Trimethoprim-Sulfamethoxazole is an antibiotic combination commonly used in equine medicine to treat bacterial infections. This combination includes trimethoprim, a dihydrofolate reductase inhibitor, and sulfamethoxazole, a sulfonamide, which work synergistically to inhibit bacterial folic acid synthesis. It is administered to horses for conditions such as respiratory infections, urinary tract infections, and certain skin infections. The pharmacokinetics, efficacy, and safety profile of trimethoprim-sulfamethoxazole in horses have been the subject of various studies. This page compiles peer-reviewed research studies and scholarly articles that explore the use, dosing regimens, and potential side effects of trimethoprim-sulfamethoxazole in equine medicine.
Braga PRC, Dos Santos CA, Bertani AMJ, Vieira T, Amarante AF, Reis AD, Sacchi CT, Camargo CH, Ribeiro MG, Borges AS, Tiba-Casas MR.This study reports the genomic characterization of the multidrug resistant Salmonella Newport strain 195_20 recovered from the diarrheic faeces of a foal in Brazil and co-harbouring the mcr-9, blaCMY-2 and qnrB19 antibiotic resistance genes. Bacterial isolate positive for mobile colistin resistance gene (mcr-9) was submitted to antimicrobial susceptibility testing by disk diffusion and broth microdilution for colistin and polymyxin B. The isolate was submitted to whole genome sequencing by Illumina technology and Nanopore Sequencing. Conjugation assays, plasmid sizes determined by S1-PFGE and ...
Ekstrand C, Nostell K, Gehring R, Bondesson U, Bröjer J.Septicaemia in the neonatal foal is caused by both Gram positive and Gram negative bacteria. The life-threatening nature of this condition requires treatment to be initiated with broad spectrum antimicrobial drugs pending antimicrobial susceptibility testing. Potentiated sulphonamides, for example, trimethoprim combined with sulfadiazine, could be clinically relevant options but their pharmacokinetics in the neonatal foal are unknown. To describe the plasma disposition of trimethoprim and sulfadiazine in neonatal foals and to relate the results to patterns in the minimum inhibitory concentrati...
Ribeiro MG, de Morais ABC, Alves AC, Bolaños CAD, de Paula CL, Portilho FVR, de Nardi Júnior G, Lara GHB, de Souza Araújo Martins L, Moraes LS....Klebsiella species, particularly K. pneumoniae, are well-known opportunistic enterobacteria related to complexity of clinical infections in humans and animals, commonly refractory to conventional therapy. The domestic animals may represent a source of the pathogenic and multidrug-resistant Klebsiella species to humans. Nevertheless, most studies involving Klebsiella-induced infections in domestic animals are restricted to case reports or outbreaks. We retrospectively investigated selected epidemiological data, clinical aspects, and in vitro susceptibility pattern of 697 non-repetitive Klebsiel...
Johnston GCA, Lumsden JM.To describe the prevalence and antimicrobial susceptibility of bacterial isolates cultured from surgical specimens of infected arytenoid cartilage and granulomas. Methods: Retrospective cohort study. Methods: Thirty-three thoroughbred horses. Methods: Hospital records were retrieved for all horses admitted to a referral hospital for arytenoid chondropathy surgery that had samples submitted for culture and sensitivity between 2005 and 2019. Descriptive analyses were performed. Results: In total, 56 bacterial isolates were obtained. Gram-positive bacteria (58%), Gram-negative bacteria (54%), and...
Winther L, Guardabassi L, Baptiste KE, Friis C.Sulfadiazine (SDZ) and trimethoprim (TMP) concentrations were examined in plasma and pulmonary epithelial lining fluid (PELF), following intravenous and oral administration and compared to minimum inhibitory concentrations (MICs) of common bacterial isolates from equine lower airway infections. SDZ/TMP (25/5 mg/kg) was administered intravenously, intragastric or per os to fed horses, and blood samples were collected before and 11 times, over 24 h, after administration. PELF samples were collected via a tampon device four times after drug administration and analysed for drug concentrations. Add...
