Plasmid-mediated AmpC Β-lactamase Research Articles

β-Lactamases in amoxicillin-clavulanate–resistant Escherichia coli strains isolated from a Chinese tertiary hospital

A total of 52 strains were resistant to amoxicillin-clavulanate by disk diffusion method in a Chinese tertiary hospital from July 2011 to December 2011. Among these isolates, 2 isolates possessed a phenotype consistent with production of inhibitor-resistant temoniera (TEM) (IRT) β-lactamase, and the TEM-type gene was cloned into strains of Escherichia coli JM109 cells. Both had no blaTEM mutations and were identified as TEM-1 β-lactamase producers. As a result, no IRT β-lactamase was detected. Multiplex PCR detected most of these strains produced TEM-1 enzymes, and plasmid-mediated AmpC β-lactamase and oxacillinase-1 β-lactamases are important mechanisms of resistance as well.

Prevalence and types of extended spectrum β-lactamases among urinary Escherichia coli isolates in Moroccan community

This study was designed to characterize extended-spectrum-β-lactamases (ESBL) produced by Escherichia coli isolates causing community urinary tract infections over a 2-year period (2010 and 2011) in a Moroccan large geographical region. Molecular characterization was done by using PCR and sequencing of the β-lactamases genes and plasmid-mediated quinolone resistance determinants. Among 1174 isolates, 49 (4.1%) were ESBL producers. The blaCTx-M-15 (n = 31) was the most frequent ESBL gene detected, followed by blaCTx-M-1 (n = 5), blaSHV-12 (n = 6), blaPER-2 (n = 3), then blaTEM-3, blaTEM-20, blaTEM-158, blaSHV-27, blaSHV-28, blaSHV-36, blaSHV-125, blaCTx-M-14 and blaCTx-M-27 with one isolate for each. The non-ESBL genes detected were blaTEM-70 (n = 1), blaTEM-176 (n = 1), blaTEM-104 (n = 6), blaTEM-1 (n = 15) and blaOxA-1 (n = 12). Plasmid mediated AmpC β-lactamases genes; blaACT-5 (n = 1), blaDHA-1(n = 2) and blaCMY-2 (n = 4) were detected in seven isolates (14.2%). The blaOxA-48 (n = 1) and blaIMP-1 (n = 1) carbapenemases genes were detected among five carbapenem-resistant E. coli. Five isolates (10.2%) harboured qnr genes, qnrB1 (n = 3), qnrB2 (n = 1) and qnrS1 (n = 1) type were detected. Thirty isolates (61.2%) were positive for aac(6′)-Ib-cr gene. The class 1 integron was detected in twenty two (44.8%) isolates. Phylogenetic grouping revealed that 22 (44.8%) isolates belonged to group A, while 15 (30.6%), 11 (22.4%) and 1 (2%) belonged to B2, D and B1. Results of conjugation experiments indicated that blaCTx-M-15, blaTEM-1, blaOxA-1, aac(6′)-Ib-cr and qnrB1 genes were co-transferred and that these genes were carried by a conjugative plasmid of high molecular weight. The results of this work reports the genetic diversity of ESBL genes, with the CTX-M-15 enzyme being the most common among ESBL-producing E. coli in Moroccan community.

Detection of extended-spectrum and plasmid-mediated AmpC β-lactamases in nosocomial Klebsiella isolates

Objective: The coexistence of enzymes in the same Klebsiella strain may result in false-negative tests for the detection of ESBLs as pAmpCs resist inhibition by clavulanic acid so masking ESBL presence. This study was to highlight the detection rates of ESBLs and pAmpCs by using phenotypic method; MAST 4-disc test and multiplex polymerase chain reaction (PCR) method. In addition, it aimed to evaluate the sensitivity of the phenotypic method in detection of these enzymes. Methods: Klebsiella isolates were collected from clinical samples in different wards in Zagazig University Hospitals. The antibiogram of these bacteria was determined by disc diffusion method. The presence of ESBLs and pAmpCs within the isolates was determined using the phenotypic MAST 4-disc test followed by a multiplex PCR method. Results: In total, 38 Klebsiella pneumoniae strains were evaluated. Among these isolates, 65.8% were ESBL producers, 2.6% were pAmpC producers, and 31.6% were neither ESBL nor pAmpC producers. The most frequent genotype of ESBL was SHV (84%); followed by TEM (44%) pAmpC producers were of DHA genotype. The distribution of different ESBL genotypes was SHV (84%), TEM (44%), CTX-M II genotype (28%) and followed by SHV and CTX-M IV genotype (24%). Using multiplex PCR as a reference method, MAST 4-disc test was of 92% sensitivity and 86.7% specificity. Conclusion: A rising alarm of ESBL producing strains among K. pneumoniae isolates. The exact detection of ESBLs in isolates that produce both enzymes is important for both treatment and epidemiology.

