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

J Antimicrob Chemother. 2016 May;71(5):1169-73. doi: 10.1093/jac/dkv489. Epub 2016 Feb 16.


Objectives: 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.

Methods: Eighty-one samples were recovered from healthy persons (n = 18), healthy animals (n = 33) and their environments (n = 10) or aquatic settings (n = 20) in south Angola (2013). Samples were plated onto CHROMagar™ 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.

Results: 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. blaCTX-M-15 was variably identified on typeable (29%; 100-335 kb; IncFII, IncFIIK6, 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.

Conclusions: 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 blaCTX-M-15 through such a high diversity of genetic backgrounds (clones, typeable/non-typeable plasmids and genetic environments) unveils an extraordinary ability for blaCTX-M-15 acquisition and mobilization favoured by unrecognized ecological factors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Angola
  • Animals
  • Conjugation, Genetic
  • Electrophoresis, Gel, Pulsed-Field
  • Enterobacteriaceae / classification
  • Enterobacteriaceae / enzymology*
  • Enterobacteriaceae / genetics
  • Enterobacteriaceae / isolation & purification*
  • Environmental Microbiology
  • Gene Transfer, Horizontal
  • Genotype
  • Healthy Volunteers
  • Humans
  • Microbial Sensitivity Tests
  • Multilocus Sequence Typing
  • Plasmids / analysis
  • beta-Lactamases / genetics*


  • beta-lactamase CTX-M-15
  • beta-Lactamases