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Thirteen Yersinia enterocolitica were recovered from a variety of clinical sources. Of these, only one was associated with mesenteric lymphadenitis and belonged to serotype 8. The 12 remaining strains were isolated from nonmesenteric sources and belonged to serotype 17. All strains exhibited the main characteristics of Y. enterocolitica which differentiated them from other Enterobacteriaceae , i.e., motility at 22 C but not at 37 C, positive urease and ornithine decarboxylase activities, and negative phenylalanine deaminase. These 12 strains differed, however, from other Y. enterocolitica previously described in the United States in that they fermented rhamnose and raffinose at 22 C, and failed to grow on Salmonella-Shigella and Hektoen-Enteric agars.

Ten strictly anaerobic bacterial strains belonging to the genera Inflabilis (I), Zymobacterium (Z), Acuformis (A), Streptococcus (S1, S2), Ristella (R), Clostridium (C), Eubacterium (E), Pasteurella (P), and Veillonella (V); three facultatively anaerobic strains belonging to the genera Actinobacillus (Ac), Lactobacillus (L), and Staphylococcus (St); and one yeast strain of the genus Torulopsis (T) were inoculated into adult male and female axenic mice fed either a commercial diet A or a semisynthetic diet B.Three strains (I, Z, St) did not establish in any "gnotoxenic" animals. One strain established only in animals fed diet B (S2). The average number of each of the other 10 strains is 10 to 100 times less in animals receiving diet B than in those given diet A. The microflora of the stomach and the small intestine is more variable and less abundant in mice fed diet B than in those receiving diet A. For strains A and C there is a net decrease in colon populations as related to those of the caecum or the feces, especially in mice receiving diet B.In the digestive tract of young "gnotoxenic" mice sacrificed before weaning, the facultatively anaerobic microflora is always established before the strictly anaerobic flora but does not change the establishment of the latter. Finally, the diet of the mother affects appreciably the establishment kinetics of strains L, St, and T in the young mice.

Antibody, transferrin and complement, acting together, directly interfere with the biochemistry of Pasteurella septica effecting an inhibition of RNA accumulation and the cessation of bacterial growth. This communication describes the fate of ribosomal RNA in antiserum inhibited cells. P. septica RNA was prelabelled with 32 P or [ 14 C] uracil, the organisms resuspended in unlabelled horse serum and antiserum added. The label remained in the RNA for up to 45 min after the addition of antiserum but was lost very rapidly thereafter. By the 90th min, 80–90% had been lost, this loss being reflected by the appearance of labelled material in the serum. Sucrose gradient analysis showed that the ribosomes were lost from such inhibited cells and that the ribosomal RNA was broken down before it was lost from the cells or even released from the ribosomal particles. Addition of haematin to the system prevented both the inhibition of bacterial growth and the subsequent breakdown of RNA. A similar degradation of ribosomal RNA was seen when antiserum was added to P. septica growing in rabbit serum, although in this case, antiserum produced bacteriostasis instead of the lethal effect seen in horse serum.

Lipopolysaccharide prepared from cells of Yersinia ( Pasteurella ) pseudotuberculosis of serogroups I, II, III, IV, and V is known to contain the 3,6-dideoxyhexose (DDH) paratose, abequose, paratose, tyvelose, and ascarylose in its respective O-specific side chains. Lipopolysaccharides or lipid-free polysaccharides of all of the 10 known serogroups and subgroups were subjected to methylation analysis and determined as alditol acetates by gas-liquid chromatography and mass spectrometry. The results indicated that the O-specific side chains of nine serotypes are composed of oligosaccharide repeating units in the form of four alternative general structures in which a terminal DDH may vary. These structures are DDH [Formula: see text] 6-deoxy- d - manno -heptose [Formula: see text] d -galactose (serogroups IA, IIA, and IVB), DDH [Formula: see text] d -mannose [Formula: see text] l -fucose (serogroups IB and IIB), and two configurations similar to the latter except that the 4-position of l -fucose was either linked to the d -mannose residue (serogroups VA and VB) or to the DDH residue (serogroups III and IVA). In contrast, O-groups in lipopolysaccharide of the newly discovered serogroup VI contained the DDH colitose and 2-acetamido-2-deoxy- d -galactose. Accordingly, all five known types of DDH have now been detected in lipopolysaccharides of Y. pseudotuberculosis . The sugar 6-deoxy- d - manno -heptose, present in O-specific side chains of serogroups IA, IIA, and IVB, has not yet been reported to occur elsewhere in nature.

