Antibiotic Susceptibility Patterns of Biofilm-producing Nosocomial Non-coagulase Staphylococcus Isolates from Clinical Sources in Iraq

Coagulase-negative staphylococci (CoNS), like S. epidermidis and S. haemolyticus, are skin commensals that can cause infections. Their biofilms increase resistance and persistence. This study assessed biofilm formation, antibiotic resistance, and genetic diversity of local CoNS using MLST to aid regional surveillance.

In this study, samples were collected, and the species were identified using the VITEK 2 Compact system. A Kirby-Bauer disc diffusion test was carried out to detect antimicrobial susceptibility, and the biofilm production was tested with a microtiter plate. Multilocus sequence typing (MLST) was performed, followed by data processing using the Oxford scheme to categorize the isolates.

Among 150 clinical samples, 13.3% were S. epidermidis and 20% S. haemolyticus. Coagulase-negative staphylococci (CoNS) showed 100% resistance to amoxiclav, cefoxitin, methicillin, amoxicillin, and ceftriaxone. High resistance (66–96%) was seen for several antibiotics, with 76% classified as multidrug-resistant (MDR). All CoNS formed biofilms (58% strong). MLST revealed diverse sequence types (STs), including newly reported ST23 and ST59 for S. epidermidis, and ST24, ST35, and ST109 for S. haemolyticus in Iraq.

Multidrug-resistant CoNS isolates showed high biofilm formation and mecA gene presence, indicating significant clinical infection and resistance challenges.

This study provides valuable data on the prevalence, antibiotic resistance, and genetic diversity of S. epidermidis and S. haemolyticus strains in Anbar, Iraq. It also reports several novel MLST sequence types for the first time in the region, including unique strain IDs for both species, contributing to improved local epidemiological knowledge and surveillance efforts.