Antibiotic Sensitivity of Bacteria Isolated from a Dairy Farm in Kandy, Sri Lanka

Abstract

The dairy industry is a vital constituent in livestock which is a substantial part of agriculture and significantly contributes to the local economy producing approximately 42 million litres of milk per month. Indiscriminate use of antibiotics in livestock industry is considered to be a reason for emerging antibiotic resistance among dairy bacteria. Investigating the antibiotic resistance of such bacteria is essential to prevent adverse effects on animal and public health through corrective measures. The current study aimed at isolation and identification of dairy faecal bacteria and determine their antibiotic resistance. Freshly voided faecal samples were collected from ten cattle at a dairy farm in Kandy, Central Province, Sri Lanka in March 2022. Faecal bacteria were isolated by standard microbiological techniques. Morphological and biochemical tests were performed on 35 chosen bacterial colonies for identification. Kirby-Bauer disk diffusion method (CLSI) was employed on 6 representative bacterial spp to detect susceptibility for 10 antibiotics. In this study, 6 bacterial species identified were Bacillus spp (62.9%), Staphylococcus spp (11.4%), Pseudomonas aeruginosa (8.6%), Enterobacter spp (8.6%), Escherichia coli (5.7%), and Streptococcus spp (2.9%). All six tested isolates were sensitive to Amikacin, Chloramphenicol, Enrofloxacin, Gentamycin, and Imipenem. Five isolates were sensitive to Ciprofloxacin, Streptococcus spp indicating intermediate susceptibility. The highest resistance was shown against Ampicillin (66.6%) followed by Amoxicillin (50%). S. aureus was resistant to Amoxicillin, Ampicillin and Cefuroxime. B. subtilis, Streptococcus spp, and E. coli each were resistant to two antibiotics. The effect of Tetracycline was intermediate on S. aureus and Enterobacter spp while other bacteria were susceptible. Present results revealed the complete susceptibility of examined bacteria to five antibiotics critically or highly important to animals and humans, suggesting low selection pressure. However, higher resistance to two Aminopenicillins and reduced effectiveness of other three antibiotics indicate the need to minimize resistance development in the farm through modified management practices.