Inhalation anesthesia induced by isoflurane alters penicillin disposition in swine tissues

Twelve healthy swine were dosed with penicillin G intramuscularly. Fluids and tissues samples were collected at the end of two periods of general anesthesia, performed 24 h apart. Tissue samples were collected by minimally invasive laparoscopy under general anesthesia at 8 and 28 h postdose. Four nonanesthetized, penicillin-treated pigs were euthanized at 8 h postdose, and a second set of four similarly treated control pigs were sacrificed 28 h postdose. Liver penicillin tissue concentrations from animals that underwent anesthesia and laparoscopic tissue collection had tissue concentrations that were higher than nonanesthetized pigs at both time points. Urine, plasma, kidney, skeletal, and cardiac muscle showed no differences between the two groups. Laparoscopic tissue collection under general anesthesia in swine induces physiological changes that cause alterations in tissue pharmacokinetics not seen in conscious animals.

Plasma pharmacokinetics of ceftiofur metabolite desfuroylceftiofur cysteine disulfide in holstein steers: application of nonlinear mixed-effects modeling

Eight clinically normal and drug-naïve Holstein steers were dosed with ceftiofur sodium at 2.2 mg/kg body weight intramuscularly. Doses were given at 24-h intervals for 5 days. Prior to the first dose and after all injections, blood samples were collected serially for determination of plasma concentrations of one of ceftiofur's main metabolites, desfuroylceftiofur cysteine disulfide (DCCD). A nonlinear mixed-effect model was used to analyze the plasma concentration data. A stochastic approximation expectation maximization (SAEM) algorithm in MONOLIX version 4.2.2 was used to approximate the likelihood of the nonlinear mixed-effect model and to estimate the population parameters. In addition, simulation studies were conducted to justify the model and demonstrate how to interpret the model parameters given different scenarios.

Detection and survival of Toxoplasma gondii in milk and cheese from experimentally infected goats

The consumption of unpasteurized goat cheese and goat's milk has been suggested as a risk factor for toxoplasmosis in humans. In the present study, detection and survival of Toxoplasma gondii in milk and cheese was studied by bioassay in mice (milk) and in cats (cheese). Eight goats were inoculated orally with 300 to 10,000 oocysts of T. gondii strain TgGoatUS26. Milk samples were collected daily up to 30 days postinoculation and bioassayed in mice and cats. For mouse bioassay, 50 ml of milk samples were centrifuged, and the sediment was inoculated subcutaneously into mice. Mice were tested for T. gondii infection by seroconversion and by the demonstration of parasites. By mouse bioassay, T. gondii was detected in milk from all eight goats. The T. gondii excretion in milk was intermittent. For cat bioassay, 400 ml (100 ml or more from each goat) of milk from four goats from 6 to 27 days postinoculation were pooled daily, and cheese was made using rennin. Ten grams of cheese was fed daily to four cats, and cat feces were examined for oocyst shedding. One cat fed cheese shed oocysts 7 to 11 days after consuming cheese. Attempts were made to detect T. gondii DNA in milk of four goats; T. gondii was detected by PCR more consistently, but there was no correlation between detection of viable T. gondii by bioassay in mice and T. gondii DNA by PCR. Results indicate that T. gondii can be excreted in goat's milk and can survive in fresh cheese made by cold-enzyme treatment. To prevent transmission to humans or animals, milk should not be consumed raw. Raw fresh goat cheese made by cold-enzyme treatment of unpasteurized milk also should not be consumed.

Bovine kidney tissue/biological fluid correlation for penicillin

Penicillin is one of the most commonly misused drugs in steers and dairy cows. In the US, at slaughter the tolerance is 50 ng/g in kidney and other edible tissues. If the tolerance is exceeded, the carcass may not be used for human food. A preslaughter test for penicillin in an easily accessible biological fluid is needed to predict if the concentration of penicillin is below tolerance in the kidney before the bovine is slaughtered. In this study, 12 steers were injected three times with the approved dose (7000 IU) of penicillin at 12-h intervals. Blood and urine samples were collected at intervals after the final dose of penicillin. At each sampling point, one kidney biopsy sample was collected by laparoscopic surgery in the live animal. Another kidney sample was collected at slaughter. Correlations between plasma and kidney concentrations and between urine and kidney concentrations were determined. These correlations predict with 95% confidence that 99% of the animals will have kidney tissue below penicillin tolerance when the plasma concentration of penicillin is below 0.4 ng/mL and/or the urine penicillin concentration is below 140 ng/mL.

