Advancing antimicrobial susceptibility testing in body fluid-associated infections: a focus on direct testing for timely and targeted therapeutic interventions

Background: timely Antimicrobial Susceptibility Testing (AST) is critical in managing infections, particularly with the rise of multidrug-resistant organisms. This study evaluates the efficacy of Direct AST (D-AST) on body fluids in reducing turnaround time compared to Routine AST (R-AST).

Materials and Methods: over six months, 43 monobacterial body fluid samples were analyzed using both D-AST and R-AST at a tertiary care hospital. D-AST was performed on the same day of sample receipt, while R-AST followed Clinical and Laboratory Standards Institute (CLSI) guidelines. Concordance between the methods was statistically assessed.

Results: D-AST showed high concordance with R-AST for most antibiotics (p>0.05), with a significant reduction in turnaround time (D-AST: 24-36 hours; R-AST: 48-72 hours). For Gram-negative organisms, discrepancies were noted for amikacin sensitivity in Escherichia coli (D-AST: 76.19%; R-AST: 90.4%) and ciprofloxacin in Klebsiella pneumoniae (D-AST: 80%; R-AST: 100%). Gram-positive organisms showed 100% concordance for key antibiotics like linezolid and teicoplanin.

Conclusions: D-AST is a reliable, rapid alternative to R-AST, enabling earlier therapeutic decisions and reducing empirical antibiotic use. It shows promise in improving outcomes and combating antimicrobial resistance, particularly in resource-limited settings. Further standardization is needed for broader application.