Tetracycline Series Research Articles

Dependence of treatment effectiveness in dogs ticke-borreliosis from the time of diagnosis

The importance and necessity of confirming the diagnosis of tick-borne borreliosis (Lyme disease) in dogs at the initial stages is due to the possibility of timely prescribing specific treatment and reducing the recovery time of animals. In the conditions of a veterinary clinic in St. Petersburg, tick-borne borreliosis was diagnosed in dogs, taking into account the parasitism of ixodid ticks, erythema at the site of their attachment, depression, lowgrade fever, anorexia, lameness, paraplegia, and confirmed by the PCR. In dogs of one of the experimental groups, after removing the ticks, the Borrelia Test test system was used to detect the pathogen Borrelia burgdorferi. Dogs were treated with tertacycline preparations - "Doxycycline", "Doxyfin" and fluoroquinolones - "Enroflaxocin". It was found that the oral administration of drugs "Doxycycline" and "Doxyfin" to dogs at the rate of 10 mg / kg of animal weight, 1 time per day, for 28 days is equally effective in Lyme disease. The alternation of the use of bacteriostatic antibiotics of the tetracycline series and fluoroquinolones has a greater therapeutic efficacy compared to the use of only drugs of the tetracycline group. The use of drugs "Enroflaxocin" and "Doxycycline" reduced the recovery time of animals to three weeks compared to 28 days when animals were treated only with tetracycline antibiotics. The early timing of the detection of borrelia in ixodid ticks made it possible to timely prescribe treatment to animals. In dogs of this group, it was possible to avoid the development of a severe course of tick-borne borreliosis, accompanied by a long period of fever, the development of signs of anorexia, depression, lameness, and the use of drugs from the fluoroquinolones and tetracyclines groups reduced the recovery time of animals to two weeks

A Selective Fluorescent Nanoprobe Based on Graphene Quantum Dots and Hg2+ for the Determination of Tetracycline in Biological Samples.

A simple, sensitive, and selective fluorometric method based on graphene quantum dots and Hg2+ is presented for the determination of tetracycline. The fluorescence emission of graphene quantum dots at 463nm decreased in the presence of Hg2+ ions due to its electrostatic interaction with the negatively charged surface of quantum dots at pH = 8.0. The addition of tetracycline to this system resulted in the retrieval of the fluorescence emission of the graphene quantum dots proportional to the tetracycline concentration. This is because of the interaction between tetracycline and Hg2+ that results in the release of the quantum dots' surface. Under the optimized conditions, the calibration curve indicated good linearity in the range of 2.0-44.0nmol L-1 with a detection limit of 0.52nmol L-1 for tetracycline. The designed nanoprobe was capable of the determination of tetracycline in serum and urine samples.

Facile In-Situ Synthesis of Biopolymer Capped Nano Sized Silver Particles: Smartphone Aided Paper-Based Selective Detection of CYS and TC Drugs in Biological and Drug Samples

Herein we are reporting, the in-situ synthesis of polydopamine capped silver nanoparticles (PDA-AgNPs) and its cysteamine (CYS) and tetracycline (TC) drugs sensor applications. The synthesized PDA-AgNPs was characterized by UV–Visible, Fourier Transformed–Infrared, X-Ray Diffraction, Zeta Potential, and High Resolution-Transmission Electron Microscope techniques. We have utilized PDA-AgNPs as probes for the detection of CYS and TC by spectrophotometry method. The addition of CYS has led to a decrease in the absorption of PDA-AgNPs. The yellow color solution becomes colorless and observed the aggregated particles in the TEM image. In contrast, the addition of TC, into the same solution, absorption of PDA-AgNPs was increased. The color of the solution became dark yellow and the particles are obtained de-aggregation. Based on the Surface Plasmon Resonance (SPR) band absorption changes, the detection limit of CYS and TC was calculated to be 180 nM and 17 nM, respectively. Interestingly, 600-fold of common interferences did not interfere with the detection of CYS and TC. PDA-AgNPs was successfully utilized to detect CYS and TC in serum, urine, and drug samples. Finally, we have prepared a paper-based colorimetric kit for on-site monitoring of CYS and TC.

