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Abstract

Objective

To determine prevalence of various pheno- and genotypes of Serpulina sp in young pigs in relation to diarrhea and feed medication in Swedish pig-rearing herds.

Design

Isolation of spirochetes. Phenotypical and genotypical classification.

Sample Population

Young pigs (n = 358) in 19 pig-rearing herds.

Procedure

Serpulina isolates were classified according to a biochemical scheme based on hemolysis, indole production, hippurate hydrolysis, and α-galactosidase, α-glucosidase, and β-glucosidase activities. The 16S rRNA sequences for 10 of the field strains and 2 type strains of Serpulina spp were aligned and compared. Minimum inhibitory concentrations of olaquindox for 9 of the strains were determined.

Results

Weakly β-hemolytic intestinal spirochetes (WBHIS) were isolated from 17 of the herds and 65% of the samples. More than 1 phenotype of WBHIS was found in 12 of the 19 herds. S hyodysenteriae was not isolated in any of the herds. Hippurate-positive WBHIS were isolated in 6 of 7 herds affected by diarrhea, but in only 1 of 8 herds without diarrhea. Hippurate-positive strains were closely related to the pathogenic strain P43 if judged from sequence comparisons. Strains with the same biochemical profile isolated within a herd had identical sequences, but when isolated from different herds, sequence differences were observed. The prevalence of WBHIS was reduced in herds medicated with olaquindox. Investigated field strains had minimum inhibitory concentration values ≤ 1 μg/ml for olaquindox.

Conclusion

The presence of WBHIS, with the ability to hydrolyze hippurate, was related to diarrhea in pig herds.

Clinical Relevance

Potentially pathogenic WBHIS can be distinguished from nonpathogenic strains by the hippurate hydrolysis test. (Am J Vet Res 1996;57:807–811)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To evaluate and compare the in vitro antifungal properties of lufenuron and nikkomycin Z against isolates of Coccidioides immitis and Aspergillus fumigatus when used singly and in combination with the azole antifungal agent itraconazole.

Sample Population—3 clinical isolates of A fumigatus and the Silveira strain of C immitis.

Procedure—The fungal isolates were tested in vitro for susceptibility to the single and combination of compounds by use of microtiter-format susceptibility methods. Minimum inhibitory concentration end points were determined visually, and the contents of representative wells were examined microscopically for evidence of morphologic effects on fungi.

Results—No evidence of inhibition, either by susceptibility testing or direct microscopic examination of treated cells, was obtained with lufenuron under experimental conditions. In contrast, nikkomycin Z, a known inhibitor of fungal chitin synthesis, had potent activity against C immitis when used singly. A synergistic interaction between nikkomycin Z and itraconazole was found against isolates of both species tested.

Conclusions and Clinical Relevance—On the basis of our in vitro data, lufenuron does not appear to possess antifungal properties. ( Am J Vet Res 2005;66:1090–1093)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine the pharmacokinetics of ceftazidime following subcutaneous administration and continuous IV infusion to healthy dogs and to determine the minimum inhibitory concentration (MIC) of ceftazidime for clinical isolates of Pseudomonas aeruginosa.

Animals—10 healthy adult dogs.

Procedure—MIC of ceftazidime for 101 clinical isolates of P aeruginosa was determined in vitro. Serum concentrations of ceftazidime were determined following subcutaneous administration of ceftazidime (30 mg/kg of body weight) to 5 dogs and continuous IV infusion of ceftazidime (loading dose, 4.4 mg/kg; infusion rate, 4.1 mg/kg/h) for 36 hours to 5 dogs.

Results—The MIC of ceftazidime for P aeruginosa was ≤ 8 µg/ml; all isolates were considered susceptible. Following SC administration of ceftazidime, mean β disappearance half-life was 0.8 hours, and mean serum ceftazidime concentration exceeded the MIC for P aeruginosa for only 4.3 hours. Two dogs had gastrointestinal tract effects. Mean serum ceftazidime concentration exceeded 16 µg/ml during continuous IV infusion. None of the dogs developed adverse effects.

Conclusions and Clinical Relevance—Administration of ceftazidime subcutaneously (30 mg/kg, q 4 h) or as a constant IV infusion (loading dose, 4.4 mg/kg; rate, 4.1 mg/kg/h) would maintain serum ceftazidime concentrations above the MIC determined for 101 clinical isolates of P aeruginosa. Use of these dosages may be appropriate for treatment of dogs with infections caused by P aeruginosa. (Am J Vet Res 2000;61:1204–1208)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To determine effects of prior feeding on pharmacokinetics and estimated bioavailability of orally administered microencapsulated erythromycin base (MEB) in healthy foals.

Animals—6 healthy foals, 3 to 5 months old.

