Tissue distribution of cefquinome after intramammary and “systemic” administration in the isolated perfused bovine udder

Pharmacokinetics and relative bioavailability study of two cefquinome sulfate intramammary infusions in cow milk

In this study, two intramammary infusions of cefquinome sulfate were investigated for pharmacokinetics and bioavailability. Twelve lactating cows for each group were administered an effective dose of 75 mg/gland for cefquinome, with milk samples collected at various time intervals. The concentrations of cefquinome in milk at different times were determined by the UPLC-MS/MS method. Analyses of noncompartmental pharmacokinetics were conducted on the concentration of cefquinome in milk. Mean pharmacokinetic parameters of group A and group B following intramammary administration were as follows: AUClast 300558.57 ± 25052.78 ng/mL and 266551.3 ± 50654.85 ng/mL, Cmax 51786.35 ± 11948.4 ng/mL and 59763.7 ± 8403.2 ng/mL, T1/2 5.69 ± 0.62 h and 5.25 ± 1.62 h, MRT 7.43 ± 0.79 h and 4.8 ± 0.78 h, respectively. Pharmacokinetic experiments showed that the relative bioavailability of group B was 88.69% that of group A. From our findings, group B (3 g: 75 mg) shows a quicker drug elimination process than group A (8 g: 75 mg), which suggests that the withdrawal period for the new formulation may be shorter.

Invited review: Selective treatment of clinical mastitis in dairy cattle

Treatment of clinical mastitis (CM) and use of antimicrobials for dry cow therapy are responsible for the majority of animal-defined daily doses of antimicrobial use (AMU) on dairy farms. However, advancements made in the last decade have enabled excluding nonsevere CM cases from antimicrobial treatment that have a high probability of cure without antimicrobials (no bacterial causes or gram-negative, excluding Klebsiella spp.) and cases with a low bacteriological cure rate (chronic cases). These advancements include availability of rapid diagnostic tests and improved udder health management practices, which reduced the incidence and infection pressure of contagious CM pathogens. This review informed an evidence-based protocol for selective CM treatment decisions based on a combination of rapid diagnostic test results, review of somatic cell count and CM records, and elucidated consequences in terms of udder health, AMU, and farm economics. Relatively fast identification of the causative agent is the most important factor in selective CM treatment protocols. Many reported studies did not indicate detrimental udder health consequences (e.g., reduced clinical or bacteriological cures, increased somatic cell count, increased culling rate, or increased recurrence of CM later in lactation) after initiating selective CM treatment protocols using on-farm testing. The magnitude of AMU reduction following a selective CM treatment protocol implementation depended on the causal pathogen distribution and protocol characteristics. Uptake of selective treatment of nonsevere CM cases differs across regions and is dependent on management systems and adoption of udder health programs. No economic losses or animal welfare issues are expected when adopting a selective versus blanket CM treatment protocol. Therefore, selective CM treatment of nonsevere cases can be a practical tool to aid AMU reduction on dairy farms.

Elimination of Cefquinome Sulfate Residue in Cow’s Milk after Intrauterine Infusion

As set in the maximum residue limit regulations of the European Commission, this study aimed to obtain the residual parameters in milk with optimized UPLC-MS/MS conditions and to determine the conclusive drug withdrawal period to ensure food safety. In this research, an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed to study cefquinome sulfate’s residue elimination in milk and to calculate cefquinome’s withdrawal period. Twelve healthy cows free of endometritis were selected for the experiment. Before using the drug, the vaginal orifice and perineum of each cow was disinfected. One dose of intrauterine perfusion was used for each cow, followed by an additional dose after 72 h. Before administration and 12 h, 18 h, 24 h, 36 h, 42 h, 48 h, 60 h, 66 h, 72 h, 84 h, 90 h, and 96 h after the last dose, milk (10 mL) was gathered from each cow’s teat and pooled. For the measurement of cefquinome concentrations in milk, UPLC-MS/MS was performed. A calibration curve was generated using linear regression as follows: Y = 250.86X − 102.29, with a correlation coefficient of 0.9996; the limits of detection and the limits of quantitation were 0.1 μg·kg−1 and 0.2 μg·kg−1, respectively. The average recovery of cefquinome was 88.60 ± 16.33% at 0.2 μg·kg−1, 100.95 ± 2.54% at 10 μg·kg−1, and 97.29 ± 1.77% at 50 μg·kg−1. For 5 consecutive days at the three spiking levels, the intra and inter-day relative standard deviations (RSD) were 1.28%–13.73% and 1.81%–18.44%, respectively; the residual amount of cefquinome was less than the maximum residue limit of 20 μg·kg−1, 36 h after administration; and the residual amount was less than the limit of detection (0.1 μg·kg−1) 48 h after administration. The withdrawal time of cefquinome in cow’s milk was 39.8 h, as calculated using WTM1.4 software. In terms of clinical practical use, the withdrawal period of milk was temporarily set at 48 h after the administration of the cefquinome sulfate uterus injection to cows, in accordance with the recommended dose and course.