Smith MA, Ross MW.To determine features of postoperative wound infection caused by Actinobacillus spp in horses undergoing clean, elective surgery and to evaluate bacterial susceptibility profiles of bacteria isolated. Methods: Retrospective study. Methods: 10 horses. Methods: Data were retrieved from medical records and the microbiology laboratory database. Results: 1,604 horses underwent clean, elective surgical procedures during the study period. Of these, 23 (1.43%) had postoperative wound infections, and Actinobacillus spp was isolated from 10 of these 23 (43%). Surgical procedures in these 10 horses inclu...
van Duijkeren E, Ensink JM, Meijer LA.The distribution of trimethoprim (TMP) and sulfadiazine (SDZ) into subcutaneously implanted noninfected tissue chambers was studied in healthy adult ponies. Six ponies were given an oral TMP/SDZ paste formulation at a dose of 5 mg/kg TMP and 25 mg/kg SDZ at 12 h intervals for 2 days in order to reach steady-state concentrations. Plasma concentrations and tissue chamber fluid (TCF) concentrations of both drugs were measured at regular intervals during a period commencing 24 h after the last oral administration. The peak concentration of TMP (mean +/- SD) was 2.92 +/- 0.86 microg/mL for plasma a...
Oukessou M, Alsouss L.The body disposition of sulfadimidine (SDM), sulfadiazine (SDZ), sulfamethoxypyridazine (SMPZ) and a trimethoprim-sulfadimethoxine combination (TMP-SDMX) was investigated in the donkey. The four sulfonamides and TMP were injected intravenously at doses of 20 mg/kg (SDM, SDZ, SMPZ), 12.5 mg/kg (SDMX) and 2.5 mg/kg (TMP). The body clearance (ClB) of SDZ (1.70 +/- 0.14 ml/min/kg) was significantly higher than those of SDM (1.13 +/- 0.18 ml/min/kg), SMPZ (1.10 +/- 0.09 ml/min/kg) and SDMX (0.75 +/- 0.04 ml/min/kg). In contrast, the volume of distribution at steady state (Vss) was similar for the f...
Fey K, Weiss R, Sasse HH.Both, the oral and intravenous application of two trimethoprim-potentiated sulfonamides induced measurable antibacterial activities in the feces of horses. With regard to the risk of antibiotic-induced alterations of the gastrointestinal flora, the route of application of potentiated sulfonamides seems to be of minor importance. The antibiotics used were Sulfadimethoxine/Trimethoprim (Trafigal 30% ad us. vet.) for oral and Sulfadoxine/Trimethoprim (Borgal 24% ad us. vet., both Hoechst AG, Frankfurt) for intravenous application. As recommended, both drugs were given in a dose of 20 mg per kg bo...
Freestone JF, Paccamonti DL, Eilts BE, McClure JJ, Swiderski CE, Causey RC.A 5-year-old stallion was referred because of signs of abdominal pain. During the initial examination, signs of pain were elicited when the right seminal vesicle was palpated per rectum. Signs of pain were also elicited during sexual arousal and attempts at semen collection. The right seminal vesicle was subsequently determined to be abnormal by ultrasonographic and endoscopic examination. The stallion was treated with trimethoprim/sulfamethoxazole for 6 weeks. Five months later, there had been no recurrence of the condition.
Brown MP, McCartney JH, Gronwall R, Houston AE.Six healthy two-day-old foals (3 pony foals and 3 horse foals) were given a single intravenous (iv) injection of trimethoprim (TMP)--sulphamethoxazole (SMZ) at a dosage of 2.5 mg of TMP/kg bodyweight (bwt) and 12.5 mg of SMZ/kg bwt. Serum TMP and SMZ concentrations were measured serially during a 24 hour period. The overall elimination rate constant (K) for TMP in the pony and horse foals was 0.45/h, whereas the K values for SMZ for the pony and horse foals were 0.12/h and 0.07/h, respectively (no significant difference; P greater than 0.05). Based on published minimum inhibitory concentration...
Brown MP, Gronwall R, Castro L.Six healthy adult mares were each given a single IV injection of trimethoprim (TMP)-sulfamethoxazole (SMZ) at a dosage of 2.5 mg of TMP/kg of body weight and 12.5 mg of SMZ/kg. Serum concentrations of each drug were measured serially over a 24-hour period. For TMP, the mean overall elimination rate constant (K) was 0.43/hr and the elimination half-life (t1/2) was 1.9 hours. The apparent volume of distribution (at steady state) was 1.62 L/kg and TMP clearance was 886 ml/hr/kg. For SMZ, K was 0.22/hr and t1/2 was 3.53 hours. The apparent volume of distribution at steady state was 0.33 L/kg and S...
