Phylogenetic Group and Virulence Gene Profile of Bovine Mastitis Escherichia coli Isolates from North West Cameroon

Abstract

Escherichia coli, a facultative anaerobic bacterium existing in symbiosis in the gut of warm-blooded animals, has several strains some of which are pathogenic. Its virulence and pathogenicity have been associated with one of several phylogenetic groups. We examined bovine mastitis E. coli strains to identify phylogenetic groups and virulence genes in order to understand the public health implications of consuming unpasteurised milk. Thirty-seven E. coli isolates previously recovered from mastitis milk and identified by biochemical methods were confirmed by PCR and sequencing. The phylogenetic groups associated with mastitis were determined by the Clermont quadruplex PCR method. We also investigated 23 virulence genes in the isolates. All 37 isolates were confirmed to be E. coli. The phylogenetic groups detected were: A (37.8%), B1 (37.8%), F (8.1%), D (2.7%) and E (2.7%). We detected 11 of the 23 virulence genes investigated, and thirty-six (97.3%) isolates harboured at least one virulence gene. The genes detected were fimH (91.9%),  traT (62.2%), ehlyA and stx2 (37.8% each), eaeA (35.1%), stx1 (29.7%), f17 (16.7%), kspMII (13.5%), iucD (10.8%), malX (8.1%) and hlyA (8.1%). Nine virulence gene combinations were identified in phylogroups A and B. The detection of iucD and malX were significantly associated with E. coli that belonged to phylogenetic group F. Most E. coli strains in this study are related to intestinal E. coli pathotypes, based on the phylogroups and virulence genes suggesting a public health threat. Hence, biosafety measures are recommended in handling raw milk, while consuming unpasteurized milk should be discouraged.