β-Lactamases Encoded by bla(CTX-M) Group I Genes as Determinants of Resistance of Esbl-Positive Enterobacteriaceae in European Soldiers in Tropical Mali

ESBL (extended-spectrum-β-lactamase)-positive Enterobacteriaceae, which colonized European soldiers in tropical Western African Mali, were subjected to a molecular assessment of their resistance determinants. By doing so, a better insight into the locally endemic pattern of ESBL-associated β-lactamase genes was aspired. From a previous study on diarrhea in European soldiers on deployment in tropical Mali, 15 ESBL-positive Escherichia coli with demonstrated high clonal diversity and one positive Klebsiella pneumoniae were assessed. Polymerase chain reactions (PCRs) for bla(TEM) and bla(SHV) β-lactamase genes with subsequent sequencing for the discrimination of ESBL- and non-ESBL variants were performed, followed by four group-specific PCRs for bla(CTX-M) genes. Non-ESBL-associated bla(TEM-1) was identified in six out of 15 (40%) E. coli strains, while 100% of the assessed strains were positive for group I bla(CTX-M). Considering the known clonal diversity of the assessed strains, the striking restriction to one group of bla(CTX-M) genes accounting for the ESBL phenotypes of the isolates suggests little genetic exchange in the local setting. Under such circumstances of restricted numbers of locally endemic target genes, PCR-based screening approaches for ESBL colonization might be promising.