Enterobacteriaceae that Produce Extended-spectrum β-lactamases and AmpC β-lactamases in the Community: The Tip of the Iceberg?

Escherichia coli remains one of the most frequent causes of nosocomial and community-acquired bacterial infections including urinary tract infections, enteric infections, and systemic infections in humans. Extra-intestinal pathogenic E. coli or ExPEC had emerged during the 2000s as an important player in the resistance to antibiotics, especially to the cephalosporins and fluoroquinolones. Most importantly among ExPEC, is the increasing recognition of isolates producing "newer β-lactamases" that consist of plasmidmediated AmpC β-lactamases (e.g. CMY), extended-spectrum β-lactamases (e.g. CTX-M), and carbapenemases (e.g. NDM, KPC and OXA-48). Since the mid 2000's, E. coli that produce CTX-M enzymes (especially CTX-M-15), have emerged worldwide as important causes of community-associated urinary tract (UTIs) and blood stream infections. Community-associated acquisition and infections due to enterobacteria with plasmid-mediated AmpC β-lactamases are a relatively recent phenomenon and have been described in Canada and USA. Empiric antibiotic coverage for these resistant organisms should be considered in community patients presenting with sepsis involving the urinary tract especially if a patient recently traveled to a high-risk area. If this emerging public health threat is ignored, it is possible that the medical community may be forced in the near future to use the carbapenems as the first choice for the empirical treatment of serious infections associated with urinary tract infections originating from the community.

Detection of Gram-Negative β-Lactamase Producing Pathogens in the Clinical Lab

Pathogens that produce extended spectrum β-lactamases (ESBLs), plasmid-mediated AmpC β-lactamases, and carbapenemases may appear falsely susceptible to β-lactam antibiotics in the laboratory. Infected patients may be treated with inappropriate antibiotics if laboratories do not perform accurate tests to detect these resistance mechanisms. Furthermore the resistant pathogens may spread undetected to amplify the therapeutic and infection control challenge. This review makes a case for why and how laboratories should perform tests to detect β-lactamase-mediated resistance in gram-negative pathogens.

Prevalence and Epidemiological Relationship of CMY-2 AmpC β-Lactamase and CTX-M Extended-Spectrum β-Lactamase-Producing <i>Escherichia coli</i> Isolates from Broiler Farms in Japan

To evaluate the prevalence of extended-spectrum cephalosporin (ESC)-resistant Enterobacteriaceae in broiler chickens, 41 rectal samples taken from 4 commercial farms were examined. Desoxycholate hydrogen sulfide lactose agars, supplemented with either 4 μg/ml cefotaxime or 16 μg/ml ceftazidime, were used to screen ESC-resistant bacteria. ESC-resistant bacteria were isolated from all samples. Of the 164 ESC-resistant bacteria (included 4 isolates per a sample), 163 were Escherichia coli, while 1 isolate was identified as Enterobacter cloacae. Extended-spectrum β-lactamase (ESBL) genes and plasmid-mediated AmpC β-lactamase genes in the isolates were determined by PCR and sequencing. One AmpC β-lactamase gene, bla(CMY-2) (66%), and 4 ESBL genes, bla(CTX-M-1) (26%), bla(CTX-M-55) (10%), bla(SHV-5) (4%) and bla(CTX-M-2) (3%), were detected in the E. coli isolates. The epidemiological relationship of the CMY-2 and CTX-M β-lactamase-producing isolates among the farms was analyzed by pulsed-field gel electrophoresis using the XbaI restriction enzyme. Forty-one (Y1-Y41) and 14 (X1-X14) clusters were found in the CMY-2 and CTX-M-carrying E. coli isolates, respectively. Some clusters included isolates derived from more than 1 farm, indicating some cross-contamination of clonal strains and spread of CMY-2 AmpC β-lactamase or CTX-M ESBL among the farms.