Procedure—Foals were given 2 doses of MEB (25 mg/kg of body weight, PO). One dose was administered after food was withheld overnight, and the other was administered after foals had consumed hay. The study used a crossover design with a 2-week period between doses. Blood was collected via a jugular vein prior to and at specific times after drug administration. Concentrations of erythromycin A and anhydroerythromycin A in plasma were determined, using highperformance liquid chromatography. Results pharmacokinetic analysis of plasma concentration-time data for food-withheld and fed conditions were compared.

Results—Plasma concentrations of erythromycin A for foals were lower after feeding than concentrations when food was withheld. Area under the plasma concentration- time curve, maximum plasma concentration, and estimated bioavailability were greater in foals when food was withheld than when foals were fed. Anhydroerythromycin A was detected in plasma after administration of MEB in all foals.

Conclusions and Clinical Relevance—Foals should be given MEB before they are fed hay. Administration of MEB to foals from which food was withheld overnight apparently provides plasma concentrations of erythromycin A that exceed the minimum inhibitory concentration of Rhodococcus equi for approximately 5 hours. The dosage of 25 mg/kg every 8 hours, PO, appears appropriate. (Am J Vet Res 2000;61:1011–1015)

Full access
in American Journal of Veterinary Research

Abstract

Objective—To measure minimum inhibitory concentrations (MIC) of 17 antimicrobials for Escherichia coli isolates from a turkey operation and assess whether small samples provide precise estimates of geometric mean MIC.

Design—Prospective study.

Sample Population—105 clinical isolates from birds and 1,104 fecal isolates from 20 flocks (poults and finisher hens).

Procedure—A Mueller-Hinton broth dilution panel was used to measure MIC, and MIC of fecal and clinical isolates were compared. We drew random samples of 5, 10, 15, 20, 25, 30, 35, 40, and 45 isolates from each finisher flock and between 100 and 105 isolates from 5, 7, 10, and 20 flocks. Antimicrobial usage was determined for enrolled flocks.

Results—Six of 12 poult and 18 of 20 finisher flocks had been treated with antimicrobials, often for respiratory illnesses consistent with colibacillosis. All birds received gentamicin at the hatchery. More fecal than clinical isolates were resistant to ampicillin; however, more clinical isolates were resistant to ciprofloxacin, gentamicin, and sulfamethoxazole. Precise estimates of geometric mean MIC for flocks were obtained when ≥ 15 fecal isolates were obtained per flock and, for the operation, when 105 isolates were obtained from ≥ 7 flocks.

Conclusions and Clinical Relevance—Antimicrobial usage was common and may have contributed to the resistance patterns of isolates. With a modest allocation of laboratory resources, producers can monitor antimicrobial susceptibilities of clinical and fecal E coli to manage risks of antimicrobial usage and resistance. (J Am Vet Med Assoc 2002;221:411–416)

Full access
in Journal of the American Veterinary Medical Association

Abstract

Objective

To compare serum and skin concentrations of enrofloxacin in dogs with pyoderma with those of clinically normal dogs and to evaluate concentrations in dogs with superficial versus deep pyoderma.

Animals

16 clinically normal dogs and 16 dogs with pyoderma.

Procedure

Enrofloxacin (approx 5 mg/kg of body weight, PO) was administered daily to all dogs. Serum samples and skin biopsy specimens were obtained on day 1 at 3 hours after drug administration and on day 3 immediately before and 3 hours after drug administration. Samples and specimens were assayed by high-performance liquid chromatography. Morphometric analysis was performed on skin biopsy specimens to determine correlation between inflammatory cells and peak tissue enrofloxacin concentration on day 1.

Results

Morphometric analysis revealed high correlation between dermal inflammatory cell count and drug concentration in dogs with pyoderma.

Conclusions

At mean dosage of 5 mg/kg once daily, enrofloxacin tissue concentrations were significantly greater in dogs with pyoderma at 3 hours after pill administration. Enrofloxacin tissue concentration on day 3 at 3 hours after pill administration was 12.4 times the 90% minimum inhibitory concentration of enrofloxacin for Staphylococcus intermedius.

Clinical Relevance

In dogs with pyoderma, therapeutic tissue concentrations of enrofloxacin are reached as early as 3 hours after drug administration. (Am J Vet Res 1998;59:1599-1604)

Free access
in American Journal of Veterinary Research

Objective

To compare serum and skin concentrations of enrofloxacin in dogs with pyoderma with those of clinically normal dogs and to evaluate concentrations in dogs with superficial versus deep pyoderma.

Animals

16 clinically normal dogs and 16 dogs with pyoderma.

Procedure

Enrofloxacin (approx 5 mg/kg of body weight, PO) was administered daily to all dogs. Serum samples and skin biopsy specimens were obtained on day 1 at 3 hours after drug administration and on day 3 immediately before and 3 hours after drug administration. Samples and specimens were assayed by high-performance liquid chromatography. Morphometric analysis was performed on skin biopsy specimens to determine correlation between inflammatory cells and peak tissue enrofloxacin concentration on day 1.

