Topic:Antibiotics
Antibiotics are medications used to treat bacterial infections in horses. They work by either killing bacteria or inhibiting their growth, aiding the horse's immune system in overcoming the infection. Commonly used antibiotics in equine medicine include penicillin, trimethoprim-sulfamethoxazole, and gentamicin. The selection of an antibiotic depends on factors such as the type of bacteria, the site of infection, and the horse's health status. Responsible use of antibiotics is essential to minimize the risk of resistance. This page compiles peer-reviewed research studies and scholarly articles that explore the efficacy, administration, and impact of antibiotics on equine health.
Botulism as a sequel to open castration in a horse. Clostridium botulinum and type-B C botulinum toxin were isolated from a necrotic wound that developed subsequent to castration in a 2-year-old Thoroughbred gelding. The horse had clinical signs of botulism and was successfully treated with wound debridement, C botulinum type-B antitoxin, potassium penicillin, and supportive care.
Immune-mediated hemolytic anemia induced by penicillin in horses. Three horses developed severe, immune-mediated hemolytic anemia after treatment with penicillin. The horses had positive direct antiglobulin (Coombs) tests and high titers of IgG antibody that agglutinated penicillin-coated equine red cells. Two of the horses were tested for antibodies to autologous red cell antigens; autoantibodies were not present. Titers of antipenicillin antibody decreased after penicillin was discontinued but IgG antibody was detectable months after recovery. One of the horses was challenged with penicillin; antibody titer increased slightly, but anemia did not develop. A...
Cellulitis and subcutaneous abscesses caused by Rhodococcus equi infection in a foal. Cellulitis and subcutaneous abscess formation was diagnosed in a 3-month-old Thoroughbred filly. Clinical signs consisted of a large ulcerated plaque, with satellite pustules on the medial aspect of the right hock and subcutaneous abscesses in the right inguinal and mammary gland areas. Laboratory analysis revealed mature neutrophilia. Rhodococcus equi was isolated from the cellulitis and the subcutaneous abscess. Oral administration of erythromycin and rifampin for 35 days resulted in a clinical cure.
Antimicrobial susceptibility of microorganisms isolated from equine orthopedic patients. Positive cultures were obtained from 60 equine orthopedic cases during a 12 year period (1974-1985). These cases consisted of 34 long or cuboidal bone fractures, 13 arthrotomy/arthroscopy procedures for removal or internal fixation of a fracture, 7 proximal splint bone fractures, and 6 facial or mandibular fractures. Excluding the 13 arthrotomies, only 10 (21%) of the 47 were open fractures. Multiple organisms were isolated from 36 cases (20 long or cuboidal bone fractures, 7 splint bone fractures, 5 mandibular fractures, and 4 intra-articular fractures). Of the 142 isolates, 35 (24%) were mem...
Absorption of neomycin from the equine uterus: effect of stage of oestrous cycle and volume of vehicle. Plasma concentrations of neomycin were measured following intrauterine infusion of 3.3 mg/kg bodyweight neomycin sulphate. Mares in oestrus absorbed approximately 6 per cent of neomycin infused whereas mares in a luteal phase absorbed 56 per cent. The volume of infusate also affected absorption as increased volume resulted in decreased absorption. The decreased absorption both during oestrus and when large volumes were used was probably due to reflux of antibiotic through the cervix.
Cardiovascular effects of intravenous sodium penicillin, sodium cefazolin, and sodium citrate in awake and anesthetized horses. Sodium penicillin, sodium cefazolin, and sodium citrate were administered to six adult horses on separate occasions, when awake and during anesthesia. The order of administration was randomized and studies were separated by a minimum of 7 days. Arterial blood pressure decreased significantly (less than 0.05) from control 5 minutes after intravenous (IV) sodium penicillin in awake and anesthetized horses. Systolic arterial blood pressure remained significantly (less than 0.05) decreased 10 minutes after IV sodium penicillin in anesthetized horses. Sodium cefazolin and sodium citrate did not sig...
Group C streptococcal arthritis. A case report of equine transmission. Presented is the third known case of a group C streptococcal arthritis, this case documented in a healthy 42-year-old horse trainer, apparently transmitted by a mare. After a delayed diagnosis, the patient responded favorably to surgical drainage and parenteral penicillin G, but required a manipulation of his knee under general anesthesia. Although rare, group C streptococcal arthritis can occur in hosts with no apparent predisposing factors. Frequent exposure to farm animals may increase the risk.
Rational selection of antimicrobial drugs for treatment of infections of horses. The goal of antimicrobial drug use is quite specific. Consideration of many microbe-related, host-related, and drug-related factors is necessary for appropriate selection and use of antimicrobial drugs in equine patients. The concepts and data presented in this article demonstrate that fact. At the risk of oversimplification, "The bug denotes the drug, and the horse directs the course."
