PA3297 Counteracts Antimicrobial Effects of Azithromycin in Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa causes acute and chronic infections in human. Its increasing resistance to antibiotics requires alternative treatments that are more effective than available strategies. Among the alternatives is the unconventional usage of conventional antibiotics, of which the macrolide antibiotic azithromycin (AZM) provides a paradigmatic example. AZM therapy is associated with a small but consistent improvement in respiratory function of cystic fibrosis patients suffering from chronic P. aeruginosa infection. Besides immunomodulating activities, AZM represses bacterial genes involved in virulence, quorum sensing, biofilm formation, and motility, all of which are due to stalling of ribosome and depletion of cellular tRNA pool. However, how P. aeruginosa responds to and counteracts the effects of AZM remain elusive. Here, we found that deficiency of PA3297, a gene encoding a DEAH-box helicase, intensified AZM-mediated bacterial killing, suppression of pyocyanin production and swarming motility, and hypersusceptibility to hydrogen peroxide. We demonstrated that expression of PA3297 is induced by the interaction between AZM and ribosome. Importantly, mutation of PA3297 resulted in elevated levels of unprocessed 23S-5S rRNA in the presence of AZM, which might lead to increased susceptibility to AZM-mediated effects. Our results revealed one of the bacterial responses in counteracting the detrimental effects of AZM.

Crystal Structure of the Escherichia coli DExH-Box NTPase HrpB

“…Other bacterial RNA helicases were shown to be involved in bacterial stress responses, such as heat, cold, and oxidative stress (Owttrim, 2013;Tan et al, 2016). We could not demonstrate that a hrpB mutant is more sensitive to growth-restricting conditions of heat and cold shock or to oxidative stress in growth or survival assays in E. coli K12.…”

“…DEAD-box proteins are also known to play a role under oxidative stress conditions (Markkula et al, 2012), and mutation of the DExH-box protein HrpA of P. aeruginosa increased the sensitivity to oxidative stress in the presence of azithromycin (Tan et al, 2016). We therefore compared the survival of the wildtype and hrpB deletion mutants 1 hr after exposure of exponentially growing cells with 2 mM H 2 O 2 .…”

“…We could not demonstrate that a hrpB mutant is more sensitive to growth-restricting conditions of heat and cold shock or to oxidative stress in growth or survival assays in E. coli K12. Recently, the HrpA homolog PA3297 of P. aeruginosa was shown to be required for azithromycin resistance and enhanced the processing of the 5S-23S rRNA under ribosomal antibiotics stress (Tan et al, 2016). Thus, our future studies are aimed at analyzing whether the hrpB deletion mutant shows increased sensitivity to certain antibiotics and whether HrpB might be involved in responses to translation stress.…”

Acquired resistance to macrolides inPseudomonas aeruginosafrom cystic fibrosis patients

“…Yet, we argue that the highlighted mutations are of concern. First, they may compromise some of the macrolide antivirulence effects that are directly or indirectly dependent on their binding to ribosomes and subsequent protein synthesis inhibition [2,35]. Second, they may create a reservoir of resistance, possibly compromising the activity of future drugs acting on the same target.…”

Chitin Oligosaccharide (COS) Reduces Antibiotics Dose and Prevents Antibiotics-Caused Side Effects in Adolescent Idiopathic Scoliosis (AIS) Patients with Spinal Fusion Surgery

“…The overexpression of PA3297 (a DEAH-box helicase; DEAH, Asp-Glu-Ala-His) was found to be caused by the interaction between Azithromycin and ribosomes. The mutant PA3297 will increase unprocessed 23TS-5S rRNA in the presence of Azithromycin, which increases the sensitivity to Azithromycin-reduced effects, suggesting the bacterial reactions to counteract the effects of Azithromycin [32]. Lipopolysaccharides/lipooligosaccharides are abundant in the cell surface and increase antibiotics resistance in most Gram-negative bacteria.…”