Comparative pharmacokinetics of antifungal drugs in domestic turkeys, red-tailed hawks, broad-winged hawks, and great-horned owls

The present research was to test in vitro activity of thiabendazole, 5-fluorocytosine, and amphotericin B against 11 isolates of Aspergillus fumigatus from avian species. Additionally, the plasma concentrations of these drugs were determined in four avian species given a range of dosages by oral, intravenous, and intratracheal routes. Thiabendazole inhibited most isolates in vitro at concentrations between 25 and 50 micrograms/ml; however, there were no detectable inhibitory concentrations in the plasma of any species at any of the doses. The arithmetic mean minimum inhibitory in vitro concentration for 5-fluorocytosine against the 11 Aspergillus isolates was 2.73 micrograms/ml. Inhibitory concentrations of 5-fluorocytosine were found 2 and 6 hours post-administration in all species when given oral doses of 30 or 60 mg/kg as a single dose or when given three divided doses a day totaling 120 mg/kg. No inhibitory concentrations were found 24 hours post-administration. Inhibitory concentrations of amphotericin B were found only 2 and 6 hours post-administration in birds receiving three doses of 1.5 mg/kg at 2-hour intervals. The arithmetic mean minimum inhibitory in vitro concentration for amphotericin B against 11 isolates of A. fumigatus was 0.81 micrograms/ml.     

Clinical pharmacokinetics of amikacin in dogs

After IV, IM, and subcutaneous injection of single dosages of amikacin (5, 10, and 20 mg/kg of body weight) in each of 4 dogs, the elimination kinetics of amikacin were determined. The pattern of urinary excretion and cumulative amount excreted unchanged in 24 hours were also determined. Amikacin had a short half-life (approx 1 hour) that was independent of the dosage. Intravenous injection of 10 mg/kg gave apparent volume of distribution of 226 +/- 37 ml/kg and body clearance of 2.64 +/- 0.24 ml/min.kg (mean +/- SD, n = 4). Within 6 hours, greater than 90% of the antibiotic was excreted in the urine, regardless of the route of administration. For isolates of common bacterial species from the canine urinary tract, minimum inhibitory concentrations of amikacin, gentamicin, tobramycin, and kanamycin were determined in vitro. Cumulative percentages were approximately the same for urinary isolates of Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, and coagulase-positive staphylococci that were susceptible (minimum inhibitory concentrations less than or equal to 32 micrograms/ml) to increasing concentrations of amikacin, gentamicin, and tobramycin, in vitro. Klebsiella pneumoniae was significantly more susceptible to amikacin than were the other bacteria evaluated. Widest variations in susceptibility to aminoglycosides were found with urinary isolates of streptococcal species. For dogs with normal renal function, an amikacin dosage of 10 mg/kg (IM or subcutaneously) is recommended every 8 hours for treatment of systemic infections, and every 12 hours for treatment of urinary tract infections caused by susceptible bacteria.     

Pharmacokinetics of ceftazidime given alone and combination with probenecid to unweaned calves

Ceftazidime pharmacokinetic values were studied in unweaned calves given the antibiotic alone or in combination with probenecid. Ceftazidime was administered IV to 9 calves at a dosage of 10 mg/kg of body weight and IM (10 mg/kg) to 8 calves, to 7 calves (10 mg/kg plus probenecid [40 mg/kg]), and to 9 calves (10 mg/kg plus probenecid [80 mg/kg]). Serum concentration-vs-time data were analyzed, using noncompartmental methods based on statistical moment theory. The data for IV ceftazidime administration also were fitted by use of a linear, open 2-compartment model. The mean (+/- SD) terminal half-life was 138.7 +/- 23.6 minutes and 126.3 +/- 10.5 minutes after IV and IM administrations, respectively. The mean residence time was 167.3 +/- 21.1 minutes and 201.4 +/- 16.8 minutes after IV and IM administrations, respectively. Coadministeration of probenecid did not affect the terminal half-life or mean residence time values. The total body clearance was 1.75 +/- 0.26 ml/min/kg, and the volume of distribution at steady state was 0.294 +/- 0.064 L/kg. The estimated mean absorption time was 34.1 minutes. There were no significant differences between the mean residence time calculated by statistical moment theory or by compartmental analysis, indicating central compartment output of ceftazidime. The 90% minimal inhibitory concentration values of ceftazidime determined for Escherichia coli, Salmonella spp, Pasteurella multocida, and P haemolytica isolates ranged from less than 0.01 to 0.1 micrograms/ml.     

