Production of patulin and citrinin by Penicillium expansum from British Columbia (Canada) apples.

Twenty-four isolates of Penicillium expansum Link from British Columbia (Canada) apples were cultured in yeast-extract sucrose (YES) at 25°C for 28 days to investigate production of patulin and citrinin. These isolates proved to be potent producers of citrinin, patulin, or in most cases, both mycotoxins. In every isolate, citrinin, patulin, or both compounds were produced at levels as high as 565 µg/mL (mean 269 µg/mL) and 100 µg/mL (mean 31 µg/mL), respectively. Of the 24 isolates, 4 produced citrinin only, and 2 produced patulin only. Overall, 83% of the isolates formed patulin and 91% formed citrinin. YES broth proved to be an effective medium for patulin and citrinin production. Other workers have noted that production of these mycotoxins in culture often presages production in fruits, so these results might help Canadian fruit processors evaluate and minimize mycotoxin levels in their products.

In vitro antibacterial activity of enrofloxacin and ciprofloxacin in combination against Escherichia coli and staphylococcal clinical isolates from dogs.

The objective of the study was to determine the in vitro interaction between enrofloxacin and ciprofloxacin against Escherichia coli and staphylococcal isolates from dogs. The microdilution checkerboard assay was used to determine the interaction of the drugs against 50 E. coli and 50 beta-haemolytic staphylococcal clinical isolates. The checkerboard assay revealed that the activity of enrofloxacin and ciprofloxacin was additive against E. coli and staphylococcal clinical isolates. It was concluded that for bacterial species against which ciprofloxacin is more potent than enrofloxacin, the in vivo transformation of enrofloxacin to ciprofloxacin may enhance the efficacy of enrofloxacin, if additivity of the drugs is confirmed in vivo.

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.

Comparison of amikacin dosing regimens in neutropenic guinea pigs with Escherichia coli infection.

OBJECTIVE: To derive pharmacokinetic data for 3 amikacin dosing regimens in guinea pigs and to determine whether the antibacterial activity of 15 mg/kg of body weight given twice daily is equivalent to administering the drug more frequently. ANIMALS: 10 guinea pigs in pharmacokinetic trials, and 10 guinea pigs in pretreatment, control, and amikacin treatment groups. PROCEDURE: Amikacin pharmacokinetic data were determined in guinea pigs after single i.m. administration of 3.75, 7.5 and 15 mg/kg. Guinea pigs had been made neutropenic by treatment with cyclophosphamide. All guinea pigs were inoculated with 2.8 x 10(8) colony-forming units (CFU) of Escherichia coli in the thigh muscle, then were allotted to 5 groups: pretreatment (euthanized 4 hours after inoculation), control, and 3 amikacin treatment groups (3.75 mg/kg, q 3 h; 7.5 mg/kg, q 6 h; and 15 mg/kg, q 12 h). Amikacin administration was begun 4 hours after E coli inoculation and was continued for 72 hours. Numbers of E coli CFU in infected thigh muscle were determined for each guinea pig. RESULTS: Difference in survival between control and the amikacin-treated groups was significant. The E coli infection concentration (log10 CFU) increased significantly in the control, compared with the pretreatment, group. Infection concentration decreased significantly in all treatment groups, compared with the pretreatment group. There was no significant difference in bacterial killing among the 3 treatment groups. CONCLUSION: Amikacin had a significant effect on survival of neutropenic guinea pigs with E coli infection. Antibacterial activity did not differ among 3 doses of amikacin administered at different intervals. CLINICAL RELEVANCE: Aminoglycoside dosing regimen with high peak concentration and long drug-free interval is as efficacious as divided dose regimens.

Bacterial killing by use of once daily gentamicin dosage in guinea pigs with Escherichia coli infection.