Enhancement of gold nanoclusters-based peroxidase nanozymes for detection of tetracycline

Gold nanoclusters (AuNCs) have shown great potential in mimicking the redox properties of nanozymes. However, limited fundamental knowledge and a lack of an effective means have hindered the enhancement of their catalysis efficiency. In this study, we report a simple protocol for the synthesis of D-trytophan methyl ester protected AuNCs and exhibit their peroxidase-like activity in a chromogenic reaction coupling with 3,3′,5,5′-tetramethylbenzidine-H2O2. Interestingly, the addition of tetracycline resulted in a remarkable acceleration of the redox reaction rate with AuNCs as the nanozymes due to the increased levels of reactive oxygen species. The UV–vis adsorption intensity of oxidized 3,3′,5,5′-tetramethylbenzidine presented a good linear relationship with the concentration of tetracycline in the range of 1.5–30.0 µM and the limit of detection of the method was 0.2 µM. The proposed assay was further applied in the analysis of serum tetracycline. This study enriches our basic understanding of the enhancement of the catalytic efficiency of AuNCs-based nanozymes.

Сравнительная эффективность сорбентов при выведении антибиотиков из организма цыплят-бройлеров для получения экологически чистой продукции

Comparative tests on the removal of doxycycline hydrochloride, the tetracycline series antibiotic, from the body of broiler chickens using Belvetsorb and Ultrasorb enterosorbents after oral application for 5 days in a therapeutic and prophylactic dose were carried out. Already on the 4th day after cessation of antibiotic feeding was observed across more intense decreasing of the concentration of doxycycline in the meat of chickens treated with Belvetsorb food, Ultrasorb food and Ultrasorb with water (65.6% to 80% and 81%, respectively). This trend continued in the subsequent period after the end of the use of doxycycline hydrochloride (from 10 to 13 days). On the 14th day after stopping the drinking of doxycycline hydro-chloride, there was a significantly more intense decrease in the antibiotic content in the meat of chickens receiving Belvetsorb with feed, Ultrasorb with feed and especially, Ultrasorb with water (15.7%, 19.4% and 76.3%, respectively). Limit content in meat and meat products doxycycline should be less than 0.1 mg/kg. The tests identified the most rapid excretion of doxycycline when administered to chickens sorbent "Ultrasorb" method of feeding. The use of the sorbent "Ultrasorb" by the method of drinking leads to the content of residual amounts of doxycycline in the meat of broiler chickens to an acceptable level for 10 days after the end of antibiotic use, the use of Ultrasorb and Belvetsorb with feed – for 12 days and 13 days, respectively. In the control group without the use of drugs, the permissible level of doxycycline in broiler meat was achieved only on day 14. Thus, the use of these drugs and, first of all, Ultrasorb with water can be recommended to reduce the waiting period after the use of tetracycline antibiotics in poultry farming. Further research will be aimed at studying the effect of sorbents on reducing the waiting period after the use of other tetracycline antibiotics, as well as other classes of antibiotics that are removed from the body mainly unchanged with faeces and urine

Effect of Soil Organic Matter Content on Uptake of Four Veterinary Antibiotics by Pepper

