ABSTRACT
Escherichia coli recovered from three hospitals in Barcelona (Spain) were studied to determine the prevalence of isolates with acquired AmpC (ac-AmpC) and/or overproduced chromosomal AmpC (c-AmpC). Mechanisms involved in blac-AmpC overexpression, blaac-AmpC and the plasmids associated with their distribution as well as the prevalence of plasmid-mediated quinolone resistance (PMQR) in AmpC-producing isolates were also determined. Isolates were selected according to their resistance phenotype. blaac-AmpC, alterations in the blac-AmpC promoter/attenuator, and PMQR genes [qnrA, qnrB, qnrS, aac(6')-Ib-cr and qepA] were characterised by PCR and sequencing. blac-AmpC expression was determined by qRT-PCR. Population structure analysis was performed using PFGE, MLST and phylogenetic group PCR. Plasmids carrying blaac-AmpC were characterised by PCR-based replicon typing and S1-PFGE. IncI1 and IncF plasmids were also analysed by plasmid MLST and replicon sequence typing, respectively. Among 21563 E. coli isolates, 240 (1.1%) overproduced AmpC ß-lactamases, including 180 (75.0%) harbouring ac-AmpC (132 CMY-2 variants and 48 DHA-1) and 60 (25.0%) c-AmpC enzymes. Three mutation profiles in the blac-AmpC promoter/attenuator were associated with a 72.5-, 19.9- and 5.8-fold increased expression, respectively. Moreover, 63.3% of ac-AmpC and 43.3% of c-AmpC isolates belonged to B2, D, E or F phylogenetic groups. PMQR was found in 31% of ac-AmpC isolates [38 qnrB4, 8 aac(6')-Ib-cr, 6 qnrS1 and 3 qnrB19] and in 10% of c-AmpC isolates [5 aac(6')-Ib-cr and 1 qnrS1]. IncI1-ST12 and IncF were associated with blaCMY-2 and blaDHA-1, respectively. These results suggest that ac-AmpC ß-lactamases were the main mechanism of AmpC production. Isolates and plasmids both showed high genetic diversity.
Subject(s)
Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Escherichia coli Infections/microbiology , Escherichia coli/enzymology , Escherichia coli/genetics , beta-Lactamases/genetics , beta-Lactamases/metabolism , Chromosomes, Bacterial , DNA Fingerprinting , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , Drug Resistance, Bacterial , Electrophoresis, Gel, Pulsed-Field , Escherichia coli/classification , Gene Expression , Gene Transfer, Horizontal , Genes, Bacterial , Genetic Variation , Humans , Multilocus Sequence Typing , Mutation , Plasmids , Polymerase Chain Reaction , Quinolones/metabolism , Sequence Analysis, DNA , SpainABSTRACT
OBJECTIVES: To describe the prevalence and risk factors for infection due to AmpC ß-lactamase-producing Escherichia coli (AmpC-EC). METHODS: For the prevalence study, all clinical isolates of E. coli with reduced susceptibility to third-generation cephalosporins were prospectively included from June 2010 to November 2011. For risk factor analysis, a case-control study was conducted. Cases were patients with an infection due to AmpC-EC. Controls were patients infected with cephalosporin-susceptible E. coli, matched 1â:â2. Detection of blaAmpC genes was done with a multiplex AmpC-PCR, and hyperproduction of E. coli chromosomal blaAmpC by quantitative RT-PCR. Alteration of the blaAmpC promoter was studied by PCR and sequencing. RESULTS: We identified 243 (1.1%) AmpC-EC strains out of 21â563 clinical isolates. Three cases with strains carrying ESBLs, 18 strains that were considered due to colonization and 8 cases lost to clinical follow-up were excluded. Finally, 214 cases were included in the analysis. Ninety-one cases (42.5%) and 269 (62.8%) controls were strictly community acquired (Pâ<â0.001). Thirty-five (16.3%) cases and 186 controls (43.5%) did not have any identifiable risk factor (Pâ<â0.001). Among cases, 158 (73.8%) were found to harbour an acquired AmpC (73.4% CMY-2). Previous use of fluoroquinolones [OR 2.6 (95% CI 1.12-3.36); Pâ=â0.008] was independently associated with AmpC-EC in the multivariate analysis. CONCLUSIONS: Prevalence of AmpC in E. coli remains low in our area. Plasmid acquisition (CMY type) represents the main mechanism of AmpC production. A high proportion of community-acquired isolates and patients with no identifiable risk factors were found. Previous use of fluoroquinolones was identified as a risk factor.
Subject(s)
Bacterial Proteins/biosynthesis , Escherichia coli Infections/epidemiology , Escherichia coli Infections/microbiology , Escherichia coli/enzymology , beta-Lactamases/biosynthesis , Adult , Aged , Aged, 80 and over , Bacterial Proteins/genetics , Case-Control Studies , Cross-Sectional Studies , Escherichia coli/genetics , Escherichia coli/isolation & purification , Female , Gene Expression Profiling , Humans , Male , Middle Aged , Multiplex Polymerase Chain Reaction , Promoter Regions, Genetic , Prospective Studies , Real-Time Polymerase Chain Reaction , Risk Factors , Sequence Analysis, DNA , beta-Lactamases/geneticsABSTRACT
The model described by Bewick et al seems to be able to distinguish between H1N1 influenza-related pneumonia and non-H1N1 community acquired pneumonia (CAP) based on five criteria. However, bacterial infection in the influenza group has not been accurately excluded. Therefore, this model could misidentify these patients and lead to an inappropriate treatment. We conducted a prospective observational study to compare mixed pneumonia vs viral pneumonia. In the mixed pneumonia group patients were older, had higher levels of procalcitonine and higher scores of severity. In our cohort the model proposed by Bewick et al would not identify patients with coinfection.
