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SUMMARY

Hepatic abscesses were induced experimentally in 5 steers by inoculating Fusobacterium necrophorum via ultrasonography-guided, percutaneous catheterization of the portal vein. Hepatic ultrasonography was performed to determine the onset and progression of abscessation. Blood samples were collected before and after inoculation for performing leukocyte counts and hepatic function tests. Ultrasonographic evidence of liver abscesses was observed as early as 3 days after inoculation. Abscesses appeared as hyperechoic centers (cellular debris and pus) surrounded by hypoechoic or anechoic areas (fluid). Increases in rectal temperature, leukocyte counts, fibrinogen, globulin, bilirubin, γ-glutamyltransferase, and sorbitol dehydrogenase concentrations were detected. Hepatic dysfunction was evidenced by decrease in serum albumin concentration and low sulfobromophthalein clearance. The ultrasonographic diagnosis of abscesses correlated well with necropsy findings.

Free access
in American Journal of Veterinary Research

SUMMARY

Objective

To determine the resistance and susceptibility to antimicrobial compounds of Fusobacterium necrophorum isolates from bovine hepatic abscesses.

Procedure

37 isolates of F necrophorum (21 subsp necrophorum and 16 subsp funduliforme) isolated from bovine hepatic abscesses were obtained from cultures grown and maintained in anaerobic brain heart infusion broth. A broth dilution method was used as an initial screening to determine general susceptibility to 31 antimicrobial compounds. The minimal inhibitory concentrations (MIC) of 19 of the antimicrobial compounds that inhibited growth in the initial test were determined by use of the broth microdilution method.

Results

Fusobacterium necrophorum isolates were generally susceptible to penicillins, tetracyclines (chlortetracycline and oxytetracycline), lincosamides (clindamycin and lincomycin), and macrolides (tylosin and erythromycin), and were resistant to aminoglycosides (kanamycin, neomycin, gentamicin, and streptomycin), ionophores (except narasin), and peptides (avoparcin, polymyxin, and thiopeptin). The 5 antimicrobials (bacitracin, chlortetracycline, oxytetracycline, tylosin, and virginiamycin) that have FDA approval for prevention of liver abscesses in feedlot cattle were inhibitory to F necrophorum. Differences in antimicrobial susceptibility patterns were observed between the 2 subspecies only for clindamycin and lincomycin. The MIC of F necrophorum isolates from antibiotic-fed cattle were similar to those for isolates from nonantibiotic-fed cattle.

Conclusions

The MIC of FDA-approved antibiotics were not reflective of the efficacy of antibiotics in preventing liver abscesses in feedlot cattle. Also, continuous feeding of tylosin did not appear to select resistant F necrophorum. (Am J Vet Res 1998;59:44–47)

Free access
in American Journal of Veterinary Research

Summary

Biological and biochemical characteristics of the leukotoxin of Fusobacterium necrophorum were determined. Culture supernatant of F necrophorum was toxic to polymorphonuclear neutrophilic, leukocytes from cattle and sheep, but not to those from pigs and rabbits. Culture supernatant and sonicated bacterial cell fractions had low hemolytic activity and did not cause dermonecrosis in a guinea pig. Supernatant derived leukotoxin was inactivated at 56 C for 5 minutes and became unstable at pH > 7.8 or < 6.6. Chemical treatment with 0.1% sodium dodecyl sulfate, 0.25% sodium deoxycholate, 5.2% sodium sulfide, or 0.25 mM titanium (III) citrate markedly decreased leukotoxicity. Enzymatic treatment with protease, trypsin, and chymotrypsin inactivated the toxin completely, whereas amylase had no effect. Use of protease inhibitors failed to prevent loss of leukotoxin activity. Using membrane partition chromatography and gel filtration, the estimated molecular weight of the toxin was > 300,000. On reduction and denaturation, the toxin dissociated into several components by use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To isolate Actinomyces pyogenes and A pyogenes-like (APL) organisms from the ruminal wall and ruminal contents of cattle and compare them with isolates from liver abscesses from the same animals, using ribosomal DNA restriction fragment length polymorphism analysis or ribotyping.

Procedure

Specimens of liver abscesses, ruminal walls, and ruminal contents were collected from 59 cattle at slaughter. All β-hemolytic, pinpoint colonies that were gram positive, pleomorphic rod-shaped, and catalase negative, and that hydrolyzed casein and gelatin were presumptively identified as A pyogenes and were characterized biochemically, using an identification kit. The isolates that resembled A pyogenes but fermented mannitol or raffinose, or both, were called APL organisms. Isolates from the ruminal wall and ruminal contents were compared with liver abscess isolates from the same animal by use of ribotyping.

Results

Actinomyces pyogenes and APL organisms were isolated more frequently from the ruminal wall than from ruminal contents. Ruminal isolates of A pyogenes and APL had biochemical characteristics similar to those of the isolates from liver abscesses. Among 6 sets of isolates (4 A pyogenes and 2 APL), 2 isolates from liver abscesses had ribopatterns identical to the corresponding ruminal wall isolates. Also, the APL organisms isolated from the ruminal content matched with the corresponding liver abscess isolates for both sets of specimens tested.

Conclusions

The ruminal wall may be the niche for A pyogenes and APL organisms in the rumen. The genetic similarity, on the basis of ribotyping among isolates from liver abscesses, the ruminal wall, and ruminal contents of the same animal suggests that A pyogenes and APL organisms that cause liver abscesses originate from the rumen. (Am J Vet Res 1998;59:271–276)

Free access
in American Journal of Veterinary Research

Abstract

Objective

To determine the efficacy of leukotoxin-based Fusobacterium necrophorum vaccines and dietary tylosin in providing protection against experimentally induced hepatic abscesses in steers.

Design

30 steers assigned randomly to 6 treatment groups of 5 steers each: 1, phosphate-buffered saline solution (PBSS; control); 2, PBSS control, fed tylosin (100 mg/steer) daily; 3, inactivated whole-cell culture with oil emulsion adjuvant; 4, culture supernatant (crude toxoid) with oil emulsion adjuvant; 5, semipurified leukotoxoid with oil emulsion adjuvant; and 6, semipurified leukotoxoid with saponin adjuvant.

Procedure

Steers were inoculated SC with emulsified antigen or PBSS on days 0 and 21. Blood samples were collected at weekly intervals to monitor serum antileukotoxin antibody titer. On day 42, all steers were challenge exposed intraportally with F necrophorum culture. Three weeks later (day 63), steers were euthanatized and necropsied to examine liver and assess protection.

Results

Antileukotoxin antibody titers of all vaccinated groups markedly increased from baseline values, and mean titers of vaccinated groups were higher than those of the control and tylosin-treated groups. Steers vaccinated with culture supernatant with oil emulsion adjuvant or semipurified leukotoxoid with saponin adjuvant had the highest mean antibody titers. All 5 steers in the control group developed liver abscesses. Tylosin feeding did not protect steers challenge exposed with F necrophorum intraportally.

Conclusions

Culture supernatant was more protective than whole-cell culture or semipurified leukotoxin against experimentally induced hepatic abscesses. Partial purification of leukotoxin appeared to reduce its protective immunity. (Am J Vet Res 1996;57:483–488)

Free access
in American Journal of Veterinary Research