Objective-To evaluate the ability of bovine complement to kill a variety of field isolates and laboratory strains of Brucella abortus. Design-The experimental approach was to determine the sensitivity of B abortus isolates to killing by bovine serum, and to document the role of complement in brucellacidal activity. Sample population-Six laboratory isolates and 12 field isolates of B abortus were tested. Procedure-The ability of B abortus to survive exposure to undiluted bovine serum for 2 hours at 37 C was assessed. The role of complement in killing was determined by examining the ability of heat (56 C for 60 minutes) and cobra venom factor to obliterate the activity in serum, and by detecting binding of the ninth component of bovine complement to serum-sensitive target cells. Results-Isolates of B abortus that were resistant to the bactericidal activity of normal bovine serum were revealed. These included field isolates and laboratory strains. Furthermore, the study confirmed earlier reports that bovine serum-mediated killing of B abortus is caused by the complement cascade. Conclusions-Some isolates of B abortus, like other gram-negative bacteria, were resistant to complement-mediated killing. Resistance was associated with smooth colony morphology. Isolates lacking detectable O antigen were serum sensitive.

Genus-, subspecies-, and serotype 1-specific antigens of Chlamydia psittaci were characterized by immunoblot analysis, using monoclonal antibodies that recognize 2 C psittaci strains: AB7 isolated from an ewe that had aborted, and iB1 isolated from feces of a healthy ewe. Genus-specific epitopes were detected on lipopolysaccharide, on a 47-kd protein, and on a 27- to 30-kd doublet. Subspecies-specific epitopes were located on a 30-kd protein, and a 80- to 90-kd protein region was identified, which bore subspecies- and serotype 1-specific epitopes. These 80- to 90-kd proteins were highly reactive with serum from ewes that had aborted and could be a useful antigen for diagnosis of chlamydial induced abortion of ruminants.

Hemagglutinins HA) of H1N1 swine influenza viruses isolated in the United States have remained antigenically and genetically conserved for many years. In contrast to such conservation, the RA of A/Swine/Nebraska/1/92 (Sw/Neb) could readily be distinguished from those of contemporary porcine viruses. Twenty-eight amino acid mutations differentiated the HA of Sw/Neb and A/Swine/Indiana/1726/88, the most recent H1N1 swine influenza virus for which HA sequence data were available. Among these differences were mutations at potential asparagine-linked glycosylation sites and charge changes at many residues. The Sw/Neb virus also could be differentiated from other swine influenza viruses in hemagglutination-inhibition assays with monoclonal antibodies to recent H1 swine HA. Nonetheless, overall sequence analysis of the HA and the nucleoprotein genes of Sw/Neb indicated that this virus was more closely related genetically to classic H1N1 swine influenza viruses than to H1N1 avian or human viruses. Infection of swine with Sw/Neb under experimental conditions induced clinical signs and lesions typical of swine influenza. However, affected swine in the field had high, persistent fevers, but relatively mild signs of respiratory tract disease. This study indicated that an antigenically and genetically novel variant of swine influenza virus was detected in the United States.

Twenty-four 10-month-old Polled Hereford heifers were inoculated sc with live cells of one of the following strains of Brucella abortus: S19 delta 31K (n = 4), S19 delta SOD (n = 4), RB51 (n = 4), and strain 19 (n = 6); controls (n = 6) were given saline solution. Heifers given the deletion mutants S19 delta 31K and S19 delta SOD, and those given strain 19 developed antibody responses to B abortus and cutaneous reactions to brucellin. Heifers given strain RB51 did not develop antibodies that reacted in the standard tube agglutination test, but sera reacted in tests, using an antibody dot-blot assay containing RB51 antigen. The S19 delta 31K and S19 delta SOD strains of B abortus isolated from lymph node tissue after vaccination did not differ genetically from the master stock strain. All heifers were bred naturally at 16 to 17 months of age, and were challenge-exposed intraconjunctivally with virulent B abortus strain 2308 during the fifth month of pregnancy. All vaccinated heifers were protected (ie, none aborted and none had B abortus isolated from their tissues after parturition). Calves born from vaccinated dams were free of B abortus. Antibody responses in heifers after challenge exposure were an indicator of immunity. All 5 control heifers (nonvaccinated) developed serum antibodies after challenge exposure; 3 aborted, and 1 delivered a small, weak calf at 8.5 months of gestation. Thus, live mutant strains of B abortus can induce protective immunity when given at 10 months of age, and strain RB51 is a strong candidate for further testing.