Detection of plasmid-mediated AmpC β-lactamase in Escherichia coli and Klebsiella pneumoniae

Background: Detecting plasmid-mediated AmpC (pAmpC) β-lactamase-producing organism is important for optimal infection control and providing accurate and effective treatment option for physicians. Objectives: The aim of this study was to investigate the prevalence of pAmpC β-lactamase and compare the results of boronic acid (BA) disk test with other phenotypic tests detecting AmpC positive isolates. Materials and Methods: A total of 273 clinical isolates of Klebsiella pneumoniae (n: 82) and Escherichia coli (n: 191) were analysed. The presence of pAmpC β-lactamase was determined by BA disk test, cefoxitin (FOX) screening test, modified three dimensional test (M3DT), and multiplex polymerase chain reaction (PCR). Pulsed-field gel electrophoresis was performed to evaluate the genetic similarities between isolates. To detect extended spectrum β-lactamases (ESBL) in the presence of AmpC β-lactamase, ESBL confirmation test was carried out with and without BA solution. Results: Of the 273 strains tested, 127 strains were found FOX resistant, 114 were positive by M3DT, 108 were positive in BA disk test, and the multiplex PCR detected 24 pAmpC β-lactamase-positive isolate. The prevalence of AmpC-producing strains was 10.9% in E. coli and 3.6% in K. pneumoniae in the tested population by PCR. CIT and MOX group genes were predominant type in these strains. Conclusion: These results emphasize that clinical laboratories should consider testing the presence of pAmpC enzymes particularly in FOX-resistant isolates, and BA disk test will improve detection of this emerging resistance phenotype.

Identification of ACT-1 Plasmid-Mediated AmpC β-Lactamase Producing Citrobacter freundii from a Chinese Patient

Identification of ACT-1 Plasmid-Mediated AmpC β-Lactamase Producing Citrobacter freundii from a Chinese Patient

Study on drug resistance of Pseudomonas aeruginosa plasmid-mediated AmpC β-lactamase

The aim of the present study was to investigate the resistance of plasmid-mediated AmpC β-lactamase in Pseudomonas aeruginosa, to detect and identify the AmpC genotype and to provide evidence for antibiotic applications in the clinic. Resistance phenotype in 108 strains of clinically isolated P. aeruginosa was determined by Kirby-Bauer disk test and cefoxitin three dimensional test in AmpC-positive strains. Plasmids were extracted from AmpC-positive strains using the SDS-alkali splitting technique. The depurated plasmid was used to amplify AmpC β-lactamase genes by PCR. Positive PCR products were sequenced by the Shanghai Sangon Biological Engineering Technology Company. Gene homology of PCR products with other index sample gene sequences was compared. In the present study, 28 AmpC enzyme-positive P. aeruginosa strains among 108 were identified. Multidrug‑resistance to antibiotics was observed in positive AmpC P. aeruginosa strains and a new P. aeruginosa strain of plasmid-mediated CMY-7 type AmpC enzyme was identified. In addition, AmpC type β-lactamases were revealed to be important in the resistance mechanism to antibiotics in P. aeruginosa. This is the first report of CMY-7 plasmid‑mediated AmpC enzyme expression in P. aeruginosa.

Enterobacteriaceae that Produce Extended-spectrum β -lactamases and AmpC β -lactamases in the Community: The Tip of the Iceberg?

Escherichia coli remains one of the most frequent causes of nosocomial and community-acquired bacterial infections including urinary tract infections, enteric infections, and systemic infections in humans. Extra-intestinal pathogenic E. coli or ExPEC had emerged during the 2000s as an important player in the resistance to antibiotics, especially to the cephalosporins and fluoroquinolones. Most importantly among ExPEC, is the increasing recognition of isolates producing “newer β-lactamases” that consist of plasmidmediated AmpC β-lactamases (e.g. CMY), extended-spectrum β-lactamases (e.g. CTX-M), and carbapenemases (e.g. NDM, KPC and OXA-48). Since the mid 2000’s, E. coli that produce CTX-M enzymes (especially CTX-M-15), have emerged worldwide as important causes of community-associated urinary tract (UTIs) and blood stream infections. Community-associated acquisition and infections due to enterobacteria with plasmid-mediated AmpC β-lactamases are a relatively recent phenomenon and have been described in Canada and USA. Empiric antibiotic coverage for these resistant organisms should be considered in community patients presenting with sepsis involving the urinary tract especially if a patient recently traveled to a high-risk area. If this emerging public health threat is ignored, it is possible that the medical community may be forced in the near future to use the carbapenems as the first choice for the empirical treatment of serious infections associated with urinary tract infections originating from the community. Keywords: Community-onset infections, extended-spectrum beta-lactamases, AmpC beta-lactamases

Enterobacteriaceae that Produce Extended-spectrum β -lactamases and AmpC β -lactamases in the Community: The Tip of the Iceberg?

