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Optimization and Validation of an FTIR-based, All-in-one System for Viable MDR Bacteria Detection in Combat-related
Ying Chen1, Andrew Leung1, Yulia Wang2
1Optowares, Inc., Woburn, MA 01801, USA.
Introduction:
The U.S. Military members experiencing combat-related injuries have a higher chance of developing infections by multidrug-resistant (MDR) bacteria at admission to military hospitals. MDR wound infections result in higher amputation rates and greater risks for subsequent or chronic infections that require readmission or extended stay in the hospital. Currently, there is no FDA-clear, deployable early diagnostic system for suitable field use.We are reporting our efforts to improve a previously developed Rapid Label-free Pathogen Identification (RAPID) system to detect viable MDR bacteria in wound infections and perform antibiotic susceptibility testing (AST). Specifically, we added multiplex and automation capability and significantly simplified the sample preparation process. A functional prototype of the improved system was built, and its performance was validated using a variety of lab-prepared spiked samples and real-world samples.
Materials And Methods:
To access the baseline performance of the improved RAPID system in detecting bacteria presence, we selected 17 isolates, most of them from blood or wound infections, and prepared mono-strain spiked samples at 104 to 106 cfu/mL concentration. These samples were processed and analyzed by the RAPID system. To demonstrate the AST capability of the system, we selected 6 strains against 6 different antibiotics and compared the results from the system with the ones from the gold standard method.To validate the system's performance with real-world samples, we first investigated its performance on 3 swab samples from epicutaneous methicillin-resistant Staphylococcus aureus-exposed mouse model. The AST results from our system were compared with the ones from the gold standard method. All animal experiments were approved by the Johns Hopkins University Animal Care and Use Committee (Protocol No. MO21M378). Then, we obtained swab samples from 7 atopic dermatitis (AD) patients and compared our AST results with the ones from the gold standard method. The human subject protocol was approved by the Johns Hopkins Medicines Institutional Review Boards (Study No. CR00043438/IRB00307926) and by USAMRDC (Proposal Log Number/Study Number 20000251).
Results:
High-quality data were obtained from the spiked samples of all 17 strains. A quantitative analysis model built using these data achieved 94% accuracy in predicting the species ID in 8 unknown samples. The AST results on the spiked samples had shown 100% matching with the gold standard method. Our system successfully detects the presence/absence of viable bacteria in all 3 mouse and 7 AD patient swab samples. Our system shows 100% and 85.7% (6 out of 7) accuracy when compared to the oxacillin susceptibility testing results for the mouse and the AD patient swabs, respectively.
Conclusions:
Our system has achieved excellent performance in detecting viable bacteria presence and in performing AST in a multiplex, automated, and easy-to-operate manner, on both lab-prepared and real samples. Our results have shown a path forward to a rapid (sample-to-answer time ≤3 hours), accurate, sensitive, species-specific, and portable system to detect the presence of MDR combat-related wound infections in the field environment. Our future efforts involve ruggedizing the RAPID system and evaluating performance under relevant environmental conditions.
Insights
A new Rapid Label-free Pathogen Identification (RAPID) system accurately detects multidrug-resistant (MDR) bacteria and performs antibiotic susceptibility testing (AST) in under three hours. This portable diagnostic tool shows promise for field use in identifying combat-related wound infections.
Area of Science:
- Biotechnology
- Medical Diagnostics
- Infectious Disease Research
Background:
- Combat injuries increase risk of multidrug-resistant (MDR) bacterial infections in military personnel.
- MDR wound infections lead to higher amputation rates and prolonged hospital stays.
- Lack of a deployable, FDA-cleared early diagnostic system for field use poses a significant challenge.
Purpose of the Study:
- To improve the Rapid Label-free Pathogen Identification (RAPID) system for detecting viable MDR bacteria and performing antibiotic susceptibility testing (AST).
- To enhance the system with multiplexing, automation, and simplified sample preparation for field applicability.
- To validate the performance of the improved RAPID system using both laboratory and real-world samples.
Main Methods:
- Validated the improved RAPID system using 17 bacterial isolates at concentrations of 10^4 to 10^6 CFU/mL.
- Assessed antibiotic susceptibility testing (AST) for 6 strains against 6 antibiotics, comparing results to the gold standard.
- Tested system performance on swab samples from a mouse model and 7 atopic dermatitis (AD) patients, comparing AST results to the gold standard.
Main Results:
- Achieved 94% accuracy in species identification using a quantitative analysis model on unknown samples.
- Demonstrated 100% concordance with the gold standard for AST on spiked samples.
- Successfully detected viable bacteria in mouse and AD patient samples, with 100% and 85.7% accuracy for oxacillin susceptibility, respectively.
Conclusions:
- The improved RAPID system offers excellent performance in detecting viable bacteria and performing AST in a multiplexed, automated, and user-friendly manner.
- The system provides a pathway towards a rapid (≤3 hours), accurate, sensitive, species-specific, and portable solution for field detection of MDR combat-related wound infections.
- Future work will focus on ruggedizing the system and evaluating its performance under relevant environmental conditions.
