Pseudomonas aeruginosa Polynucleotide Phosphorylase Controls Tolerance to Aminoglycoside Antibiotics by Regulating the MexXY Multidrug Efflux Pump

Abstract

Pseudomonas aeruginosa is an opportunistic pathogen that shows high intrinsic resistance to a variety of antibiotics. The MexX-MexY-OprM efflux pump plays an important role in the bacterial resistance to aminoglycoside antibiotics. Polynucleotide phosphorylase (PNPase) is a highly conserved exonuclease that plays important roles in RNA processing and bacterial response to environmental stresses. Previously, we demonstrated that PNPase controls the tolerance to fluoroquinolone antibiotics by influencing the production of pyocin in P. aeruginosa. In this study, we found that mutation of the PNPase coding gene (pnp) in P. aeruginosa increases the bacterial tolerance to aminoglycoside antibiotics. We further demonstrate that upregulation of the mexXY genes is responsible for the increased tolerance in the pnp mutant. Furthermore, our experimental results revealed that PNPase controls translation of the armZ mRNA through its 5′ untranslated region (5′-UTR). ArmZ had previously been shown to positively regulate the expression of mexXY. Therefore, our results revealed a novel role of PNPase in the regulation of armZ and subsequently the MexXY efflux pump.

Involvement of Acquired Tobramycin Resistance in the Shift to the Viable but Non-Culturable State in Pseudomonas aeruginosa

“…The greater activity of the MexXY-OprM in P. aeruginosa C30 compared to P. aeruginosa PAO1-N after exposure to tobramycin may thus result in an early shift to the VBNC state of most of the bacterial population, followed by VBNC cell reactivation and multiplication as a consequence of drug extrusion, a behavior not observed in the absence of tobramycin. This is consistent with our previous data, which evidenced the role of the MexXY-OprM pump in the tolerance of P. aeruginosa to tobramycin [13] and with further studies describing efflux as a typical strategy through which this pathogen counteracts the bactericidal activities of antibiotics [14,15]. Accordingly, the lack of VBNC cell production by P. aeruginosa AR86 might have been due to the modification of tobramycin by Ant(2")-Ia before reaching the intracellular environment, which prevents the action of tobramycin either as a stress factor or as a gene expression inducer.…”

Rapid Detection of Multi-Resistance Strains Carrying mcr-1 Gene Using Recombinase-Aided Amplification Directly on Clinical Samples

“…The 2020 Clinical Laboratory Standards Institute’s threshold was used to as reference. In addition, the MICs of colistin and polymyxin B were determined by the twofold serial dilution method, as previously described ( Fan et al, 2021 ). Briefly, the strains harboring mcr -1 genes were grown in LB broth at 37°C until the optical density at 600 nm (OD600) reached 1.0.…”

Antibiotic influx and efflux in Pseudomonas aeruginosa: Regulation and therapeutic implications

“…Transcriptional expression of armZ is repressed by the TCS PmrA/PmrB which is activated by halogenated indoles (Dou et al., 2023 ). In addition, polynucleotide phosphorylase (PNPase) was found to control the translation of the armZ mRNA through its 5′ UTR (Fan et al., 2021 ). Therefore, mutations in the PNPase‐encoding gene upregulate the expression of the mexXY genes and increase the resistance of P. aeruginosa to aminoglycoside antibiotics (Fan et al., 2021 ).…”

“…In addition, polynucleotide phosphorylase (PNPase) was found to control the translation of the armZ mRNA through its 5′ UTR (Fan et al., 2021 ). Therefore, mutations in the PNPase‐encoding gene upregulate the expression of the mexXY genes and increase the resistance of P. aeruginosa to aminoglycoside antibiotics (Fan et al., 2021 ). Furthermore, the expression of armZ is upregulated by oxidative stress, PA2798 , and downregulated by suhB , fmt , folD , rplY , and rplU‐rpmA (Caughlan Ruth et al., 2009 ; El'Garch et al., 2007 ; Fraud & Poole, 2011 ; Genova et al., 2023 ; Lau Calvin et al., 2012 ; Shi et al., 2015 ).…”