Characterization of Extended-Spectrum β-Lactamase Genes of Shigella flexneri Isolates With Fosfomycin Resistance From Patients in China

BACKGROUND: The emergence of fosfomycin resistance and extended-spectrum β-lactamase (ESBL) genes is a serious threat to public health and a new challenge in shigellosis treatment. The purpose of this study was to identify fosfomycin resistance and characterize β-lactamase genes in fos-carrying isolates of Shigella flexneri from patients in China. METHODS: A total of 263 S. flexneri isolates were collected from 34 hospitals in the Anhui Province of China during September 2012-September 2015 and screened for fosA3, fosA, and fosC2 by PCR amplification and sequencing. The fos-carrying isolates were then screened for β-lactamase genes. The clonal relationships between fosA3-carrying isolates, the transmissibility of fosfomycin resistance, replicon types of plasmids carrying fosfomycin resistance genes and other associated resistance genes were investigated. RESULTS: Twenty-five of the 263 isolates (9.5%) showed resistance to fosfomycin, and 18 (6.8%) were positive for fosA3. None of the isolates was positive for fosA or fosC2. Seventeen of the isolates carrying fosA3 (94%) were CTX-M producers (seven CTX-M-55, five CTX-M-14, and five CTX-M-123), while three (16.7%) were TEM producers (TEM-1).Sixteen (88.9%) fosA3-carrying isolates exhibited multi-drug resistance. The replicon types of the 13 fosA3-carrying plasmids were IncF (n=13), IncHI2 (n=3), IncIl-Ir (n=2), and IncN (n=1). CONCLUSIONS: Our results indicated that fosA3 could spread through plasmids in S. flexneri isolates, along with the bla(CTX-M) and bla(TEM), which facilitate its quick dispersal. To the best of our knowledge, this is the first report of CTX-M-123-type ESBLs in S. flexneri isolates from patients in China.

Discovery of a Fluoroquinolone-Resistant Serratia marcescens Clinical Isolate without Quinolone Resistance-Determining Region Mutations

No abstract available.

Surveillance of Antimicrobial Susceptibility Patterns among Shigella Species Isolated in China during the 7-Year Period of 2005-2011

BACKGROUND: Shigella is a frequent cause of bacterial dysentery in the developing world. Treatment with antibiotics is recommended for shigellosis, but the options are limited due to globally emerging resistance. This study was conducted to determine the frequency and pattern of antimicrobial susceptibility of Shigella in China. METHODS: We studied the antimicrobial resistance profiles of 308 Shigella spp. strains (260 S. flexneri, 40 S. sonnei, 5 S. boydii, and 3 S. dysenteriae) isolated from fecal samples of patients (age, from 3 months to 92 yr) presenting with diarrhea in different districts of Anhui, China. The antimicrobial resistance of strains was determined by the agar dilution method according to the CSLI guidelines. RESULTS: The most common serogroup in the Shigella isolates was S. flexneri (n=260, 84.4%), followed by S. sonnei (n=40, 13.0%). The highest resistance rate was found for nalidixic acid (96.4%), followed by ampicillin (93.2%), tetracycline (90.9%), and trimethoprim/sulfamethoxazole (80.8%). Among the isolates tested, 280 (91.0%) were multidrug resistant (resistant to > or =2 agents). The most common resistance pattern was the combination of ampicillin, tetracycline, and trimethoprim/sulfamethoxazole (70.8%). Resistance to ampicillin and tetracycline were more common among S. flexneri than among S. sonnei isolates. CONCLUSIONS: S. flexneri is predominant in Anhui, China, and its higher antimicrobial resistance rate compared with that of S. sonnei is a cause for concern. Continuous monitoring of resistance patterns is necessary to control the spread of resistance in Shigella. The recommendations for antimicrobial treatment must be updated regularly based on surveillance results.

Distribution and resistance surveillance of 104 clinical strains of Serratia marcescens in Anhui Province / 中华传染病杂志

ObjectiveTo analyze the clinical distribution and antimicrobial resistance profile of Serratia marcescens(S. marcescens), and to provide the scientific evidence supporting clinical diagnosis and treatment.MethodsThe antimicrobial susceptibility test was performed in 104 strains of S. marcescens by agar dilution method. The results were judged according to the criteria recommended by Clinical and Laboratory Standards Institute (CLSI) 2010.The data were analyzed by chi square test. Results The majority of S. marcescens were isolated from sputum specimens,accounting for 59.6％ (62/104). The bacteria were most frequently isolated from department of respiratory (33.7％,35/104),followed by intensive care unit (23.1％,24/104),department of gerontology (16.3％, 17/104). The results of antimicrobial susceptibility test showed that the resistance rates of S.marcescens against ampicillin,gentamicin and cephazolin were high,which were 90.4％,86.5％ and 79.8％,respectively; those against the 3rd generation of cephalosporins were 24.0％-43.3％. No imipenem and meropenem resistant strains were identified. Compared with cefoxitin-resistant strains,the resistance rates of non-cefoxitin resistant strains against piperacillin (82.9％ vs 28.6％),ceftazidime (63.4％ vs 9.5％),aztreonam (68.3％ vs 9.5％),amikacin (68.3％ vs 20.6％),ciprofloxacin (48.8％ vs 19.1％) and chloramphenicol (90.3％ vs 58.7％) were all lower (all P ＜ 0.05 ). Conclusions S. marcescens is one of the most common conditional pathogenic bacteria leading to nosocomial infections,which is resistant to many kinds of antimicrobial agents.The surveillance of antimicrobial resistance in S. marcescens should be strengthened for purpose of preventing the transmission of multidrug resistant strains.

Chromosome and plasmid-mediated quinolone resistance mechanism in clinical isolates of Serratia marcescens / 中华检验医学杂志

Objective To investigate the prevalence of plasmid-mediated quinolone resistance ( PMQR ) determinants [ qnr,aac ( 6' ) -Ib-cr and qepA ]and mutations in quinolone resistance-determining regions (QRDRs) of gyrA and parC and their association with fluoroquinolone susceptibility in clinical isolates of Serratia marcescens in Anhui.Methods The minimum inhibition concentration ( MIC ) of 104 strains of S.rnarcescens collected from various clinical specimens from 34 hospitals during 2005 to 2010 were determined by agar dilution method.The qnr,aac (6')-Ib,qepA,gyrA and parC genes were screened by polymerase chain reaction (PCR) in 31 strains resistant to ciprofloxacin,and positive results were subsequently confirmed by sequencing.The conjugation experiments were performed for qnr and aac(6')-Ib-cr positive strains.The MIC of S.marcescens isolates,recipient strains and conjugants were tested by agar dilution method for quinolones and other antimicrobial agents.Results Six strains of the 31 S.marcescens isolates harboured qnr and/or aac(6')-Ib-cr genes.Among those 6 strains,2 strains harboured a qnrB6 gene,1 harboured a qnrS2 gene,and 4 harboured aac( 6' ) -Ib-cr,whereas no qnrA-,qnrC- or qnrD-positive isolate was detected.None of the 31 isolates carried the qepA gene.Mutations in the QRDR of gyrA and parC genes were detected in 9 and 7 isolates,respectively.The conjugation experiments were successfully carried out in 5 isolates of 6 PMQR determinants-postive strains.The MIC of conjugants for quinolones were increased evidently compared to recipient strains.Conclusions Chromosome and plasmid-mediated resistance determinants play an important role in quinolone resistance in clinical isolates of S.marcescens.And more important is that the PMQR determinants can be horizontal transmitted.It is necessary to continuously survey and watch for the spread of PMQR in S.marcescens in public health control program.