Detection and intensity of urease activity in enterobacteriaceae greatly varies as a function of the media or techniques used, or both. A comparative investigation on several solid and liquid media led us to the following conclusions. (i) Detection of Proteus spp. can be adequately performed with the highly selective solid medium described by Cook (1948), as well as with the different liquid media described (Stuart standard and rapid media; Elek medium). (ii) Detection of Klebsiella should be based upon urease production on solid media with low buffer capacity (Christensen, 1946). (iii) For the identification of Yersinia , either the solid Christensen urea agar or the rapid Elek technique give optimal results.

SUMMARY Of 358 carbohydrate tests carried out independently by two diagnostic laboratories on 28 Pasteurella pneumotropica isolates, the results of 273 were in agreement, 65 were judged uncertain by one laboratory, and 20 were contradictory. On the other hand, the following corroborated atypical reactions were found: negative catalase reaction (one strain), gas production in maltose (one strain), acid production in mannitol (one strain), and weak or absent indole production (14 strains). A strain of P. pneumotropica from rats produced on subculture typical colonies together with a proportion of white, beta-haemolytic colonies of a variant that was indole negative, gave a stronger oxidase reaction, and acidified raffinose, trehalose and dulcitol, in addition to the carbohydrates acidified by the wild type.

Two isolates of Yersinia enterocolitica recently found in humans in North America and one isolate of flea origin killed mice after sc inoculation. Median lethal doses varied from 1.6 x 104 to 54 x 104 bacteria. Of 11 remaining isolates tested in mice, all but four produced distinct morbidity without extensive mortality. The LD50 after ip inoculation was 1,000-fold less than after sc inoculation into mice. One selected isolate was also tested in gerbils. All gerbils inoculated ip with as few as 250 organisms died within four days. These findings indicate that this bacterial species can no longer be considered to be nonlethal for laboratory animals. Studies of the pathology and immunopathology of Y. enterocolitica disease processes, which were previously impractical because of the lack of suitable susceptible experimental animals, are now possible.

Many laboratory animals are known to harbor infectious agents which produce spontaneous disease or are present in a latent state. Swiss mice have been studied with special care in this respect, and a number of bacteria1-7 and other organisms8'9 have been found to produce epizootic outbreaks from time to time in breeding colonies. Increasing interest in human respiratory infections has led to many attempts to adapt agents causing such diseases to small laboratory animals for more convenient study. Blind passage of lung material by the respiratory route under ether anesthesia frequently led to the production of lung lesions in the experimental animals due to the activation of latent agents. A number of latent viruses10-16 and pleuro

1. In the experiments here presented, P. avicida proved incapable of inciting fowl cholera when introduced directly into the alimentary tract. On the other hand, when administered into the upper respiratory passages, it induced typical disease. 2. When P. avicida was introduced into the nasal passages of controlled, selected chickens, some died of typical septicemic cholera, a few developed chronic pneumonias and other conditions and succumbed, a few developed localized upper respiratory inflammations, such as rhinitis, roup, and wattle involvement, while yet a few others became "healthy" nasal carriers. Usually, however, more than 50 per cent resisted infection. Repeated titrations of this sort gave, in general, uniform results, save that in spring and summer the per cent mortality decreased. 3. P. avicida was recovered from a number of cases of "spontaneous" roup, rhinitis, and wattle disease. 4. Groups of chickens reacted similarly to doses of virulent P. avicida varying from 20,000,000 to 20,000. Outside these limits, dosage exercised a marked influence on mortality.

Seventeen cases of mesenteric adenitis were investigated between May and October, 1959, for the presence of virus as well as for evidence of Pasteurella pseudotuberculosis infection. Specimens examined included mesenteric glands, appendix, throat swab, faeces, and serum, although glands were received from only 12 patients. Virus was not isolated from any of the specimens, but evidence of infection with Pasteurella pseudotuberculosis was obtained in three patients. The three cases of acute mesenteric lymphadenitis due to Pasteurella pseudotuberculosis are reported. Pasteurella pseudotuberculosis Type IA was isolated from the mesenteric glands of two of the cases, and all three cases showed serological evidence of infection with the organism. The mesenteric glands of two of the cases showed histological changes characteristic of pseudotuberculosis.

