Topic:Antimicrobial
Antimicrobials are agents used to inhibit the growth of or destroy microorganisms, including bacteria, viruses, fungi, and parasites, in horses. They are employed in the treatment and prevention of infections and play a role in maintaining equine health. Antimicrobials can be classified into various categories, such as antibiotics, antifungals, antivirals, and antiparasitics, each targeting specific types of pathogens. The use of antimicrobials in horses is subject to considerations regarding dosage, administration routes, and potential resistance development. This page compiles peer-reviewed research studies and scholarly articles that explore the application, efficacy, and challenges associated with antimicrobial use in equine medicine.
Disorders of the infraspinatus tendon and bursa in three horses. 3 horses with penetrating wounds to the shoulder area were examined because of forelimb lameness. Results: All horses had physical examination findings (decreased cranial phase of the stride, swelling in the shoulder region, and signs of pain on manipulation of the shoulder) that were suggestive of problems in the upper portion of the forelimb. Injury to the biceps tendon or bursa was the primary differential diagnosis in each instance, but no abnormalities involving those structures were found. Radiographic and ultrasonographic imaging revealed injuries to the caudal eminence of the greater t...
Equine gastrointestinal motility–ileus and pharmacological modification. Colic is a common problem encountered in equine practice. Alteration of gastrointestinal motility is often the underlying cause for abdominal pain. Gastrointestinal motility can be measured as myoelectric activity, mechanical activity, and transit of intraluminal contents. Regulation of motility is based on a complex interaction between central innervation, autonomic innervation, and the enteric nervous system. Various humoral and neurochemical substances are required to interact flawlessly to allow propulsive motility. Ileus is defined as the absence of propulsive aboral movement of gastroint...
In vitro efficacy of a buffered chelating solution as an antimicrobial potentiator for antifungal drugs against fungal pathogens obtained from horses with mycotic keratitis. To determine whether a novel third-generation chelating agent (8 mM disodium EDTA dehydrate and 20 mM 2-amino-2-hydroxymethyl-1, 3-propanediol) would act as an antimicrobial potentiator to enhance in vitro activity of antifungal medications against fungal isolates obtained from horses with mycotic keratitis. Methods: Fungal isolates (3 Aspergillus isolates, 5 Fusarium isolates, 1 Penicillium isolate, 1 Cladosporium isolate, and 1 Curvularia isolate) obtained from horses with mycotic keratitis and 2 quality-control strains obtained from the American Type Culture Collection (ATCC; Candida albica...
Aspects of glycoconjugate production and lysozyme- and defensins-expression of the ceruminous glands of the horse (Equus przewalskii f. dom.). The distribution of complex glycoconjugates and antimicrobial substances in the ceruminous glands of the horse (Equus przewalskii f. dom., type: pony) was studied using carbohydrate histochemical and immunohistochemical methods. The epithelial cells and luminal secretion of these glands exhibited considerable amounts of glycoconjugates with various saccharide residues, such as alpha-D-mannose, alpha-L-fucose, beta-D-galactose, beta-N-acetyl-D-glucosamine and sialic acid, including O-acetylated sialic acid. Several sugars (alpha-D-mannose, alpha-L-fucose, and beta-D-galactose) were also detecta...
Investigation of falsely reported resistance of Streptococcus equi subsp. zooepidemicus isolates from horses to trimethoprim-sulfamethoxazole. The objective of this study was to investigate the perceived increase in resistance of Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) isolated from the lower respiratory tract of horses to trimethoprim-sulfamethoxazole (SXT). The recorded SXT-susceptibility results of 50 S. zooepidemicus isolates from the tracheal wash fluid of equine patients examined at Colorado State University Veterinary Teaching Hospital from each of 2 time periods (1987-1990 and 1997-2001) were compared and statistically analyzed using a cross-sectional study design. There was a statistically significant diff...
Multidrug-resistant Salmonella and nosocomial infections. Nosocomial infections are a serious threat to optimum patient care. In addition, nosocomial infections can have far-reaching consequences for the hospital personnel and the financial aspects of the hospital. Nosocomial infections with Salmonella spp have been described among hospitalized equine populations more frequently than any other agent. Salmonella spp associated with hospitalized equids often possess more antimicrobial resistance determinants than do Salmonella spp isolated from healthy horses in the general population. There is little evidence to suggest that resistant salmonellae are ...
Postoperative management of the large colon volvulus patient. Horses with large colon volvulus (LCV) often require intensive postoperative medical management. Although early referral and surgical intervention are critical for minimal postoperative complications and a successful outcome, this is often not possible for many reasons. Endotoxemia, extensive mucosal damage with subsequent severe hypoproteinemia, and focal ischemic necrosis are the major causes of postoperative morbidity and mortality. Although fluid therapy, flunixin meglumine, and antimicrobials are still the mainstay of perioperative management, synthetic colloids are being used to maintain...
