Plasmids and outer membrane proteins of Yersinia enterocolitica and related species of swine origin.

Yersinia enterocolitica and other pathogenic yersiniae harbor a plasmid termed pYV which is required for the full expression of virulence. The pYV codes for the release of a set of proteins called Yops and two outer membrane proteins Yad A and Ylp A. In the present study, 80 strains of Y. enterocolitica and related species were examined for the possession of the pYV and the ability to express Yops and Yad A. Only Y. enterocolitica belonging to serogroups O:1,2,3, O:3, O:5,27, O:8, and O:9 harbored the virulence plasmid and were positive for the presence of the ancillary proteins. The restriction fragment patterns of the pathogenic bioserotypes belonging to the same serogroup affiliation were similar irrespective of whether they were of swine origin, reference strains, or human clinical isolates. The same was also true of the electrophoretic patterns of the Yops. Our findings are in agreement with previous studies and support the view that pigs may be an important reservoir of pathogenic Y. enterocolitica.

Isolation of Yersinia enterocolitica (0:5,27 biotype 2) from a common garter snake.

Yersinia enterocolitica serotype 0:5,27 biotype 2 was isolated from the intestinal contents of a common garter snake (Thamnophis sirtalis). The isolate possessed virulence associated phenotypes in all tests conducted. It was susceptible to amikacin, ampicillin/sulbactam, aztreonam, cefoperazone, cefotaxime, ceftazidime, ceftriaxone, cefuroxime, ciprofloxacin, gentamicin, imipenem, mezlocillin, norfloxacin, piperacillin, ticarcillin/clavulanic acid, trimethoprim-sulfamethoxazole, tobramycin, chloramphenicol and tetracycline. The isolate harbored the virulence plasmid.

Detection of pathogenic Yersinia enterocolitica by polymerase chain reaction and digoxigenin-labeled polynucleotide probes.

Yersinia enterocolitica is widespread in nature, but only a few bioserotypes are involved in human infections. Pigs are considered to be the major reservoirs of pathogenic strains. It is essential to have an accurate and rapid method for the detection of pathogenic yersiniae. To achieve this objective, 19-base synthetic oligonucleotide primers were used in a polymerase chain reaction (PCR) to detect the ail gene (which is conserved only in pathogenic strains) in strains of Y. enterocolitica and related species originating from pigs or pork products. Digoxigenin-labeled probes derived from the ail, inv, and yst genes were also evaluated on these strains. The PCR amplified a 273-bp fragment of the ail gene involved in eukaryotic cell invasion and serum resistance. The PCR detected template DNA only in strains of Y. enterocolitica traditionally classified as human pathogens but not in biotype 1A strains and related species. Other members of the family Enterobacteriaceae were also negative for the target gene. The digoxigenin-labeled ail probe gave identical results to the PCR. By use of this nonisotopic method, inv-homologous DNA was detected only among yersiniae, except for Y. ruckeri. Although all pathogenic serotypes of Y. enterocolitica were positive for the heat-stable enterotoxin yst gene, two strains of biotype 1A, one Y. intermedia strain, and six other species of the Enterobacteriaceae were also positive. Our results support the notion that pigs constitute an important reservoir of pathogenic Y. enterocolitica and that the inv-homologous sequence is Yersinia specific.

Laboratory investigation of virulence among strains of Yersinia enterocolitica and related species isolated from pigs and pork products.

Eighty strains of Yersinia enterocolitica and related species isolated from slaughtered pigs and pork products were tested for possession of virulence-associated phenotypes by employing 12 in vivo and in vitro assays. The isolates could be broadly divided into two groups: (i) strains belonging to pathogenic bioserotypes of Y. enterocolitica that displayed virulence-associated characteristics in most or all assays and (ii) strains belonging to Y. enterocolitica biotype 1A and to related species that were largely negative in these assays. No individual test was found as a single reliable measure of virulence. All strains belonging to Y. enterocolitica serotype O:1,2,3 were pyrazinamidase positive (indicates avirulence) and autoagglutination negative but were positive in all other virulence assays. Salt aggregation was found to be a better indicator of virulence than latex particle agglutination, both of which measure surface hydrophobicity. Overall, tissue culture cell invasion provided the best selection of a subpopulation of yersiniae that are potentially virulent. However, crystal violet and Congo red binding assays among others provided good prediction of virulence at the time of testing. Our results provide further evidence that swine may constitute an important reservoir of human pathogenic strains.

In vitro antimicrobial susceptibilities of Yersinia enterocolitica and related species isolated from slaughtered pigs and pork products.

