Identification of pmrB mutations as putative mechanism for colistin resistance in A. baumannii strains isolated after in vivo colistin exposure

Marano, Vito; Marascio, Nadia; Pavia, Grazia; Lamberti, Angelo Giuseppe; Quirino, Angela; Musarella, Rosanna; Casalinuovo, Francesco; Mazzitelli, Maria; Trecarichi, Enrico Maria; Torti, Carlo; Matera, Giovanni; Liberto, Maria Carla

doi:10.1016/j.micpath.2020.104058

Cited by 15 publications

(15 citation statements)

References 22 publications

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“…Colistin has been classified as "Reserve Group" of antibiotics to be used as a lastresort antibiotic against MDR infections that cannot be treated by any other conventional antibiotics (Hsia et al, 2019). However, the efficacy of colistin has been challenged by emerging acquired colistin resistance in several human pathogens and the global spread of plasmid acquired colistin resistance (Liu et al, 2016;McGann et al, 2016;Rolain et al, 2016;Elbediwi et al, 2020;Marano et al, 2020). Interestingly, species like Burkholderia are intrinsically resistant to colistin and the resistance may be multifactorial (Loutet and Valvano, 2011;Hamad et al, 2012;Malott et al, 2012;El-Halfawy and Valvano, 2014).…”

Section: Discussionmentioning

confidence: 99%

“…However, clinical use of colistin is increasing due to limited alternative therapeutic options (Li et al, 2006). With increased colistin use, the emergence of colistin resistance has been documented in several human pathogens, such as K. pneumoniae (Bratu et al, 2005;Antoniadou et al, 2007;Farzana et al, 2020), Salmonella enterica serovar Newport (Elbediwi et al, 2020), and Acinetobacter baumannii (Marano et al, 2020;Papathanakos et al, 2020). More worrisome is the recent global spread of mobilized colistin resistance (mcr) genes (Elbediwi et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

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A Burkholderia thailandensis DedA Family Membrane Protein Is Required for Proton Motive Force Dependent Lipid A Modification

Panta

Doerrler

2021

Front. Microbiol.

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The DedA family is a conserved membrane protein family found in most organisms. A Burkholderia thailandensis DedA family protein, named DbcA, is required for high-level colistin (polymyxin E) resistance, but the mechanism awaits elucidation. Modification of lipopolysaccharide lipid A with the cationic sugar aminoarabinose (Ara4N) is required for colistin resistance and is dependent upon protonmotive force (PMF) dependent transporters. B. thailandensis ΔdbcA lipid A contains only small amounts of Ara4N, likely leading to colistin sensitivity. Two B. thailandensis operons are required for lipid A modification with Ara4N, one needed for biosynthesis of undecaprenyl-P-Ara4N and one for transport of the lipid linked sugar and subsequent lipid A modification. Here, we directed overexpression of each arn operon by genomic insertion of inducible promoters. We found that overexpression of arn operons in ΔdbcA can partially, but not completely, restore Ara4N modification of lipid A and colistin resistance. Artificially increasing the PMF by lowering the pH of the growth media also increased membrane potential, amounts of Ara4N, and colistin resistance of ΔdbcA. In addition, the products of arn operons are essential for acid tolerance, suggesting a physiological function of Ara4N modification. Finally, we show that ΔdbcA is sensitive to bacitracin and expression of a B. thailandensis UppP/BacA homolog (BTH_I1512) can partially restore resistance to bacitracin. Expression of a different UppP/BacA homolog (BTH_I2750) can partially restore colistin resistance, without changing the lipid A profile. This work suggests that maintaining optimal membrane potential at slightly alkaline pH media by DbcA is responsible for proper modification of lipid A by Ara4N and provides evidence of lipid A modification-dependent and -independent mechanisms of colistin resistance in B. thailandensis.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Burkholderia thailandensis DedA Family Membrane Protein Is Required for Proton Motive Force Dependent Lipid A Modification

Panta

Doerrler

2021

Front. Microbiol.

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“…Total loss of lipid A of the LPS by alteration of lxpA, lxpC and lpxD genes has been described as a colistin resistance mechanism in Acinetobacter baumannii (5). Mutations in pmrAB also lead to colistin resistance in this species (19,46,47). A published comparison between susceptible and resistant A. baumannii isolates after in vivo exposure in three different patients found different but unique mutations in pmrB that led to resistance levels of 16mg/ml (47).…”

Section: Discussionmentioning

confidence: 99%

Colistin resistance in Gram-negative bacteria analysed by five phenotypic assays and inference of the underlying genomic mechanisms

