Exposure to sub-inhibitory concentrations of cefotaxime enhances the systemic colonization of Salmonella Typhimurium in BALB/c mice

Abstract

It has been proposed that sub-inhibitory concentrations of antibiotics play a role in virulence modulation. In this study, we evaluated the ability of Salmonella enterica serovar Typhimurium (hereafter S. Typhimurium) to colonize systemically BALB/c mice after exposure to a sub-inhibitory concentration of cefotaxime (CTX). In vivo competition assays showed a fivefold increase in systemic colonization of CTX-exposed bacteria when compared to untreated bacteria. To identify the molecular mechanisms involved in this phenomenon, we carried out a high-throughput genetic screen. A transposon library of S. Typhimurium mutants was subjected to negative selection in the presence of a sub-inhibitory concentration of CTX and genes related to anaerobic metabolism, biosynthesis of purines, pyrimidines, amino acids and other metabolites were identified as needed to survive in this condition. In addition, an impaired ability for oxygen consumption was observed when bacteria were cultured in the presence of a sub-inhibitory concentration of CTX. Altogether, our data indicate that exposure to sub-lethal concentrations of CTX increases the systemic colonization of S. Typhimurium in BALB/c mice in part by the establishment of a fitness alteration conducive to anaerobic metabolism.

Adaptation Through Lifestyle Switching Sculpts the Fitness Landscape of Evolving Populations: Implications for the Selection of Drug-Resistant Bacteria at Low Drug Pressures

“…It is predicted that selection environments with low drug concentrations strongly select against costly resistance mutations (Andersson and Hughes 2012;Hughes and Andersson 2015), though experimental tests of this prediction are limited. Further, sublethal antibiotic doses facilitate a number of other adaptations in bacteria such as biofilm formation (Nguyen et al 2014;Aka and Haji 2015;Oliveira et al 2015), altered metabolic signatures (Wu et al 2014;Molina-Quiroz et al 2015), or transcriptional deregulation (Hesketh et al 2011). These adaptations are likely to alter the fitness effects of drug-resistant mutations.…”

Changes in physiology and virulence during the selection of resistant Yersinia ruckeri mutants under subinhibitory cefotaxime concentrations

“…It seems that the differences in the production of 50S ribosomal protein L16, thiol peroxidase, OmpF and NADH-quinone oxidoreductase proteins, which were found between Y. ruckeri 150 and 150 CTX strains, correlate with the switch to anaerobic metabolism caused by exposure to subinhibitory concentrations of cefotaxime as it has been previously described in Salmonella Typhimurium by Molina-Quiroz et al (2015). According to these authors, this response would be a global defence mechanism against cefotaximemediated stress.…”

“…Interestingly, in Salmonella Typhimurium exposure to subinhibitory concentrations of this antibiotic promotes systemic colonization in mice (Molina‐Quiroz et al, ). According to Molina‐Quiroz et al (), cefotaxime induces in Salmonella Typhimurium a metabolic switch to anaerobic metabolism and the biosynthesis of essential metabolites, allowing the bacterium a preadaptation that would enhance systemic colonization in mice. It is a response that seems to represent a global defence mechanism against different classes of stress, since it has been also observed in different bacterial models after exposure to metals, high salt concentrations and phage infection (Fallico, Ross, Fitzgerald, & McAuliffe, ; Fu, Wang, Yin, Du, & Kan, ; Molina‐Quiroz et al, ).…”

“…Both bacterial fitness and virulence are influenced by antibiotic resistance, and the link between them is affected by different genetic mechanisms such as co‐selection, compensatory mutation and global responses (Beceiro, Tomás, & Bou, ). There are many studies in which increased resistance has been linked to increased virulence (Eswarappa, Panguluri, Hensel, & Chakravortty, ; Molina‐Quiroz et al, ; Verbrugghe et al, ). This fact is very important if we take into account that in certain situations, such as the hospital environment, antibiotic resistance is considered a key factor in the development of infection.…”

Lactobacillus bulgaricus, Lactobacillus rhamnosus and Lactobacillus paracasei Attenuate Salmonella Enteritidis, Salmonella Heidelberg and Salmonella Typhimurium Colonization and Virulence Gene Expression In Vitro

“…To obtain LAB CFSN, overnight cultures of LD/LP/LR were centrifuged (3000× g , 15 min, 4 °C) and the supernatant was filtered using 0.22 µm syringe filter [ 50 ]. The SIC of LAB supernatants was estimated as previously described [ 51 , 52 ]. Approximately 6 log 10 CFU/mL of Salmonella was inoculated into 10 mL of TSB supplemented with different concentrations of CFSN (0.5%, 1%, 2.5%, 5%, 7.5%, 10%, 15%, and 20%) and incubated at 37 °C for 24 h. Following incubation, the surviving Salmonella population was enumerated by dilution and plating on TSA.…”