Molecular epidemiology and resistance patterns of MRSA in dairy systems of Basrah, Iraq: Evidence of zoonotic and environmental transmission | ||
| Microbes and Infectious Diseases | ||
| Articles in Press, Accepted Manuscript, Available Online from 07 October 2025 | ||
| Document Type: Original Article | ||
| DOI: 10.21608/mid.2025.417326.3148 | ||
| Authors | ||
| Maryam A. Abdul Ameer* ; Alyaa S. Jasim; Hasan M. Al Tameemi | ||
| Microbiology Department, College of Veterinary Medicine, Basrah University, Basrah, Iraq | ||
| Abstract | ||
| Background: Staphylococcus aureus is well documented as a serious foodborne and animal-origin germ, frequently implicated in bovine mastitis and subsequent contamination of raw milk. The present investigation examined the prevalence, antimicrobial resistance patterns, and molecular features of S. aureus found in both clinical and environmental samples. Methods: Samples comprised specimens from clinical and subclinical mastitis, raw milk, and hand swabs from milkers yielding a total of 237 specimens. After initial cultivation, S. aureus Identification was performed using culture, biochemical assays, VITEK analysis, PCR targeting the nuc gene, and MLST profiling. Results: Twenty isolates (8.43 percent) were identified and confirmed as S. aureus. The rate of isolation from subclinical mastitis was slightly higher, at 12.5 percent, than that from clinical cases, which reached 12.1 percent, whereas raw milk and hand swabs yielded rates of 5.0 percent and 5.6 percent, respectively. Remarkably, all confirmed strains were methicillin-resistant S. aureus (MRSA), demonstrated by phenotypic resistance to cefoxitin and oxacillin and high-level resistance to -lactams such as ampicillin and benzylpenicillin. Multilocus sequence typing (MLST) of seven representative isolates revealed the predominance of clonal complex 97 (CC97), including ST97 and its variant ST2826, across all sample types—mastitis, milk, and human hand swabs. Additionally, human-associated clones CC8 (ST2454) and CC5 (ST6) were identified in bovine and raw milk samples, suggesting potential human-to-animal cross-transmission. CC97 clones were geographically widespread across Abu Al-Khaseeb, Al-Zubair, Mtaiha, and Al-Garma, with Al-Zubair emerging as a potential clonal hotspot. Conclusion: These findings underscore the endemic circulation of MRSA—particularly CC97—within Basrah’s dairy ecosystem and highlight the zoonotic and food safety risks posed by unregulated antibiotic use, raw milk consumption, and inadequate farm hygiene. Continued surveillance, antimicrobial testing, and more importantly improving hygienic standards of milk processing are critically important. | ||
| Keywords | ||
| clinical mastitis; subclinical mastitis; Raw milk; sequence typing | ||
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