Species identification and antimicrobial susceptibility profile of bacteria associated with cow mastitis in southern Brazil

Abstract

Bovine mastitis is the most common disease in dairy cattle and responsible for economic losses in the milk industry. The present study aimed to identify the main species and to evaluate the antimicrobial susceptibility of bacterial isolates from cow herds with mastitis in dairy farms from southern Brazil. A total of 107 milk samples were collected from different cow herds in one important dairy producing region in southern Brazil, including farms located in ten cities from the Northeast region in the Rio Grande do Sul state. Bacterial strains were isolated and submitted to presumptive identification by classical bacteriological methods. Bacterial species were also identified by MALDI-TOF MS and antimicrobial susceptibility testing was performed with 12 antimicrobials commonly used in dairy farms. Fifty-one bacterial strains were isolated and the presumptive identification demonstrated the occurrence of Staphylococcus spp. (82.3%), Bacillus spp. (3.9%), Klebsiella spp. (3.9%), Streptococcus spp. (3.9%), Corynebacterium sp. (2%), Enterococcus sp. (2%) and Serratia sp. (2%). Forty-one isolates were successfully identified in the MALDI-TOF analysis, including 35 isolates from eleven different bacterial species. Importantly, there were eight different Staphylococcus species, with a high frequency of Staphylococcus chromogenes (48.6%) and Staphylococcus aureus (20%). Overall, bacterial isolates demonstrated resistance to penicillin (46.3%), tetracycline (39%), amoxicillin (36.6%), ampicillin (34.1%) and sulfamethoxazole/trimethoprim (31.7%). Enrofloxacin was the unique antimicrobial that all isolates were susceptible. In addition, there were six multidrug resistant isolates (five S. chromogenes and one S. aureus). This study highlights that bacterial pathogens with resistance to several antimicrobials were identified in cows from dairy farms in a very important milk producing region located in southern Brazil. Microbial identification of the bovine mastitis pathogens and determination of the antimicrobial profile is necessary for the rational use of the medicines.

Environmental Bovine Mastitis Pathogens: Prevalence, Antimicrobial Susceptibility, and Sensitivity to Thymus vulgaris L., Thymus serpyllum L., and Origanum vulgare L. Essential Oils

“…Contrary to our findings, the prevalence of this mastitis-associated pathogen may be even higher than 20% [ 8 , 31 ]. In addition, the prevalence of S. marcescens was higher than those reported in China [ 29 ], Iraq [ 32 ], Brazil [ 33 ], and Japan [ 34 ]. Interestingly, according to Bannerman et al [ 9 ], the mild clinical symptoms displayed during mastitis—as well as the finding that this pathogen is shed in low numbers—complicates the ability to identify Serratia spp.…”

“…Despite the fact that S. marcescens isolates from cow’s milk are usually sensitive in vitro to antibiotics, their use in the treatment of mastitis does not produce satisfactory results and is not recommended. Even in the cases of using the correct treatment, the bacteriological elimination rate is low, with poor responses to antimicrobial therapy [ 33 ]. Signs of improvement can be noticed but this condition is mostly temporary, and the cure rate is less than 14% [ 8 , 50 ].…”