Non-typhoidal Salmonella and Zoonotic E. coli as Potential Drivers of Antimicrobial Resistance in Pastoralist Communities in Kasese District, Uganda
School of Medicine, Islamic University in Uganda
Introduction: Non-prescribed use of antimicrobials in Agriculture incurs a transfer risk of resistant pathogens to humans. The aim of this study was to determine the potential of non-typhoidal Salmonella spp and Zoonotic E. coli to serve as drivers of Antimicrobial resistance among animals and humans.
Methodology: A laboratory based cross-sectional study was done using archived Salmonella spp and E. coli isolates previously obtained from individuals among pastoralist communities of Kasese district, Uganda. Recovery of the isolates was done by conventional culture and Identification by biochemical methods, serotyping and PCR. Antimicrobial resistance profiling was done by using Kirby bauer disc diffusion method. Following this; the isolates were screened for resistance mechanisms including Extended Spectrum β-lactamase, Carbapenemase and AmpC production using disc diffusion based methods.
Results: The prevalence of Enterohemorrhagic E.coli (EHEC) and Non Typhoidal salmonella were 16% (28/180) and 50% (1/2) respectively. Of the EHEC, 94% (26/28) were of phylogroup B1, A (3%, 1/28) and B2 (3%, 1/28). The most prevalent virulence gene in the EHEC was Stx1 (100%, 28/28) followed by Stx2e (94%, 26/28), none was Stx2 positive. Highest resistance was seen to Cotrimoxazole (89%, 25/28), Tetracycline (71%,20/28), Ampicillin (65%,18/28) and Nitrofurantoin (28%,8/28), these are commonly used in the agricultural sector, whereas minimal resistance was observed to those commonly used in human medicine especially the β-lactams, β-lactam inhibitors and Carbapenems. 17%, (5/28) of the EHEC were ESBL positive, of these one (3%, 1/28) was a Carbapenemase producer. Though only one Non-typhoidal Salmonella isolate was found, it is worrying to note that it showed resistance to all the three antimicrobial agents (Nalidixic acid, Chloramphenicol and Ciprofloxacin) that are most recommended for treatment of Salmonellosis in this setting.
Conclusion: There is a high prevalence of highly pathogenic and resistant zoonotic E. coli and low prevalence of Non typhoidal salmonella among humans in pastoralist communities in Uganda. We suspect that these pathogens, along with their AMR genes, were acquired from animals because the zoonotic E. coli (EHEC) largely contained the animal specific Vero toxin gene VT2e and majority belonged Pylo-group B1 which has been documented as the most common EHEC phylo-group inhabiting domestic animals. Therefore, it is highly likely that zoonotic bacteria are potential drivers of antimicrobial resistance to humans in these settings and we recommend that studies involving relatedness of drug resistant isolates from humans and animals should be conducted to ascertain the role of enterohemorrhagic E. coli in the zoonotic spread of antimicrobial resistance in pastoralist communities. We recommend that a one health approach should be used to establish drivers of MDR spread in pastoralist communities.