Comparison of Rapid Antibiotic Susceptibility Test Method Directly from Blood Culture Bottle with Standard Disc Diffusion Method

Abstract

Aim: Early determination of antimicrobial susceptibility of sepsis pathogens is important. In this study, we aimed to compare the standard disc diffusion method with the rapid antimicrobial susceptibility testing (RAST) method performed directly from blood culture bottles. Material and Methods: Bacteria isolated from samples that gave a positive signal on the blood culture device between April 2019 and September 2019 were included in the study, and antimicrobial susceptibilities were determined by the standard disc diffusion method and the RAST method. Categorical agreement, small error, large error, very large error, and area of technical uncertainty ratios were recorded. Results: A total of 103 bacteria including 19 S. aureus, 10 Enterococcus spp. and 24 E. coli, 24 K. pneumoniae, 13 P. aeruginosa, and 13 A. baumannii were included in the study. When the RAST method was compared with the standard disc diffusion method, 100% agreement was found between the methods against imipenem, meropenem, gentamicin, and trimethoprim-sulfamethoxazole in E. coli isolates at all hours evaluated, and against meropenem in K. pneumoniae isolates at the 6th and 8th hour. For S. aureus and P. aeruginosa isolates, very major errors were found in the RAST results. For A. baumannii isolates, 100% agreement between methods was observed for many antibiotics. Conclusion: It was concluded that the RAST method is a simple and inexpensive test for life-threatening infections such as sepsis. It was also felt that similar studies should be carried out with a large number of isolates, as compliance rates vary depending on the bacteria tested.