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Background: Research on the effectiveness of pharmacist-led antimicrobial stewardship programmes (ASPs) in the urology department is limited., Aim: To evaluate the impact of pharmacist-led multi-faceted ASPs on antibiotic use and clinical outcomes., Methods: A prescription review of inpatients receiving one or more antibiotics in the urology department of a large teaching hospital in Guangzhou, China, was conducted from April 2019 to March 2023. The pharmacist-led multi-faceted ASP intervention included guideline development, training, medication consultation, review of medical orders, indicator monitoring, and consultation. The primary outcome was antibiotic consumption. The data were analysed using interrupted time-series (ITS) analysis., Findings: Following the implementation of ASPs, an immediate decrease was observed in total antibiotic consumption, antibiotic use rate, second-generation cephalosporins, third-generation cephalosporins, fluoroquinolones, and WHO Watch category antibiotics. No differences were observed in mortality rate before and after the intervention, and no significant short- or long-term effects were found on length of hospital stay (LOS) using ITS. However, there was a significant short-term effect on average antibiotic cost., Conclusion: The implementation of pharmacist-led multi-faceted ASPs had positive impacts on reducing antimicrobial consumption without increasing LOS, antibiotic cost, or mortality rate., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objectives: The COVID-19 pandemic has posed a significant threat to the global healthcare system, presenting a major challenge to antimicrobial stewardship worldwide. This study aimed to provide a comprehensive and up-to-date picture of global antimicrobial resistance (AMR) and antibiotic use in COVID-19 patients., Methods: We conducted a systematic review to determine the prevalence of AMR and antibiotic usage among COVID-19 patients receiving treatment in healthcare facilities. Our search encompassed the PubMed, Web of Science, Embase, and Scopus databases, spanning studies published from December 2019 to May 2023. We utilized random-effects meta-analysis to assess the prevalence of multidrug-resistant organisms (MDROs) and antibiotic use in COVID-19 patients, aligning with both the WHO's priority list of MDROs and the AWaRe list of antibiotic products. Estimates were stratified by region, country, and country income. Meta-regression models were established to identify predictors of MDRO prevalence and antibiotic use in COVID-19 patients. The study protocol was registered with PROSPERO (CRD 42023449396)., Results: Among the 11,050 studies screened, 173 were included in the review, encompassing a total of 892,312 COVID-19 patients. MDROs were observed in 42.9% (95% CI 31.1-54.5%, I 2 = 99.90%) of COVID-19 patients: 41.0% (95% CI 35.5-46.6%) for carbapenem-resistant organisms (CRO), 19.9% (95% CI 13.4-27.2%) for methicillin-resistant Staphylococcus aureus (MRSA), 24.9% (95% CI 16.7-34.1%) for extended-spectrum beta-lactamase-producing organisms (ESBL), and 22.9% (95% CI 13.0-34.5%) for vancomycin-resistant Enterococcus species (VRE), respectively. Overall, 76.2% (95% CI 69.5-82.9%, I 2 = 99.99%) of COVID-19 patients were treated with antibiotics: 29.6% (95% CI 26.0-33.4%) with "Watch" antibiotics, 22.4% (95% CI 18.0-26.7%) with "Reserve" antibiotics, and 16.5% (95% CI 13.3-19.7%) with "Access" antibiotics. The MDRO prevalence and antibiotic use were significantly higher in low- and middle-income countries than in high-income countries, with the lowest proportion of antibiotic use (60.1% (95% CI 52.1-68.0%)) and MDRO prevalence (29.1% (95% CI 21.8-36.4%)) in North America, the highest MDRO prevalence in the Middle East and North Africa (63.9% (95% CI 46.6-81.2%)), and the highest proportion of antibiotic use in South Asia (92.7% (95% CI 90.4-95.0%)). The meta-regression identified antibiotic use and ICU admission as a significant predictor of higher prevalence of MDROs in COVID-19 patients., Conclusions: This systematic review offers a comprehensive and current assessment of MDRO prevalence and antibiotic use among COVID-19 patients in healthcare facilities. It underscores the formidable challenge facing global efforts to prevent and control AMR amidst the backdrop of the COVID-19 pandemic. These findings serve as a crucial warning to policymakers, highlighting the urgent need to enhance antimicrobial stewardship strategies to mitigate the risks associated with future pandemics., Competing Interests: Declaration of Competing Interest All authors declare no competing interests. All authors had full access to all the data in the study and had final responsibility for the decision to submit for publication., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Riparian soil is a critical area of watersheds. The characteristics of biological contaminants in riparian soil affect the pollution control of the watershed water environment. Thus, the microbial community structure, antibiotic resistance genes (ARGs), and mobile genetic elements (MGEs) in the riparian soil of the Lanzhou section of the Yellow River were investigated by analyzing the characteristics of soil samples collected from farmland, mountains, and industrial land. The results showed that the Proteobacteria, Bacteroidetes, and Actinobacteria were the dominant phyla in the riparian soil of Lanzhou section of the Yellow River. The microbial structure in the riparian soil was significantly correlated with the land use type ( P < 0.05). The α diversity index of bacterial communities in land types was in the order of farmland > mountain > industry. Sulfonamide-typed ARGs were the most dominant genes in the soil of the Lanzhou section of the Yellow River Basin, among which the sul1 gene had the highest abundance, 20-36 000 times that of other detected ARGs. Moreover, the total absolute abundance of ARGs in industrial soil was the highest. Principal coordinate analysis (PCoA) displayed that the ARGs characteristics had a significant correlation with land types ( P < 0.05), and intl1 and tnpA-04 drove the diffuseness of sulfonamide and tetracycline ARGs, respectively. Redundancy analysis (RDA) demonstrated that the content of inorganic salt ions and total phosphorus in the soil of the riparian zone of the Yellow River Lanzhou section were the main environmental factors, modifying the distribution of the microbial structure. Halobacterota and Acidobacteriota were the main microflora that drove the structural change in ARGs.

River is a unique source of drinking water in valley-type cities, affecting local urban development and human lifestyles. However, the key driving factors for dissemination of antibiotic-resistant genes (ARGs) in valley-type urban environments remain unclear. This study aimed to investigate the distribution of ARGs in the Yellow River and to clarify the driving factors of ARGs in a typical valley basin city (Lanzhou, China). The seven selected ARGs with higher abundances including tetracycline resistance genes (tetM, tetX), macrolide resistance genes (ermB, ermF, ereA), and sulfonamide resistance genes (sul1, sul2) were detected. The results showed that the total absolute abundance of all the selected ARGs varied from 9.97 × 10 12 to 1.04 × 10 15 copies/L in the water body, with higher abundances in the wet season, relative to the dry season. Among these, sulfonamide resistance genes (sul1, sul2) displayed the highest absolute abundance in the river and soil. The ARGs and mobile genetic elements (MGEs) were significantly correlated with bacterial abundance, dissolved organic carbon (DOC), ammonia nitrogen (NH 4 + ), and total nitrogen (TN) levels in the water environment (Mantel test, P < 0.01). Structural equation modeling revealed the direct input of point-source and nonpoint-source ARGs in this area contributed less to the overall level of the ARGs in the water. Among the multiple drivers, the MGEs derived from wastewater treatment plant and anthropogenic nonpoint area positively and directly affected the ARG profiles in water (P < 0.01), rather than the factors of bacterial abundance and physicochemical properties. According to this study, the exogenous MGEs from anthropogenic activities are the main driver for the enrichment of ARGs in the valley-type urban river environment., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Importance: Plasmid size is one of the factors affecting transfection efficacy in most of the molecular genetic research studies. One effective approach for reducing plasmid size is to replace relatively large, conventional antibiotic resistance genes with the short-size dfrB10 gene. The successful construct of a series of dfrB10- based tool plasmids and their functional validation, via comparison with original plasmids, suggest that dfrB10 is a potent drug resistance selection marker. The antibiotic trimethoprim offers convenient usage comparable to that of ampicillin or kanamycin. Additionally, fluorescence analysis has demonstrated the compatibility of TMP with protein expression in various host cells. Based on these findings, TMP- dfrB10 could be an alternative choice for future use in molecular genetic research studies that require miniature plasmids to achieve optimal results., Competing Interests: The authors declare no conflict of interest.