Antibacterial effect of bovine lactoferrin against udder pathogens

The antibacterial effect of lactoferrin (Lf) was tested on isolates of Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and coagulase-negative staphylococci (CNS) as well as on Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae), originally isolated from bovine mastitis. Concentrations of Lf used were 0.67 mg/ml, 1.67 mg/ml, and 2.67 mg/ml. Growth of udder pathogens was monitored by turbidometry either in broth culture or in whey prepared from normal milk. We focused on 3 different growth variables: lag time, slope, and maximum absorbance of bacterial growth curves. Growth inhibition was seen in the broth but hardly at all in whey. The isolates of E. coli and CNS did not grow sufficiently well in whey to draw any conclusions. The most effective inhibitory activity of Lf was seen against E. coli and P. aeruginosa. All 5 E. coil isolates had similar growth patterns. Inhibition of growth by Lf was concentration-dependent. The concentration of 0.67 mg/ml in broth and whey was generally too low for a significant inhibitory effect.     

Sensitivity of Chlamydia suis to cathelicidin peptides

Nine Chlamydia suis isolates, obtained from pigs with conjunctivitis, were molecularly characterized by ompA sequencing and their in vitro susceptibility to six cathelicidin peptides (SMAP-29, BAC-7, BMAP-27, BMAP-27, BMAP-28, PG-1, LL-37) determined in cell culture. SMAP-29 was the most active peptide, reducing the intracellular inclusion number by > or =50% at a concentration of 10 microg/ml (3 microM) in six of the nine isolates tested. Three molecularly identical isolates were insensitive at a concentration as high as 80 microg/ml (25 microM). Of the remaining cathelicidin peptides tested, BAC-7 and BMAP-27 were active against six C. suis isolates at a concentration of 80 microg/ml (25 and 26 microM, respectively). Cathelicidins LL-37 and PG-1 did not show any anti-chlamydial activity at 80 microg/ml.     

Clinical pharmacology of polymyxin B, colistin and colistimethate in young dairy calves

The in vitro sensitivity of 592 Gram-negative bacteria isolated from cattle against polymyxin B was determined by the agar plate dilution method. The minimal inhibitory concentration of polymyxin B for all but ten of the isolates was ≤ 2.0 μg/ml and 75% of the isolates were inhibited at 1.0 μg of polymyxin B/ml or less. Intramuscular injections of polymyxin B, colistin and colistimethate (CMS) were given to veal calves once daily for 3 days. Mean peak serum drug concentrations were observed within 0.5–1 h after treatment and were between 2.7 and 4.7 μg/ml when polymyxin B and colistin were administered at a dose rate of 2.5 mg/kg/day, and between 5.3 and 7.5 μg/ml at dose rate of 5.0 mg/kg/day. When CMS was given at 5.0 mg/kg/day mean peak drug concentration was 14.1 μg/ml. The elimination half-life ( t _1/2) of polymyxin B and colistin was 4–5 h but was approximately 2 h for CMS. Kidney function tests, using the double isotope single-injection method, were performed before and after the course of antibiotic treatment. No changes were detected in the glomerular filtration rate (GFR) or the effective renal plasma flow (ERPF) and blood urea levels were not raised following treatment. Several calves treated with the higher doses of polymyxin B and colistin exhibited transient ataxia and apathy 2–4 h after treatment but clinical signs suggesting interference with neurological function were not observed after an equivalent dose of CMS was administered.     

Probenecid effect on cefuroxime pharmacokinetics in calves

Cefuroxime pharmacokinetics were studied in unweaned calves. The antibiotic was administered at 10 mg/kg to six calves i.v., to 12 calves i.m. and to ten of the previous 12 calves i.m. at 10 mg/kg together with probenecid at 40 mg/kg. Intramuscular doses of cefuroxime alone at 20 mg/kg were given to seven calves; to five of these calves cefuroxime was also given together with probenecid at 40 mg/kg and at 80 mg/kg. The serum concentration-time data were analyzed using statistical moment theory (SMT). The elimination half-life (t1/2) was 69.2 min (harmonic mean) after i.v. and 64.8 min and 64.9 min following i.m. administration of the lower and higher dose, respectively. Co-administration of probenecid did not affect the t1/2. The mean residence time (MRT) was 80.9 +/- 23.5 min (mean +/- SD) after i.v. and 117.8 +/- 9.3 min and 117.7 +/- 5.4 min after i.m. administration of cefuroxime at 10 and 20 mg/kg, respectively. The MRTi.m. following administration of cefuroxime at 10 mg/kg together with probenecid at 40 mg/kg was 140.0 +/- 8.8 min. The MRTi.m. values were 132.8 +/- 2.3 min and 150.8 +/- 5.1 min after cefuroxime was given at 20 mg/kg together with probenecid at 40 mg/kg or 80 mg/kg, respectively. The total body clearance (ClT) was 3.56 +/- 1.11 ml/min/kg and the volume of distribution at steady state (Vd(ss] 0.270 +/- 0.051 l/kg. The MIC90 values of cefuroxime were 16 micrograms/ml for E. coli and Salmonella isolates, 0.5 microgram/ml for Pasteurella multocida and 2.0 micrograms/ml for P. haemolytica.     

