agr Genotyping and Biofilm Formation in Staphylococci Isolated From Clinical Specimens

Abstract Staphylococci, a type of Gram-positive cocci, are frequently associated with invasive infections, posing difficulties for effective treatment due to various virulence factors. The accessory gene regulator (agr) gene and biofilm production are known contributors to these treatment challenges. The purpose of this study was to examine the presence of biofilm- forming strains, the agr gene, and patterns of multidrug resistance in staphylococci. A total of 363 staphylococci were isolated from various clinical specimens at Annapurna Neurological and Allied Science Hospital, Maitighar. Kathmandu from August 2023 to February 2024. Disk diffusion test was performed for the methicillin resistant S. aureus (MRSA) and coagulase negative staphylococci (CONS). The antibiotic susceptibility test was performed by Kirby Bauer disc diffusion method following CLSI guidelines. To identify clindamycin and erythromycin resistance a D-test was performed by Kirby Bauer disc diffusion method. Detection of biofilm formation was performed by microtitre plate assay followed by Polymerase Chain Reaction for agr genotyping. Among total isolates 82.9% were S. aureus and 17% were CONS. The disc diffusion method detected 17% of isolates were MRCONS and 36.58% of isolates were MRSA isolates. Both MRSA and MRCONS showed higher resistance towards erythromycin and ampicillin. MRCONS showed multidrug resistance. Only one Methicillin Susceptible Staphylococcus aureus (MSSA) isolate (5.5%) showed Susceptible pattern, 3 MSSA isolates (16.67%) isolates showed Inducible Macrolide- Lincosamide- Streptogramin B (IMLSB) pattern and 2 (11.11%) isolates showed Macrolide- Lincosamide- Streptogramin B (MSB) pattern. Similarly, among MRSA 3 (18.75%) isolates showed Constitutive Macrolide- Lincosamide- Sterptog-ramin B (CMLSB) pattern, 1 (6.25%) isolate showed susceptible pattern and 2 (12.5%) isolates showed IMLSB pattern. A total of 14 (34.15%) isolates were biofilm producers and 27 (65.85%) were biofilm non-producers. Among biofilm producers higher resistance was found against erythromycin (57.1%). Out of total isolates one isolate was agr I (9.1%) positive and 10 (24.4%) isolates were agr III positive. The current investigation revealed that S. aureus and CONS were highly prevalent in the hospital environment. Staphylococcal isolates have demonstrated resistance to (beta) β- lactams and macrolides, which is consistent with the trend of the multiple drugs resistance emerging. Among biofilm formers S. aureus has shown higher resistance towards antibiotics than CONS. Among the isolates agr I and agr III gene has been discovered. The percentage of MRSA from our region that carry this gene seems to be rather high based on the prevalence of the agr gene in MRSA.