To assess the role of enterotoxigenic (ETEC), verotoxigenic (VTEC), and necrotoxigenic (NTEC) Escherichia coli in cattle with diarrhea, 1,524 colonies of E coli isolated from 197 calves with diarrhea and from 112 healthy controls were investigated for production of heat-labile and heat-stable enterotoxins, verotoxins, and cytotoxic necrotizing factors (CNF1 and CNF2). The ETEC were isolated from only 2 (1%) calves with diarrhea and from 5 (4%) healthy controls. In contrast, VTEC and NTEC that produced CNF2 were frequently identified. The VTEC were isolated from 18 (9%) calves with diarrhea and from 21 (19%) healthy cattle (P < 0.05), whereas NTEC that produced CNF2 were detected in 39 (20%) ill calves and in 38 (34%) controls (P < 0.01). Therefore, VTEC and NTEC that produced CNF2 were isolated significantly more frequently from healthy than diseased calves. Serogroups to which VTEC belonged differed considerably from the O groups involved with NTEC. Although, VTEC belonged to 18 serogroups, only 4 (O26, O103, O113, and O157) accounted for 56% (25 of 45) of verotoxigenic strains. The NTEC that produced CNF2 belonged to 26 serogroups; however, 64% (69 of 108) were from 6 serogroups (O1, O3, O15, O55, O88, and O123). Our results are compatible with cattle being a reservoir of VTEC that are pathogenic for human beings and with ETEC being an unusual cause of bovine colibacillosis in Galicia (northwestern Spain). Furthermore, results of this study indicate that VTEC and NTEC that produced CNF2 may be part of the normal intestinal flora of cattle.

Ten controlled tests were done between 1972 and 1989, in lambs on pasture, evaluating activity of fenbendazole (FBZ; 5 mg/kg of body weight), oxfendazole (OFZ; 3.5 and 10 mg/kg), oxibendazole (OBZ; 10 mg/kg), pyrantel pamoate (PRT; 25 mg of base/kg), and thiabendazole (TBZ; 44 and 50 mg/kg) against natural infections of helminths, with emphasis on 2 strains (A and B) of Haemonchus contortus. Strain A was phenothiazine-susceptible and strain B was phenothiazine-resistant when isolated in 1955. For approximately 10 years prior to these tests, sheep infected with both strains had been treated periodically each year with several compounds, including thiabendazole, which was used many more times than the other drugs. For this study, 4 (FBZ, OFZ, OBZ, and PRT) of the 5 compounds were evaluated in either 1 or 2 controlled tests. The fifth compound, TBZ, was used for 5 tests. Strain A H contortus was resistant to TBZ for all years tested, but more susceptible to FBZ, OFZ, OBZ, and PRT. Overall, strain B was susceptible to TBZ (with a few exceptions), and also to FBZ, OFZ, OBZ (activity less on immature forms), and PRT. Other abomasal parasites (2 species of Ostertagia and 3 of Trichostrongylus) were found in low numbers, but removal overall was good for the compounds tested. Trichostrongylus axei, found in higher numbers than species of Ostertagia and other species of Trichostrongylus, were effectively removed by all compounds in most cases. Activities of TBZ and PRT were also evaluated against several species of intestinal helminths, most of which were found in low numbers. Cooperia curticei were inconsistently removed by TBZ, but activity of PRT was effective. Both compounds were active on mature Nematodirus spathiger, but TBZ had variable activity on immature forms. Strongyloides papillosus were effectively removed by TBZ. Other parasites found in lower numbers than the aforementioned 3 species were Capillaria spp, Trichuris spp, and Oesophagostomum columbianum; removal was variable for both drugs.

In an attempt to establish if cross protection can be induced by different strains of Haemophilus parasuis, three groups of 12 gnotobiotic pigs were immunized each with an aluminum hydroxide adsorbed whole cell bacterin of one of three H. parasuis strains. Two weeks later, four pigs within each vaccinated group were challenged with aerosols of live cultures of each of the three test strains and observed for response. Two virulent strains V1 and V2 protected all the vaccinated pigs, while all non-vaccinated controls succumbed to Glasser's disease when challenged with these strains. Vaccination with strain LV (of low virulence) protected the pigs against challenge with strain V2, but not against strain V1. Strain LV did not cause disease in the immunized animals and only in one of ten nonimmunized pigs upon second challenge. The results suggest that strains may differ in antigenicity and that virulence and immunoprotection are positively related. Strains to be used in commercial vaccines should therefore be selected carefully. Antibodies detected in the sera of vaccinated pigs were to outer membrane proteins of the bacteria, but not to lipopolysaccharides or capsular polysaccharides. This would suggest that for gnotobiotic pigs outer membrane proteins are more immunogenic than lipopolysaccharide or capsular antigens. Further work is needed to determine if outer membrane proteins also contribute protective immunogens.