Poplar waste is acted as feedstock to produce renewable biofuel and green chemical by catalytic pyrolysis using ferric nitrate and zinc chloride as additive. The additive contributes to the generation of furfural in bio-oil. Additive promotes the generation of H 2 and inhibits the generation of CO with bio-gas heating value of 12.16 MJ (Nm 3 ) -1 . Biochar exists ZnO and Fe 3 O 4 with large surface area, which could be used as absorbent and photocatalyst for tetracycline and ciprofloxacin removal. The tetracycline and ciprofloxacin adsorption amount of biochar are 316.41 and 255.23 mg g -1 respectively. While the photocatalytic degradation removal of the tetracycline and ciprofloxacin is close to 100%. The adsorption and photocatalytic degradation mechanism are investigate and analyzed using the density functional theory and electron paramagnetic resonance analysis. Biochar can be quickly recycled and regenerated after use. Besides, biochar can be used in lithium ion battery industry for energy storage, which specific capacity is 535 mAh g -1 ., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Milbemycins (MILs), a group of 16-membered insecticidal macrocylic lactones, are widely used as the biological pesticide and the precursors of semi-synthetic veterinary drugs. Polyketide synthases (PKSs), which require phosphopantetheinyl transferases (PPTases) to activate their ACP domains from apo forms to holo forms, catalyze the backbone biosynthesis of MILs. Here we found there was a complex phosphopantetheinylation network mediated by five putative PPTases in Streptomyces bingchenggensis. Repression mutants of PpA27 and PpA62 via CRISPRi both produced significantly lower yields of MILs than that of the control strain. Repression mutant of PpA68 led to abolishment of the pigment production. MILs production was significantly enhanced by PpA27 overexpression, while not by the overexpression of other PPTases. PpA27 was thus proved a dedicated post-translational enzyme to activate PKSs involved in the MILs biosynthesis. MILs titer was further enhanced by co-overexpression of PpA27 and MilR, the pathway‑specific transcriptional activator of MIL biosynthetic gene cluster. When PpA27 and MilR were co-overexpressed in the industrial S. bingchenggensis HMB, MILs production was increased by 40.5%. These results indicated that tuning the antibiotic biosynthetic pathway by co-engineering transcriptional regulation network and post-translational phosphopantetheinylation network is an effective strategy for antibiotic production improvement., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Antimicrobial resistance (AMR) and the possible consequences of rising ambient temperatures brought on by global warming have been extensively discussed. However, the epidemiological evidence on the effects of temperature on AMR is rare and little is known about the role of socioeconomic inequities. This ecological study obtained 31 provinces AMR data of Escherichia Coli (E. coli) from the China Antimicrobial Resistance Surveillance System (CARSS) over the period from 2014 to 2020, which were linked to the meteorological and socioeconomic data published in the China Statistical Yearbook. Modified difference-in-differences (DID) analyses were performed to estimate the effect of ambient temperature on AMR of E. coli to third-generation cephalosporins (ceftriaxone and cefotaxime), carbapenems, and quinolones, adjusting for variations in meteorological and socioeconomic factors. We estimated that every 1 °C increase in average ambient temperature was associated with 2.71 % (95 % confidence interval [CI]: 1.20-4.24), 32.92 % (95 % CI: 15.62-52.81), and 1.81 % (95 % CI: 0.47-3.16) increase in the prevalence of E. coli resistance to third-generation cephalosporins (ceftriaxone and cefotaxime), carbapenems and quinolones, respectively. The link was more profound in the regions with lower temperature and a median level of average humidity, and the regions with lower income, lower expenditure (in economics), lower health resources, and lower hospital admissions. Neither the replacement of the temperature variable nor the alternative approaches for confounding adjustment changed the positive association between ambient temperature and AMR. In general, there exists a positive association between ambient temperature and AMR, although the strength of such an association varies by socioeconomic and health services factors. The association is possibly nonlinear, especially for E. coli resistance to third-generation cephalosporins. The findings suggest that AMR control programs should explicitly incorporate weather patterns to increase their effectiveness., Competing Interests: Declaration of competing interest All authors declare no competing interests., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The role of earthworms in reducing the antibiotic resistance genes (ARGs) in sludge vermicompost remains unclear. The structure of extracellular polymeric substance (EPS) of sludge may be associated with the horizontal gene transfer behavior of ARGs in the vermicomposting of sludge. Therefore, this study aimed to investigate the effects of earthworms on the structural characteristics of EPS associated with the fate of ARGs in EPS during the vermicomposting of sludge. The results showed vermicomposting could diminish the abundance of ARGs and mobile genetic elements (MGEs) in the EPS of sludge by 47.93 % and 7.75 %, compared to the control, respectively. Relative to the control, vermicomposting also led to the reduction of MGEs abundances in the soluble EPS of 40.04 %, lightly bound EPS of 43.53 %, and tightly bound EPS of 70.49 %, respectively. The total abundances of certain ARGs dramatically diminished 95.37 % in tightly bound EPS of sludge during vermicomposting. In vermicomposting, the main influencing factor of ARGs distribution was the proteins in LB-EPS, accounting for 48.5 % of the variation. This study suggests that the earthworms lower the total abundances of ARGs by regulating the microbial community and modifying the microbial metabolic pathways associated with ARGs and MGEs in the EPS of sludge., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Introduction: Antimicrobial resistance (AMR) of Klebsiella pneumoniae ( K. pneumoniae ) poses a significant global public health threat and is responsible for a high prevalence of infections and mortality. However, knowledge about how ambient temperature influences the AMR of K. pneumoniae is limited in the context of global warming., Methods: AMR data of 31 Chinese provinces was collected from the China Antimicrobial Resistance Surveillance System (CARSS) between 2014 and 2020. Socioeconomic and meteorological data were collected from the China Statistical Yearbook during the same period. A modified difference-in-differences (DID) approach was applied to estimate the association between ambient temperature and third-generation cephalosporin-resistant K. pneumoniae (3GCRKP) and carbapenem-resistant K. pneumoniae (CRKP). Furthermore, moderating effects of socioeconomic factors were also evaluated., Results: Every 1°C increase in annual average temperature was associated with a 4.7% (relative risk (RR):1.047, 95% confidence intervals (CI): 1.031-1.082) increase in the detection rate of 3GCRKP, and a 10.7% (RR:1.107, 95% CI: 1.011-1.211) increase in the detection rate of CRKP. The relationships between ambient temperature and 3GCRKP and CRKP were found to be moderated by socioeconomic status (GDP per capita , income per capita , and consumption per capita ; the interaction p -values <0.05), where higher economic status was found to strengthen the effects of temperature on the detection rate of 3GCRKP and weaken the effects on the detection rate of CRKP., Discussion: Ambient temperature was found to be positively associated with AMR of K. pneumoniae , and this association was moderated by socioeconomic status. Policymakers should consider the impact of global warming and high temperatures on the spread of 3GCRKP and CRKP when developing strategies for the containment of AMR., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Zeng, Li, Zhao, Li, Liu, Shi, Yang, Xia, Yang and Yang.)

A carbapenem-resistant Citrobacter sedlakii strain AA2CS carrying bla NDM-5 was detected in outdoor aerosols of a wastewater treatment plant (WWTP) in China and the whole genome was sequenced subsequently. AA2CS was captured in an aerobic tank with aerosol particles of sizes ranging from 4.7 to 7.0 μm. Besides bla NDM-5 , AA2CS also harbored 21 other antibiotic resistance genes and displayed a high level of resistance to ampicillin, cefotaxime, ceftazidime, tetracycline, and meropenem. Bla NDM-5 was located on the IncX3 plasmid (pCSNDM-5) with an IS 3000 -IS5- bla NDM-5 - ble MBL - trpF - dsbD -IS 26 structure. pCSNDM-5 was highly homologous to other bla NDM-5 -carrying IncX3 plasmids in China and can be transferred to the Escherichia coli recipient J53. To our knowledge, this is the first report of carbapenem-resistant Enterobacteriaceae in outdoor aerosols in WWTPs.