SUMMARY: From strains of Pasteurella pseudotuberculosis representing each of the five serological groups and some ‘Rough’ forms, lipopolysaccharides were isolated after disintegration of acetone-dried saline extracted organisms with phenol. The materials appear to carry the specificities on which the serological classification of the species is based; they are relatively poor antigens when isolated but antigenicity can be enhanced by combining with lipoprotein. Analyses show some unusual features, an aldoheptose sugar being present in all of the materials and some of the ‘Smooth’ cell products contain dideoxy sugars; rhamnose is absent. The ‘Rough’ cell products are somewhat similar in composition to the ‘Rough’ somatic polysaccharide of Pasteurella pestis, to which they are also related serologically.

Data are presented, demonstrating that infection with Rickettsia typhi brings about a reduction of the death rates and a prolongation of the time of survival in animals subsequently challenged with Pasteurella pestis or Pasteurella tularensis. This interference with bacterial infection by previous rickettsial infection does not appear immediately after injection of the rickettsiae; it begins to appear around 16 hours after this injection and becomes more marked during the first 96 hours; later it decreases. The phenomenon is essentially a local tissue reaction with weaker systemic effects. The phenomenon of interference can be overcome by challenge with too large a number or too virulent a strain of bacteria. A strain of P. pestis subjected to 10 passages through mice infected with Rickettsia typhi failed to develop resistance to the interfering activity of the latter microbial species. This does not rule out, but might be evidence against, an assumption that the interfering action is due to antibiotic effects from the rickettsiae.

Anhand der Literatur und eigener Untersuchungen wird uber die Taxonomie von Yersinia enterocolitica und uber die Klinik, Pathogenese, Epidemiologie, Therapie und Diagnose der von ihr beim Menschen ausgelosten Infektionen berichtet. Die bisher bestehende diagnostische Unsicherheit durch Fehlen einheitlicher bakteriologischer und serologischer Untersuchungsverfahren wird aufgezeigt. 46 durch Erreger-und/oder Antikorpernachweis atiologisch gesicherte Infektionen beweisen, das auser der Erregerisolierung dem O-Agglutininnachweis mit gekochten Antigenen bei Infektionen mit Stammen der Gruppen I und V die groste diagnostische Bedeutung zukommt. Der Antikorper-bzw. Erregernachweis gelang in 7,5 bzw. 1,9% der untersuchten Serum- bzw. Stuhlproben. Einzelheiten sind den tabellarischen Zusammenstellungen und kasuistischen Beitragen zu entnehmen.

Ninety-nine nasal swab isolates of organisms resembling colonially Pasteurella haemolytica, but not assignable to any existing serotype, were subjected to differential tests in order to determine their true identity. Biochemical and microscopic examinations established the organisms as bearing the characteristics of Past. haemolytica although fermentation tests and somatic agglutination left the relationship of these strains to the typable strains of biotypes A and T uncertain.

BIERER and Eleazer (1968) and Bierer Scott (1968) reported that either continuous use or use once every 2 weeks of an attenuated live Pasteurella multocida vaccine in the drinking water conferred a significant degree of immunity against fowl cholera disease in turkeys. Heddleston and Rebers (1968) reported that active immunity was induced in chicks and turkeys by oral administration of a killed P. multocida vaccine. This experiment was undertaken to determine whether an attenuated killed drinking water vaccine would confer a similar degree of immunity as the same attenuated drinking water vaccine, but unkilled. Also, a comparison was made between the live drinking water vaccine and five commerical injected bacterins that are in common use. MATERIALS AND METHODS Four hundred 8-week-old Broad Breasted White tom turkeys were placed in groups of 50 in each of eight experimental pens. The turkeys in pens 1, 2, 3, 4, and 5 were injected…

The susceptibility of homozygous BSVS mice to acute disseminated encephalomyelitis (ADE) has been found to be nutritionally dependent. On a laboratory stock regimen of commercial fox chow pellets, whole wheat bread, and milk this genotype is 100 per cent susceptible to the disease. On a "synthetic" diet, containing a minimal list of vitamins adequate for growth and maintenance, susceptibility was found to be reduced to 15 per cent. Supplementation of the "synthetic" diet with biotin, folic acid, and vitamin B12 restored susceptibility to a frequency of 70 per cent. Increasing the supplements tenfold had no further effect in restoring susceptibility frequencies to the 100 per cent level. In the restoration of susceptibility, folic acid and vitamin B12 were equally effective as single supplements and equivalent to the triple vitamin supplement. The effect of single biotin supplementation was less. An outbreak of fatal pasteurellosis among BSVS mice latently infected with Pasteurella and used in an ADE susceptibility test has been described. The fatal pasteurellosis has been ascribed to a constellation of determinants including (a) diet, (b) sex, (c) inoculation events, and (d) latent infection with Pasteurella. With males the susceptible sex it was possible to avert the fatal pasteurellosis and continue the nutritional experiments by using females exclusively.