Characteristics of 2 encephalomyocarditis virus (EMCV) isolates (MN-25 and MN-30) recovered from aborted swine fetuses were examined along with 2 other swine isolates (NVSL-MDV and NVSL-PR) and a reference ATCC strain (VR-129). All 5 EMCV isolates were found to be serologically related by cross testing, using serum neutralization and fluorescent antibody assays. Hemagglutination (HA) properties of the 5 isolates were compared, using 5 diluents. The MN-25 and NVSL-MDV strains had HA activity with guinea pig RBC in all 5 diluents, whereas MN-30, NVSL-PR, and VR-129 had HA activity only in KCl-borate buffer. The HA ability with RBC of various animal species was examined using KCl-borate diluent. All virus isolates had high HA titer (1:512 to 1:2,048) with guinea pig, rat, and horse RBC and lower HA titer (1:16 to 1:64) with sheep RBC. The MN-25 and NVSL-MDV isolates agglutinated dog RBC, whereas MN-30, NVSL-PR, and VR-strains 129 did not. Viral replication was evident in 8 of 10 cell lines tested, although infectivity titers of each virus varied by cell line used. Plaque-forming ability was similar for all 5 isolates, but plaque size was different by virus and cell culture used. Virus isolates were found to be stable after being heated at 56 C and subjected to a wide range of pH. A viral polypeptide pattern difference for all 5 isolates was not found by use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It was concluded that MN-25 and MN-30 are serologically related and have similar viral characteristics as those of previous EMCV isolates and the reference ATCC strain, although differences in HA ability could be observed.

Thirty-seven local isolates of Actinobacillus suis-like organisms from diseased and clinically normal horses and 1 Ilama were compared with reference strains of A suis, A lignieresii, A equuli, A capsulatus, A hominis, A (Pasteurella) ureae, and equine A suis-like organisms (ASLO) previously described in literature. Comparison was by cultural characteristics, carbohydrate fermentation, enzyme profiles, and whole-cell protein polyacrylamide gel electrophoresis. Carbohydrate fermentation, determined by API-CH gallery, divided 36 equine ASLO isolates into 6 API-CH biotypes. The Ilama isolate was an additional distinct biotype. The biochemical comparisons between A suis and ASLO did not reveal remarkable and consistent differences. Enzyme analysis revealed 5 API-ZYM biotypes, one of which included the same strains as one of the API-CH biotypes and consisted in both instances of 4 esculin-negative ASLO cultures and the reference strain of A lignieresii. We conclude that the 4 strains were hemolytic variants of A lignieresii. Protein electrophoresis disclosed 15 banding patterns, 10 of which represented equine ASLO strains. The reference strains of A suis shared the pattern predominant among equine ASLO. Four of the remaining reference strains of Actinobacillus species each had a unique profile, whereas the type strain of A capsulatus and the Ilama isolate had similar profiles. The groupings of cultures resulting from the different testing methods had little relation to each other and to the anatomic source of the strains except the strains comprising API-CH biotype III, which originated in the equine respiratory tract, and the A lignieressi cluster.

This work was an attempt to develop an in vitro adherence model for Mycoplasma hyopneumoniae, using monolayers of human and porcine lung fibroblasts and porcine kidney cells. Mycoplasma hyopneumoniae grown in Friis mycoplasma broth was radiolabeled with 35[S]-methionine, washed, concentrated, and inoculated on the monolayers. After 15 minutes of centrifugation to facilitate adherence, monolayers were washed 3 times, dissolved with 0.1N NaOH, and suspended in scintillation liquid, and the radioactivity was determined in a liquid scintillation counter. Adherence, measured as a percentage of counts added, varied according to the mycoplasma strain and the cell line used. Comparison of strains J, 144L, and 232 of M hyopneumoniae revealed 7.5 +/- 5.9, 31.9 +/- 13, and 9.6 +/- 5% adherence to porcine kidney cells, respectively. Slightly different, but proportionally the same relationships were obtained with swine or human fibroblasts. Adherence was decreased slightly by repeated washings of the mycoplasma-treated cell monolayers; however, a plateau was reached, indicating irreversibility of the adherence process. Pretreatment of cell monolayers with nonlabeled organisms substantially blocked adherence by labeled organisms. Dilution of labeled organisms resulted in an increased proportion adhering. Therefore, it appears that the adherence was a receptor-dependent event. Treatment of the mycoplasmas with trypsin prior to the inoculation of monolayers resulted in a marked reduction in adherence. Treatment of the mycoplasmas with hyperimmune swine serum against M hyopneumoniae or normal swine serum resulted in 80 to 90% reduction of adherence; however, no inhibition occurred when mycoplasmas were treated with purified IgG from the hyperimmune serum.