Susceptibility of Helicobacter pylori and its urease activity to the peroxidase-hydrogen peroxide-thiocyanate antimicrobial system

Abstract

The susceptibility of Helicobacter pylori to the antimicrobial system involving lactoperoxidase, hydrogen peroxide and thiocyanate was investigated. The inhibitory effect of the system on the urease activity of H. pylori, which plays a role in its colonisation of the stomach, was also investigated. Twelve H. pylori strains examined, including 10 clinical isolates, were all inhibited by the peroxidase system in brain-heart infusion broth supplemented with fetal calf serum, but to different extents. The killing effect was observed within 3 h. Although bacterial viability recovered afterwards, there was still a clear difference between cultures incubated in the presence of the complete system and control cultures incubated in the absence of lactoperoxidase, after incubation for 24 h. The urease activity and viability of H. pylori were both inactivated by this system in phosphate buffer. These effects were dependent on the concentrations of both lactoperoxidase and hydrogen peroxide and were abolished by the addition of cysteine. Furthermore, these effects were observed when bovine lactoperoxidase was replaced by recombinant human lactoperoxidase or native or recombinant human myeloperoxidase. The peroxidase system found in saliva and milk may contribute to the host defence against H. pylori infection and inhibition of transmission via the oral route.

Sensitivity of Helicobacter pylori to an innate defence mechanism, the lactoperoxidase system, in buffer and in human whole saliva

“…None of the strains were sensitive to H 2 O 2 or KSCN alone (data not shown). These results are in accordance with those reported by Shin et al (2002).…”

“…It enables H. pylori to survive in acidic pH, since ammonia increases the gastric pH levels in the microenvironment of the bacterial cells. The LP system has been shown to reduce the urease activity of H. pylori (Shin et al, 2002), but in our experiment the constant pH was more likely to have been due to the citrate in reaction mixtures at pH 5. Urease production of H. pylori is dramatically reduced in citrate buffer at pH 5 (Bauerfeind et al, 1997).…”

“…À -H 2 O 2 system (the LP system), catalytically similar to the salivary peroxidase system, is known to inhibit many Gram-negative bacteria, including H. pylori, in vitro (Thomas & Aune, 1978a, b;Courtois et al, 1992;Shin et al, 2002). To extend the currently limited knowledge, we investigated the effects of the LP system on several H. pylori strains, including clinical Abbreviation: LP, lactoperoxidase.…”

Inactivating effects of the lactoperoxidase system on bacterial lyases involved in oral malodour production

“…It catalyses the hydrogen peroxide (H 2 O 2 )-dependent oxidation of thiocyanate (SCN -) to hypothiocyanite (OSCN -), which is a potent antimicrobial agent against bacteria, fungi and viruses (Thomas et al, 1991;Sharma et al, 2013). and inhibits various functions, such as glycolysis (Adamson & Pruitt, 1981), the membrane transport of sugars and amino acids (Hamon & Klebanoff, 1973;Mickelson, 1977), respiration (Law & John, 1981;Shin et al, 2001), and the urease activity of Helicobacter pylori (Shin et al, 2002).…”

Orally Administered Lactoperoxidase Increases Expression of the FK506 Binding Protein 5 Gene in Epithelial Cells of the Small Intestine of Mice: A DNA Microarray Study

“…1,2) LPO is an enzyme that catalyses the hydrogen peroxide (H 2 O 2 )-dependent oxidation of thiocyanate (SCN À ) to produce the hypothiocyanate anion (OSCN À ), which has inhibitory activity against a wide variety of microorganisms, including gram-positive and gram-negative bacteria, fungi, and viruses. 3,4) The in vivo antibacterial activity of LPO and its substrates has been demonstrated in the sheep airway. 5) Direct antimicrobial effects in the oral cavity and gastrointestinal tract have been achieved by orally administered LPO.…”