Staphylococcus aureus nasal carriage ina Moroccan dialysis center andisolates characterization

Staphylococcus aureus, which has its ecological niche in the anterior nares, has been shown to

cause a variety of infectious diseases mainly for patients in hemodialysis units. We performed this

study to evaluate the prevalence of nasal S. aureus carriage among hemodialysis outpatients, to

determine the antimicrobial susceptibility of isolates, to characterize the virulence genes, and to

identify associated risk factors. Nares swab specimens were obtained from 70 outpatients on

hemodialysis between March and June 2010. Samples were plated immediately onto S. aureus

specific media and pattern of antibacterial sensitivity was determined using disk diffusion method

Polymerase chain reaction was used to detect nuc, mecA, and genes encoding staphylococcal

toxins. Medical record of patients was explored to determine S.aureus carriage risk factors. Nasal

screening identified 42.9% S. aureus carriers with only one (3.3%) methicillin-resistant S. aureus

isolate. Among the methicillin-susceptible S. aureus isolates, high rate of penicillin resistance

(81.8%) has been detected. The identified risk factors were male gender and age ? 30 years

Research of virulence factors showed a high genetic diversity among the 30 S. aureus isolates

Twenty-one (70%) of them had at least one virulence gene, of which 3.3% were Panton-Valentine

leukocidin (lukS/F-PV) genes. S. aureus carriage must be screened for at regular intervals in

hemodialysis patients. Setting up a bacterial surveillance system is one of the strategies to

understand the epidemiology of methicillin-resistant S. aureus, to guide local antibiotic policy and

prevent spread of antibiotic-resistant S. aureus