Escherichia coli remains one of the most frequent causes of nosocomial and community-acquired bacterial infections including urinary tract infections, enteric infections, and systemic infections in humans. Extra-intestinal pathogenic E. coli or ExPEC had emerged during the 2000s as an important player in the resistance to antibiotics, especially to the cephalosporins and fluoroquinolones. Most importantly among ExPEC, is the increasing recognition of isolates producing "newer β-lactamases" that consist of plasmidmediated AmpC β-lactamases (e.g. CMY), extended-spectrum β-lactamases (e.g. CTX-M), and carbapenemases (e.g. NDM, KPC and OXA-48). Since the mid 2000's, E. coli that produce CTX-M enzymes (especially CTX-M-15), have emerged worldwide as important causes of community-associated urinary tract (UTIs) and blood stream infections. Community-associated acquisition and infections due to enterobacteria with plasmid-mediated AmpC β-lactamases are a relatively recent phenomenon and have been described in Canada and USA. Empiric antibiotic coverage for these resistant organisms should be considered in community patients presenting with sepsis involving the urinary tract especially if a patient recently traveled to a high-risk area. If this emerging public health threat is ignored, it is possible that the medical community may be forced in the near future to use the carbapenems as the first choice for the empirical treatment of serious infections associated with urinary tract infections originating from the community.

Detection of Gram-Negative β-Lactamase Producing Pathogens in the Clinical Lab

Pathogens that produce extended spectrum β-lactamases (ESBLs), plasmid-mediated AmpC β-lactamases, and carbapenemases may appear falsely susceptible to β-lactam antibiotics in the laboratory. Infected patients may be treated with inappropriate antibiotics if laboratories do not perform accurate tests to detect these resistance mechanisms. Furthermore the resistant pathogens may spread undetected to amplify the therapeutic and infection control challenge. This review makes a case for why and how laboratories should perform tests to detect β-lactamase-mediated resistance in gram-negative pathogens.

Detection of Gram-Negative β-Lactamase Producing Pathogens in the Clinical Lab

Pathogens that produce extended spectrum β-lactamases (ESBLs), plasmid-mediated AmpC β-lactamases, and carbapenemases may appear falsely susceptible to β-lactam antibiotics in the laboratory. Infected patients may be treated with inappropriate antibiotics if laboratories do not perform accurate tests to detect these resistance mechanisms. Furthermore the resistant pathogens may spread undetected to amplify the therapeutic and infection control challenge. This review makes a case for why and how laboratories should perform tests to detect β-lactamase-mediated resistance in gram-negative pathogens.

Prevalence and genotypic analysis of plasmid-mediated β-lactamases among urinary Klebsiella pneumoniae isolates in Moroccan community

The aim of this study is to assess the prevalence and molecular characterization of the extended spectrum β-lactamases (ESBL)-producing Klebsiella pneumoniae isolated from community acquired urinary tract infections and collected in five Moroccan cities during a 2010 survey. In all, 34 (7.5%) of the 453 K. pneumoniae isolates studied were positive for an ESBL phenotype and 91.1% of these isolates were multidrug resistant. The bla(CTX-M-15) (n=31) was the most frequent ESBL genes detected, followed equally by bla(SHV-28) and bla(SHV-12) (n=3), then bla(TEM-3), bla(SHV-36), bla(SHV-110) and bla(CTX-M-1) with one isolate for each (n=1). Eight isolates co-expressed more than one ESBL with bla(CTX-M-15). The non-ESBL genes detected were bla(SHV-1), bla(SHV-11), bla(SHV-32), bla(SHV-26), bla(SHV-76), bla(TEM-1), bla(TEM-1b) and bla(OXA-1). Plasmid-mediated AmpC β-lactamase genes, bla(ACT-2), bla(DHA-1) and a new β-lacatamase named bla(EBC-1464), were detected in 11.7% of isolates. Fourteen (41.1%) isolates harbored qnr genes; qnrA6 (n=1), qnrB1 (n=8), qnrB2 (n=1) and qnrS1 (n=4) types were detected. Twenty-six isolates (76.4%) were positive for aac(6')-Ib-cr gene. Results of conjugation experiments indicated that bla(CTX-M-15), bla(TEM-1b), bla(OXA-1), aac(6')-Ib-cr and qnrB1 genes were co-transferred and that these genes were carried by a conjugative plasmid of high molecular weight. With the exception of qnrB1, all the antibiotic resistance genes were clustered in a 12-kb region. The results of this work report the genetic diversity of ESBL genes, with the CTX-M-15 enzyme being most common among ESBL-producing K. pneumoniae in Moroccan community. Furthermore, a major finding is that bla(EBC-1464) detection is a first in Morocco.

