Molecular Investigation of Methicillin-Resistant Staphylococcus aureus Strains Recovered from the Intensive Care Unit (ICU) Based on Toxin, Adhesion Genes and agr Locus Type Analysis

Staphylococcus aureus, as one of the most common causes of nosocomial infections, has widely spread to all parts of the world and is becoming a serious concern in public health.
The present study aimed at evaluating the prevalence of adhesion and toxin gene profiles and their distribution among different agr types.
The current cross-sectional study was performed in Tehran, Iran, by analyzing 125 methicillin resistant Staphylococcus aureus (MRSA) strains isolated from hospitalized patients at the ICUs from March, 2016 to January, 2017. In vitro antibiotic susceptibility testing of isolates was assessed using the Kirby-Bauer disk diffusion method. The MRSA strains were genetically typed by agr typing and virulence and adhesion genes profile by conventional PCR.
Antibiotic susceptibility testing showed that inducible macrolide-lincosamide-streptogramin B, constitutive macrolide-lincosamide-streptogramin B, and high-level mupirocin resistance phenotypes had a frequency of 18 (14.4%), 50 (56%), and 10 (31.3%), respectively. The predominant resistance profile among MDR-MRSA isolates included resistance profile to seven antibiotics (32%). A total of ten virulence genotypes were observed, from which genotype spa, clfA, clfB, fnbB, fnbA, ebp, and can / tst (36%, 45/125) comprised the majority followed by spa, clfA, clfB, and fnbB (24%, 30/125). Type I was the most prevalent agr type (52%), followed by type III (34.4%), type II (9.6%), I 5(5.3%), and IV (4%). All isolates carrying PVL-encoding genes and HLMUPR-MRSA strains corresponded exclusively to agr type I.
The current data demonstrated that virulence gene profiles among different agr types of MRSA isolates were divers. The present study suggests that molecular characterization of MRSA strains should periodically be studied.