The purpose of this study is to shorten the time required for subculture, bacterial identification, and antibiotic susceptibility test, and to obtain a fast accurate and simple results by searching for a new test method for bloodstream infection.
Mass spectrometry which is used to aid in bacterial identification and can identify bacteria easily within 5 to 10 minutes was used in this study. The antimicrobial susceptibility test was carried out using the VITEK 2 system.
In order to quickly identify the bacteria that proliferated in the blood culture, the concentrated bacterial suspension which is made by adding a mixed solution of 9.26% ammonium chloride solution(0.1mL) and 2% saponin solution to the broth containing protein component. It destroyed cellular components in 10 minutes and concentrated by washing with 0.45% saline.
The result was analyzed by the accuracy and concordance rate between two methods. The accuracy of the bacterial identification was high as 97.6% in the intestinal bacteria and the accuracy of the gram-positive bacteria was similar to that of the previous studies. In addition, the reporting time was shortened to 24 ～ 72 hours compared to previous inspection methods.
There was no difference in identification rate between blood culture. However, using anaerobic culture did not require dissolution process, and sample preparation time could be shortened.
The antimicrobial susceptibility test met the CLSI criteria, and was able to reduce the reporting time by 24 hours. However, it was found that additional test should be done with the disc diffusion methods for the antimicrobial agents with very large errors.
These results suggest that conducting bacterial identification and antimicrobial test directly in the broth is very useful for the treatment of patients, as it is accurate and is quick on result reporting. However further studies in the future will need to improve the method for identifying streptococci and Coagulase-negative staphylococcus(CNS) that lacked accuracy in this study.