Characterization of antimicrobial aerosols for administration to horses. A study was conducted to characterize the aerosols produced by a medical ultrasonic nebulizer using solutions containing antimicrobials appropriate for therapy of equine lower respiratory bacterial infections (gentamicin sulfate and ceftiofur sodium). Test aerosols were generated using an ultrasonic nebulizer and were analyzed using a laser diffraction aerosol particle analyzer. The aerosol was described in terms of the particle size distribution (volume median diameter), span (sample dispersion), and aerosol density (% volume). The particle size distribution and aerosol density of gentamicin ...
Purpura haemorrhagica in 53 horses. The medical records of 53 horses with purpura haemorrhagica were reviewed. Seventeen of them had been exposed to or infected with Streptococcus equi, nine had been infected with Corynebacterium pseudotuberculosis, five had been vaccinated with S. equi M protein, five had had a respiratory infection of unknown aetiology, and two had open wounds; the other 15 cases had no history of recent viral or bacterial infection. The horses were between six months and 19 years of age (mean 8.4 years). The predominant clinical signs were well demarcated subcutaneous oedema of all four limbs and haemorrhages...
Clostridium difficile: prevalence in horses and environment, and antimicrobial susceptibility. Clostridium difficile has been associated with acute colitis in mature horses. Objective: To survey C. difficile colonisation of the alimentary tract with age, occurrence of diarrhoea and history of antibiotic therapy; and to study the occurrence and survival of C. difficile in the environment and antimicrobial susceptibility of isolated strains. Methods: A total of 777 horses of different breeds, age and sex were studied. Further, 598 soil samples and 434 indoor surface samples were examined. Antimicrobial susceptibility of 52 strains was investigated by Etest for 10 antibiotics. Results: In ...
Increases in cytokine and antimicrobial peptide gene expression in horses by immunomodulation with Propionibacterium acnes. Immunomodulation with Propionibacterium acnes is used for prophylaxis of respiratory disease or in horses suffering from chronic pulmonary inflammation; however, the mechanism for this response is poorly understood. Semiquantitative reverse transcriptase-polymerase chain reaction assays were used to evaluate gene expression of interleukin (IL)-2, IL-10, interferon (IFN)-gamma, and NK-lysin in healthy horses treated with P. acnes. Findings in the study indicated that horses treated with a P. acnes-based immunomodulator exhibited increased IFN-gamma and NK-lysin gene expression in peripheral blo...
In vitro susceptibilities of Rhodococcus equi and other common equine pathogens to azithromycin, clarithromycin, and 20 other antimicrobials. The objective of this study was to determine in vitro activities of azithromycin (AZM), clarithromycin (CLR), and 20 other antimicrobial agents against Rhodococcus equi and other common equine bacterial pathogens. A total of 201 bacterial isolates from various equine clinical samples were examined. CLR was more active than AZM against R. equi, with MICs at which 90% of the isolates were inhibited of 0.12 and 1.0 micro g/ml, respectively. Other antimicrobial agents highly active against at least 90% of R. equi isolates in vitro included rifampin, gentamicin, and imipenem. Both AZM and CLR showe...
Owner survey of headshaking in horses. To determine signalment, history, clinical signs, duration, seasonality, and response to various treatments reported by owners for headshaking in horses. Methods: Owner survey. Methods: 109 horses with headshaking. Methods: Owners of affected horses completed a survey questionnaire. Results: 78 affected horses were geldings, 29 were mares, and 2 were stallions. Mean age of onset was 9 years. Headshaking in 64 horses had a seasonal component, and for most horses, headshaking began in spring and ceased in late summer or fall. The most common clinical signs were shaking the head in a vertical pla...
Medical treatment of cholangiohepatitis and cholelithiasis in mature horses: 9 cases (1991-1998). The medical approach to treatment of cholangiohepatitis and cholelithiasis in 9 horses is described. Seven horses were treated successfully and returned to normal use, with a minimum follow-up period of 12 months. Long-term antimicrobial therapy was believed to be critical in those cases that survived, with a median treatment duration of 51 days (range 17-124 days). Treatment failure was associated with severe periportal and bridging hepatic fibrosis from biopsy material obtained at admission in 2 horses, one of whom also presented with hyperammonaemic hepatic encephalopathy. Transabdominal ul...
