In vitro characterization of the anti-bacterial activity of SQ109 against Helicobacter pylori

• Published in: PloS one Vol. 8; no. 7; p. e68917
• Main Authors: Makobongo, Morris O, Einck, Leo, Peek, Jr, Richard M, Merrell, D Scott
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 25-07-2013; Public Library of Science (PLoS)
• Subjects: Adamantane - analogs & derivatives; Adamantane - pharmacology; Amoxicillin; Amoxicillin - pharmacology; Antibiotics; Antimicrobial activity; Antitubercular agents; Antitubercular Agents - pharmacology; Antiulcer agents; Bacteria; Bacterial infections; Bactericidal activity; Bioavailability; Cell division; Cell Membrane - drug effects; Cell Membrane - ultrastructure; Chloramphenicol; Chloramphenicol - pharmacology; Clarithromycin; Clarithromycin - pharmacology; Clinical isolates; Clinical trials; Dilution; Drug development; Drug resistance; Drug Resistance, Multiple, Bacterial - drug effects; Drug Synergism; Drugs; Duodenal Ulcer - complications; Duodenal Ulcer - drug therapy; Duodenal Ulcer - microbiology; Duodenitis - complications; Duodenitis - drug therapy; Duodenitis - microbiology; Electron microscopy; Ethane; Ethylene; Ethylenediamines; Ethylenediamines - pharmacology; Gastric cancer; Gastritis; Gastritis - complications; Gastritis - drug therapy; Gastritis - microbiology; Gastroenterology; Genomes; Health aspects; Health sciences; Helicobacter Infections - complications; Helicobacter Infections - drug therapy; Helicobacter Infections - microbiology; Helicobacter pylori; Helicobacter pylori - drug effects; Helicobacter pylori - growth & development; Helicobacter pylori - isolation & purification; Helicobacter pylori - ultrastructure; Humans; Hydrogen-Ion Concentration; Immunology; Killing; Kinetics; Medical research; Medical schools; Medicine; Metronidazole; Metronidazole - pharmacology; Microbial drug resistance; Microbial Sensitivity Tests; Microscopy, Electron; Minimum inhibitory concentration; Multidrug resistance; Oral administration; Pathogens; Patient compliance; Peptic ulcer; Peptic ulcers; pH effects; Pharmacology; Pretreatment; Rats; Rifampin; Stomach; Stomach cancer; Stomach Ulcer - complications; Stomach Ulcer - drug therapy; Stomach Ulcer - microbiology; Strains (organisms); Streptococcus infections; Thermal stability; Tuberculosis; Ulcers; United States > US; Maryland
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0068917

The most evident challenge to treatment of Helicobacter pylori, a bacterium responsible for gastritis, peptic ulcers and gastric cancer, is the increasing rate of resistance to all currently used therapeutic antibiotics. Thus, the development of novel therapies is urgently required. N-geranyl-N'-(2-adamantyl) ethane-1, 2-diamine (SQ109) is an ethylene diamine-based antitubercular drug that is currently in clinical trials for the treatment of tuberculosis (TB). Previous pharmacokinetic studies of SQ109 revealed that persistently high concentrations of SQ109 remain in the stomach 4 hours post oral administration in rats. This finding, combined with the need for new anti-Helicobacter therapies, prompted us to define the in vitro efficacy of SQ109 against H. pylori. Liquid broth micro-dilution was used for susceptibility studies to determine the antimicrobial activity of SQ109 against a total of 6 laboratory strains and 20 clinical isolates of H. pylori; the clinical isolates included a multi-drug resistant strain. All strains tested were susceptible to SQ109 with MIC and MBC ranges of 6-10 µM and 50-60 µM, respectively. SQ109 killing kinetics were concentration- and time-dependent. SQ109 killed H. pylori in 8-10 h at 140 µM (2MBCs) or 4-6 h at 200 µM (~3MBCs). Importantly, though the kinetics of killing were altered, SQ109 retained potent bactericidal activity against H. pylori at low pH. Additionally, SQ109 demonstrated robust thermal stability and was effective at killing slow growing or static bacteria. In fact, pretreatment of cultures with a bacteriostatic concentration of chloramphenicol (Cm) synergized the effects of typically bacteriostatic concentrations of SQ109 to the level of five-logs of bacterial killing. A molar-to-molar comparison of the efficacy of SQ109 as compared to metronidazole (MTZ), amoxicillin (AMX), rifampicin (RIF) and clarithromycin (CLR), revealed that SQ109 was superior to MTZ, AMX and RIF but not to CLR. Finally, the frequency of resistance to SQ109 was low and electron microscopy studies revealed that SQ109 interacted with bacterial inner membrane and cytoplasmic content(s). Collectively, our in vitro data demonstrate that SQ109 is an effective monotherapy against susceptible and multi-drug resistant strains of H. pylori and may be useful alone or in combination with other antibiotics for development as a new class of anti-Helicobacter drugs.