Colistin Heteroresistance among Extended Spectrum β-lactamases-Producing Klebsiella pneumoniae

Abstract

Colistin-heteroresistant (CST-HR) Enterobacterales isolates have been identified recently, challenging the clinical laboratories since routine susceptibility tests fail to detect this phenotype. In this work we describe the first CST-HR phenotype in extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae isolates in South America. Additionally, we determine the genomic mechanisms of colistin heteroresistance in these strains. The CST-HR phenotype was analyzed by the population analysis profile (PAP) method, and mutations associated with this phenotype were determined by whole-genome sequencing (WGS) and the local BLAST+ DB tool. As a result, 8/60 isolates were classified as CST-HR according to the PAP method. From WGS, we determined that the CST-HR isolates belong to three different Sequence Types (STs) and four K-loci: ST11 (KL15 and KL81), ST25 (KL2), and ST1161 (KL19). We identified diverse mutations in the two-component regulatory systems PmrAB and PhoPQ, as well as a disruption of the mgrB global regulator mediated by IS1-like and IS-5-like elements, which could confer resistance to CST in CST-HR and ESBL-producing isolates. These are the first descriptions in Chile of CST-HR in ESBL-producing K. pneumoniae isolates. The emergence of these isolates could have a major impact on the effectiveness of colistin as a “last resort” against these isolates, thus jeopardizing current antibiotic alternatives; therefore, it is important to consider the epidemiology of the CST-HR phenotype.

Insight into Antibiotic Synergy Combinations for Eliminating Colistin Heteroresistant Klebsiella pneumoniae

“…In our study, among the three MDR CH K. pneumoniae strains identified by PAP assays, two of them belong to ST15 and ST323, which are known multi-drug-resistant clones. Similarly, there are also other studies, where CH isolates belonging to well-known multidrug-resistant international lineages such as ST11, ST307 were identified [24,[29][30][31][32]. The association of colistin heteroresistance with isolates belonging to MDR clones which are known to be globally disseminated is very worrying since infections due to such strains are more likely to be treated with colistin if these are misclassified as susceptible by clinical diagnostic testing.…”

Assessment of Colistin Heteroresistance among Multidrug-Resistant Klebsiella pneumoniae Isolated from Intensive Care Patients in Europe

“…A strength of this study was its large sample size compared to previous studies on CHR using the PAP assay [ 22 , 23 , 24 , 25 ]. Within this study, two different classification schemes for CHR were used.…”

Antibiotic Heteroresistance in Klebsiella pneumoniae

“…It was proposed that an amino acid change in the sensor domain of PhoQ or PhoQ overexpression may lead to the constitutive phosphorylation of PhoP, and the subsequent activation of genes involved in lipid A modifications [ 51 ]. Colistin heteroresistance in K. pneumoniae was also attributed to mutations in the pmrAB genes, encoding another two-component system that controls the synthesis of L-Ara4N and PEtN ( Figure 2 ) [ 21 , 56 , 57 ]. It is worth noting that diverse resistant subpopulations with different amino acid substitutions in PhoPQ and PmrAB were detected in various isolates.…”

“…Other studies have found that clinical crrB mutations lead to the addition of both L-Ara4N and pEtN to lipid A, inducing higher polymyxin resistance [ 69 ]. Colistin resistance may also be linked to mutations, insertions, or deletions in the mgrB , yciM , and lpxM genes [ 44 , 51 , 53 , 57 ]. The mgrB gene encodes a small transmembrane protein which acts as a negative regulator of the PhoPQ system.…”

“…The mgrB gene encodes a small transmembrane protein which acts as a negative regulator of the PhoPQ system. Therefore, its inactivation leads to overexpression of the pmrHFIJKLM operon [ 44 , 53 , 57 ]. The inactivation of the mgrB gene may also result in a thicker multilayered capsule which protects bacteria against colistin [ 70 ].…”