Antibiogram Studies of Biofilm Forming Escherichia Coli and Pseudomonas Aeruginosa Isolated from Clinical Mastitis Cases in Bovines

Abstract

Mastitis is a common disease of dairy cattle. It is characterized by pathological changes in udder and bacteriological changes in milk, making it unfit for human consumption. In veterinary medicine, antibiotic treatment of mastitis has led to the development of antibiotic-resistant bacteria. To combat the treatment challenge of mastitis caused by Gram-negative bacteria, antibiogram profiling of Escherichia coli and Pseudomonas aeruginosa was done to select effective antibiotics against these bacteria. In this research, samples containing milk and puss were collected from affected quarter of udder of cattle and screening of mastitis was performed by using Surf field mastitis test. Samples tested positive for mastitis were used for culturing of bacteria. E. coli and P. aeruginosa were isolated and identified by using selective media and biochemical tests, respectively. The biofilm formation capacity of E. coli and P. aeruginosa was determined by performing biofilm assay. Both E. coli and P. aeruginosa isolates exhibited varied biofilm-formation capacities. E. coli isolates were classified as strong biofilm-formers (12%), moderate biofilm-formers (50%) and weak biofilm formers (38%). Furthermore, 20% of P. aeruginosa isolates were classified as strong biofilm-formers, 40% as moderate biofilm-formers and 40% as weak biofilm-formers Antibiogram of isolated bacteria was determined using disc diffusion test. Overall, E. coli isolates showed resistance to all the tested antibiotics except meropenem. P. aeruginosa isolates were found resistant to enrofloxacin, linezolid, cefixime and chloramphenicol, and susceptible to meropenem, vancomycin and azithromycin. These results suggest that meropenem could be an effective antibiotic against mastitis infections caused by E. coli and P. aeruginosa. Moreover, vancomycin and azithromycin could be used to treat mastitis infection caused by P. aeruginosa. These results indicate a dire need for the development of alternative therapeutic strategies for antibiotic-resistant biofilm-forming bacteria and surveillance of antibiotic resistance in treatment of mastitis infection in cattle.