Antibiogram, Haemolysis and Biofilm Properties of Escherichia coli from Bovine Mastitis

Abstract

Background: Escherichia coli cause mammary gland inflammation in dairy cows with striking local and sometimes severe systemic clinical symptoms. This disease affects many high producing cows in dairy herds and may cause several cases of death per year in the most severe cases. The present study was planned to evaluate the antibiogram and virulence factors of the isolated bacteria responsible for mastitis. Methods: In this study, 300 milk samples were collected and subjected to identify clinical mastitis (based on clinical symptoms) and sub clinical mastitis (using California mastitis test). E. coli was isolated and identified from mastitis positive samples and further tested for antibiogram and virulence factors such as haemolysis, biofilm formation and fimH and pap genes presence. Result: Out of 300 milk samples collected, 121 (40.33%) were positive for mastitis. E. coli was isolated from only 30 (24.79%) out of 121 mastitis positive samples. On Serotyping for somatic antigen, 13 E. coli isolates belonged to somatic serogroup O83, 2 to O157 and one each to O8, O20, O49, O119, O128 and O145. The highest sensitivity of E. coli isolates was recorded for ciprofloxacin, followed by gentamicin, tetracycline, nitrofurantoin, chloramphenicol, amikacin, cefixime, trimethoprim, ampicillin/sulbactam, ceftriaxone, cefoperazone, cefotaxime, kanamycin, cefotaxime/clavulanic acid and amoxycillin in the decreasing order. Multidrug resistance (MDR) was recorded in 96.66% of isolates. Out of 30 E. coli isolates, 46.66% were haemolytic and 40.0% positive for Congo red dye binding. Biofilm production was shown by 76.66% isolates. Molecular characterization revealed presence of fimH gene in 9 isolates, but pap gene was not detected in any of the strain. It may be concluded that E. coli is an emerging environmental mastitogen in cows and isolation of MDR strains with virulence factors is of serious concern.