Ex Vivo Pharmacokinetics and Pharmacodynamics Modeling and Optimal Regimens Evaluation of Cefquinome Against Bovine Mastitis Caused by Staphylococcus aureus

Cefquinome, the fourth-generation cephalosporin applied solely for veterinary medicine, is commonly used for bovine mastitis caused by Staphylococcus aureus. The present study aims to establish an optimal dose and provide a PK/PD Cutoff value (COPD) for cefquinome against S. aureus based on ex vivo pharmacokinetics and pharmacodynamics (PK/PD) integration. This study investigated the pharmacokinetics (PK) of cefquinome when administered as three consecutive intramammary (IMM) doses of cefquinome in three healthy dairy cows at 75 mg/gland. Drug concentration was determined by HPLC-MS/MS assay. The ex vivo pharmacodynamics (PD) of cefquinome were evaluated by using a milk sample from a PK experiment. The relationship between the AUC/ MIC of cefquinome and bacterial loading reduction was simulated using a Sigmoid Emax model. The cefquinome concentration in milk attained a maximum level of 1.55 ± 0.21 mg/mL at 1.8 h after the third administration. The mean value of the area under the concentration-time curve (AUC0−24) was 26.12 ± 2.42 mg·h/mL after the third administration. The elimination half-life was 10.6 h. For PD profile, the MICs of cefquinome in milk were 2–4 times higher than those in the broth. In vitro time-killing curve shows that initial bacterial concentration has a huge impact on antibacterial effect on three strains. The antibacterial effect was weakened with the initial bacterial concentration increasing from 106 to 108 CFU/mL. The AUC0−24h/MIC index correlated well with ex vivo efficacy both for the initial inoculum of 106 CFU/mL and 108 CFU/mL (R2 > 0.84). According to the inhibitory sigmoid Emax model analysis, the PK/PD surrogate (AUC0−24/MIC) values were 8,638, 1,397, and 3,851 for bactericidal effect (E = −3) with an initial inoculum of 106 CFU/mL, while the corresponding values were 12,266, 2,295, and 5,337, respectively, with the initial inoculum of 108 CFU/mL. The ex vivo PK/PD based population dose prediction indicated a target attainment rate (TAR) of 90% of 55 mg/gland/12 h. The COPD for cefquinome against S. aureus was 2 μg/mL under the recommended dose of 55 mg/gland/12 h. However, it should be validated in clinical practice in future investigations. These results contribute to the rational use of cefquinome for mastitis treatment in clinical veterinary medicine.

Pharmacokinetic evaluation of cefquinome in febrile goats following intravenous administration

Pharmacokinetics of cefquinome was studied in febrile female goats following its intravenous (IV) administration at the dose rate of 2 mg/kg body weight. The fever was induced by administration of Escherichia coli lipopolysaccharide (lμg/kg body weight). Cefquinome concentration in plasma of goats was estimated using HPLC. The drug was detected upto 24 h in febrile goats. The disposition kinetics of the drug was described by twocompartment open model. PK-PD indices; AUC24h/MIC, Cmax/MIC, T>MIC were calculated by integrating in-vivo PK data with earlier generated MIC data against Pasteurella (P.) multocida. A favourable PK and PK-PD indices suggested that the dose of 2 mg/kg/24 h of cefquinome would be effective clinically to treat goats affected with P. multocida infections.

A pilot study on the pharmacokinetics of a single intramuscular injection of cefquinome in Arabian camel calves

This study was conducted to evaluate the pharmacokinetics of cefquinome in camel calves after a single intramuscular injection in a dose of 2 mg/kg body weight (kg b. w.). Cefquinome concentrations were measured by ultra-high performance liquid chromatography-mass spectrometry (UPLC-MS/MS). A non-compartmental pharmacokinetic model was used to fit the time-concentration curve and estimate the pharmacokinetic parameters. The peak serum concentration (Cmax) was 28.4 μg/mL at the time of maximum concentration (Tmax) of 25 min. The elimination half-life (t1/2) was 17.4 h. The area under the concentration-time curve (AUC0-∞) was 103.7 μg/ml-1h and the mean residence time (MRT0-∞) was 21.3 h. In comparison with other animal species, the pharmacokinetics of cefquinome in Arabian camel calves showed faster absorption from the site of injection and slower elimination. Since cefquinome, as other beta-lactams, is a time-dependent antimicrobial agent, a single dose of 2 mg/kg b. w. might be sufficient against the most sensitive organisms in camel calves owing to its prolonged elimination phase. However, dose readjustment is required for cases needing concentrations above 2 µg/mL for 12 h or above 1 µg/mL for 24 h.

