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Multicellular cooperation in actinomycetes is a division of labor-based beneficial trait where phenotypically specialized clonal subpopulations, or genetically distinct lineages, perform complementary tasks. The division of labor improves the access to nutrients and optimizes reproductive and vegetative tasks while reducing the costly production of secondary metabolites and/or of secreted enzymes. In this study, we took advantage of the possibility to isolate genetically distinct lineages deriving from the division of labor, for the isolation of heterogeneous teicoplanin producer phenotypes from Actinoplanes teichomyceticus ATCC 31121. In order to efficiently separate phenotypes and associated genomes, we produced and regenerated protoplasts. This approach turned out to be a rapid and effective strain improvement method, as it allowed the identification of those phenotypes in the population that produced higher teicoplanin amounts. Interestingly, a heterogeneous teicoplanin complex productivity pattern was also identified among the clones. This study suggests that strain improvement and strain maintenance should be integrated with the use of protoplasts as a strategy to unravel the hidden industrial potential of vegetative mycelium.

Multicellular cooperation in actinomycetes is a division of labor-based beneficial trait where phenotypically specialized clonal subpopulations, or genetically distinct lineages, perform complementary tasks. The division of labor improves the access to nutrients and optimizes reproductive and vegetative tasks while reducing the costly production of secondary metabolites and/or of secreted enzymes. In this study, we took advantage of the possibility to isolate genetically distinct lineages deriving from the division of labor, for the isolation of heterogeneous teicoplanin producer phenotypes from Actinoplanes teichomyceticus ATCC 31121. In order to efficiently separate phenotypes and associated genomes, we produced and regenerated protoplasts. This approach turned out to be a rapid and effective strain improvement method, as it allowed the identification of those phenotypes in the population that produced higher teicoplanin amounts. Interestingly, a heterogeneous teicoplanin complex productivity pattern was also identified among the clones. This study suggests that strain improvement and strain maintenance should be integrated with the use of protoplasts as a strategy to unravel the hidden industrial potential of vegetative mycelium.

In the era of antimicrobial resistance, the use of nanoconjugated antibiotics is regarded as a promising approach for preventing and fighting infections caused by resistant bacteria, including those exacerbated by the formation of difficult-to-treat bacterial biofilms. Thanks to their biocompatibility and magnetic properties, iron oxide nanoparticles (IONPs) are particularly attractive as antibiotic carriers for the targeting therapy. IONPs can direct conjugated antibiotics to infection sites by the use of an external magnet, facilitating tissue penetration and disturbing biofilm formation. As a consequence of antibiotic localization, a decrease in its administration dosage might be possible, reducing the side effects to non-targeted organs and the risk of antibiotic resistance spread in the commensal microbiota. Here, we prepared nanoformulations of the ‘last-resort’ glycopeptides teicoplanin and vancomycin by conjugating them to IONPs via surface functionalization with (3-aminopropyl) triethoxysilane (APTES). These superparamagnetic NP-TEICO and NP-VANCO were chemically stable and NP-TEICO (better than NP-VANCO) conserved the typical spectrum of antimicrobial activity of glycopeptide antibiotics, being effective against a panel of staphylococci and enterococci, including clinical isolates and resistant strains. By a combination of different methodological approaches, we proved that NP-TEICO and, although to a lesser extent, NP-VANCO were effective in reducing biofilm formation by three methicillin-sensitive or resistant Staphylococcus aureus strains. Moreover, when attracted and concentrated by the action of an external magnet, NP-TEICO exerted a localized inhibitory effect on S. aureus biofilm formation at low antibiotic concentration. Finally, we proved that the conjugation of glycopeptide antibiotics to IONPs reduced their intrinsic cytotoxicity toward a human cell line.

At the end of December 2019, a novel coronavirus was identified which caused severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with a disease known as coronavirus disease 2019 (COVID-19). The virus first originated in the city of Wuhan in China, causing symptoms such as pneumonic plague, which began in the Wuhan and then spread throughout the world with high transmission efficiency. Special precautions and care are needed such as leaving the public area, covering your mouth with a mask, not shaking hands, washing hands, and sanitation from time to time. Infection due to SARS-CoV-2 shows several symptoms, one of which is very often the patient shows difficulty breathing. Currently, COVID-19 has been declared a global pandemic and has almost attacked all countries in the world, including in India which has one of the largest human populations in the entire world. One of the challenges in handling COVID-19 is the unavailability of drugs or special vaccines to treat the disease, so clinical practitioners and academics are currently testing various drugs to see how they affect the COVID-19 patients. Some of the drugs tested provide effective mechanisms against SARS-CoV-2, such as chloroquine, remdesivir, lopinavir, and vaccines under development. These drugs are still being tested and are now at the forefront to combat the effects of SARS-CoV-2 infection. This review article will discuss all kinds of ins and outs of SARS-CoV-2 and COVID-19, including the transmission method, how to prevent it, as well as various drugs and vaccines currently used in handling COVID-19.

