Susceptibility Testing by Volatile Organic Compound Detection Direct from Positive Blood Cultures: A Proof-of-Principle Laboratory Study

Abstract

Background: Bacteria produce volatile organic compounds (VOCs) during growth, which can be detected by colorimetric sensor arrays (CSAs). The SpecifAST® system (Specific Diagnostics) employs this technique to enable antibiotic susceptibility testing (AST) directly from blood cultures without prior subculture of isolates. The aim of this study was to compare the SpecifAST® AST results and analysis time to the VITEK®2 (bioMérieux) system. Methods: In a 12-month single site prospective study, remnants of clinical positive monomicrobial blood cultures were combined with a series of antibiotic concentrations. Volatile emission was monitored at 37 °C via CSAs. Minimal Inhibitory Concentrations (MICs) of seven antimicrobial agents for Enterobacterales, Staphylococcus, and Enterococcus spp. were compared to VITEK®2 AST results. MICs were interpreted according to EUCAST clinical breakpoints. Performance was assessed by calculating agreement and discrepancy rates. Results: In total, 96 positive blood cultures containing Enterobacterales, Staphylococcus, and Enterococcus spp. were tested (269 bug–drug combinations). The categorical agreement of the SpecifAST® system compared to the VITEK®2 system was 100% and 91% for Gram-negatives and Gram-positives, respectively. Errors among Gram-positives were from coagulase-negative staphylococci. Overall results were available in 3.1 h (±0.9 h) after growth detection without the need for subculture steps. Conclusion: The AST results based on VOC detection are promising and warrant further evaluation in studies with a larger sample of bacterial species and antimicrobials.

Blood Culture Headspace Gas Analysis Enables Early Detection of Escherichia coli Bacteremia in an Animal Model of Sepsis

“…Moreover, mVOC analysis of BC could be an appropriate method to perform rapid antimicrobial susceptibility testing [ 32 , 33 ]. Kuil et al [ 32 ] compared the results and analysis time of a colorimetric sensor array to detect VOCs with VITEK ® 2.…”

“…Moreover, mVOC analysis of BC could be an appropriate method to perform rapid antimicrobial susceptibility testing [ 32 , 33 ]. Kuil et al [ 32 ] compared the results and analysis time of a colorimetric sensor array to detect VOCs with VITEK ® 2. In 96 positive blood cultures, a categorical agreement was 100% for Gram-negatives and 91% for Gram-positives, with overall results being available in 3.1 h (±0.9 h) after growth detection.…”

A decade of clinical microbiology: top 10 advances in 10 years: what every infection preventionist and antimicrobial steward should know

“…Novel methods include detection of changes in cell morphology induced by antimicrobials using single cell microscopy, assessing the rate of cell division, examining gene expression patterns, or detection of volatile organic compounds. 48 One commercially available system in the US performs AST approximately 7 hours from positive blood cultures using time-lapse imaging under dark-field microscopy, monitoring morphological and kinetic changes in the bacteria to determine MICs. 49 Several other rapid AST platforms are in the development pipeline.…”

Current Limitations of Staph Infection Diagnostics, and the Role for VOCs in Achieving Culture-Independent Detection

“…Breath tests have high sensitivity and specificity, especially when utilizing a profile of multiple VOCs as biomarkers for infection [ 99 ]. VOCs can differentiate closely-related pathogens of the same genus and have the capacity to concomitantly reveal antibiotic sensitivity or resistance [ 100 , 101 ]. Because breath volatiles can be detected down to picomole concentrations [ 102 ], it may be possible to detect disease prior to occurrence of symptomology.…”

“…CSAs can also be used to perform rapid antibiotic susceptibility testing directly from blood cultures by growing aliquots of the cultures in an antibiotic array and monitoring for bacterial growth via VOC production. Kuil and colleagues analyzed the performance of the SPECIFIC REVEAL® CSA system for antibiotic susceptibility testing of 96 positive blood cultures [ 101 ]. They observed perfect agreement with the categorical results (susceptible, intermediate, or resistant) provided by bioMérieux VITEK®2 system for infections caused by Gram-negative bacteria and 91% agreement for the Gram-positives, including S. aureus .…”