Methicillin-susceptible Staphylococcus aureus endocarditis isolates are associated with clonal complex 30 genotype and a distinct repertoire of enterotoxins and adhesins

Abstract

Background: Using multinational collections of methicillin-susceptible Staphylococcus aureus (MSSA) isolates from infective endocarditis (IE) and soft tissue infections (STIs), we sought to (1) validate the finding that S. aureus in clonal complex (CC) 30 is associated with hematogenous complications and (2) test the hypothesis that specific genetic characteristics in S. aureus are associated with infection severity.

Methods: IE and STI isolates from 2 cohorts were frequency matched by geographic origin. Isolates underwent spa typing to infer CC and multiplex polymerase chain reaction for presence of virulence genes.

Results: 114 isolate pairs were genotyped. IE isolates were more likely to be CC30 (19.5% vs 6.2%; P = .005) and to contain 3 adhesins (clfB, cna, map/eap; P < .0001 for all) and 5 enterotoxins (tst, sea, sed, see, and sei; P ≤ .005 for all). CC30 isolates were more likely to contain cna, tst, sea, see, seg, and chp (P < .05 for all).

Conclusions: MSSA IE isolates were significantly more likely to be CC30 and to possess a distinct repertoire of virulence genes than MSSA STI isolates from the same region. The genetic basis of this association requires further study.

Figure 1.

A, Specific virulence genes are significantly more common in methicillin-susceptible Staphylococcus aureus isolates from infective endocarditis (IE) compared with geographically matched methicillin-susceptible S. aureus isolates from soft tissue infection (STI). B, Specific virulence genes are significantly more common in clonal complex 30 (CC30) compared with non-CC30 methicillin-susceptible S. aureus. Genes listed are statistically significant after adjustment for multiple comparisons using a false discovery rate of 10%.