Clostridium difficile je najčešći uzročnik postantibiotske dijareje i pseudomembranoznog kolitisa. Nekada sporadična infekcija, poslednjih petnaest godina dobija razmere globalne epidemije i postaje jedna od vodećih intrahospitalnih infekcija u svetu i značajan uzrok smrti naročito među starijima od 65 godina. Porast broja obolelih, kao i sve veći broj bolesnika sa teškom kliničkom slikom i komplikacijama te sve češća pojava recidiva i slučajeva refraktarnih na standardnu terapiju vezuju se za razvoj hipervirulentnog soja bakterije, NAP1/BI/027. Spektar kliničkih oblika C. difficile infekcije obuhvata blagu do umerenu bolest u vidu dijareje bez kolitisa, tešku i tešku komplikovanu formu koja se karakteriše pojavom ileusa, toksičnog megakolona, hipotenzije sa primenom vazopresora, organskom disfunkcijom, izmenjenim mentalnim statusom, leukocitozom ≥ 35000/mm3 ili leukopenijom < 2000/mm3. Glavni problem u svakodnevnom kliničkom radu sa obolelima od C. difficle infekcije predstavlja velika učestalost recidiva bolesti, kao i sve češća pojava refraktarnih slučajeva. Standardnu terapiju C. difficile infekcije čine metronidazol i vankomicin, a poslednjih godina i fidaksomicin, čijim primenom je samo delimično smanjen rizik od recidiva. U ranije sprovedenim istraživanjima o primeni teikoplanina u lečenju C. difficile infekcije teikoplanin se pokazao kao uspešan, međutim, ova istraživanja su sprovedena u vreme pre pojave hipervirulentnog soja i „epidemije“ C. difficile infekcije i obuhvatala su mali broj ispitanika. CILJ: Cilj ovog istraživanja bio je da se ispita i uporedi ishod C. difficile infekcije kod bolesnika sa teškom formom bolesti lečenih teikoplaninom i vankomicinom u pogledu postignutog procenta kliničkog izlečenja, vremena od početka terapije do prestanka proliva, smrtnosti kao i učestalosti recidiva nakon 8 nedelja praćenja. Drugi cilj je bio da se utvrdi efikasnost peroralno primenjenog teikoplanina (u pogledu kliničkog izlečenja, smrtnosti, vremena od početka

Background. Teicoplanin and vancomycin are glycopeptide antibiotics currently in use for treatment of multidrug-resistant bacterial infections. Scope and Approach. Severe undesirable effects, such as ototoxicity, nephrotoxicity and neutropenia have been reported for vancomycin and teicoplanin, which necessitates monitoring the concentration of these two drugs in different biological samples. In order to obtain precise and accurate results, sensitive, reliable and fast methods are necessary. The main aim of this mini review is to give a clear and concise overview of the recently developed, validated, novel and improved methods for glycopeptide antibiotic analyses in various biological matrices. Also, the variability of the matrices requires optimal and effective sample preparation procedures to be developed, and so these are discussed. Key Findings and Conclusions. Different liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods have been described for quantitative determination of glycopeptide antibiotics in various biological matrices. It was shown that protein precipitation was a convenient method for sample preparation despite the high number of novel sample preparation methods., Uvod. Teikoplanin i vankomicin su antibiotici glikopeptidne strukture koji se trenutno koriste u terapiji multirezistentnih bakterijskih infekcija. Cilj i pristup. Ozbiljni neželjeni efekti vankomicina i teikoplanina kao što su ototoksičnost, nefrotoksičnost i neutropenija zahtevaju njihovo praćenje u različitim tipovima biološkog materijala. Osetljiva, pouzdana i brza metoda potrebna je u cilju dobijanja tačnih i preciznih podataka o koncentraciji pomenutih jedinjenja. Cilj ovog pregleda je da da jasan i kratak prikaz o razvijenim i validiranim novim, ili unapređenim metodama za analizu glikopeptidnih antibiotika u različitim biološkim matriksima. Takođe, u radu su opisane i metode pripreme uzorka upravo zbog raznovrsnosti biološkog materijala. Ključni nalazi i zaključak. Opisane su raznovrsne LC-MS/MS metode za određivanje glikopeptidnih antibiotika u biološkom materijalu. Primećeno je da je precipitacija proteina pogodna metoda pripreme uzorka bez obzira na broj novijih metoda pripreme koje se koriste.

