Molecular characterization of coagulase-negative staphylococci isolated from neonates with sepsis at Mwananyamala regional referral hospital

Abstract

ABSTRACT Background: Coagulase-negative staphylococci (CoNS) have emerged as pathogenic bacteria causing bloodstream infection (BSI), particularly in people with immature immune status such as neonates. Single set of blood culture is collected in neonates hence becomes difficult to distinguish non-pathogenic and pathogenic CoNS. Their capacity to form biofilm is regarded as the major virulence mechanism that facilitates pathogenicity, horizontal gene transfer and impairs penetration of antimicrobial agents and immunologic response. Broad objective: To determine virulence genes (VGs) (icaA, icaB, icaC, and icaD) and antibiotic resistance genes (ARGs) (blaZ, mecA, and aac(6’)-Ie-aph(2’’)-Ia) expressed by CoNS isolated from neonates with sepsis at Mwananyamala Regional Referral Hospital (MRRH). Methodology: A cross-sectional laboratory-based study was carried out from January to June 2024, using archived CoNS isolated from neonates with sepsis previously admitted at MRRH. VITEK® MS was used for speciation, and Polymerase Chain Reaction was performed for detection of VGs and ARGs. Amplicons were separated by Agarose gel electrophoresis and bands were visualized by Molecular Imager Gel Doc XR. Statistical analysis was performed using Statistical Package for Social Science software version 23.0. Descriptive statistics such as frequency tables were computed to describe categorical variables which were species, virulence genes, and ARGs distribution among the isolates. Results: A total of 70 archived CoNS isolates were included in the study. Out of 70 CoNS six different CoNS species were identified with S. epidermidis 27 (36.8%) being the predominant isolate followed by S. haemolyticus 24 (34.3%). Virulence genes responsible for biofilm formation (ica genes) were detected, of which 90% of CoNS species harbored all ica genes (icaADBC) in the ica locus and were considered as pathogenic species. A high proportion 61 (87.1%) of CoNS isolates harbored all three ARGs against the commonly prescribed antibiotics, where mecA 69 (98.6%) was the most prevalent gene detected followed by blaZ 67 (95.7%). Conclusion and recommendation: This study reveals CoNS species causing neonatal sepsis are predominantly S. epidermidis followed by S. haemolyticus and that most of them (90%) are pathogenic with a high carriage of ARGs blaZ, mecA, and aac ( 6’)-Ie-aph(2’’) Ia which confer resistance to the most commonly prescribed antibiotics including penicillin, methicillin, and gentamycin respectively.