Oxidative Stress Induction of the MexXY Multidrug Efflux Genes and Promotion of Aminoglycoside Resistance Development in Pseudomonas aeruginosa

Abstract

Exposure to reactive oxygen species (ROS) (e.g., peroxide) was shown to induce expression of the PA5471 gene, which was previously shown to be required for antimicrobial induction of the MexXY components of the MexXY-OprM multidrug efflux system and aminoglycoside resistance determinant in Pseudomonas aeruginosa. mexXY was also induced by peroxide exposure, and this too was PA5471 dependent. The prospect of ROS promoting mexXY expression and aminoglycoside resistance recalls P. aeruginosa infection of the chronically inflamed lungs of cystic fibrosis (CF) patients, where the organism is exposed to ROS and where MexXY-OprM predominates as the mechanism of aminoglycoside resistance. While ROS did not enhance aminoglycoside resistance in vitro, long-term (8-day) exposure of P. aeruginosa to peroxide (mimicking chronic in vivo ROS exposure) increased aminoglycoside resistance frequency, dependent upon PA5471 and mexXY. This enhanced resistance frequency was also seen in a mutant strain overexpressing PA5471, in the absence of peroxide, suggesting that induction of PA5471 by peroxide was key to peroxide enhancement of aminoglycoside resistance frequency. Resistant mutants selected following peroxide exposure were typically pan-aminoglycoside-resistant, with mexXY generally required for this resistance. Moreover, PA5471 was required for mexXY expression and aminoglycoside resistance in these as well as several CF isolates examined.

Prevalence of eight resistance-nodulation-division efflux pump genes in epidemiologically characterized Acinetobacter baumannii of worldwide origin

“…MexCD functions as part of the envelope stress response (Fraud et al, 2008). However, MexEF is linked to the organism's nitrosative stress response (Fetar et al, 2011), whereas oxidative stress (Fraud & Poole, 2011) activates MexXY expression. Except for the overlapping substrate profile of AdeB, AdeJ and AdeG, and a growth-phase-dependent expression of these genes (Fernando & Kumar, 2012), little is known about regulation of the RND-type efflux systems in A. baumannii.…”

Primary mechanisms mediating aminoglycoside resistance in the multidrug-resistant Pseudomonas aeruginosa clinical isolate PA7

“…cefepime, ceftobiprole; Hocquet et al, 2006;Baum et al, 2009), tigecycline (Dean et al, 2003), LBM415 (peptide deformylase inhibitor; Caughlan et al, 2009) and/or some other sources of stress (e.g. oxidative stress; Fraud & Poole, 2011). In fact, P. aeruginosa is exposed to high levels of reactive oxygen species in cystic fibrosis lungs, where mexXY overexpression mutants accumulate due to DNA damage resulting from the inflammatory response (Smith et al, 2006;Fraud & Poole, 2011).…”

“…oxidative stress; Fraud & Poole, 2011). In fact, P. aeruginosa is exposed to high levels of reactive oxygen species in cystic fibrosis lungs, where mexXY overexpression mutants accumulate due to DNA damage resulting from the inflammatory response (Smith et al, 2006;Fraud & Poole, 2011). The multidrug-resistant O12 clone clusters very tightly, includes only clinical isolates and emerged during the 1980s, perhaps by selection from heavy antibiotic use (Pirnay et al, 2009;Woodford et al, 2011).…”

Adaptive and Mutational Resistance: Role of Porins and Efflux Pumps in Drug Resistance

“…The presence of oxidative compounds is another factor that contributes to the dysregulation of efflux pump expression. Thus, the aminoglycoside pump MexXY of P. aeruginosa is induced by reactive oxygen species (ROS) via the product of the gene PA5471 (65). This is relevant to infections because the microorganism will encounter ROS, e.g., during infections of the CF lung.…”

“…This pump has also been shown to be involved in the antagonism between divalent cations and aminoglycosides (147). The induction of mexXY by aminoglycosides requires the upregulation of the gene PA5471, which in turn inhibits the repressor MexZ (65).…”