Search Results
You are looking at 1 - 9 of 9 items for
- Author or Editor: Robert D. Walker x
- Refine by Access: All Content x
Summary
Enrofloxacin was administered orally to 6 healthy dogs at dosages of approximately 2.75, 5.5, and 11 mg/kg of body weight, every 12 hours for 4 days, with a 4-week interval between dosage regimens. Serum and tissue cage fluid (tcf) concentrations of enrofloxacin were measured after the first and seventh treatments. The mean peak serum concentration occurred between 1 and 2.5 hours after dosing. Peak serum concentrations increased with increases in dosage. For each dosage regimen, there was an accumulation of enrofloxacin between the first and seventh treatment, as demonstrated by a significant (P = 0.001) increase in peak serum concentrations. The serum elimination half-life increased from 3.39 hours for the 2.75 mg/kg dosage to 4.94 hours for the 11 mg/kg dosage. Enrofloxacin accumulated slowly into tcf, with peak concentrations being approximately 58% of those of serum. The time of peak tcf concentrations occurred between 3.8 hours and 5.9 hours after drug administration, depending on the dosage and whether it was after single or multiple administrations. Compared with serum concentrations (area under the curve tcf /area under the curveserum), the percentage of enrofloxacin penetration into tcf was 85% at a dosage of 2.75 mg/kg, 83% at a dosage of 5.5 mg/kg, and 88% at a dosage of 11 mg/kg. All 3 dosage regimens of enrofloxacin induced continuous serum and tcf concentrations greater than the minimal concentration required to inhibit 90% (mic 90) of the aerobic and facultative anaerobic clinical isolates tested, except Pseudomonas aeruginosa. Only the 11 mg/kg dosage regimen provided continuous serum and tcf concentrations that exceeded the mic 90 for P aeruginosa isolates; whereas none of the dosages induced serum or tcf concentrations greater than the mic 90 of the obligate anaerobic bacteria tested.
SUMMARY
Serum retinol, retinyl palmitate, and total vitamin A concentrations, and jejunoileal morphology were examined in neonatal calves infected with Cryptosporidium parvum. Group-1 calves served as noninfected controls and, after an adjustment period, were given 50 ml of saline solution iv every 12 hours for 6 days. Group-2 calves were inoculated with 107 C parvum oocysts and, after the onset of diarrhea, were given 50 ml of saline solution iv every 12 hours for 6 days. Group-3 calves were inoculated with 107 C parvum oocysts and, after the onset of diarrhea, were treated with difluoromethylornithine (dfmo, 200 mg/kg of body weight iv, q 12 h) for 6 days. Group-4 calves were naturally infected with C parvum. Jejunoileal biopsy specimens were excised from calves of groups 1-3 at 3 and again at 15 to 16 days of age. During the course of diarrhea and 3 days after saline or dfmo administration, water-miscible retinyl palmitate was administered orally (2,750 μg/kg) to each calf in each group. Cryptosporidium parvum infection was associated with significant (P ≤ 0.05) reduction in postadministration serum retinol, retinyl palmitate, and total vitamin A concentrations in calves of groups 2, 3, and 4. Cryptosporidium parvum infection caused significant (P ≤ 0.05) reduction in villus height. Decreased villus height, villus blunting and fusion, and attenuation of the intestinal mucosa were associated with reduced absorption of vitamin A, as indicated by lower peak postadministration retinyl palmitate concentration in C parvum-infected calves. Intravenous administration of dfmo to group-3 calves did not improve retinol absorption. Vitamin A should be provided parenterally to young calves with enteric cryptosporidiosis in an attempt to avoid depletion of concurrent low liver vitamin A reserves.
Abstract
Objective—To determine sources of Salmonella organisms in a veterinary teaching hospital, compare bacterial culture with polymerase chain reaction (PCR) testing for detection of Salmonella organisms in environmental samples, and evaluate the effects of various disinfectants on detection of Salmonella organisms on surface materials.
Design—Prospective study.
Sample Population—Fecal samples from 638 hospitalized horses and 783 environmental samples.
