The antimicrobial interaction of acidified nitrite with other physiologically active compounds (PAC), the potential host defence mechanism of dietary nitrate
Transfer of nitrite at salivary concentrations enhance the antimicrobial activity of stomach acid against food borne pathogens and may be involved in the host defence of humans and animals. Studies from experimental animals, microbial tests, human ex vivo and in vivo investigations support the hypothesis that dietary nitrate is beneficial for health. The positive findings that acidified nitrite is antimicrobial at the acidic conditions of the stomach is viewed in conjunction with the potential production of nitrogen, intermediates such as NO, a molecule of significant importance in science. This led to propose that acidified nitrite can kill or inhibit enteric bacterial species that are associated with gastrointestinal diseases and could modify the antimicrobial effects of acidified nitrite by other physiologically active compounds. By a systematic exposure of selected enteric bacterial species to acidified nitrite and other PAC alone or in combinations, it was found that acidified nitrite, especially at low pH values was inhibitory to bacterial growth or killer of bacterial cells. Glutathione and vitamin C inhibited the antimicrobial effects of nitrite whilst thiocyanate and iodide enhanced it. Thiocyanate produced an effective antimicrobial activity that was comparable to nitrite but there was no synergistic antimicrobial interaction between acidified nitrite and thiocyanate. The addition of thiocyanate enhanced the antimicrobial effects of cow's milk in a pH-dependent activity. The overall results reported here suggested to conclude that dietary factors found in fruits and vegetables are not only beneficial in the supply of vitamins, antioxidants and enzymes but also antimicrobial agents that are worth investigation for therapeutic purposes.