Abstract
Data on the prevalence of antibiotic resistance in Enterobacteriaceae in African wildlife are still relatively limited. The aim of this study was to estimate the prevalence of phenotypic intrinsic and acquired antimicrobial resistance of enterobacteria from several species of terrestrial wild mammals in national parks of Gabon. Colony culture and isolation were done using MacConkey agar. Isolates were identified using the VITEK 2 and MALDI-TOF methods. Antibiotic susceptibility was analysed and interpreted according to the European Committee on Antimicrobial Susceptibility Testing guidelines. The preliminary test for ESBL-producing Enterobacteriaceae was performed by replicating enterobacterial colonies on MacConkey agar supplemented with 2 mg/L cefotaxime (MCA+CTX). Extended-spectrum beta-lactamase (ESBL) production was confirmed with the double-disc synergy test (DDST). The inhibition zone diameters were read with SirScan. Among the 130 bacterial colonies isolated from 125 fecal samples, 90 enterobacterial isolates were identified. Escherichia coli (61%) was the most prevalent, followed by Enterobacter cloacae (8%), Proteus mirabilis (8%), Klebsiella variicola (7%), Klebsiella aerogenes (7%), Klebsiella oxytoca (4%), Citrobacter freundii (3%), Klebsiella pneumoniae (1%) and Serratia marcescens (1%). Acquired resistance was carried by E. coli (11% of all E. coli isolates) and E. cloacae (3% of all E. cloacae) isolates, while intrinsic resistance was detected in all the other resistant isolates (n = 31); K. variicola, K. oxytoca, K. pneumoniae, E. cloacae, K. aerogenes, S. marcescens and P. mirabilis). Our data show that most strains isolated in protected areas in Gabon are wild type isolates and carry intrinsic resistance rather than acquired resistance.
Highlights
The emergence of antibiotic resistant bacteria (ARB) in the Enterobacteriaceae family is a major issue worldwide that affects the dynamics of microbial populations and leads to human public health problems [1]
The discovery of resistant Enterobacteriaceae strains carried by wild animals or in the environment, outside areas frequented by humans and for which human contamination seems unlikely, suggests that resistance might be present in environmental reservoirs and has an adaptive significance that predates the antibiotic era [5,6,7]
60% (52/90) of these enterobacterial isolates were susceptible to all the antibiotics tested, E. coli (56%, 51/90) and P. mirabilis (3%, 3/90)
Summary
The emergence of antibiotic resistant bacteria (ARB) in the Enterobacteriaceae family is a major issue worldwide that affects the dynamics of microbial populations and leads to human public health problems [1]. Acquired resistance is found only in some isolates of a bacterial species and results from horizontal gene transfer, or more rarely, from selection of a mutation. Many studies have documented the prevalence of resistance in wild animals. This phenomenon has been largely interpreted as the result of contacts with contaminated anthropogenic sources [4].
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