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An epidemiologic study of Pasteurella haemolytica serovar 1 (Ph1) in market-stressed feeder calves from 7 farms in eastern Tennessee was conducted. The nasal mucus of each calf was cultured sequentially at the farm of origin (day 0), at an auction market (day 133), and at a feedyard in Texas (days 141, 148, 155, and 169). Of the 103 calves tested, 77 were culture-positive, including 1 on day 0, 1 on day 133, 20 on day 141, 57 on day 148, 50 on day 155, and 14 on day 169. From the 143 Ph1 isolates, 20 enzyme profiles were determined by use of a commercial enzyme system that detects 19 enzymatic reactions; 4 antimicrobial susceptibility profiles were obtained, using the disk-diffusion method, which evaluated susceptibility to 11 antibacterial drugs. All isolates were positive for acid phosphatase and alkaline phosphatase, but were negative for alpha-galactosidase, alpha-mannosidase, beta-glucosidase, beta-glucuronidase, cystine aminopeptidase, N-acetyl-beta-glucosaminidase, and trypsin. Other positive enzyme reactions included: leucine aminopeptidase, 140 Ph1 isolates; phosphohydrolase, 90 isolates; alpha-fucosidase, 63 isolates; esterase (C4), 59 isolates; valine aminopeptidase, 30 isolates; esterase lipase (C8), 24 isolates; beta-galactosidase, 2 isolates; and alpha-glucosidase, chymotrypsin and lipase (C14), 1 isolate each. Thirty-four Ph1 profiles were identified, using combined enzyme and antimicrobial susceptibility profiles. The data indicate that the strains isolated during the feedyard period may have been determined more by farm of origin (P < or = 0.001) than by habitation with calves from other farms while in the feedyard.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolates of Fusobacterium necrophorum were obtained from 124 bovine hepatic abscesses (in 119 cattle) and from the ruminal contents of 12 cattle. Three biotypes (A, AB, and B) were found. Type A isolates were most common in hepatic abscesses, and type B isolates were most common in ruminal contents. Virulence studies in mice indicated that type A isolates were more pathogenic than types AB or B isolates. The difference in virulences between types A and B isolates was not related to the toxicity of the endotoxin. Results of serotesting (passive hemagglutination) showed that a wide heterogeneity existed between isolates. Minimal inhibitory concentrations of antibiotics for 12 of the isolates (7 type A, 1 type AB, and 4 type B) were as follows: less than or equal to 0.06 IU of penicillin G/ml; less than or equal to 0.5 micrograms of cephaloridine/ml; less than or equal to 2 micrograms of chloramphenicol/ml; less than or equal to 0.06 micrograms of clindamycin/ml; less than or equal to 8 micrograms of erythromycin/ml; less than or equal to 128 micrograms of gentamicin/ml; less than or equal to 0.25 micrograms of oxytetracycline/ml; and less than or equal to 4 micrograms of tylosin/ml.

Fusobacterium necrophorum is considered to be a member of the normal rumen flora and is the primary etiologic agent of bovine liver abscesses. Of the three biotypes of F. necrophorum, A, B, and C, only biotypes A and B have been implicated in the disease. Type B is the predominant biotype isolated from ruminal lesions and type A is the predominate biotype isolated from liver abscesses. Type A is usually found in pure culture in the liver abscesses; whereas, type B is usually found in mixed culture with either type A or with other bacterial species. Corynebacterium pyogenes, Streptococcus spp., Staphylococcus spp., and Bacteroides spp. are the most prevalent bacteria recovered from mixed cultures. Corynebacterium pyogenes is the most common species isolated and can cause disease synergistically with type B isolates.

A 4-year-old beefmaster cow was examined for a left hind leg lateral claw lameness due to septic arthritis of the distal interphalangeal joint and associated osteomyelitis of the second and third phalanges. Actinomyces pyogenes and Fusobacterium necrophorum, which have been demonstrated previously to act synergistically in ovine heel abscesses, were isolated from the affected digit. A claw amputation was performed because of the advanced destructive nature of the lesion.

Viable cultures of Fusobacterium necrophorum were inoculated into the hepatic portal veins of 7 cattle. The experimentally produced hepatic necrobacillosis lesions were described from 30 minutes through 36 hours. The lesions were established by 2 different host-bacterial interactions. Most frequent, microabscesses were initiated by diffusely distributed bacteria and were observed from 30 minutes through 2 hours. Gross abscesses from 3 through 8 hours had centrally located abscess cores and were encircled by leukocytes which were predominantly neutrophils. Lesions from 12 through 36 hours had abscess cores that were encircled by leukocytes which were predominantly macrophages. Less frequent, emboli of F. necrophorum initiated infections in hepatic sinusoids or telangiectatic lesions. Hepatocytes adjacent to the bacteria exhibited coagulation necrosis and few leukocytes were observed in these lesions.

The biochemical characteristics of the leukotoxins of 3 bovine isolates of Fusobacterium necrophorum which represent biotypes A, AB, and B were compared. Two methods were used for the production of the leukotoxins: medium M-1 continuous dialysis sac cultures and brain-heart infusion agar plate cultures. The supernatant cultural fluids were fractionated sequentially by membrane-partition chromatography, using ultrafilters with approximate molecular weight (mol wt) exclusion limits of 100,000, 10,000, 2,000, and 500. The ultrafiltrates (less than 500 mol wt) were fractionated by gel-permeation chromatography, using G-10 Sephadex. The leukotoxins of the 3 F necrophorum strains were estimated to have a molecular weight between 350 and 450. The leukotoxins in the ultrafiltrates (less than 500 mol wt) were stable at 60 C for 4 hours and at 100 C for 30 minutes, stable to extremes of pH (3 to 11), and stable to degradative enzymes including trypsin, protease, alpha-amylase, lipase, deoxyribonuclease, and ribonuclease. Significant differences were not observed in the biochemical characteristics of the leukotoxins produced in vitro by the 3 F necrophorum biotypes. These assays were done, using monolayers of mouse peritoneal macrophages. The monolayers were exposed to the 4 ultrafiltrates of both the continuous dialysis sac and brain-heart infusion agar cultures (pH 7.2) for 4 hours at 4 C, 25 C, and 37 C. Maximal cytotoxic activity in the assays was at 37 C.