First Detection of Human ST131-CTX-M-15-O25-B2 Clone and High-Risk Clonal Lineages of ESBL/pAmpC-Producing E. coli Isolates from Diarrheic Poultry in Tunisia

Abstract

Circulation of a multi-resistance clone of bacteria associated with genetic elements in diseased animals constitutes a global public health problem. Our study focused on the characterization of the support of ESBL in cefotaxime resistant E. coli (CTX ^R) isolates recovered from poultry with diarrhea, analysis of their clonal lineage, and virulence-associated genes. The study was carried out on 130 samples of chickens with diarrhea, collected in 2015 from poultry farms in Tunisia. Isolates of 20 CTX ^R  E. coli strains were identified as ESBL and AmpC β- lactamase producers. The following β-lactamase genes (number of isolates) were detected: bla _CTX-M-15+ bla _OXA1 (4), bla _CTX-M-15 + bla _OXA1 + bla _TEM-1b (2), bla _CTX-M-1 + bla _TEM-1b (9), bla _CTX-M-1 (2), bla _CMY2 + bla _TEM-1b (3). Six E. coli harboring bla _CTXM-15 were allocated to ST131-B2-O25b-; six and three bla _CTX-M-1 were grouped in ST155, ST10, and ST58, respectively, related to the phylogroup D and A. The qnrB gene, the variant aac(6′)-Ib-cr, and the class 1 integrons with different gene cassettes, were detected amongst our 20 isolated strains, which were classified as ExPEC and aEPEC. Our findings highlighted the emergence of the human pandemic ST131-CTX-M-15-O25-B2 clone and the high risk of such clonal lineage strains in diarrheic poultry, in Tunisia, which could constitute a risk of their transfer to healthy animals and humans.