Pythiosis with bone lesions in a pregnant mare. A 9-year-old pregnant mare was referred for evaluation of a nonhealing wound of 8 weeks' duration on the lateral aspect of the left forelimb. A soft tissue mass encircled the proximal two thirds of the metacarpus; radiography revealed a moderate periosteal reaction affecting metacarpal bone i.v. Histologic and immunohistochemical examinations revealed eosinophilic granulomatous inflammation and Pythium sp in the soft tissues. The mare was treated for 12 days with antimicrobials, medicated wound dressings, debridement, and i.v. administration of sodium iodide; radiography revealed progression o...
Antibacterial properties of a silver chloride-coated nylon wound dressing. A silver chloride-coated nylon wound dressing (Ag-WD) was evaluated in vitro for antimicrobial activity against five common equine wound pathogens. Methods: Bacterial susceptibility study. Methods: Equine wound pathogens: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Streptococcus equi subspecies zooepidemicus, and Staphylococcus aureus. Methods: An inoculum of each pathogen was incubated directly with Ag-WD and quantitated after 24 to 48 hours of incubation. To determine if bactericidal activity of Ag-WD was contact dependent, an inoculum of E. coli and Staphylococcus aureu...
Antibacterial activity of antileukoprotease. Antileukoprotease (ALP), or secretory leukocyte proteinase inhibitor, is an endogenous inhibitor of serine proteinases that is present in various external secretions. ALP, one of the major inhibitors of serine proteinases present in the human lung, is a potent reversible inhibitor of elastase and, to a lesser extent, of cathepsin G. In equine neutrophils, an antimicrobial polypeptide that has some of the characteristics of ALP has been identified (M. A. Couto, S. S. L. Harwig, J. S. Cullor, J. P. Hughes, and R. I. Lehrer, Infect. Immun. 60:5042-5047, 1992). This report, together with the catio...
Instrument sterilization, skin preparation, and wound management. Recent advances in instrument sterilization include the introduction of gas plasma sterilization and the increased use of glutaraldehyde. Gas plasma sterilization has the advantages of no toxic residue effects, reduced turnover time, and applicability for sterilization of heat- and moisture-sensitive instruments. Chlorhexidine gluconate (4%) appears to be a superior preoperative surgical scrub for both the surgeon and the patient because of its increased antimicrobial efficacy, residual activity, and minimal tissue reactions. There are many new wound dressings and topical medications for treat...
Infectious tenosynovitis. Infectious tenosynovitis is treated similarly to infectious arthritis. The principles of treatment include an early diagnosis and immediate therapy. Therapy should include use of systemic and local antimicrobials and sheath lavage and drainage. Fibrosis and adhesions can be minimized with passive range of motion exercises, intrathecal hyaluronate, and phenylbutazone therapy. Restrictive fibrosis may be treated successfully by annular ligament resection.
Ventricular tachycardia and myocardial dysfunction in a horse. Ventricular tachycardia develops less frequently than supraventricular dysrhythmias and generally is more indicative of cardiac disease. The horse in this report had clinical signs of lethargy and hypophagia and was determined to have sustained ventricular tachycardia. Echocardiography was a valuable diagnostic tool and revealed an echodense area in the left ventricle that had subnormal ventricular performance. A primary heart problem of an inflammatory nature was suspected. The horse responded favorably to treatment with lidocaine, antimicrobials, and aspirin, as well as stall rest. The horse...
Systemic candidiasis in four foals. Four foals were admitted to the neonatal intensive care unit in the first 2 days of life with problems related to birth hypoxia (neonatal maladjustment syndrome, renal failure, necrotizing enterocolitis) and sepsis. Foals were hospitalized for an extended period (35 to 70 days) and received treatment with several broad spectrum antimicrobial agents. Invasive monitoring and treatment procedures included intravenous catheterization, urinary catheterization, and parenteral nutritional and ventilatory support. In each foal, infections of undetermined cause developed, and systemic candidiasis was d...
Selective inhibition of microbial serine proteases by eNAP-2, an antimicrobial peptide from equine neutrophils. Equine neutrophil antimicrobial peptide 2 (eNAP-2), a recently described antimicrobial peptide isolated from equine neutrophils, was found to selectively inactivate microbial serine proteases (subtilisin A and proteinase K) without inhibiting mammalian serine proteases (human neutrophil elastase, human cathepsin G, and bovine pancreatic trypsin). Although the primary structure of eNAP-2 resembled that of several known antiproteases that belong to the 4-disulfide core peptide family, this pattern of selectivity is unique. eNAP-2 formed a noncovalent complex with native subtilisin A or proteinas...
