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OXA-232 carbapenemase, being a vital resistance mechanism against carbapenems, has recently been increasingly reported. In China, the identified OXA-232-producing K. pneumoniae isolates almost belonged to ST15 and were not hypervirulent, despite harboring a virulence plasmid.

Carbapenemase-producing Enterobacteriaceae (CPE) isolates are recognized as one of the most severe threats to public health. However, the population structure and genetic characteristics of CPE isolates among bloodstream infections (BSIs) are largely unknown. To address this knowledge gap, in this study, we included patients with clinically significant BSIs due to Enterobacterales isolates, recruited from 26 sentinel hospitals in China (2014–2015). CPE isolates were microbiologically and genomically characterized, including their susceptibility profiles, molecular typing, phylogenetic features, and genetic context analysis of carbapenemase-encoding genes. Of the 2569 BSI Enterobacterales isolates enrolled, 42 (1.6%) were carbapenemase-positive. Moreover, among the 2242 investigated isolates, 1111 (49.6%) extended-spectrum β-lactamase (ESBL)-producing isolates were identified in Escherichia (E.) coli, Klebsiella (K.) pneumoniae, Proteus (P.) mirabilis, and K. oxytoca. Whole genome sequencing analysis showed the clonal spread of K. pneumoniae carbapenemase (KPC)-2-producing K. pneumoniae sequence type 11 (ST11) and New Delhi metallo-β-lactamase (NDM)-5-producing E. coli ST167 in our collection. Plasmid analysis revealed that carbapenemase-encoding genes were located on multiple plasmids. A high prevalence of biofilm-encoding type 3 fimbriae clusters and yesiniabactin-associated genes was observed in K. pneumoniae isolates. This work demonstrates the high prevalence of ESBLs and the wide dissemination of CPE among BSI isolates in China, which represent real clinical threats. Moreover, our findings first illustrate a more comprehensive genome scenario of CPE isolates among BSIs. The clonal spread of KPC-2-producing K. pneumoniae ST11 and NDM-5-producing E. coli ST167 needs to be closely monitored.

There is a paucity of published data to evaluate the efficacy and safety of imipenem, cefepime and piperacillin/tazobactam dosing regimens against bloodstream infections caused by Klebsiella aerogenes (BSIs-Kae) and Enterobacter cloacae complex (BSIs-Ecc) in patients with various degrees of renal function.Pathogens were isolated from China's blood bacterial resistant investigation network. The dosing regimens of imipenem, cefepime and piperacillin were simulated with intermittent infusion and extended infusion. Monte Carlo simulation was performed to calculate the probability of target attainment and a cumulative fraction of response (CFR) against BSIs-Kae/Ecc.In total, 203 BSIs-Kae, and 785 BSIs-Ecc were isolated from the surveillance network. Imipenem showed the highest in vitro activity against BSIs-Kae/Ecc, followed by cefepime (85%) and piperacillin/tazobactam (70-80%). The MICCefepime, not piperacillin/tazobactam, can be a reasonable carbapenem-sparing option in empirically treating BSIs-Kae/Ecc.