The MICs for and disk susceptibilities of 80 strains of yersiniae isolated from swine and pork products were determined. The most effective antimicrobial agents in the in vitro tests were the aminoglycosides, cephalosporins (cefotaxime, ceftazidime, and ceftriaxone), imipenem, ticarcillin-clavulanic acid, aztreonam, ciprofloxacin, norfloxacin, and trimethoprim-sulfamethoxazole. There was a high percentage of resistance among the strains to penicillinase-sensitive penicillins, erythromycin, clindamycin, vancomycin, cefazolin, and cephalothin.

Prevalence of antibodies to Toxoplasma gondii in striped skunks from Saskatchewan and Alberta.

Fifteen percent (81 of 542) of striped skunks, Mephitis mephitis, collected in the prairie of Alberta and Saskatchewan during 1974 to 1978, were positive for antibodies against Toxoplasma gondii. The seropositive rates varied from 8% (6 of 78) for skunks less than six months of age to 47% (9 of 19) in animals three or more years old. Spring and summer transmission was indicated by a preponderance of high titres (greater than or equal to 1:1024) in seropositive skunks collected April through September (22 of 40, 55%) compared to seropositives collected October through MFarch (10 of 38, 26%) (P = < 0.05). Prevalence was significantly greater among skunks collected in the relatively humid parkland (63 of 286, 22%) than in the arid prairie grassland biome (20 of 225, 8%) (P = < 0.01). The results indicate that T. gondii is focally enzootic in Alberta and Saskatchewan.

Cache Valley virus: isolations from mosquitoes in Saskatchewan, 1972-1974.

Eighteen isolations of Cache Valley virus (Bunyaviridae) were obtained from a total of 113,694 mosquitoes collected in Saskatchewan during the summers of 1972 to 1974. Most of the isolations were from mosquitoes collected during August. Culiseta inornata, the most abundant mosquito (38% of total collected), had the highest minimum vector-infection rate (0.83 isolations per 1000 mosquitoes). The virus was also isolated from Culex tarsalis and Aedes vexans. It is indicated in the isolations that the prairie grasslands of the province are enzootic for Cache Valley virus.

A serological survey of Leptospira interrogans serotype pomona in Saskatchewan horses.

Leptospira interrogans serotype pomona antibody titres of 1:100 or greater were detected in 12.8% of 408 adult horses from seven of eight sampled herds in Saskatchewan. The geographical distribution of the seropositive horses was widespread throughout the agricultural area of the province. The geographical distribution and the cumulative increase in prevalence with age suggested that serotype pomona is enzootic in the equine population of Saskatchewan.

Experimental chlamydiosis in wild and domestic lagomorphs.

Chlamydia psittaci (strain M56, the agent of epizootic chlamydiosis of muskrats and hares) was highly lethal for the snowshoe hare (Lepus americans) following intravenous inoculation, whereas the agent was much less virulent for cottontail (Sylvilagus floridanus) and albino domestic rabbits (Oryctolagus cuniculus). Tissue titres of strain M56 were generally higher after 96 hr in the snowshoe hare than in tissues of the other lagomorphs. Spleen, liver and bone marrow were apparently the chief sites of primary multiplication of strain M56 in the hare. Virulence appeared to be very host specific in that only strain M56 among the six chlamydiae tested was highly lethal for the snowshoe hare.

Ocular involvement with Chlamydia psittaci (strain M56) in rabbits inoculated intravenously.

Fourteen albino rabbits were inoculated intravenously with 10(3.5)-10(4.0) mouse ICLD(50) of Chlamydia psittaci (strain M56) of mammalian origin. Ocular lesions accompanied the chlamydial infection in the rabbits. Bilateral anterior uveitis, a common occurrence, began on the second or third day and subsided by the tenth day whereas keratoconjunctivitis was observed infrequently. After 15 days the most prominent microscopic lesion was iritis. Accumulations of inflammatory cells, mainly plasma cells, were observed in the iris and ciliary body and elementary bodies were found infrequently in macrophages. Chlamydiae were recovered consistently by conjunctival swabbing from the fifth to the twenty-fourth day. The agent was present within the eye (viz. iris-ciliary body) in three of four rabbits killed at 15 days and in five of ten rabbits killed 60 days after inoculation. Chlamydiae had persisted in the cerebrum and joints as well. Although neutralizing antibody was consistently present in sera at 60 days none of the samples of aqueous humor were capable of neutralizing the agent. It is suggested that systemic chlamydial infections in the rabbit provide a model for the study of endogenous uveitis, a common ophthalmological problem.

Selected microbial agents in snowshoe hares and other vertebrates of Alberta.

Serologic surveillance of populations of snowshoe hares and other vertebrate species of north-central Alberta from 1961 to 1969, revealed activity of one bacterial and eight viral agents. The most prevalent agents infecting the snowshoe hare were California encephalitis and Silverwater viruses, while in other vertebrates California encephalitis and Western equine encephalomyelitis viruses were the most common. The role of the snowshoe hare in the natural history of the agents is considered as is the effect of the agent on the hare ten-year cycle of abundance.