Johnston JK, Neely DP, Latterman SA.A 4.5-month-old Standard-bred filly was referred for evaluation of pigmenturia. Initially, the pigmenturia had resolved with the administration of antibiotics, only to recur after their withdrawal. A dark red urine sample contained numerous RBC, WBC, and gram-negative rods (Escherichia coli). Ultrasonography revealed the right kidney to be large, with multiple cystic structures and a dilated renal pelvis and calices. Cystoscopy revealed a large blood clot within the bladder and urine coming from the left ureteral opening. Urine was not observed coming from the right ureter. It was suspected th...
Sweeney CR, Sweeney RW, Divers TJ.Case records of 48 foals with pneumonia due to Rhodococcus equi were reviewed. Twenty of the 48 foals survived and 28 died or were euthanized. There was no significant difference between the survivors and non-survivors in the age of onset of illness, duration of illness prior to admission, the mean white blood cell (WBC) count, or the mean plasma fibrinogen content. All foals had R. equi isolated from a tracheobronchial aspirate or lung specimens obtained at necropsy. All organisms were susceptible in vitro (Kirby-Bauer) to erythromycin and gentamicin. Susceptibilities to other drugs were: tri...
Prescott JF, Sweeney CR.Combined antimicrobial drug treatment was recommended for foals with Corynebacterium equi pneumonia. The preferred combination is orally administered erythromycin estolate (25 mg/kg of body weight, QID) plus rifampin (10 mg/kg, BID). Erythromycin estolate also can be combined for synergistic effect with sodium benzyl penicillin given IV (100,000 IU/kg, QID) or with ampicillin given IV (11 to 15 mg/kg, QID). A third choice is sodium benzyl penicillin IV with gentamicin IM (2.2 mg/kg, TID) or with kanamycin IM (10 mg/kg, QID). Gentamicin should be combined with penicillin G or ampicillin and not...
Sigel CW, Byars TD, Divers TJ, Murch O, DeAngelis D.Two fasted and 2 fed horses were dosed orally with a combined trimethoprim and sulfadiazine paste formulation at a dose of 35 mg (1:5 combined active ingredients)/kg. Serum concentrations of each drug were determined periodically for 3 consecutive days for the 4 horses. The extent and rate of absorption for trimethoprim were variable, but peak serum concentrations occurred generally within 3 hours; sulfadiazine absorption was slower, reaching peak concentrations by 6 hours. Fasting did not have a consistent effect on the serum concentration profiles for either drug. Both drugs achieved serum c...
Ribeiro MG, de Morais ABC, Alves AC, Bolaños CAD, de Paula CL, Portilho FVR, de Nardi Júnior G, Lara GHB, de Souza Araújo Martins L, Moraes LS....Klebsiella species, particularly K. pneumoniae, are well-known opportunistic enterobacteria related to complexity of clinical infections in humans and animals, commonly refractory to conventional therapy. The domestic animals may represent a source of the pathogenic and multidrug-resistant Klebsiella species to humans. Nevertheless, most studies involving Klebsiella-induced infections in domestic animals are restricted to case reports or outbreaks. We retrospectively investigated selected epidemiological data, clinical aspects, and in vitro susceptibility pattern of 697 non-repetitive Klebsiel...
Prescott JF, Sweeney CR.Combined antimicrobial drug treatment was recommended for foals with Corynebacterium equi pneumonia. The preferred combination is orally administered erythromycin estolate (25 mg/kg of body weight, QID) plus rifampin (10 mg/kg, BID). Erythromycin estolate also can be combined for synergistic effect with sodium benzyl penicillin given IV (100,000 IU/kg, QID) or with ampicillin given IV (11 to 15 mg/kg, QID). A third choice is sodium benzyl penicillin IV with gentamicin IM (2.2 mg/kg, TID) or with kanamycin IM (10 mg/kg, QID). Gentamicin should be combined with penicillin G or ampicillin and not...
