Antimicrobial screening of zinc in the absence or presence of oleoresins and various resin acids

The highly synergistic, broad spectrum, antibacterial activity of organic acids and transition metals

For millennia, transition metals have been exploited to inhibit bacterial growth. We report here the potentiation of the anti-bacterial activity of transition metals by organic acids. Strong synergy between low, non-toxic concentrations of transition metals and organic acids was observed with up to ~1000-fold higher inhibitory effect on bacterial growth. We show that organic acids shuttle transition metals through the permeability barrier of the bacterial membrane, leading to increased influx of transition metals into bacterial cells. We demonstrate that this synergy can be effectively used to inhibit the growth of a broad range of plant and human bacterial pathogens, and suggest that a revision of food preservation and crop protection strategies may be in order. These findings bear significant biomedical, agricultural, financial and environmental opportunities.

The acute phase response in the Sudan plated lizard, Gerrhosaurus major

The Sudan plated lizard (Gerrhosaurus major), previously reported to be an afebrile species, was utilized in a series of experiments to test for various aspects of the acute phase response. Treatment of individuals with the antibiotic Baytril resulted in a slight (0.5 degree C) but significant reduction in mean selected body temperature (MSBT), while treatment with saline did not lower MSBT. Nonantibiotic treatment individuals had depressed plasma iron levels (86.6 +/- 22.4 micrograms Fe 100 ml-1 plasma) and treatment with Baytril produced a significant increase in plasma iron concentration (186.8 +/- 19.5 micrograms Fe 100 ml-1 plasma). Necropsy of randomly selected individuals indicated that animals obtained from the commercial supplier had Aeromonas, Arthrobacter, Pseudomonas and Salmonella infections and antibiotic treatment eliminated these infections. The growth rate of Aeromonas sobria is reduced when the bacteria are grown at 32 degrees C and reduced iron concentration compared to 34.5 degrees C and low iron concentration, which suggests that a fever response may not be beneficial in reducing bacterial growth. Saline injected, bacteria injected and antibiotic injected Gerrhosaurus major have high plasma zinc concentrations compared to the previously studied febrile species, Dipsosaurus dorsalis. This difference suggests that zinc concentrations in afebrile species deserve further study.

The protective effect of zinc on rosin and resin acid toxicity in human polymorphonuclear leukocytes and human gingival fibroblasts in vitro

Combinations of rosin and zinc are used in dentistry as components of periodontal dressings and cements and as root canal sealers. The composition and properties of rosins differ largely depending on source and refinement processes. Rosin (colophony) is composed of approximately 70% resin acids. In order to study the toxic effects of different natural rosins and purified resin acids and the detoxifying effects of zinc, these compounds were analyzed and tested on human polymorphonuclear leukocytes (PMN cells) and human gingival fibroblasts using the radiochromium release method. The rosins and the pure resin acids showed a strong dose-related cytotoxicity, which was inhibited by increased zinc concentrations. The purified resin acids (isopimaric, levopimaric, and neoabietic acid) were more toxic than the natural rosins. The contents of these resin acids might explain the difference in toxicity of the rosins tested. It is concluded that rosin and zinc are not to be considered inert compounds and that the cytoprotective effects of zinc and its role in dentistry products merit further investigations.

Influence of infection at the time of root filling on the outcome of endodontic treatment of teeth with apical periodontitis

This study investigated the role of infection on the prognosis of endodontic therapy by following-up teeth that had had their canals cleaned and obturated during a single appointment. The root canals of 55 single-rooted teeth with apical periodontitis were thoroughly instrumented and irrigated with sodium hypochlorite solution. Using advanced anaerobic bacteriological techniques, post-instrumentation samples were taken and the teeth were then root-filled during the same appointment. All teeth were initially infected; after instrumentation low numbers of bacteria were detected in 22 of 55 root canals. Periapical healing was followed-up for 5 years. Complete periapical healing occurred in 94% of cases that yielded a negative culture. Where the samples were positive prior to root filling, the success rate of treatment was just 68%--a statistically significant difference. Further investigation of three failures revealed the presence of Actinomyces species in each case; no other specific bacteria were implicated in failure cases. These findings emphasize the importance of completely eliminating bacteria from the root canal system before obturation. This objective cannot be reliably achieved in a one-visit treatment because it is not possible to eradicate all infection from the root canal without the support of an inter-appointment antimicrobial dressing.