Background: The C-3',4'-dideoxygenation structure in gentamicin can prevent deactivation by aminoglycoside 3'-phosphotransferase (APH(3')) in drug-resistant pathogens. However, the enzyme catalyzing the dideoxygenation step in the gentamicin biosynthesis pathway remains unknown., Results: Here, we report that GenP catalyzes 3' phosphorylation of the gentamicin biosynthesis intermediates JI-20A, JI-20Ba, and JI-20B. We further demonstrate that the pyridoxal-5'-phosphate (PLP)-dependent enzyme GenB3 uses these phosphorylated substrates to form 3',4'-dideoxy-4',5'-ene-6'-oxo products. The following C-6'-transamination and the GenB4-catalyzed reduction of 4',5'-olefin lead to the formation of gentamicin C. To the best of our knowledge, GenB3 is the first PLP-dependent enzyme catalyzing dideoxygenation in aminoglycoside biosynthesis., Conclusions: This discovery solves a long-standing puzzle in gentamicin biosynthesis and enriches our knowledge of the chemistry of PLP-dependent enzymes. Interestingly, these results demonstrate that to evade APH(3') deactivation by pathogens, the gentamicin producers evolved a smart strategy, which utilized their own APH(3') to activate hydroxyls as leaving groups for the 3',4'-dideoxygenation in gentamicin biosynthesis.

A novel exopolysaccharide (EPS) with high molecular weight (3.65 × 10 5  Da) and film-forming ability was produced by the strain Kosakonia sp. CCTCC M2018092. Partially acid hydrolyzed EPS (AH-EPS) with high content of fucose was prepared and exhaustively characterized. The molecular weight of AH-EPS was determined to be 3.47 × 10 4  Da. GC-MS and HPLC analyses indicated that AH-EPS is composed of L-fucose, d-glucose, D-galactose, D-glucuronic acid and pyruvic acid in the molar ratio of 2.03:1.00:1.18:0.64:0.67. Chemical and NMR analyses revealed that AH-EPS is an anionic heteropolysaccharide, with a major linkage structural motif as follows. Utilizing AH-EPS as reducing and stabilizing agent, silver nanoparticles (AH-EPS@Ag NPs) with uniform size (diameter about 20 nm) were synthesized through a green method. A hybrid film containing EPS and AH-EPS@Ag NPs was further prepared, and its antibacterial effectiveness to Staphylococcus aureus was confirmed. Taken together, this work revealed the structural characteristics of a novel fucose-rich polysaccharide, with good potential in developing new biodegradable antibacterial film., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In order to obtain a novel multifunctional wound dressing with good water vapor permeability and long-lasting antibacterial properties, a skin-like thermoplastic polyurethane (TPU) bilayer membrane containing self-made polyhexamethylene guanidine hydrochloride (PHMG) grafted graphene oxide (MGO) was prepared by non-solvent phase separation and particle filtration. The antibacterial properties and wound-healing ability of TPU, GO-TPU, MGO-TPU composite porous membrane are systematically compared. The results show that with the incorporation of MGO, the porous MGO-TPU membrane exhibits good biocompatibility, excellent water vapor transmission properties, and long-lasting broad-spectrum antibacterial properties (the antibacterial property remains unchanged for 30 days under continuously shaking and washing). The wound healing results for mouse model show that MGO-TPU could significantly accelerate the healing rate of wounds as it provides a sterile environment and also promotes the formation of re-epithelialization during wound healing., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Background: New semi-synthetic aminoglycoside antibiotics generally use chemical modifications to avoid inactivity from pathogens. One of the most used modifications is 3',4'-di-deoxygenation, which imitates the structure of gentamicin. However, the mechanism of di-deoxygenation has not been clearly elucidated., Results: Here, we report that the bifunctional enzyme, GenB4, catalyzes the last step of gentamicin 3',4'-di-deoxygenation via reduction and transamination activities. Following disruption of genB4 in wild-type M. echinospora, its products accumulated in 6'-deamino-6'-oxoverdamicin (1), verdamicin C2a (2), and its epimer, verdamicin C2 (3). Following disruption of genB4 in M. echinospora ΔgenK, its products accumulated in sisomicin (4) and 6'-N-methylsisomicin (5, G-52). Following in vitro catalytic reactions, GenB4 transformed sisomicin (4) to gentamicin C1a (9) and transformed verdamicin C2a (2) and its epimer, verdamicin C2 (3), to gentamicin C2a (11) and gentamicin C2 (12), respectively., Conclusion: This finding indicated that in addition to its transamination activity, GenB4 exhibits specific 4',5' double-bond reducing activity and is responsible for the last step of gentamicin 3',4'-di-deoxygenation. Taken together, we propose three new intermediates that may refine and supplement the specific biosynthetic pathway of gentamicin C components and lay the foundation for the complete elucidation of di-deoxygenation mechanisms.

Rapid absorption of wound exudate and prevention of wound infection are prerequisites for wound dressing to accelerate wound healing. In this study, a novel kind of promising wound dressing is developed by incorporating polyhexamethylene guanidine (PHMG)-modified graphene oxide (mGO) into the poly(vinyl alcohol)/chitosan (PVA/CS) matrix, conferring the dressing the required mechanical properties, higher water vapor transmission rate (WVTR), less swelling time, improved antibacterial activity, and more cell proliferation compared to the PVA/CS film crosslinked by genipin. In vivo experiments indicate that the PVA/CS/mGO composite film can accelerate wound healing via enhancement of the re-epithelialization. PVA/CS/mGO composite film with 0.5 wt% mGO sheets displays the best wound healing properties, as manifested by the 50% higher antibacterial rate compared to GO and the wound healing rate of the mouse using this dressing is about 41% faster than the control group and 31% faster than the pure PVA/CS dressing. The underlying mechanism of the accelerated wound healing properties may be a result of the improved antibacterial ability to eradicate pathogenic bacteria on the wound area and maintain an appropriate moist aseptic wound healing environment to accelerate re-epithelialization. These findings suggest that this novel composite PVA/CS/mGO film may have promising applications in wound dressing., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The aim of this study was to characterize rpoC gene mutations in Mycobacterium tuberculosis (MTB) and investigate the factors associated with rpoC mutations and the relation between rpoC mutations and tuberculosis (TB) transmission. A total of 245 MTB clinical isolates from patients with TB in six provinces and two municipalities in China were characterized based on gene mutations through DNA sequencing of rpoC and rpoB genes, phenotyping via standard drug susceptibility testing, and genotypic profiling by mycobacterial interspersed repetitive unit-variable number tandem repeat (MIRU-VNTR) typing. Approximately 36.4% of the rifampin-resistant isolates harbored nonsynonymous mutations in the rpoC gene. Twenty-nine nonsynonymous single mutations and three double mutations were identified. The rpoC mutations at locus 483 (11.3%) were predominant, and the mutations at V483G, W484G, I491V, L516P, L566R, N698K, and A788E accounted for 54.5% of the total detected mutations. Fifteen new mutations in the rpoC gene were identified. Rifampin resistance and rpoB mutations at locus 531 were significantly associated with rpoC mutations. MIRU-VNTR genotype results indicated that 18.4% of the studied isolates were clustered, and the rpoC mutations were not significantly associated with MIRU-VNTR clusters. A large proportion of rpoC mutation was observed in the rifampicin-resistant MTB isolates. However, the findings of this study do not support the association of rpoC mutation with compensated transmissibility.

Streptomyces is famous for its capability to produce the most abundant antibiotics in all kingdoms. All Streptomyces antibiotics are natural products, whose biosynthesis from the so-called gene clusters are elaborately regulated by pyramidal transcriptional regulatory cascades. In the past decades, scientists have striven to unveil the regulatory mechanisms involved in antibiotic production in Streptomyces. Here we mainly focus on three aspects of the regulation on antibiotic production. 1. The onset of antibiotic production triggered by hormones and their coupled receptors as regulators; 2. The cascades of global and pathway-specific regulators governing antibiotic production; 3. The feedback regulation of antibiotics and/or intermediates on the gene cluster expression for their coordinated production. This review will summarize how the antibiotic production is stringently regulated in Streptomyces based on the signaling, and lay a theoretical foundation for improvement of antibiotic production and potentially drug discovery.