POSITIVE-CONTRAST ARTHROGRAPHY

Normal colony Beagle dogs were used to evaluate the effect of concentration, volume, and limb positioning on positive-contrast arthrography in the humeral joint. An 8.4% w/v (33.3 mg/ml ± volume) concentration of analytic grade metrizamide (33 mg/ml of iodine) was thought to provide arthrograms of the highest diagnostic quality. Optimal volume of contrast medium was 2–4 ml in dogs with weight of 7.0–15.6 kg (mean, 10.3 kg). Radiographs thought to be of greatest diagnostic value were those made with the dog in lateral recumbency and the limb positioned for neutral, traction, flexion, supination, and pronation views, plus a caudocranial radiograph made with the dog in dorsal recumbency and the limb in traction.     

Absorption and Synthesis of Immunoglobulins G in Newborn Calves

Newborn calves (n=19) got 4.5 liters of pooled colostrum within three feedings in the first 14 hours post natum (p.n.). The immunoglobulin G1 (IgG1) and IgG2 concentrations in the colostrum pool were 54.9 mg/ml and 4.2 mg/ml. The precolostral serum IgG concentrations in calves were 0.15 mg/ml (IgG1; SD 0.24) and 0.06 mg/ml (IgG2; SD 0.14). The highest serum IgG levels p.n. were measured 12 hours after the first colostrum feeding (9.3 mg IgG1/ml (SD 4.0), 0.8 mg IgG1/ml (SD 1.0). Thereafter, the mean IgG1 level was reduced continuously to the significant lowest concentration of 4.9 mg/ml (SD 2.3) at day 28 p.n. and then increased continuously to the significant highest concentration of 9.0 mg/ml (SD 4.8) on day 77 p.n. The mean concentration of IgG2 was lowest on day 11 p.n. (0.5 mg/ml; SD 0.4) and highest on day 77 p.n. (1.2 mg/ml; SD 0.6).
In blood from 198 calves, housed in Germany and sampled between day 4 and 6 p.n., the IgG concentration averaged 4.9 mg/ml serum (SD 3.3). From 93 dams of these calves a sample of the first colostrum could be obtained showing a mean concentration of 22.0 mg IgG/ml (SD 11.0). IgG levels in the colostrum and in the serum showed a correlation of r=0.37.
In Kenia IgG levels of three week old calves from two farms were measured. The calves were always with mother for the first 24 hours. The mean serum IgG concentrations of the calves were 22.5 mg IgG/ml (n=7, SD 6.8) and 15.2 mg IgG/ml (n=15; SD 6.3). Comparing to the serum IgG levels found in calves of our studies in Germany there were significant differences.     

Penicillin G or ampicillin for oral treatment of canine urinary tract infections.

Penicillin G or ampicillin was administered orally to 144 dogs with urinary tract infections. The daily dosage of penicillin G ranged from 110,000 to 165,000 U/kg (50,000-75,000 U/lb), and the dosage of ampicillin varied from 77 to 110 mg/kg (35-50 mg/lb). The daily dose of each antibiotic was divided into 3 or 4 doses and given at approximately 8- or 6-hour intervals for 10 to 14 days. Response to treatment, based on results of urine culture, varied from no response for infections caused by Pseudomonas spp to 100% response for those caused by Staphylococcus aureus and Streptococcus spp. About 50% of infections caused by Escherichia coli were eliminated, as were about 80% of those due to Proteus mirabilis. Mean concentrations of penicillin G and ampicillin in urines collected at 6-hour intervals after oral administration to clinically normal adult dogs were approximately 350 microgram/ml for both drugs when each was given individually in daily dosages (divided QID) of 55 mg/kg (25 mg/lb). The minimum inhibitory concentration of penicillin G for a number of the bacteria isolated from the urine of the infected dogs was compared with the results of the clinical trials and to the minimum inhibitory concentration of a larger number of urinary bacterial isolates.     