Objectives: Monte Carlo simulation (MCS) was used to evaluate optimal dosage for cefepime (FEP), moxalactam (MOX), and cefperazone/sulbactam (CFZ/SBT) against extended-spectrum β-lactamase (ESBL) producers isolated from the Blood Bacterial Resistant Investigation Collaborative System. Methods: Minimum inhibitory concentration (MIC) was tested by agar dilution, and ESBL producers were identified by modified Clinical and Laboratory Standards Institute tests. Pharmacokinetic parameters were derived from data on healthy individuals, and probability of target attainment (PTA) and cumulative fraction of response (CFR) %fT >MIC values were estimated by MCS. Results: A total of 2032 Escherichia coli (875 ESBL-producing) and Klebsiella pneumoniae (157 ESBL-producing) strains, and 371 other Enterobacteriaceae strains, were isolated from patients with bloodstream infections (BSIs). MIC90 values for FEP, MOX, and CFZ/SBT against ESBL-producing E. coli and K. pneumoniae were 64/64 mg/L, 2/32 mg/L, and 64/128 mg/L, respectively. Conventional MOX and CFZ/SBT doses failed to reach 90% PTA against isolates with MICs ≥8 mg/L and ≥4 mg/L, respectively. Against ESBL producers, neither FEP nor CFZ/SBT achieved ≥90% CFR, while CFRs for MOX (1 g iv q6h, 2 g iv q12h, and 2 g iv q8h) exceeded 90% against ESBL-producing E. coli. Simulated CFRs for FEP and MOX were similar (>90%) against non-ESBL-producing Enterobacteriaceae, and higher than CFRs for CFZ/SBT. Conclusion: ESBL producers from BSIs were highly susceptible to MOX, and PTA values were generally higher for MOX than FEP or CFZ/SBT for conventional dosing regimens. This large MCS analysis shows that MOX but not FEP or CFZ/SBT can be used empirically to treat BSIs caused by ESBL-producing E. coli strains.

Background The aim of this study was to investigate the mechanism of Listeria monocytogenes (Lm) pathogenicity and resistance. In addition, the effect of existing treatment options against Lm were systematically evaluated. Methods Six Lm isolates were collected and antimicrobial susceptibility testing of 15 antibiotics were done. Subsequently, whole genome sequencing and bioinformatics analysis were performed. Biofilm formation was evaluated by crystal violet staining. Furthermore, the effect of meropenem, linezolid, penicillin, vancomycin, and trimethoprim/sulfamethoxazole were determined using the time-kill assay. Results Four sequence types (STs) were identified (ST1, ST3, ST87, ST451). Multivirulence-locus sequence typing results classified ST87 isolates into cluster. All isolates were resistant to fosfomycin and daptomycin with fosX and mprF. In addition, a total of 80 virulence genes were detected and 72 genes were found in all 6 isolates. Seven genes associated with hemolysin were found in 26530 and 115423. However, due to lack of one genomic island including virulence genes related to flagellar synthesis, isolate 115423 produced less biofilm than 5 other isolates. Although all isolates were susceptible to vancomycin, the in vitro time-kill assay showed that vancomycin monotherapy resulted in less than 2 log10 cerebrospinal fluid (CFU)/mL compared with the initial count. Trimethoprim/sulfamethoxazole at serum or CFU concentrations had bactericidal effect against tested Lm strains at 24 hours. Conclusions ST87 clone was a typical prevalent ST in clinical Lm isolates in China. Trimethoprim/sulfamethoxazole might be greater potential therapeutic option against Lm infections., The present study revealed ST87 clone was the predominant sequence type among clinical Listeria monocytogenes (Lm) isolates in China. Although all isolates were susceptible to vancomycin, the effect was still unsatisfactory. Trimethoprim/sulfamethoxazole was a potent option against Lm infections.