Teicoplanin, a glycopeptide antibiotic for methicillin-resistant Staphylococcus aureus, is recommended for therapeutic drug monitoring during treatment. Maintaining a high trough range of teicoplanin is also recommended for severe infectious disease. However, the optimal dose and interval of treatment for severe renal impairment is unknown. We report a 79-year-old man who received long-term teicoplanin treatment for methicillin-resistant Staphylococcus aureus bacteremia due to postoperative sternal osteomyelitis with renal impairment. Plasma teicoplanin trough levels were maintained at a high range (20-30 μg/mL). Although the patient required long-term teicoplanin treatment, a further decline in renal function was not observed, and blood culture remained negative after the start of treatment. Teicoplanin treatment that is maintained at a high trough level by therapeutic drug monitoring might be beneficial for severe methicillin-resistant Staphylococcus aureus infection accompanied by renal impairment.

Background: Antimicrobial stewardship teams play an important role in assisting with the optimization of antimicrobial use in acute care settings. We aimed to determine whether a rapid review by a multidisciplinary antimicrobial stewardship team would improve the timeliness of optimal antimicrobial therapy for patients with positive blood cultures. Method(s): This prospective randomized controlled trial was undertaken in two Australian hospitals. Patients received either standard care (a clinical microbiologist, registrar or laboratory scientist communicating the positive blood culture by phone to the treating doctor) or intervention (standard care plus rapid review by a multidisciplinary antimicrobial stewardship team). Outcomes included time to appropriate and/or active antimicrobial therapy and in-hospital mortality. The trial was registered on the Australian New Zealand Clinical Trials Registry (ACTRN12614000258651). Result(s): A total of 160 patients were enrolled in this study: 81 in the standard care arm and 79 in the intervention arm. Patients in the intervention arm were commenced earlier on active (HR 8.02, 95% CI: 2.15-29.91) and appropriate antimicrobials (HR 1.95, 95% CI: 1.13-3.38), with a higher proportion of patients allocated to the intervention arm receiving active therapy at 48 h (96% versus 82%) and appropriate therapy at 72 h (70% versus 54%). The majority of patients where the blood culture was a contaminant were not started on antimicrobial therapy, and there were no significant differences in time to cessation of antimicrobial therapy. Conclusion(s): Antimicrobial stewardship team review of patients with pathogenic positive blood cultures improved the time to both active and appropriate antimicrobial therapy.Copyright © The Author 2016. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved.

Background: Antimicrobial stewardship teams play an important role in assisting with the optimization of antimicrobial use in acute care settings. We aimed to determine whether a rapid review by a multidisciplinary antimicrobial stewardship team would improve the timeliness of optimal antimicrobial therapy for patients with positive blood cultures. Method(s): This prospective randomized controlled trial was undertaken in two Australian hospitals. Patients received either standard care (a clinical microbiologist, registrar or laboratory scientist communicating the positive blood culture by phone to the treating doctor) or intervention (standard care plus rapid review by a multidisciplinary antimicrobial stewardship team). Outcomes included time to appropriate and/or active antimicrobial therapy and in-hospital mortality. The trial was registered on the Australian New Zealand Clinical Trials Registry (ACTRN12614000258651). Result(s): A total of 160 patients were enrolled in this study: 81 in the standard care arm and 79 in the intervention arm. Patients in the intervention arm were commenced earlier on active (HR 8.02, 95% CI: 2.15-29.91) and appropriate antimicrobials (HR 1.95, 95% CI: 1.13-3.38), with a higher proportion of patients allocated to the intervention arm receiving active therapy at 48 h (96% versus 82%) and appropriate therapy at 72 h (70% versus 54%). The majority of patients where the blood culture was a contaminant were not started on antimicrobial therapy, and there were no significant differences in time to cessation of antimicrobial therapy. Conclusion(s): Antimicrobial stewardship team review of patients with pathogenic positive blood cultures improved the time to both active and appropriate antimicrobial therapy.Copyright © The Author 2016. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved.

