Molecular analysis and frequency of Staphylococcus aureus virulence genes isolated from bloodstream infections in a teaching hospital in Tianjin, China

Abstract

ABSTRACT. Staphylococcus aureus is an important cause of bloodstream infections worldwide. We examined the prevalence of genes that encode erythromycin ribosome methylase and bacterial toxins in S. aureus collected from bloodstream infections. Sixty different S. aureus isolates were obtained from blood cultures of patients who were admitted to a Teaching Hospital in Tianjin from January 2006 to August 2011. The susceptibility of the isolates to 16 antibiotics was tested. Methicillin-resistant S. aureus (MRSA) was identified using the disk diffusion method with cefoxitin. PCR was used to detect genes that encode the staphylococcal enterotoxins, Panton-Valentine leukocidin, toxic shock syndrome toxin 1 and erythromycin ribosome methylase. Molecular analysis of the MRSA strains was done using pulsed-field gel electrophoresis (PFGE) and staphylococcal cassette chromosome mec (SCCmec) typing. The positivity rates of mecA, ermA, ermB, and ermC in the isolates were 13/60, 10/60, 18/60, and 18/60, respectively. Among the ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 12 (1): 646-654 (2013) Virulence genes of Staphylococcus aureus 647 60 isolates, 30 harbored enterotoxin genes, with sea as the most frequent toxin gene (33%), followed by sec (15%), sed (12%), and seb (5%). The see and tst genes were not found in any of the isolates. The pvl gene was detected in four strains. Eleven MRSA isolates were of the SCCmec type III; two MRSA isolates could not be determined through SCCmec typing. PFGE analysis of the 13 MRSA isolates produced 8 distinct pulsotypes. Virulence genes and erythromycin ribosome methylase genes were highly prevalent in these isolates. The PFGE results demonstrated that the MRSA spread through cloning, mainly involving SCCmec type III.

Detection of enterotoxins and genotyping of Staphylococcus aureus strains isolated from Isfahan Educational Hospital, Iran

“…Also in Wang et al study the sea gene was found with 33%, and followed by sec with 15%. Our results were similar to other investigators, however the percentage of sea and sec genes in some studies are different (20).…”

Analysis of Virulence Genes Among Methicillin Resistant Staphylococcus aureus (MRSA) Strains

“…The frequency of the sea gene of MRSA was 58.8% in Gorgan of Iran (38), 33% China (39), 15.78% Canada, (19), 74.4% Tehran of Iran (40), 12% Germany (41), 17.5% Malaysia, (13), 32.07% Tehran of Iran (42), 27% Korea (43), 12% Czech (44) and 30% Turkey (45). In a study carried out in Colombia, among the 30 MRSA isolates, the nil gene of sea was not reported (27).…”

“…Moreover, the frequency of the seb gene has been investigated by many studies. Frequency of this gene in blood specimens in Gorgan of Iran (38), China (39), Canada (19), Tehran (42), Korea (43), Czech (44), Colombia (26) were 61.3%, 5%, 15.78%, 73.58%, 5.6%, 3%, and 7%, respectively. In our study, the frequency of the seb gene was 10.95%.…”

Molecular Detection of Staphylococcus aureus Enterotoxin A and B Genes in Clinical Samples from Patients Referred to Health Centers in Zahedan City

“…Nashev et al reported the most abundant enterotoxin is enterotoxin A (23%) in S. aureus isolates from nasal samples (11). The most common enterotoxin coding gene in their study was sea with a prevalence of 33%, followed by sec with 15% prevalence (12). A Turkish investigation showed that only 2.9% of 70 S. aureus strains tested were positive for sea gene while there were no positive results for other putative genes (13,14,15,16).…”