Torres

Seth-Smith

Jossee

et al. 2021

Preprint

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Background Colistin is used against multi-drug resistant pathogens, yet resistance emerges either through dissemination of plasmid-mediated genes (mcr) or chromosomal mutation of genes involved in lipopolysaccharide synthesis (i.e. mgrB, phoPQ, pmrCAB). Phenotypic susceptibility testing is challenging due to poor diffusion of colistin in agar media, leading to an underestimation of resistance. We aimed to compare the performance of four different phenotypic approaches in the context of different molecular mechanism of resistance. Methods We compared the performance of Vitek 2® (bioMérieux, AST N242), Colistin MIC Test Strip (Liofilchem Diagnostici), UMIC (Biocentric), and Rapid Polymyxin NP Test (ELITechGroup) against the standard broth microdilution (BDM) method. We used whole genome sequencing (WGS) to infer the molecular mechanisms of resistance. A total of 97 Enterobacterales and non-fermenting bacterial isolates were collected from clinical samples during 2016–2017 and tested for colistin susceptibility. Data was analysed by comparing the susceptibility category (susceptible or resistant) and minimal inhibitory concentrations (MIC). We determined diversity of isolates by core genome multi locus sequencing typing (cgMLST) and identified antimicrobial resistance genes using NCBI and CARD databases. Results Of the 97 clinical isolates, 54 (56%) were resistant by the standard broth microdilution. The highest susceptibility category concordance was achieved by the Rapid Polymyxin NP test (98.8%) followed by UMIC (97.9%), E-test MIC strip (96.9%) and Vitek 2 (95.6%). The highest MIC concordance was achieved by UMIC (80.4%), followed by Vitek 2 (72.5%) and E-test MIC strip (62.9%). Among the resistant isolates, 23/54 (43%) were intrinsically resistant to colistin, whereas 31/54 (57%) isolates had acquired colistin resistance. Of these, mcr-1 was detected in four isolates and mcr-2 in one isolate. Mutations in mgrB, phoQ, pmrA, pmrB, and pmrC genes that led to amino acid changes were encountered in Klebsiella pneumoniae, Escherichia coli, and Acinetobacter bereziniae resistant isolates. Conclusions The Rapid Polymyxin NP test showed the highest categorical concordance and the UMIC test provided MIC values with a high concordance to the standard method. We found colistin resistance in diverse species occurred predominantly through spontaneous chromosomal mutation rather than plasmid-mediated resistance.

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“…The mechanism of emergent colistin resistance was evaluated in n=49 cases (Table 1). In most cases (n=44) a variety of mutations were noted in the pmrCAB locus (predominantly pmrB) [16, 18, 20, 23, 25-29, 31-33, 36, 38, 40, 41, 44, 46], resulting in upregulation of pmr genes [16,23,25,27,36,44,46]. The locus regulates a phosphoethanolamine (pEtN) transferase coded by pmrC, that by modifying the lipid A component of LPS reduces its negative charge and decreases the binding of the positively charged colistin.…”

Section: Mechanisms Of Emergent Resistancementioning

confidence: 99%

“…The impact of emergent resistance was evaluable in 28 cases; in 86% (24/28) emergent resistance was associated with persistent or recurrent infection [8,11,12,17,22,23,28,32,37,38,40,43,46] (Table 1), while in 14% (4/28) emergent resistance did not require any further treatment [13,19,27,43], possibly due to reduced virulence of the resistant strains [15,19,27].…”

Section: Does Emergent Resistance Explain Treatment Failure?mentioning

confidence: 99%

A Systematic Review of Implications, Mechanisms, and Stability of In Vivo Emergent Resistance to Colistin and Tigecycline in <em>Acinetobacter baumannii</em>

Karakonstantis

2020

Preprint

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The potential of A. baumannii for acquired resistance to last resort antibiotics (colistin and tigecycline) during treatment has important clinical implications, especially when dealing with patients failing to improve despite treatment with an active antimicrobial. However, the relevant literature remains scattered. Therefore, a systematic search was conducted in PubMed and Scopus. Several studies reported emergence of resistance to colistin or tigecycline during treatment, in most cases (86%) resulting in persistent or recurrent infections, especially in cases of emergent resistance without fitness cost. Lipopolysaccharide modification in the case of colistin and overexpression of efflux pumps in the case of tigecycline were the main mechanisms of resistance. Emergent colistin resistance is often associated with fitness cost resulting in re-emergence of the fitter and more virulent colistin susceptible strain after cessation of antibiotic pressure. Prospective studies are needed to determine the frequency of emergent resistance during treatment and its impact on patient outcomes.

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Identification of pmrB mutations as putative mechanism for colistin resistance in A. baumannii strains isolated after in vivo colistin exposure

Cited by 15 publications

References 22 publications

A Burkholderia thailandensis DedA Family Membrane Protein Is Required for Proton Motive Force Dependent Lipid A Modification

A Burkholderia thailandensis DedA Family Membrane Protein Is Required for Proton Motive Force Dependent Lipid A Modification

Colistin resistance in Gram-negative bacteria analysed by five phenotypic assays and inference of the underlying genomic mechanisms

A Systematic Review of Implications, Mechanisms, and Stability of In Vivo Emergent Resistance to Colistin and Tigecycline in <em>Acinetobacter baumannii</em>

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