Vaginal colonization with virulent Staphylococcus aureus and methicillin resistant Staphylococcus aureus among Ugandan women in labour

Abstract

Abstract Background Staphylococcus aureus (S. aureus) often colonizes the human skin, upper respiratory and genital tracts. In the female genital tract, it can be passed on to the newborn during vaginal delivery leading to either ordinary colonization, or neonatal infections notably umbilical stump sepsis, scalded skin syndrome, arthritis, or bactereamia/sepsis. These infections are mediated by Staphylococcal virulence factors such as i. Staphylococcal Enterotoxins A, B, C, D, and E encoded by the sea, seb, sec, sed, see genes, ii. Exfoliative Toxins A and B encoded by the eta and etb genes, iii. Toxic Shock Syndrome Toxin 1 (TSST-1) encoded by the tst gene, iv. Panton-Valentine Leukocidin (PVL) encoded by the pvl gene, and v. Hemolysins alpha and delta encoded by the hla and hld genes, respectively. We determined the prevalence of S. aureus possessing one or more virulence factor genes and of methicillin resistant Staphylococcus aureus (MRSA) in this population.Methods This was a descriptive cross-sectional study, which used 85 retrieved cryopreserved S. aureus isolates from the Chlorohexidine (CHX) clinical trial in Uganda. The isolates had been obtained by culturing vaginal swabs (VS) from 1472 women in labour. Isolates were thawed and sub-cultured. These were studied for selected virulence and methicillin resistance genes (mecA) using molecular techniques. Data were analysed using SPSS version 20.Results Of the 85 S. aureus isolates 13 (15.3%) were positive for one or more virulence factor genes, as follows: pvl 9/85 (10.6%), hld 5/85 (5.9%), sea 1/85 (1.2%) and seb genes 1/85 (1.2%). The other virulence genes (sec, sed, see, eta, etb, hla and tst) were not detected in any of the isolates. MRSA was detected in 55.3% (47/85) of the isolates, but only two of these carried the pvl virulence gene.Conclusion This study demonstrated that 15% of the S. aureus colonizing the female lower genital tract of mothers in labour in central Uganda carried one or more virulence genes, mostly pvl. More than half of the isolates were MRSA but mostly avirulent. Therefore, in the study settings, the potential for newborn infection with virulent S. aureus stands, but with non-MRSA strains.