Antimicrobial susceptibility profiles of Staphylococcus spp. contaminating raw goat milk

Abstract

Background and Aim: Antimicrobial resistance poses a major threat to global public health. Foodstuff of animal origin can serve as potential vehicles for the dissemination of antimicrobial-resistant bacteria and resistance genes to consumers. In view of the lack of knowledge about antimicrobial resistance in bacteria associated with goat milk, the aim of this study was to report species-level identification and antimicrobial susceptibility profiles of a large collection of Staphylococcus spp. isolates recovered from raw goat milk in Brazil. Materials and Methods: A total of 434 Staphylococcus spp. isolates originated from 510 goat milk samples in Northeast Brazil were investigated. The isolates were obtained by conventional microbiological methods. Species identification and antimicrobial susceptibility testing were performed by means of a semi-automated system using a panel for biochemical tests and broth microdilution method for 19 antimicrobial drugs. Results: Although Staphylococcus aureus (22.6%) accounted for the majority of the isolates, a total of 13 different non-aureus staphylococci spp. were identified. High resistance rates against erythromycin (40.8%), and the beta-lactams ampicillin (45.9%) and penicillin (42.9%) were observed among S. aureus isolates. The most significant findings were related to the resistance against quinupristin-dalfopristin, a drug of last resort used in human medicine to treat infections caused by vancomycin-resistant S. aureus and enterococci. Conclusion: The high diversity of Staphylococcus spp. showing phenotypic resistance against different antimicrobial drugs encourages further investigations on the real impact of these bacteria as reservoirs of antimicrobial resistance genes to consumers. Furthermore, the potential impact of technological processes, such as pasteurization, fermentation, and maturation, on the maintenance and dissemination of antimicrobial resistance among the microbial populations in milk and dairy products must also be investigated.

The first study on antimicrobial resistance of Staphylococcus aureus isolated from raw goat milk associated with subclinical mastitis in Siliragung Subdistrict, East Java, Indonesia

“…Based on our study, P was identified as the most resistant among the antibiotics tested and recorded at 81.82%, which is higher than that reported by Jamali et al [20] and Silva Júnior et al [14]. In contrast, NO was identified as the most sensitive among the antibiotics tested and recorded at 95.60%, followed by CIP (86.88%).…”

“…The results of the study showed that the prevalence of S. aureus in Siliragung Subdistrict, Banyuwangi District, Indonesia, was 25.58%, which is higher than that reported in previous studies in Shaanxi, China (23.53%) [24] and the Oromia Region, Ethiopia (16.6%) [5]. However, it is slightly similar to a previous report from Northeast Brazil, which recorded a rate of 22.6% [14]. This high prevalence of subclinical mastitis may be due to improper farming management systems, such as poor milking management, poor environmental sanitation, and conventional milking procedures that lead to S. aureus transmission among dairy goats [18][19][20][21].…”

“…However, the prerequisites for the prevention of bacterial transmission at farm or industry levels depend on identifying not only Staphylococcus spp. but also all causative agents of mastitis, with the priority being antibiotic susceptibility patterns [14].…”