Objective: To determine the phenotypic and genotypic characterization of the virulence and antimicrobial susceptibility of S. aureus.
Design: Descriptive study
Samples:175 raw goat milk samples
Procedures: A total of 87 S. aureus strains was isolated from goat with mastitis in north-west cost of Egypt. PCR technique was used to detect genes coding some virulence and antimicrobial properties while phenotypic antimicrobial susceptibility was determined by the disc diffusion method.
Results: Most S. aureus isolates were resistant to amoxycillin (89.7%), penicillin G (88.5%), and ampicillin (86%) while were less resistant to other members of β-lactam group as cefoxitin (17.2%) and ceftriaxone (10.3%).The lowest resistant rates were toward fluroquinolone group members; ciprofloxacin, levofloxacin and ofloxacin in rates 1.2%, 2.3% and 4.5%, respectively. Tetracycline showed the highest level of phenotypic resistance (34.6%) and prevalence of a tetK gene (39.1%). The virulence factors, spa and coa exhibited prevalence rate of 6.9% and 8%, respectively with significant relationship between them.
Conclusion and Clinical relevance: The problem of antimicrobial resistance needs strict measures to limit the indiscriminate use of antibiotics and concerted research efforts to limit the spread of resistant bacteria, which will negatively affect human health and control of the infectious diseases in both humans and animals.