Misao Tsubokura

Geographical heterogeneity between Far Eastern and Western countries in prevalence of the virulence plasmid, the superantigen Yersinia pseudotuberculosis-derived mitogen, and the high-pathogenicity island among Yersinia pseudotuberculosis strains.

ABSTRACT Yersinia pseudotuberculosis produces novel superantigenic toxins designated YPMa (Y. pseudotuberculosis-derived mitogen), YPMb, and YPMc and has a pathogenicity island termed HPI (high-pathogenicity island) and R-HPI (the right-hand part of the HPI with truncation in its left-hand part) on the chromosome. Analysis of the distribution of these virulence factors allowed for differentiation of species Y. pseudotuberculosis into six subgroups, thus reflecting the geographical spread of two main clones: the YPMa+HPI− Far Eastern systemic pathogenic type belonging to serotypes O1b, -2a, -2b, -2c, -3, -4a, -4b, -5a, -5b, -6, -10, and UT (untypeable) and the YPMs− HPI+European gastroenteric pathogenic type belonging to serotypes O1a and -1b. The YPMa+ HPI+ pathogenic type belonging to serotypes O1b, -3, -5a, -5b, and UT and the YPMb+HPI− nonpathogenic type belonging to non-melibiose-fermenting serotypes O1b, -5a, -5b, -6, -7, -9, -10, -11, and -12 were prevalent in the Far East. The YPMc+R-HPI+ European low-pathogenicity type belonging to non-melibiose-fermenting serotype O3 and the YPMs−HPI− pathogenic type belonging to 15 serotypes were found to be prevalent all over the world. This new information is useful for a better understanding of the evolution and spread of Y. pseudotuberculosis.

Studies on avian infectious bronchitis virus (IBV)

SummaryThe induction of interferon by avian infectious bronchitis virus (IBV) and the sensitivity of IBV to interferon were studied. The results of experiments with ten IBV strains are summarized as follows. 1. All the IBV strains tested induced interferon in chick embryo (CE) cells, chicken kidney (CK) cells and embryonated eggs. The Iowa-609 strain induced about 1000 units of interferon in CE cells while the Beaudette-42 strain induced about 200 units of interferon in embryonated eggs; the interferon titers induced by other strains usually ranged from 5 to 60 units. No IBV strain induced interferon in HeLa or BHK-21 cells. 2. IBV particles inactivated by ultraviolet irradiation or by heating lost their ability to induce interferon. 3. The properties of the interferon produced in the present study are similar to those of other interferons produced in chicken cells. 4. HeLa or BHK-21 cells did not acquire resistance to virus infection, after incubation with interferon produced in CE cells. On the other hand, CK cells acquired the same degree of resistance to virus infection as CE cells after incubation with interferon produced in CE cells. 5. All the IBV strains tested were sensitive to interferon in CK cells. The sensitivities of Massachusetts-41 and Holte strains to interferon were similar to that of vesicular stomatitis virus.

Community outbreak of Yersinia pseudotuberculosis.

An outbreak of Yersinia pseudotuberculosis in Kurashiki, Japan is described. This is the first conclusive report of a community outbreak of this microorganism. A total of 535 pupils, five teachers, and one food attendant contracted the organism. Causative organisms were detected in 19 out of 30 patients. All isolated strains belonged to serotype VA. Out of 653 sera of the pupils, 488 showed elevated agglutinin titers ranging from 1: 80 to 1: 1,280 or more within a period of 3 months.

Growth Temperature-dependent Variation in the Bacteriophage-inactivating Capacity and Antigenicity of Yersinia enterocolitica Lipopolysaccharide

Growth temperature affected the structure of Yersinia enterocolitica Ye 3827 lipopolysaccharide (LPS). Although Y. enterocolitica Ye 3827 synthesized smooth LPS when grown at a low temperature (25 degrees C), partial smooth-rough transition occurred when the bacteria were grown at the physiological temperature (37 degrees C). The structural alteration was detected by bacteriophage-inactivation assay and chemical and immunological analyses. LPS prepared from bacteria grown at 25 degrees C inactivated a number of bacteriophages that recognize the O-antigenic polysaccharide portion of LPS, whereas more than 3000 times the amount of LPS from bacteria grown at 37 degrees C was required for the same degree of inactivation. The antigenic determinant(s) responsible for the major reaction between 25 degrees C-LPS and anti-25 degree C-bacteria was located on the O-antigenic polysaccharide portion of LPS, but those responsible for the major reaction between 37 degrees C-LPS and anti-37 degrees C-bacteria were located on the R-core or inner portion of LPS.

DRUG RESISTANCE AND CONJUGATIVE R PLASMIDS IN ESCHERICHIA COLI STRAINS ISOLATED FROM MIGRATORY WATERFOWL

We evaluated drug resistance and R plasmids of 554 strains of Escherichia coli isolated from feces of migratory waterfowl, including whistling swans (Cygnus columbianus), pintails (Anas acuta) and black-tailed gulls (Larus crassirostris) collected from the San-in District, Japan, between each November and March, 1983 to 1984, 1984 to 1985, and 1985 to 1986. Seven antimicrobial agents were tested: dihydrostreptomycin (DSM), kanamycin, spectinomycin, ampicillin (ABPC), oxytetracycline (OTC), chloramphenicol, and sulfadimethoxine (SDMX). Many strains were resistant to several drugs; in particular, all strains were resistant to SDMX. Both multiple drug resistant strains and drug resistance patterns occurred most frequently in strains isolated from whistling swans, followed by black-tailed gulls, and pintails, respectively. Of 233 strains, 128 (55%) carried transmissible R plasmids. The drugs with the largest number of resistance patterns observed were, in descending order, OTC, DSM, ABPC, and SDXM.

