Antimicrobial resistance pattern of bacterial isolates and genetic resistance determinants of carbapenemase producers in bloodstream infections

Introduction: Bloodstream infection (BSI) continues to be a significant cause of disease and death in hospitalized patients worldwide. These are among the most common healthcare-associated infections with a mortality rate of 20%-50%. The emergence of multidrug resistance among the organisms causing BSI is of great concern. Objectives: The study was undertaken in a medical intensive care unit of a tertiary care hospital in Eastern India to evaluate the spectrum of pathogens causing BSI, their antimicrobial resistance patterns and carbapenemase enzyme production using polymerase chain reaction (PCR). Materials and Methods: A total of 550 blood samples from clinically suspected cases of BSIs were studied from July 2016 to June 2018. Blood samples were inoculated and incubated in BacT/ALERT (BioMerieux) system. Identification and antibiotic susceptibility testing was conducted in Vitek-2 (BioMerieux) as per the Clinical Laboratory Standards Institute guidelines. Methicillin-resistant Staphylococcus aureus (MRSA) and β-lactamase production were also noted in the Vitek-2 method. All Gram-negative isolates were studied for carbapenemase production by the genotypic method using PCR. Results: Of 550 samples, 116 samples yielded the growth of various bacterial isolates. Of these, 54 (47%) were Gram-positive organisms and 62 (53%) were Gram-negative organisms. S. aureus was the most common organism isolated followed by Klebsiella pneumoniae. MRSA was observed in 66.7% of S. aureus isolates. Among Gram-negative isolates, 43.5% were found to be β-lactamase producers and 66.1% were carbapenemase producers. Most of the carbapenemase producers were encoded by the OXA gene (58%). Conclusion: This study emphasizes the importance of antibiotic policy and its stringent application, which will eventually help us to control the menacing rise in antimicrobial resistance.