Abstract
BackgroundWe investigated the molecular characteristics of multidrug-resistant, extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae isolated in community settings and in hospitals in Antananarivo, Madagascar.ResultsForty-nine E. coli, K. pneumoniae, K. oxytoca and E. cloacae ESBL-producing isolates were studied. In antimicrobial susceptibility analyses, many of the isolates exhibited resistance to aminoglycosides, fluoroquinolones and trimethoprim-sulfamethoxazole. Gene amplification analysis and sequencing revealed that 75.5% (n=37) of the isolates harbored blaCTX-M-15 and 38.7% (n=19) harbored blaSHV-12. The non-ESBLs resistance genes detected were blaTEM-1, blaOXA-1, aac(6′)-Ib,aac(6′)-Ib-cr, tetA, sul-1, sul-2, qnrA, qnrB and catB-3. We found dfrA and aadA gene cassettes in the class 1 integron variable regions of the isolates, and the combination of dfrA17-aadA5 to be the most prevalent. All blaCTX-M-15 positive isolates also contained the ISEcp1 insertion element. Conjugation and transformation experiments indicated that 70.3% of the antibiotic resistance genes resided on plasmids. Through a PCR based replicon typing method, plasmids carrying the blaSHV-12 or blaCTX-M-15 genes were assigned to either the IncFII replicon type or, rarely, to the HI2 replicon type. All isolates were subtyped by the rep-PCR and ERIC-PCR methods.Phylogenetic grouping and virulence genotyping of the E. coli isolates revealed that most of them belonged to group A1. One isolate assigned to group B2 harbored blaCTX-M-15 and five virulence genes (traT, fyuA, iutA, iha and sfa) and was related to the O25b-ST131 clone.ConclusionsOur results highlight the dissemination of multidrug resistant Enterobacteriaceae isolates in Antananarivo. These findings underline the need for a rational use of antibiotic and for appropriate methods of screening ESBL in routine laboratories in Antananarivo.
Highlights
We investigated the molecular characteristics of multidrug-resistant, extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae isolated in community settings and in hospitals in Antananarivo, Madagascar
BlaCTX-M-15 is recognized as the most widely distributed CTX-M enzyme [8]. It is derived from CTX-M-3 by a substitution of Asp-240-Gly which increases its catalytic efficiency against ceftazidime [9]. blaCTX-M-15 are encoded on plasmids belonging to the incompatibility group IncF [10]
We found blaCTX-M-15 to be the most prevalent ESBL in Madagascar, as it was detected in 75.5% of the isolates we studied
Summary
We investigated the molecular characteristics of multidrug-resistant, extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae isolated in community settings and in hospitals in Antananarivo, Madagascar. Extended-spectrum β-lactamase (ESBL)-producing bacteria represent a major worldwide threat among drug-resistant bacteria in both hospital and community settings [1]. A novel type of ESBLs, the CTX-M enzymes, emerged worldwide, mostly from Enterobacteriaceae [5,6]. CTX-M β-lactamases are not closely related to TEM or SHV ESBLs but share high amino-acid identity with chromosomal β-lactamases from Kluyvera spp. BlaCTX-M-15 is recognized as the most widely distributed CTX-M enzyme [8]. It is derived from CTX-M-3 by a substitution of Asp-240-Gly which increases its catalytic efficiency against ceftazidime [9]. In the upstream region of CTX-M genes an insertion sequence element, ISEcp, is commonly present and is likely responsible for the transposition process of the genes [11]
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