Evaluation of EUCAST rapid antibiotic susceptibility testing for positive blood cultures in the Autobio BC60 blood culture system

Abstract

Early diagnosis and effective treatment of bloodstream infections significantly improve prognosis. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) has developed rapid antimicrobial susceptibility testing(RAST) based on the disk diffusion method. In the present study, we compared the data from the RAST study from positive blood cultures in the Autobio BC (Autobio-diagnostics, Zhengzhou, Chinese) blood culture system with those obtained using the standard disk diffusion method. A total of 234 spiked blood culture samples (Klebsiella penumoniae [n= 50], Escherichia coli [n= 50], Acinetobacter baumannii [n= 20], Pseudomonas aeruginosa [n= 13], Staphylococcus aureus [n= 51], and Enterococcus spp. [n= 50]) were collected. The RAST test was performed on positive bottles, and the results were measured at 4, 8, and 20 h. Standard disk diffusion (sDD) was performed, and zone diameters were measured from subculture samples obtained from blood culture bottles. The RAST zone diameters were compared with the sDD zone diameters. The categorical agreement based on the readable zone diameters for the 4th, 8th, and 20th h was K.pneumoniae (99.7 %,99.7 %,99.7 %), E.coli (99.4 %,99.6 %,99.7 %), A.baumannii (98.7 %,98.7 %,98.7 %), P.aeruginosa (100 %,99.3 %,100 %), S. aureus (100 %,100 %,100 %), and Enterococcus spp. (100 %,100 %,100 %). The minor error(mE), major error(ME), and very major error(VME) results obtained in the whole study were determined as 0.9, 0, and 1.3 for 4 h; 1.4, 0, and 1.3 for 8 h; 0.6, 0, and 1.3 for 20 h. The EUCAST RAST study can be performed from positive bottles in the Autobio BC blood culture system, resulting in reliable outcomes. To report earlier antibiotic susceptibility test results, laboratories using Autobio BC can combine RAST with quality control studies.

Keywords: Blood culture; Early diagnosis; Rapid antimicrobial susceptibility testing.