The objectives of this study were to investigate the effect of soil organic matter content on the accumulation of veterinary antibiotics in pepper (Capsicum annuum L.) and the effect of antibiotic concentrations on culturable soil-borne bacteria. Soils containing 0%, 5%, or 10% (vol/vol) organic matter content were prepared using coir dust. Four veterinary antibiotics: sulfamethoxazole, sulfamethazine (sulfonamide series), oxytetracycline, and chlortetracycline (tetracycline series), commonly used in Korea were selected for this study. Antibiotic mixtures of equal amount of each antibiotic were used to spike the soil to achieve concentrations of 0, 1, 5, and 10 mg kg−1, respectively. Pepper cultivated for 2 weeks after sowing was transplanted into pots filled with soil treated with organic matter and antibiotics. After 8 weeks, pepper roots, leaves, and fruits were harvested, and antibiotic concentrations in the soil and pepper plants were analyzed. Concentrations of the tetracycline series in soil were higher than those of the sulfonamide series. The amount of sulfonamide series antibiotics transferred to pepper roots increased with increasing organic matter content in the soil, whereas no significant difference was observed in oxytetracycline and chlortetracycline concentrations in roots. Under all organic matter treatments, the microbial activity in soil decreased when antibiotic concentrations increased. For a given antibiotic concentration, the number of culturable soil-borne bacteria increased as the organic matter content increased.

Regional monitoring of the urinary tract infections causative agents antibiotic resistance in the child population of the Chernivtsi region

In the scope of current medical practice the “viewpoint” regarding the growth of antibiotic resistance of microorganisms is a threat to national security. A reasonable use of antibiotics on the basis of uropathogen regional bacterial sensitivity gives the opportunity to “restrain” the growth of antibiotic resistance of microorganisms and increase the effectiveness of the UTI treatment.The aim of the article is to determine the range and dynamics of the antibiotic resistance of major groups of infectious-inflammatory diseases causative agents of the urinary tract in the child population of the Chernivtsi region.Materials and methods. The analysis of etiologic spectrum and antibiotic resistance of uropathogens was conducted and observed in the urine samples of 657 patients who were provided with a specialized medical care in the Nephrology department of the “Municipal Children’s Clinical Hospital”, Chernivtsi (2014–2015) with the purpose of the dynamic control of possible changes in the regional antibiotic resistance of pathogens of causative pathogens of the “urinary tract infections” (UTI); identify the age and gender differences of the child population of the Chernivtsi region (2014–2015) compared to the monitoring data for the period of 2009–2013.Results. When UTI among of the child population of the Chernivtsi region leading etiologic organisms include strains of the family Enterobacteriaceae and uropathogen of the genus Proteus. A “wave-like” curve of the dynamics of antibiotic resistance of Enterobacteriaceae uropathogens with a decreasing tendency to the “drugs of choice” was observed among the child population of the region (2009–2015): penicillin (p < 0.01), cephalosporin II–III generation (p < 0.01) and medicine of the fluoroquinolone series (p < 0.01). A “wave-like” curve of the dynamics of antibiotic resistance of Proteus uropathogens with a decreasing tendency to the “drugs of choice” was observed among the child population of the region (2009–2015): semi-synthetic penicillin (p < 0.1), and medicine of the tetracycline series (p < 0.01).Conclusions. Regional microbiological monitoring of the uropathogens is an effective “tool” in higher quality treatment of infectious and inflammatory diseases of the urinary tract of the child population.

ЕФЕКТИВНІСТЬ «МАЗІ ДЛЯ РАН» У КОМПЛЕКСНІЙ ТЕРАПІЇ ПРИ ЛІКУВАННІ РВАНИХ РАН ДІЙОК ВИМЕНІ КОРІВ

In the study of cows’ mammary glands pathologies it was determined that the udder wounds constitute 1.2% in the overall structure of diseases. The peak of traumatism on cows’ breast wounds falls on summer (pasture–range period) – 77.3%, resulting from offences of sanitary requirements for cattle pasture and grazing. While testing new treatment regimens it was set the high efficiency of «Ointments for wounds» based on essential oils of Siberian Cedar, Eucalyptus, Clove, Cedar, Tea Tree and chlorophyllipt oil solution for treatment of avulsive wounds of cows’ udder teats. It has been proven the reducing of time for treatment compared with traditional drugs «Oxytetracycline Ointment 5%» containing oxytetracycline – a semisynthetic antibiotic of a tetracycline series. Complex therapy, including application of preparation for external use «Ointment for wounds» and hypodermic injection of NSAID «Celecoxib», together with the wound defects closing by sutures with polyglycolide, promotes rapid correction of the clinical condition of cows. It was observed upregulating of hemoglobin by 6.1%, the number of erythrocytes – 11.4%, leukocytes – 9% in the blood, compared with the traditional method of treatment («Oxytetracycline Ointment 5%» and nonsteroidal drug «Kefen»). Local application of phytopreparation «Ointments for wounds» and hypodermic injection of NSAID «Celecoxib» promotes acceleration of inflammatory reactions cancellation in 1,3 times, reduce udder edema – 1.2 times and enhance regenerative processes, thereby reducing treatment time 5 – 6 days compared to control animals.