The increase in severe infections caused by antibiotic drug resistance and the decrease in the number of new antibacterial drugs approved for use in the last few decades are driving the need for the development of new antimicrobial strategies. Antimicrobial peptides (AMPs) are a potential new class of antimicrobial drugs that are expected to solve the problem of global antibiotic drug resistance. Herein, the AMP Tet213 was immobilised onto the substrates of alginate (ALG), hyaluronic acid (HA), and collagen (COL) to form the ALG/HA/COL-AMP wound dressing. This wound dressing exhibited a high degree of swelling and the appropriate porosity, mechanical properties, and biodegradability. The Tet213-immobilised ALG/HA/COL dressings exhibited antimicrobial activity against three pathogenic bacterial strains (Gram-negative E. coli and Gram-positive MRSA and S. aureus) and facilitated the proliferation of NIH 3T3 fibroblast cells. In addition, the ALG/HA/COL-AMP antimicrobial dressings promoted wound healing, re-epithelialisation, collagen deposition, and angiogenesis. Moreover, the wound-healing effects of ALG/HA/COL-AMP surpassed the gauze and ALG/HA/COL compared to commercially available silver-based dressings (Aguacel Ag). These results suggest that the Tet213-conjugated ALG/HA/COL wound dressing, with its multiple biological activities, is a promising wound-dressing material., (Copyright © 2019. Published by Elsevier B.V.)

Vermicomposting is a green technology used in the recycling of sewage sludge using the joint action of earthworms and microorganisms. Although tetracycline is present in abundance in sewage sludge, little attention has been given to its influence on vermicomposts. This study investigated the effects of different tetracycline concentrations (0, 100, 500 and 1000 mg/kg) on the decomposition of organic matter, microbial community and antibiotic resistance genes (ARGs) during vermicomposting of spiked sludge. The results showed that 100 mg/kg tetracycline could stimulate earthworms' growth, accompanied by the highest humification and decomposition rates of organic matter in the sludge. The abundance of active microbial cells and diversity decreased with the increase in tetracycline concentrations. The member of Bacteroidetes dominated in the tetracycline spiked treatments, especially in the higher concentration treatments. Compared to its counterparts, the addition of tetracycline significantly increased the abundances of ARGs (tetC, tetM, tetX, tetG and tetW) and Class 1 integron (int-1) by 4.7-186.9 folds and 4.25 folds, respectively. The genera of Bacillus and Mycobacterium were the possible bacterial pathogen hosts of ARGs enriched in tetracycline added group. This study suggests that higher concentration of tetracycline residual can modify microbial communities and increase the dissemination risk of ARGs for final sludge vermicompost., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The high content of tetracycline in municipal sludge may result in vermicomposting products carrying a high abundance of antibiotic resistance genes, thus lowering the utilization value of the vermicompost. Hence, this study aimed to reveal the underlying effects of tetracycline concentrations on the resistance genes involved in vermicomposting systems for sludge recycling. For this purpose, fresh sludge substrates with different concentrations of tetracycline (100, 500, and 1000 mg·kg -1 ) were vermicomposted for 60 days using Eisenia foetida . In parallel, sludge treatment without the addition of the tetracycline was used as a control. During the experiment, changes in bacterial communities, tetracycline resistance genes ( tetC , tetG , tetM , tetW , and tetX ), and class 1 integron ( intI1 ) were detected using high-throughput sequencing and qualitative PCR, respectively. The results showed that the addition of tetracycline reduced the abundance of Proteobacteria but increased the abundance of Bacteroidetes in the sludge vermicompost. Furthermore, the concentrations of tetracycline had a significant negative correlation with Shannon and Pielou indexes of bacterial diversity. In addition, tetracycline increased intI1 genes and tetracycline resistance genes in the sludge by 4.25 times and 4.7-186.9 times, respectively. Moreover, there was a significantly positive correlation between the abundance of tetM genes and tetracycline concentration. This study suggests that higher concentration of tetracycline in sludge can modify the microbial community structure of vermicompost, enhancing the abundance of antibiotic resistance genes and their associated dissemination risks.

The dissemination and propagation of antibiotic resistance genes (ARGs) is an emerging global health concern, and the potential effects of nanomaterials on ARGs fates have drawn much attention recently. In the current study, the effects of metallic nanoparticles on ARGs occurrence of leachate culturable microbiota were investigated by four typical metal and metal oxide nanoparticles (Cu, Zn, CuO, and ZnO). The ARGs diversity was remarkably decreased during the cultivation and enrichment of leachate microbiota, and their abundances decreased for 1.4-3.2 orders of magnitude. The presence of nanoparticles facilitated the ARGs attenuation, and the magnitude of effects depended on types of nanoparticles and ARGs. Metal oxide nanoparticles caused more remarkable effects than metal nanoparticles. Mechanism analysis indicated that bacterial growth was inhibited, and the dissolved metal ions from nanoparticles partially contributed to nanoparticles decreasing ARGs. Flow cytometry experiments further confirmed that nanoparticles could enter bacterial cells, and then induce excessive reactive oxygen species (ROS) generation and increase membrane permeability. Finally, the possible mechanisms were put forward, and the structural equation models (SEM) differentiated the contribution of different factors shaping ARGs. The dissolved metal ions and growth inhibition caused by nanoparticles decreased ARGs transfer frequencies via exerting excessive metal stress and lowering population density. On the other hand, nanoparticles were incorporated into the cells, and then induced the generation of ROS, which might facilitate ARGs horizontal transfer via increasing membrane permeability, or decrease ARGs via the damage of genomic and plasmid DNA. Therefore, nanoparticles could affect ARGs fates via several ways, and combined effects finally determined the ARGs variations., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objective: The aim of the present work was to use a semi-mechanistic pharmacokinetic-pharmacodynamic (PK/PD) model developed from in vitro time-kill measurements with P. aeruginosa to compare different pharmacodynamic indices derived from simulated human avibactam exposures, with respect to their degree of correlation with the modelled bacterial responses., Methods: A mathematical model of the effect of ceftazidime-avibactam on the growth dynamics of P. aeruginosa was used to simulate bacterial responses to modelled human exposures from fractionated avibactam dosing regimens with a fixed ceftazidime dosing regimen (2 or 8 g q8h as a 2-h infusion). The relatedness of the 24-h change in bacterial density and avibactam exposure parameters was evaluated to determine exposure parameter that closely correlated with bacterial growth/killing responses., Results: Frequent dosing was associated with higher efficacy, resulting in a reduction of avibactam daily dose. The best-fit PD index of avibactam determined from the simulation was fT > C T of 1 mg/L avibactam and q8h was the longest dosing interval able to achieve 2-log kill: 41-87% (3.3 h to 7.0 h out of 8-h interval, respectively). The avibactam exposure magnitude required to achieve a 2-log kill in the simulations was dependent on the susceptibility of the bacterial isolate to ceftazidime., Conclusions: Avibactam activity in combination with ceftazidime against multidrug resistant P. aeruginosa correlated with fT > C T . Setting a threshold avibactam concentration to 1 mg/L, superimposed over a simulated human-like exposure of ceftazidime, achieved at least 2-log kill for the clinical dose of 500 mg q8h avibactam as a 2-h infusion, depending on the minimum inhibitory concentration of ceftazidime alone., (Copyright © 2018 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Dewatered sludge often contains abundant antibiotics, and such contaminants can potentially affect the nitrogen fertilizer value of sludge-derived vermicompost. For this purpose, the aims of this study were to investigate the effects of different tetracycline concentrations in sludge on the nitrification rate and abundance and community characteristics of ammonia oxidizers during vermicomposting. Four sludge treatments with different concentrations of tetracycline (0, 100, 500, and 1000 mg·kg -1 ) were used, and data were collected to reveal the mechanism regarding the ammonia oxidization of sludge in the vermicomposting system. The results showed that the high concentration of tetracycline (1000 mg·kg -1 ) significantly inhibited the nitrification rate of vermicomposting ( P <0.05), but no significant effect was observed in the low concentration treatments. Compared with ammonia-oxidizing bacteria (AOB), ammonia oxidizing archaea (AOA) were detected as the dominant microorganisms involved in the ammonia oxidation process during vermicomposting. In addition, the abundances of amoA genes were significantly elevated ( P <0.05) in the treatments with 100 mg·kg -1 tetracycline, but values significantly decreased with the further increments of tetracycline concentrations ( P <0.05). The results obtained from high-throughput sequencing revealed that the community diversity and structure of AOA and AOB were strongly modified by tetracycline concentrations, and a negative correlation relationship was detected between the tetracycline concentrations and the α diversity of AOA.

