Characterization of colonizing Staphylococcus aureus isolated from surgical wards' patients in a Nigerian university hospital.

In contrast to developed countries, only limited data on the prevalence, resistance and clonal structure of Staphylococcus aureus are available for African countries. Since S. aureus carriage is a risk factor for postoperative wound infection, patients who had been hospitalized in surgical wards in a Nigerian University Teaching Hospital were screened for S. aureus carriage. All S. aureus isolates were genotyped (spa, agr) and assigned to multilocus sequence types (MLST). Species affiliation, methicillin-resistance, and the possession of pyrogenic toxin superantigens (PTSAg), exfoliative toxins (ETs) and Panton-Valentine Leukocidin (PVL) were analyzed. Of 192 patients screened, the S. aureus carrier rate was 31.8 % (n = 61). Of these isolates, 7 (11.5%) were methicillin-resistant (MRSA). The isolates comprised 24 spa types. The most frequent spa types were t064, t084, t311, and t1931, while the most prevalent MLST clonal complexes were CC5 and CC15. The most frequent PTSAg genes detected were seg/sei (41.0%) followed by seb (29.5%), sea (19.7%), seh (14.7%) and sec (11.5). The difference between the possession of classical and newly described PTSAg genes was not significant (63.9% versus 59.0% respectively; P = 0.602). PVL encoding genes were found in 39.3% isolates. All MRSA isolates were PVL negative, SCCmec types I and VI in MLST CC 5 and CC 30, respectively. Typing of the accessory gene regulator (agr) showed the following distribution: agr group 1 (n = 20), group II (n = 17), group III (n = 14) and group IV (n = 10). Compared to European data, enterotoxin gene seb and PVL-encoding genes were more prevalent in Nigerian methicillin-susceptible S. aureus isolates, which may therefore act as potential reservoir for PVL and PTSAg genes

Characteristics of the surgical patient cohort studied.

1<p>Data are no.(%) of participants unless otherwise indicated.</p

Characteristics of nasal and cutaneous <i>S. aureus</i> isolates.

1<p><i>spa</i>, staphylococcal protein A gene; <i>spa</i>CC, <i>spa</i> clonal complex inferred by BURP analysis; n, indicates number of isolates with similar identity for all characteristics tested;</p>2<p>MLST, multilocus sequence typing; CC, clonal complex; ST, sequence type;</p>3<p>PVL, Panton-Valentine leukocidin; pos., positive; neg., negative;</p>4<p>PTSAg/ET gene profile, pyrogenic toxin superantigen gene/exfoliative toxin gene profile; -, no PTSAg/ET gene detected;</p>5<p><i>agr</i>, accessory gene regulator type;</p>6<p>MSSA, methicillin-susceptible <i>S. aureus</i>; MRSA, methicillin-resistant <i>S. aureus</i>;</p>7<p>ND, not done; NT, not type able.</p

Results of testing 61 <i>S. aureus</i> isolates for staphylococcal PTSAg and ET genes by multiplex PCR.

1<p><i>sea</i>, staphylococcal enterotoxin A gene; <i>seb</i>, staphylococcal enterotoxin B gene; <i>sec</i>, staphylococcal enterotoxin C gene; <i>sed</i>, staphylococcal enterotoxin D gene; <i>see</i>, staphylococcal enterotoxin E gene; <i>tst</i>, toxin shock toxin gene; <i>seg-sei</i>, staphylococcal enterotoxin G and staphylococcal enterotoxin I genes; <i>seh</i>, staphylococcal enterotoxin H gene; <i>sej</i>, staphylococcal enterotoxin J gene; <i>eta</i>, exfoliative toxin A gene; <i>etb</i>, exfoliative toxin B gene; <i>etd</i>, exfoliative toxin D gene; <i>luk</i>S-PV and <i>luk</i>F-PV, Panton-Valentine leukocidin genes; <i>hlg</i>, gamma-hemolysin gene.</p