SummaryDuring a three-month period in 1968,3875 sera sent in for rheumatoid factor tests were screened for agglutinating antibodies against two Yersinia enterocolitica serotypes. Nineteen of the 46 patients with a titer of 160 or higher had polyarthritis with acute onset. Of the remaining 27 patients 11 had erythema nodosum and eight febrile diarrhea, usually associated with some symptoms in joints. Most of the 19 patients with polyarthritis had preceding fever and gastrointestinal symptoms. Fingers, knees and ankles were most often affected. Three patients had acute sacro-iliitis and some others back pain or severe myalgia. In the initial phase the tests for rheumatoid factors were negative in all 19 cases. Mean ESR was 79 mm/hour in the acute phase. A significant reduction in the Y.enterocolitica titer took place within three months in every case. The duration of the arthritis was from one week to five months in the 15 cases in which the arthritis subsided during the follow-up period of eight to eleven ...

By immunodiffusion and immunoelectrophoresis tests in agarose serological cross-reactions were demonstrated between Yersinia enterocolitica type IX and Brucella strains from four species (Brucella abortus, Brucella melitensis, Brucella suis and Brucella neotomae). No qualitative differences between these strains in their tendencies to cross-react with Yersinia enterocolitica type IX were observed. Brucella canis and Brucella ovis, which have nonsmooth colonial morphology, gave no demonstrable cross-reaction with Yersinia enterocolitica type IX. The results of absorption tests and qualitative staining reaction of the obtained precipitation lines suggest that the antigenic determinants common to Brucella and Yersinia enterocolitica type IX seemed to be associated with the outer layer and in the lipopolysaccharide complex of the respective bacteria. By immunodiffusion and immunoelectrophoresis it was possible to identify in hyperimmune sera those antibodies that derive from Brucella and Yersinia enterocolitica type IX. Immunodiffusion och immunoelektrofores. Med hjalp av immunodiffusion och immunoelektrofores i agarose har en serologisk korsreaktion pavisats mellan Yersinia enterocolitica typ IX och Brucella stammar fran 4 olika species (Brucella abortus, Brucella melitensis, Brucella suis och Brucella neotomae). Nagra kvalitativa skillnader for dessa stammar med avseende pa deras benagenhet att korsreagera med Yersinia enterocolitica typ IX har inte kunnat pavisas. Brucella canis och Brucella ovis, som ar kolonimorfologiskt av R-typ, har icke givet nagon pavisbar korsreaktion med Yersinia enterocolitica typ IX. Resultaten fran gjorda absorptionsforsok och kvalitativa fargningsreaktioner av erhallna precipitationslinjer tyder pa att de gemensamma antigena determinanterna for Brucella och Yersinia enterocolitica typ IX torde finnas hos respektive bakteriecellers ytskickt och i deras lipopolysackaridkomplex. Immunodiffusion och immunoelektrofores visar en mojlighet att i hyperimmunsera kunna identifiera de antikroppar som harror fran Brucella respektive Yersinia enterocolitica typ IX.

SummaryRNA was extracted with 10% NaCl from acetone-dried cells of Past, mul-tocida and deproteinized by treatment with the chloroform-octanol mixture. After alkaline hydrolysis, CMP, AMP, UMP and GMP were separated by anion exchange chroma-tography and paper ionophoresis. The nu-cleotides were tightly bound to peptide material. Nucleotide-peptide complexes were also detected in the TCA-soluble extract from Past, multocida.

