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Multilocus Sequence Typing and Molecular Detection of Phenol-soluble Modulin in Biofilm-positive Staphylococcus epidermidis Isolated from Paediatric Blood Culture

Grace A John- Ugwuanya, Stephen K Obaro, Busayo O Olayinka, Josiah A Onaolapo, Fatimah Hassan Hanga, Huda Munir and Paul D Fey

Aim: Staphylococcus epidermidis is a significant coagulase-negative staphylococci obtained from blood culture samples. However, there is limited information about phenol-soluble modulin (PSM), which is associated with virulence in S. epidermidis and its genetic relatedness in Nigeria. This study observed the presence of phenolsoluble modulin mec (psm-mec) gene and the multilocus sequence typing (MLST) of biofilm-positive Staphylococcus epidermidis (BPSE).

Method: Twenty-two biofilm-positive S. epidermidis isolates obtained from paediatric blood culture at three hospitals in north-west and north-central Nigeria were evaluated for the molecular detection of the psm-mec gene using conventional polymerase chain reaction (PCR). The biofilm formation was previously assessed by molecular detection of the intercellular adhesion (icaA) gene and the methicillin resistance using cefoxitin disk agar diffusion. Internal fragments of the respective seven housekeeping genes was sequenced for 21 BPSE strains and matched with the central MLST database.

Results: Out of 22 BPSE, only 4.5% had the psm-mec gene and it was methicillin resistant. About 91% methicillin resistance was observed among the psm-mec negative BPSE strains. Twenty-one BPSE strains were sequence type 1 (ST1) based on the MLST analysis of the seven housekeeping genes.

Conclusion: Considering the very low presence of psm-mec gene, the BPSE may be carrying the ß-type PSMs related to biofilm formation and dissemination, and not the cytolytic a-type PSMs common in the aggressive form of S. epidermidis. Phenol-soluble modulin methicillin resistance island-encoded peptide toxin is involved in sepsis related methicillin-resistant S. epidermidis. The strains are genetically related to each other.