Abstract
For the timely treatment of patients with infections in bloodstream and cerebrospinal fluid, a rapid antimicrobial susceptibility test (AST) is urgently needed. Here, we describe a direct and rapid antimicrobial susceptibility testing (dRAST) system, which can determine the antimicrobial susceptibility of bacteria from a positive blood culture bottle (PBCB) in six hours. The positive blood culture sample is directly mixed with agarose and inoculated into a micropatterned plastic microchip with lyophilized antibiotic agents. Using microscopic detection of bacterial colony formation in agarose, the total time to result from a PBCB for dRAST was only six hours for a wide range of bacterial concentrations in PBCBs. The results from the dRAST system were consistent with the results from a standard AST, broth microdilution test. In tests of clinical isolates (n = 206) composed of 16 Gram-negative species and seven Gram-positive species, the dRAST system was accurate compared to the standard broth microdilution test, with rates of 91.11% (2613/2868) categorical agreement, 6.69% (192/2868) minor error, 2.72% (50/1837) major error and 1.45% (13/896) very major error. Thus, the dRAST system can be used to rapidly identify appropriate antimicrobial agents for the treatment of blood stream infection (BSI) and antibiotic-resistant strain infections.
Highlights
Bloodstream infection (BSI) is a leading cause of morbidity and mortality among hospitalized patients, and approximately 250,000 cases of blood stream infection (BSI) occur in the U.S annually[1]
By satisfying the recommended performance criteria of the United States (U.S.) Food and Drug Administration (FDA), this study demonstrated the feasibility of using the direct and rapid antimicrobial susceptibility testing (dRAST) system in clinical settings as a rapid antimicrobial susceptibility test (AST) for positive blood culture specimens
The raw sample contained an average of 109 colony forming unit (CFU)/ml of bacterial cells mixed with hemocytes, and the microcolonies were too small for their formation to be detected
Summary
Bloodstream infection (BSI) is a leading cause of morbidity and mortality among hospitalized patients, and approximately 250,000 cases of BSI occur in the U.S annually[1]. The total turnaround time (TAT) of current antibiotic resistance detection process for blood samples from BSI patients is longer than three days since it requires three overnight culture steps: blood culture, subculture and antimicrobial susceptibility test (AST) culture (see Fig. 1A). These separation processes are time consuming and require multiple manual preparations that are not suitable for clinical application. By satisfying the recommended performance criteria of the United States (U.S.) Food and Drug Administration (FDA), this study demonstrated the feasibility of using the dRAST system in clinical settings as a rapid AST for positive blood culture specimens. The direct use of PBCBs in this rapid AST system reduced the turnaround time to appropriate antimicrobial treatment by two days compared to conventional systems
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