OBJECTIVE: To determine whether the antibacterial activity of 6 mg of gentamicin/kg of body weight given SC once daily, is equivalent to the standard gentamicin dose of 2 mg/kg given SC every 8 hours. ANIMALS: Guinea pigs with infected thigh wound: 5 in an untreated control group and 12 in 6 and 2 mg/kg gentamicin treatment groups. PROCEDURE: Guinea pigs were inoculated with 10(9) Escherichia coli in the thigh muscle. Gentamicin treatment (2 mg/kg, SC, q 8 h or 6 mg/kg, SC, q 24 h) was begun 4 hours after E coli inoculation and continued for 72 hours. Four hours after the last gentamicin treatment, all guinea pigs were euthanatized and the cranial thigh muscle containing the entire inoculum was removed. Colony-forming units were counted to determine the E coli concentration in each thigh. RESULTS: Mean +/- SD log10 colony-forming units was 9.293 +/- 0.074 in the control group, 8.161 +/- 0.478 in the 2 mg/kg treatment group, and 7.796 +/- 0.182 in the 6 mg/kg treatment group. One-way ANOVA revealed a significant (P < 0.05) difference between the control group and both treatment groups, and between both treatment groups. CONCLUSION: Bacterial killing did not differ between gentamicin given at a dosage of 6 mg/kg once daily, compared with 2 mg/kg every 8 hours in guinea pigs infected with E coli. CLINICAL RELEVANCE: Gentamicin dosage regimens with high peak concentration and long dosing interval are as efficacious as divided dosage regimens. These data support the concept that once daily administration of gentamicin for treatment of E coli infection should be investigated clinically.

Pharmacokinetics of enrofloxacin in clinically normal dogs and mice and drug pharmacodynamics in neutropenic mice with Escherichia coli and staphylococcal infections.

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 10(6) 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 colony-forming 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.

Cephalothin and cefazolin in vitro antibacterial activity and pharmacokinetics in dogs.

The periods of time that cephalothin and cefazolin serum concentration remained above minimum inhibitory concentration (MIC) for beta hemolytic, coagulase positive staphylococcal, and Escherichia coli clinical isolates were compared. Cephalothin and cefazolin were similarly very effective in vitro against staphylococcal isolates, with an MIC90 of 0.12 microgram/mL and 0.25 microgram/mL, respectively. In contrast, cefazolin was more effective than cephalothin against E coli isolates; the cefazolin MIC90 for E coli was 16 micrograms/mL and for cephalothin 64 micrograms/mL. Cefazolin (20 mg/kg intravenously [i.v.]) serum concentration remained more than MIC90 for E coli isolates significantly longer than serum concentration of cephalothin (40 mg/kg i.v.) (P < .001).

Hypotensive shock syndrome associated with acute Babesia canis infection in a dog.

A Doberman Pinscher contracted babesiosis after receiving a fresh blood transfusion from a Greyhound blood donor. Hypotensive shock syndrome was suspected on the basis of arterial hypotension, weakness, and pyrexia in the absence of detectable hemolysis and within hours of detection of low numbers of circulating Babesia canis organisms. Treatment with imidocarb dipropionate appears to have been effective in eliminating circulating B canis organisms and clinical disease. The blood donor, recently acquired from a race track, was healthy and lacked any abnormalities on initial laboratory evaluation; however, its serum antibody titer for B canis was > 1:5,000; B canis organisms were later identified on blood smears after the dog had been splenectomized and treated with corticosteroids at an immunosuppressive dosage. This case draws attention to a potential problem in current screening practices for infectious diseases of retired racing Greyhounds intended for use as blood donors.

In vitro antibacterial activity of cefoxitin and cefotetan and pharmacokinetics in dogs.

The susceptibility of 50 clinical Escherichia coli isolates to various antibacterials, including cefoxitin and cefotetan was ascertained, and the minimal inhibitory concentration (MIC) of cefoxitin and cefotetan for each of these isolates was determined. The pharmacokinetics of cefoxitin and cefotetan after a single i.v. or SC injection (30 mg/kg of body weight) were determined in 4 dogs. Of the 50 E coli isolates, 98% were susceptible in vitro to cefotetan, 90% were susceptible to cefoxitin, and 88% were susceptible to gentamicin. The MIC that would inhibit the growth of 90% of the E coli isolates (MIC90) was 0.25 microgram/ml for cefotetan and 4 micrograms/ml for cefoxitin. Plasma cefotetan concentrations remained above MIC90 for (mean +/- SD) 8.2 +/- 1.72 hours and 13.52 +/- 0.28 hours after i.v. and SC administration, respectively. Plasma cefoxitin concentrations remained above MIC90 for (mean +/- SD) 5.37 +/- 1.18 hours and 7.95 +/- 0.71 hours after i.v. and SC administration, respectively. We concluded that cefotetan was superior to cefoxitin in activity against E coli in vitro. We recommend that cefotetan be given at a dosage of 30 mg/kg, i.v., every 8 hours, or SC, every 12 hours.