Efficacy of cefquinome and a combination of cloxacillin and ampicillin for treatment of dairy cows with Streptococcus agalactiae subclinical mastitis

A randomized clinical trial was conducted to assess efficacy of intramammary cloxacillin and ampicillin (CLOXIMM), intramammary cefquinome (CEFIMM), and intramuscular cefquinome (CEFIM) to treat Streptococcus agalactiae intramammary infections (Trial 1). Subsequently, two treatment groups were extended to assess whether CLOXIMM was not inferior to CEFIMM (Trial 2). Nine farms were included in the study. Milk samples were collected from all quarters of all lactating cows for microbiological identification of S. agalactiae. Positive cows were randomly allocated into four groups: CLOXIMM, CEFIMM, CEFIM, or negative control (CONTROL). Study outcomes were bacteriological cure at 14 (CURE14), 21 (CURE21), and 14 and 21 (CURE1421) days after treatment onset, and somatic cell count. Logistic regression was used to estimate the odds of cure between each treatment and CONTROL. Non-inferiority analysis was performed considering a one-sided 95% confidence interval (CI) and non-inferiority margins (Δ) of 0.10, 0.15, 0.20, and 0.25. Adjusted S. agalactiae bacteriological cure for CLOXIMM, CEFIMM, CEFIM, and CONTROL was 86, 98, 55, and 25% at day 14; 82, 93, 52, and 0% at day 21; and 82, 92, 40, and 0% at days 14 and 21, respectively. Treatment with CLOXIMM and CEFIMM resulted in greater bacteriological cure rates, as compared with CEFIM or CONTROL, which does not justify the use of CEFIM in S. agalactiae eradication programs. The CURE14 difference between CEFIMM and CLOXIMM was of 12.1 percentage points (95% CI: 0.056–0.184). CLOXIMM was considered not inferior to CEFIMM for Δ = 0.20 or 0.25 and inconclusive for Δ = 0.10 or 0.15. Thus, it should be pondered by veterinarians whether an expected 12.1 (5.6–18.4) percentage points increase in cure rate would justify the use of a fourth-generation cephalosporin, as opposed to a combination of traditional IMM drugs (cloxacillin and ampicillin) to treat S. agalactiae subclinical mastitis.

Selection of DNA aptamers and establishment of an effective aptasensor for highly sensitive detection of cefquinome residues in milk

Cefquinome (CFQ), which is a fourth-generation cephalosporin approved for veterinary use only, has been widely used for treating porcine or bovine respiratory infection, bovine mastitis and other diseases. However, the antibacterial effect of CFQ is based on the duration of drug concentration remaining in excess of the minimum inhibitory concentration in serum or tissues, thereby inevitably leading to CFQ residues with high levels in animal-sourced food. In this paper, four CFQ-specific ssDNA aptamers were selected via a magnetic bead-based systematic evolution of ligands by the exponential enrichment (SELEX) method. Aptamer W1 with the lowest dissociation constant (Kd) value of 40.13 ± 22.11 nM was chosen for establishing a fluorescence aptasensor based on magnetic separation and release of molecular beacons for detection of CFQ residues. This aptasensor exhibited a high sensitivity toward CFQ with a limit of detection (LOD) of 0.09 ng mL-1 (linear range from 0.5 to 150 ng mL-1). Moreover, the present aptasensor also showed high selectivity against ampicillin and CFQ's structural analogs (i.e., cefpirome sulfate and cefixime). Finally, this aptasensor was used to detect CFQ in real spiked milk. The recovery rate of CFQ from spiked milk samples ranged from 96.6% to 103.2%. These results indicated that the developed aptasensor is a promising, highly sensitive and specific method for CFQ residue detection in animal-sourced food.

Pharmacokinetics of cefquinome after single and repeated subcutaneous administrations in sheep

The purpose of this study was to determine the pharmacokinetics of cefquinome (CFQ) following single and repeated subcutaneous (SC) administrations in sheep. Six clinically healthy, 1.5 ± 0.2 years sheep were used for the study. In pharmacokinetic study, the crossover design in three periods was performed. The withdrawal interval between the study periods was 15 days. In first period, CFQ (Cobactan, 2.5%) was administered by an intravenous (IV) bolus (3 sheep) and SC (3 sheep) injections at 2.5 mg/kg dose. In second period, the treatment administration was repeated via the opposite administration route. In third period, CFQ was administrated subcutaneously to each sheep (n = 6) at a dose of 2.5 mg/kg q. 24 hr for 5 days. Plasma concentrations of CFQ were measured using the HPLC-UV method. Pharmacokinetic parameters were calculated using non-compartmental methods. The elimination half-life and mean residence time of CFQ after the single SC administration were longer than IV administration (p < 0.05). Bioavailability (F%) of CFQ following the single SC administration was 123.51 ± 11.54%. The area under the curve (AUC_0-∞ ) and peak concentration following repeated doses (last dose) were higher than those observed after the first dose (p < 0.05). CFQ accumulated after repeated SC doses. CFQ can be given via SC at a dose of 2.5 mg/kg every 24 hr for the treatment of infections caused by susceptible pathogens, which minimum inhibitory concentration is ≤1.0 μg/ml in sheep.

