Distribution of Adhesion and Toxin Genes in Staphylococcus aureus Strains Recovered From Hospitalized Patients Admitted to the ICU

Abstract

Background: Methicillin-resistant Staphylococcus aureus (MRSA) strains are a common cause of emerging nosocomial infections and are a major public health concern. Objectives: The aim of the present study was to determine the prevalence of MRSA, its antibiotic resistance pattern, and the virulence gene profiles in hospitalized patients admitted to ICUs. Methods: During a 6-month period, a total of 70 S. aureus isolates were collected from 249 patients admitted to the ICU in five hospitals. In vitro antibiotic susceptibility testing of the S. aureus isolates was carried out using the Kirby-Bauer disk diffusion method with 16 antibiotic disks. Molecular detection of toxin and adhesion genes was carried out using PCR. Results: All the 70 S. aureus isolates were confirmed to be MRSA strains. The largest number of S. aureus isolates was found in the blood (42.9%) and wound (21.4%) samples. The MDR pattern was detected in 71.4% of the isolates, which were obtained from wound and blood samples. Simultaneous resistance to seven, six, five, four and three drugs was common in 35 (50%), 7 (10%), 8 (11.4%), 11 (15.7%), 2 (2.9%) and 5 (7.1%) isolates, respectively. The frequency of the spa, fnbB, fnbA, clfB, clfA, can, bbp, ebp, etb, eta, pvl, and tst genes was 100%, 75.7%, 74.3%, 78.6%, 71.4%24.3%, 0%, 58.6%, 2.9%, 7.1%, 21.4%, and 51.4%, respectively. In addition, among all the examined genes, the clfB (78.6%) and etb (2.9%) genes had the highest and lowest prevalence respectively. Conclusions: In the present study, we found a high prevalence of MRSA at the hospitals studied. The findings emphasized the increased prevalence of MRSA isolates containing different toxin and adhesion genes, probably accompanied by antimicrobial resistance. Infection with such isolates worsens the clinical outcomes as well as the morbidity and mortality rates in hospitalized patients in ICUs.