Breakthrough: BJMC Unveils Faster Colistin Test for MDR Infections!

Colistin susceptibility testing is crucial for guiding treatment of multi-drug resistant (MDR) infections, especially when colistin, a “last resort” antibiotic, presents the only viable option. Nonetheless, colistin is highly nephrotoxic and neurotoxic. Hence, confirming its effectiveness against specific MDR infections before administration is paramount to prevent adverse outcomes. For many years, broth microdilution (BMD) served as the gold standard method for determining colistin susceptibility.

Challenges with Traditional Colistin Susceptibility Testing

Despite its status as the reference method, BMD presents significant challenges for clinical microbiology laboratories. Indeed, this labor-intensive technique is often impractical for routine use. Moreover, colistin’s amphipathic nature can cause it to bind to plastic materials, potentially affecting MIC determinations in BMD tests. These factors highlight the urgent need for a more efficient and user-friendly alternative that maintains high accuracy. Consequently, many laboratories, particularly in resource-limited settings, struggle to implement BMD routinely. This often delays critical treatment decisions for patients with severe infections.

Introducing the Colistin Broth Disk Elution (CBDE) Method

Doctors at the microbiology department of BJ Medical College in Pune successfully developed and evaluated a new method: colistin broth disk elution (CBDE). This innovative technique offers a faster and more accurate approach to colistin susceptibility testing. The CBDE method significantly addresses BMD’s limitations by streamlining the testing process. For instance, it can save up to an hour per patient in busy government hospitals, a crucial factor when dealing with life-threatening MDR infections. Furthermore, it conserves valuable manpower, thereby improving laboratory efficiency.

Advantages of the CBDE Method in Colistin Susceptibility Testing

The CBDE method demonstrates remarkable benefits over traditional BMD. It shows high categorical agreement with BMD and consistently low error rates, establishing it as a reliable alternative. Specifically, studies indicate categorical agreement rates often exceeding 90%, with some reporting up to 100% for certain isolates. The Clinical and Laboratory Standards Institute (CLSI) has, in fact, endorsed CBDE for colistin testing of Enterobacterales and Pseudomonas aeruginosa. Therefore, its simplicity, cost-effectiveness, and reproducibility make CBDE an excellent tool to bolster antimicrobial stewardship efforts, particularly in resource-limited regions. Ultimately, accurate and timely colistin susceptibility testing empowers doctors to make better, informed treatment decisions, ensuring patients receive the most effective therapy.

Future Validation and Policy Implications

Researchers published their paper, “Comparison of Broth Disk Elution and Broth Microdilution Methods for Colistin Susceptibility Testing in Carbapenem-Resistant Enterobacteriaceae and Pseudomonas aeruginosa,” in Cureus, a peer-reviewed journal. They also submitted it to the Ministry of Health and Family Welfare for further consideration. However, the developers acknowledge that the new method requires further validation before a definitive policy decision can replace BMD with CBDE for routine colistin susceptibility testing. Ongoing research and validation will ensure the widespread adoption and optimal implementation of this promising new technique.

Frequently Asked Questions

Q1: What is colistin and why is its susceptibility testing important?

Colistin is a ‘last resort’ antibiotic used for patients with multi-drug resistant (MDR) infections. Because it is highly damaging to the kidneys (nephrotoxic) and nervous system (neurotoxic), confirming its effectiveness against a specific infection before administration is crucial to prevent severe side effects and ensure patient benefit.

Q2: What are the main advantages of the CBDE method over the traditional BMD method?

The Colistin Broth Disk Elution (CBDE) method is faster, more accurate, and less labor-intensive than the traditional Broth Microdilution (BMD) method. It saves time for patients, conserves manpower in laboratories, and has shown high categorical agreement with BMD while having low error rates.

Q3: Has the CBDE method been officially recognized?

Yes, the Clinical and Laboratory Standards Institute (CLSI) has endorsed the CBDE method for colistin susceptibility testing in Enterobacterales and Pseudomonas aeruginosa. However, further validation is still recommended before a complete policy shift from BMD to CBDE for routine testing.

References

1. BJ Medical doctors discover faster, more accurate way to test ‘last resort’antibiotic – ETHealthworld
2. Multicenter Evaluation of Colistin Broth Disk Elution and Colistin Agar Test: a Report from the Clinical and Laboratory Standards Institute – PMC – PubMed Central
3. Two-Site Evaluation of the Colistin Broth Disk Elution Test To Determine Colistin In Vitro Activity against Gram-Negative Bacilli – PMC
4. Evaluation of Broth Disk Elution Test and Agar Test to Determine Colistin In Vitro Activity in Enterobacteriaceae. – Ain Shams Medical Journal
5. Review of Colistin Susceptibility Testing with Current Data – Molecular Imaging and Radionuclide Therapy
6. Two-Site Evaluation of the Colistin Broth Disk Elution Test To Determine Colistin In Vitro Activity against Gram-Negative Bacilli | Journal of Clinical Microbiology
7. A COMPARATIVE STUDY OF COLISTIN BROTH DISK ELUTION TEST AND BROTH MICRODILUTION TEST ON GRAM-NEGATIVE BACTERIA IN ALL CLINICAL I – International Journal of Academic Medicine and Pharmacy
8. Evaluation of different methods for in vitro susceptibility testing of colistin in carbapenem resistant Gram-negative bacilli – PubMed Central
9. Is Colistin Susceptibility Testing Finally on the Right Track? – PMC
10. (PDF) Colistin Susceptibility Testing of Gram-Negative Bacilli: Better Performance of Vitek2 System than E-Test Compared to Broth Microdilution Method as the Gold Standard Test – ResearchGate
11. Evaluation of colistin susceptibility by four phenotypic methods compared to broth microdilution in multidrug-resistant Klebsiella pneumoniae – PubMed Central
12. (PDF) Evaluation of different methods for in vitro susceptibility testing of colistin in carbapenem resistant Gram-negative bacilli – ResearchGate
13. Evaluation of Broth Disk Elution Method to Determine Colistin Resistance in Klebsiella pneumoniae and Escherichia coli Strains – PubMed
14. Comparative evaluation of colistin broth disc elution (CBDE) and broth microdilution (BMD) in clinical isolates of Pseudomonas aeruginosa with special reference to heteroresistance – Bohrium

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