Speciation and Antimicrobial Susceptibility of Coagulase Negative Staphylococci Isolated from Clinical Samples in a Tertiary Care Centre

Dr. Aparna Aparajita; Dr. Ashok Kumar Sharma

Volume : IX, Issue : VIII, August - 2020

Speciation and Antimicrobial Susceptibility of Coagulase Negative Staphylococci Isolated from Clinical Samples in a Tertiary Care Centre

Dr. Aparna Aparajita, Dr. Ashok Kumar Sharma

Abstract :

Introduction: Coagulase negative staphylococci are usually considered contaminants when isolated from clinical samples but have gained importance in causing various nosocomial infections in seriously ill and immunocompromised patients specially in those with indwelling device or prosthetic implants. Several commercial identification systems for identification of coagulase negative staphylococci are available but are still out of reach to most of the laboratories in developing countries. The present study aimed to identify these group of organisms by conventional methods with minimum number of tests which were simple, inexpensive and easy to perform. Materials & methods: The present study was a cross sectional study, conducted in the Department of Microbiology, RIMS, Ranchi from July 2017 to June 2018. A total of 111 consecutive, clinically significant strains of CoNS were isolated from various clinical samples which included blood, wound swab, pus, body fluids, sputum, urine etc. Identification was done using conventional microbiological methods. Antibiotic sensitivity testing was performed by Kirby Bauer disc diffusion method on Mueller–Hinton agar using a number of antibiotics. The results were read as the zone of inhibition as per CLSI guidelines. Results: Out of 657 staphylococci samples a total of 111samples were identified as coagulase negative staphylococci. S. epidermidis 55(49.5%) was the most common isolate in our study, followed by S. haemolyticus 27(24.3%), S. saprophyticus 11(9.9%), S. cohnii 9(8.1%), S. lugdunensis 5(4.5%), S. hominis 3(2.7%) and S. warneri 1(0.9%) respectively. Antibiotic susceptibility pattern of the isolates showed that most isolates were resistant to Ampicillin 107 (96.4%), followed by cefotaxime 104(93.7%), Erythromycin 95(85.6%), Ciprofloxacin 78 (71.2%), cefoxitin 39(35.2%) and Trimethoprim–sulfamethoxazole 67(60.3%). Sensitivity of the isolates to Tetracycline were 57(51.3%), gentamicin 53(47.7%) and Clindamycin 78(70.2%). Highest sensitivities of CoNS isolates were shown to Vancomycin and Linezolid (100%) followed by Netilmycin 98 (88.2%) and Ampicillin–sulbactam 89 (80.1%). Conclusion: The conventional methods of identification can be useful in identification of CoNS isolates even in the absence of automated systems. The rising resistance to various antibiotics is of prime concern therefore correct and timely identification along with appropriate antibiotic selection helps the clinicians to provide effective therapies thereby reducing the chances of development of resistance, patient morbidity and mortality.