Antibiotics existed in dewatered sludge may affect the organic decomposition and nitrification efficiency of vermicomposting process, and thus lowering the agricultural value of sludge vermicompost. However, few studies have focused on the effects of antibiotics during vermicomposting process of sludge, notably for the maturated phage. Hence, this study aimed to investigate the effects of antibiotics on the nitrification rate and the features of ammonia oxidizing archaea (AOA) and bacteria (AOB) during vermicomposting maturated phage of sludge. The treatments including the additions of tetracycline and ofloxacin with high and low concentrations were compared with the control without adding antibiotics. The results showed the antibiotics enhanced the nitrification rate of 15.8%-42% in vermicomposting maturated phage compared with the counterpart, with a better stimulating effect in the low concentration of tetracycline. The population of amoA genes increased in antibiotic treatments with low concentrations but decreased in these with high concentrations. In addition, high through-put sequencing results revealed that the tetracycline had a stronger influence on the α and β diversities of AOA and AOB, relative to the ofloxacin. In contrast to the AOB, the AOA played a more important role in ammonia oxidization, in the presence of antibiotics. This study suggests that the antibiotics of dewatered sludge can strongly affect the ammonia oxidization process through modifying the numbers and community structures of AOA and AOB during vermicomposting and these effects are associated with the types and concentrations of antibiotics., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Azalomycin F 5a was a polyhydroxy macrolide produced by streptomycete strains. Our preliminary researches indicated that it could kill methicillin-resistant Staphylococcus aureus (MRSA) likely by increasing the permeability of cell membrane, and that cell-membrane phospholipids were likely important targets. To confirm this, membrane permeability assay was performed and visualized by fluorescence staining, and then the detailed interactions between azalomycin F 5a and model membranes prepared with 1,2-dihexadecanoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DPPG) were determined using attenuated total reflectance fourier transform infrared spectroscopy and 31 P nuclear magnetic resonance techniques. The results indicated that there were strong interactions between azalomycin F 5a and model membranes, especially between azalomycin F 5a and the polar head of phospholipid. For further evidence and details, the molecular dynamics (MD) simulation of the interactions between azalomycin F 5a and DPPG or lysyl-DPPG were performed using Amber16 software package. A strong interaction between the lactone ring of azalomycin F 5a and the polar head of DPPG or lysyl-DPPG had been clearly observed. Moreover, a larger distribution probability out of phospholipid bilayer had been discovered for the guanidyl side chain of azalomycin F 5a , especially when probable anion molecules anchoring on the cytoplasmic membrane occurred. Therefore, lipoteichoic acid (LTA), a vital component of gram-positive bacterial envelope, was investigated for its probable interactions with azalomycin F 5a using broth microdilution method. The results showed that azalomycin F 5a -induced MRSA lysis could be prevented by LTA. This deduced that there were some interactions between azalomycin F 5a , more likely its guanidyl side chain, and LTA. Thereby, azalomycin F 5a increasing the cell-membrane permeability of MRSA had likely achieved by the synergy of its lactone ring binding to the polar head of phospholipid and its guanidyl side chain targeting to LTA, and which had eventually led to the autolysis of MRSA cells., (Copyright © 2018 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Zero-dimensional carbon dots (CD) and their effects on osteogenesis have been rarely studied in bone repair scaffolds. Here, we fabricate a novel CD doped chitosan/nanohydroxyapatite (CS/nHA/CD) scaffold with full potential to promote bone regeneration by a facile freeze-drying method. The CS/nHA/CD scaffolds enhanced cell adhesion and osteoinductivity in rat bone mesenchymal stem cells by up-regulating genes involved in focal adhesion and osteogenesis in vitro, which significantly improved the formation of vascularized new bone tissue at 4 weeks compared to pure CS/nHA scaffolds in vivo. Inspired by the excellent photothermal effect of CD, the scaffolds were applied in tumor photothermal therapy (PTT) under near-infrared (NIR) irradiation (808 nm, 1 W/cm 2 ). The scaffolds significantly inhibited osteosarcoma cell proliferation in vitro and effectively suppressed tumor growth in vivo. Moreover, the CS/nHA/CD scaffolds possessed distinct antibacterial properties toward clinically collected S. aureus and E. coli, and their antibacterial activity was further enhanced under NIR irradiation. This work demonstrates that zero-dimensional CD can enhance the osteogenesis-inducing property of bone repair scaffolds and that CD doped scaffolds have potential for use in PTT for tumors and infections.

Objectives: To characterize quantitatively the effect of avibactam in potentiating ceftazidime against MDR Pseudomonas aeruginosa by developing a mathematical model to describe the bacterial response to constant concentration time-kill information and validating it using both constant and time-varying concentration-effect data from in vitro and in vivo infection systems., Methods: The time course of the bacterial population dynamics in the presence of static concentrations of ceftazidime and avibactam was modelled using a two-state pharmacokinetic/pharmacodynamic (PK/PD) model, consisting of active and resting states, to account for bactericidal activities, bacteria-mediated ceftazidime degradation and inhibition of degradation by avibactam. Ceftazidime's effect on the bacterial population was described as an enhancement of the death rate of the active population, with the effect of avibactam being to increase ceftazidime potency. Model validation was performed by comparing simulated time courses of bacterial responses with those from in vitro and in vivo experimental exposures of ceftazidime and avibactam that represented those predicted in an average patient dosed with 2 g/0.5 g ceftazidime/avibactam administered every 8 h as 2 h infusions., Results: The two-state model successfully described the bacterial population dynamics, ceftazidime degradation and its inhibition by avibactam. For external validation, the model correctly predicted the bacterial response of P. aeruginosa isolates evaluated in in vitro hollow-fibre and in vivo neutropenic mouse thigh and lung infection models., Conclusions: The PK/PD model and modelled strains successfully replicated the spread in activity when compared with a large selection of P. aeruginosa strains reported in the literature.

Small colony variants (SCVs) are a commonly observed subpopulation of bacteria that have a small colony size and distinctive biochemical characteristics. SCVs are more resistant than the wild type to some antibiotics and usually cause persistent infections in the clinic. SCV studies have been very active during the past 2 decades, especially Staphylococcus aureus SCVs. However, fewer studies on Escherichia coli SCVs exist, so we studied an E. coli SCV during an experiment involving the deletion of the yigP locus. PCR and DNA sequencing revealed that the SCV was attributable to a defect in the yigP function. Furthermore, we investigated the antibiotic resistance profile of the E. coli SCV and it showed increased erythromycin, kanamycin, and d-cycloserine resistance, but collateral sensitivity to ampicillin, polymyxin, chloramphenicol, tetracycline, rifampin, and nalidixic acid. We tried to determine the association between yigP and the pleiotropic antibiotic resistance of the SCV by analyzing biofilm formation, cellular morphology, and coenzyme Q (Q 8 ) production. Our results indicated that impaired Q 8 biosynthesis was the primary factor that contributed to the increased resistance and collateral sensitivity of the SCV. This study offers a novel genetic basis for E. coli SCVs and an insight into the development of alternative antimicrobial strategies for clinical therapy.

Objective: To evaluate the performance of the Sensitire MYCOTB MIC Plate (MYCOTB) which could measure the twelve anti-tuberculosis drugs susceptibility on one 96-wells plate., Methods: A total of 140 MDR-TB strains and 60 non-MDR strains were sub-cultured and 193 strains were finally tested for drug resistance using MYCOTB and agar proportion method (APM) and another 7 strains failed of subculture. The drugs included ofloxacin (Ofx), moxifloxacin (Mfx), rifampin (RFP), amikacin (Am), rifabutin (Rfb), para-aminosalicylic acid (PAS), ethionamide (Eth), isoniazid (INH), kanamycin (Km), ethambutol (EMB), streptomycin (Sm), and cycloserine(Cs). The categorical agreement, conditional agreement, sensitivity and specificity of MYCOTB were assessed in comparison with APM. For strains with inconsistent results between MYCOTB and APM, the drug resistance related gene fragments were amplified and sequenced: gyrA for Ofx and Mfx; rpoB for RFP and Rfb; embB for EMB; rpsl for Sm; katG and the promoter region of inhA for INH, ethA and the promoter region of inhA for Eth. The sequence results were compared with results of MYCOTB and APM to analyze the consistency between sequence results and MYCOTB or APM., Results: The categorical agreement between two methods for each drug ranged from 88.6% to 100%. It was the lowest for INH (88.6%). The sensitivity and specificity of MYCOTB ranged from 71.4% to 100% and 84.3% to 100%, respectively. The sensitivity was lowest for Cs(71.4%), EMB at 10μg/ml (80.0%) and INH at 10.0μg/ml (84.6%). The specificity was lowest for Rfb (84.3%). Overall discordance between the two phenotypic methods was observed for 96 strains, of which 63 (65.6%) were found susceptible with APM and resistant with MYCOTB and the remaining 33(34.4%) strains were resistant by APM and susceptible with MYCOTB. 34/52 (65.4%) sequenced APM susceptible and MYCOTB resistant(APM-S/MYCOTB-R) strains had mutations or insertions in the amplified regions. 20/30 (66.7%) sequenced APM resistant and MYCOTB susceptible strains had mutations in the sequenced genes. MICs of twenty-nine of these thirty isolates were equal to or within 1 doubling dilution of the critical concentration., Conclusion: MYCOTB had good performance for most of tested drugs and could be used as an alternative to the more labor demanding and longer turnaround time solid culture based DST method for detection of drug susceptibility in China., Competing Interests: The authors have declared that no competing interests exist.

