Staphylococcus aureus is a common human commensal but carriage varies between e.g. geographic location, age, gender, ethnicity and body niche. The nares, throat and perineum are the most prevalent sites for carriage in the general adult population. Other sites of the skin and the intestine are also frequently colonised. Thus, a successful establishment is dependent on multiple factors. This review describes results from observational studies of S. aureus carriage and the influence bacterial, host and environmental/modifiable factors might have on the relationship.

A total of 91 consecutive clinical isolates of Staphylococcus aureus were collected at the Regional Hospital of Arkhangelsk, Russia, from May to December 2004, and examined for antimicrobial susceptibility, methicillin resistance and presence of Panton-Valentine leucocidin (PVL) genes. Epidemiological typing was performed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Methicillin-resistant S. aureus (MRSA) isolates were examined by staphylococcal cassette chromosome mec (SCCmec) typing. High-to-moderate rates of resistance to penicillin (beta-lactamase production; 93%), tetracycline (40%), erythromycin and clindamycin (32%) were observed. Forty out of ninety-one (44%) isolates were positive for PVL genes. Thirty-six (40%) PVL-positive methicillin-susceptible S. aureus (MSSA) strains were shown by PFGE and MLST typing (ST121, ST681, ST837) to be part of a nosocomial outbreak caused by clonal complex (CC) 121. PFGE, MLST and SCCmec typing revealed three MRSA clones. Sequence type (ST) 239-III (n=11), ST1097-III (n=1) and ST8-IV (n=3) belong to CC8 of epidemic multiresistant MRSA, whereas ST426-MRSA-IV/CC395 (n=1) has not been reported previously. All MRSA strains were PVL negative. The overall results underline the necessity of microbiological sampling, antimicrobial susceptibility testing, and epidemiological typing as a rational basis for antimicrobial treatment of S. aureus infections, and infection control measures to limit the spread of multiresistant MRSA and epidemic MSSA clones.

BackgroundStaphylococcus aureus cell wall anchored Serine Aspartate repeat containing protein D (SdrD) is a member of the microbial surface component recognising adhesive matrix molecules (MSCRAMMs). It is involved in the bacterial adhesion and virulence. However the extent of genetic variation in S. aureus sdrD gene within isolates from healthy carriers are not known. The aim of this study was to evaluate allelic variation of the sdrD gene among S. aureus from healthy nasal carriers.ResultsThe sdrD A region from 48 S. aureus isolates from healthy carriers were analysed and classified into seven variants. Variations in the sdrD A region were concentrated in the N2 and N3 subdomains. Sequence analysis of the entire sdrD gene of representative isolates revealed variations in the SD repeat and the EF motifs of the B repeat. In silico structural modelling indicates that there are no differences in the SdrD structure of the 7 variants. Variable amino acid residues mapped onto the 3D structure revealed that the variations are surface located, exist within the groove between the N2-N3 subdomains and distributed mainly on the N3 subdomain. Comparison of adhesion to keratinocytes in an in vitro cell adhesion assay, using NCTC 8325–4∆sdrD strains expressing the various sdrD gene variants, indicated a significant difference between only two complements while others showed no major difference in their adhesion.ConclusionsThis study provides evidence of sequence variations across the different domains of SdrD from S. aureus isolated from healthy nasal carriers. Proper understanding of these variations is necessary in the study of S. aureus pathogenesis.Electronic supplementary materialThe online version of this article (10.1186/s12866-018-1179-7) contains supplementary material, which is available to authorized users.

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