Extraintestinal pathogenic Escherichia coli: an update on antimicrobial resistance, laboratory diagnosis and treatment

Escherichia coli remains one of the most frequent causes of nosocomial and community-acquired bacterial infections including urinary tract infections, enteric infections and systemic infections in humans. Extraintestinal pathogenic E. coli (ExPEC) had emerged during the 2000s as an important player in the resistance to antibiotics, especially to the cephalosporins and fluoroquinolones. Most importantly, among ExPEC is the increasing recognition of isolates producing ‘newer β-lactamases’ that consist of plasmid-mediated AmpC β-lactamases (e.g., CMY), extended-spectrum β-lactamases (e.g., CTX-M) and carbapenemases (e.g., New Delhi metallo-β-lactamase, Klebsiella pneumonaie carbapenemase and OXA-48). This review will highlight recent aspects on antimicrobial resistance in ExPEC, including the laboratory detection of these isolates, and describe some treatment options for infections due to antimicrobial-resistant isolates.

Clinical significance of infections caused by plasmid-mediated AmpC β-lactamases and extended-spectrum β-lactamase-producing Escherichia coli

Escherichia coli frequently causes both nosocomial and community-acquired infections, and antimicrobial resistance in E. coli is a growing problem worldwide. Resistance to broad-spectrum antibiotics in E. coli is often mediated by the production of extended-spectrum b-lactamases (ESBLs) [1]. In recent years, some E. coli strains have been isolated that harbor plasmid-mediated AmpC genes imported from other Enterobacteriaceae carrying chromosomal AmpC genes, such as Citrobacter freundii, Enterobacter cloacae, and Aeromonas species [2]. Recent studies on plasmid-mediated AmpC b-lactamase (PAB)producing E. coli have shown only the prevalence of PAB [3–6]. Furthermore, most previous studies regarding PABproducing E. coli have involved all clinical isolates, including colonized pathogens [1, 4–6]. Thus, we investigated the clinical features and clinical outcomes of patients with PAB-producing E. coli bacteremia. Also, we conducted this study in order to delineate the differences in the clinical manifestations and outcome of E. coli bacteremia between ESBL and non-ESBL groups, and to evaluate the impact of ESBL-producing organisms on outcome in E. coli bacteremia. We reviewed the medical records of individuals diagnosed with E. coli bacteremia from July 2006 to August 2007 at Samsung Medical Center, Seoul, Republic of Korea, a 1,950-bed tertiary-care university hospital. Patients were included in the study if their blood culture results were positive for E. coli. Only the first bacteremic episode for each patient was included in this study. E. coli bacteremia was defined as a growth of E. coli in a blood culture specimen. Nosocomial infection was defined as an infection that occurred [72 h after admission to the hospital. Community-onset infections occurring B72 h after admission were further classified as healthcare-associated if any of the established criteria were present [7]. We considered antimicrobial therapy to be inappropriate if the drugs used did not have in vitro activity against the isolates or if the patient did not receive antimicrobial therapy. The bacterial isolates were obtained from the Asian Bacterial Bank (ABB) of the Asia Pacific Foundation for Infectious Disease (APFID). In vitro antimicrobial susceptibility testing of the isolates was performed in Mueller–Hinton broth (Becton–Dickinson, Sparks, MD) by the broth microdilution method in accordance with the guidelines established by the Clinical and Laboratory Standards Institute (CLSI). Isolates with resistance to cefoxitin were considered to be positive for AmpC b-lactamase. Cefoxitin-positive isolates were further tested using the previously described polymerase chain reaction (PCR) primers and conditions [6]. ESBL production was confirmed in screening-positive isolates via a double-disk synergy test using BD BBL Sensi-Disc (Becton–Dickinson). Doubledisk synergy test-positive isolates were further tested by PCR and sequence analyses to determine the gene This study was presented, in part, at the 49th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), San Francisco, CA, USA, September 2009 (abstract 2413).

