Emergence of colistin-heteroresistant and carbapenem-resistant hypervirulent Klebsiella pneumoniae

Systematic review and meta-analysis of colistin heteroresistance in Klebsiella pneumoniae isolates

BACKGROUND

Antibiotic heteroresistance is a common phenotype observed in a variety of pathogenic bacteria such as K. pneumonia: A subpopulation of cells with a higher MIC than the dominant population is defined as heteroresistance. Several studies have demonstrated colistin heteroresistance in K. pneumonia leading to treatment failures. Therefore, we performed a systematic meta-analysis to summarize the current evidence on the prevalence of colistin heteroresistance in K. pneumonia isolates.

METHODS

Multiple databases were searched to find relevant literature from 2008 to 2024, including PubMed, Scopus, Embase, and Web of Science.

RESULTS

The meta-analysis included eighteen articles. According to the random effects model, the pooled proportion of heteroresistant K. pneumoniae was 0.315 (95% CI: 0.179-0.492). The heterogeneity was substantial, with Q [17] = 335.020, I² = 94.93%, and p < 0.001, suggesting that heteroresistance rates varied widely across the 18 included studies.

CONCLUSION

In conclusion, our findings revealed that a prevalence of colistin heteroresistant detected in approximately 31.5%, of K. pneumonia. These findings are obtained and highlighted in this meta-analysis as a new guidance document for diagnosing and treating K. pneumonia infections is needed to raise the awareness of infectious disease specialists, gastroenterologists, and microbiologists to the heteroresistance to colistin in patients with a K. pneumonia infection.

Study on the predictive value of APACHE II score and neurogenic dysphagia in carbapenem-resistant Klebsiella pneumoniae

Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a growing challenge in clinical treatment globally. Early identification of high-risk patients is essential to control infection spread and improve treatment outcomes. This retrospective study analyzed 152 patients with K pneumoniae infections at the Second People's Hospital of Hefei City, Anhui Province, dividing them into carbapenem-resistant and non-carbapenem-resistant groups. Clinical data, microbiological test results, Acute Physiology and Chronic Health Evaluation II (APACHE II) scores, and neurogenic dysphagia status were evaluated to identify risk factors for CRKP infection. The study revealed that patients in the carbapenem-resistant group had significantly higher APACHE II scores and a higher incidence of neurogenic dysphagia (P < 0.05). Multivariate logistic regression analysis identified APACHE II scores and neurogenic dysphagia as independent risk factors for CRKP infection. Receiver operating characteristic curve analysis showed an area under the curve of 0.824 (95% confidence interval: 0.749-0.898) for the APACHE II score, with an optimal threshold of 14.5 points. A new predictive model combining neurogenic dysphagia with APACHE II scores improved classification performance, as demonstrated by Net Reclassification Improvement (NRI = 0.0967, 95% confidence interval: -0.0477 to 0.2410) and reclassification probability analysis, correctly reclassifying 24.32% of individuals into a higher risk category. The findings highlight the combined predictive value of APACHE II scores and neurogenic dysphagia for early identification and intervention in high-risk CRKP patients.

A novel small RNA PhaS contributes to polymyxin B-heteroresistance in carbapenem-resistant Klebsiella pneumoniae

