Evaluation of rapid polymyxin Nordmann Poirel test for detection of polymyxin resistance in clinical isolates of Enterobacteriaceae

Clinical analysis of colistin sulfate in the treatment of pneumonia caused by carbapenem-resistant Gram-negative bacteria

BACKGROUND

Multidrug-resistant Gram-negative bacteria, exacerbated by excessive use of antimicrobials and immunosuppressants, are a major health threat.

AIM

To study the clinical efficacy and safety of colistin sulfate in the treatment of carbapenem-resistant Gram-negative bacilli-induced pneumonia, and to provide theoretical reference for clinical diagnosis and treatment.

METHODS

This retrospective analysis involved 54 patients with Gram-negative bacilli pneumonia admitted to intensive care unit of The General Hospital of the Northern Theater Command of the People's Liberation Army of China from August 2020 to June 2022. After bacteriological culture, the patients' airway secretions were collected to confirm the presence of Gram-negative bacilli. The patients were divided into the experimental and control groups according to the medication used. The research group consisted of 28 patients who received polymyxin sulfate combined with other drugs through intravenous, nebulization, or intravenous combined with nebulization, with a daily dosage of 1.5-3.0 million units. The control group consisted of 26 patients who received standard dosages of other antibiotics (including sulbactam sodium for injection, cefoperazone sodium sulbactam for injection, tigecycline, meropenem, or vaborbactam).

RESULTS

Of the 28 patients included in the research group, 26 patients showed improvement, treatment was ineffective for two patients, and one patient died, with the treatment efficacy rate of 92.82%. Of the 26 patients in the control group, 18 patients improved, treatment was ineffective for eight patients, and two patients died, with the treatment efficacy rate of 54.9%; significant difference was observed between the two groups (P < 0.05). The levels of white blood cell (WBC), procalcitonin (PCT), and C-reactive protein (CRP) in both groups were significantly lower after treatment than before treatment (P < 0.05), and the levels of WBC, PCT, and CRP in the research group were significantly lower than those in the control group (P < 0.05). Compared with before treatment, there were no significant changes in aspartate aminotransferase, creatinine, and glomerular filtration rate in both groups, while total bilirubin and alanine aminotransferase decreased after treatment (P < 0.05) with no difference between the groups. In patients with good clinical outcomes, the sequential organ failure assessment (SOFA) score was low when treated with inhaled polymyxin sulfate, and specific antibiotic treatment did not improve the outcome. Sepsis and septic shock as well as a low SOFA score were independent factors associated with good clinical outcomes.

CONCLUSION

Polymyxin sulfate has a significant effect on the treatment of patients with multiple drug-resistant Gram-negative bacilli pneumonia and other infections in the lungs and is safe and reliable. Moreover, the administration route of low-dose intravenous injection combined with nebulization shows better therapeutic effects and lower adverse reactions, providing new ideas for clinical administration.

Detection of polymyxins resistance among Enterobacterales: evaluation of available methods and proposal of a new rapid and feasible methodology

BACKGROUND

Fast and accurate detection of polymyxins resistance is necessary as they remain the last resources to treat infections caused by Carbapenem-resistant Enterobacterales in many regions. We evaluated the rapid colorimetric polymyxin B elution (RCPE) and developed its miniaturized version, RCPE microelution (RCPEm), aiming to detect polymyxins resistance among Enterobacterales.

METHODS

The methodologies consist of exposing the bacterial population in a solution (NP solution) where polymyxin B disks were previously eluted to obtain a concentration of 2 µg/mL for RCPE and 3 µg/mL for RCPEm.

RESULTS

Two hundred sixty-seven Enterobacterales were evaluated, 90 (33.7%) resistant to polymyxin B by broth microdilution. It was observed 0.6% of major error (ME) by RCPE, with a specificity of 99.4%. The miniaturized version (RCPEm) presented the same ME and specificity values, but slightly higher sensitivity (97.8% vs. 95.6%) with 2.2% of very major error (VME).

CONCLUSIONS

RCPE and RCPEm proved to be useful alternatives to determine polymyxin B susceptibility in clinical microbiology laboratories, presenting low cost, being easy to perform, and demanding short incubation time.

Rapid high-resolution detection of colistin resistance in Gram-negative bacteria using flow cytometry: a comparison with broth microdilution, a commercial screening test and WGS

BACKGROUND

Even though both EUCAST and CLSI consider broth microdilution (BMD) as the reference method for antimicrobial susceptibility testing (AST) of colistin, the method exhibits potential flaws related to properties of the colistin molecule.

OBJECTIVES

To develop a flow cytometry method (FCM) for colistin AST and to validate it against BMD, a commercial screening test and WGS.

METHODS

Colistin-mediated loss of membrane integrity in Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter spp. was detected with the fluorescent probe YoPro-1 by FCM. An international collection of 65 resistant and 109 susceptible isolates were analysed and the colistin concentration required to reach the EC50 was compared with the BMD MIC and the presence of genotypic resistance markers.

RESULTS

The overall FCM sensitivity and specificity for colistin resistance was 89% and 94%, with E. coli > K. pneumoniae > P. aeruginosa, whereas the performance for Acinetobacter spp. was poor. All tested E. coli were correctly categorized. Three K. pneumoniae isolates with genotypic findings consistent with colistin resistance were detected by FCM but not BMD. Compared with BMD, FCM delivered AST results with a 75% reduction of time.

CONCLUSIONS

Here, we present a rapid FCM-based AST assay for qualitative and quantitative testing of colistin resistance in E. coli and K. pneumoniae. The assay revealed probable chromosomal colistin resistance in K. pneumoniae that was not detected by BMD. If confirmed, these results question the reliability of BMD for colistin testing.

Synergistic Recognition-Triggered Charge Transfer Enables Rapid Visual Colorimetric Detection of Fentanyl

As a new psychoactive substance, abuse of fentanyl (FTN) is currently spreading around the world, resulting in an urgent need of on-site and rapid analytical methods for detection of FTN. Here, we present a synergistic recognition strategy for rapid, cost-effective, selective, sensitive, and visual colorimetric detection of FTN by taking advantage of Rose Bengal (RB) as the specific probe. This assay is based on the halogen- and hydrogen-bonding interactions between them, generating a charge transfer and accompanying a red shift in the RB absorption band as well as color change from red to purple. The utility of the present visual colorimetric assay is demonstrated in aqueous solution, diluted urine, and domestic sewage samples. A detection limit of 0.7 mg·L^-1 in aqueous solution is achieved, and the naked-eye detection of FTN is also realized in different real matrices within 6 min. Moreover, this method is insusceptible to interference from various substances (other opioids, cutting agents of street drugs, FTN precursors, amino acids, and small-molecular amines). Additionally, we successfully fabricate a smartphone-based portable device to determine FTN, which is appropriate for field tests. The present work not only provides the first visual assay for FTN but also reveals the molecular structure-property relationship, which will guide the design and development of various probes for recognizing FTN.

Polymyxin NP tests (from colonies and directly from blood cultures): accurate and rapid methodologies to detect polymyxin B susceptibility among Enterobacterales

Detection of polymyxins susceptibility is challenging. We aimed to evaluate Rapid Polymyxin NP from colonies (NP-colony) and directly from positive blood bottles (NP-bottle), using polymyxin B instead of colistin among Enterobacterales. Both had similar and acceptable accuracy. This is the first study performing NP-bottle using polymyxin B instead of colistin.