Ecological studies of Yersinia enterocolitica. II. Experimental infection with Y. enterocolitica in pigs.

Fattening pigs were inoculated with the human pathogenic strains of Yersinia enterocolitica, biovar 4 serovar 3 phagovar 8 and biovar 2 serovar 5.27. Each pig received 2.6 X 10(9) organisms by catheter into the stomach and thereafter 10% sodium bicarbonate solution, by the same route. The serovar 3 strain became established in the intestines of four out of six 11-week-old pigs and in all three 24-week-old pigs. Serovar 5.27 established in the intestines of all four 10-week-old pigs. In these pigs, both serovars were excreted in the feces at 10(2)-10(6) cells g-1 for a few weeks. However, the serovar 5.27 was excreted in the feces at less than 10(3.3) cells g-1 for 2 weeks by 24-week-old pigs. Horizontal transmission with the serovar 5.27 strain was observed on the 5th-11th day, and the bacteria were present in the intestines during the 2nd week. However, the serum titers to O-agglutinin were 1/10 and less, but in one pig, the titer was 1/40 against serovar 5.27 strain.

Pathogenicity for chickens of avian influenza viruses isolated from whistling swans and a black-tailed gull in Japan.

We isolated 24 Hav1 Neq1 and 18 Hav6 Nav3 influenza viruses from such free-living wild waterfowl as whistling swans, black-tailed gulls, and tufted ducks in western Japan in 1980. Two Hav1 Neq1 viruses isolated from a whistling swan and a black-tailed gull and a Hav6 Nav3 virus from a whistling swan were examined for their pathogenicity for chickens. Five-week-old specific-pathogen-free chickens were inoculated with the viruses intratracheally or intraperitoneally. Virus was recovered successfully from all the organs, including the brain, despite the absence of signs of disease. The intracerebral pathogenicity index scores obtained for the Hav1 Neq1 viruses were 0.43 and 0.87; the score for the Hav6 Nav3 virus was 0.43. No virus produced plaques in cultivated chick embryo fibroblast cells in the absence of trypsin.

Addition of new serogroups and improvement of the antigenic designs ofYersinia pseudotuberculosis

Eight strains ofYersinia pseudotuberculosis, untypable for any established serogroups, were studied. They were isolated from humans (three), dogs (two), cat (one), and rats (two), and the general characteristics of the strains were identical with those ofY. pseudotuberculosis. On the basis of results of O-agglutinin absorption tests, these strains were classified into three new serogroups. The new serogroups proposed were serogroups IIC, VII, and VIII, and a new O-antigenic scheme ofY. pseudotuberculosis was designed.

Biochemical heterogeneity of serotype 03 strains of 700Yersinia strains isolated from humans, other mammals, flies, animal feed, and river water

A total of 700 serotype 03 strains of yersiniae were recovered from patients, households withYersinia enterocolitica-infected persons, healthy humans, pigs, dogs, flies, feed, and river water, from 1977 to 1983. Of these isolates, 695 belonged toYersinia enterocolitica, three toYersinia intermedia, and two toYersinia frederiksenii. The 695Y. enterocolitica strains were classified into 484 biotype 4 serotype 03 phage type VIII, 17 biotype 4A (ornithine decarboxylase-negative) serotype 03 phage type VIII, 15 biotype 4B (maltosenegative) serotype 03 phage type VIII, and 179 biotype 3B (VP-, sorbose-, and inositolnegative) serotype 03 phage type II. These four biochemical heterogeneous types, including three new types, ofY. enterocolitica probably have long existed in Japan. There was a close relation between human infection withY. enterocolitica and the harboring ofY. enterocolitica in pigs and dogs.

Analysis of the superantigen-producing ability of Yersinia pseudotuberculosis strains of various serotypes isolated from patients with systemic or gastroenteric infections, wildlife animals and natural environments.

Yersinia pseudotuberculosis is a pathogen causing gastroenteritis as well as acute and systemic infections. This organism produces a superantigenic exotoxin, designated Y. pseudotuberculosis-derived mitogen (YPM). We consider this exotoxin to be the primary pathogen of the systemic type infection. In this study, we examined 101 Y. pseudotuberculosis strains isolated from various sources, patients with the systemic or the gastroenteric type of infections, wildlife animals and natural environments for the presence of the YPM gene and the production of YPM or other related superantigens. We found that all of the strains isolated from patients with systemic type infection carried the YPM gene and produced YPM. A certain proportion of the organisms isolated from patients with the gastroenteric type infection, wildlife animals or natural environments did not carry the YPM gene nor produced superantigens. These results suggest that YPM is involved in the pathogenesis of the systemic type of Y. pseudotuberculosis infection.