Use of tissue-fluid correlations to estimate gentamicin residues in kidney tissue of Holstein steers

Gentamicin continues to be one of the most effective antibiotics for the treatment of gram-negative infections. Greater than 90% of the drug is rapidly eliminated from the body in <2 days, however, a small residue remains bound to the kidney cortex tissue for many months. In beef steers, the gentamicin residue is unacceptable and its presence is monitored by the FAST (Fast Antimicrobial Screen Test) applied to the kidney at the time of slaughter. The sensitivity of the FAST to gentamicin in the kidney cortex is reported to be 100 ng/g, therefore, this level of gentamicin defines the acceptable limit of gentamicin drug residue in the bovine kidney. In the present study, three doses of 4 mg/kg gentamicin was administered intramuscularly to eight steers. Gentamicin was allowed to deplete from the kidneys for a range of times from 7 to 10 months. At slaughter the level of gentamicin in the kidney cortex varied from 91 to 193 ng/g, but a total of 160 FAST tests performed on the kidneys were negative. Blood and urine samples were collected at varying times following the last dose of gentamicin. Kidney tissue samples were collected by laparoscopic surgery in the live steers as well as the final sample obtained at slaughter. Plasma levels of gentamicin declined rapidly to nondetectable within 3 days, while measurable urine persisted for 75 days before the concentration of gentamicin declined to levels too low to quantitate by the available liquid chromatography tandem mass spectrometry (LC/MS/MS) technique. An estimated correlation between an extrapolation of urine gentamicin concentration to the corresponding kidney tissue sample suggests a urine to kidney tissue relationship of 1:100. A test system sufficiently sensitive to a urine gentamicin concentration of 1 ng/mL will correlate with the estimated 100 ng/g gentamicin limit of the FAST applied to the fresh kidney of the recently slaughtered bovine.

Cytological and microbiological findings in guttural pouch lavages of clinically normal horses with head restraint

OBJECTIVE

To evaluate the cytological and microbiological contents of guttural pouch washes of ten randomly selected horses restrained so as to prevent them lowering their heads, and to assess the possible effects on the guttural pouch environment in these horses.

PROCEDURE

Cytological and microbiological studies were performed on guttural pouch washes of ten clinically normal horses restrained in a standing position so as to prevent them from lowering their heads below normal, as would happen during transportation on long journeys. They were restrained for 12 or 24 h and cytological, bacteriological and mycological findings in guttural pouch washes were recorded.

RESULTS

The cytological gradings and neutrophil concentrations of guttural pouch washings were higher in horses that had their heads restrained for a longer period. Washings from these horses were more likely to contain cultivable bacteria and were the only washes yielding potentially pathogenic bacterial species.

CONCLUSION

Variation in the cytological differential counts and bacterial cultures of guttural pouch lavages may be found in clinically normal horses which have had their heads restrained in an elevated position for periods from 12 to 24 h. This should be considered when examining this site and care must be taken when interpreting cytology of guttural pouch lavages in samples taken after transportation for more than 12 h. Restriction of head movement could also affect the normal pouch enviroment and predispose it to disease.

Cytological and bacteriological findings in guttural pouch lavages of clinically normal horses

Percutaneous washes of the guttural pouches were obtained from two groups of 15 clinically normal horses, one lightly exercised and the other heavily exercised. Microbiological and cytological studies showed a wide variation in the differential cell counts. The cytological pattern of the normal lavages (< 5 per cent neutrophils) was characterised by a large proportion of ciliated columnar epithelial cells, a few non-ciliated cuboidal epithelial cells, and less than 1 per cent monocytes, lymphocytes, and eosinophils. Abnormal lavages (with more than 5 per cent neutrophils) had higher levels of bacterial growth than normal lavages. There were significant differences between the bacterial growth and total cell count, and also between the neutrophil contents of the lavages from the two groups of horses.