Sheath blight, causes by Rhizoctonia spp., threaten maize yield every year throughout the world. Trichoderma could degrade Rhizoctonia solani on maize mainly via competition and hyperparasitism, whereas validamycin A could efficiently inhibit the growth of R. solani via disturbing the energy system. By contrast, validamycin A is efficient but it takes effect in a short period, while Trichoderma takes effect in a long period though time-consuming. To overcome the disadvantages, Trichoderma asperellum GDFS1009 was used together with validamycin A. In vitro tests proved that the combined pathogen-inhibiting efficiency was significantly improved. Furthermore, results based on transcriptome and metabolome showed that validamycin A had no significant effects on growth, basic metabolism and main bio-control mechanisms of T. asperellum GDFS1009. Such few impacts may be attributed to detoxification and tolerance mechanism of T. asperellum GDFS1009. In addition, T. asperellum GDFS1009 has an ability to relieve the stress caused by validaymicn A. Meanwhile, liquid chromatography-mass spectrometry (LC-MS) results showed that only minor degradation (20%) of validamycin A was caused by T. asperellum GDFS1009 during cofermentation. All results together provide solid bases for validamycin A synergy with T. asperellum GDFS1009 in their combined biocontrol application.

Implant-associated infections and non-absorbing materials are two important reasons for a second surgical procedure to remove internal fixation devices after an orthopedic internal fixation surgery. The objective of this study was to produce an antibacterial and absorbable fixation screw by adding gentamicin to silk-based materials. The antibacterial activity was assessed against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in vitro by plate cultivation and scanning electron microscopy (SEM). We also investigated the properties, such as the mechanical features, swelling properties, biocompatibility and degradation, of gentamicin-loaded silk-based screws (GSS) in vitro. The GSS showed significant bactericidal effects against S. aureus and E. coli. The antibacterial activity remained high even after 4 weeks of immersion in protease solution. In addition, the GSS maintained the remarkable mechanical properties and excellent biocompatibility of pure silk-based screws (PSS). Interestingly, after gentamicin incorporation, the degradation rate and water-absorbing capacity increased and decreased, respectively. These GSS provide both impressive material properties and antibacterial activity and have great potential for use in orthopedic implants to reduce the incidence of second surgeries.

Objectives: Gentamicin is widely used in end-stage renal disease (ESRD) patients for the treatment of infections. The goal of this study was to find the most reasonable dosing regimen for gentamicin in ESRD patients receiving haemodialysis., Methods: The in vitro antimicrobial activity of gentamicin was evaluated by static and dynamic time-kill experiments against three bacterial strains of MSSA, MRSA and Pseudomonas aeruginosa. A semi-mechanistic pharmacokinetic/pharmacodynamic (PK/PD) model was established afterwards, allowing the characterization of the antibacterial effect of gentamicin in the human body. The model was utilized to assess dosing regimens of gentamicin in ESRD patients receiving haemodialysis, taking both efficacy and safety into account., Results: The PK/PD model was capable of describing the bacterial response to gentamicin exposure in all three strains. Simulation based on the PK/PD model showed that pre-dialysis and post-dialysis dosing would bring comparable benefit to the ESRD patient regardless of whether the PK/PD target (fCmax/MIC >8-fold) was achieved, while the post-dialysis dosing resulted in a significantly lower trough concentration. The result of simulated dose fractionation demonstrated that both fCmax/MIC and fAUC(0-24)/MIC are strong predictors of drug effectiveness, but the PK/PD model would provide a more precise prediction of antibacterial activity as well as valuable information on dose selection in ESRD patients receiving haemodialysis., Conclusions: Our study supports the original FDA label with regard to the dosing regimen of gentamicin in ESRD patients, which offers adequate clinical benefit as well as an acceptable safety profile., (© The Author 2015. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

The antibacterial mechanism of the Cu-containing materials has not been fully understood although such understanding is crucial for the sustained clinical use of Cu-containing antibacterial materials such as bone implants. The aim of this study is to investigate the molecular mechanisms by which the Gram-positive Staphylococcus aureus is inactivated through Cu-bearing titanium alloys (Ti6Al4V5Cu). Cu ions released from the alloys are found to contribute to lethal damage of bacteria. They destroy the permeability of the bacterial membranes, resulting in the leakage of reducing sugars and proteins from the cells. They also promote the generation of bacteria-killing reactive oxygen species (ROS). The ROS production is confirmed by several assays including fluorescent staining of intracellular oxidative stress, detection of respiratory chain activity, and measurement of the levels of lipid peroxidation, catalase, and glutathione. Furthermore, the released Cu ions show obvious genetic toxicity by interfering the replication of nuc (species-specific) and 16SrRNA genes, but with no effect on the genome integrity. All of these effects lead to the antibacterial effect of Ti6Al4V5Cu. Collectively, our work reconciles the conflicting antibacterial mechanisms of Cu-bearing metallic materials or nanoparticles reported in the literature and highlights the potential use of Ti6Al4V5Cu alloys in inhibiting bacterial infections., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A putative regulatory gene ttmRIV located in the tetramycin biosynthetic gene cluster was found in Streptomyces ahygroscopicus. In-frame deletion of ttmRIV led to abolishment of tetramycin and significant enhancement of nystatin A1, whose production reached 2.1-fold of the H42 parental strain. Gene complementation by an integrative plasmid carrying ttmRIV restored tetramycin biosynthesis revealed that ttmRIV was indispensable to tetramycin biosynthesis. Gene expression analysis of the H42 strain and its mutant strain ΔttmRIV via reverse transcriptase-PCR of the tetramycin gene cluster demonstrated that the expression levels of most biosynthetic genes were reduced in ΔttmRIV. Results of electrophoretic mobility shift assays showed that TtmRIV bound the putative promoters of several genes in the tetramycin pathway. Thus, TtmRIV is a pathway-specific positive regulator activating the transcription of the tetramycin gene cluster in S. ahygroscopicus. Providing an additional copy of ttmRIV under the control of the ermEp* promoter in the H42 strain boosted tetramycin A production to 3.3-fold.

The aim of this study was to develop a semi-mechanistic pharmacokinetic/pharmacodynamic (PK/PD) model to evaluate the in vitro synergy between vertilmicin and ceftazidime against Pseudomonas aeruginosa. The in vitro antimicrobial activity of vertilmicin alone was initially assessed by static and dynamic time-kill experiments against three bacterial strains, including MSSA, MRSA and P. aeruginosa. The combined killing effect with ceftazidime was then evaluated in a static time-kill study against P. aeruginosa. Vertilmicin displayed a concentration-dependent killing effect against the three bacterial strains, and its short half-life may possibly have a dramatic impact on antimicrobial activities. A two-compartment pharmacodynamic model consisting of drug-susceptible and -resistant compartments was developed to characterise the relationship between drug exposure and bacterial response for the time-kill curves from both monotherapy and combination therapy. Loewe additivity was incorporated into the pharmacodynamic model to describe the drug-drug interactive effect in the combination therapy. For monotherapy, the estimated EC50 of the dynamic time-kill study against each strain was close to its MIC but was higher than that of the static time-kill study. The EC50 of combination therapy was estimated at 2.67 mg/L compared with 4.54 mg/L in monotherapy, indicating an enhanced bactericidal capacity. The drug-drug interactive effect was not significantly synergistic but highly varied at each specific combination. Potential synergistic combinations could be screened using PK/PD modelling and simulation. These results demonstrated that PK/PD modelling provides an innovative approach to assist dose selection of combination vertilmicin and ceftazidime for future clinical study design., (Copyright © 2014 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved.)

