<p>Rapid Identification of KL49 <em>Acinetobacter baumannii</em> Associated with Clinical Mortality</p>

Abstract

Objective We aimed to establish a tool for rapid identification of KL49 Acinetobacter baumannii . Methods Based on the capsular polysaccharide (CPS) synthesis genes database, we investigated the distribution of K locus type 49 (KL49) genes in other KL types and established a rapid identification method for KL49. We collected 61 clinical carbapenem-resistant A. baumannii (CRAB) strains, identified KL49 by gtr100 detection, and used whole genome sequencing (WGS) for verification. A mouse pneumonia model was used to confirm the hypervirulence phenotype. We tested the presence of gtr100 gene in 165 CRAB strains from three provinces in China and evaluated the correlation of gtr100 carrying CRAB infection with mortality. Results The gtr100 gene is the CPS synthesis gene found only in KL49. We screened out nine WGS-validated KL49 strains from 61 CRAB clinical strains using polymerase chain reaction (PCR) to detect the gtr100 gene. The survival rates of KL49 strains were significantly lower than nonKL49 strains in a mouse pneumonia model. The survival rates of LAC-4 gtr100 knockout strain decreased significantly. Analysis of phylogenetics showed the worldwide spread of KL49 A. baumannii . Infection of gtr100 carrying CRAB is an independent risk for mortality (OR, 10.76; 95%CI: 3.08–37.55; p <0.001). Conclusion The hypervirulence phenotype of KL49 CRAB and the association with mortality highlight the urgent need for implementing control measures. The rapid identification assay has the potential to facilitate early medical intervention and worldwide surveillance.

An update to the database for Acinetobacter baumannii capsular polysaccharide locus typing extends the extensive and diverse repertoire of genes found at and outside the K locus

“…Though further work is needed to improve the predictive power of WGS for determination of CPS type, the database is a valuable tool for epidemiological studies. Our analysis showed that 17 KL represent a large proportion of the genome assemblies assessed in this study, which includes KL2, KL3/KL22 and KL49 that have been previously linked to increased virulence or poorer patient outcomes [8–10]. Though this may be due to bias in the dataset associated with strain sampling for outbreak studies, particularly the over-representation of genomes for GC2 isolates, new KL described here were each found in <1 % of genomes in the pool, indicating that the previous iteration of the database had captured the most common KL.…”

“…The genetics underlying the CPS type has also proven valuable as an epidemiological marker [3][4][5][6][7]. Finally, recent studies have associated some specific CPS types [8,9] or alterations in the CPS structure [10] with increased virulence. Hence, the determination of the specific type produced in problem strains is important in several areas.…”

Risk factors and genetic characteristics of the carriage of hypervirulent and carbapenem-resistant Acinetobacter baumannii among pregnant women

“…Efforts to understand and track the epidemiology of AB have employed a variety of genotyping methods, revealing the pathogen’s sophisticated population dynamics. This includes exploring virulence traits such as capsular polysaccharide (KL) and the lipooligosaccharide outer core (OCL), which are substantively connected to AB’s pathogenic properties ( Deng et al, 2020 ; Li et al, 2020 ; Diep et al, 2023 ). The technological progress in whole-genome sequencing (WGS) has enriched genotyping capabilities, enabling more nuanced analysis through core genome multilocus sequence typing (cgMLST) or single nucleotide typing (SNP) for detailed typing and evolutionary studies.…”

“…An evident manifestation of CRAB’s genetic plasticity is its co-evolution toward both high virulence and drug resistance. One stark example is the KL49 AB type, similar in capsular polysaccharide type to the hypervirulent strain LAC-4 ( Zhou et al, 2018 ; Deng et al, 2020 ), which has been implicated in several death-related outbreaks across continents ( Valentine et al, 2008 ; Jones et al, 2015 ; Deng et al, 2020 ). Carbapenem-resistant hypervirulent AB (CR-hvAB) isolates with KL49 can cause fatal outcomes not only in immunodeficiency, but also in immunocompetent patients ( Jones et al, 2015 ; Li et al, 2020 ).…”

An update to the database for Acinetobacter baumannii capsular polysaccharide locus typing extends the extensive and diverse repertoire of genes found at and outside the K locus

“…The genetics underlying the CPS type has also proven valuable as an epidemiological marker [3][4][5][6][7]. Finally, recent studies have associated some specific CPS types [8,9] or alterations in the CPS structure [10] with increased virulence. Hence, the determination of the specific type produced in problem strains is important in several areas.…”