Antibacterial Effects Of Zn On Enteric Pathogens

1136 Words 5 Pages
Results of the present investigation indicate that both, Zn-gluconate and Zn-sulphate, inhibit the growth of G. lamblia trophozoites in vitro. To date, there are no reports about the effect of Zn on gastrointestinal parasites. Very few studies have so far been conducted on the antibacterial effect of various salts of Zn on enteric pathogens. An in vitro study conducted by Surjawidjaja et al. (2003) showed that Zn-sulfate at concentrations between 1.2 and 1.8 mg/ml inhibited the growth in enteric pathogens commonly associated with diarrheal disease (Salmonella typhi, Salmonella groups A, B, C, D and E, Escherichia coli, Enterobacter, Shigella and Vibrio cholera). Our results seem to indicate that Giardia is more sensitive to Zn than these enteric …show more content…
Zn is an essential element for microorganisms and higher organisms because it is involved in many vital cellular reactions at its low endogenous concentrations, acting as a cofactor needed for catalytic and structural activities [36, 37]. Zn ion concentrations of 10-5-10-7 M are required for optimal bacterial growth of most microorganisms in vitro [38]. However, it is claimed that high zinc ion concentrations may have some antibacterial properties [39]. Zn concentration is regulated under physiological conditions by several transporters [40, 41], so that Zn ions are essentially nontoxic to higher organisms. Although homeostasis regulates Zn uptake by cells, it does not control zinc adsorption to cell membranes. Among the mechanisms proposed for the antimicrobial effect of Zn, a direct interaction with microbial membranes leading to membrane destabilization and enhanced permeability has been discussed. Cellular internalization of Zn and the production of active oxygen species have been proposed in earlier studies. Increase of Zn concentrations above optimal levels perturbs its homeostasis and allows its entry inside cells, so that Zn starts being cytotoxic to prokaryotes above a concentration of ∼10−4 M [38, …show more content…
lamblia trophozoites attach to the intestinal villi via a specialized microtubule structure, the ventral disc [44]. The mechanism of attachment has been proposed to involve suction generated either by the ventral disc itself or by the regular beating of the ventral flagella [45-47]. For Giardia pathogenesis, the contact between trophozoite and epithelium is a key determinant. Therefore, interventions that disrupt adherence to epithelium and subsequent downstream events hold promise to be an effective non-antibiotic therapy against giardiasis. On the other hand, it has been described that the surface and flagella of the Giardia trophozoite are covered by a protein coat composed of a single variant-specific surface protein (VSP) [48, 49]; these are metal-binding proteins and different cloned trophozoite lines all bound zinc [50]. The benefit of metal binding of VSPs to Giardia is unknown. Most interestingly, no other surface-residing Zn-finger protein exists in any other organism [51]. Giardia has abundant surface-located Zn-finger proteins which may be particularly susceptible to Zn availability within the host. The potential metal-binding properties of G. lamblia suggest unusual ways that the parasite may interact with its host, but whether the availability of Zn within the host could affect the parasite´s VSP´s mechanisms is not clear, especially in view of the non-specificity of metal binding by the VSPs

Related Documents