Pharmacokinetics of florfenicol in the plasma of Japanese quail

Abstract

AIM: To determine the pharmacokinetics and bioavailability of florfenicol in the plasma of healthy Japanese quail (Coturnix japonica).

METHODS: Sixty-five quail were given an I/V and I/M dose of florfenicol at 30 mg/kg bodyweight (BW). A two-period sequential design was used, with a wash-out period of 2 weeks between the different routes of administration. Concentrations of florfenicol in plasma were determined using high-performance liquid chromatography (HPLC).

RESULTS: A naíve pooled data analysis approach for the plasma concentration-time profile of florfenicol was found to fit a non-compartmental open model. After I/V administration, the mean residence time (MRT), mean volume of distribution at steady state (V_ss), and total body clearance of florfenicol were 12.0 (SD 0.37) h, 8.7 (SD 0.22) L/kg, and 1.3 (SD 0.08) L/h/kg, respectively. After I/M injection, the MRT, mean absorption time (MAT), and bioavailability were 12.3 (SD 0.37) h, 0.2 (SD 0.02) h, and 79.1 (SD 1.79)%, respectively.

CONCLUSIONS: The time for the concentration of florfenicol to fall below the probable effective concentration of 1 µg/ml of approximately 10 h is sufficient for the minimum inhibitory concentration needed for many bacterial isolates. Further pharm acodynamic studies in quail are needed to evaluate a suitable dosage regimen.     

Disposition of orally administered cefpodoxime proxetil in foals and adult horses and minimum inhibitory concentration of the drug against common bacterial pathogens of horses

OBJECTIVES: To determine the disposition of orally administered cefpodoxime proxetil in foals and adult horses and measure the minimum inhibitory concentrations (MICs) of the drug against common bacterial pathogens of horses. ANIMALS: 6 healthy adult horses and 6 healthy foals at 7 to 14 days of age and again at 3 to 4 months of age. PROCEDURE: A single dose of cefpodoxime proxetil oral suspension was administered (10 mg/kg) to each horse by use of a nasogastric tube. In 7- to 14-day-old foals, 5 additional doses were administered intragastrically at 12-hour intervals. The MIC of cefpodoxime for each of 173 bacterial isolates was determined by use of a commercially available test. RESULTS: In 7- to 14-day-old foals, mean +/- SD time to peak serum concentration (Tmax) was 1.7 +/- 0.7 hours, maximum serum concentration (Cmax) was 0.81 +/- 0.22 microg/mL, and elimination half-life (harmonic mean) was 7.2 hours. Disposition of cefpodoxime in 3- to 4-month-old foals was not significantly different from that of neonates. Adult horses had significantly higher Cmax and significantly lower Tmax, compared with values for foals. The MIC of cefpodoxime required to inhibit growth of 90% of isolates for Salmonella enterica, Escherichia coli, Pasteurella spp, Klebsiella spp, and beta-hemolytic streptococci was 0.38, 1.00, 0.16, 0.19, and 0.09 microg/mL, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Oral administration at a dosage of 10 mg/kg every 6 to 12 hours would appear appropriate for the treatment of equine neonates with bacterial infections.     

Pharmacokinetics of ceftazidime in dogs following subcutaneous administration and continuous infusion and the association with in vitro susceptibility of Pseudomonas aeruginosa

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 < or = 8 microg/ml; all isolates were considered susceptible. Following SC administration of ceftazidime, mean beta 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 microg/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.     

Florfenicol in non-lactating dairy cows: pharmacokinetics, binding to plasma proteins, and effects on phagocytosis by blood neutrophils

Serial blood samples were collected and plasma concentrations of florfenicol (FLO) were measured following the administration of an intravenous bolus of 50 mg/kg FLO to five healthy non-lactating dairy cows. A triexponential equation provided the best fit of the data for four of the five cows. The mean value for beta corresponded to a half-life of 3.2 h. The mean apparent volume of distribution was 0.67 l/kg, and the mean body clearance was 0.15 l/kg/h. The extent of binding of FLO to bovine plasma proteins was determined in vitro at concentrations of 5 micrograms/ml and 50 micrograms/ml by equilibrium dialysis and ultrafiltration. The drug was 18% and 19% bound by equilibrium dialysis, and 23% and 19% bound by ultrafiltration, at 5 micrograms/ml and 50 micrograms/ml, respectively. Phagocytosis of 32phosphorus-labelled Staphylococcus aureus by bovine blood neutrophils was compared in vitro between neutrophils incubated in phosphate-buffered saline alone or in combination with 5, 125, or 1000 micrograms/ml chloramphenicol or FLO. There was no significant effect of chloramphenicol at any concentration. Florfenicol significantly inhibited phagocytosis at all concentrations, but the percentage inhibition was small. The clinical significance, if any, of this effect of FLO remains to be demonstrated.     

