Coagulase‑negative staphylococci causing blood stream infection at an Indian tertiary care hospital: Prevalence, antimicrobial resistance and molecular characterisation.

ABSTRACT

Introduction: Recent years have seen a rise of coagulase‑negative staphylococci (CoNS) from common contaminants to agents of nosocomial blood stream infections (BSI’s). Molecular typing and establishing a correlation with antibiotic resistance is essential particularly in countries like India where genotyping studies for drug‑resistant CoNS are sparse. Methods: A prospective study was done over 18 months, wherein 42,693 blood samples were received, and 59 patients with BSI due to CoNS were evaluated. The isolates recovered were identified by a biochemical test panel and matrix‑assisted laser desorption ionization – time of flight mass spectrometry followed by antimicrobial susceptibility testing by Kirby–Baur disc diffusion method and E‑test strips. Staphylococcal chromosomal cassette mec (SCCmec) element was characterised by multiplex polymerase chain reaction for all methicillin‑resistant (MR) isolates. Results: The majority of CoNS isolated were constituted by Staphylococcus haemolyticus (47.5%) followed by Staphylococcus epidermidis (33.9%), Staphylococcus hominis (11.86%), Staphylococcus cohnii (5.08%) and Staphylococcus warneri (1.69%). Among all isolates 57.6% were MR with statistically significant higher resistance versus methicillin sensitive‑CoNS. This difference was significant for erythromycin (76% vs. 44%, P = 0.011), rifampicin (50% vs. 12%, P = 0.002) and amikacin (26.5% vs. 4%, P = 0.023), ciprofloxacin (64.7% vs. 20%, P = 0.001) and cotrimoxazole (55.9% vs. 20%, P = 0.006). SCCmec type I was predominant (61.8%, P = 0.028) and exhibited multidrug resistance (76.2%). Coexistence of SCCmec type I and III was seen in 8.82% MR isolates. Conclusion: CoNS exhibit high antimicrobial resistance thereby limiting treatment options. The presence of new variants of SCCmec type in hospital‑acquired CoNS may predict the antibiotic resistance pattern. This is the first evaluation of the molecular epidemiology of CoNS causing BSI from India and can serve as a guide in the formulation of hospital infection control and treatment guidelines.