Evolved resistance to colistin and its loss due to genetic reversion in Pseudomonas aeruginosa

Abstract

The increased reliance on colistin for treating multidrug-resistant Gram-negative bacterial infections has resulted in the emergence of colistin-resistant Pseudomonas aeruginosa. We attempted to identify genetic contributors to colistin resistance in vitro evolved isogenic colistin-resistant and -susceptible strains of two P. aeruginosa lineages (P5 and P155). Their evolutionary paths to acquisition and loss of colistin resistance were also tracked. Comparative genomic analysis revealed 13 and five colistin resistance determinants in the P5 and P155 lineages, respectively. Lipid A in colistin-resistant mutants was modified through the addition of 4-amino-L-arabinose; this modification was absent in colistin-susceptible revertant strains. Many amino acid substitutions that emerged during the acquisition of colistin resistance were reversed in colistin-susceptible revertants. We demonstrated that evolved colistin resistance in P. aeruginosa was mediated by a complicated regulatory network that likely emerges through diverse genetic alterations. Colistin-resistant P. aeruginosa became susceptible to the colistin upon its withdrawal because of genetic reversion. The mechanisms through which P. aeruginosa acquires and loses colistin resistance have implications on the treatment options that can be applied against P. aeruginosa infections, with respect to improving bactericidal efficacy and preventing further resistance to antibiotics.

The evolution of antimicrobial peptide resistance in Pseudomonas aeruginosa is shaped by strong epistatic interactions

“…2)283940. This specific phoQ mutation has also been identified in clinical and in vitro evolved isolates with increased col R (refs 30, 38, 41). These findings argue against inactivation of a negative regulator as an adequate explanation for the selective preference of this specific mutation.…”

Rapid and Consistent Evolution of Colistin Resistance in Extensively Drug-Resistant Pseudomonas aeruginosa during Morbidostat Culture

“…One reason why colistin-resistant strains do not emerge as frequently in clinical settings as in in vitro experiments could be fitness costs and impaired virulence associated with resistance. Lee et al (11) observed rapid reversion of colistin resistance mutations in P. aeruginosa. Similarly, references 47 and 48 describe fitness costs of colistin resistance in Acinetobacter baumannii isolates, while others also reported an inhibited growth of colistinresistant LPS mutants in fetal bovine serum (49) and a decreased production of capsular polysaccharides in a Klebsiella pneumoniae strain (50).…”

“…These mutations alter the outer membrane of P. aeruginosa by addition of 4-amino-4-deoxy-L-arabinose (L-Ara4N) to phosphate groups of the LPS lipid A region. The resulting reduced negative charge decreases the uptake of polycationic antimicrobial peptides and lipopeptide polymyxins (11). This modification is typically induced by enzymes that are encoded in the arnBCADTEF-PA3559 (PA3552-PA3559) operon (12).…”

In Vitro and In Vivo Efficacy of an LpxC Inhibitor, CHIR-090, Alone or Combined with Colistin against Pseudomonas aeruginosa Biofilm

“…A better understanding of the molecular mechanisms responsible for the reduced colistin susceptibility in the subpopulations of each strain with higher colistin MICs is now of great interest to better understand the mechanism of synergy observed with CHIR-090. Inactivation of lipid A biosynthesis has already been reported to be associated with reduced susceptibility to colistin in Acinetobacter baumannii and recently in P. aeruginosa (20,21) Of interest, a complex and reversible mechanism involving the regulatory network, genetic alterations, and lipid A biosynthesis was suggested in P. aeruginosa (22). These findings highlight the great interest in inhibitors of lipid A biosynthesis and their therapeutic potential in combination with colistin for the treatment of Gram-negative bacterial infections associated or not associated with biofilms.…”