Prevalence of the bovine mastitis causing bacteria and confirmation of the virulence potential of Mammary Pathogenic E. coli (MPEC)

Abstract

Bovine mastitis is the inflammation of the mammary glands due to physical injury or microbial infection. It is one of the most common and expensive disease of dairy industry resulting huge economic loss due to reduced milk production. Mastitis can be further classified into clinical and sub-clinical types based on the degree of inflammation. In this study, prevalence of bovine mastitis in the Rawalpindi district along with prevalence of mastitis causing bacteria in mastitis positive milk samples was investigated. Moreover, antibiotic susceptibility pattern, ESBL production, in vitro virulence properties, phylogenetic classification, prevalence of virulence associated genes (VAGs) and toxin genes were also analyzed for Mammary Pathogenic E. coli (MPEC). The prevalence of mastitis found was 13.98% (10.6% subclinical, 2.11% clinical) and 22% (20.58% subclinical, 1.47% clinical) for buffalos and cattle respectively. The most prevalent isolated bacteria included S. aureus, Streptococcus spp. and E. coli occurring in 80%, 30% and 26.78% respectively of total mastitis positive milk samples. Except for one, all MPEC isolates (95.45%) were Multi-drug resistant (MDR) and ESBL producers. All MPEC isolates were α-hemolytic while most isolates showed positive Congo red binding activity, different motility activities, low to medium biofilm formation and high growth in human urine. Most MPEC isolates belonged to D group (50%) followed by B1, B2 and A group E. coli at 27.27%, 18.18% and 9.09% respectively. Among VAGs, iss and fimH gene occurred in around 95.45% samples while papC and cvaC occurred in less than half number of samples. Prevalence of Shiga toxins also was high (59.09% for stx1and 4.54% for stx2) while hlyA and eaeA were present in 9.09% and 13.63% isolates respectively. The study reports high prevalence of bovine mastitis with very high resistance pattern of MPEC isolates and different virulence associated properties.