Occurrence of Virulence Genes among Methicillin-Resistant Staphylococcus aureus Isolated from Subclinical Bovine Mastitis

Maryam Shahid; Riaz Hussain; Zeeshan Nawaz; Bilal Aslam; Muhammad Zishan Ahmad; Abu Baker Siddique; Hira Ahsan; Aiman Fatima; Iahtasham Khan; Bilal Mustafa; Rashid Iqbal; Khalid M Al Syaad; Ashwag Shami

doi:10.1021/acsomega.3c04206

Occurrence of Virulence Genes among Methicillin-Resistant Staphylococcus aureus Isolated from Subclinical Bovine Mastitis

ACS Omega. 2023 Oct 2;8(41):38111-38117. doi: 10.1021/acsomega.3c04206. eCollection 2023 Oct 17.

Authors

Affiliations

¹ Institute of Microbiology, Government College University, Faisalabad 38040, Pakistan.
² Department of Pathology, Faculty of Veterinary and Animal Sciences, The Islamia University of Bahawalpur, Bahawalpur 63100, Pakistan.
³ Department Veterinary Pathology, Faculty of Veterinary and Animal Sciences, PMAS Arid Agriculture University Rawalpindi, Rawalpindi 46000, Pakistan.
⁴ Institute of Microbiology and Molecular Genetics University of the Punjab Lahore, Lahore 54590 Pakistan.
⁵ Section of Epidemiology and Public Health, Department of Clinical Sciences, University of Veterinary and Animal Sciences, Lahore Sub-Campus, Jhang 35200, Pakistan.
⁶ University of Oxford, Department of Biology, Wildlife Conservation Research Unit (WildCRU), Oxford Ox13 5QL, U.K.
⁷ Department of Agronomy, Faculty of Agriculture and Environment, The Islamia University of Bahawalpur Pakistan, Bahawalpur 63100, Pakistan.
⁸ Biology Department, College of Science, King Khalid University, Abha 61413, Saudi Arabia.
⁹ Department of Biology, College of Science, Princess Nourah bint Abdulrahman University, Riyadh 11671, Saudi Arabia.

Abstract

The occurrence of Staphylococcus aureus-induced subclinical mastitis holds significant implications for public health. This specific microorganism possesses a wide array of pathogenic factors that enable it to adhere to, colonize, invade, and infect the host. The objective of the current study was to assess the prevalence of S. aureus, determine antimicrobial resistance patterns, and identify virulence genes of methicillin-resistant S. aureus (MRSA) strains responsible for subclinical mastitis in bovines. A total of 249 milk samples were collected from various farms in the district of Faisalabad. The presence of subclinical mastitis was assessed by using the California mastitis test. Positive milk samples (n = 100) were then subjected to standard microbiological techniques for isolation and identification of S. aureus. Antibiogram analysis was conducted by using the disc diffusion method to assess antimicrobial resistance. For the molecular detection of S. aureus and its virulence genes, the polymerase chain reaction (PCR) was performed with species-specific primers. The overall prevalence of S. aureus was found to be 40% (40/100), which was confirmed through molecular detection of the nuc gene in 40/40 (100%) of samples using PCR. Antimicrobial susceptibility tests indicated the highest susceptibility to vancomycin, sulfamethoxazole/trimethoprim, erythromycin, gentamicin, ciprofloxacin, and chloramphenicol, while the highest resistance rate was observed against tetracycline. Additionally, 30% of samples (12/40) tested positive for methicillin resistance. PCR analysis revealed that 100% of MRSA-tested isolates harbored the mecA and clfA genes. Furthermore, the MRSA isolates showed the presence of pvl, hla, hlb, sec, icaA, icaD, icaB, and icaC genes at rates of 92, 75, 67, 42, 42, 75, 8, and 25%, respectively. These findings underscore the need for stricter aseptic control in dairy farms to prevent disease transmission between animals and ensure the production of safe and uncontaminated food for human consumption.