Yersinia enterocolitica among small wild mammals in France.

A survey of Yersinia enterocolitica was made in two French areas (Indre and Alsace) in several components of the terrestrial ecosystem. Y. enterocolitica has been isolated from several habitats and from numerous species of small mammals. The trap line method enabled us to estimate the density of the two abundant small mammal species, Microtus arvalis and Apodemus sylvaticus, and the densities of Y. enterocolitica carriers. The frequency of isolation was high when temperatures were low, but did not seem to be in direct relationship with animal densities. Infectious lesions were never found in spleens or intestines of 1893 captured animals. Samples of fresh water, fresh-water fish, soil and earthworms were occasionally collected. A total of 163 strains were isolated. Of these, 99 were of biochemical type 1; 20 different 0 serogroups were found.

Production of bacteriocin-like substances by Yersinia frederiksenii, Y. kristensenii, and Y. intermedia strains.

The production of bacteriocin-like substances by strains of Yersinia frederiksenii, Y. kristensenii and Y. intermedia in broth culture was established. These substances showed a selective activity against Y. enterocolitica, Y. frederiksenii, Y. kristensenii and Y. intermedia strains. Electron micrographs revealed the presence of phage tails in culture media. The production of these substances was detected in cultures grown at 25 degrees C but not in those grown at 37 degrees C, while these bacteriocin-like substances were active at 25 and 37 degrees C. Y. enterocolitica serogroups 0:3 and 0:9 were more susceptible to these bacterin-like substances than strains of Yersinia isolated from environmental sources.

Antagonism between Yersinia intermedia and Yersinia enterocolitica in water.

One strain of Yersinia enterocolitica and one strain of Y. intermedia were grown in peptone water at 25 or 37 degrees C, or in ground water at 15 degrees C. Similar growth rates were observed when these strains were cultivated separately in the same media and at the same temperature. Mixed cultures at 37 degrees C displayed equivalent growth rates. In contrast, mixed cultures incubated at 15 or 25 degrees C were regularly unfavourable to Y. enterocolitica, whereas they did not modify the growth of Y. intermedia. A bacteriophage active on Y. enterocolitica and not on Y. intermedia was characterized from the filtrate of mixed cultures at low temperatures. This phage produced by the lysogenic Y. intermedia strain might be a potential factor responsible for the inhibition of Y. enterocolitica, since no additional antibacterial factor or nutritional competition between Y. intermedia and Y. enterocolitica were found in the mixed cultures.

[New results on the phage typing of Yersinia enterocolitica, concerning more of 4 000 strains of various origins (author's transl)]. / Nouveaux résultats sur la lysotypie de Yersinia enterocolitica portant surplus de 4 000 souches d'origines diverses

1) The phage typing of Y. enterocolitica has been made on more than 4,000 strains of various origins by means of 2 sets of phages. The 1st one, composed of 12 phages extracted from lysogenic strains of the same species has permitted to distinguish 10 phages types numbered from I to VIII and from IXa to IXb among the 3,323 lysotypable strains on the 4,366 examinated. 2) The search of the beta-galactosidase has differentiated the phage type IXa in its 2 varieties, the IXa 1, beta-galactosidase negative and the IXa 2, beta-galactosidase positive. 3) The 1,043 untypable strains by the 1st set were forming 2 very different groups. One of them, the X was insensitive to the 12 phages of the 1st set; the other XI, showed such a variety of lytic reactions to the phages of the 1st set that it was impossible to consider the rare samples of each of them as phage types. 4) The group X, submitted to a "complementary phage typing" by means of a second set of phages isolated from sewage water, has been subdivised into about 20 undergroups, from which only, 7 have been studies up to now, numbered from X 1 to X 7...

[The discovery by Paul-Louis Simond of the role of the flea in the transmission of the plague]. / La découverte par Paul-Louis Simond du rôle de la puce dans la transmission de la peste.

After Yersin's two fundamental discoveries of the plague bacillus and of the rat's role in its propagation, no one had sought to solve the riddle of how the bacillus itself spread and how it contaminated man. P. L. Simond was the first to realise that manipulating a rat that had recently died could be extremely dangerous whereas after a time lapse of several hours the same dead rat presented no risks to man. He was also the first to detect an insect bite as being responsible for the lesions he had observed at the beginning of bubonic plague outbreaks and called "precocious plyctenas". After having verified the presence of the bacillus in fleas of dying rats, on 2 June 1898 Simond carried out his princeps experiment on the transmission of plague to rats by fleas. From then onwards, disinsectisation was added to deratisation in plague prophylaxis.

[Concealing and denying the plague]. / Dissimulation et négation de la peste.

Some examples are given of plague epidemics which have been negated or dissimulated in order to avoid isolation and quarantine: epidemics of Marseille (1720), San Francisco (1900), Mauretania (1963-1967), Libya and Egypt (1984).

[Tholozan and plague in Persia]. / Joseph Désiré Tholozan et la peste en Perse.

In Persia since 1858, Tholozan studied between 1870 and 1882 the plague foci of the iranian Kurdistan which shall be dealt a century later (1947-1963) with Dr. M. Baltazard and his co-workers from the Pasteur Institute of Teheran. Tholozan had already pointed out the localization of the disease in some well defined villages and gave a good clinical description mentioning the traces of flea bites on the patients skin. One knows nowadays that wild rodents (Meriones) are the storing places of the plague bacilli in the Kurdistan. Tholozan's observations confirmed by modern ones allow to consider him a great loïmologist of modern times.

[A personal view of the history of the genus Yersinia]. / A personal view of history of the genus Yersinia.

