Prevalence, Antibiotic Resistance Pattern, and Molecular Characteristics of Staphylococcus epidermidis Isolated From Milk of Pure Breeds of Dairy Cattle With Subclinical Mastitis
Bovine mastitis, a widespread disease in dairy cattle characterized by udder inflammation triggered primarily by pathogenic micro-organisms, poses a considerable challenge to the dairy industry. Staphylococcus epidermidis (S. epidermidis) stands out as a significant etiological factor in the incidence of bovine subclinical mastitis (SCM), further exacerbated by the diminishing efficacy of antibiotics due to the increase in antibiotic-resistant strains. This study sets out to comprehensively investigate the landscape of S. epidermidis in dairy cattle afflicted with SCM. We examined the prevalence of S. epidermidis, assessed its antibiotic resistance patterns, and probed for the presence of antibiotic-resistant genes (mecA, tetK, and ermC) within S. epidermidis strains isolated from 305 milk samples across four distinct dairy cattle breeds: Holstein Friesian, Red Sindhi, Sahiwal, and Cholistani. Among the sampled cows, 56.39% (172 out of 305) were found to have SCM. Within this group, S. epidermidis was identified in 27.90% (48 out of 172) of the cases. Our breed-specific analysis revealed significant disparities, with Red Sindhi cows displaying the highest prevalence at 75%, followed by Holstein Friesian at 45.45%, and significantly lower levels in Sahiwal (5.19%) and Cholistani (3.44%) breeds. To assess the efficacy of antibiotics, we conducted sensitivity testing using nine commonly prescribed antibiotics. Alarmingly, 18 out of the 48 isolates (37.5%) exhibited multidrug resistance (MDR). Our antibiogram results underscored a high resistance of S. epidermidis isolates, particularly against cefoxitin (56.25%) and penicillin (43.75%), while demonstrating remarkable susceptibility to amikacin (2.08%), clindamycin (0%), ciprofloxacin (0%), and chloramphenicol (0%). Furthermore, we employed PCR to ascertain the presence of resistant genes in all S. epidermidis isolates. mecA was detected in 38 isolates (79.16%), while tetK was identified in 33 isolates (68.75%). Notably, the study did not detect the presence of the ermC gene. Our investigation highlights the efficacy of chloramphenicol, clindamycin, and ciprofloxacin against S. epidermidis. However, the prevalence of multidrug-resistant strains calls for careful antibiotic use in veterinary practices. Further research is needed to examine geographic and farm-specific factors affecting S. epidermidis prevalence, and genetic techniques like multilocus sequence typing should be employed to study clonal spread and horizontal gene transfer. Routine antimicrobial sensitivity assessments and continuous monitoring of medication use are essential to develop sustainable strategies against antibiotic resistance in the dairy industry.
Bovine mastitis, a widespread disease in dairy cattle characterized by udder inflammation triggered primarily by pathogenic micro-organisms, poses a considerable challenge to the dairy industry. …
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