Residue concentration of cefquinome after intramammary dry cow therapy and short dry periods

Short dry periods and their effects on milk production, reproductive performance, as well as cow and udder health have been widely studied. A dearth of information is available about the consequences of short dry periods on the residue concentrations of dry cow antibiotics in milk after calving. The objective of our study was to determine the residue concentration of a dry cow antibiotic in milk after short dry periods during the colostrum period and early lactation. Quarters of 19 dry cows were treated with an intramammary (IMM) dry cow antibiotic containing 150 mg of cefquinome on d 21, 14, and 7 before calculated calving date. One quarter of each cow did not receive treatment and served as negative control. After calving, quarter foremilk samples were collected twice daily until 21 d and once daily until 36 d after IMM dry cow treatment (i.e., end of withdrawal period). A total of 588 foremilk samples from odd milking numbers were chosen for the determination of the residue concentration of cefquinome using HPLC-tandem mass spectrometry until the residue concentration fell below the limit of quantification (1 ng/g), which occurred at the latest in milking number 37. The dry period length of the treated quarters was categorized in 3 dry period groups ranging from 1 to 7 d (4.8 ± 2.4), 8 to 14 d (11.5 ± 2.3), and 15 to 26 d (19.5 ± 3.3; ±SEM), in dry period group 1, 2, and 3, respectively. In dry period group 1, the cefquinome concentration increased after calving until the third milking and decreased considerably until the fifth milking. In dry period group 2, the cefquinome concentration peaked at the second milking and decreased considerably until the fifth milking as well. There was no increase in cefquinome after calving in dry period group 3. Up to the 37th milking, the cefquinome concentration was higher in dry period group 1 than in dry period group 2 and 3. On average, 31.3 ± 1.2, 19.0 ± 1.1, and 6.7 ± 0.8 milkings and 19.4 ± 0.4, 20.6 ± 0.5, and 24.1 ± 0.7 d after treatment were necessary for the concentration of cefquinome to fall below the maximum residue limit (MRL) in dry period group 1, 2, and 3, respectively. These results indicate that shorter dry periods lead initially to higher cefquinome residues in milk. The residue concentration after experimental short dry periods still falls below the MRL within the recommended withdrawal period for milk of 36 d after IMM dry cow treatment. For the sake of food safety and economics, these short dry periods should not be used in the dry cow management, as they lead up to a maximum of 31.3 ± 1.2 milkings and 19.4 ± 0.4 d after treatment with cefquinome residues above the MRL. Therefore, a considerable number of milkings have to be discarded due to long withdrawal periods after calving.

Pharmacokinetics of a single intramuscular injection of cefquinome in buffalo calves

The objective of this study was to investigate the pharmacokinetics of cefquinome following single intramuscular (IM) administration in six healthy male buffalo calves. Cefquinome was administered intramuscularly (2 mg/kg bodyweight) and blood samples were collected prior to drug administration and up to 24 hr after injection. No adverse effects or changes were observed after the IM injection of cefquinome. Plasma concentrations of cefquinome were determined by high-performance liquid chromatography. The disposition of plasma cefquinome is characterized by a mono-compartmental open model. The pharmacokinetic parameters after IM administration (mean ± SE) were C_max 6.93 ± 0.58 μg/ml, T_max 0.5 hr, t_½kα 0.16 ± 0.05 hr, t_½β 3.73 ± 0.10 hr, and AUC 28.40 ± 1.30 μg hr/ml after IM administration. A dosage regimen of 2 mg/kg bodyweight at 24-hr interval following IM injection of cefquinome would maintain the plasma levels required to be effective against the bacterial pathogens with MIC values ≤0.39 μg/ml. The suggested dosage regimen of cefquinome has to be validated in the disease models before recommending for clinical use in buffalo calves.

