Occurrence of antimicrobial-resistant bovine mastitis bacteria in Sakon Nakhon, Thailand.

BACKGROUND AND AIM

Bovine mastitis is an inflammation of the mammary gland of dairy cattle that causes economic losses due to poor quantity and quality of milk. The extensive or incorrect use of antibiotics has increased in the veterinary field, leading to the emergence of antibiotic-resistant pathogens worldwide. This study aimed to investigate bovine mastitis bacterial pathogens in Sakon Nakhon, Thailand.

MATERIALS AND METHODS

A total of 35 dairy farms were screened for clinical and subclinical mastitis using the California Mastitis Test and clinical examination. Polymerase chain reaction was used to characterize bacterial species-induced mastitis (380 isolates) in cattle and antimicrobial resistance genes, and disk diffusion and broth microdilution were used to characterize antimicrobial susceptibility.

RESULTS

The prevalence of (38.10%; 32/84)-induced mastitis in cattle was considerably high, followed by (33.33%), (25%), (8.33%), and (4.76%). In this study, spp. isolates demonstrated 100% susceptibility to cefoxitin, and no antibiotic-resistance genes were identified. Tetracycline (TET) and macrolide-resistant genes of spp. revealed that M was predominant in 55.63% (79/142), followed by S + (B) (16.90%). Antibiotic susceptibility tests revealed the following resistance profiles to bacterial species: TET (85.92%), clindamycin (29.58%), erythromycin (15.49%), levofloxacin (14.08%), and penicillin (0%). Gram-negative bacterial isolates ( [8.33%], [2.38%], [1.19%], and [1.19%]) were recovered and still susceptible to meropenem (100%), ceftazidime (97.06%), ceftriaxone (79.41%), and ciprofloxacin (79.41%).

CONCLUSION

This result suggested that mastitis pathogens in this area were susceptible to most antimicrobials, with the exception of streptococci against TET. In this study, limited data were available including one from small-holder dairy farms and study only dairy farms in Sakon Nakhon, Thailand. So, more farms should be included in the future studies.