Antimicrobic susceptibility of bacterial pathogens from horses. Rational choice of an antimicrobial agent requires that the condition for which the drug is prescribed contain an infectious agent and, if so, knowledge of the susceptibility of the microorganism to antimicrobial drugs. Unfortunately, most infectious conditions necessitate the use of an antimicrobic drug before data from the microbiology laboratory are available. The data presented are meant to serve as a guide in the choice of antimicrobic drugs for treatment of infectious processes of the horse before knowledge of the nature of the microorganism isolated as well as its susceptibility to anti...
Pharmacologic considerations in drug therapy in foals. Rational drug therapy in the foal requires a sound knowledge of the pharmacodynamics and pharmacokinetics of various drugs as well as a thorough understanding of the physiologic differences that exist between the neonate and the adult and that may serve to alter drug disposition and, therefore, drug response. A summary of these physiologic factors with emphasis on the foal is presented and is followed by recommendations regarding the applied therapeutics of various antimicrobial agents.
Drug therapy of respiratory disorders. The emphasis of this article is on the clinical application of drugs in therapy for treatment of disorders of the lower respiratory tract. Medications discussed include those used to enhance clearance of secretions and those employed to prevent and/or alleviate bronchoconstriction. Antimicrobial agents and respiratory stimulants are briefly mentioned.
Povidone-iodine lavage treatment of experimentally induced equine infectious arthritis. Both tarsocrural joints of 4 horses were inoculated with 1.5 X 10(5) colony-forming units of Staphylococcus aureus. On days 1, 3, and 6, each horse had one tarsocrural joint lavaged with a balanced electrolyte solution and had the contralateral tarsocrural joint lavaged with 0.1% povidone-iodine solution. All horses were orally administered trimethoprim (5 mg/kg)/sufadiazine (25 mg/kg) combination twice daily and phenylbutazone (2 g) once daily for the duration of the study (21 days). On days 0, 1, 3, 6, 9, 14, and 21, synovial fluid specimens were collected and analyzed for color, clarity, to...
Anti-pseudomonas activity of anti-lipopolysaccharide hyperimmune equine plasma. Passive immunotherapy with anti-lipopolysaccharide hyperimmune equine plasma (Anti-LPS) is effective in treating experimental Gram-negative bacterial infections. The bactericidal activity of anti-LPS towards five different Pseudomonas species, including two multiresistant Pseudomonas aeruginosa isolates was tested here, as well as the ability of anti-LPS to inhibit the quantitative chromogenic limulus amoebocyte lysate (LAL) assay. Anti-LPS caused a mean reduction of 84.4 +/- 3.2% (P less than 0.001) in the number of colony forming units (cfu) of all isolates, whereas saline and complement ina...
Comparison of various treatments for experimentally induced equine infectious arthritis. To evaluate the effects of 5 treatments on clinical responses, synovial fluid analysis, radiographic changes, bacteriologic culture results of the synovial fluid and synovial membrane, microscopic characteristics of the synovial membrane, and articular cartilage histochemistry, Staphylococcus aureus organisms (1.6 X 10(6) colony-forming units) were inoculated into the tarsocrural joints of 12 horses (n = 24 joints; 2 joints/horse). Each horse was given phenylbutazone (2 g) orally, every 24 hours, beginning 24 hours after inoculation. Two horses (ie, 4 joints) were not given other treatment (co...
Pharmacokinetics and renal clearance of sulfamethazine, sulfamerazine, and sulfadiazine and their N4-acetyl and hydroxy metabolites in horses. Plasma disposition, protein binding, urinary recovery, and renal clearance of sulfamethazine (SMZ), sulfamerazine (SMR), and sulfadiazine (SDZ) and their N4-acetyl and hydroxy derivatives were studied in 4 horses in a crossover trial. The plasma concentration-time curves of the metabolites paralleled those of the parent drug in the elimination phase. Sulfamethazine and SMR were extensively metabolized. In plasma and urine, the main metabolite of the 3 sulfonamides tested was the 5-hydroxypyrimidine derivative, which was highly glucuronidated. Difference in elimination half-life of SMZ, SMR, an...
Antimicrobial selection and dosage in the treatment of equine bacterial infections. The success of antimicrobial therapy depends on administration of an agent to which the pathogenic microorganisms are susceptible at the concentrations attained at the site of infection. The route of administration, size of the dose and dosing interval must be appropriate for the drug preparation selected. With penicillins in particular, dosage can be tailored to the severity of the infection and quantitative susceptibility of the microorganism. This approach cannot be applied to aminoglycosides because their relatively narrow margin of safety limits the amount which can be administered. In se...
Single- and repeat-dose pharmacokinetic studies of chloramphenicol in horses: values and limitations of pharmacokinetic studies in predicting dosage regimens. A single-dose pharmacokinetic study of chloramphenicol in propylene glycol was done in 6 horses after 22 mg/kg was administered IV. Serum drug concentrations obtained at various predetermined intervals were determined by an electroncapture gas-chromatographic technique. The time-concentration data were described by a 2-compartment open model, and various pharmacokinetic variables were estimated. The median elimination rate constant was estimated to be -0.0185 minute-1 (-0.0225 to -0.0148 minute-1), and the median half-life was 37.36 minutes (30.74 to 46.90 minutes). The median apparent volume ...
