Serological surveys of Corynebacterium kutscheri infection in mice and rats

Serological surveys of mice and rats naturally infected with Corynebacterium kutscheri were performed by examining serum samples collected from breeder and laboratory colonies between 1981 and 1983. Among 756 mice from 73 conventional colonies, only 4 animals (0.5%) from 3 colonies (4.1%) developed C. kutscheri antibody of 1:40 to 1:2, 560 titers. Three of them suffered from abscess caused by the organism. Regarding a titer of 1:40 or higher as reliably positive, 87 (13.0%) of 669 conventional rats or 20 (32.8%) of 61 colonies were found to be infected with the organism. The antibodies were detected in both types of animals older than 6 months of age. No lesions caused by C. kutscheri were found in almost all the rats examined. Germ-free and SPF mice and rats were all negative for antibody at 1:5 serum dilution.     

Detection of Corynebacterium kutscheri from the oral cavity of rats.

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.     

Selective medium for Corynebacterium kutscheri and localization of the organism in mice and rats

A new selective medium for isolation of Corynebacterium kutscheri (CK) from animals suffering subclinical infection was made by adding furazolidone, nalidixic acid and corimycin to the heart infusion agar base, this being named FNC agar. The FNC agar inhibited the growth of gram-negative rods, Pseudomonas aeruginosa, Proteus sp. and gram-positive cocci but did not affect the growth of CK. When this medium was used to isolate CK from the oral cavity and cecal contents of mice and rats, two of 6 conventional mouse colonies and three of 8 conventional rat colonies were found to be infected, with isolation of the organism from 19 mice and 12 rats in total. The animals showed neither clinical signs nor lesions, but the antibody was positive in 11 mice and 10 rats. In mice and rats inoculated orally with 4 x 10(8) and 1 x 10(9) organisms, respectively, CK was isolated for 20 weeks post-inoculation by use FNC agar. The isolation rate of the organism was the highest in the oral cavities of both inoculated mice and rats, and also in the submaxillary lymph nodes of the inoculated rats. The organism was also recovered from the cecal contents of more than half of the inoculated mice and rats. Thus, it was considered that FNC agar was useful in isolating CK from the oral cavity and cecal contents of mice and rats with subclinical infection of the organism.     

Sex differences in susceptibility of ICR mice to oral infection with Corynebacterium kutscheri.

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.     

Experimental Corynebacterium kutscheri infection in rats: bacteriology and serology

In a preliminary study, hydrocortisone-treated rats developed pseudotuberculosis when challenged with 6.2 X 10(5) to 3.1 X 10(7) colony forming units of Corynebacterium kutscheri by intranasal, intragastric, or subcutaneous inoculation. Oronasal exposure was selected as a likely natural route to further study inapparent infection. In Study 1, 50 rats received 1.2 X 10(5) colony forming units and various tissues were cultured at intervals to 12 weeks post-inoculation. At each interval, C. kutscheri was regularly isolated from submaxillary lymph nodes, but isolation was sporadic from other sites. In Study 2, 17 out of 21 rats given 1.2 X 10(5) colony forming units and killed weekly for 6 weeks had 2.0 X 10(2) to 1.8 X 10(5) colony forming units of C. kutscheri in oral washes, and 16 rats had 2.0 X 10(2) to 1.0 X 10(5) colony forming units in submaxillary lymph nodes, Serum antibody to C. kutscheri using both microagglutination and indirect immunofluorescence was first detected in some rats by 2 weeks, and in all rats at subsequent intervals. There was a significant (P less than 0.001) positive correlation (r = 0.93) between serum antibody titers and the duration of infection.     

The effect of selected viruses on Corynebacterium kutscheri infection in rats

The influence of selected viral pathogens on rats that were previously infected with Corynebacterium kutscheri was investigated. A series of three separate experiments were performed to test the effect of sialodacryoadenitis virus, Sendai virus and rat virus. In each experiment, weanling rats were divided into three groups (C. kutscheri-inoculated, virus-inoculated and C. kutscheri plus virus-inoculated). Two groups were inoculated oronasally with C. kutscheri to establish subclinical infections. Two weeks later, two groups were inoculated intranasally with virus. At 5 weeks, the prevalence of C. kutscheri recovery from oral cavity and submaxillary lymph node and the prevalence of overt pseudotuberculosis was compared between treatment groups. Seroconversion of rats to C. kutscheri was measured by microagglutination and viruses by indirect immunofluorescence assays. Infection of rats with sialodacryoadenitis virus, Sendai virus or rat virus had no discernable effect on C. kutscheri-infected rats.     

Upregulation of galectin-3 by Corynebacterium kutscheri infection in the rat lung.