In Vivo Pharmacokinetics/Pharmacodynamics of Cefquinome in an Experimental Mouse Model of Staphylococcus Aureus Mastitis following Intramammary Infusion

Staphylococcus aureus remains the major cause of morbidity of bovine mastitis worldwide leading to massive economic losses. Cefquinome is a fourth generation cephalosporin, which preserves susceptibility and antibacterial activity against S. aureus. This work aims to study the pharmacokinetic (PK) and pharmacodynamic (PD) modeling following intramammary administration of cefquinome against S. aureus mastitis. The mouse model of S. aureus mastitis was developed for the PK/PD experiments. The plasma PK characteristics after intramammary injection of cefquinome at various single doses of 25, 50, 100, 200, 400 μg per gland (both fourth pairs of glands: L4 and R4) were calculated using one-compartment and first-order absorption model. PD study was investigated based on twenty-one intermittent dosing regimens, of which total daily dose ranged from 25 to 4800 μg per mouse and dosage intervals included 8, 12 or 24 h. The sigmoid Emax model of inhibitory effect was employed for PK/PD modeling. The results of PK/PD integration of cefquinome against S. aureus suggested that the percentage of duration that drug concentration exceeded the minimal inhibitory concentration (%T>MIC) and the ratio of area under time-concentration curve over MIC (AUC/MIC) are important indexes to evaluate the antibacterial activity. The PK/PD parameters of %T>MIC and AUC0-24/MIC were 35.98% and 137.43 h to obtain a 1.8 logCFU/gland reduction of bacterial colony counts in vivo, against S. aureus strains with cefquinome MIC of 0.5μg/ml.

Integration of PK/PD for dose optimization of Cefquinome against Staphylococcus aureus causing septicemia in cattle

Cefquinome is a fourth generation cephalosporin with antimicrobial activity against gram negative and gram positive bacterial species, including Staphylococcus aureus. The aim of our study was to observe the ex-vivo activity of cefquinome against Staphylococcus aureus strains by using bovine serum from intravenously treated cattle. Cefquinome kinetics were measured by liquid chromatography and UV detection. In vitro post antibiotic effects (PAEs) and mutant prevention concentrations were determined with S. aureus strain ATCC 12598. Cefquinome exhibited time-dependent killing and produced in vitro PAEs increasing with concentration and time of exposure. A pharmacokinetic-pharmacodynamic model was established to simulate the efficacy of cefquinome for different dosage regimens. A dosage of 2 mg/kg every 12 h for 3 days was expected to reach a bactericidal activity against S. aureus in case of septicemia.

Systemic and mammary gland disposition of enrofloxacin in healthy sheep following intramammary administration

Background

Mastitis is one of the most important diseases affecting dairy sheep. Antimicrobial drugs are often administered directly through teat to treat or prevent this disease, but data on drug distribution within glandular tissue are scarce and it cannot be estimated from concentrations in milk. Thus, the aim of this study was to investigate systemic and mammary gland distribution of enrofloxacin after intramammary administration. The drug was administered to 6 healthy lactating Assaf sheep with an injector containing an enrofloxacin preparation (1 g drug/5 g ointment). Blood samples were collected at 0, 30, 60, 90, 120, 150 and 180 min. Animals were then sedated and sacrificed, and glandular tissue samples were obtained from treated udders at 2, 4, 6 and 8 cm height. Enrofloxacin concentrations were measured in plasma and tissue samples by UV high-performed liquid chromatography.

Results

Mean enrofloxacin plasma concentrations were below 0.5 μg/mL. Mean tissue concentrations decreased in mammary gland with vertical distance from the teat, ranging from 356.6 μg/g at 2 cm to 95.60 μg/g at the base of the udder. Glandular tissue concentrations best fitted to a decreasing monoexponential model, and showed a good correlation with an ex vivo model previously developed.

Conclusions

Enrofloxacin concentrations were effective in the entire glandular tissue against the main pathogens causing mastitis in sheep. These results suggest that this drug may be suitable to treat mastitis in sheep by intramammary administration.

Pharmacokinetic profile of cefquinome after oral subchronic flubendiamide exposure and in vitro plasma protein binding in buffalo calves

The disposition kinetics study of cefquinome was conducted following single intravenous (IV) administration of 2mg/kg bodyweight in buffalo calves after oral subchronic exposure to flubendiamide and to determine the in vitro plasma protein binding of cefquinome. Plasma concentrations of cefquinome were analyzed using reverse-phase high performance liquid chromatography (HPLC). The results were compared with our earlier study on the pharmacokinetics of cefquinome in untreated buffalo calves. Plasma concentration-time data for cefquinome following IV injection were best fit into a two-compartmental open model in flubendiamide-exposed buffalo calves. Following flubendiamide exposure, most of the pharmacokinetic parameters of cefquinome were significantly altered in buffalo calves. Cefquinome was bound to plasma proteins of buffalo calves to the extent of 11.4±0.66%. In flubendiamide-exposed animals an intravenous dose of 2mg/kg body weight would maintain the therapeutic plasma levels required to be effective against the bacterial pathogens with MIC values ≤0.39μg/mL for only 12h, whereas in untreated buffalo calves the same dose of 2mg/kg body weight would maintain the plasma levels up to 24h, The study revealed that subchronic flubendiamide exposure significantly alters the disposition of cefquinome in buffalo calves.

