Isolation of Escherichia coli, Klebsiella spp. and Staphylococcus spp. from Bovine Mastitic Milk in Nuwera Eliya District of Sri Lanka and their Sensitivity to Commonly Used Antibiotics

Aims: Mastitis is one of the very important and most common diseases among dairy cattle globally which leads to severe economical losses in the dairy industry. For the sustainability of the dairy sector it is critical that efficient, economically feasible treatment regime is available for clinical cases of mastitis as a part of the control program with minimum risk for residues in milk. Antimicrobials are the most common drugs of choice for controlling and preventing this devastating condition. But the frequent use of antibiotics leads to the development of resistant bacteria which could have an adverse effect on human health as well. To mitigate this destructive constraint in the industry, identifying the etiology and their susceptibilities to remedial measures are of paramount importance. Hence this study was aimed at isolating and identifying the common bacterial etiology Escherichia coli, Klebsiella spp. and Staphylococcus spp. of mastitis and evaluating the antimicrobial susceptibility of the isolates in order to develop mastitis control strategies in the area.

Study Design: Milk samples were collected from mastitic cows in different stages including subclinical and clinical cases based on the results of California Mastitis Test

Place and Duration of Study: Samples were collected from dairy farms in Nuwera Eliya District, Sri Lanka and Laboratory investigations were carried out in the Laboratory of Livestock Production, Faculty of Agricultural Sciences, Sabaragamuwa University of Sri Lanka, Between Aug. 2017 and Nov. 2017.

Methodology: E.coli, Klebsiella spp. and Staphylococcus spp. were isolated from 31 milk samples and susceptibility to commonly used antibiotics (Trimethoprim, Oxytetracycline, Chloramphenicol, Cephalexin, Enrofloxacin and Ciprofloxacin) was determined by Kirby Bauer disk diffusion method.

Results: The study revealed that the most common isolate was the Klebsiella spp. and it is 54.8% and other two organisms Staphylococcus spp. had 51.6% and Escherichia coli 41.9%. Of all isolated pathogen, 97.1% exhibited resistant to Cephalexin and it was the highest while lowest resistance was to Chloramphenicol (31.4%). Among the other antibiotics, 54.3% of total isolates showed resistance to Trimethoprim followed by 42.9% to Oxytetracycline and Enrofloxacin, 34.3% was resistant to Ciprofloxacin. Resistance to at least one antibiotic was observed for the isolated microorganisms. All the three isolated pathogens are more resistant to Cephalexin. Both E. coli and Klebsiella spp. show 100% resistance to Cephalexin while Staphylococci had 92.9% resistance. This further revealed that E. coli (10%) and Klebsiella spp. (27.3%) are showing the least resistance to Chloramphenicol, None of Staphylococcus spp. (0%) isolated show resistance to Enrofloxacin.

Conclusion: Most common organisms isolated were Klebsiella spp. followed by Staphylococcus spp., E. coli and there is a resistance of isolated organisms to some commonly used antibiotics.