In recent years, polymyxin has been used as a last-resort therapy for carbapenem-resistant bacterial infections. The emergence of heteroresistance (HR) to polymyxin hampers the efficacy of polymyxin treatment by amplifying resistant subpopulation. However, the mechanisms behind polymyxin HR remain unclear. Small noncoding RNAs (sRNAs) play an important role in regulating drug resistance. The purpose of this study was to investigate the effects and mechanisms of sRNA on polymyxin B (PB)-HR in carbapenem-resistant Klebsiella pneumoniae. In this study, a novel sRNA PhaS was identified by transcriptome sequencing. PhaS expression was elevated in the PB heteroresistant subpopulation. Overexpression and deletion of PhaS were constructed in three carbapenem-resistant K. pneumoniae strains. Population analysis profiling, growth curve, and time-killing curve analysis showed that PhaS enhanced PB-HR. In addition, we verified that PhaS directly targeted phoP through the green fluorescent protein reporter system. PhaS promoted the expression of phoP, thereby encouraging the expression of downstream genes pmrD and arnT. This upregulation of arnT promoted the 4-amino-4-deoxyL-arabinosaccharide (L-Ara4N) modification of lipid A in PhaS overexpressing strains, thus enhancing PB-HR. Further, within the promoter region of PhaS, specific PhoP recognition sites were identified. ONPG assays and RT-qPCR analysis confirmed that PhaS expression was positively modulated by PhoP and thus up-regulated by PB stimulation. To sum up, a novel sRNA enhancing PB-HR was identified and a positive feedback regulatory pathway of sRNA-PhoP/Q was demonstrated in the study. This helps to provide a more comprehensive and clear understanding of the underlying mechanisms behind polymyxin HR in carbapenem-resistant K. pneumoniae.

Antibiotic heteroresistance in Klebsiella pneumoniae: Definition, detection methods, mechanisms, and combination therapy

Klebsiella pneumoniae is a common opportunistic pathogen that presents significant challenges in the treatment of infections due to its resistance to multiple antibiotics. In recent years, K. pneumoniae has been reported for the development of heteroresistance, a phenomenon where subpopulations of the susceptible bacteria exhibit resistance. This heteroresistance has been associated with increased morbidity and mortality rates. Complicating matters further, its definition and detection pose challenges, often leading to its oversight or misdiagnosis. Various mechanisms contribute to the development of heteroresistance in K. pneumoniae, and these mechanisms differ among different antibiotics. Even for the same antibiotic, multiple mechanisms may be involved. However, our current understanding of these mechanisms remains incomplete, and further research is needed to gain a more comprehensive understanding of heteroresistance. While the clinical recommendation is to use combination antibiotic therapy to mitigate heteroresistance, this approach also comes with several drawbacks and potential adverse effects. In this review, we discuss the definition, detection methods, molecular mechanisms, and treatment of heterogenic resistance, aiming to pave the way for more effective treatment and management in the future. However, addressing the problem of heteroresistance in K. pneumoniae represents a long and complex journey that necessitates comprehensive research efforts.

Dissemination of antibiotic resistance genes from aboveground sources to groundwater in livestock farms

Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are prevalent in various environments on livestock farms, including livestock waste, soil, and groundwater. Contamination of groundwater by ARB and ARGs in livestock farms is a growing concern as it may have potentially huge risks to human health. However, the source of groundwater-borne ARB and ARGs in animal farms remains largely unknown. In this study, different types of samples including groundwater and its potential contamination sources from aboveground (pig feces, wastewater, and soil) from both working and abandoned swine feedlots in southern China were collected and subjected to metagenomic sequencing and ARB isolation. The source tracking based on metagenomic analysis revealed that 56-95 % of ARGs in groundwater was attributable to aboveground sources. Using metagenomic assembly, we found that 45 ARGs predominantly conferring resistance to aminoglycosides, sulfonamides, and tetracyclines could be transferred from the aboveground sources to groundwater, mostly through plasmid-mediated horizontal gene transfer. Furthermore, the full-length nucleotide sequences of sul1, tetA, and TEM-1 detected in ARB isolates exhibited the close evolutionary relationships between aboveground sources and groundwater. Some isolated strains of antibiotic-resistant Pseudomonas spp. from aboveground sources and groundwater had the high similarity (average nucleotide identity > 99 %). Notably, the groundwater-borne ARGs were identified as mainly carried by bacterial pathogens, potentially posing risks to human and animal health. Overall, this study underscores the dissemination of ARGs from aboveground sources to groundwater in animal farms and associated risks.