Abstract
ABSTRACT This study aims to detect the main virulence and antimicrobial resistance genes in Stapylococcus aureus from bovine mastitic milk as well as classifying them according to agr typing. A total of 55 strains from six dairy unities in the state of Rio de Janeiro were selected, of these 27.3% presented fbnA and 78,2% for fbnB genes, respectively. None of the strains tested were positive for cap5 gene, 3.6% were positive for cap8 gene. Additionally, 94.5% of strains had hlA gene and 89.1% had hlB gene while 67.3% of the strains had icaA gene and 87.3% had icaD gene. From these results it was possible to establish 12 different virulence profiles. Prevalence of agrII type was detected in 81.8% of the isolates. Concerning antimicrobial resistance evaluation, the studied strains were susceptible to all antibiotics tested except penicillin, 83.6% being resistant strains. None of the strains had mecA gene, however, 40% of the strains had blaZ gene. Associating virulence and resistance data made it possible to obtain 23 different profiles. This great diversity of strains shows wide array of bacterial strategies and the challenge of mastitis prevention in cattle. Despite antimicrobial susceptibility, these strains presented certain genes that allow its persistence in the herd.
Highlights
Milk production is considered one of the main agricultural activities in Brazil (Rigolin-Sá et al, 2014)
This study aims to characterize S. aureus isolated from cases of subclinical bovine mastitis in the State of Rio de Janeiro in order to establish virulence and resistance profiles as well as to classify agr typing
A total of 27.3% (15/55) were positive for fbnA gene and 78.2% (43/55) for fbnB gene, genes implicated in fibronectin production
Summary
Milk production is considered one of the main agricultural activities in Brazil (Rigolin-Sá et al, 2014). Mastitis is recognized as the main cause of economic losses in dairy industry due to reduced milk production in cows, increased expenditure due to treatment of cows and losses associated with withdrawal and disposal of affected milk during the infection period (Reshi et al, 2015). Mastitis represents a potential risk to consumer health through transmission of zoonotic agents, possibility of triggering allergies, changes in the balance of intestinal microbiota and selection of resistant bacteria in digestive tract from the use of antibiotics (Cassol et al, 2010). Several bacterial pathogens can cause mastitis, Staphylococcus aureus is one of prevalent etiologic agents of this disease in dairy cattle worldwide. Indiscriminate use of antimicrobials to combat mastitis has led to selection of resistant strains of Staphylococcus spp., undermining the efficacy of treatment. Limited success of antibiotic therapy may be due to the ability of S. aureus to invade and survive within different cell types found in the mammary gland including phagocytes such as fibroblasts, osteoblasts, and various epithelial cell types (Bur et al, 2013)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