Eggerthella lenta is an emerging pathogen that has been underrecognized due to historical difficulties with phenotypic identification. Until now, its pathogenicity, antimicrobial susceptibility profile, and optimal treatment have been poorly characterized. In this article, we report the largest cohort of patients with E. lenta bacteremia to date and describe in detail their clinical features, microbiologic characteristics, treatment, and outcomes. We identified 33 patients; the median age was 68 years, and there was no gender predominance. Twenty-seven patients (82%) had serious intra-abdominal pathology, often requiring a medical procedure. Of those who received antibiotics (28/33, 85%), the median duration of treatment was 21.5 days. Mortality from all causes was 6% at 7 days, 12% at 30 days, and 33% at 1 year. Of 26 isolates available for further testing, all were identified as E. lenta by both commercially available matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) systems, and none were found to harbor a vanA or vanB gene. Of 23 isolates which underwent susceptibility testing, all were susceptible to amoxicillin-clavulanate, cefoxitin, metronidazole, piperacillin-tazobactam, ertapenem, and meropenem, 91% were susceptible to clindamycin, 74% were susceptible to moxifloxacin, and 39% were susceptible to penicillin.Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Some Australian strain types of Clostridium difficile appear unique, highlighting the global diversity of this bacterium. We examined recent and historic local isolates, finding predominantly toxinotype 0 strains, but also toxinotypes V and VIII. All isolates tested were susceptible to vancomycin and metronidazole, while moxifloxacin resistance was only detected in recent strains.Copyright © 2015 Elsevier Ltd.

Objective To describe successful termination of an outbreak of vancomycin-resistant Enterococcus faecium (VREfm) colonization within a neonatal service. Setting Multisite neonatal intensive care unit and special care nurseries within a single health care service. Participants Forty-four cases of VREfm-colonized neonatal inpatients-including 2 clinical isolates (eye swab and catheter-urine specimen) and 42 screening isolates. Interventions Active surveillance cultures, patient isolation, contact precautions, enhanced environment cleaning, and staff and parent education. Whole genome sequencing and multilocus sequence typing were used to characterize the outbreak and refine infection control procedures. Results Peak prevalence of VREfm colonization across all sites was 31% upon discovery of the outbreak. Subsequent to the intervention, transmission was halted within 8 weeks and no further isolates of the outbreak strain have been detected as of 12 months following outbreak cessation. Environmental swabs revealed VREfm colonization of baby-weighing scales, a baby bath, and a pharmacy refrigerator within the neonatal intensive care unit. All isolates were of a single multilocus sequence type (sequence type 796) and highly clonal at the core genome level. Conclusions Bundled infection control interventions were effective in rapidly terminating a clonal outbreak of sequence type 796 VREfm colonization within a neonatal inpatient service. Strain-typing and active surveillance cultures were critical in guiding the management of this outbreak. The closed environment of a neonatal unit likely facilitated eradication of the patient and environment reservoirs of VREfm colonization.Copyright © 2015 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

To analyse the possible relationship between consumption of old and new MRSA-active antibiotics and burden of MRSA in acute care hospitals in Catalonia during the period 2007-12.Fifty-four hospitals participating in the VINCat Programme were included. Proportion of MRSA (resistant isolates of Staphylococcus aureus per 100 isolates of S. aureus tested), incidence of new cases of infection [new cases of MRSA per 1000 occupied bed-days (OBD)] and incidence of cases of bacteraemia (MRSA bacteraemia cases per 1000 OBD) were determined to estimate the annual MRSA burden. Antibiotic consumption was calculated in DDD/100 OBD. Cost was expressed in euros/100 OBD.MRSA rates remained stable over the study period, with the proportion of MRSA ranging from 20% to 22.82% in 2007 and 2012, respectively (P=0.864). Consumption of old MRSA-active antibiotics (vancomycin and teicoplanin) did not change significantly, with values from 1.51 to 2.07 DDD/100 OBD (P=0.693). Consumption of new MRSA-active antibiotics (linezolid and daptomycin) increased significantly, with values rising from 0.24 to 1.49 DDD/100 OBD (P<0.001). Cost increased by almost 200%.A widespread and steady increase in consumption of new MRSA-active antibiotics was observed among acute care hospitals in Catalonia, in spite of a stable MRSA burden. At the same time, consumption of old drugs remained stable. Such trends resulted in a significant increase in cost. Our findings suggest that factors other than the proportion of methicillin resistance among S. aureus may influence the use of old and new MRSA-active antibiotics in the clinical setting.© The Author 2014. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please e-mail: journal