Identification of eNAP-1, an antimicrobial peptide from equine neutrophils. Endogenous, cysteine-rich antimicrobial peptides known as defensins are prominent components of human, rabbit, and rat neutrophils, yet little is known about their occurrence in other mammalian species. Although we did not detect mature (i.e., processed) defensins in equine neutrophil granules, we found that these granules contained small amounts of other cysteine-rich peptides with antimicrobial activity. One of these, eNAP-1, was purified by a combination of gel permeation and reversed-phase high-performance liquid chromatography from acid extracts prepared from the cytoplasmic granules of e...
Effects of exercise stress on various immune functions in horses. Chemotactic locomotion and luminol-dependent chemiluminescence of neutrophils, mitogen-induced lymphocyte blastogenesis, serum cortisol concentration, immunoglobulin quantification, and leukocyte counts were determined to evaluate the effect of a single strenuous exercise in horses. Increased serum cortisol concentration (P less than 0.01) and an increased neutrophil-to-lymphocyte ratio (P less than 0.05) indicated that horses had been stressed. The chemotactic index and peak chemiluminescence production decreased significantly (P less than 0.05 and P less than 0.01, respectively) 1 day after ...
Septic arthritis of the distal interphalangeal joint in 12 horses. The medical records of 12 horses with septic arthritis of a distal interphalangeal joint were reviewed to determine clinical features and response to treatment. Sepsis was caused by trauma or an injection that resulted in an open or contaminated distal interphalangeal joint. All horses were severely lame. Treatment included broad-spectrum parenterally administered antimicrobial drugs (ten horses), percutaneous through-and-through joint lavage (eight horses), indwelling drains (three horses), immobilization of the limb in a cast (three horses), intraarticular injection of sodium hyaluronate (on...
Corynebacterium pseudotuberculosis: in vitro susceptibility to 39 antimicrobial agents. The minimal inhibitory concentrations of 39 antimicrobial agents for 54 isolates of Corynebacterium pseudotuberculosis in vitro have been determined. The most active agents were penicillins, macrolides, tetracyclines, cephalosporins, lincomycin, chloramphenicol, and rifampicin. Most isolates were resistant to aminoglycosides, nitrofurans, polymyxins, nalidixic acid, and cycloheximide.
Clinical use of metronidazole in horses: 200 cases (1984-1989). Case records of 200 horses treated with metronidazole were reviewed. Horses were treated for respiratory tract infections (90 cases), peritonitis or abdominal abscess (39 cases), celiotomy (49 cases), orthopedic infections (6 cases), and miscellaneous soft tissue infections (16 cases). Bacteria of the genus Bacteroides were most prevalent (55 of 167 anaerobic isolates). Metronidazole was always used in combination with other antimicrobial drugs. Only 4 of the 200 horses had signs of adverse effects associated with metronidazole treatment. Those 4 horses had poor appetite that resolved when met...
In vitro antimicrobial activity of defensins against ocular pathogens. New approaches to antimicrobial therapy for ocular pathogens must overcome organisms that are resistant to current therapeutic modalities. This investigation examined the antimicrobial activity of novel antimicrobial neutrophil peptides (defensins NP-1 and NP-5) against isolates from clinical ocular microbial infections in humans and horses. The test panel of human clinical isolates included Candida albicans, an alpha-hemolytic Streptococcus, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Morganella morganii. The test panel of equine pathogens included three clinical isolates of P aerug...
Ulceration in the proximal portion of the urethra as a cause of hematuria in horses: four cases (1978-1985). Sudden onset of hematuria was associated with mucosal ulceration of the proximal portion of the urethra in 1 stallion and 3 geldings. Hematuria was observed characteristically and consistently at the end of urination. Mucosal ulceration was identified endoscopically in the proximal portion of the urethra at the level of the ischial arch. Biopsy of an ulcerated area of the proximal urethra in one gelding revealed transitional cell carcinoma. Treatment regimens varied from systemic antimicrobial and/or vasoactive therapy to diversion of urinary flow via a temporary perineal urethrostomy. Hematur...
Prevalence of ocular microorganisms in hospitalized and stabled horses. Microorganisms from normal eyes of hospitalized and stabled horses were identified, and the frequency of isolation was compared between the 2 groups. Using standard techniques, swab specimens from both eyes of 22 hospitalized horses and both eyes of 18 stabled horses were cultured for aerobic bacteria and fungi. Ninety-six aerobic bacteria and 57 fungi were isolated. The predominant bacterial isolates were gram-positive organisms, most of which belonged to the genera Corynebacterium, Bacillus, Staphylococcus, and Streptomyces. Gram-negative organisms comprised less than one-fourth of the bacte...