Inactivation of chemical and heat-resistant spores of Bacillus and Geobacillus by nitrogen cold atmospheric plasma evokes distinct changes in morphology and integrity of spores.

Bacterial spores are resistant to severe conditions and form a challenge to eradicate from food or food packaging material. Cold atmospheric plasma (CAP) treatment is receiving more attention as potential sterilization method at relatively mild conditions but the exact mechanism of inactivation is still not fully understood. In this study, the biocidal effect by nitrogen CAP was determined for chemical (hypochlorite and hydrogen peroxide), physical (UV) and heat-resistant spores. The three different sporeformers used are Bacillus cereus a food-borne pathogen, and Bacillus atrophaeus and Geobacillus stearothermophilus that are used as biological indicators for validation of chemical sterilization and thermal processes, respectively. The different spores showed variation in their degree of inactivation by applied heat, hypochlorite, hydrogen peroxide, and UV treatments, whereas similar inactivation results were obtained with the different spores treated with nitrogen CAP. G. stearothermophilus spores displayed high resistance to heat, hypochlorite, hydrogen peroxide, while for UV treatment B. atrophaeus spores are most tolerant. Scanning electron microscopy analysis revealed distinct morphological changes for nitrogen CAP-treated B. cereus spores including etching effects and the appearance of rough spore surfaces, whereas morphology of spores treated with heat or disinfectants showed no such changes. Moreover, microscopy analysis revealed CAP-exposed B. cereus spores to turn phase grey conceivably because of water influx indicating damage of the spores, a phenomenon that was not observed for non-treated spores. In addition, data are supplied that exclude UV radiation as determinant of antimicrobial activity of nitrogen CAP. Overall, this study shows that nitrogen CAP treatment has a biocidal effect on selected Bacillus and Geobacillus spores associated with alterations in spore surface morphology and loss of spore integrity.

[Observation on the therapeutic effect of Lamivudin on chronic hepatitis B].

OBJECTIVE: To observe the therapeutic effect of Lamivudine on controlling hepatitis B virus DNA replication. METHODS: The liver disease patients were divided into two groups, the treated group (n=64) was given Lamivudine 100 mg once a day for one year and was additionally given liver protection drugs according to their liver function, while the control group (n=30) was given common liver protection drugs. The blood routine test, liver function and the viral markers were detected at defined times. RESULTS: The results showed that after one year treatment of chronic hepatitis B with Lamivudine, the recovery rate of ALT was 90.7%, the negative conversion rate of HBV DNA was 73.1% showing a significant difference as compared with the control group (P<0.05). The negative seroconversion rate of HBeAg was 50%, HBeAg/anti HBe changing rate was 38.2%, that had no significant different as compared with the control group (P<0.05). The percentage for disease relapse and second elevation of ALT was 3.1% in therapeutic group that was significantly different from that of the control group (P<0.05). Two cases with severe hepatitis in the treated group were all alive. CONCLUSIONS: Lamivudine could effectively control HBV DNA replication, making ALT normal, it also could decrease the relapse rate of chronic hepatitis B and raise the survival rate of the patients with liver disease.