Complete and independent tetramycin and nystatin gene clusters containing varying lengths of type I polyketide synthase (PKS) genes were isolated from Streptomyces ahygroscopicus, a producer of tetramycin (a tetraene) in large amounts and nystatin A1 (a heptaene) in small amounts. Tetramycin was similar to pimaricin, and nystatin A1 was similar to amphotericin. All these polyene macrolide antibiotics possessed the same macrolactone ring biosynthesized from coenzyme A precursors by PKSs but had different number of atoms in the macrolactone ring and side groups. Because tetramycin and nystatin shared limited coenzyme A precursors in the same producer organism, blocking the consumption of precursors in tetramycin pathway may increase the coenzyme A pool. Thus, we genetically manipulated the tetramycin PKS to enhance nystatin production. The type I PKS ttmS1 gene mutant abolished production of tetramycin and had a beneficial effect on the production of nystatin A1. For the mutant, the yield of nystatin A1 was increased by 10-fold compared to that of the wild-type. Thus, deletion of the tetramycin pathway redirected precursor metabolic fluxes and provided an easy genetic approach to manipulate organisms and to increase production levels of a precise target., (Copyright © 2013 Elsevier GmbH. All rights reserved.)

Genome mining led to the discovery of a novel aminocoumarin gene cluster in the rare actinomycete Catenulispora acidiphila DSM 44928. Sequence analysis revealed the presence of genes putatively involved in export/resistance, regulation, and biosynthesis of the aminocoumarin moiety and its halogenation, as well as several genes with so far unknown function. Two new aminocoumarins, cacibiocin A and B, were identified in the culture broth of C. acidiphila. Heterologous expression of the putative gene cluster in Streptomyces coelicolor M1152 confirmed that this cluster is responsible for cacibiocin biosynthesis. Furthermore, total production levels of cacibiocins could be increased by heterologous expression and screening of different culture media from an initial yield of 4.9 mg L(-1) in C. acidiphila to 60 mg L(-1) in S. coelicolor M1152. By HR-MS and NMR analysis, cacibiocin A was found to contain a 3-amino-4,7-dihydroxycoumarin moiety linked by an amide bond to a pyrrole-2,5-dicarboxylic acid. The latter structural motif has not been identified previously in any natural compound. Additionally, cacibiocin B contains two chlorine atoms at positions 6' and 8' of the aminocoumarin moiety., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Purpose: To evaluate the ocular pharmacokinetics of clarithromycin (CLA) eye drops topically applied to the corneas of rabbits., Methods: One 50-μL drop of CLA (0.25%) was administered to each New Zealand white rabbit in a single dose group, and one 50-μL drop of CLA was administered 6 times at 5-min intervals to each rabbit in a loading dose group. The effect of debridement on corneal penetration was also investigated in a de-epithelium group. The drug concentrations in the cornea and aqueous humor (AH) were assayed using high-performance liquid chromatography with tandem mass spectrometry (HPLC-MS/MS) analysis., Results: Maximum CLA levels were achieved in the corneas and AH at 15 and 60 min, respectively, in the intact epithelium eyes in the single dose group (24.54±10.64 μg/g and 0.78±0.22 μg/mL, respectively, mean±the standard error of the mean, n=8). In the loading dose group, 30 min after the last application, the CLA level in the corneas reached 92.26±17.62 μg/g. In the loading dose group, the drug levels in the corneas and AH were significantly increased compared with the drug levels in the corneas with the intact epithelium and de-epithelium eyes in the single dose group at the corresponding time points (P<0.05). The estimated CLA half-lives in the corneas and AH for the intact eyes were 103.28 and 132.61 min, respectively., Conclusion: Therapeutic CLA levels can be achieved in rabbit corneas after topically applying the drug with eye drops.

To identify the most active antimicrobial fraction of Folium Syringae, four common pathogens were used in an in vitro screening. The results indicated that the combination of the 30% and 60% ethanol fraction (FSC) obtained from the water extraction was the most active fraction with a minimal inhibitory concentration of 0.65 mg mL(-1). FSC was also found to be able to protect mice from a lethal infection of Staphylococcus aureus at clinical dosage (0.2 g kg(-1)) with a survival rate of 83.3%. The antibacterial activity of FSC was then tested using the serum pharmacology method which revealed that FSC exhibits a more long-lasting activity than the positive control (levofloxacin hydrochloride). The main components were confirmed to be iridoid glycosides and flavones by HPLC-MS analysis.

The model organism Streptomyces coelicolor A3(2) harbors a 356-kb linear plasmid, SCP1. We report here development of a recombinational cloning method for deleting large segment from one telomere of SCP1 followed by replacing with the telomere of pSLA2 and sequentially inserting with the overlapping cosmids in vivo. The procedure depends on homologous recombination coupled with cleavage at telomere termini by telomere terminal protein. Using this procedure, we cloned the 81-kb avermectin and the 76-kb spinosad biosynthetic gene clusters into SCP1. Heterologous expression of avermectin production in S. coelicolor was detected. These results demonstrate the utility of SCP1 for cloning large DNA segments such as antibiotic biosynthetic gene clusters., (© 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.)

Autophagy is a cellular lysosome-dependent catabolic mechanism mediating the turnover of intracellular organelles and long-lived proteins. We show that antimycin A, a known inhibitor of mETC complex III, can inhibit autophagy. A structural and functional study shows that four close analogs of antimycin A that have no effect on mitochondria inhibition also do not inhibit autophagy, whereas myxothiazol, another mETC complex III inhibitor with unrelated structure to antimycin A, inhibits autophagy. Additionally, antimycin A and myxothiazol cannot inhibit autophagy in mtDNA-depleted H4 and mtDNA-depleted HeLa cells. These data suggest that antimycin A inhibits autophagy through its inhibitory activity on mETC complex III. Our data suggest that mETC complex III may have a role in mediating autophagy induction., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

An automated system has been developed for the determination of trace tetracycline antibiotics (TCs) in egg samples, based on online molecularly imprinted solid-phase extraction (MISPE) coupling with high-performance liquid chromatography (HPLC). Oxytetracycline and chlortetracycline were chosen as mixed templates to synthesize highly selective molecularly imprinted polymers for online extraction. Under the optimal online MISPE-HPLC condition, 10 mL egg samples were injected into the MISPE column and then the matrix was washed out. By rotating the switching valve, TCs were transferred to the analytical column and then separated by HPLC. Because sample pretreatment and chromatographic separation were carried out simultaneously, the whole analytical time (18 min) was significantly shortened compared with conventional offline techniques. The detection limits ranged from 0.8 to 1.3 ng/g. The enhancement factors were in the range of 159-410. The spiked recoveries of TCs in real egg samples ranged from 91.6 to 107.6% and the relative standard deviations (RSDs) were not higher than 4.0%., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Genetic engineering as an important approach to strain optimization has received wide recognition. Recent advances in the studies on the biosynthetic pathways and gene clusters of Streptomyces make stain optimization by genetic alteration possible. Kanamycin B is a key intermediate in the manufacture of the important medicines dibekacin and arbekacin, which belong to a class of antibiotics known as the aminoglycosides. Kanamycin could be prepared by carbamoylkanamycin B hydrolysis. However, carbamoylkanamycin B production in Streptomyces tenebrarius H6 is very low. Therefore, we tried to obtain high kanamycin B-producing strains that produced kanamycin B as a main component. In our work, aprD3 and aprD4 were clarified to be responsible for deoxygenation in apramycin and tobramycin biosynthesis. Based on this information, genes aprD3, aprQ (deduced apramycin biosynthetic gene), and aprD4 were disrupted to optimize the production of carbamoylkanamycin B. Compared with wild-type strain, mutant strain SPU313 (ΔaprD3, ΔaprQ, and ΔaprD4) produced carbamoylkanamycin B as a single antibiotic, whose production increased approximately fivefold. To construct a strain producing kanamycin B instead of carbamoylkanamycin B, the carbamoyl-transfer gene tacA was inactivated in strain SPU313. Mutant strain SPU314 (ΔaprD3, ΔaprQ, ΔaprD4, and ΔtacA) specifically produced kanamycin B, which was proven by LC-MS. This work demonstrated careful genetic engineering could significantly improve production and eliminate undesired products.