Equine ehrlichiosis in northern California: 49 cases (1968-1981). Case records of horses with equine ehrlichiosis (Ehrlichia equi) at the University of California Veterinary Medical Teaching Hospital and Ackerman Creek Large Animal Clinic were analyzed for evaluation of clinical signs, time of onset, hematologic values, response to treatment, and recovery. Equine ehrlichiosis was found to be seasonal in horses in the foothills of northern California, with higher incidence than reported previously. The horses developed fever, anorexia, depression, limb edema, icterus, and ataxia. Hematologic changes were leukopenia, thrombocytopenia, icterus, anemia, and incl...
Immune-mediated hemolytic anemia and thrombocytopenia in a foal. A one-month-old Quarter Horse filly had unilateral epistaxis, hyphema, icterus, petechial hemorrhages in the oral, nasal, conjunctival, and vulvar mucous membranes, anemia, thrombocytopenia, negative antinuclear test result, and a positive direct Coombs' test result. Megakaryocytes or cell-associated IgG (fluorescent antibody and immunoperoxidase stains) were not found in bone marrow biopsy specimens. Treatment consisted of glucocorticoids, antibiotics, and a single whole blood transfusion. The foal responded well to treatment, did not develop relapses of the disease, and was clinically normal...
Umbilical cord remnant infections in foals: 16 cases (1975-1985). Infection of the umbilical cord remnants was diagnosed in 16 foals. The infection was found in the urachus alone in 3 foals, the umbilical arteries in 2 foals, the urachus and umbilical arteries in 3 foals, the urachus and umbilical vein in 2 foals, and the urachus, umbilical vein, and umbilical arteries in 2 foals. The specific location of the infection was not determined in 4 foals. Eleven foals developed an acquired patent urachus between 4 and 16 days of age. Seven foals had one or more joints infected. All foals with umbilical cord remnant infections were treated with orally, intramuscula...
Role of anaerobic bacteria in equine endometritis. This study, performed over 3 breeding seasons, surveyed anaerobic and aerobic bacterial isolates from 362 clitoral and endometrial swabs and uterine washes from 263 Thoroughbred maiden, foaling, foal heat and barren mares, and from 113 urethral, urethral fossa, preputial and pre-ejaculatory fluid swabs from 29 Thoroughbred stallions. The significance of isolates was determined by their association with acute endometritis, as determined by concurrent endometrial smear results and by consideration of age and reproductive status before and after the survey. The results suggest that the horse uter...
Cellulitis associated with coagulase-positive staphylococci in racehorses: nine cases (1975-1984). Nine Thoroughbred racehorses were admitted with cellulitis (of one or more limbs) associated with coagulase-positive staphylococci. The right hindlimb was affected in 4 horses, the right forelimb in 2, the left hindlimb in 1, and both hindlimbs in 2. Typical abnormalities included high values for rectal temperature (9 horses) and heart rate (5 horses), hyperfibrinogenemia (7 horses), leukocytosis (7 horses), and neutrophilia (6 horses). The staphylococcal isolants were speciated in 3 horses and classified as Staphylococcus aureus. Complications included skin loss (5 horses), laminitis of the a...
Body fluid concentrations and pharmacokinetics of chloramphenicol given to mares intravenously or by repeated gavage. Serum concentrations and the pharmacokinetics of chloramphenicol were determined in 6 healthy mares after a single IV administration (50 mg/kg of body weight) or after the 1st and 5th sequential intragastric (IG) administration (50 mg/kg/6 hours) of chloramphenicol. Synovial fluid, peritoneal fluid, CSF, and urinary concentrations of chloramphenicol after the IG administrations also were determined. Mean (+/- SEM) overall elimination rate constant (K) values for the IV, 1st IG, and 5th IG dosages were 0.42 +/- 0.064/hr, 0.42 +/- 0.049/hr, and 0.29 +/- 0.074/hr, respectively, and were not signi...
Pharmacokinetics of rifampin given as a single oral dose in foals. Six foals from 6 to 8 weeks of age were given a single oral dose of rifampin at a dosage of 10 mg/kg of body weight. Serum rifampin concentrations were measured serially during a 24-hour period. The mean peak serum rifampin concentration was 6.7 micrograms/ml at 4 hours after treatment. The concentration decreased slowly, and at 24 hours the mean value was 2.7 micrograms/ml. The elimination half-life was 17.5 hours, and the elimination rate constant was 0.04/hr.
Pharmacokinetics and endometrial tissue concentrations of ticarcillin given to the horse by intravenous and intrauterine routes. Plasma and endometrial tissue concentrations of ticarcillin were measured in healthy mares. In the first of the 3 separate phases comprising the study, ticarcillin disodium (30 mg/kg) was administered IV. The mean peak concentration in endometrial tissue, 12.9 micrograms/g, was attained at 30 minutes. The plasma half-life of the drug in the 6 mares was 0.83 +/- 0.22 hour. Six grams of the drug was diluted in 250 ml of sodium chloride injection USP (2nd phase) and in 60 ml of sodium chloride injection USP (3rd phase). These dilutions were administered by intrauterine infusion. In phase 2, the m...