Prevalence of bovine mastitis-related pathogens, identified by mass spectrometry in flies (Insecta, Diptera) captured in the milking environment.

Diptera (Insecta) are able to transmit approximately 200 pathogenic microorganisms to humans and animals, causing more than 65 diseases, including bovine mastitis, which constitutes a major cause of economic losses in the dairy industry. In this scenario, 217 adult specimens of Diptera were collected from nine farms and identified to the family and/or species level. Of the 11 families recorded, Muscidae was the most prevalent (152 out of 217; 70%). All Diptera specimens were subjected to microbiological culture using conventional and selective media, and isolates were then identified at the species level by mass spectrometry. In total, 275 microorganisms were identified, with a predominance of pathogens related to environmental bovine mastitis (166/275 = 60·4%), that is, Enterococcus species (70/275 = 25·4%) and Escherichia coli (49/275 = 17·8%). Nontraditional agents related to bovine mastitis (called miscellaneous) were detected in 28% (77/275), as well as microorganisms with well-known zoonotic behaviour (e.g. Bacillus cereus). This is study contributes with knowledge of diversity of microorganisms carried by Diptera in the dairy environment, including pathogens associated with environmental and contagious bovine mastitis, and agents with human relevance. To our knowledge, a three-part chromogenic selective medium used to microbial culture of milk on farms was used for the first time to identification of pathogens in Diptera.

Species diversity and antimicrobial resistance patterns of Enterococcus spp. isolated from mastitis cases, milking machine and the environment of dairy cows.

The objectives were to study the diversity of Enterococcus spp. isolated from mastitis cases, milking equipment and the environment of dairy cows; and to determine in vitro resistance of isolates to antimicrobials that are relevant to human and animal health. Ten dairy farms were visited to collect samples from mastitis cases, faeces, bedding, aisles, water and milking equipment. Identification of Enterococcus at the species level and antimicrobial resistance testing was performed by MALDI-TOF and the disk-diffusion method, respectively. Of 365 isolates, Enterococcus hirae was the most prevalent, being more likely to be isolated from faeces than from milk (odds ratio (OR) = 39·2), liners (OR = 5·4) or bedding (OR = 2·2). Enterococcus saccharolyticus was the most prevalent in milk samples. The chances of isolating Enterococcus faecalis from milk were higher than from aisles (OR = 12·5), faeces (OR = 5·3), bedding (OR = 3·6) or liners (OR = 3·0). The odds of isolating Enterococcus faecium from faeces were higher than from liners (OR = 7·3), bedding (OR = 2·5) or aisles (OR = 2·4). Of 360 tested isolates, 1·9, 0·3 and 0·6% were resistant to penicillin, vancomycin and teicoplanin, respectively. Our results suggest that Enterococcus species can occupy specific ecological niches on dairy farms and pose a risk to public and animal health.