Rapid Identification and Antimicrobial Susceptibility Testing of Gram Positive Bacteria by Direct Inoculation from Positive Blood Culture Bottles

Abstract Background Rapid identification of the causative agent for sepsis and determination of its susceptibility profile by direct inoculation of the biochemical and susceptibility testing media with the blood-broth mixtures from signal positive bottles might help reducing the time needed for provision of results compared to the standard isolated-colony based method and hence would help the rapid initiation of effective and targeted antimicrobial therapy and reduce the bacteremia-related morbidity and mortality Aim of the Work To validate the direct inoculation method as a rapid method for the identification of Gram-positive bacteremic isolates and determination of their antimicrobial susceptibility profile by comparing its results to that of the standard isolate-based method routinely used in our laboratories. Patients and Methods This study included a total of 100 positive blood culture bottles submitted to the Main Microbiology laboratory for identification and antimicrobial susceptibility testing via disk diffusion method directly from blood culture bottles and according to standard isolate-based identification method. Results There was a 100% categorical agreement between the results of the direct (primary) biochemical identification method and those of the standard isolate-based identification method. As regard AST the overall categorical agreement between both methods was 96.9%, the minor error rate was 0.8% and the major error rate was 2.3%. Conclusion Rapid Identification and Antimicrobial Susceptibility Testing of Gram-positive Bacteria is a time saving method and can help in reducing turnaround time to obtain AST results.