Ciprofloxacin-Mediated Mutagenesis Is Suppressed by Subinhibitory Concentrations of Amikacin in Pseudomonas aeruginosa

Abstract

Resistance to antibiotics is a global health problem. Activation of the SOS response, and the subsequent elevation in mutagenesis, contributes to the appearance of resistance mutations. Among currently used drugs, quinolones are the most potent inducers of the SOS response. In the present study, we show that amikacin inhibits ciprofloxacin-mediated SOS induction and mutagenesis in Pseudomonas aeruginosa.KEYWORDS Pseudomonas aeruginosa, SOS response, ciprofloxacin, recA A ntibiotics may cause genetic changes involving different pathways, and one of them is the induction of error-prone polymerases mediated by SOS response (1, 2). Ciprofloxacin (CIP), one of the antimicrobials of choice for the treatment of Pseudomonas aeruginosa, induces the SOS response (3-5) by interfering with gyrase or topoisomerase activity (6, 7). The SOS regulon controls 15 genes, including imuABC and dinB (4, 5), which encode error-prone polymerases (8,9). By inducing the SOS response, ciprofloxacin increases mutagenesis (e.g., see references 10 and 11), facilitating the appearance of drug resistance.We investigated the effect of antibiotic combinations on the SOS response and mutagenesis induced by ciprofloxacin in P. aeruginosa PAO1. recA is among the SOS-regulated genes in this organism (4,5). To analyze the induction of the SOS response, we constructed a chromosomal PrecA-lux reporter. The regulatory region upstream from recA (Ϫ501 bp relative to the start codon) was cloned into the pUC18T-mini-Tn7T-lux-Gm plasmid (12) and transferred to P. aeruginosa for integration at attTn7, resulting in strain attTn7::PrecA-lux. The effect of antibiotics on the expression of the reporter was evaluated in solid medium using disk-based qualitative assays. The PrecA-lux strain was diluted to an optical density at 260 nm (OD 600 ) of 0.1. Fifty microliters of this dilution was seeded on Mueller-Hinton (MH) agar, and test antibiotic disks and CIP (5 g) disks (Sensifar-Cefar, Brazil) were placed close to one another to observe the effect of the antibiotic interaction on recA expression. Luciferase activity was detected in the ChemiDoc MP system (Bio-Rad, USA).Amikacin (AMI), imipenem, meropenem, polymyxin B, ceftazidime, cefepime, and aztreonam were tested, representing different drug classes. We found that amikacin is not an inducer of the SOS response but is in fact a strong inhibitor of recA induction by sub-MICs of ciprofloxacin (Fig. 1A). Amikacin is an aminoglycoside derived from kanamycin (13). Aminoglycosides bind, with high affinity, to the A-site on the 16S rRNA of the 30S ribosome (14) and can cause mRNA decoding errors, block mRNA and tRNA translocation, and inhibit ribosome recycling (15).

Ecological effects of stress drive bacterial evolvability under sub-inhibitory antibiotic treatments

“…The following studies contain relevant data, but were excluded from the analysis despite matching our a priori inclusion criteria: Gutierrez et al [5], Schroder et al [36] (data available, but in a different representation or in a summary form); Kohanski et al [4], Nair et al [37], Peng et al [38], Bunnell et al [39], Cairns et al [40], Thi et al [41], Song et al [42], Valencia et al [43], Nagel et al [44] (raw data unavailable or no answer from the author who kept the raw data).…”

Expression of different ParE toxins results in conserved phenotypes with distinguishable classes of toxicity

“…A change in cell morphology has been previously characterized as a survival mechanism of E. coli present in urinary tract infections (French, Cote, Stokes, Truant, & Brown, ; Justice, Hunstad, Cegelski, & Hultgren, ; Klein, Palarasah, Kolmos, Moller‐Jensen, & Andersen, ), and CIP‐induced filaments were found to give rise to antibiotic‐resistant populations (Bos et al, ). This survival mechanism is linked to pathway activation in response to DNA breaks, thus promoting error‐prone repair and driving evolution (Recacha et al, ; Torres‐Barcelo et al, ; Valencia, Esposito, Spira, Blazquez, & Galhardo, ). Further studies have identified that the coordination of DNA repair after DNA damage, arising from CIP in this study, can accurately predict the emergence of a persister phenotype (Mok & Brynildsen, ).…”

Modeling the control of bacterial infections via antibiotic-induced proviruses

“…There are many mechanisms of resistance to quinolones and fluoroquinolones. However, sub-inhibitory concentrations of several antibiotics are known to induce SOS but not result directly in cell death [34,[74][75][76][77]]. Therefore we model the impact of phage induction on P. aeruginosa population size with and without antibiotic resistance.…”

“…Note that not all antibiotics induce phage [34], so we focus only on the types of antibiotics known to do so (e.g., quinolones like Levofloxacin and Ciprofloxacin) [8,73]. We assume that even antibiotic-resistant bacteria induce viruses in the presence of antibiotics, which has been demonstrated for several classes of antibiotics [34,[74][75][76][77].…”