Methicillin Resistance and Biofilm Formation of Staphylococcus epidermidis in Blood Culture Isolates from Children under Five: A Multicenter Study in Nigeria

Abstract

The clinical impact of Staphylococcus epidermidis in bacteremia remains controversial. The aim of this study is to determine the methicillin resistance and biofilm formation of S. epidermidis isolates. A total of 102 S. epidermidis blood culture isolates from children under five attending seven selected hospitals in north-central and northwest Nigeria within 2009 to 2016 were analyzed for methicillin resistance using cefoxitin disk agar diffusion test. Phenotypic biofilm formation and molecular detection of the intercellular adhesion locus (icaA) gene was performed by the quantitative Microtitre Plate (MTP) method and conventional Polymerase Chain Reaction (PCR) respectively. Seventy-four (72.5%) Methicillin-Resistant Staphylococcus epidermidis (MRSE) was observed while biofilm formation was detected in 20 (19.6%) S. epidermidis isolates. The icaA gene positive and negative S. epidermidis were 22.5% (23/102) and 77.5% (79/102) respectively. In correlating the biofilm formation using MTP method and icaA gene detection, 19.6% were biofilm producers and icaA positive while 2.9% carried the icaA gene but did not produce biofilm on the tissue culture plate. Out of the icaA positive S. epidermidis, 91.3% were MRSE while 69.6% were MRSE among the icaA negative strains. Methicillin-Resistant Staphylococcus epidermidis is common and the majority of the biofilm-producing strains were highly resistant to methicillin. This suggests a close association between biofilm-formation in S. epidermidis with increased methicillin resistance.