Screening of antibiotic resistance genes and virulence determinants of Staphylococcus aureus from skin infections

Abstract

BackgroundVirulent strains of Staphylococcus aureus (S. aureus) express a series of virulence factors which cause severe infections such as skin and soft tissue infections which can be life-threatening. Additionally, extensive antibiotic resistance among nosocomial pathogens has left limited choices for their eradication. Our objective was investigation of antibiotic resistance and virulence determinants of S. aureus from skin infections. Materials and methodsTwo-hundred non-duplicate S. aureus isolates were collected from skin infections. Antibiotic susceptibility profile was evaluated using disc diffusion and methicillin resistance was confirmed. Biofilm formation was assessed by microtiter tissue plate assay. Determinants of virulence factors including hlA-α, tsst-1, pvl, PSM's, eta and etb genes and also the mupirocin resistance mup A gene and class I integron were detected by PCR. MLST was performed for isolates containing the pvl gene. ResultsThe age range of patients included 12–76 years (mean ± SD = 56.34 ± 5.43). MRSA (70/200) were isolated significantly higher among ages>50 years (p < .001) but not significantly different between both genders (p = .112). Prior antibiotic consumption and hospitalization were significantly associated with MRSA (81.42%) and MDR (84.28%) isolation. The existence of int1 gene (44.5%) was significantly higher in multidrug-resistant (MDR) isolates (p < .001). Thirty-six (18%) MDR isolates carried the mupA gene. The existence of mupA gene was significantly associated with prior hospitalization (n = 33, 91.66%, p < .0001) and antibiotic consumption (n = 30, 83.33%, p < .001). Predominant virulence determinant included PSMα (61.5%), followed by tsst-1 (17.5%), hla-α (9.5%), pvl (2.5%), eta (2.5%) and etb (1%). The rate of strong biofilm producers (totally 25%) was not significantly different between MRSA and MSSA. The existence of PSM-α gene was significantly higher among strong biofilm producers compared to biofilm non-producers (p = .002). PFGE exhibited no genetic relation among strains. ConclusionVirulence factors of S. aureus from skin infections contributed in severity of infection and biofilm formation. MDR phenotype was more common among older patients with history of hospitalization and prior antibiotic consumption. Mupirocin resistance has emerged among MDR and MRSA isolates. Hence suitable control strategies must be performed to inhibit the spread of these strains in healthcare and community settings.