A novel colorimetric triple-helix molecular switch aptasensor for ultrasensitive detection of tetracycline

Detection methods of antibiotic residues in blood serum and animal derived foods are of great interest. In this study a colorimetric aptasensor was designed for sensitive, selective and fast detection of tetracycline based on triple-helix molecular switch (THMS) and gold nanoparticles (AuNPs). As a biosensor, THMS shows distinct advantages including high stability, sensitivity and preserving the selectivity and affinity of the original aptamer. In the absence of tetracycline, THMS is stable, leading to the aggregation of AuNPs by salt and an obvious color change from red to blue. In the presence of tetracycline, aptamer binds to its target, signal transduction probe (STP) leaves the THMS and adsorbs on the surface of AuNPs. So the well-dispersed AuNPs remain stable against salt-induced aggregation with a red color. The presented aptasensor showed high selectivity toward tetracyclines with a limit of detection as low as 266 pM for tetracycline. The designed aptasensor was successfully applied to detect tetracycline in serum and milk.

Pharmacokinetics of tetracycline hydrochloride after single intravenous injection in dogs

Summary Six mixed-breed apparently healthy dogs were intravenously administered a single dose of tetracycline hydrochloride (50 mg/kg) to evaluate the pharmacokinetic parameters of the drug. Blood samples were collected before and at various time intervals after the administration of the drug. Serum tetracycline concentrations were determined over a 24 h period using fluorescence spectrophotometry. Noncompartmental analysis of the data indicated that tetracycline has a half-life of 4.4 h, a body clearance of around 0.7 ml/kg.min and a volume of distribution of about 0.3 L/kg. The pharmacokinetics of tetracycline found in this study is favourable for therapeutic use in the dog.

Susceptibility of bacteria from feline and canine urinary tract infections to doxycycline and tetracycline concentrations attained in urine four hours after oral dosage

To measure urinary concentrations of doxycycline in cats and dogs and tetracycline in dogs 4 h after conventional oral dosing and determine whether these antibiotics were present in sufficient concentrations to be effective against common feline and canine urinary tract pathogens as assessed in vitro by Epsilometer and disc diffusion antimicrobial susceptibility methods. A prospective study involving oral administration to clinically normal cats and dogs of doxycycline or tetracycline (dogs only) and culture of bacteria from dogs and cats with urinary tract infections to determine their susceptibility to both doxycycline and tetracycline in vitro. In the first study, nine cats and eight dogs were administered doxycycline monohydrate (5 mg/kg every 12 h) and a further eight dogs were administered tetracycline hydrochloride (20 mg/kg every 8 h) for 72 h. Blood was collected at 2 and 4 h, and urine at 4 h, after the last dose. The concentration of each agent in serum and urine was determined by modified agar diffusion. In the second study, 45 urine samples from cats and dogs with urinary tract infections were cultured. Every bacterial isolate was tested in vitro using both Epsilometer (doxycycline and tetracycline) and disc diffusion (doxycycline, tetracycline or amoxycillin-clavulanate) tests. Serum doxycycline concentrations in sera of cats and dogs at 2 h were 4.2 +/- 1.0 mg/mL and 3.4 +/- 1.1 mg/mL, respectively. The corresponding concentrations at 4 h were 3.5 +/- 0.7 mg/mL and 2.8 +/- 0.6 mg/mL. Urinary doxycycline concentrations at 4 h (53.8 +/- 24.4 mg/mL for cats and 52.4 +/- 24.1 mg/mL for dogs) were substantially higher than corresponding serum values. Serum tetracycline concentrations in dogs at 2 and 4 h, and in urine at 4 h, were 6.8 +/- 2.8, 5.4 +/- 0.8, 144.8 +/- 39.4 mg/mL, respectively. Most of the urinary tract pathogens (35/45) were susceptible to urinary concentrations of doxycycline and 38/45 were susceptible to tetracycline. In contrast 41/45 of all isolates were susceptible to amoxycillin-clavulanate. This is the first report of urinary concentrations of doxycycline after conventional oral administration. Concentrations attained in the urine of normal cats and dogs were sufficient to inhibit the growth of a significant number of urinary tract pathogens and thus doxycycline may be a useful antimicrobial agent for some urinary tract infections.