Xingbing Wu,1 Chen Huang,2 Hui Wang,2 Jinru Ji,3 Chaoqun Ying,3 Yonghong Xiao3 1Department of Infectious Disease, Ningbo Medical Center Lihuili Hospital, Ningbo, People’s Republic of China; 2Department of Respiratory Medicine, Ningbo Medical Center Lihuili Hospital, Ningbo, People’s Republic of China; 3State Key Laboratory for Diagnosis and Treatment of Infectious Disease, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, People’s Republic of ChinaCorrespondence: Chen HuangDepartment of Respiratory Medicine, Ningbo Medical Center Lihuili Hospital, Ningbo, 315000, People’s Republic of ChinaEmail drhchen@163.comYonghong XiaoState Key Laboratory for Diagnosis and Treatment of Infectious Diseases, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, 310003, People’s Republic of ChinaTel +865 718 723 6421Email xiao-yonghong@163.comBackground: Few pharmacodynamics studies to date have evaluated the efficacy and safety of polymyxin B (PMB) in treating patients with bloodstream infections (BSIs) in China.Methods: Patients with BSIs were identified using an antimicrobial surveillance network, and their pathogens were isolated. Patients were treated with a loading dose of PMB followed by either a weight-based or weight-independent maintenance dose. Monte Carlo simulation was utilized to calculate the probability of target attainment (PTA) and cumulative fraction of response (CFR) against Gram-negative organisms in patients with normal or decreased renal function.Results: A total of 10,066 Gram-negative organisms, including 5500 Escherichia coli (Eco), 2519 Klebsiella pneumoniae (Kpn), 501 Acinetobacter baumannii (Aba), were isolated from patients with BSIs. Although these strains were highly resistant to carbapenem, they remained susceptible to PMB. Among patients with renal impairment (mean CrCL, 42 mL/min), a PMB 2.5 mg/kg loading dose followed by a maintenance dose of 60 mg q12h reached ≥ 90% PTA against isolates with an MIC of 2 mg/L, with a low risk of toxicity. Among patients with normal renal function (mean CrCL, 123 mL/min), all simulated regimens showed PTAs of 25– 80%. A weight-based loading dose followed by either a weight-based or weight-independent maintenance dose showed a promising CFR, especially in patients with renal impairment, with CFRs ≥ 90% against carbapenem-resistant Eco, Kpn, and Aba. Simulated regimens showed a disappointing CFR (< 80%) against carbapenem-resistant Pae in patients with normal renal function. Based on the optimal balance of efficacy and toxicity, a fixed maintenance dose of 60 mg q12h among patients with renal impairment yielded a CFR similar to regimens based on total body weight and was associated with a probability of toxicity (12.5%) significantly lower than that of simulations based on total body weight. Among patients with normal renal function, a weight-based maintenance dose of 1.25 mg/kg q12h achieved a higher CFR than a fixed maintenance dose, without significantly increasing toxicity.Conclusion: A 2.5 mg/kg loading dose of PMB is optimal, regardless of renal function. A fixed maintenance dose of 60 mg q12h is recommended for empirical treatment of patients with renal impairment infected with Eco, Kpn, and Aba, whereas a weight-based maintenance dose of 1.25 mg/kg is recommended for patients with normal renal function.Keywords: polymyxin B, carbapenem-resistant gram-negative organisms, bloodstream infection, Monte Carlo, toxicity

Objectives Although blaNDM-1 has been widely detected in various Enterobacteriaceae clinical isolates, multiple blaNDM-1 colonisations within the same patient remain rare. The aim of the study was to describe a patient with respiratory tract colonisation with NDM-1-producing Escherichia coli and Citrobacter freundii during hospitalisation in China. Methods Two carbapenem-resistant isolates were analysed. Antimicrobial susceptibility testing, metallo-β-lactamase production, conjugation assay, plasmid analysis and molecular typing were performed. Results The two clinical isolates carried the blaNDM-1 gene and showed resistance to carbapenems. S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) revealed that E. coli NB753 harboured a plasmid of ca. 80 kb, and C. freundii NB865 harboured three plasmids (ca. 70, 80 and 135 kb). Southern blot and Inc replicon typing further demonstrated that both isolates carried the blaNDM-1 gene on a self-transferrable IncX3 plasmid. Moreover, the two NDM-producing plasmids were conjugative and the transconjugants showed increased resistance to carbapenems. Conclusion An NDM-1-encoding plasmid harboured by various clinical isolates in a single patient is worrying considering that this plasmid may be widespread in our hospital. Furthermore, the threat of carbapenemase-producing bacterial epidemics should be closely monitored. However, a limitation of this study was the extremely small sample size.

