Frequency of Isolation of Coagulase Negative Staphylococcus from Blood Cultures and its Antibiogram

Background: Coagulase-negative Staphylococci are members of stable skin inhabitants. They are frequent contaminants in blood cultures and can lead to unnecessary exposure of patients to antimicrobial drugs and excess hospital costs. This study aims to estimate the frequency of Coagulase-negative Staphylococci in blood cultures and their antibiograms. Materials and Methods: This cross-sectional study was performed in a tertiary care hospital over one year from April 2018 to March 2019. Blood cultures received in the laboratory were processed to isolate Coagulase-negative Staphylococci. Susceptibility to various antimicrobial drugs was detected by disc diffusion method and E-strips. Results: A total of 13802 blood cultures were processed in one year. 1750 blood cultures yielded bacterial growth and 374 blood cultures were positive for Staphylococci. Out of these 374 blood cultures, 97 were categorized as Staphylococcus aureus and 277 were Coagulase-negative Staphylococci. Out of 13802 total blood cultures performed during study period, 277 blood cultures positive with Coagulase negative Staphylococcus means contamination rate of 2% out of total blood cultures. 277 Coagulase negative Staphylococcus positive cultures out of 1750 positive blood cultures means contamination rate of 15.8% out of positive blood cultures. Among Coagulase-negative Staphylococci, 68.2% isolates were resistant to Cefoxitin, 95.3% to Penicillin, 85.1% to Erythromycin, 37.5% to Ciprofloxacin, 59.6% to Gentamicin, 68.6% to Fusidic acid, 3.6% to Teichoplanin, and 1.4% to Linezolid. All isolates were sensitive to Vancomycin. Conclusion: The rate of blood culture contamination was 2% out of total blood cultures and 15.8% out of positive blood cultures.