A study of a Gram-negative pleomorphic organism, Hemophilus aphrophilus, isolated from the blood of a patient with clinical bacterial endocarditis, presented a problem in identification. The literature on bacteriologic technic is replete with detailed methods for the isolation and identification of Grampositive cocci and Gram-negative enteric bacilli. However, little clear-cut information is given on the differentiation of Gram-negative pleomorphic organisms belonging to the genera Hemophilus, Pasteurella, Brucella, or Actinobacillus. Ordinarily these organisms have been thought of in relation to well defined clinical situations, i.e., Hemophilus influenzae from the nasopharynx or spinal fluid of an infant, or else to be of such rare occurrence, i.e., Pasteurella pestis, as not to present a problem in the routine hospital laboratory. Upon perusal of the recent literature, however, several reports of unusual types of human infection due to organisms of the Gram-negative pleomorphic type are noted. These reports cite the increased frequency of human infections caused by previously undescribed organisms, and refer to bacteria previously regarded as animal pathogens. Several articles contain statements affirming the ease with which these organisms may be confused with other bacteria and give complete morphologic, biochemical, and serologic characterization of the particular organism under discussion, but fail to indicate how these organisms might effectively be differentiated in the routine hospital laboratory. That this problem is not unique to our laboratory became apparent when we submitted the organism to other laboratories where similar difficulties were experienced. The organism in our case was finally identified by the staff of the Communicable Disease Center in Atlanta, Georgia.

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Viable attenuated tularemia vaccines have been shown to be effective in immunizing mice and other animals against challenge with highly virulent Pasteurella tularensis. Nonviable preparations, however, induced little or no resistance to challenge with even small numbers of virulent organisms. It seemed reasonable to expect that antigenicity would be retained to a greater extent if the organisms were killed by irradiation rather than by chemicals or heat. Vaccines rendered nonviable by the action of X-radiation produced levels of immunity such that 20 to 30% of immunized mice survived intraperitoneal challenge with moderate doses of the highly virulent SCHU S4 strain. Cysteamine at a concentration of 0.02 M was added to the bacterial suspension prior to irradiation to minimize the indirect effects of irradiation. Vaccines contained approximately 10 sup 9 nonviable organisms per milliliter. Proof of nonviability of irradiated vaccines was based on (a) absence of colonies when irradiated vaccines were plated on solid medium, (b) failure to isolate P. tularensis from sacrificed immunized animals, and (c) the inability of treatment with streptomycin during immunization to interfere with the development of immunity.

Pasteurella pneumotropica is a potential pulmonary pathogen in mice. In healthy animals, this organism was killed rapidly by the normal function of the intrapulmonary phagocytic defense mechanisms. Impairment of this bactericidal activity by the acute renal failure of nephrectomy resulted in multiplication of the Pasteurella in the lung, both when the animals were nephrectomized first and then infected, and when the animals were infected first and nephrectomized several hours after the infection. The study demonstrates that the pathogenicity of the Pasteurella organisms is governed by the functional state of these pulmonary antibacterial mechanisms.

Summary (1) One hundred calves dying within the first few months after birth were examined, and an attempt has been made to classify on an aetiological basis the diseases of calves occurring in this country. (2) In 69 cases it was possible to isolate and identify the associated organism or organisms. (3) Pure infections with Bact. coli accounted for 37 cases, C. pyogenes for 12, haemolytic coccobacilli for six, Salmonella typhi-murium for two and Pasteurella for one. (4) Mixed bacterial infections accounted for 11 cases, such organisms as Staph. aureus and Ps. pyocyonea being present in addition to certain of those encountered in pure infections. (5) In the remaining 31 cases the aetiology was doubtful, indicated causes not considered bacterial, or associated with bacteria which could not be identified with any known species.

A respiratory infection commonly called infectious pneumonia, or hemorrhagic septicemia, has long been known to affect sheep. In the typical form there is an acute pneumonia with hemorrhagic lesions most evident on the serous surfaces of the lungs and heart. An intense septicemia usually occurs at death, and a highly pathogenic organism of the pasteurella group may be almost constantly isolated from the heart blood either by direct inoculation on blood agar or by inoculation of rabbits, which are very susceptible to pasteurella infections.