Eggerthella lenta is an emerging pathogen that has been underrecognized due to historical difficulties with phenotypic identification. Until now, its pathogenicity, antimicrobial susceptibility profile, and optimal treatment have been poorly characterized. In this article, we report the largest cohort of patients with E. lenta bacteremia to date and describe in detail their clinical features, microbiologic characteristics, treatment, and outcomes. We identified 33 patients; the median age was 68 years, and there was no gender predominance. Twenty-seven patients (82%) had serious intra-abdominal pathology, often requiring a medical procedure. Of those who received antibiotics (28/33, 85%), the median duration of treatment was 21.5 days. Mortality from all causes was 6% at 7 days, 12% at 30 days, and 33% at 1 year. Of 26 isolates available for further testing, all were identified as E. lenta by both commercially available matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) systems, and none were found to harbor a vanA or vanB gene. Of 23 isolates which underwent susceptibility testing, all were susceptible to amoxicillin-clavulanate, cefoxitin, metronidazole, piperacillin-tazobactam, ertapenem, and meropenem, 91% were susceptible to clindamycin, 74% were susceptible to moxifloxacin, and 39% were susceptible to penicillin.Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Some Australian strain types of Clostridium difficile appear unique, highlighting the global diversity of this bacterium. We examined recent and historic local isolates, finding predominantly toxinotype 0 strains, but also toxinotypes V and VIII. All isolates tested were susceptible to vancomycin and metronidazole, while moxifloxacin resistance was only detected in recent strains.Copyright © 2015 Elsevier Ltd.

Objective To describe successful termination of an outbreak of vancomycin-resistant Enterococcus faecium (VREfm) colonization within a neonatal service. Setting Multisite neonatal intensive care unit and special care nurseries within a single health care service. Participants Forty-four cases of VREfm-colonized neonatal inpatients-including 2 clinical isolates (eye swab and catheter-urine specimen) and 42 screening isolates. Interventions Active surveillance cultures, patient isolation, contact precautions, enhanced environment cleaning, and staff and parent education. Whole genome sequencing and multilocus sequence typing were used to characterize the outbreak and refine infection control procedures. Results Peak prevalence of VREfm colonization across all sites was 31% upon discovery of the outbreak. Subsequent to the intervention, transmission was halted within 8 weeks and no further isolates of the outbreak strain have been detected as of 12 months following outbreak cessation. Environmental swabs revealed VREfm colonization of baby-weighing scales, a baby bath, and a pharmacy refrigerator within the neonatal intensive care unit. All isolates were of a single multilocus sequence type (sequence type 796) and highly clonal at the core genome level. Conclusions Bundled infection control interventions were effective in rapidly terminating a clonal outbreak of sequence type 796 VREfm colonization within a neonatal inpatient service. Strain-typing and active surveillance cultures were critical in guiding the management of this outbreak. The closed environment of a neonatal unit likely facilitated eradication of the patient and environment reservoirs of VREfm colonization.Copyright © 2015 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

Aim: The main objective of this study is to understand the mechanism of vancomycin resistance in a Streptomyces coelicolor disrupted mutant highly resistant to vancomycin. Materials & methods: Different techniques have been performed in the study including gene disruption, primer extension, antibiotic susceptibility tests, electron microscopy, confocal microscopy, cell wall analysis and microarrays. Results: During the phenotypical characterization of mutant strains affected in phosphate-regulated genes of unknown function, we found that the S. coelicolor SCO2594 disrupted mutant was highly resistant to vancomycin and had other phenotypic alterations such as antibiotic overproduction, impaired growth and reduction of phosphate cell wall content. Transcriptomic studies with this mutant indicated a relationship between vancomycin resistance and cell wall stress. Conclusion: We identified a S. coelicolor mutant highly resistant to vancomycin in both high and low phosphate media. In addition to Van proteins, others such as WhiB or SigE appear to be involved in this regulatory mechanism.

Aim: The main objective of this study is to understand the mechanism of vancomycin resistance in a Streptomyces coelicolor disrupted mutant highly resistant to vancomycin. Materials & methods: Different techniques have been performed in the study including gene disruption, primer extension, antibiotic susceptibility tests, electron microscopy, confocal microscopy, cell wall analysis and microarrays. Results: During the phenotypical characterization of mutant strains affected in phosphate-regulated genes of unknown function, we found that the S. coelicolor SCO2594 disrupted mutant was highly resistant to vancomycin and had other phenotypic alterations such as antibiotic overproduction, impaired growth and reduction of phosphate cell wall content. Transcriptomic studies with this mutant indicated a relationship between vancomycin resistance and cell wall stress. Conclusion: We identified a S. coelicolor mutant highly resistant to vancomycin in both high and low phosphate media. In addition to Van proteins, others such as WhiB or SigE appear to be involved in this regulatory mechanism.