Prevalence of plasmid-mediated AmpC β-lactamase-producing Escherichia coli and spread of the ST131 clone among extended-spectrum β-lactamase-producing E. coli in Japan

In 2010, a total of 1327 clinical Escherichia coli isolates from five hospitals in the Kyoto and Shiga regions of Japan were analysed by PCR. The prevalences of plasmid-mediated AmpC β-lactamase (pAmpC)-producers, extended-spectrum β-lactamase (ESBL)-producers and co-producers of pAmpC and ESBL were 1.7%, 9.7% and 0.3%, respectively. Less than one-half of the pAmpC-producers were reported to be resistant to third-generation cephalosporins, cephamycins and β-lactam/β-lactam inhibitors using the old 2009 Clinical and Laboratory Standards Institute (CLSI) breakpoints. CMY-2 was the most prevalent pAmpC type (95%), and CTX-M-14 (38%), CTX-M-15 (26%) and CTX-M-27 (19%) were the most prevalent ESBL types. The worldwide O25b-ST131-B2 clone accounted for 11% of pAmpC-producers and 41% of ESBL-producers. The O25b-ST131-B2 clone was characterised by a CTX-M-27- or CTX-M-15-type ESBL and ciprofloxacin-non-susceptibility with quadruple mutations in the quinolone resistance-determining regions (S83L and D87N in GyrA and S80I and E84V in ParC). A significant proportion of pAmpC-producers and the O25b-ST131-B2 clone were found in Japan by a recent regional surveillance programme.

Imipenem Resistance inKlebsiella pneumoniaeIs Associated to the Combination of Plasmid-Mediated CMY-4 AmpC β-Lactamase and Loss of an Outer Membrane Protein

This study was conducted to identify the molecular mechanisms of imipenem resistance in a Klebsiella pneumoniae (Kp16137) isolate recovered in August 2008 at the University Hospital Sahloul, Sousse, Tunisia. The strain was identified with the API 20E system; antibiotic-containing disks were used for detection of antibiotic susceptibility by a disk diffusion assay. We investigated the presence of β-lactamases by PCR, using specific primers for bla(TEM), bla(SHV), bla(CTX-M), bla(OXA), bla(CMY), bla(ACC), bla(FOX), bla(IMP), bla(KPC), bla(VIM), and by sequencing. Extraction of plasmid DNA from Kp16137 and the transconjugant was performed by the method of Kado. Southern transfer was performed on nylon. The membrane was hybridized with a specific probe for the bla(CMY-2) gene. Outer membrane proteins were isolated and were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis on 12% polyacrylamide gel. K. pneumoniae Kp16137 was resistant to all available β-lactams, including third generation cephalosporins and carbapenems. The screening of β-lactamases showed the presence of three β-lactamases: TEM-1, SHV-61, and CMY-4. The CMY-4 β-lactamase was located on an 80-kb plasmid. An analysis of the outer membrane proteins of this isolate revealed that it lacked a porin of 42 kDa. The loss of this outer membrane protein band correlated with imipenem resistance in this strain. In K. pneumoniae 16137, synthesis of a plasmid-mediated β-lactamase: AmpC CMY-4, together with alteration in permeability led to resistance to all available β-lactams and carbapenems.

CMY-2-Producing Escherichia coli in the Nose of Pigs

The spread of extended-spectrum cephalosporin-resistant (ESC-R) Escherichia coli isolates represents a public health concern. Extended-spectrum β-lactamases (ESBLs) or plasmid-mediated AmpC β-lactamases (pAmpCs) are the most frequently encountered mechanisms responsible for this phenomenon ([10][1

Plasmid-Mediated Quinolone Resistance in Extended-Spectrum-β-Lactamase- and AmpC β-Lactamase-Producing Serratia marcescens in China

We investigated the prevalence of plasmid-mediated quinolone resistance (PMQR) determinants and examined the association of these determinants with extended-spectrum β-lactamases (ESBLs) and/or plasmid-mediated AmpC β-lactamases (pAmpCs) in Serratia marcescens isolates in China. In this study, the presence of PMQR determinants was significantly related to the coproduction of ESBLs and/or pAmpCs (CTX-M-14, SHV-5, DHA-1, and ACT-1), among which CTX-M-14 was the most common gene type.