Pharmacokinetic Study on Interaction Between Tetracycline and Aspirin

Rajaian, H. Jalaei, J. and Razmjou, A. 2004. Pharmacokinetic study on interaction between tetracycline and aspirin. J. Appl. Anim. Res., 25: 117–120. To understand the mechanism involved in interaction between aspirin and tetracycline, six mixed breed dogs were premedicated with acetyl-promazine. Tetracycline hydrochloride was administered intravenously at various stages: first, tetracycline alone, second, immediately after intravenous injection of salicylic acid and third, three hours following oral administration of aspirin. Blood samples were collected during 6h after administration of tetracycline. The concentration of tetracycline was higher when it was administered alone compared with when it was given after oral aspirin or with salicylic acid. Serum tetracycline concentration was more rapidly approached to the minimum when it was administered in conjunction with salicylic acid. In addition, the area under the curve for serum tetracycline concentration versus time (AUC) was smaller compared to when tetracycline was administered alone. Furthermore, when aspirin was given orally prior to intravenous administration of tetracycline, the rate of decline in serum tetracycline concentration was less and AUC was higher compared to when it was injected alone. An increase in the unbound form of tetracycline molecules may be involved which is possibly due to competition between tetracycline and salicylic acid or aspirin for plasma protein binding sites. As the underlying mechanism(s) will have pharmacokinetic impact, which may be important from clinical pharmacology point of view, further in vivo and in vitro studies should be carried out to elucidate the exact nature of this drug interaction.

Simultaneous determination of ciprofloxacin and tetracycline in biological fluids based on dual-lanthanide sensitised luminescence using dry reagent chemical technology

Terbium(III) and europium(III) have been used as dry reagents for the simultaneous determination of ciprofloxacin and tetracycline in serum and urine samples. These lanthanide ions were immobilised by adsorption in paper strips, which were previously treated with sucrose. The terbium(III)-ciprofloxacin chelate presents an intense luminescence at λ ex=284 nm and λ em=545 nm and the europium(III)-tetracycline chelate does it at λ ex=395 nm and λ em=615 nm. Luminescence measurements have been performed using the time-resolved mode. The linear ranges of the calibration graphs using standard solutions are 0.03–1.5 μg ml −1 for ciprofloxacin and 0.03–2.5 μg ml −1 for tetracycline and the calculated 3 σ detection limits are 9 and 11 ng ml −1, for ciprofloxacin and tetracycline, respectively. Quantification limits (10 σ) in the original human urine and serum samples were 125 and 1.3 μg ml −1, respectively, for ciprofloxacin, and 75 and 0.8 μg ml −1, respectively, for tetracycline. The features of the dry reagent method have been compared to those provided by the measurements carried out in solution. Mixtures of ciprofloxacin and tetracycline ranged in weight ratios between 5:1 and 1:10 were satisfactorily resolved with errors <6% using the dry reagent method, which was applied to the analysis of several serum and urine samples with recoveries ranging from 88.7 to 109.3%.