While developing a rapid method to detect carriers of vancomycin-resistant enterococci (VRE), we found the vanB gene by PCR in 13 of 50 human faecal specimens that did not contain culturable VRE. Passaging under antibiotic selection allowed us to isolate two species of anaerobic bacteria that were vanB PCR positive, vancomycin resistant, and teicoplanin sensitive. Sequence analysis of the 16S rRNA genes showed that one isolate resembled Eggerthella lenta (98% identity), and the other Clostridium innocuum (92% identity). Southern hybridisation and nucleotide sequencing showed a vanB locus homologous to that in VRE. We propose that vanB resistance in enterococci might arise from gene transfer in the human bowel.

While developing a rapid method to detect carriers of vancomycin-resistant enterococci (VRE), we found the vanB gene by PCR in 13 of 50 human faecal specimens that did not contain culturable VRE. Passaging under antibiotic selection allowed us to isolate two species of anaerobic bacteria that were vanB PCR positive, vancomycin resistant, and teicoplanin sensitive. Sequence analysis of the 16S rRNA genes showed that one isolate resembled Eggerthella lenta (98% identity), and the other Clostridium innocuum (92% identity). Southern hybridisation and nucleotide sequencing showed a vanB locus homologous to that in VRE. We propose that vanB resistance in enterococci might arise from gene transfer in the human bowel.

Glycopeptides (vancomycin and teicoplanin) are an alternative therapeutic in the treatment of severe infections by methicillin-resistant S. aureus strains. However, two resistance mechanisms of S. aureus have already been described: low-level resistance, characterized by an abnormal thickening of the cellular wall, present in the VISA strains, and high-level resistance, mediated by the vanA operon, which causes the replacement of D-ala - D-ala terminal residues by D-ala-D-lac, decreasing its affinity for the antibiotic. This review summarizes the history of the emergence of glycopeptide resistance in S. aureus and considers the mechanisms that determine the resistance in these organisms as a background for understanding the need and potential roles of new agents of this kind., Los glicopéptidos (vancomicina y teicoplanina) constituyen una alternativa terapéutica en el tratamiento de infecciones severas por cepas de S. aureus resistentes a meticilina. Sin embargo, ya se han descrito dos mecanismos de resistencia en S. aureus: resistencia de bajo nivel, caracterizada por un engrosamiento anormal de la pared celular, presente en las cepas VISA y, resistencia de alto nivel mediada por el operón vanA, que provoca la sustitución de los residuos terminales D-ala-D-ala por D-ala-D-lac, disminuyendo su afinidad por el antibiótico. Esta revisión resume la historia de la aparición de la resistencia a glicopéptidos en S. aureus y considera los mecanismos que determinan la resistencia en estos organismos como base para comprender la necesidad y los potenciales roles de nuevos agentes de esta clase.

The selective pressure resulting from the extensive use of antibiotics over the last 50 years has led to the emergence of bacterial resistance and to the dissemination of resistance genes among pathogenic microorganisms. Consequently, we are now at serious risk of suffering intractable, life-threatening infections. The progressive emergence and rapid dissemination of resistance to glycopeptides, the last resort for treating nosocomial infections with enterococci resistant to usual antibiotics, constitute one of the most dramatic examples of such resistance. Enterococci are normal human commensals, but are also a frequent cause of nosocomial urinary tract infections and nosocomial bacteremia. Enterococcus faecalis causes 80 to 90% of human enterococcal infections, while Enterococcus faecium accounts for most of the remainder. During the last decade, our understanding of the genetics and biochemical basis of resistance to glycopeptides has increased greatly. Furthermore, the application of molecular methods for the diagnosis of glycopeptide-resistant enterococci has provided new insights into the epidemiology of enterococcal infections.

Hemi-synthetic derivatives of glycopeptides have demonstrated bactericidal activity towards Gram-positive bacteria, including vancomycin-resistant strains (oritavancin and telavancin), and a prolonged half-life, allowing for once-daily (oritavancin and telavancin) or once-weekly (dalbavancin) administration. These compounds have proved effective for the treatment of infections caused by multidrug-resistant Gram-positive bacteria, including complicated skin and skin structure infections (oritavancin, telavancin and dalbavancin), bacteremia (oritavancin and dalbavancin) and nosocomial pneumonia. This review compares the antibacterial activity and clinical activity of three glycopeptides, oritavancin, telavancin and dalbavancin, and the natural lipoglycopeptide, ramoplanin, which, being unstable in the bloodstream, is administered orally to treat Clostridium difficile colitis and for digestive tract decontamination. All of these compounds, with the exception of oritavancin, have received Fast Track designation from the FDA because of their clinical efficacy.