Cefazolin antibacterial activity and concentrations in serum and the surgical wound in dogs.

An antibiotic selected for surgical antimicrobial prophylaxis must be present in the surgical site throughout the operation in concentration sufficient to prevent growth of contaminating pathogens. The antimicrobial spectrum, minimal toxicity, and low cost of cefazolin make this first-generation cephalosporin a logical choice for antimicrobial prophylaxis in small animal surgical procedures in which the normal microbiologic flora of skin and gastrointestinal tract are the most likely pathogens. Pharmacokinetic variables of cefazolin were determined in serum and surgical wounds in dogs. Drug concentration in interstitial fluid of muscle biopsy specimens taken at random from wound surfaces and in postoperative wound fluid samples were determined. Effective surgical wound concentration of cefazolin was defined as 4 micrograms/ml, a concentration that inhibited the growth in vitro of 100% of staphylococcal and 80% of Escherichia coli clinical isolates. After IV and SC administrations, cefazolin equilibrated rapidly between serum and the surgical wound, and concentrations in the 2 sites decreased in parallel. With a bolus dose of 20 mg/kg of body weight given IV at the beginning of surgery and repeated by SC administration at 6 hours, cefazolin concentration in the surgical wound remained > 4 micrograms/ml for longer than 12 hours.

Evaluation of bovine fibrin sealant in the dog.

Fibrin sealant (human fibrinogen-bovine thrombin) is an effective biodegradable hemostatic agent. However, there is a risk of transmission of infectious viral disease. A new bovine fibrinogen-thrombin sealant (BFTS) was tested for tissue and immune responses in intrathoracic aorta graft in dogs. Intrathoracic aorta replacement was performed in three dogs with a porous Dacron graft presealed with BFTS. Dogs were immunized preoperatively with four dermal applications of BFTS at 9-day intervals. Cellular and humoral immunity to BFTS were determined with lymphocyte blastogenesis test and enzyme-lined immunosorbent assay, respectively. Dogs were necropsied 3 weeks after aortic replacement. Histopathological examination showed that all dogs had a mild inflammatory reaction to the BFTS sealed graft, as expected in response to an inert foreign body. Assay of cellular and humoral immunity to BFTS revealed a low lymphocyte response and a moderate immunoglobulin G (Ig G) response, with no evidence of immediate Ig E (type I) or delayed (type IV) hypersensitivity reaction. We conclude that BFTS causes no adverse tissue response or immunologic reaction when used as a hemostatic agent in the dog even after multiple applications of the material.

Megacolon in cats. The role of colectomy.

In cats, clinical signs of constipation usually respond to laxatives, fecal softeners, enemas, and dietary management. Uncommonly, constipation is chronic and is associated with a marked increase in the diameter of the colon. When megacolon is present, constipation responds poorly to medical therapy. Without surgical treatment, megacolon may become an intolerable problem, with euthanasia of the cat as the probable outcome. Subtotal colectomy is now established as a satisfactory treatment for idiopathic megacolon in cats. Recently, removal of the colon has been used successfully to treat chronic constipation and megacolon associated with mechanical obstruction of the pelvic canal caused by stenosis from malunion of pelvic fractures. Colectomy has minimal long-term effects on enteric function in cats.

Pharmacokinetics of cefazolin applied topically to the surgical wound.

Topical application of antibiotics is used in the prophylaxis of postoperative surgical infections. However, whether topically applied antibiotics remain primarily in the surgical wound fluid or are systemically absorbed is uncertain. The pharmacokinetics of topically applied cefazolin were studied in a canine model that allowed simultaneous determination of serum and wound fluid antibiotic concentrations. Topical administration of cefazolin resulted in high antibiotic concentrations in the wound fluid for prolonged periods and rapid systemic absorption. Bioavailability after topical administration was 95%. Within 1 hour, the serum concentrations after topical administration equaled the serum concentrations after intravenous administration, and the concentration time curves declined in parallel. In wound fluid, the mean time above the susceptibility break point minimum inhibitory concentration after topical administration of cefazolin was 5.76 hours compared with the estimated time above the minimum inhibitory concentration of 2.55 hours after intravenous administration.

