Coagulase Negative Staphylococcus as a Cause for Bacteraemia: Mere a Contaminant or Potential Threat as Pathogen, an Observational Study

Introduction: Coagulase-negative Staphylococcus is considered as one of the most common skin commensal bacteria in human beings. Usually, patients with weakened immune system (with prosthetic devices, pacemakers and intravenous catheters) are prone to develop infections due to CONS. They were previously considered as culture contaminants, but in the past decades they are gaining significance as significant pathogen. A contaminant can be differentiated from a pathogen depending upon various clinical and microbiological aspects. Clinically, a true infection is generally considered in patients with fever with or without Leukocytosis or hypotension whereas growth of CONS in blood culture within 48 hours of inoculation along with multiple blood cultures (>2) positive for same organism with similar antibiograms favours microbiological part of infection related to that particular pathogen. Materials and Methods: Data were collected prospectively over a period of 1 year (January 2023-December 2023) to determine the prevalence of significant CONS bacteraemia at our tertiary care setup by automated culture and sensitivity methods (Biomerieux vitek-2 compact) and to evaluate drug therapy in patients with repeated cultures positive for CONS by Kirby-Bauer disc diffusion method on Muller-Hinton agar. The study findings were interpreted on the basis of CLSI standards. Detection of methicillin resistance among CONS was performed using cefoxitin disk (30 μg) diffusion method. Data analysis was done using descriptive statistics. The study was approved by our Ethics committee (IEC no GBCM/IEC/2024/05-01)Results: Blood culture positivity came out to be 35% at our tertiary care set up in a period of one year. Out of which majority of the isolated organisms were CONS (73.09%) and rest (other than CONS) were 26.01 %. Among blood isolates other than CONS, most common isolates were Staphylococcus aureus, Echerichia coli, Acinetobacter calcoaceticus baumanii complex and few were Klebsiells sp, Pseudomonas and Enterococcus spp. The interesting fact which came out as a result in our study that, out of 133 CONS isolates only 97(73%) were positive in multiple cultures proving others to be a mere contaminant (23%). The samples which were failed to come as repeat cultures due to unavoidable circumstances were not calculated in the study. Among all the CONS isolates, Staphylococcus hominis subspecies hominis predominated (62 %) followed by Staphylococcus epidermidis (25 %), Staphylococcus hemolyticus (08 %), Staphylococcus saprophyticus (04 %) one isolate was identified as Kockuria Kristae (1%). Most of the CONS isolates were resistant to penicillin (91 %) and azithromycin (94 %), followed by levofloxacin and clindamycin. Least resistance was shown to vancomycin and linezolid (3%) followed by teicoplanin. Cefoxitin resistance CONS was detected in 62 (64%) isolates.Conclusion: To conclude, CONS bacteraemia is one of the most considerate reasons for nosocomial blood-stream infections and its crucial to look upon these isolates as pathogen, not mere contaminant. The relevance of repeated blood cultures is proved in our study and many studies prior to rule out contaminant from clinically significant pathogen. As they could put a profound impact on an institution’s bloodstream infection rates therefore slight improvement in hand hygiene measures could decrease the blood culture contamination rates. which in return will restrict unnecessary antibiotic usage and decrease antimicrobial resistance.