Pharmacokinetic/pharmacodynamic relationship of cefquinome against Pasteurella multocida in a tissue-cage model in yellow cattle

The cephalosporin antimicrobial drug cefquinome was administered to yellow cattle intravenously (i.v.) and intramuscularly (i.m.) at a dose of 1 mg/kg of body weight in a two-period crossover study. The pharmacokinetic (PK) properties of cefquinome in serum, inflamed tissue-cage fluid (exudate), and noninflamed tissue-cage fluid (transudate) were studied using a tissue-cage model. The in vitro and ex vivo activities of cefquinome in serum, exudate, and transudate against a pathogenic strain of Pasteurella multocida (P. multocida) were determined. A concentration-independent antimicrobial activity of cefquinome was confirmed for levels lower than 4 × MIC. Integration of in vivo pharmacokinetic data with the in vitro MIC provided mean values for the time that drug levels remain above the MIC (T > MIC) in serum was 14.10 h after intravenous and 14.46 h after intramuscular dosing, indicating a likely high level of effectiveness in clinical infections caused by P. multocida of MIC 0.04 μg/mL or less. These data may be used as a rational basis for setting dosing schedules, which optimize clinical efficacy and minimize the opportunities for emergence of resistant organisms.

Treatment for bovine Escherichia coli mastitis - an evidence-based approach

Bovine mastitis caused by Escherichia coli can range from being a subclinical infection of the mammary gland to a severe systemic disease. Cow-dependent factors such as lactation stage and age affect the severity of coliform mastitis. Evidence for the efficacy of antimicrobial treatment for E. coli mastitis is very limited. Antimicrobial resistance is generally not a limiting factor for treatment, but it should be monitored to detect changes in resistance profiles. The only antimicrobials for which there is some scientific evidence of beneficial effects in the treatment for E. coli mastitis are fluoroquinolones and cephalosporins. Both are critically important drugs, the use of which in animals destined for food should be limited to specific indications and should be based on bacteriological diagnosis. The suggested routine protocol in dairy herds could target the primary antimicrobial treatment for mastitis, specifically infections caused by gram-positive bacteria. In E. coli mastitis with mild to moderate clinical signs, a non-antimicrobial approach (anti-inflammatory treatment, frequent milking and fluid therapy) should be the first option. In cases of severe E. coli mastitis, parenteral administration of fluoroquinolones, or third- or fourth-generation cephalosporins, is recommended due to the risk of unlimited growth of bacteria in the mammary gland and ensuing bacteremia. Evidence for the efficacy of intramammary-administered antimicrobial treatment for E. coli mastitis is so limited that it cannot be recommended. Nonsteroidal anti-inflammatory drugs have documented the efficacy in the treatment for E. coli mastitis and are recommended for supportive treatment for clinical mastitis.

Pharmacokinetics following intravenous administration and pharmacodynamics of cefquinome in buffalo calves

Disposition following single intravenous injection (2 mg/kg) and pharmacodynamics of cefquinome were investigated in buffalo calves 6-8 months of age. Drug levels in plasma were estimated by high-performance liquid chromatography. The plasma concentration-time profile following intravenous administration was best described by a two-compartment open model. Rapid distribution of cefquinome was evident from the short distribution half-life (t ½ α = 0.36 ± 0.01 h), and small apparent volume of distribution (Vd area = 0.31 ± 0.008 L/kg) indicated limited drug distribution in buffalo calves. The values of area under plasma concentration-time curve, elimination half-life (t ½ β ), total body clearance (ClB), and mean residence time were 32.9 ± 0.56 μg · h/mL, 3.56 ± 0.05 h, 60.9 ± 1.09 mL/h/kg, and 4.24 ± 0.09 h, respectively. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration of cefquinome were 0.035-0.07 and 0.05-0.09 μg/mL, respectively. A single intravenous injection of 2 mg/kg may be effective to maintain the MIC up to 12 h in buffalo calves against the pathogens for which cefquinome is indicated.

Tissue distribution of enrofloxacin after intramammary or simulated systemic administration in isolated perfused sheep udders

OBJECTIVE

To determine the tissue distribution of enrofloxacin after intramammary or simulated systemic administration in isolated perfused sheep udders by measuring its concentration at various sample collection sites.

SAMPLE

26 udders (obtained following euthanasia) from 26 healthy lactating sheep.

