Dr. Rathish R. L.VIGNESH S2024-01-232024-01-232022-10-15https://krishikosh.egranth.ac.in/handle/1/5810206498The present study was conducted to assess the biocide sensitivity and to detect the presence of biocide resistance genes among staphylococci isolated from infected milk and udder surface. A total of 20 organised dairy farms of Wayanad were selected. Study revealed that only five per cent of farms practiced udder sanitation procedures. Clinical mastitis was detected in nine animals. Subclinical mastitis was detected in 29 and 31 per cent of animals based on California Mastitis Test and Somatic Cell Counts, respectively. A total of five Staphylococcus aureus isolates and 11 isolates of coagulase negative staphylococci (CNS) were isolated form milk. All cases were successfully treated with parenteral enrofloxacin along with neomycin or cefoperazone. It was observed that udder surface bacterial load increased significantly if udder sanitation procedures were not followed. The counts significantly decreased if udder sanitation was followed. Machine milking resulted in lower microbial loadin post milking. A total of 17 S. aureus isolates were obtained from 96 udder wash samples. Minimum Inhibitory Concentration (MIC) of povidone iodine, chlorhexidine and cetyltrimethylammonium bromide (CTAB) against the staphylococcal isolates were also estimated. Average MIC of chlorhexidine against S. aureus and CNS isolates was 0.88 µg/ml and 0.09µg/ml respectively, significant at p<0.01. Average MIC of povidone iodine against S. aureus and CNS isolates was 13.84µg/ml and 19.15µg/ml, while it was 0.58 µg/ml and 0.27µg/ml for CTAB, respectively. Biocide resistance was noted against chlorhexidine and povidone iodine. Povidone iodine had the highest and the widest range of MICs. The MIC of S. aureus form udder wash had higher MIC than those from mastitis cases. Polymerase chain reaction targeting virulence gene amplified of ica A inthree and ica D in one isolate. Gene coding resistance to quaternary ammonium compounds (qac A/B) was detected from seven isolates of S. aureus obtained from mastitis, while smr gene, which coded for chlorhexidine resistance was obtained from two isolates. The study revealed the presence of biocide resistantstrains of S. aureus even in farms that seldom use any biocidesEnglishThesis