Tetracycline delivery from fibrin controls peritoneal infection without measurable systemic antibiotic.

The addition of antibiotics to an adhesive haemostat results in an ideal system for the treatment of a localized infectious disease. Fibrin sealant (FS) is a biocompatible, resorbable, adherent haemostat that can deliver antibiotics. Previous use of fibrin to deliver antibiotics resulted in rapid release and limited bioactivity. We have reported previously that poorly soluble antibiotics significantly retard release from FS, resulting in extended delivery in vitro, and overcome antibiotic-resistant infection. We now report that localized antibiotic delivery from FS controls peritoneal infection without measurable systemic antibiotic. Rats and mice were implanted with preformed FS discs containing tetracycline free-base to evaluate control of peritoneal sepsis and to measure serum tetracycline levels. Infection was initiated with Staphylococcus aureus. Morbidity and mortality were evaluated for 14 days. Serum was isolated from jugular vein blood with subsequent evaluation for antimicrobial activity. Mice prophylactically treated with FS-tetracycline (FS-TET) 500 mg/kg 2 days before infection cleared the S. aureus infection, resulting in 100% survival. Mice treated with FS-TET 500 mg/kg 7 days before infection survived. Mice treated with FS-TET 1750 mg/kg 35 days before infection also survived. Rats treated with FS-TET 500 mg/kg had undetectable serum tetracycline levels, whereas in vitro release of tetracycline from FS-TET pellets in rat serum was readily detected. We conclude that fibrin is an excellent vehicle for extended delivery of low solubility tetracycline. Tetracycline delivered from FS is an appropriate chemotherapy for S. aureus peritonitis. FS-TET controls localized infection without a measurable concentration of systemic tetracycline.

Uptake of tetracycline by aortic aneurysm wall and its effect on inflammation and proteolysis.

Proteolytic degradation of the aortic wall by matrix metalloproteinases (MMPs) is considered important in the pathogenesis of abdominal aortic aneurysms (AAAs). Many of these MMPs are inhibited by tetracycline derivatives, which may have the potential to retard aneurysm growth. Patients undergoing elective repair of an AAA (n = 5) received an intravenous bolus of tetracycline (500 mg) on induction of anaesthesia and levels of tetracycline in serum, aneurysm wall and mural thrombus were assessed by microbiological assay. In a separate series of patients (n = 7) aneurysm biopsies were placed into explant culture (with and without tetracyline) and the accumulation of protein, hydroxyproline, MMP-9, interleukin (IL) 6 and monocyte chemoattractant protein (MCP) 1 in the medium was assessed by colorimetric assay or immunoassay. At aortic cross-clamping the median concentration of tetracycline was 8.3 microg/ml in serum, 2.9 microg per g tissue in aortic wall and zero in mural thrombus. Tetracycline inhibited, in a concentration-dependent manner, both MMP-9 and MCP-1 secretion (P = 0.022 and P = 0.018 respectively), but did not alter hydroxyproline or IL-6 secretion. At the highest concentration of tetracycline (100 microg/ml) median MMP-9 secretion was reduced from 27 to 5 ng/ml (P = 0.007) and median MCP-1 secretion was reduced from 50 to 10 ng/ml (P = 0.008). Tetracycline rapidly penetrates the aortic wall, but the concentration achieved may be insufficient to alter collagen turnover through limitation of MMP production or activity.

