Comparative analysis of conventional and direct antimicrobial susceptibility testing of blood cultures in a tertiary care cancer hospital: the way forward

Bloodstream infections (BSI) are associated with high mortality rates, especially in immunocompromised patients. Identifying pathogens early and selecting appropriate antimicrobials to treat BSI is integral in reducing the mortality rate. There is a need to reduce the turnaround time (TAT) of pathogen identification as well as to accelerate the antimicrobial susceptibility testing (AST) of blood cultures, which can be achieved by following relevant identification methods and performing the direct AST (DAST) by the disk diffusion method. In this study, blood samples were collected from patients with suspected bacteremia/septicemia, and aseptic precautions were taken to prevent contamination. Samples containing gram-negative bacilli (GNB) were then analyzed by DAST and conventional AST (CAST). We tested 118 GNB-positive isolates in total to compare the results of DAST and CAST. DAST and CAST showed good categorical agreement (CA) for various groups of microorganisms: 98.9% and 99.6% for Enterobacterales and Pseudomonas spp., respectively. Early detection of pathogens in blood along with the determination of their antibiotic susceptibility patterns is a need of the hour. By performing DAST on positive blood culture broth, clinical teams can obtain the information necessary for switching from empirical therapy to definitive treatment one day faster. This rapid identification of the pathogen, along with corresponding AST results, will help clinicians to accelerate targeted antimicrobial therapy for critical patients and, thus, reduce mortality and morbidity rates in patients with bloodstream infections.