The effect of nitric oxide combined with fluoroquinolones against Salmonella enterica serovar Typhimurium in vitro

Abstract

Two regulons, soxRS and marRAB, are associated with resistance to quinolones or multiple antibiotic in Salmonella enterica serovar Typhimurium. These regulons are activated by nitric oxide and redox-cycling drugs, such as paraquat and cause on activation of the acrAB-encoded efflux pump. In this study, we investigated the effect of nitric oxide (NO) It has been shown before that endothelial (eNOS), neuronal and inducible (iNOS) types of nitric oxide (NO) synthases are involved in the production of NO in healthy humans and contribute to the intracellular killing of intracellular pathogens like Salmonella, Legionella pneumophila, Mycobacterium tuberculosis and Leishmania (Long et al. 1999). These pathogens include in their infection pathogenesis a phase during which they grow within macrophages (Eriksson et al. 2000). High-output pathways for production of reactive oxygen intermediates via the respiratory burst and reactive nitrogen intermediates via iNOS are presently the major molecularly defined means by which activated macrophages are thought to inhibit facultative or obligate intracellular pathogens (Shiloh & Nathan 2000). The cytotoxicity promoted by NO mainly depends on the interaction of NO with iron-containing moieties of the key enzymes of DNA replication and respiratory cycle in the target cells (Moncado & Higgs 1993). As NO has other important functions in metabolic processes in humans, the possible occurence of an unaccetaple side effect is a major drawback in the usage of NO for antimicrobial chemotherapy. Instability, limited solubility and the absence of a reliable delivery method complicates further the consideration of NO as an antimicrobial agent. NO-nucleophile complexes termed diazeniumdiolates are compounds with such specifications like the capability of releasing NO in aqueous or low pH environments without the need of a redox reaction or electron transfer and might be useful to overcome those barriers to develop an effective antimicrobial chemotherapy based on NO (McElhaney-Feser et al. 1998 Since S. typhimurium is an intracellular pathogen, antibiotics are to be effective needed to achieve high intracellular concentrations. Fluoroquinolones, including ofloxacin, ciprofloxacin, pefloxacin, and sparfloxacin have been shown to achieve high intracellular concentrations (Schüler et al. 1997).In this study, initially, we investigated the effect of NO against S. typhimurium and further interaction with ofloxacin, ciprofloxacin, and pefloxacin between NO was evaluated against clinical isolates and mutant strains in vitro. MATERIALS AND METHODSBacterial strains - Table I shows the bacteria used in this study.Antibacterial agents -NO donor DETA-NO {(Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate} was kindly gifted by Joseph A Hrabie and Larry Keefer, National Cancer Institute, Frederick Cancer Research Center, Frederick, Md. Ofloxacin, ciprofloxacin, pefloxacin were obtained "Hoechst Marion Roussel", "Bayer Turk Kimya San. Ltd. Sti.", "Eczacibasi Rhone Poulenc", respective...

Efflux-Mediated Drug Resistance in Bacteria

“…Typhimurium. [678] RamR repressor controls RamA expression (and therefore AcrAB expression) in Salmonella , and most MDR clinical isolates had mutations in the ramA gene. [679]…”

Two-pronged survival strategy for the major cystic fibrosis pathogen, Pseudomonas aeruginosa, lacking the capacity to degrade nitric oxide during anaerobic respiration

“…The most extensively studied proteins involved in NO detoxification are flavohemoglobin (Hmp or NOD (Hausladen et al, 2001) and flavorubredoxin (FlavoRb) in Escherichia coli. NO exposure also triggers activation of the soxRS regulon, members of which include the superoxide dismutase (SOD) and antibiotic efflux pumps in both E. coli and Salmonella typhimurium (Vasil'eva et al, 2001;Coban and Durupinar, 2003). Recent data indicate that Hmp is activated in response to NO even under anaerobic conditions, and NO-mediated modification of FNR, an E. coli ANR homolog, was suggested as a link between NO stress and anaerobic hmp transcription (Cruz-Ramos et al, 2002).…”

“…Recent data indicate that Hmp is activated in response to NO even under anaerobic conditions, and NO-mediated modification of FNR, an E. coli ANR homolog, was suggested as a link between NO stress and anaerobic hmp transcription (Cruz-Ramos et al, 2002). NO exposure also triggers activation of the soxRS regulon, members of which include the superoxide dismutase (SOD) and antibiotic efflux pumps in both E. coli and Salmonella typhimurium (Vasil'eva et al, 2001;Coban and Durupinar, 2003). Because NO can react with superoxide (O 2 À ) to produce highly destructive peroxynitrite (ONOO À ), higher levels of SOD are required for protection of NO-treated bacteria (Nunoshiba et al, 1993).…”