Winther L, Guardabassi L, Baptiste KE, Friis C.Sulfadiazine (SDZ) and trimethoprim (TMP) concentrations were examined in plasma and pulmonary epithelial lining fluid (PELF), following intravenous and oral administration and compared to minimum inhibitory concentrations (MICs) of common bacterial isolates from equine lower airway infections. SDZ/TMP (25/5 mg/kg) was administered intravenously, intragastric or per os to fed horses, and blood samples were collected before and 11 times, over 24 h, after administration. PELF samples were collected via a tampon device four times after drug administration and analysed for drug concentrations. Add...
van Duijkeren E, Ensink JM, Meijer LA.The distribution of trimethoprim (TMP) and sulfadiazine (SDZ) into subcutaneously implanted noninfected tissue chambers was studied in healthy adult ponies. Six ponies were given an oral TMP/SDZ paste formulation at a dose of 5 mg/kg TMP and 25 mg/kg SDZ at 12 h intervals for 2 days in order to reach steady-state concentrations. Plasma concentrations and tissue chamber fluid (TCF) concentrations of both drugs were measured at regular intervals during a period commencing 24 h after the last oral administration. The peak concentration of TMP (mean +/- SD) was 2.92 +/- 0.86 microg/mL for plasma a...
Brown MP, Gronwall R, Castro L.Six healthy adult mares were each given a single IV injection of trimethoprim (TMP)-sulfamethoxazole (SMZ) at a dosage of 2.5 mg of TMP/kg of body weight and 12.5 mg of SMZ/kg. Serum concentrations of each drug were measured serially over a 24-hour period. For TMP, the mean overall elimination rate constant (K) was 0.43/hr and the elimination half-life (t1/2) was 1.9 hours. The apparent volume of distribution (at steady state) was 1.62 L/kg and TMP clearance was 886 ml/hr/kg. For SMZ, K was 0.22/hr and t1/2 was 3.53 hours. The apparent volume of distribution at steady state was 0.33 L/kg and S...
Johnston JK, Neely DP, Latterman SA.A 4.5-month-old Standard-bred filly was referred for evaluation of pigmenturia. Initially, the pigmenturia had resolved with the administration of antibiotics, only to recur after their withdrawal. A dark red urine sample contained numerous RBC, WBC, and gram-negative rods (Escherichia coli). Ultrasonography revealed the right kidney to be large, with multiple cystic structures and a dilated renal pelvis and calices. Cystoscopy revealed a large blood clot within the bladder and urine coming from the left ureteral opening. Urine was not observed coming from the right ureter. It was suspected th...
Smith MA, Ross MW.To determine features of postoperative wound infection caused by Actinobacillus spp in horses undergoing clean, elective surgery and to evaluate bacterial susceptibility profiles of bacteria isolated. Methods: Retrospective study. Methods: 10 horses. Methods: Data were retrieved from medical records and the microbiology laboratory database. Results: 1,604 horses underwent clean, elective surgical procedures during the study period. Of these, 23 (1.43%) had postoperative wound infections, and Actinobacillus spp was isolated from 10 of these 23 (43%). Surgical procedures in these 10 horses inclu...
Brown MP, McCartney JH, Gronwall R, Houston AE.Six healthy two-day-old foals (3 pony foals and 3 horse foals) were given a single intravenous (iv) injection of trimethoprim (TMP)--sulphamethoxazole (SMZ) at a dosage of 2.5 mg of TMP/kg bodyweight (bwt) and 12.5 mg of SMZ/kg bwt. Serum TMP and SMZ concentrations were measured serially during a 24 hour period. The overall elimination rate constant (K) for TMP in the pony and horse foals was 0.45/h, whereas the K values for SMZ for the pony and horse foals were 0.12/h and 0.07/h, respectively (no significant difference; P greater than 0.05). Based on published minimum inhibitory concentration...
Sigel CW, Byars TD, Divers TJ, Murch O, DeAngelis D.Two fasted and 2 fed horses were dosed orally with a combined trimethoprim and sulfadiazine paste formulation at a dose of 35 mg (1:5 combined active ingredients)/kg. Serum concentrations of each drug were determined periodically for 3 consecutive days for the 4 horses. The extent and rate of absorption for trimethoprim were variable, but peak serum concentrations occurred generally within 3 hours; sulfadiazine absorption was slower, reaching peak concentrations by 6 hours. Fasting did not have a consistent effect on the serum concentration profiles for either drug. Both drugs achieved serum c...
