Age- and Gender-Associated Staphylococcus aureus spa Types Found among Nasal Carriers in a General Population: the Tromsø Staph and Skin Study

Abstract

Staphylococcus aureus nasal carriers risk autoinfection; however, knowledge about the factors that make specific strains successful colonizers is limited. This study was undertaken to identify the most successful S. aureus clones in nasal carriers and compare their distribution among host groups. The population structure of S. aureus isolates from healthy adults was investigated by spa typing 1,981 isolates from persistent and intermittent nasal carriers participating in a health survey. In the baseline screening (1,113 isolates), the most common spa types were t012 (8.4%), t084 (7.6%), and t065 (4.9%). Three large spa clonal complexes (spa CC012, spa CC065, and spa CC084) comprised 62.4% of the isolates. In multivariate models adjusted for age and smoking status, male sex was associated with higher risk for spa type t084 (odds ratio [OR], 1.72; 95% confidence interval [CI], 1.06 to 2.77), and lower risk of spa type t012 (OR, 0.60; 95% CI, 0.39 to 0.92) colonization. The prevalence of spa type t012 decreased significantly with increasing age (P ‫؍‬ 0.03), with a prevalence almost twice as high in the youngest group (age 30 to 44 years, prevalence ‫؍‬ 11.1%) as in the oldest group (age, 60 to 87 years; prevalence ‫؍‬ 5.6%). Among baseline isolates, spa type t084 had a twofold-higher prevalence among intermittent carriers than among persistent carriers (10.6% versus 5.5%; P ‫؍‬ 0.04). In summary, the two most prevalent spa types found in this study were significantly associated with age and/or gender. This may provide valuable clues to the multifactorial mechanisms, among them bacterial factors, involved in nasal colonization with S. aureus.

Infection control of Staphylococcus aureus : spa typing to elucidate transmission

“…Gender-specific spa types have been identified previously (Sangvik et al 2011). The study demonstrating this correlation was, however, larger than ours.…”

“…There are indications that the immune defense is somehow boosted by female sex hormones (Marriott & Huet-Hudson 2006). This could explain the lower S. aureus colonization rates among females compared to males described in paper III and previous studies (Bischoff et al 2004;Herwaldt et al 2004;Sangvik et al 2011) as well as why the association between colonization and carriage status and serum concentration of vitamin D was more prominent among males (Olsen et al 2012). Due to the few hours of sun-light during the winter in Scandinavia, low serum concentrations of vitamin D, and thereby a higher prevalence of S. aureus, can be expected during this period.…”

“…The procedure of using an enrichment broth prior to plating (paper IV) revealed colonization rates ranging from 51 % to 70 % among adults. A gender-associated difference in colonization, with males being more frequently colonized compared to females, has been demonstrated in previous studies (Bischoff et al 2004;Herwaldt et al 2004;Sangvik et al 2011;Olsen et al 2012). Initially, the reason for this association was unknown and scarcely studied (Bischoff et al 2004).…”

“…In the same study, t084 was not detected at all (Matussek et al 2007) which could indicate that the molecular epidemiology of S. aureus is somewhat dynamic. t084 has recently been described as one of the most common spa types in studies both from northern Norway and Nigeria (Sangvik et al 2011;Kolawole et al 2013;Olsen et al 2013).The high prevalence of t084 both among adults and infants indicates that it is highly transmittable and a successful colonizer. S. aureus of spa type t084 was also the predominant colonizing type, but also the cause of four cases of bacteremia, in the neonatology department in one of the hospitals participating in the Swedish HITS study (paper III).…”

Epidemiological and molecular biological studies of multi-resistant methicillin-susceptible Staphylococcus aureus

“…spa type t084 is one of the most frequently found spa types among MSSA worldwide. In a study from Norway on 1113 MSSA isolates, t084 was shown to be the second most common spa type detected (7.6 %) [152]. Similarly, t084 is the second most abundant MSSA clone causing invasive infections in Europe [153].…”