PROCEDURES

For each isolated udder, 1 mammary gland was perfused with warmed, gassed Tyrode solution. Enrofloxacin (1 g of enrofloxacin/5 g of ointment) was administered into the perfused gland via the intramammary route or systemically via the perfusion fluid (equivalent to a dose of 5 mg/kg). Samples of the perfusate were obtained every 30 minutes for 180 minutes; glandular tissue samples were obtained at 2, 4, 6, and 8 cm from the teat base after 180 minutes. The enrofloxacin content of the perfusate and tissue samples was analyzed via high-performance liquid chromatography with UV detection.

RESULTS

After intramammary administration, maximun perfusate enrofloxacin concentration was detected at 180 minutes and, at this time, mean tissue enrofloxacin concentration was detected and mean tissue enrofloxacin concentration was 123.80, 54.48, 36.72, and 26.42 μg/g of tissue at 2, 4, 6, and 8 cm from the teat base, respectively. Following systemic administration, perfusate enrofloxacin concentration decreased with time and, at 180 minutes, tissue enrofloxacin concentrations ranged from 40.38 to 35.58 μg/g of tissue.

CONCLUSIONS AND CLINICAL RELEVANCE

By 180 minutes after administration via the intramammary or systemic route in isolated perfused sheep mammary glands, mean tissue concentration of enrofloxacin was greater than the minimum inhibitory concentration required to inhibit growth of 90% of many common mastitis pathogens in sheep. Use of either route of administration (or in combination) appears suitable for the treatment of acute mastitis in sheep.

Modelling the concentration-time relationship in milk from cattle administered an intramammary drug

Antimicrobial drugs are often infused directly through the streak canal into the bovine udder for the treatment or prevention of mastitis. These infusions have two major problems: drug residues in milk and variable antimicrobial efficacy. Both problems are influenced by the pharmacokinetics of intramammary delivery and elimination of drugs. This pharmacokinetics does not conform to the assumptions of traditional first-order mamillary pharmacokinetic models. To help understand drug delivery into and elimination from the udder, a new approach to pharmacokinetic modelling of the udder is proposed. This new model was used to predict the movement of drug within the udder and the concentrations of drug achieved within physiological compartments of the udder. These predictions were examined using computer modelling. The model was evaluated using data from in vivo intramammary infusion of cefuroxime. The model predicts that changes in milking efficiency (residual volume), milk productivity and milking frequency can impact both the drug residue persistence and the time that milk drug concentrations exceed the minimum inhibitory concentrations for pathogens. The model provides a new tool for future evaluation of intramammary dosing studies.

Development and validation of a high-performance liquid chromatography method for determination of cefquinome concentrations in sheep plasma and its application to pharmacokinetic studies

Cefquinome has a broad spectrum of antibacterial activity and was developed especially for use in animals. A simple and sensitive high-performance liquid chromatography (HPLC) method with UV-visible detection for quantification of cefquinome concentrations in sheep plasma was developed and validated. Separation of cefquinome from plasma components was achieved on a Phenomenex Gemini C(18) column (250 mm by 4.6 mm; internal diameter [i.d.], 5 μm). The mobile phase consisted of acetonitrile and 0.1% trifluoroacetic acid in water and was delivered at a rate of 0.9 ml/min. A simple and rapid sample preparation involved the addition of methanol to 200 μl of plasma to precipitate plasma proteins followed by direct injection of 50 μl of supernatant into the high-performance liquid chromatography system. The linearity range of the proposed method was 0.02 to 12 μg/ml. The intraday and interday coefficients of variation obtained from cefquinome were less than 5%, and biases ranged from -3.76% to 1.24%. Mean recovery based on low-, medium-, and high-quality control standards ranged between 92.0 and 93.9%. Plasma samples were found to be stable in various storage conditions (freeze-thaw, postpreparative, short-term, and long-term stability). The method described was found to be readily available, practicable, cheap, rapid, sensitive, precise, and accurate. It was successfully applied to the study of the pharmacokinetics of cefquinome in sheep. This method can be very useful and an alternate to performing pharmacokinetic studies in the determination of cefquinome for clinical use.

Tissue distribution of cloxacillin after intramammary administration in the isolated perfused bovine udder

Background

Various intramammary suspensions containing cloxacillin benzathine are registered for use in cattle as antibiotics for intramammary use at drying off. To ensure antibacterial efficacy, the glandular tissue concentration of an antimicrobial agent must be sufficient. Since the possibilities to measure concentrations in the different areas of the glandular tissue in vivo are very limited, it was the aim of the present study to examine the distribution of cloxacillin in vitro using the isolated perfused bovine udder.