The first recorded experience Australia had of the genus Yersinia was the arrival in 1889 of a French expedition led by Pasteur's nephew, Dr. Adrien Loir. At that time Australia was in the grips of an epidemic of rabbits, and Loir's purpose was to eradicate the rabbits by means of fowl plague (Pasteurella multocida). Sadly, bureaucratic and political obstacles prevailed, and Loir was never granted permission to release his biological control agent. Alexander Yersin had been tempted to join Loir's expedition, but elected in the end to travel to Hong Kong, where he discovered the plague bacillus. Had he gone to Australia, we might not now be speaking of the genus Yersinia... Historically, Yersinia pestis has affected not only world history but literature as well. In Shakespeare's Romeo and Juliet, the tragic denouement can be attributed directly to the consequences of the Great Plague. In times of plague, cities closed their gates to travellers, and houses their doors and windows. Thus Laurence's explanatory letter was prevented from reaching Romeo, who returned to take his life beside the drugged (but living) body of his beloved. Not only was the contemporary literature from which Shakespeare drew inspiration full of references to the plague, but he himself had experienced the social effects of the plague at first hand. The recent rejection of the name Y. pseudotuberculosis var. pestis in favour of Y. pestis is fitting, not simply on the grounds of preventing confusion - after all, Y. pseudotuberculosis can be an equally lethal pathogen. However, a review of the epidemiology for Y. pestis since the First Pandemic in the 6th Century AD lends support to Devignat's hypothesis that Y. pseudotuberculosis evolved from Y. pestis, rather than vice versa. This probably occurred in Europe shortly before the Second Pandemic, and the new mutant spread slowly through the European rodent population, immunising the carriers against plague. In other parts of the world which continued to be affected by plague, the rodent populations remained susceptible because they had not been immunised by exposure to Y. pseudotuberculosis. In some areas which have not been affected by plague, it is also possible that the native rodent populations have been immunised by Y. enterocolitica and its relatives. The plague, the first biological weapon, has killed more people than man's wars. It is our duty, as bacteriologists handling this pathogen, to refuse to allow our work to be used in modern warfare, to refuse to participate in any further warfare against humanity itself.

[Yersinia pseudotuberculosis and Yersinia enterocolitica]. / Yersinia pseudotuberculosis et Yersinia enterocolitica.

Yersinia pseudotuberculosis is a very homogeneous species, with only six sero-groups and which can not also be lysotyped. The essential reservoir is made up of rodents, birds, cats and soil and is the origin of human infection. Y. enterocolitica has 5 biochemical types, 57 serotypes (types 03 and 09 are the most commonly involved in human pathology) and 11 lysotypes. Contamination is essentially by direct human-human contact from healthy carriers or, more rarely, via infected food. The aetiological diagnosis of the arthritis occurring after an episode of abdominal Yersinia (enteritis, mesenteric adenitis) depends on the simultaneous search for bacteria in the stools and for antibodies.

Cellular depletion in Peyer's patches after cyclophosphamide treatment in mice.

The cytotoxic effects of cyclophosphamide (CY) in mice given by the intravenous route at the dose of 200 mg per kg of body weight, were investigated in Peyer's patches comparatively with peripheral blood and mesenteric lymph node as well as changes in the spleen weight. Peyer's patches are the sites of a more intense and durable cellular depletion than the mesenteric lymph node, observed as soon as day 1. A partial restauration of cell populations was observed from the 9th day, but even at day 21 their number remained lower than in control mice. Histological studies failed to show any germinal centre throughout the experiment; just a few cells were observed, 2 days after CY injection, in the interfollicular areas in which cells in mitosis were only seen at day 7. This preliminary results allow to study the role of the Peyer's patches as first barrier against penetration of an enteropathogenic bacteria able to invade the host tissues through the intestinal wall components after local or general acquired immunodeficiency.

Comparison of restriction endonuclease analysis and phenotypic typing methods for differentiation of Yersinia enterocolitica isolates.

Restriction endonuclease analysis of chromosomal DNA (REAC) was used to study polymorphism in restriction fragment patterns among Yersinia enterocolitica isolates belonging to serogroups O3, O5,27, O8, O9, O13, and O21. Using the enzyme HaeIII and electrophoresis on thin (0.75-mm) vertical 5% polyacrylamide gels, we were able to distinguish at least 22 DNA fragment patterns among the 72 strains examined. The method showed the greatest discriminatory power with regard to serogroup O8, within which as many as 10 different DNA fragment patterns were detected among the 16 strains examined. Compared with O8, serogroups O3 and O9 were relatively homogeneous with regard to REAC patterns. The discriminatory power of the method was compared with H-antigen typing, biotyping, phage typing, antimicrobial susceptibility typing, and restriction enzyme analysis of the virulence plasmid (REAP), by means of Simpson's index of diversity. The results showed that REAC and REAP constitute an effective supplement or alternative to conventional phenotypic methods for tracing epidemiologically related isolates of Y. enterocolitica. Our finding that human and porcine isolates exhibited the same REAC, REAP, and H-antigen patterns provides additional support for the hypothesis that pigs play an important role in the epidemiology of human Y. enterocolitica infection.

Expression of iron-regulated proteins in Yersinia species and their relation to virulence.

Under iron-starvation conditions, the different Yersinia species expressed various iron-regulated proteins. Among them, two high-molecular-weight outer membrane proteins were synthesized in high-virulence-phenotype Y. pestis, Y. pseudotuberculosis, and Y. enterocolitica serovars O:8 and O:Tacoma but were present neither in low-virulence phenotype Y. enterocolitica serovars O:3 and O:9 nor in avirulent Y. frederiksenii, Y. kristensenii, Y. intermedia, and Y. enterocolitica serovar O:39. Thus, the degree of virulence correlates with the presence of the two high-molecular-weight proteins in Yersinia species.