Knot security of suture materials.

The knot security of chromic gut, polyglycolic acid, polyglactin 910, polydioxanone, polypropylene, and monofilament nylon size 2-0 suture materials were tested biomechanically in vitro. Twenty reproducible knots were tied and incubated in canine serum at 37 degrees for 24 hours before testing. A "secure knot" was defined as a knot that, when tested to failure, broke rather than untied by slippage. The minimum number of throws necessary to make a secure, snug (1500 g tension) square knot was three for gut, polyglycolic acid, polyglactin 910, and polypropylene and four for polydioxanone and nylon. All throws including the first were counted. With all suture materials tested, surgeon's knots were as secure as square knots. Only gut, polyglycolic acid, and polydioxanone granny knots were as secure as square knots; no loosely tied (500 g tension) asymmetric square knots were as secure as snug square knots, and only polydioxanone and polypropylene loose square knots were as secure as snug square knots. Square knots used to start a continuous pattern required one additional throw with gut, polydioxanone, and nylon. Square knots used to end a continuous pattern required two to three additional throws with all materials tested.

Penetration of antibiotics into the surgical wound in a canine model.

The dose and timing of antimicrobial agents given for surgical wound prophylaxis should be based on the concentration-time profile of the drug in tissue at the site of contamination. However, concentrations of antimicrobial agents in surgical wounds are difficult to determine accurately. Since a surgical wound is a unique extravascular compartment with increased vascular permeability and a high surface area/volume ratio, antibiotic concentrations in sera and surgical wounds should be similar. To test this hypothesis, the pharmacokinetics of single intravenous doses of cefazolin (40 mg/kg) and gentamicin (4 mg/kg) in sera and surgical wounds in a clinically relevant surgical model using dogs were compared. Drug concentrations were determined in interstitial fluid in muscle biopsies taken randomly from wound surfaces and serial wound fluid samples collected after the incisions were closed. Protein binding of cefazolin and gentamicin in sera and wound fluids was low (less than or equal to 29 +/- 9%) in this canine model. Cefazolin and gentamicin equilibrated rapidly (less than or equal to 30 min) between serum and the surgical wound, and concentrations in the two sites declined in parallel. Values for the area under the concentration-time curve, mean residence time, and terminal half-life in serum and the surgical site for each drug were similar. Cefazolin concentrations in serum underestimated the time during which concentrations in surgical wounds exceeded the susceptibility breakpoint MIC for important pathogens by an average of 58 min (range, 26 to 109 min; P = 0.036); for gentamicin, the underestimation averaged 30 min (range, 10 to 60 min; P = 0.036). These data support the concept that the concentration-time profiles of antimicrobial agents in serum may prove valuable clinically as guides to determining the and timing of antibiotic administration necessary for effective antimicrobial prophylaxis in surgery. Further studies are needed to determine the surgical wound pharmacokinetics of highly protein-bound antibodies.

Subtotal colectomy for treatment of chronic constipation associated with idiopathic megacolon in cats: 38 cases (1979-1985).

Chronic constipation, nonresponsive to medical management and associated with idiopathic megacolon, was diagnosed in 38 cats from 1979 to 1985. All cats were treated by subtotal colectomy and enterocolostomy, in which the ileum or distal portion of the jejunum was joined to a 2- to 4-cm segment of distal portion of the colon preserved to accommodate an end-to-end anastomosis. After surgery, cats usually were depressed and anorectic, had tenesmus, and passed liquid tarry feces. In 37 cats 1 week to 3 months after surgery, character of the feces changed from diarrhea to soft semiformed or formed feces. One cat had severe diarrhea that was nonresponsive to diet change and pharmacologic treatment; the diarrhea resolved after 4.5 months. One cat developed a stricture of the enterocolostomy, which was relieved by 3 balloon catheter dilatations. All cats regained normal appetite, did not lose weight, and were not incontinent. Three cats had sporadic episodes of constipation and were easily treated. Results of histologic examination of the resected portion of colon in 23 cats were inconclusive.