Clinical and laboratory diagnostic characteristics and cytotoxigenic potential of Hafnia alvei and Hafnia paralvei strains.

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 ß-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 µg/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.

Chemical inactivation of Toxoplasma gondii oocysts in water.

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.

Description of Babesia duncani n.sp. (Apicomplexa: Babesiidae) from humans and its differentiation from other piroplasms.

The morphologic, ultrastructural and genotypic characteristics of Babesia duncani n.sp. are described based on the characterization of two isolates (WA1, CA5) obtained from infected human patients in Washington and California. The intraerythrocytic stages of the parasite are morphologically indistinguishable from Babesia microti, which is the most commonly identified cause of human babesiosis in the USA. Intraerythrocytic trophozoites of B. duncani n.sp. are round to oval, with some piriform, ring and ameboid forms. Division occurs by intraerythrocytic schizogony, which results in the formation of merozoites in tetrads (syn. Maltese cross or quadruplet forms). The ultrastructural features of trophozoites and merozoites are similar to those described for B. microti and Theileria spp. However, intralymphocytic schizont stages characteristic of Theileria spp. have not been observed in infected humans. In phylogenetic analyses based on sequence data for the complete18S ribosomal RNA gene, B. duncani n.sp. lies in a distinct clade that includes isolates from humans, dogs and wildlife in the western United States but separate from Babesia sensu stricto, Theileria spp. and B. microti. ITS2 sequence analysis of the B. duncani n.sp. isolates (WA1, CA5) show that they are phylogenetically indistinguishable from each other and from two other human B. duncani-type parasites (CA6, WA2 clone1) but distinct from other Babesia and Theileria species sequenced. This analysis provides robust molecular support that the B. duncani n.sp. isolates are monophyletic and the same species. The morphologic characteristics together with the phylogenetic analysis of two genetic loci support the assertion that B. duncani n.sp. is a distinct species from other known Babesia spp. for which morphologic and sequence information are available.

Babesia conradae, sp. Nov., a small canine Babesia identified in California.

Small piroplasms as a cause of canine babesiosis have usually been identified as Babesia gibsoni. Recent genetic studies suggested that small piroplasms are more likely comprised of at least three genotypically distinct species. In southern California, canine babesiosis caused by a small piroplasm has been documented since 1990. Morphological characteristics of this parasite include a small (0.3-3.0 microm) intraerythrocytic merozoite stage with predominantly ring, piriform, tetrad, amoeboid, or anaplasmoid forms. Transmission electron microscopic images of merozoites demonstrate the presence of an apical complex consisting of an inner subplasmalemmal membrane and rhoptries. Based on phylogenetic analyses of the 18S rRNA and the ITS-2 genes, the Californian small piroplasm isolate is more closely related to piroplasm isolates from wildlife and humans in the western United States than it is to B. gibsoni. Molecular and morphologic evidence supports naming the small piroplasm from southern California as a distinct species, Babesia conradae.

Physical inactivation of Toxoplasma gondii oocysts in water.

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