In this study, the effects of Benzoinum and Styrax on Escherichia coli (E. coli) growth were investigated by microcalorimetry. Using a TAM Air Isothermal Calorimeter, ampoule method, the power-time curves of E. coli growth at 37°C affected by Benzoinum and Styrax were measured. By analysing some quantitative thermokinetic parameters, such as growth rate constants k, the maximum heat-out power Pm, the time of the maximum heat-out power tm, the total heat production Qt and inhibitory ratio I, one could find that low concentrations (0-3.9 mg mL(-1)) of Benzoinum and Styrax had stimulation effects on E. coli growth, and high concentrations (7.8-125.0 mg mL(-1)) of these two drugs would inhibit the growth of the bacteria. The antibacterial effects of Benzoinum and Styrax can also be expressed as half inhibitory concentration IC50. The IC50 values for Benzoinum and Styrax are 78.5 and 88.0 mg mL(-1), respectively, which suggests that the antibacterial effect of Benzoinum on E. coli was much stronger than that of Styrax. This study provides a useful method to investigate the effects of herbal medicines on microbes. It also supplies some references for the application of Benzoinum and Styrax in clinical treatment.

In this study, silver-loaded coral hydroxyapatites (SLCHAs) were used as scaffolds for bone tissue engineering. The SLCHAs were prepared by surface adsorption process and ion-exchange reaction between Ca(2+) of coral hydroxyapatite (CHA) and Ag(+) of silver nitrate with different concentrations at room temperature. The properties of the composite SLCHAs were investigated by inductively coupled plasma-atomic emission spectrometry (ICP-AES), scanning electron microscropy (SEM) equipped with backscattered electron detector (BSE), and energy-dispersive X-ray spectrometer (EDS). The SEM images showed that the morphology of the SLCHAs depended on the content of Ag(+), and the silver ions were uniformly distributed on the surface of SLCHAs. The ICP-AES results demonstrated that the silver content of the SLCHAs decreased along with the decrease of the concentration of silver nitrate. The SLCHAs were found effective against Escherichia coli and Staphylococcus aureus by antibacterial test. Mouse embryonic pre-osteoblast cells (MC3T3-E1) were used to test the cytocompatibility of SLCHAs, CHA, and pure coral. Cell morphology and cell proliferation were studied with SEM, laser scanning confocal microscope (LSCM), and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay after 1, 3, and 5 days of culture. The results indicated the cell morphology and proliferation on the scaffolds of Ag(+) (13.6 microg/ml)/CHA and Ag(+) (1.7 microg/ml)/CHA were better than that on Ag(+) (170 microg/ml)/CHA. In addition, adhesion of MC3T3-E1 on the scaffolds showed that the confluent cells showed fusiform shape and arranged tightly on the scaffolds. All the results showed that the antibacterial SLCHAs would have potential clinical application as the scaffolds for bone tissue engineering.

We developed in the present study a set of molecularly imprinted polymers (MIPs) by precipitation polymerization, using four members of tetracycline antibiotics (TCs) as templates (Oxytetracycline, Tetracycline, Chlortetracycline and Doxycycline). Then, based on the imprinting effect of different MIPs (TCs), Oxytetracycline and Chlortetracycline were chosen as mixed-templates to synthesize high selective MIPs for recognition of a family of analytes. And the characterization of obtained MIPs was analyzed by FESEM analysis, Brunauer-Emmett-Teller (BET) method, polymer size analysis, and determination of swelling ratio and COOH capacity. It was shown that the optimal imprinting factors of TCs on mixed-templates MIPs were more than 6.0 and the maximum binding amount of TCs were about 27 micromol g(-1) (Oxytetracycline), 35 micromol g(-1) (Tetracycline), 35 micromol g(-1) (Chlortetracycline) and 39 micromol g(-1) (Doxycycline), respectively. Finally, the mixed-templates MIPs were shown to be promising for on-line solid-phase extraction-HPLC-UV determination of trace TCs in foodstuffs. With a sample loading volume of 10 mL, the enhancement factors were in the range of 159-410., (Copyright 2010 Elsevier B.V. All rights reserved.)

Streptomyces tenebrarius H6 mainly produces three kinds of antibiotics: apramycin, carbamoyltobramycin and some carbamoylkanamycin B. In our present study, a dehydrogenase gene tacB in the tobramycin biosynthetic gene cluster was disrupted by in-frame deletion. The result of TLC bio-autograph analysis demonstrated the disruption mutant strain produced apramycin and a new antibiotic. The new antibiotic was identified as 3'-deoxy-carbamoylkanamycin C by MS and NMR analysis after isolation and purification. The disruption mutant was restored to produce carbamoyltobramycin in a complementation experiment by the intact tacB gene. Our studies suggested that the tacB gene encodes a 6'-dehydrogenase, which reduces the 6'-hydroxyl group of paromamine to a keto group, thus facilitating the transfer of an aminogroup to form neamine. This study is the first report on the generation of a tobramycin derivative by gene engineering, and will contribute to clarify the complete biosynthetic pathway of tobramycin.

Aim: To determine the antibiotic susceptibility of Helicobacter pylori and evaluate the efficacy of a clarithromycin-based triple therapy in relation to antibiotic resistance., Methods: Consecutive patients referred for upper endoscopy due to dyspeptic symptoms were recruited. Gastric biopsies were obtained for the CLO test, histology and culture. Antibiotic susceptibility was assessed by the E-test. Patients with H. pylori infection received rabeprazole 20 mg, clarithromycin 500 mg, and amoxicillin 1,000 mg, all twice daily for 7 days., Results: Of 234 patients recruited, 124 were H. pylori-positive and culture was successful in 102 patients. The updated prevalences of resistance to clarithromycin, amoxicillin and metronidazole were 7.8, 0 and 39.2%, respectively. A total of 86 patients received 1-week triple therapy with rabeprazole 20 mg, clarithromycin 500 mg, and amoxicillin 1,000 mg, all twice daily, and 81 patients attended the follow-up test. Eradication rates by per-protocol and intention-to-treat analysis were 92.6 and 87.2%, respectively. The eradication rate by per protocol was significantly higher in patients with clarithromycin-susceptible strains than in those with clarithromycin-resistant strains (98.6 vs. 28.6%, p < 0.001)., Conclusion: Clarithromycin resistance reduces the clinical efficacy of clarithromycin-based triple therapy. However, due to the low prevalence of clarithromycin resistance, clarithromycin-based therapy is still the first choice for clinical use., (Copyright 2006 S. Karger AG, Basel.)

Aim: To test the efficacy of rabeprazole, levofloxacin and rifabutin triple therapy vs. quadruple therapy for the second-line treatment of Helicobacter pylori infection., Methods: One hundred and nine patients who had failed previous H. pylori eradication were randomized to receive: (i) rabeprazole, 20 mg b.d., rifabutin, 300 mg once daily, and levofloxacin, 500 mg once daily, for 7 days (triple therapy); or (ii) rabeprazole, 20 mg b.d., metronidazole, 400 mg t.d.s., bismuth subcitrate, 120 mg q.d.s., and tetracycline, 500 mg q.d.s., for 7 days (quadruple therapy). Endoscopy and culture were performed before treatment., Results: The clarithromycin (79% vs. 21%, P < 0.001) and metronidazole (89% vs. 40%, P < 0.001) resistance rates were significantly higher in patients with previous exposure than in those with no previous exposure. The intention-to-treat and per protocol eradication rates were 91%/91% for the triple therapy group and 91%/92% for the quadruple therapy group. For patients with double resistance to metronidazole and clarithromycin, the eradication rates were 85% (17/20) in the triple therapy group and 87% (13/15) in the quadruple therapy group. Compliance was greater than 95% for both regimens., Conclusion: Rabeprazole, levofloxacin and rifabutin-based triple therapy and quadruple therapy were equally effective as second-line treatments for H. pylori infection.