Table S1. Analysis of risk factors for 28â day mortality in 283 patients with ESBL- producing E. coli BSI. (DOCX 31 kb)

Figure S1. Kaplan-Meier survival estimates among non-transplant patients with BSIs caused by non-ESBL-producing E. coli and ESBL-producing E. coli. (A) Community-acquired infection. (B) Nosocomial-acquired infection. Figure S2. Kaplan-Meier 28 day survival estimates. (A) E. coli BSI patients (APACHE II score < 9) treated with carbapenem and β-lactam-β-lactamase inhibitor (BLBLI) combination antibiotics. (B) E. coli BSI patients (APACHE II score ≥ 9) treated with carbapenem and BLBLIs. (DOCX 122 kb)

Objectives: Monte Carlo simulation (MCS) was used to evaluate optimal dosage for cefepime (FEP), moxalactam (MOX), and cefperazone/sulbactam (CFZ/SBT) against extended-spectrum β-lactamase (ESBL) producers isolated from the Blood Bacterial Resistant Investigation Collaborative System. Methods: Minimum inhibitory concentration (MIC) was tested by agar dilution, and ESBL producers were identified by modified Clinical and Laboratory Standards Institute tests. Pharmacokinetic parameters were derived from data on healthy individuals, and probability of target attainment (PTA) and cumulative fraction of response (CFR) %fT >MIC values were estimated by MCS. Results: A total of 2032 Escherichia coli (875 ESBL-producing) and Klebsiella pneumoniae (157 ESBL-producing) strains, and 371 other Enterobacteriaceae strains, were isolated from patients with bloodstream infections (BSIs). MIC90 values for FEP, MOX, and CFZ/SBT against ESBL-producing E. coli and K. pneumoniae were 64/64 mg/L, 2/32 mg/L, and 64/128 mg/L, respectively. Conventional MOX and CFZ/SBT doses failed to reach 90% PTA against isolates with MICs ≥8 mg/L and ≥4 mg/L, respectively. Against ESBL producers, neither FEP nor CFZ/SBT achieved ≥90% CFR, while CFRs for MOX (1 g iv q6h, 2 g iv q12h, and 2 g iv q8h) exceeded 90% against ESBL-producing E. coli. Simulated CFRs for FEP and MOX were similar (>90%) against non-ESBL-producing Enterobacteriaceae, and higher than CFRs for CFZ/SBT. Conclusion: ESBL producers from BSIs were highly susceptible to MOX, and PTA values were generally higher for MOX than FEP or CFZ/SBT for conventional dosing regimens. This large MCS analysis shows that MOX but not FEP or CFZ/SBT can be used empirically to treat BSIs caused by ESBL-producing E. coli strains.

We report here the emergence of seven IMP-4-producing Raoultella ornithinolytica isolates obtained from one patient. All isolates carried the bla IMP-4 carbapenemase gene, five isolates also carried bla SHV-12 , four contained bla TEM-1 , and one contained bla OXA-1 . Notably, the R. ornithinolytica isolate Ro25724 also expressed Klebsiella pneumoniae carbapenemase (KPC)-2. The bla KPC-2 gene was located on a Tn 3 -Tn 4401 integration structure on a plasmid of ∼450 kb. This is the first description of the coexistence of bla KPC-2 and bla IMP-4 from the genus Raoultella .

Vibrio fluvialis is recognized as an emerging pathogen. However, not much is known about the mechanism of its pathogenesis, and its adaptation to a special niche such as the gall bladder. Here we describe two V. fluvialis strains that cause acute cholecystitis. It is noteworthy that both strains were susceptible to all antibiotics tested, which is in contrast to previous studies, suggesting substantial genetic diversity among V. fluvialis isolates. In agreement with their survival and growth in the gall bladder, the genomes of strains 12605 and 3663 contain a considerable number of genes that confer resistance to bile, including toxR, ompU, tolC, cmeABC, rlpB, yrbK, rpoS, damX and gltK. Furthermore, integrative and conjugative elements (ICEs), virulence factors and prophage regions were also detected in strains 12605 and 3663, reflecting their flexibility in recombination during the evolution of pathogenicity. Comparative analysis of nine available genomes of V. fluvialis revealed a core genome consisting of 3,147 genes. Our results highlight the association of V. fluvialis with a rare disease profile and shed light on the evolution of pathogenesis and niche adaptation of V. fluvialis.