Corynebacterium (C) kutscheri and Staphylococcus aureus were isolated from two Sprague-Dawley (SD) rats with a hemisected spinal cord. Grossly, gray-white bulging foci and abscesses were distributed throughout the parenchyma of the lung. Pathologically, severe necrotizing lobar pneumonia with abscesses and fibrinous pleuritis were observed. Immunohistochemical analysis found accumulation of galectin-3 in alveolar macrophages and the alveolar interstitial region. No other viral or bacterial pathogens were detected in these animals. In addition, similar pathogenic changes and accumulation of galectin-3 were observed in the lungs of SD rats experimentally infected with C. kutscheri. Using northern blot analysis, the relative galectin-3 and GAPDH mRNA levels were 4.6 to 9.3 times higher in C. kutscheri-infected lung than in uninfected controls. These results demonstrate that a single C. kutscheri infection can induce the upregulation of galectin-3 in the lung and that this molecule may have an important pathogenic role in C. kutscheri infections in rats.     

Comparison of methods to diagnose an epizootic of Corynebacterium kutscheri pneumonia in rats

An outbreak of Corynebacterium kutscheri pneumonia occurred in a colony of laboratory rats. Diagnostic methods compared on a prospective basis included (1) an enzyme-linked immunosorbent assay (ELISA) for serum antibody to C. kutscheri; (2) C. kutscheri isolation from retrograde nasal wash, cervical lymph nodes, tracheal wash, lung homogenate; and (3) histopathology. C. kutscheri was isolated from one or more of the cultured sites from suspected cases, but no individual rat yielded C. kutscheri from all of the sites. The presence of histological lung lesions was the most frequent indicator of infection (8 of 9 suspected cases), followed by isolation of C. kutscheri from lung homogenate (5 of 6), ELISA for serum antibody (6 of 8), and isolation of C. kutscheri from cervical lymph node (4 of 8). Isolation of C. kutscheri from nasal wash (1 of 9) was the least sensitive indicator of infection. ELISA antibody was not detected in rats which had normal lungs and did not harbor C. kutscheri. It was concluded that ELISA provides noninvasive means for detecting infection and cervical lymph node culture increase the potential for successful isolation of the agent in C. kutscheri infected rats.     

Latent infection with Corynebacterium kutscheri in mice after peroral inoculation and its provocation by cortisone (author's transl)]

Latent infection with Corynebacterium kutscheri in mice and its provocation by cortisone were studied with a rifampicin-resistant strain of the organism. Mice having been infected perorally began to excrete the organisms in feces within 6 hours, and most of them were found to be carrying the organisms in the intestine, especially in the cecum even 90 days after infection. In such state of latency, however, no organisms were detected in other main organs, and neither visible lesions nor serum agglutinin was detectable. The latent infection with excretion of the organisms in feces after peroral infection was shown to become overt and fatal by cortisone treatment made even 90 days after infection. In infected mice excreting no organisms in feces and having bites on their skin, the wounds became severe ulcers after cortisone treatment resulting in septicemia.     

Massive microfilaremia in a dog subclinically infected with Acanthocheilonema dracunculoides

Canine filarioids are worldwide distributed nematodes transmitted by arthropods with variable virulence depending on the species. Dirofilaria immitis is the most virulent and serological antigen tests are commonly employed to detect it. This study reports on the heaviest cavity filariasis recorded so far in a dog, which showed no apparent clinical signs of infection. The 6-year-old male was positive to a D. immitis antigen test. Blood samples collected and analyzed with the modified Knott's test for microfilariae revealed 264,367 microfilariae/ml. In a post-mortem examination 791 adult filarial nematodes were found in the dog's thoracic and peritoneal cavities. Morphological and molecular analysis identified the nematode as Acanthocheilonema dracunculoides and no other species were present. This is evidence that massive A. dracunculoides infections in dogs may not be clinically evident, they may cause serologic cross-reaction with D. immitis infection and become a life-threatening condition if dogs are treated with a microfilaricidal treatment without previously performing an adequate diagnosis.     

Isolation of Corynebacterium kutscheri from aged Syrian hamsters (Mesocricetus auratus).

Corynebacterium kutscheri was isolated from the oral cavities of 12 male Syrian hamsters (Mesocricetus auratus) which were about 12 months old. At 1, 5, and 9 months after initial isolation of C. kutscheri from the oral cavity, hamsters were euthanatized, and attempts were made to culture C. kutscheri from 13 additional sites. Corynebacterium kutscheri was isolated from nine hamsters, and regardless of the hamsters' ages, the organisms were most frequently isolated from the oral cavity (100%), esophagus (100%), cecal content (100%), and colon and rectum (88.9%). Isolation rates in the nasal cavity were 66.7%, followed by 55.5% in the trachea and 33.3% in the submaxillary lymph nodes. The number of the organisms found in the submaxillary lymph nodes and esophagus was 10(3) to 10(4) CFU/g. The number found in the cecal content and in the colon and rectum was 10(2) to 10(5) CFU/g. The organisms were not isolated from lung, stomach, kidney, spleen, and mesenteric lymph node tissues. The hamsters had neither clinical signs nor lesions. However, 7 of 12 animals had low agglutinating antibody titers. The Syrian hamster can therefore be an asymptomatic carrier of C. kutscheri.