Vancomycin and teicoplanin are still the only glycopeptide antibiotics available for use in humans. Emergence of resistance in enterococci and staphylococci has led to restriction of their use to severe infections caused by Gram-positive bacteria for which no other alternative is acceptable (because of resistance or allergy). In parallel, considerable efforts have been made to produce semisynthetic glycopeptides with improved pharmacokinetic and pharmacodynamic properties, and with activity towards resistant strains. Several molecules have now been obtained, helping to better delineate structure-activity relationships. Two are being currently evaluated for skin and soft tissue infections and are in phases II/III. The first, oritavancin (LY333328), is the 4'-chlorobiphenylmethyl derivative of chloroeremomycin, an analogue to vancomycin. It is characterised by: i) a spectrum covering vancomycin-resistant enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA) and to some extent glycopeptide-intermediate S. aureus (GISA); ii) rapid bactericidal activity including against the intracellular forms of enterococci and staphylococci; and iii) a prolonged half-life, allowing for daily administration. The second molecule is dalbavancin (BI397), a derivative of the teicoplanin analogue A40926. Dalbavancin has a spectrum of activity similar to that of oritavancin against vancomycin-sensitive strains, but is not active against VRE. It can be administered once a week, based on its prolonged retention in the organism. Despite these remarkable properties, the use of these potent agents should be restricted to severe infections, as should the older glycopeptides, with an extension towards resistant or poorly sensitive bacteria, to limit the risk of potential selection of resistance.

Vancomycin and teicoplanin are the two glycopeptides currently used in the clinics for the treatment of multiresistant infections by Gram-positive organisms. The development of resistance in enterococci and staphylococci has stimulated the search for new derivatives with improved activity, particularly against strains resistant to conventional derivatives. Three of these, obtained by hemi-synthesis starting from natural compounds, are now in clinical development (oritavancin and telavancin, as derivatives of vancomycin; and dalbavancin, as a derivative of teicoplanin). The presence of a lipophilic tail on these molecules results in them having a prolonged half-life. It also modifies their mode of action, conferring to them a concentration-dependent bactericidal activity. Their spectrum of activity includes methicillin-susceptible or methicillin-resistant staphylococci, penicillin-resistant pneumococci and enterococci (including vancomycin-resistant strains for oritavancin and telavancin). Ongoing clinical studies are evaluating the efficacy and safety of these molecules for the treatment of complicated skin and soft tissue infections and bactereamia, in a once-daily (oritavancin, telavancin) or once-weekly (dalbavancin) scheme of administration. Despite these remarkable properties, the use of these potent molecules should be restricted to severe infections by multiresistant organisms to limit the risk of selection of resistance.

OBJECTIVE: The 'HICPAC guidelines', published in the USA in 1995 stressed the crucial role of restrictive usage of glycopeptides in the strategy to limit the emergence and spread of resistant enterococci. Because controversy still remains in Belgium on the necessity and feasability of restricting glycopeptide usage, the infectious diseases advisory board (IDAB) developed a consensus statement on the judicious use of glycopeptides in Belgium. METHODS: The literature on the indications for glycopeptide treatment was reviewed, categorized and discussed by a working party of the IDAB.Consequently, the IDAB reached consensus on the warranted indications for glycopeptide use in Belgium. RESULTS: The opinion of the IDAB-members is reported in a consensus statement specifying the indications for treatment and for prophylaxis with glycopeptide antimicrobials, as well as the situations where glycopeptides should not be used, taking into account the specific epidemiology of bacterial resistance, the availability of antibiotics and the common prescribing practices in Belgium. CONCLUSIONS: The IDAB concludes that restrictive usage of glycopeptides must also be a priority in Belgium. Guidelines on the judicious use of these antibiotics adapted to the national situations must contribute to this objective.

OBJECTIVE: The 'HICPAC guidelines', published in the USA in 1995 stressed the crucial role of restrictive usage of glycopeptides in the strategy to limit the emergence and spread of resistant enterococci. Because controversy still remains in Belgium on the necessity and feasability of restricting glycopeptide usage, the infectious diseases advisory board (IDAB) developed a consensus statement on the judicious use of glycopeptides in Belgium. METHODS: The literature on the indications for glycopeptide treatment was reviewed, categorized and discussed by a working party of the IDAB.Consequently, the IDAB reached consensus on the warranted indications for glycopeptide use in Belgium. RESULTS: The opinion of the IDAB-members is reported in a consensus statement specifying the indications for treatment and for prophylaxis with glycopeptide antimicrobials, as well as the situations where glycopeptides should not be used, taking into account the specific epidemiology of bacterial resistance, the availability of antibiotics and the common prescribing practices in Belgium. CONCLUSIONS: The IDAB concludes that restrictive usage of glycopeptides must also be a priority in Belgium. Guidelines on the judicious use of these antibiotics adapted to the national situations must contribute to this objective.