Oukessou M, Alsouss L.The body disposition of sulfadimidine (SDM), sulfadiazine (SDZ), sulfamethoxypyridazine (SMPZ) and a trimethoprim-sulfadimethoxine combination (TMP-SDMX) was investigated in the donkey. The four sulfonamides and TMP were injected intravenously at doses of 20 mg/kg (SDM, SDZ, SMPZ), 12.5 mg/kg (SDMX) and 2.5 mg/kg (TMP). The body clearance (ClB) of SDZ (1.70 +/- 0.14 ml/min/kg) was significantly higher than those of SDM (1.13 +/- 0.18 ml/min/kg), SMPZ (1.10 +/- 0.09 ml/min/kg) and SDMX (0.75 +/- 0.04 ml/min/kg). In contrast, the volume of distribution at steady state (Vss) was similar for the f...
Johnston GCA, Lumsden JM.To describe the prevalence and antimicrobial susceptibility of bacterial isolates cultured from surgical specimens of infected arytenoid cartilage and granulomas. Methods: Retrospective cohort study. Methods: Thirty-three thoroughbred horses. Methods: Hospital records were retrieved for all horses admitted to a referral hospital for arytenoid chondropathy surgery that had samples submitted for culture and sensitivity between 2005 and 2019. Descriptive analyses were performed. Results: In total, 56 bacterial isolates were obtained. Gram-positive bacteria (58%), Gram-negative bacteria (54%), and...
Fey K, Weiss R, Sasse HH.Both, the oral and intravenous application of two trimethoprim-potentiated sulfonamides induced measurable antibacterial activities in the feces of horses. With regard to the risk of antibiotic-induced alterations of the gastrointestinal flora, the route of application of potentiated sulfonamides seems to be of minor importance. The antibiotics used were Sulfadimethoxine/Trimethoprim (Trafigal 30% ad us. vet.) for oral and Sulfadoxine/Trimethoprim (Borgal 24% ad us. vet., both Hoechst AG, Frankfurt) for intravenous application. As recommended, both drugs were given in a dose of 20 mg per kg bo...
Freestone JF, Paccamonti DL, Eilts BE, McClure JJ, Swiderski CE, Causey RC.A 5-year-old stallion was referred because of signs of abdominal pain. During the initial examination, signs of pain were elicited when the right seminal vesicle was palpated per rectum. Signs of pain were also elicited during sexual arousal and attempts at semen collection. The right seminal vesicle was subsequently determined to be abnormal by ultrasonographic and endoscopic examination. The stallion was treated with trimethoprim/sulfamethoxazole for 6 weeks. Five months later, there had been no recurrence of the condition.
Ekstrand C, Nostell K, Gehring R, Bondesson U, Bröjer J.Septicaemia in the neonatal foal is caused by both Gram positive and Gram negative bacteria. The life-threatening nature of this condition requires treatment to be initiated with broad spectrum antimicrobial drugs pending antimicrobial susceptibility testing. Potentiated sulphonamides, for example, trimethoprim combined with sulfadiazine, could be clinically relevant options but their pharmacokinetics in the neonatal foal are unknown. To describe the plasma disposition of trimethoprim and sulfadiazine in neonatal foals and to relate the results to patterns in the minimum inhibitory concentrati...
Sweeney CR, Sweeney RW, Divers TJ.Case records of 48 foals with pneumonia due to Rhodococcus equi were reviewed. Twenty of the 48 foals survived and 28 died or were euthanized. There was no significant difference between the survivors and non-survivors in the age of onset of illness, duration of illness prior to admission, the mean white blood cell (WBC) count, or the mean plasma fibrinogen content. All foals had R. equi isolated from a tracheobronchial aspirate or lung specimens obtained at necropsy. All organisms were susceptible in vitro (Kirby-Bauer) to erythromycin and gentamicin. Susceptibilities to other drugs were: tri...
Braga PRC, Dos Santos CA, Bertani AMJ, Vieira T, Amarante AF, Reis AD, Sacchi CT, Camargo CH, Ribeiro MG, Borges AS, Tiba-Casas MR.This study reports the genomic characterization of the multidrug resistant Salmonella Newport strain 195_20 recovered from the diarrheic faeces of a foal in Brazil and co-harbouring the mcr-9, blaCMY-2 and qnrB19 antibiotic resistance genes. Bacterial isolate positive for mobile colistin resistance gene (mcr-9) was submitted to antimicrobial susceptibility testing by disk diffusion and broth microdilution for colistin and polymyxin B. The isolate was submitted to whole genome sequencing by Illumina technology and Nanopore Sequencing. Conjugation assays, plasmid sizes determined by S1-PFGE and ...
