A simple and useful method for the detection of C. kutscheri from the oral cavity of living rats was devised. In 10 sacrificed rats from two naturally and subclinically infected conventional colonies, 10(4.28) or 10(3.84) CFU/ml C. kutscheri were isolated from upper incisor swab extractions, while 10(1.38) or 10(1.58) and < 10 or 10(1.56) CFU/ml from the upper soft palate and pharynx, respectively. In another survey with 26 living animals, which were reared on the same rack, organisms were detected from the upper incisor and gingival swabs in 15 of 26 rats (57.7%). The results were reproducible at a second survey 10 days later. No organisms were isolated from any sites of the orally negative rats. These results indicated that culture of swab specimens from the upper incisors and gingivae of incisors is useful for the detection of C. kutscheri infection in living rats.

Sex difference in susceptibility to oral infection with Corynebacterium (C.) kutscheri was experimentally studied in ICR mice. Immature (4-week-old) and adult (14-week-old) mice were inoculated with two infecting doses of C. kutscheri, and necropsied for bacteriological and serological survey 4 weeks after the bacterial infection. No macroscopic lesions at necropsy were demonstrated, except for one adult male given 10(9) bacteria. In immature mice, C. Kutscheri isolated from the oral cavity and cecum with FNC agar, were recovered in only 40.0% of female mice but in 90.0% of male mice given 10(6) bacteria (p < 0.05), and in only 55.6% of female mice but in 80.0% male mice given 10(8) bacteria. In adult mice given 10(9) bacteria, the organism were recovered in only 45.5% of female mice but in 90.9% of male mice (p < 0.05), furthermore, the mean number of organisms in the cecum of male mice harboring the organism was significantly higher than that in females (p < 0.01). Castration caused an increase in host resistance in adult male mice. These results indicated that ICR male mice were more susceptible than females, in terms of bacterial colonization in the cecum and the oral cavity, to oral infection with C. kutscheri.

SummaryMice were infected experimentally and subclinically with Corynebacterium kutscheri to recover the organism from mice faeces. The faeces were then cultured using selective furazolidone-nalidixic acid-colimycin agar. The number of C. kutscheri per gram of fresh faeces varied from mouse to mouse, but once established in the intestine, the organism was excreted in the faeces for at least five months. Viable bacteria were detected in most of the faecal samples, including those stored in the animal room for five days. The number of organisms in the stored faeces decreased gradually but did not differ significantly from those in the fresh faeces until they had been stored for more than three days. Many infected mice excreted between 10 4.77 and 10 5.37 colony forming units (CFU) of C. kutscheri per day in their faeces, and one mouse even excreted 10 3.74 CFU at eight weeks postinfection. These values showed little daily variation. Our present study showed that subclinically infected mice discharged the organism continuously and persistently in their faeces. Therefore, faecal samples would be useful for monitoring infection with C. kutscheri in living mice in a manner that is not stressful for the animals.

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Abstract:The present study investigated whether pre-stimulation with intraperitoneal (i.p.) needling protects against development of diabetes in alloxan-treated transgenic (Tg) mice overexpressing the human Cu/Zn superoxide dismutase gene or non-Tg littermates of the FVB/N strain. Twenty minutes before the alloxan treatment (60 mg/kg) the mice were injected intraperitoneally with 0.05 ml saline while control mice received only the alloxan treatment. Hyperglycemic responses of the saline-injected mice to alloxan were significantly suppressed in the Tg mice (P<0.05). A similar reduction of response was also observed in non-Tg littermates, but the effect was less than that in the Tg mice. This protective effect on the diabetogenic action of alloxan was also demonstrated by an analysis of the number of days positive for urinary glucose, and by immunohistochemical analysis of pancreatic insulinpositive cells. A similar suppressive effect on the hyperglycemic response of alloxan was observed in the mice stimulated by i.p. needling alone. However, suppression of the hyperglycemic response was not observed in ICR mice receiving an i.p. injection. These results suggest that the diabetogenic action of alloxan can be suppressed by i.p. needlingmediated stimulation in mice that have a genetic background of the FVB/N strain. Since a slight protective effects of alloxan-induced diabetes was also observed in the Tg mice compared to FVB/N mice treated with only alloxan, this phenomenon could be more clearly seen in the Tg mice than in non-Tg littermates with an FVB/N background.