Simultaneous determination of five antibiotics by ion-pair high-performance liquid chromatography

This paper presents new information on the isocratic assay of five antibiotics thereby condensing five different assay procedures to one single report. Five antibiotics, viz., cephalexin and cefaclor (cephalosporins), isoniazid and pyrazinamide (anti-tubercular drugs) and minocycline (tetracycline series) have been separated and estimated from mixtures using a mobile phase consisting of tetrabutylammonium hydrogensulphate (0.025 M), methanol–acetonitrile (96:2:2) with pH adjusted to 3.0 with triethylamine. Column used was a Metaphase-CrestPak-ODS (250×4.0 mm, 5 μm), with a flow-rate of 1.5 ml min −1, with detection at 248 nm. The retention order was isoniazid (2.68 min), minocycline (5.79 min), pyrazinamide (6.89 min), cephalexin (8.50 min) and cefaclor (12.18 min). The composition and polarity of the mobile phase was found to be critical, not for individual drugs, but for mixtures. The linear dynamic range was 0.30–10.00 μg ml −1. Any one of the drugs could be used as internal standard for the other four drugs. All the drugs gave sharp, well-resolved peaks with optimum chromatographic figures of merit. Analytical performance parameters were calculated and were found to conform to the USP standards.

Time-resolved fluorescence studies of the interaction of the Eu 3+ complexes of tetracycline analogues with DNA

The interaction of the Eu 3+ complexes of tetracycline analogues with DNA has been examined by using UV-visible absorption and fluorescence spectra. Among the tetracycline series, the europium fluorescence sensitized by tetracycline (TC) and oxytetracycline (OTC) were enhanced by DNA more than those of other antibiotics in the series. Therefore, Eu 3+-TC-DNA and Eu 3+-OTC-DNA systems were investigated by time-resolved fluorescence. The Eu 3+-OTC complex is a more sensitive fluorescence probe for selective determination of DNA than the Eu 3+-TC complex. Detection limits (signal/ noise = 2) for DNA are 2.4 and 5.0 ng ml −1 for the OTC and TC systems, respectively.

Study of the Eu(III)—tetracycline—thenoyltrifluoroacetone system by using the stopped-flow mixing technique: Determination of tetracycline in serum

The enhancing effect of thenoyltrifluoroacetone on the fluorescence intensity of the Eu(III)—tetracycline system in the presence of Triton X-100 was studied by using equilibrium and kinetic measurements. This ligand significantly improves the sensitivity of equilibrium methods for the tetracycline determination based on energy-transfer processes. Kinetic methodology implemented by means of the stopped-flow mixing technique allows analytical data to be acquired within 5 s after the reactants are mixed, thereby minimizing manipulation and enabling ready application of the proposed method to routine analyses for tetracycline in serum samples. The calibration graph was linear over the range 20–1000 ng ml −1, but can be expanded up to 10 000 ng ml −1 by increasing the reagent concentrations. The within- and between-assay relative standard deviations were close to 1%. The mean recovery obtained in the analysis of serum samples was 98.8%.

Fluorimetric determination of tetracycline and anhydrotetracycline

A rapid fluorimetric method employing the complexes of Al3+ with tetracycline (TC) and anhydrotetracycline (ATC) has been used for the measurement of the concentrations of TC and ATC in about 10−7–10−6 mol/l. The assay offers simplicity and rapidly compared with other methods. The recoveries in the determination of synthetic samples are in the range of 95–103% for TC and 101–120% for ATC. Several determinations of TC and ATC in serum and urine have been carried out with satisfactory results.

Equine monocytic ehrlichiosis (Potomac horse fever): a review

In the late 1970s, a new infectious disease in horses, involving acute enteritis, was recognised in the Potomac River area of Maryland, U.S.A. The causative agent was identified subsequently as a new species of rickettsial organism, later named Ehrlichia risticii. Since then, the disease has been reported in many other states, and in enzootic areas vaccination is common. Signs associated with the clinical disease included depression, fever, anorexia, decreased or absent intestinal sounds, profuse watery diarrhoea and laminitis. However, considerable variation in clinical manifestations has been reported in both the natural and experimental disease. Accurate diagnosis depends on serological testing; currently, the immunofluorescent antibody test (IFA) is used widely, although an enzyme-linked immunosorbent assay (ELISA) has been developed recently. Mortality in untreated cases is 15 to 35 per cent. Antibiotics of the tetracycline series have shown activity against the organism in vitro, in an in vivo murine model and appear to be useful in clinical cases.