The prevalence and antibiotic susceptibility of Staphylococcus spp. on ocular surfaces of fighting bulls (Bos indicus) in Thailand

Background and Aim: Fighting bulls have a high risk of eye injuries, and opportunistic conjunctival bacterial flora may cause subsequent eye diseases. There is little information about the ocular health care of fighting bulls in Thailand. Thus, this study aimed to estimate the prevalence of Staphylococcus spp. from the eyes of fighting bulls and investigate their antimicrobial susceptibility.

Materials and Methods: The samples were collected from the right conjunctival sacs of 105 fighting bulls. Biochemical tests and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry were used to identify bacteria to genus and species levels. Antimicrobial susceptibility was tested by agar disk diffusion.

Results: Staphylococcus spp. (36.84%, 56/152) were the most detected bacteria. The most prevalent Staphylococcus spp. was Staphylococcus chromogenes (37.50%, 21/56). The susceptibility test revealed that all isolates were susceptible to sulfamethoxazole/trimethoprim (56/56, 100%) and most were susceptible to chloramphenicol and gentamicin (54/56, 96.43%). The highest resistance rates were seen for tetracycline and doxycycline (23.21%, 13/56) followed by erythromycin (19.64%, 11/56). In addition, S. chromogenes isolates were evaluated for their ability to produce biofilms by a quantitative biofilm production assay. A total of 21 isolates exhibited biofilm production, independent of their antimicrobial susceptibility. Three multidrug-resistant isolates were found, including two Staphylococcus epidermidis isolates and a single S. chromogenes isolate.

Conclusion: As antimicrobial resistant bacteria were detected on the eye surface, veterinarians should always conduct antimicrobial susceptibility testing before using antimicrobial agents. The results from this study will help to improve the standard of eye treatment for fighting bulls in Thailand.