High Prevalence of Antibiotic Resistant Escherichia coli Serotype O157: H7 among Pastoral Communities in Rural Uganda

Background: Non-prescribed use of antimicrobials in Agriculture incurs a transfer risk of resistant pathogens to humans, complicating treatment. The aim of this study was to determine the potential of Zoonotic E. coli to serve as drivers of antimicrobial resistance (AMR) among animals and humans in pastoralist communities in Kasese district, so as to protect the community.

Materials and Methods: A laboratory based cross-sectional study was done using archived E. coli isolates previously obtained from humans in pastoralist communities of Kasese district, Uganda. Recovery of the isolates was done by conventional culture, and Identification by biochemical methods, serotyping and PCR. Kirby Bauer disc diffusion method was adopted for AMR profiling. Isolates were screened for resistance mechanisms including Extended Spectrum β-lactamase (ESBL), Carbapenemases and AmpC production using disc diffusion based methods.

Results: The prevalence of Enterohemorrhagic E. coli (EHEC) was 16% (28/180). These EHEC isolates belonged to phylogroups; B1 (94%, 26/28), B2 (3%, 1/28) and A (3%, 1/28). All the 28 EHEC isolates possessed the virulence gene stx1, 26 of the 28 EHEC isolates contained the virulence gene stx2e, but none of the 28 possessed the virulence gene stx2. Highest resistance was seen to Cotrimoxazole (89%, 25/28), Tetracycline (71%, 20/28), Ampicillin (65%, 18/28) and Nitrofurantoin (28%, 8/28), these are the most commonly used antimicrobials in the agricultural sector in Uganda. Minimal resistance was observed to the antimicrobials that are commonly used in human medicine especially β-lactams, β-lactam+inhibitors and Carbapenems. Of the 28 zoonotic E. coli isolates, 17%, (5/28) were ESBL positive and among these 1 (3%, 1/28) was a Carbapenemase producer.

Conclusion: There is a high prevalence of highly pathogenic, drug resistant E. coli O157:H7 among humans in pastoralist communities in Uganda. We suspect that these were acquired from animals because they mostly contained vero toxin gene vt2e which is animal specific, predominantly swine. Also majority of these EHEC isolates belonged to phylo-group B1 which has been documented to inhabit domestic animals. We recommend future studies to investigate relatedness of drug resistant isolates from humans and animals to ascertain the zoonotic spread of resistant enterohemorrhagic E. coli in pastoralist communities.