Methods

Mammary glands taken at slaughter from healthy lactating cows were perfused in vitro with warmed and gassed Tyrode solution. 600 mg cloxacillin benzathine were administered as Orbenin Extra Dry Cow by the intramammary route to six front and rear quarters each. Samples of glandular tissue - at different distances from and vertical to the teat right up to the udder base - were gathered from the treated quarters after 6 h. Perfusate was also sampled before and hourly after treatment for 6 h. The cloxacillin content of the tissue samples and perfusate samples was analysed by high performance liquid chromatography.

Results

The concentration of cloxacillin in the glandular tissue of front quarters measured 6 h after administration tended to decrease with increasing vertical distance from the teat. The decrease pattern of the concentration was not quite clear in rear quarters. A considerable variation in the tissue concentrations of cloxacillin was obvious, which reflects in vivo conditions. The concentrations measured in the perfusate samples were below the limit of quantification at all time points, indicating limited absorption of the antibiotic from the glandular tissue.

Conclusion

After intramammary administration of the dry off product containing cloxacillin benzathine concentrations of more than 0.5 μg/g (MIC) were reached in all regions of the front and rear quarters.

Tissue distribution of marbofloxacin after ‘systemic’ administration into the isolated perfused bovine udder

Mammary glands taken at slaughter from healthy lactating cows were perfused in vitro with warmed and gassed Tyrode solution. Marbofloxacin was administered "systemically" via the perfusion fluid at concentrations similar to those measured in plasma following intravenous administration of 2mg/kg marbofloxacin. Samples from the perfusate were taken over a 24h period. Glandular tissue samples at different vertical distances from the teat up to the udder base were gathered from each of the four quarters after 3, 6, 12 and 24h. The marbofloxacin content of the tissue samples was analysed by high performance liquid chromatography with UV detection. The addition of marbofloxacin to the perfusion fluid produced median concentrations above the MIC90 (0.016microg/mL) against Escherichia coli at all glandular tissue sites measured after 3 and 6h with remarkable variations. Samples taken after 12 and 24h contained marbofloxacin in concentrations (median) of 0.22 (<0.05-0.32)microg/g and 0.13 (<0.05-0.16)microg/g. It is concluded that a systemic administration of marbofloxacin is well suited for the treatment of E. coli mastitis.

Residue depletion of cefquinome in swine tissues after intramuscular administration

A high-performance liquid chromatography (HPLC) method with ultraviolet (UV) detection was developed for the detection of cefquinome (CEQ) residues in swine tissues. The limit of detection (LOD) of the method was 5 ng g(-1) for muscle and 10 ng g(-1) for fat, liver, and kidney. Mean recoveries of CEQ in all fortified samples at a concentration range of 20-500 ng g(-1) were 80.5-86.0% with coefficient of variation (CV) below 10.3%. Residue depletion study of CEQ in swine was conducted after five intramuscular injections at a dose of 2 mg kg(-1) of body weight with 24 h intervals. CEQ residue concentrations were detected in muscle, fat, liver, and kidney using the HPLC-UV method at 265 nm. The highest CEQ concentration was measured in kidney tissue during the study period, indicating that kidney was the target tissue for CEQ. CEQ concentrations in all examined tissues were below the accepted maximum residue limit (MRL) recommended by the Committee for Veterinary Medical Products of European Medical Evaluation Agency (EMEA) at 3 days post-treatment.

Determination of cefquinome in pig plasma and bronchoalveolar lavage fluid by high-performance liquid chromatography combined with electrospray ionization mass spectrometry

The aim of this study was to develop a rapid and sensitive method for the quantification of cefquinome in animal plasma and bronchoalveolar lavage (BAL) fluid using high-performance liquid chromatography combined with electrospray tandem mass spectrometry (LC-ESI-MS/MS). Cefadroxil is used as internal standard. For plasma, the sample preparation includes a simple deproteinization step with a Microcon filter. This allows detecting the unbound cefquinome concentration, which is correlated with the concentration in other body fluids, such as BAL fluid. To be able to detect the total plasma concentration, deproteinization with acetonitrile, followed by a back-extraction of actonitrile with dichloromethane was performed. The BAL fluid is centrifuged to precipitate floating particles. Chromatographic separation is achieved on a PLRP-S column using 0.005% formic acid and methanol as mobile phase. For plasma, good linearity was observed in the range of 5-2500 ng ml(-1) for both the unbound and total concentration. The response in BAL fluid was linear in the range of 4-1000 ng ml(-1). The limit of quantification (LOQ) was set at 5.00 ng ml(-1) for plasma and at 4.00 ng ml(-1) for BAL fluid. The limit of detection (LOD) was 3.12 ng ml(-1) and 0.41 ng ml(-1) for the unbound and total concentration in plasma, respectively, and was 1.43 ng ml(-1) for BAL fluid. The method was shown to be of use in a pharmacokinetic study in pigs, where the correlation between cefquinome concentrations in plasma and BAL fluid of pigs was studied.