Procedure—Standard bacterial culture techniques were used; the PCR test amplified a segment of the Salmonella DNA. Five disinfectants were mixed with Salmonella suspensions, and bacterial culture was performed. Swab samples were collected from 7 surface materials after inoculation of the surfaces with Salmonella Typhimurium, with or without addition of a disinfectant, and submitted for bacterial culture and PCR testing.
Results—Salmonella organisms were detected in fecal samples from 35 (5.5%) horses. For environmental samples, the proportion of positive bacterial culture results (1/783) was significantly less than the proportion of positive PCR test results (110/783), probably because of detection of nonviable DNA by the PCR test. Detection of Salmonella organisms varied with the surface material tested, the method of detection (bacterial culture vs PCR testing), and the presence and type of disinfectant.
Conclusions and Clinical Relevance—Results of the present study suggested that Salmonella organisms can be isolated from feces of hospitalized horses and a variety of environmental surfaces in a large animal hospital. Although recovery of Salmonella organisms was affected by surface material and disinfectant, bleach was the most effective disinfectant on the largest number of surfaces tested. (J Am Vet Med Assoc 2001;218:1145–1151)
SUMMARY
Once-daily administration of aminoglycosides may be a safe and effective therapeutic regimen, on the basis of the microbiologic and pharmacokinetic characteristics of these antibiotics. This study was designed to determine serum and tissue concentrations following IV administration of gentamicin, at dosages of 6.6 mg/kg of body weight, every 24 hours, and 2.2 mg/kg, every 8 hours, for 10 days in adult horses. Nephrotoxicosis from these dosage regimens also was compared, and microbiologic effects, including postantibiotic effects, were determined with various concentrations of gentamicin against an equine clinical isolate of Pseudomonas aeruginosa. Treatment at the 6.6-mg/kg dosage resulted in maximal serum concentrations (77.93 ± 19.90 μg/ml, mean ± sem) and area under the concentration-vs-time curves (83.79 ± 14.97 μg.h/ml) that were significantly (P < 0.05) greater than those following treatment at the 2.2-mg/kg dosage (5.05 ± 0.50 μg/ml and 6.03 ± 0.66 μg.h/ml, respectively). Nephrotoxicosis was not induced with either dosage regimen, and postantibiotic effects were prolonged with a higher gentamicin concentration. This study provided evidence to support the use of once-daily gentamicin treatment in adult horses.
Summary
Ciprofloxacin, a fluoroquinolone antimicrobial agent, was administered orally to 4 healthy dogs at dosage of approximately 11 and 23 mg/kg of body weight, every 12 hours for 4 days, with a 4-week interval between dosing regimens. Serum and tissue cage fluid (tcf) concentrations of ciprofloxacin were measured after the first and seventh dose of each dosing regimen. The peak concentration was greatest in the serum after multiple doses of 23 mg/kg (mean ± sem; 5.68 ± 0.54 μg/ml) and least in the tcf after a single dose of 11 mg/kg (0.43 ± 0.54 μg/ml). The time to peak concentration was not influenced by multiple dosing or drug dose, but was longer for tcf (6.41 ± 0.52 hour) than for serum (1.53 ± 0.52 hour). Accumulation of ciprofloxacin was reflected by the area under the concentration curve from 0 to 12 hours after administration (AUC0→12). The AUC0→12 was greatest in the serum after multiple doses of 23 mg/kg (31.95 ± 1.90 μg·h/ml) and least in the tcf after a single dose of 11 mg/kg (3.87 ± 1.90 μg·h/ml). The elimination half-life was not influenced by multiple dosing or dose concentration, but was greater for tcf (14.59 ± 1.91 hours) than for serum (5.14 ± 1.91 hours). The percentage of tcf penetration (AUCTCF/AUCserum ) was greater after multiple doses (95.76 ± 6.79%) than after a single dose (55.55 ± 6.79%) and was not different between doses of 11 and 23 mg/kg. Both dosing regimens of ciprofloxacin resulted in continuous serum and tcf concentrations > 90% of the minimal inhibitory concentration for the aerobic and facultative anaerobic clinical isolates tested, including Pseudomonas aeruginosa.
