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The protozoan parasite Toxoplasma gondii is increasingly recognized as a waterborne pathogen. Infection can be acquired by drinking contaminated water and conventional water treatments may not effectively inactivate tough, environmentally resistant oocysts. The present study was performed to assess the efficacy of 2 commonly used chemicals, sodium hypochlorite and ozone, to inactivate T. gondii oocysts in water. Oocysts were exposed to 100 mg/L of chlorine for 30 min, or for 2, 4, 8, 16, and 24 hr, or to 6 mg/L of ozone for 1, 2, 4, 8, or 12 min. Oocyst viability was determined by mouse bioassay. Serology, immunohistochemistry, and in vitro parasite isolation were used to evaluate mice for infection. Initially, mouse bioassay experiments were conducted to compare the analytical sensitivity of these 3 detection methods prior to completing the chemical inactivation experiments. Toxoplasma gondii infection was confirmed by at least 1 of the 3 detection methods in mice inoculated with all doses (10(5)-10(0)) of oocysts. Results of the chemical exposure experiments indicate that neither sodium hypochlorite nor ozone effectively inactivate T. gondii oocysts, even when used at high concentrations.

Inactivation of Toxoplasma gondii oocysts occurred with exposure to pulsed and continuous UV radiation, as evidenced by mouse bioassay. Even at doses of ≥500 mJ/cm2, some oocysts retained their viability.

A collection of 68 Hafnia strains previously identified to the species level by 16S rRNA gene sequencing were investigated for simple phenotypic properties that could aid in their recognition in the clinical laboratory. Four tests, including malonate utilization, fermentation of salicin and D-arabinose, and expression of ␤-glucosidase activity, correctly assigned each strain to either Hafnia alvei or H. paralvei. Antibiotic susceptibility profiles were generated for 35 H. alvei and H. paralvei isolates using Etest strips for 24 antibiotics. All strains were susceptible to aminoglycosides, quinolones, carbapenems, and monobactams. Most of the Hafnia isolates had a colistin MIC of >2 g/ml. Sequencing of an internal ampC gene fragment allowed genotypic differentiation of the two Hafnia species. Approximately 70% of the hafniae tested additionally produced a cytolytic toxin active on Vero cells which may play a role in gastroenteritis.