Contributing to appropriate antibiotic treatment with rapid antimicrobial susceptibility testing (RAST) from positive blood cultures

Rapid Antimicrobial Susceptibility Testing technique validated by European Committee on Antimicrobial Susceptibility Testing for some Gram (+/-) bacteria. In this study; It was aimed to compare the evaluation of antibiotic discs and microorganism identification times with routinely used automatic systems in terms of time and accuracy. Antibiotic disc zone diameter results were determined at the 4, 6, 8 or 16-20 hours for the samples taken from the bottles that gave a positive signal on the blood culture system, and at this time, conventional diagnostic methods that would provide the first estimated diagnosis to the colonies that had grown were applied and the antimicrobial susceptibility testing results were reported to the clinic. Identification and antimicrobial susceptibility testing results of growths on blood agar medium were made with automatic system (Vitek-2, bioMérieux, France). As statistical analysis methods; Z-Test and Fisher's exact test were used. 5049 blood culture bottles arrived in our laboratory (within 5.5 months). A total of 2172 blood culture bottles gave a positive signal in this period. Categorical agreement was determined as follows: (4,6,8,16-20), E. coli (88,89,93,-), K. pneumoniae (88,95,89,-), A. baumannii (95,94,95,-), P. aeruginosa (-,86,86,-), TPZ (86,87,92,-), CAZ (95,95,92,-), MEM (95,96,89,-), CIP (90,95,93,-), SXT (92,95,89,-), AK (82,94,95,-), IPM (86,93,89,-), S. aureus (100,100,98,100), FOX (100,100,98,100), E. faecalis (-,100,68,72), E. faecium (-,-,84,-), AM (-,100,85,100), VA (-,-,36,0), LNZ (-,100,94,100), S. pneumoniae (-,-,-100), AM (-,-,-,100), E (-,-,-,100). The time when the most samples were read for the bacteria is 6-8 hours in Gram negative bacteria, 16-20 hours in S. pneumoniae and it is 8 hours in other Gram positive bacteria. Apart from these bacteria, 136 bacteria have been identified with Vitek-2. The time difference between Rapid Antimicrobial Susceptibility Testing and automatic identification system is as follows; E. coli (20.9 h), K. pneumoniae (20.8 h), A. baumannii (29.7 h), P. aeruginosa (19.2 h), S. aureus (15.3 h), E. faecalis (10.8 h), E. faecium (14.5 h), S. pneumoniae (37 h). With the Rapid Antimicrobial Susceptibility Testing method, antimicrobial susceptibility results of bacteria grown in positive blood cultures can be given within hours with high accuracy.