Phenotypic and phylogenetic relatedness of selected Staphylococcus aureus strains cultured from HIV seropositive mothers and their neonate's pair

Abstract

Background: Staphylococcus aureus is a major pathogen to man and is invasive when the skin is breached as well as in trauma. The frequency and transmission of S. aureus was determined in high vaginal swabs (HVS), oropharynx, and breast milk of human immunodeficiency virus (HIV)-seropositive women to their neonates at healthcare centres, Ondo State, Nigeria between November 2014 and December 2015. Materials and Methods: A total of 114 HIV pregnant women were screened for S. aureus isolates in the HVS, oropharynx, and breast milk employing sterile cotton tipped applicator. The swabs were subsequently introduced into sterile thioglycollate medium and incubated at 37°C for 24 h. When growth was noticed, a loopful was introduced onto freshly prepared mannitol salt agar (MSA). Colonies of cocci that fermented mannitol on MSA were presumptively deemed as S. aureus, but confirmed as S. aureus isolates by the slide and tube agglutination tests in pooled human plasma. HIV seropositivity was determined by the HIV1/2 strip (Determine Test, Alere, London, England, UK) and confirmed as such by enzyme-linked immunosorbent assay (Abbot laboratories, Chicago, USA). Phenotypes were determined by susceptibility testing and phylogenetic relatedness by random amplified polymorphic DNA polymerase chain reaction. Results: Results showed that 50 (43.85%) were colonized by S. aureus; however, 4 (8%) showed mother-to-child transmission from the three sites. Although all isolates tested were resistant to nalidixic acid and penicillin, 93.75% of isolates were sensitive to imipemen. Conclusion: The study revealed a high frequency of colonization of S. aureus in HVS (64%), oropharynx (20%), and breast milk (16%). Horizontal transmission from mother to neonate was 8% while phylogroups showed similarities in genetic relatedness.