1887

Abstract

The susceptibility of and to pH and the effect of pepsin-mediated proteolysis were investigated. This was to establish the relative importance of their bacterial killing properties in gastric juice. Solutions in the pH range 1.5–7.4 with or without pig pepsin A were used, together with seven gastric juice samples obtained from patients undergoing routine gastric collection. C690 (a capsulate strain), K-12 (a rough mutant) and E5 were selected as the test organisms. Suspensions of bacteria (1×10 ml and 1×10 ml) were pre-incubated with test solutions at 37 °C for up to 2 h, and then cultured to establish the effect on subsequent growth. Survival of bacteria was diminished at pHs of less than 3.5, whereas killing required a pH of less than 2.5. Pre-incubation with pig pepsin at 0.5, 1.0 and 2.0 mg ml at pH 3.5 reduced viable counts by 100 % for 690 and K-12 after 100 min incubation. With , the viable counts decreased to 50 % of the control after 20 min incubation in 1 mg pepsin ml at pH 2.5, 3.0 and 3.5. The gastric juices showed bactericidal activity at pH 3.5, and the rate of killing was juice dependent, with complete death of 690 occurring between 5 and 40 min post-incubation. Thus, killing of and occurs optimally at pHs of less than 2.5. At pH 3.5, little effect is observed, whereas addition of pepsin alone or in gastric juice causes a marked increase in bacterial susceptibility, suggesting an important role for proteolysis in the killing of bacteria.

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2006-09-01
2024-03-28
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References

  1. Ahluwalla J., Tinker A., Clapp L. H., Duchen M. R., Abramor A. Y., Pope S., Nobles M., Segal A. W. 2004; The large conductance Ca2+-activated K+ channel is essential for innate immunity. Nature 427:853–858 [CrossRef]
    [Google Scholar]
  2. Arnold K. W., Kaspar C. W. 1995; Starvation- and stationary-phase-induced acid tolerance in E. coli O157 : H7. Appl Environ Microbiol 61:2037–2039
    [Google Scholar]
  3. Balan K. K., Jones A. T., Roberts N. B., Pearson J. P., Critchley M., Jenkins S. A. 1996; The effects of Helicobacter pylori colonization on gastric function and the incidence of portal hypertensive gastropathy in patients with cirrhosis of the liver. Am J Gastroenterol 91:1400–1406
    [Google Scholar]
  4. Booth I. R. 1985; Regulation of cytoplasmic pH in bacteria. Microbiol Rev 49:359–378
    [Google Scholar]
  5. Borriello S. P., Reed P. J., Dolby J. M., Barclay F. E., Webster A. D. 1985; Micobial and metabolic profiles of the achlorhydric stomach: comparisons of pernicious and hypogammaglobulinaemia. J Clin Pathol 38:946–953 [CrossRef]
    [Google Scholar]
  6. De Alwis M. C. L. 1970; Some factors influencing the survival of and multiplication of pathogenic E. coli in the gastro-intestinal tract . PhD thesis University of Liverpool;
  7. Ferroro R. L., Hazell S. L., Lee A. 1988; The urease enzymes of C. pylori and a related bacterium. J Med Microbiol 27:33–40 [CrossRef]
    [Google Scholar]
  8. Garren M. G., Harrison M. A., Russell S. A. 1997; Retention of acid tolerance and acid shock response of Escherichia coli O157 : H7 and non O157 : H7 isolates. J Food Protect 60:1480–1482
    [Google Scholar]
  9. Garrod L. P. 1939; A study of of the bactericidal power of hydrochloric acid and of gastric juice. St Bart Hosp Rep 72:145–167
    [Google Scholar]
  10. Gianelli R. A., Broitman S. A., Zamchek N. 1972; Gastric acid barrier to ingested microorganisms in man: studies in vivo and in vitro. Gut 13:251–256 [CrossRef]
    [Google Scholar]
  11. Gray A. J. D., Shiner M. 1967; Influence of gastric pH on gastric and jejunal flora. Gut 8:574–581 [CrossRef]
    [Google Scholar]
  12. Jordan S. L., Glover J., Malcolm L., Thomas-Carter F. M., Booth I. R., Park S. F. 1999; Augmentation of killing of Escherichia coli O157 by combinations of lactate, ethanol, and low-pH conditions. Appl Environ Microbiol 65:1308–1311
    [Google Scholar]
  13. Kim S., Chamberlain A. K., Bowie J. U. 2004; Membrane channel structure of Helicobacter pylori vacuolating toxin; role of multiple GXXXG motifs in cylindrical channels. Proc Natl Acad Sci U S A 101:5988–5991 [CrossRef]
    [Google Scholar]
  14. Martinsen T. C., Bergh K., Waldum H. L. 2005; Gastric juice: a barrier against infectious diseases. Basic Clin Pharm Toxicol 96:94–102 [CrossRef]
    [Google Scholar]
  15. Nibbering P. H., Ranesbergen E., Welling M. M., VanBerkel L. A., VanBerkel P. H. C., Pauwels E. K. J., Nuijens J. H. 2001; Human lactoferrin and peptides derived from its N terminus are highly effective against infections with antibiotic-resistant bacteria. Infect Immun 69:1469–1476 [CrossRef]
    [Google Scholar]
  16. Niedhardt F. C. 1987; Chemical composition of Escherichia coli . In Escherichia coli and Salmonella typhimurum pp  3–6 Edited by Niedhardt F. C. Washington, DC: American Society for Microbiology;
    [Google Scholar]
  17. Roberts N. B., Taylor W. H. 1978; Effect of cyclo-alkyl lactamimides upon human pepsins and pepsinogens. Clin Sci Mol Med 54:181–185
    [Google Scholar]
  18. Rosina A. 1982; Human intestinal flora in health and disease . PhD thesis University of Liverpool;
  19. Ryley H. C. 2001; Human antimicrobial peptides. Revs Med Microbiol 12:177–186 [CrossRef]
    [Google Scholar]
  20. Small P. L. C., Blankenhorn D., Welty D., Zinser E., Slaczewski J. L. 1994; Acid and base resistance in E. coli and Shigella flexneri : role of rpoS and growth pH. J Bacteriol 176:1729–1737
    [Google Scholar]
  21. Waterman S. R., Small P. L. C. 1998; Acid-sensitive pathogens are protected from killing under extremely acidic conditions of pH when they are inoculated onto certain solid food sources. Appl Environ Microbiol 64:3882–3886
    [Google Scholar]
  22. Xu J., Xu X., Verstraete W. 2001; The bactericidal effect and chemical reactions of acidified nitrite under conditions simulating the stomach. J Appl Microbiol 90:523–529 [CrossRef]
    [Google Scholar]
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