Twenty-four hour urinary protein loss in healthy cats and the urinary protein-creatinine ratio as an estimate

Urinary protein loss was determined in 12 healthy cats. Voided urine was collected and protein quantitated by the Coomassie blue method. Mean protein loss for all cats was 12.65 mg/kg/24 h (5.45 SD). Protein loss for male cats (n = 6) was 16.62 mg/kg/24 h (3.3 SD), which was significantly different (P less than 0.01) from 8.69 mg/kg/24 h (4.09 SD) for females (n = 6). A single urine protein-creatinine ratio correlated well with the total urinary protein loss in mg/kg/24 h. The correlation coefficient for the protein-creatinine ratio in voided urine (UPCV) vs 24-hour urinary protein (UP-24) loss was 0.968, and that for the protein-creatinine ratio in urine obtained by cystocentesis (UPCC) vs UP-24 was 0.945. The regression equations were UPCV = 0.02145 + 0.02338 x UP-24 (mg/kg), and UPCC = 0.02667 + 0.02133 x UP-24 (mg/kg). Using the mean value plus 3 SD of urinary protein loss from the healthy cats in this study, a healthy cat would be expected to have a urinary protein loss of less than 29 mg/kg/24 h. A protein-creatinine ratio from a single urine sample provides an accurate estimate of urinary protein loss in healthy cats.     

Failure of passive immunoglobulin transfer: a major determinant of mortality in newborn alpacas (Lama pacos)

Failure of passive transfer (FPT) of immunoglobulin from colostrum was demonstrated as a major determinant of mortality in newborn alpacas (Lama pacos; crias). Serum IgG concentrations of dying crias were significantly (P less than 0.0001) lower than were serum IgG concentrations of crias that lived. Of 82 crias, 10 (12%) died within 1 month of age, and 7 of these had 0 to 9 mg of IgG/ml of serum at 48 hours after birth; 5 of the 7 had evidence of infectious diseases. The serum IgG concentrations of the remaining dead crias were 12, 13, and 20 mg/ml. On the basis of serum IgG concentrations of crias that died in the first month, FPT was defined as a 48-hour serum IgG concentration less than 9 mg/ml, which was greater than 2 SD below the 48-hour mean of clinically normal crias. Using this definition, the prevalence of FPT in the 82 crias studied was 9%. Corroborative evidence of the relationship between FPT and mortality was obtained from a retrospective study of 21 dead crias. The postmortem serum IgG concentration of 5 crias that died 2 to 10 days after birth ranged from less than 1 to 3 mg/ml; all were greater than 2 SD below the mean of age matched clinically normal crias. The range of serum IgG concentration was 2.2 to 21 mg/ml in 8 crias that died 11 to 20 days after birth; serum IgG concentration in 1 cria was greater than 2 SD below the normal mean, and 6 were greater than 1 SD below the normal mean.(ABSTRACT TRUNCATED AT 250 WORDS)     

In vitro antimicrobial activity against 10 North American and European Lawsonia intracellularis isolates

The objective of this study was to determine the in vitro minimum inhibitory concentration (MIC) of antimicrobials against 10 isolates of Lawsonia intracellularis, the etiological agent of proliferative enteropathy (PE). Antimicrobials tested included carbadox, chlortetracycline, lincomycin, tiamulin, tylosin and valnemulin. The MIC of each antimicrobial against L. intracellularis was determined using a tissue culture system and was identified as the lowest concentration that inhibited 99% of L. intracellularis growth, as compared to the antimicrobial-free control. Each antimicrobial concentration was evaluated for both intracellular and extracellular activity against L. intracellularis, an obligately intracellular bacterium. When tested for intracellular activity, carbadox, tiamulin, and valnemulin were the most active antimicrobials with MICs of < or =0.5microg/ml. Tylosin (MICs ranging from 0.25 to 32microg/ml) and chlortetracycline (MICs ranging from 0.125 to 64microg/ml) showed intermediate activities and lincomycin (MICs ranging from 8 to >128mIcog/ml) showed the least activity. When tested for extracellular activity, valnemulin (MICs ranging from 0.125 to 4microg/ml) was the most active against most L. intracellularis isolates. Chlortetracycline (MICs ranging from 16 to 64microg/ml), tylosin (MICs ranging from 1 to >128microg/ml), and tiamulin (MICs ranging from 1 to 32microg/ml) showed intermediate activities. Lincomycin (MICs ranging from 32 to >128microg/ml) showed the least activity. Our in vitro results showed that each L. intracellularis isolate had a different antimicrobial sensitivity pattern and these data can be utilized as an in vitro guideline for the further antimicrobial evaluation of field L. intracellularis isolates.     

