RESUMEN
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 Staphylococcus epidermidis (38.10%; 32/84)-induced mastitis in cattle was considerably high, followed by Streptococcus agalactiae (33.33%), Streptococcus uberis (25%), Klebsiella pneumoniae (8.33%), and Staphylococcus aureus (4.76%). In this study, Staphylococcus spp. isolates demonstrated 100% susceptibility to cefoxitin, and no antibiotic-resistance genes were identified. Tetracycline (TET) and macrolide-resistant genes of Streptococcus spp. revealed that tetM was predominant in 55.63% (79/142), followed by tetS + erm(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 (K. pneumoniae [8.33%], Klebsiella variicola [2.38%], Klebsiella quasipneumoniae [1.19%], and Escherichia coli [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.
RESUMEN
Background and Aim: Bovine mastitis is one of the most serious issues in dairy production. It is caused by contagious and coliform pathogens such as Staphylococcus spp., Escherichia coli, and Klebsiella pneumoniae. In addition, the emergence of drug-resistant bacteria raises urgent concerns in the field of drug treatment, thus requiring the exploration of alternative treatments. Bacteriophage therapy has been shown to be a promising alternative approach for the control of antibiotic-resistant pathogens. In this study, we aimed to isolate phages specific to contagious mastitis and coliform mastitis, characterize the isolated phages, and examine their ability to lyse bacteria in pasteurized milk samples. Materials and Methods: The Staphylococcus phage vB_Sau-RP15 isolated from raw milk in our previous study was used in this study. Other three phages, vB_Eco-RN12i1, vB_Kpn-RN14i1, and vB_Ssc-RN20i3, were isolated from wastewater using E. coli 5823, K. pneumoniae 194, and Staphylococcus sciuri MM01 as hosts, respectively. The host range and efficiency of plating (EOP) were determined following phage isolation. Moreover, the lysis activities of these phages against their hosts were investigated in pasteurized milk using a multiplicity of infections (MOIs) of 10 and 100 at 37°C. Phages were applied using individual and combination phages. Results: According to the EOP results, all phages showed high specificity to their respective hosts. They are tailed phages with distinct morphologies. Individual phage treatments in spiked pasteurized milk with their respective bacterial hosts significantly reduced the bacterial counts in both MOI conditions during the first 2 h of the treatment (approximately 1-8 log reduction compared to the control). Although these phages specifically infected only their hosts, the phage cocktail resulted in a better result compared to the use of individual phage. However, bacterial regrowth was observed in all experiments, which may be related to the development of phage-insensitive mutants. Conclusion: Our findings suggest that the application of phages could be used to treat bovine mastitis. Phage cocktail is suitable to promote the efficacy of phage treatment in pasteurized milk. However, when considering the use of phages in dairy cows, certain phage properties in raw milk and in vivo and ex vivo should be highlighted to ensure their effectiveness as biocontrol agents for bovine mastitis treatment.