Three vancomycin-dependent clinical isolates of Enterococcus faecalis of the VanB type were studied by determining (i) the sequence of the ddl gene encoding the host D-Ala:D-Ala ligase and the vanSB-vanRB genes specifying the two-component regulatory system that activates transcription of the vanB operon, (ii) the level of expression of resistance genes by using DD-dipeptidase activity as a reporter, and (iii) the proportions of the peptidoglycan precursors synthesized. Each strain had a mutation in ddl leading to an amino acid substitution (D295 to V; T316 to I) or deletion (DAK251-253 to E) at invariant positions in D-Ala:D-Ala, D-Ala:D-Lac, and D-Ala:D-Ser ligases. These mutations resulted in impaired host D-Ala:D-Ala ligases since only precursors terminating in D-Ala-D-Lac were synthesized under vancomycin-inducing conditions. Two types of vancomycin-independent revertants of one isolate were obtained in vitro after growth in the absence of vancomycin: (i) vancomycin-resistant, teicoplanin-susceptible mutants had a 6-bp insertion in the host ddl gene, causing the E251-to-EYK change that restored D-Ala:D-Ala ligase activity, (ii) constitutive vancomycin-resistant, teicoplanin-resistant mutants had substitutions (S232 to F or E247 to K) in the vicinity of the autophosphorylation site of the VanSB sensor and produced exclusively precursors ending in D-Ala-D-Lac. Vancomycin- and teicoplanin-dependent mutants obtained by growth in the presence of teicoplanin had an 18-bp deletion in VanSB, affecting residues 402 to 407 and overlapping the G2 ATP binding domain. The rapid emergence of vancomycin-independent revertants in vitro suggests that interruption of vancomycin therapy may not be sufficient to cure patients infected with vancomycin-dependent enterococci.

Most bacteria synthesize muramyl-pentapeptide peptidoglycan precursors ending with a D-alanyl residue (e.g., UDP-N-acetylmuramyl-L-Ala-gamma-D-Glu-L-Lys-D-Ala-D-Ala). However, it was recently demonstrated that other types of precursors, notably D-lactate-ending molecules, could be synthesized by several lactic acid bacteria. This particular feature leads to vancomycin resistance. Vancomycin is a glycopeptide antibiotic that blocks cell wall synthesis by the formation of a complex with the extremity of peptidoglycan precursors. Substitution of the terminal D-alanine by D-lactate reduces the affinity of the antibiotic for its target. Lactobacillus plantarum is a lactic acid bacterium naturally resistant to vancomycin. It converts most of the glycolytic pyruvate to L- and D-lactate by using stereospecific enzymes designated L- and D-lactate dehydrogenases, respectively. In the present study, we show that L. plantarum actually synthesizes D-lactate-ending peptidoglycan precursors. We also report the construction of a strain which is deficient for both D- and L-lactate dehydrogenase activities and which produces only trace amounts of D- and L-lactate. As a consequence, the peptidoglycan synthesis pathway is drastically affected. The wild-type precursor is still present, but a new type of D-alanine-ending precursor is also synthesized in large quantities, which results in a highly enhanced sensitivity to vancomycin.

A reverse phase high-pressure liquid chromatographic method to assay teicoplanin in serum is described. The procedure involves a single protein precipitation step with acetonitrile containing the internal standard mephenesin, followed by direct injection of the supernatant into the chromatograph. This HPLC method has good linearity, precision, recovery and sensitivity over the range of serum concentrations observed with the recommended dosages of the drug (5-50 mg/l). The assay has been validated by a correlation study with a bioassay on 97 sera obtained from patients treated with teicoplanin (r = 0.9519, P less than 0.001). The small serum sample size (100 microliters) and the use of a common C18 column make this assay ideal for drug monitoring, provided that HPLC equipment is available., Journal Article, SCOPUS: ar.j, info:eu-repo/semantics/published

A reverse phase high-pressure liquid chromatographic method to assay teicoplanin in serum is described. The procedure involves a single protein precipitation step with acetonitrile containing the internal standard mephenesin, followed by direct injection of the supernatant into the chromatograph. This HPLC method has good linearity, precision, recovery and sensitivity over the range of serum concentrations observed with the recommended dosages of the drug (5-50 mg/l). The assay has been validated by a correlation study with a bioassay on 97 sera obtained from patients treated with teicoplanin (r = 0.9519, P less than 0.001). The small serum sample size (100 microliters) and the use of a common C18 column make this assay ideal for drug monitoring, provided that HPLC equipment is available., Journal Article, SCOPUS: ar.j, info:eu-repo/semantics/published