Atypical epidemiology of CTX-M-15 among Enterobacteriaceae from a high diversity of non-clinical niches in Angola

The objective of this study was to investigate the distribution and molecular epidemiology of ESBLs, acquired AmpCs and carbapenemases in Enterobacteriaceae from non-clinical niches in Angola, an under-researched sub-Saharan country. Eighty-one samples were recovered from healthy persons (naEuroS=aEuroS18), healthy animals (naEuroS=aEuroS33) and their environments (naEuroS=aEuroS10) or aquatic settings (naEuroS=aEuroS20) in south Angola (2013). Samples were plated onto CHROMagar (TM) Orientation with/without antibiotics. Standard methods were used for bacterial identification, characterization of bla genes, antibiotic susceptibility testing and conjugation assays. Clonal analysis (XbaI-PFGE, MLST and Escherichia coli phylogroups), location of bla and plasmid characterization (S1-PFGE, I-CeuI-PFGE, replicon typing and hybridization) were also performed. ESBLs (almost exclusively CTX-M-15, 98%) were detected in 21% (45/216) of the isolates, recovered from diverse non-clinical niches and belonging to different Enterobacteriaceae species (mainly E. coli). Acquired AmpCs or carbapenemases were not found. The pandemic B2-ST131 E. coli clone was not identified, but some widespread clonal complexes (CCs) from A (CC10 and CC168), B1 (CC156) or D (CC38) phylogroups were detected. bla(CTX-M-15) was variably identified on typeable (29%; 100-335 kb; IncFII, IncFII(K6), IncHI2 and IncY) or non-typeable (16%; 70-330 kb) plasmids or on the chromosome (14%), while for 41% of the isolates its specific location was not determined. This study reports, for the first time in Angola, an unexpected high occurrence of CTX-M-15 in diverse non-clinical niches and Enterobacteriaceae species, and uncovers novel plasmid replicons in under-researched geographical regions. The diffusion of bla(CTX-M-15) through such a high diversity of genetic backgrounds (clones, typeable/non-typeable plasmids and genetic environments) unveils an extraordinary ability for bla(CTX-M-15) acquisition and mobilization favoured by unrecognized ecological factors.