Detection of Some Virulence Factors in Staphylococcus aureus Isolated from Shahid Beheshti Hospital of Hamedan in the Years 2014-2015

Staphylococcus aureus is one of the most important nosocomial pathogens. Pathogenicity of this organism is attributed to various virulence factors such as surface adhesion proteins, the ability to produce toxins and enzymes, rapid development of drug resistance and biofilm formation. The present study was conducted to investigate some of the virulence factors of S. aureus isolates.

A total of 30 isolates of S. aureus were collected from clinical samples of patients hospitalized in Shahid Beheshti hospital of Hamedan. Identification of bacteria was done using biochemical (catalase, coagulase and DNase) and molecular (PCR) tests. Thereafter, antibiotic susceptibility of the isolates and their ability to produce hemolysin, beta-lactamase and biofilm were assessed using disk diffusion, blood agar medium, acidimetric and microtiter-plate tests, respectively.

Hemolysis activities of the isolates on sheep blood agar showed that 8 (26.66%), 14 (46.66%) and 15 (50%) out of 30 isolates, produced α-, ∂- and β-hemolysins, respectively. While, using human blood agar media, the prevalence of these toxins were 40%, 53.33% and 13.33%, respectively. Twenty one isolates (70%) were found to be beta-lactamase producer using the acidimetric test. Meanwhile, the results of antibiotic susceptibility test indicated that penicillin was the less effective antibiotic (90% resistance). However, none of the isolates was resistant to vancomycin. Moreover, regarding to biofilm formation, 14 (46.66%) isolates strongly produced biofilms.

The results of this study revealed high frequencies of the virulence factors among the examined S. aureus isolates, specially the ability of biofilm formation and antibiotic resistance.