Virulence genes and genotypes of Staphylococcus aureus from blood of Thai patients

Abstract

Staphylococcus aureus is the most common cause of nosocomial fevers. We investigated the virulence genes and genotypes of S. aureus strains isolated from bloodstream infections of patients in a Thai teaching hospital. Thirtythree methicillin-resistant S. aureus (MRSA) and 52 methicillin-susceptible S. aureus (MSSA) collected during 1997-1998, and 29 MRSA and 52 MSSA strains collected during 2010-2011 were studied. Susceptibility to 8 antimicrobials was determined using an agar dilution method. Twelve virulence genes were detected by polymerase chain reaction. The bacterial strains were typed by SCCmec, agr, spa, and multilocus sequence typing. The majority of the MSSA isolates were susceptible to almost all antimicrobials tested, whereas the MRSA isolates were resistant to more than 3 of the antimicrobials tested. The hla-sea was the most common virulence gene profile in the MRSA isolates from both periods (46% in 1997-1998, 31% in 2010-2011), and hla alone was the most common pattern in the MSSA isolates (56% in 1997-1998, 35% in 2010-2011). The S. aureus isolates in 2010-2011 contained more virulence gene profiles than those in 1997-1998. All MRSA isolates from 1997-1998 carried SCCmec III-agr I, whereas those in 2010-2011 carried SCCmec III-agr I (48%) and SCCmec type II-agr II (31%). No specific virulence genes or genotypes of the isolates related to a poor clinical outcome were found.

Phenotypic and Genotypic Detection of Antimicrobial Resistance and Virulence Factors among Staphylococcus aureus Clinical Isolates

“…Among them 77 strains (91.7%) carried hla gene. Similar hla gene prevalence rates were detected [25][26][27]. On the other hand, lower prevalence rate (37.3%) was detected by Rasmi et al [28].…”