From the Guidelines
Colistin resistance detection methods should prioritize a combination of phenotypic and genotypic approaches to ensure accurate and timely results, considering the limitations and advantages of each method, as highlighted in recent studies 1. When evaluating the advantages and disadvantages of colistin resistance detection methods, it is essential to consider the clinical context and the potential impact on patient outcomes.
Key Considerations
- Phenotypic methods, such as broth microdilution (BMD), are considered the gold standard but are time-consuming and require technical expertise 1.
- Genotypic methods, including PCR and whole genome sequencing, offer rapid detection of known resistance genes but may not identify novel resistance mechanisms or those caused by chromosomal mutations 1.
- Automated systems and MALDI-TOF MS provide quick results but may have higher error rates or require specialized equipment and expertise.
- Combination methods, like the rapid polymyxin NP test, offer a balance of speed and accuracy but may have variable performance across different bacterial species.
Clinical Implications
- The choice of detection method should be guided by the laboratory's resources, turnaround time requirements, and the prevalence of colistin resistance in their setting 1.
- For critical infections where colistin might be needed, using multiple complementary methods may provide the most comprehensive assessment of resistance, as suggested by recent guidelines 1.
- The potential benefits of combination therapy, including colistin-carbapenem, should be weighed against the limitations of current evidence and the risk of promoting further resistance development 1.
Recommendations
- Laboratories should consider implementing a combination of phenotypic and genotypic methods to detect colistin resistance, taking into account the strengths and limitations of each approach.
- Clinicians should be aware of the potential advantages and disadvantages of different detection methods and consider the clinical context when interpreting results and making treatment decisions.
- Further research is needed to develop more accurate and efficient methods for detecting colistin resistance and to inform the optimal use of combination therapy in clinical practice 1.
From the Research
Advantages of Colistin Resistance Detection Methods
- Rapid detection of colistin resistance can improve patient outcomes and prevent the spread of resistance 2
- The Micromax assay is a simple, rapid, and accurate method for detecting colistin resistance in A. baumannii, with results obtained in 3 h 30 min 2
- The RPNP test and novel culture media are recommended for under-resourced laboratories due to their sensitivity, specificity, cost, and required skill 3
- Molecular diagnostics such as the CT103XL microarray, eazyplex SuperBug kit, and Taqman/SYBR Green real-time PCR assays offer 100% sensitivity and specificity, with a shorter turnaround time (<3 hr) 3
- The RCDE test is a cheaper and more rapid alternative for detecting colistin resistance among Enterobacteriaceae in low-income countries, with good performance comparable to the CBDE test 4
Disadvantages of Colistin Resistance Detection Methods
- Some methods may have high very major error (VME) rates, such as the RCDE and CBDE tests for A. baumannii isolates 4
- The use of colistin-based regimens can lead to higher rates of acute kidney injury compared to other agents such as ceftazidime/avibactam and meropenem/vaborbactam 5
- The dissemination of plasmid-borne mcr genes can assist in the spread of colistin resistance to other pathogenic bacteria, making it a serious concern 6
- Some Gram-negative species are intrinsically resistant to colistin activity, which can limit the effectiveness of detection methods 6
- The development of new methods for detecting colistin resistance determinants and reverting colistin resistance is an ongoing challenge, requiring further investigation 6