UROCYSTOLITH DETECTION: COMPARISON OF SURVEY, CONTRAST RADIOGRAPHIC AND ULTRASONOGRAPHIC TECHNIQUES IN AN IN VITRO BLADDER PHANTOM

Urocystoliths of 9 mineral types from 437 canine patients submitted to the University of Minnesota Urolith Bank were imaged in a urinary bladder phantom. Imaging techniques simulated were survey radiography, pneumocystography, double contrast cystography (two iodine concentrations) and real-time ultrasonography (3.5 MHz, 5.0 MHz, 7.5 MHz). Imaging techniques were compared for accuracy of urocystolith detection, accuracy of urocystolith enumeration, and tendencies for over or undercounting. Across urocystolith mineral types, the false negative rates (no urocystoliths detected in a given case) for survey radiographs range from 2 to 27%. Pneumocystographic techniques are one-half as likely to yield false negative results as are survey radiographic techniques. Underestimates of urocystolith numbers and false negatives are likely using 80 mg iodine/ml double contrast cystography because calcium-based urocystoliths are isopaque in this contrast medium dilution. The 200 mg iodine/ml double contrast cystographic techniques are unlikely to yield false negative diagnoses even for very small (< or = 1.0 mm) urocystoliths and is comparable to pneumocystography for detection and slightly better for enumeration. The likelihood of an ultrasonographic false negative for urocystoliths decreases with increasing MHz. Under optimal conditions using a 7.5 MHz mechanical sector transducer, the false negative rates were comparable to double contrast cystography, but rates increased notably with lower MHz transducers.     

Gentamicin for treatment of resistant urinary tract infections in dogs.

Gentamicin was administered parenterally for 6 days to 43 dogs with urinary tract infections. The daily dosage of 6.6 mg/kg (3 mg/lb) was divided into equal parts and given IM or SC at 8-hour intervals. Dogs selected for treatment with gentamicin had urinary infections that had not responded to treatment with other antimicrobial agents or had bacterial isolates from urine that were resistant to several antimicrobial agents on in vitro susceptibility tests. Response to treatment, defined as negative urine culture on the last day of therapy or 4 to 14 days after completion of the therapeutic course, included 20 of 22 (91%) infections caused by Escherichia coli, 8 of 9 (89%) infections caused by Kebsiella pneumoniae, 6 of 7 (86%) infections caused by Proteus spp, and 6 of 7 infections caused by Pseudomonas spp. These four species comprised 84% of the bacteria isolated from the dogs in this study.     

Apramycin: minimal inhibitory concentrations for avian Escherichia coli and serum levels after intramuscular injection in turkeys

The minimal inhibitory concentrations (MIC) of apramycin, a unique aminocyclitol antibiotic, for 100 Escherichia coli isolates recovered from clinical cases of avian colibacillosis were determined using the agar dilution method. All isolates were inhibited at apramycin concentration of 8.0 micrograms/ml; 90 and 50% of the isolates were inhibited at 6.6 and 3.4 micrograms/ml, respectively. A commercial injectable product containing 200 mg apramycin/ml was administered intramuscularly (i.m.) to groups of 6- and 12-week-old turkeys at 10, 15 and 20 mg/kg. Apramycin was quickly absorbed from the i.m. injection site. Mean peak serum drug concentrations were reached 1 h after treatment and were 19.5, 27.5 and 36.0 micrograms/ml, respectively. The serum elimination half-life (t 1/2) of the drug ranged between 1.75 h for the 10 mg/kg dose and 2.5 h for the 20 mg/kg dose. Very low concentrations of the drug were found 24 h after treatment. Duration of serum apramycin concentrations in relation to the MIC, dose, and age of birds was determined.