Emergence and dissemination of colistin-resistant Klebsiella pneumoniae isolates expressing OXA-48 plus CTX-M-15 in patients not previously treated with colistin in a Spanish university hospital

Global prevalence of mutation in the mgrB gene among clinical isolates of colistin-resistant Klebsiella pneumoniae: a systematic review and meta-analysis

Background

Colistin is used as a last resort for managing infections caused by multidrug-resistant bacteria. However, the high emergence of colistin-resistant strains has restricted the clinical use of this antibiotic in the clinical setting. In the present study, we evaluated the global prevalence of the mutation in the mgrB gene, one of the most important mechanisms of colistin resistance in Klebsiella pneumoniae.

Methods

Several databases, including Scopus, Medline (via PubMed), and Web of Science, were searched (until August 2023) to identify those studies that address the mgrB mutation in clinical isolates of K. pneumoniae. Using Stata software, the pooled prevalence of mgrB mutation and subgroup analyses for the year of publication, country, continent, mgrB mutation types, and detection methods of mgrB mutation were analyzed.

Results

Out of the 115 studies included in the analysis, the prevalence of mgrB mutations in colistin-resistant K. pneumoniae isolates was estimated at 65% of isolates, and mgrB variations with insertional inactivation had the highest prevalence among the five investigated mutations with 69%. The year subgroup analysis indicated an increase in mutated mgrB from 46% in 2014 to 61% in 2022. Europe had the highest prevalence of mutated mgrB at 73%, while Africa had the lowest at 54%.

Conclusion

Mutations in the mgrB gene are reported as one of the most common mechanisms of colistin resistance in K. pneumoniae, and the results of the present study showed that 65% of the reported colistin-resistant K. pneumoniae had a mutation in this gene.

The Impact of Colistin Resistance on the Activation of Innate Immunity by Lipopolysaccharide Modification

Colistin resistance is acquired by different lipopolysaccharide (LPS) modifications. We proposed to evaluate the of effect in vivo colistin resistance acquisition on the innate immune response. We used a pair of ST11 clone Klebsiella pneumoniae strains: an OXA-48, CTX-M-15 K. pneumoniae strain susceptible to colistin (CS-Kp) isolated from a urinary infection and its colistin-resistant variant (CR-Kp) from the same patient after prolonged treatment with colistin. No mutation of previously described genes for colistin resistance (pmrA, pmrB, mgrB, phoP/Q, arnA, arnC, arnT, ugdH, and crrAB) was found in the CR-Kp genome; however, LPS modifications were characterized by negative-ion matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry. The strains were cocultured with human monocytes to determine their survival after phagocytosis and induction to apoptosis. Also, monocytes were stimulated with bacterial LPS to study cytokine and immune checkpoint production. The addition of 4-amino-4-deoxy-l-arabinose (Ara4N) to lipid A of CR-Kp accounted for the colistin resistance. CR-Kp survived significantly longer inside human monocytes after being phagocytosed than did the CS-Kp strain. In addition, LPS from CR-Kp induced both higher apoptosis in monocytes and higher levels of cytokine and immune checkpoint production than LPS from CS-Kp. Our data reveal a variable impact of colistin resistance on the innate immune system, depending on the responsible mechanism. Adding Ara4N to LPS in K. pneumoniae increases bacterial survival after phagocytosis and elicits a higher inflammatory response than its colistin-susceptible counterpart.

Prevalence of Mutated Colistin-Resistant Klebsiella pneumoniae: A Systematic Review and Meta-Analysis

The emergence of genetic mutations in chromosomal genes and the transmissible plasmid-mediated colistin resistance gene may have helped in the spread of colistin resistance among various Klebsiella pneumoniae (K. pneumoniae) isolates and other different bacteria. In this study, the prevalence of mutated colistin-resistant K. pneumoniae isolates was studied globally using a systematic review and meta-analysis approach. A systematic search was conducted in databases including PubMed, ScienceDirect, Scopus and Google Scholar. The pooled prevalence of mutated colistin resistance in K. pneumoniae isolates was analyzed using Comprehensive Meta-Analysis Software (CMA). A total of 50 articles were included in this study. The pooled prevalence of mutated colistin resistance in K. pneumoniae was estimated at 75.4% (95% CI = 67.2−82.1) at high heterogeneity (I2 = 81.742%, p-value < 0.001). Meanwhile, the results of the subgroup analysis demonstrated the highest prevalence in Saudi Arabia with 97.9% (95% CI = 74.1−99.9%) and Egypt, with 4.5% (95% CI = 0.6−26.1%), had the lowest. The majority of mutations could be observed in the mgrB gene (88%), pmrB gene (54%) and phoQ gene (44%). The current study showed a high prevalence of the mutation of colistin resistance genes in K. pneumoniae. Therefore, it is recommended that regular monitoring be performed to control the spread of colistin resistance.

Carbapenemase-Producing Elizabethkingia Meningoseptica from Healthy Pigs Associated with Colistin Use in Spain

Carbapenems are considered last-resort antimicrobials, especially for treating infections involving multidrug-resistant Gram-negative bacteria. In recent years, extended-spectrum β-lactamase (ESBL) and carbapenemase-producing Gram-negative bacteria have become widespread in hospitals, community settings, and the environment, reducing the range of effective therapeutic alternatives. The use of colistin to treat infection caused by these multi-drug bacteria may favour the selection and persistence of carbapenem-resistant bacteria. In this study, it is described, for the first time to our knowledge, a carbapenemase-producing isolate of Elizabethkingia meningoseptica from healthy pigs in Spain. The isolate we report was recovered during a study to detect colistin-resistant bacteria from faecal samples of healthy food-production animals using a chromogenic selective medium. Unexpectedly, we found an isolate of Elizabethkingia meningoseptica with high Minimum Inhibitory Concentration (MIC) values for several antibiotics tested. Molecular analysis did not show any mcr family genes related with colistin resistance, but two carbapenemase genes, blaB-12_1 and blaGOB-17_1, were detected. This finding in healthy animals could suggest that colistin may favour the selection and persistence of carbapenem-resistant bacteria.

Colistin Heteroresistance in Klebsiella Pneumoniae Isolates and Diverse Mutations of PmrAB and PhoPQ in Resistant Subpopulations

Heteroresistance may pose a threat to the prognosis of patients following colistin treatment. We investigated colistin heteroresistance in Klebsiella pneumoniae isolates from South Korea. Among 252 K. pneumoniae blood isolates, 231 were susceptible to polymyxins. Heteroresistance to colistin was determined using population analysis profiles, disk diffusion assays, and E-test strip tests for the susceptible isolates. As a result, we identified three colistin-heteroresistant K. pneumoniae isolates belonging to separate clones (ST11, ST461, and ST3217) by multilocus sequence typing analysis. Two colistin-resistant subpopulations were selected from each heteroresistant isolate in either disk diffusion testing or E-testing. Two resistant subpopulations from the same isolate exhibited different amino acid substitutions in the two-component regulatory systems PmrAB and PhoPQ. An in vitro time–kill assay showed that meropenem combined with colistin had a 1× minimum inhibitory concentration bactericidal effect against a multidrug-resistant, colistin-heteroresistant isolate.