1) Minimal inhibitory concentrations (MIC) of Moenomycin1) (so called Flavophospholipol) for various fish-pathogenic bacteria isolated from different cultured fishes in Japan and effects of Moenomycin for R factors of gram negative-bacilli isolated from the cultured fishes were examined in vitro.2) MIC levels of Moenomycin for various fish-pathogenic bacteria except Chondrococcus columnaris were within a range from 0.2 to 3.1 μg/ml. MIC level for C. columnaris was 50.0 μg/ml. Especially the MIC levels of Moenomycin for Vibrio anguillarum and the pathogenic agent of bacteria-tuberculoidosis2) (Pasteurella piscicida3)) were almost the same as the levels of Chloramphenicol, Thiamphenicol and Chlortetracycline or showed a little stronger.3) MIC levels of Moenomycin for the R- and R+ strains of Aeromonas liquefaciens 67-P-24 were examined. Eleven strains of gram negative-bacilli carrying R factors isolated from intestines of cultured eels (Anguilla japonica) were used as donors and Escherchia coli CSH-24) as the recipient. The R factors transferred to E. coli CSH-2 were then each transferred to a R- strain, Aeromonas liquefaciens 67-P-24.MIC level of Moenomycin for the R- strain was 3.1 μg/ml, while those for R+ strains were all 1.6 μg/ml. This suggested that Moenomycin has a stronger anti-bacterial effect for drug resistant bacteria carrying R factors than for bacteria not carrying it.4) A comparative study of the growth curves of R- and R+ strains of Aeromonas liquefaciens incubated at 30°C in Penassay broth (Difco) containing various amounts of Moenomycin revealed that antibacterial effect of Moenomycin is stronger against the R+ strain than the R- strain.

Summary1. The therapeutic effect of streptomycin was evaluated in mice infected with a pneumotropic pasteurella either by the respiratory or by the intracerebral route.2. When treatment was started within 4 hours after infection intracerebrally mice could be saved by streptomycin injected subcutaneously. With a total dose of 0.3 g/kg streptomycin the main factor determining success of therapy was the time interval between infection and first administration of antibiotic.3. With comparable dosage regimens larger amounts of streptomycin were necessary to cure the intracerebral than the respiratory infection.4. When treatment of the pulmonary infection was delayed for 18 hours, until symptoms and lesions were present, marked differences appeared in the effectiveness of dosage schedules similar in their effects when treatment was started soon after infection.5. The possible usefulness of “natural” type infections in chemotherapeutic experiments is discussed and compared to the “test-tube” type of experimental...

Specific activities and electrophoretic mobilities of glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase were determined in 38 isolates of the family Enterobacteriaceae and in 10 isolates of the related Pasteurella . The deficiency of glucose-6-phosphate dehydrogenase in P. pestis was verified. Enzymes obtained from different strains of the same species exhibited an unexpected degree of heterogeneity. For example, 8 and 11 apparent variants of glucose-6-phosphate dehydrogenase and phosphogluconate dehydrogenase, respectively, were found in 14 strains of Escherichia coli . Although similar frequencies of heterogeneity were noted in 7 strains of P. pseudotuberculosis , 5 species of Shigella , and 8 species of Salmonella , differences in mobility were generally small in comparison with those observed between strains of E. coli . Values obtained for the pasteurellae, shigellae, and salmonellae, thus fell within narrow ranges that may prove typical for the genera. However, most of these ranges, as well as many values observed for single species of other genera, were overlapped by the wide range recorded for E. coli . The significance of this observation was discussed with respect to the relative age and taxonomic position of the organisms in question. The method could be used to distinguish between most wild-type strains of the same species and should thus facilitate investigations of genetic transfer and epidemiology.

A heat-stable, particulate, lipopolysaccharide-protein antigenic complex has been isolated from a virulent, encapsulated strain of Pasteurella multocida by extraction with cold, formalinized saline, and centrifugation at 105,000 × g . The original bacterial culture had been obtained from a bison that died of hemorrhagic septicemia, an infectious disease of cattle and buffalo. Injection of fractional milligram amounts of the antigen into mice, rabbits, and calves produced toxic reactions which frequently resulted in death of the host. The surviving animals demonstrated a high degree of immunity to challenge with live, virulent organisms. Two injections with 15 μg of the antigen produced a high degree of immunity in mice without the development of any signs of toxicity. The gross chemical composition and toxicity of the antigen were similar to those reported for endotoxins obtained by the Boivin or Westphal procedure. Although strong serological cross-reactions were obtained in Ouchterlony plates between the 105,000 × g antigens from the bison strain and an avian strain with antisera to these strains, these antisera agglutinated only the bacterial cells of the homologous strain. The active immunity obtained in mice by the injection of the 105,000 × g antigens of each strain was specific and could be correlated with the agglutination tests.