Phylogenetic Distribution of CTX-M- and Non-Extended-Spectrum-β-Lactamase-Producing Escherichia coli Isolates: Group B2 Isolates, Except Clone ST131, Rarely Produce CTX-M Enzymes

Abstract

i Escherichia coli is the species most frequently associated with clinical infections by extended-spectrum-␤-lactamase (ESBL)-producing isolates, with the CTX-M ESBL enzymes being predominant and found in genetically diverse E. coli isolates. The main objective of this study was to compare, on the basis of a case-control design, the phylogenetic diversity of 152 CTX-M-producing and 152 non-ESBL-producing clinical E. coli isolates. Multilocus sequence typing revealed that even though CTX-M enzymes were largely disseminated across the diversity of E. coli isolates, phylogenetic group B2 showed a particularly heterogeneous situation. First, clone ST131 of group B2 was strongly associated with CTX-M production (55 [79%] of 70 isolates), with CTX-M-15 being predominant. Second, the remaining members of group B2 were significantly less frequently associated with CTX-M production (9 [12%] of 75) than E. coli phylogenetic groups A, B1, and D (88 [55%] of 159). CTX-M-producing ST131 E. coli isolates were significantly more frequent in patients hospitalized in geriatric wards or long-term care facilities. Besides, the non-ESBL ST131 isolates significantly more frequently showed resistance to penicillins than the non-ESBL, non-ST131 isolates did. In conclusion, the present study emphasizes the particular antimicrobial resistance and epidemiologic characteristics of clone ST131 within group B2, which could result from the higher antibiotic exposure of this clone, as it is the predominant clone of group B2 carried in the human gut. E scherichia coli is the Enterobacteriaceae species that causes the largest number of infections, but this species is also a widespread gut commensal of humans and animals. Strains of E. coli are therefore frequently exposed to antimicrobial agents, which has resulted in the emergence and rapid diffusion of antibioticresistant E. coli clinical isolates. Extended-spectrum ␤-lactamases (ESBLs), which confer resistance to extended-spectrum cephalosporins, were, until the year 2000, produced essentially by Klebsiella pneumoniae and Enterobacter sp. isolates responsible for nosocomial infections. However, E. coli has become dominant among the ESBL-producing enterobacterial species. This is especially worrisome as the human gut carriage of E. coli favors the dissemination of ESBLs in the community (31). Interestingly, the switch of dominant species among the ESBL-producing enterobacterial isolates occurred concomitantly with the emergence of novel ESBL enzymes that belong to the CTX-M family. The CTX-M enzymes have superseded the TEM and SHV ESBLs (2) and are found in genetically diverse E. coli isolates. Among CTX-M enzymes, CTX-M-15 predominates and has been associated with the dissemination of a particular E. coli clone of sequence type 131 (ST131) (23,27).The species E. coli is genetically diverse, and strains have been classified into a number of phylogenetic groups, the most frequent ones being A, B1, B2, and D (12, 14, 29, 32). The ST131 clone belongs to phylogenetic group B2 and is associated wi...

Detection of phenotypes, virulence genes and phylotypes of avian pathogenic and human diarrheagenic Escherichia coli in Egypt

“…In this study, there was an over-representation of commensal phylogroups A and B1 among human isolates, which is consistent with the reports of previous studies that DEC isolates were included in phylogroups A, B1, and D [43,44]. The molecular identification of eae and stx genes in 50% of the human commensal phylotypes in this study is in agreement with the explanation of Escobar-Paramo et al [42], who reported that human DEC strains (which belong to the commensal phylogroups) might have the genetic precursors and virulence genes necessary for disease emergence.…”

Escherichia coli ST131, an Intriguing Clonal Group

“…In the United Kingdom, an analysis of 300 consecutive UTI E. coli isolates showed the prevalence of E. coli ST131 to be 9% among the non-ESBL-producing isolates and 54% among those producing ESBL (109). The lower of these two figures (9%) is similar to that reported in France for all non-ESBL-producing isolates (10%), whereas the higher figure (54%) is closer to that reported in the United States among all ESBL-producing isolates (49 to 50%) than to that reported in France (36%) (16,110). A study by Croxall et al focused on elderly patients in the United Kingdom, in whom E. coli ST131 accounted for 22% of the E. coli isolates causing community-and hospital-acquired UTI (17).…”

“…These studies reported similar prevalences of E. coli ST131 among the non-ESBLproducing isolates: 10% in France (2008 to 2009), 12% in Spain (2010), and 13% in each of the other two studies, carried out in the United States (2007 to 2012). However, the reported prevalence among ESBL-producing isolates was higher in the United States (49 to 50%) than in France (36%) or Spain (23%) (16,54,156,161). ESBL-producing isolates and 72% among the ESBL producers (42).…”

“…Le Gall et al identified nine subgroups within group B2. Clermont et al placed E. coli ST131 in subgroup I, which was suggested to be the basal subgroup of B2 strains (15), suggesting that the characteristics of non-ST131 B2 strains may have evolved after the divergence of ST131 and related genotypes (ST1680, ST1982, and ST1461), (16,17). E. coli ST131 strains are mostly of serotype O25:H4, with a specific O25 type, O25b.…”

“…A very small number of studies (16,54) have provided information about resistance to various antibiotic families in E. coli ST131 isolates, comparing the results obtained with those for non-ST131 E. coli isolates producing or not producing ESBL (Tables 2 and 3). For ESBL-producing isolates, these studies showed that E. coli ST131 isolates were consistently more frequently resistant to amikacin than non-ST131 isolates and potentially more frequently resistant to amoxicillin-clavulanic acid, piperacillin-tazobactam, or ciprofloxacin; they were also more frequently suscep- tible to gentamicin or co-trimoxazole than non-ST131 isolates, depending on the country considered (Table 2).…”