Results

Morphometric analysis revealed high correlation between dermal inflammatory cell count and drug concentration in dogs with pyoderma.

Conclusions

At mean dosage of 5 mg/kg once daily, enrofloxacin tissue concentrations were significantly greater in dogs with pyoderma at 3 hours after pill administration. Enrofloxacin tissue concentration on day 3 at 3 hours after pill administration was 12.4 times the 90% minimum inhibitory concentration of enrofloxacin for Staphylococcus intermedius.

Clinical Relevance

In dogs with pyoderma, therapeutic tissue concentrations of enrofloxacin are reached as early as 3 hours after drug administration. (Am J Vet Res 1998;59:veterinary medicine-veterinary medicine)

Free access
in Journal of the American Veterinary Medical Association

Summary

To evaluate the efficacy of penicillin or penicillin and dexamethasone for treatment of infectious bovine keratoconjunctivitis, 6- to 8-month-old beef heifers with clinical signs of infectious bovine keratoconjunctivitis were randomly assigned to 1 of 3 treatment groups: penicillin only, penicillin and dexamethasone, or control. Cattle assigned to the penicillin group (n = 18) were treated with 3 daily subconjunctival injections of procaine penicillin G. Cattle assigned to the penicillin/ dexamethasone group (n = 13) were treated with 3 daily subconjunctival injections of procaine penicillin G and dexamethasone sodium phosphate. Control cattle (n = 14) were not treated. Healing times and frequency of recurrence for corneal ulcers; severity, diameter, and surface area measurements of corneal ulcers; and clinical scores did not differ among the 3 groups. Frequency of Moraxella bovis isolation from specimens of ocular secretions from ulcerated and nonulcerated eyes was similar in all groups. Minimum inhibitory concentration of penicillin G for 95 of the 102 tested M bovis isolates was 0.3 U/ml, and for 7 others was 0.03 U/ml. When first and last specimens from 42 of 45 calves with isolation of M bovis on serial microbial cultures were compared, the susceptibility of each last isolate was similar to that of the corresponding first isolate.

Free access
in Journal of the American Veterinary Medical Association

SUMMARY

Pharmacodynamic variables of enrofloxacin were investigated in a neutropenic mouse Escherichia coli and staphylococcal thigh infection model. Enrofloxacin pharmacokinetics in clinically normal mice and dogs were compared to confirm that doses evaluated in the mouse model would include enrofloxacin doses appropriate for use in dogs. Mice were made neutropenic by treatment with cyclophosphamide and injected in the thigh muscle with approximately 106 colony-forming units of E coli (n = 2) or a staphylococcal (n = 2) clinical isolate. Enrofloxacin dosages tested ranged from 0.78 to 50 mg/kg of body weight and 6.25 to 200 mg/kg in the E coli and staphylococcal infection trials, respectively. In each 24-hour dosage trial, enrofloxacin was administered SC as a single dose or in divided doses given every 3, 6, or 12 hours. Comparison of log10 colonyforming units per thigh muscle in untreated control mice and mice treated with enrofloxacin was used as a measure of efficacy. Two-way anova was used to determine that the enrofloxacin total dose, but not the dose frequency, was significant in determining drug efficacy. Pharmacokinetic values analyzed by use of multivariant stepwise linear regression analysis indicated that the area under the concentration-time curve, but not time above minimum inhibitory concentration, was significant in predicting efficacy of enrofloxacin treatment. We conclude that enrofloxacin killing of E coli and staphylococci is concentration dependent and not time dependent.

Free access
in American Journal of Veterinary Research

SUMMARY

Chronic Escherichia coli-associated prostatitis was induced in 16 dogs; 9 noninfected dogs served as controls; and all dogs were vasectomized. Two to 3 weeks after instillation of bacteria directly into the prostate, the urine or prostatic fluid or both from 13 of 16 dogs were culture positive. Enrofloxacin, a fluoroquinolone antimicrobial agent, was administered orally to all dogs during the third or fourth week after surgery, at a dosage of approximately 5 mg/kg of body weight, every 12 hours for 7 days. Serum and prostatic fluid concentrations of enrofloxacin were concurrently measured in all dogs on days 2, 4, and 6 at 2 hours after dosing. Serum and prostatic tissue concentrations of enrofloxacin were concurrently measured in all dogs on day 7, at 1.5, 3, 4.5, and 6 hours after dosing. When values for these samples were compared, using a two-factor anova, significant differences were not found. Use of this dosing regimen of enrofloxacin resulted in prostatic fluid and prostatic tissue concentrations exceeding the minimum inhibitory concentration of most pathogens that cause bacterial prostatitis. In addition, prostatic fluid-to-serum and prostatic tissue-to-serum concentration ratios were greater than 1.0.

Free access
in American Journal of Veterinary Research