Wei Yu,1,2,* Jinru Ji,1,* Tingting Xiao,1 Chaoqun Ying,1 Jiaheng Fang,3 Ping Shen,1 Yonghong Xiao1 1State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University, 2Department of Infectious Diseases, Zhejiang Provincial People’s Hospital, 3Department of Gastroenterology, Hang Zhou Normal University Affiliated Hospital, Hangzhou, People’s Republic of China *These authors contributed equally to this work Background: Dicloxacillin, a semisynthetic isoxazolyl penicillin, exhibits antimicrobial activity against a wide variety of Gram-positive bacteria, as well as stability against penicillinases and low level of toxicity. The objective of this study was to obtain optimal dosing regimen of oral administration of dicloxacillin by analyzing the pharmacokinetic (PK) index in healthy volunteers and in vitro antibacterial activity by using Monte Carlo simulation. Materials and methods: A total of 867 clinical isolates from community-onset infections were collected from 31 secondary hospitals in People’s Republic of China. The minimum inhibitory concentration (MIC) values of dicloxacillin were determined by the agar dilution method. Based on the MICs and the PK parameters of different dosage regimens, Monte Carlo simulation was performed to simulate the PK/pharmacodynamic indices of 250 mg once-daily (qd), 500 mgqd, 1,000 mg qd, 2,000 mg qd, 250 mg every 6 hours (q6h), and 500 mg q6h, respectively. The probability of target attainment was estimated at each MIC value, and the cumulative fraction of response (CFR) was calculated to evaluate the efficacy of these regimens. Results: Dicloxacillin showed poor antibacterial activity against Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae. Resistance to dicloxacillin was observed in 7.5% of coagulase-negative Staphylococcus (CNS) isolates and 9.2% of other Streptococcus isolates, whereas 1.5% of methicillin-sensitive Staphylococcus aureus (MSSA) was resistant to dicloxacillin. Multiple-dose regimens could obtain higher CFR than single-dose regimens against H. influenza and S. pneumoniae. However, all dosing regimens against MSSA achieved CFR ≥90%. Meanwhile, dosing regimen of 2,000 mg qd, 250 mg q6h, and 500 mg q6h could achieve >90% of CFR for CNS. For other Streptococcus isolates, multiple-dose regimens achieved CFR ≥90%. Conclusion: Dicloxacillin has a significant antibacterial activity against MSSA, CNS, and other Streptococcus isolates. The simulation results suggest that dicloxacillin 250 mg q6h and 500 mg q6h dosing regimens may be recommended for clinical applications, especially for community-onset infections. Keywords: pharmacokinetics, pharmacodynamics, PK/PD index, dosage regimens, MSSA, CNS

Infection after renal transplantation remains a major cause of morbidity and death, especially infection from the extensively drug-resistant bacteria, A. baumannii. A total of fourteen A. baumannii isolates were isolated from the donors’ preserved fluid from DCD (donation after cardiac death) renal transplantation and four isolates in the recipients’ draining liquid at the Kidney Disease Center, The First Affiliated Hospital, College of Medicine, Zhejiang University, from March 2013 to November 2014. An outbreak of A. baumannii emerging after DCD renal transplantation was tracked to understand the transmission of the pathogen. PFGE displayed similar DNA patterns between isolates from the same hospital. Antimicrobial susceptibility tests against thirteen antimicrobial agents were determined using the K-B diffusion method and eTest. Whole-genome sequencing was applied to investigate the genetic relationship of the isolates. With the clinical data and research results, we concluded that the A. baumannii isolates 3R1 and 3R2 was probably transmitted from the donor who acquired the bacteria during his stay in the ICU, while isolate 4R1 was transmitted from 3R1 and 3R2 via medical manipulation. This study demonstrated the value of integration of clinical profiles with molecular methods in outbreak investigation and their importance in controlling infection and preventing serious complications after DCD transplantation.

