Abstract
Few reports from Africa suggest that resistance pattern, virulence factors and genotypes differ between Staphylococcus aureus from nasal carriage and clinical infection. We therefore compared antimicrobial resistance, selected virulence factors and genotypes of S. aureus from nasal carriage and clinical infection in Southwest Nigeria. Non-duplicate S. aureus isolates were obtained from infection (n = 217) and asymptomatic carriers (n = 73) during a cross sectional study in Lagos and Ogun States, Nigeria from 2010–2011. Susceptibility testing was performed using Vitek automated systems. Selected virulence factors were detected by PCR. The population structure was assessed using spa typing. The spa clonal complexes (spa-CC) were deduced using the Based Upon Repeat Pattern algorithm (BURP). Resistance was higher for aminoglycosides in clinical isolates while resistances to quinolones and tetracycline were more prevalent in carrier isolates. The Panton-Valentine leukocidin (PVL) was more frequently detected in isolates from infection compared to carriage (80.2 vs 53.4%; p<0.001, chi2-test). Seven methicillin resistant S. aureus isolates were associated with spa types t002, t008, t064, t194, t8439, t8440 and t8441. The predominant spa types among the methicillin-susceptible S. aureus isolates were t084 (65.5%), t2304 (4.4%) and t8435 (4.1%). spa-CC 084 was predominant among isolates from infection (80.3%, n = 167) and was significantly associated with PVL (OR = 7.1, 95%CI: 3.9–13.2, p<0.001, chi2- test). In conclusion, PVL positive isolates were more frequently detected among isolates from infection compared to carriage and are associated with spa-CC 084.
Highlights
Staphylococcus aureus is a versatile human pathogen causing infections ranging from relatively mild skin and soft tissue infections to life threatening sepsis, pneumonia, osteomyelitis, endocarditis as well as toxin mediated diseases such as toxic shock syndrome and food poisoning
This holds true for the Panton-Valentine leukocidin (PVL) which is highly prevalent in S. aureus from infection but is less frequently found in isolates from colonization in Africa [7]
A total of 290 S. aureus isolates were obtained from asymptomatic carriers (n = 73) and clinical infections (n = 217)
Summary
Staphylococcus aureus is a versatile human pathogen causing infections ranging from relatively mild skin and soft tissue infections to life threatening sepsis, pneumonia, osteomyelitis, endocarditis as well as toxin mediated diseases such as toxic shock syndrome and food poisoning. It is usually a colonizer of about one third of healthy humans and is most likely found in the nares, in the posterior vestibules [1]. Several studies have characterized S. aureus isolates from Nigeria but very few have compared the virulence genes and genotypes of isolates from infection and carriage in one study. PVL can be associated with skin and soft tissue infection but its role in the pathogenesis of disease remains controversial [8,9]
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