Occurrence of selected virulence genes in multidrug-resistant Escherichia Coli isolates from humans, animals and environment in Dar es salaam, Tanzania

Abstract

ABSTRACT Background: Escherichia coli is listed by the World Health Organization as one of the critical pathogen due to its vast array of virulence and antimicrobial resistance genes. The genes are widely spread between humans, animals and the environment through horizontal gene transfer. In humans, the bacterium is capable of causing a broad spectrum of intestinal and extra-intestinal diseases. Aim of the study: To determine the occurrence of virulence genes bfp, ompA, traT, eaeA and stx1 in multidrug-resistant E. coli isolates from humans, animals, and the environment in Dar es Salaam Tanzania. Methodology: This cross-sectional study involved 50 MDR E. coli isolates; 15 from humans, 6 isolates from the environment and 29 isolates from animals, of them 16 were from domestic pigs and 13 from poultry. These isolates were cultured on MacConkey agar (Oxoid Ltd, Hampshire, UK) and Nutrient agar (Oxoid Ltd, Hampshire, UK) aerobically at 37°C for 24 hrs. Multiplex PCR (New England Biolabs, Ipswich, MA, USA) was used to detect virulence genes ompA, traT, eaeA and stx1, while bfp was detected using a uniplex PCR (New England Biolabs, Ipswich, MA, USA). T. Descriptive analysis was used to determine the prevalence of virulence gene(s) among MDR E. Coli. Differences in the occurrence of the five genes between sample sources were determined using Chi-square and p < 0.05 was considered to be significant. Principal component analysis (PCA) was used to determine distribution and relationships of antimicrobial resistance and virulence genes of MDR E. coli isolates. Results: All 50/50 (100%) MDR E. coli isolates were found to carry at least one virulence gene, with 19/50 (38%) carrying four genes, bfp + traT + eaeA + ompA. The findings showed high occurrence of virulence genes bfp (82%), traT (82%), eaeA (78%) and ompA (72%), whereas stx1 was not detected in any of the isolates. For humans, the most detected virulence genes were bfp and traT 14/15 (93.3%), for poultry, was eaeA 13/14 (92.9%), for pigs were bfp and traT 13/15 (86.7%) while for river water the most detected gene was eaeA 6/6 (100%). PCA results show the virulence genes ompA, traT, eaeA and bfp contributed to virulence of the isolates. The PCA ellipses show that isolates from pigs had more virulence genes compared to those isolated from poultry, river water, and humans. No association was observed between virulence genes and the antimicrobial-resistant genes. Conclusion: The high frequency of virulence genes in MDR E. coli isolates from humans, animals, and the environment indicates these isolates have very high potential to cause diseases which are difficult to treat, emphasizing the need for integrated surveillance and control measures.