Objectives The evolution of infectious diseases (IDs) poses a challenge to many ID physicians, who must either adapt or transition to another career track. This national cross-sectional study assessed the current working conditions and problems faced by ID professionals in China. Methods A national questionnaire survey of ID physicians and their facilities throughout China was performed in May–June 2016 using stratified random sampling. Results A total of 156/300 (52.0%) ID departments and 1071/2250 (47.6%) physicians from 21 provinces participated in the survey. Overall, 151 (96.2%) of 156 hospitals had ID wards and 141 (90.4%) provided outpatient consultations. The average number of ID physicians per department was 10.32 ± 6.57. The ratio of patient beds to doctors was 5: 1, and the ratio of patient beds to nurses was 5: 1.85. Training in IDs was available in 126 (80.8%), and ID research was performed in 108 (69.2%), of the 156 departments. The main service provided by ID physicians was the management of legally notifiable communicable diseases. The annual income of 942 (88.0%) of the 1071 physicians was below $15 000. Of these physicians, 870 (81.2%) felt high or very high pressure in their work, whereas only 514 (48.0%) were satisfied or very satisfied with their jobs. Conclusions The limited medical service provided by ID physicians is poorly aligned with current healthcare demands. Moreover, the heavy workloads, high stress, poor compensation and limited career prospects for ID physicians in China impede the continued development of specialists and places them in a career dilemma. ID physicians should work to develop and diversify the field and to enhance their capacities by learning new technologies and collaborating with other medical disciplines.

Background Shigellosis is the most common cause of gastrointestinal infections in developing countries. In China, the species most frequently responsible for shigellosis is Shigella flexneri. S. flexneri remains largely unexplored from a genomic standpoint and is still described using a vocabulary based on biochemical and serological properties. Moreover, increasing numbers of ESBL-producing Shigella strains have been isolated from clinical samples. Despite this, only a few cases of ESBL-producing Shigella have been described in China. Therefore, a better understanding of ESBL-producing Shigella from a genomic standpoint is required. In this study, a S. flexneri type 1a isolate SP1 harboring blaCTX-M-14, which was recovered from the patient with diarrhea, was subjected to whole genome sequencing. Results The draft genome assembly of S. flexneri strain SP1 consisted of 4,592,345 bp with a G+C content of 50.46%. RAST analysis revealed the genome contained 4798 coding sequences (CDSs) and 100 RNA-encoding genes. We detected one incomplete prophage and six candidate CRISPR loci in the genome. In vitro antimicrobial susceptibility testing demonstrated that strain SP1 is resistant to ampicillin, amoxicillin/clavulanic acid, cefazolin, ceftriaxone and trimethoprim. In silico analysis detected genes mediating resistance to aminoglycosides, β-lactams, phenicol, tetracycline, sulphonamides, and trimethoprim. The bla CTX-M-14 gene was located on an IncFII2 plasmid. A series of virulence factors were identified in the genome. Conclusions In this study, we report the whole genome sequence of a blaCTX-M-14-encoding S. flexneri strain SP1. Dozens of resistance determinants were detected in the genome and may be responsible for the multidrug-resistance of this strain, although further confirmation studies are warranted. Numerous virulence factors identified in the strain suggest that isolate SP1 is potential pathogenic. The availability of the genome sequence and comparative analysis with other S. flexneri strains provides the basis to further address the evolution of drug resistance mechanisms and pathogenicity in S. flexneri. Electronic supplementary material The online version of this article (doi:10.1186/s12941-017-0212-2) contains supplementary material, which is available to authorized users.

Additional file 2: Table S2. Antimicrobial susceptibility profile of S. flexneri SP1 recovered from a patient with diarrhea.