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

Mammary glands taken at slaughter from healthy lactating cows were perfused in vitro with warmed and gassed Tyrode solution. Cefquinome (88.8mg cefquinome sulphate per 8mL) was administered by the intramammary route to all quarters and/or "systemically" via the perfusion fluid at concentrations similar to those measured in plasma following intramuscular administration of 1mg cefquinome per kg body weight. Samples of the perfusate were taken over a 6-h period and from the regional lymph nodes after 6h. Using a scalpel, sections of glandular tissue - at different distances from and vertical to the teat right up to the udder base - were gathered from four quarters each per route of administration at 2, 4 and 6h. The cefquinome content of the tissue samples was analysed by high performance liquid chromatography with diode array detection and of the perfusate samples by bioassay. After intramammary administration, the concentration of cefquinome in the glandular tissue decreased exponentially with increasing distance from the teat. The addition of cefquinome to the perfusion fluid produced a mean concentration of 0.2-0.5microg/g at all glandular tissue sites. Combined intramammary and systemic treatment ensured that concentrations exceeded the MIC(90) values of the most common mastitis pathogens in all areas of the udder by 2h post-administration. There was considerable variability in the tissue concentrations of cefquinome, particularly after intramammary administration. These results suggest that for the treatment of acute mastitis a combination of both intramammary and systemic administration is likely to be advantageous in order to rapidly produce maximum cefquinome concentrations in all regions of the udder.     

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.     

Tissue distribution of oxacillin and ampicillin in the isolated perfused bovine udder

In vivo, tissue distribution of intra-mammarily administered antibiotics is mostly only assessed by sampling milk and blood. Therefore, the described study analysed whether measurement of tissue concentrations makes sense in vitro instead. Isolated bovine udders were perfused with gassed and warmed Tyrode solution. To four front and rear quarters each, 1000 mg oxacillin in 7.5 ml vehicle was administered intracisternally, completely formulated as sodium monohydrate in two lactation ointments (with or without sodium dodecylsulphate) or 80% as benzathine salt in a dry-off ointment. Over 3 h, perfusate and glandular tissue from different locations were sampled and analysed by high pressure liquid chromatography. With increasing vertical distance to the teat base, the tissue concentration of antibiotics decreased. With the lactation ointment containing sodium dodecylsulphate, lower oxacillin concentrations were reached in glandular tissue and lymph nodes compared to those without. The ointments led to a higher recovery of oxacillin in glandular tissue than in perfusate. Aluminium monostearate in the dry-off ointment caused an even poorer absorption of oxacillin into perfusate. The isolated perfused bovine udder is suitable to study the tissue distribution of antibiotics, since the results were mainly comparable with the few existing in vivo studies and show the influence of different formulations.     

The tissue distribution of antibiotics in the udder--comparison of the situation in vivo with the isolated perfused bovine udder.]

Especially for animal protection reasons, tissue concentrations of intracisternally administered antibiotics in the mammary gland hardly can be determined in the live cow. Therefore, this paper assessed the use of the isolated perfused bovine udder to study the distribution of penicillins in glandular tissue. With this intention, the in vitro results acquired with this model were compared to tissue concentrations as well as absorption data from the few in vivo studies in the literature and differences were interpreted. This approach must consider inevitable deviations of experimental materials and methods. Furthermore, in vivo the udder is included in a closed circulatory system with other metabolism and excretion feasibilities than the isolated model. Moreover, the lower flow rate in the vessels in vitro has to be taken into account with respect to absorption capacities. Nevertheless, the tissue concentrations and the distribution equilibrium across the blood-udder-barrier in both experimental concepts corresponded with each other, if the deviating conditions are considered by calculating correction factors. Advantages and disadvantages of the isolated udder are discussed critically. In conclusion, this method is a useful completion of pharmacokinetic in vivo studies that are supposed to compare intracisternally administered formulations.     

Interdependence and distribution of subclinical mastitis and intramammary infection among udder quarters in dairy cattle

The objective of the present study was to determine the distribution of subclincial mastitis and intramammary infection (IMI) across udder quarters and to quantify, if any, the level of interdependence between quarters. Subclinical mastitis was defined as an udder quarter somatic cell count of > or =250,000. Intramammary infection was defined as the presence of pathogens in an udder quarter. The data used in the analyses consisted 6577 test-day records from 2034 lactations with observations on subclinical mastitis and 8428 test-day records from 2575 lactations with observations on IMI; each test-day record consisted data on all four udder quarters. Records were from animals on three research herds in southern Ireland. Observed distributions of IMI were compared to expected distributions, estimated using a binomial probability distribution, assuming independence among quarters. Generally, the observed frequencies deviated significantly from the expected frequencies, indicating some level of interdependence between quarters. Intraclass correlations were estimated from a mixed model including cow and test-day record nested within cow as random effects; fixed effects in the model included herd, year of calving, month of calving, parity, days in milk at sampling and interactions. Intraclass correlations within test-day record ranged from 0.14 to 0.50 for subclinical mastitis and from 0.02 to 0.40 for IMI. Thus, substantial interdependence between quarters exists which should be accounted for when analysing data from experiments across udder quarters. Failure to do so may result in incorrect inferences from statistical tests.     

Antimicrobial susceptibility of Prototheca zopfii isolated from bovine intramammary infections

In vitro antimicrobial susceptibility tests were carried out on 48 strains of Prototheca zopfii, an achlorophyllous algae causing refractory mastitis in dairy cows; 27 antimicrobials were evaluated. All strains were susceptible to both myxin and nystatin. In addition, 22 strains were susceptible to amphotericin B, 21 to polymyxin B, and 18 to gentamicin. Only 1 strain was susceptible to kanamycin. All strains were resistant to ampicillin, bacitracin, carbenicillin, cephalothin, chloramphenicol, clotrimazole, cloxacillin, erythromycin, flucytosine, ketoconazole, lincomycin, miconazole, neomycin, nitrofurazone, novobiocin, oleandomycin, penicillin, rifampin, streptomycin, tetracycline, and vancomycin.     

Disposition kinetics of lactoferrin in milk after intramammary administration

Disposition kinetics of lactoferrin (Lf) purified from cheese whey was studied in the milk of Finnish Ayrshire cows after intramammary administration of 1 g of Lf into one udder quarter. Intramammary administration of 1 g of Lf increased Lf concentration in milk for several hours. Mean elimination half-life of Lf was 2.2 h and a mean maximum concentration of 6.3 g/L was reached between 1 and 4 h. After 8 h of administration, Lf concentrations in milk decreased to almost the same level as before the infusion. Forty-eight hours postinfusion, the mean Lf concentration was again higher than in the milk samples taken before the infusion of Lf, being on average 1.5 g/L. Lactoferrin caused some local tissue irritation in the udder quarter. Severity of the irritation reactions varied between cows. The udder quarters of primiparous cows reacted faster than those of multiparous cows, but irritation reactions decreased more rapidly in the older cows than in primiparous cows. The cows had no general signs such as fever or anorexia. The somatic cell count returned to baseline level 4 days after the administration.     

Elimination of erythromycin in milk after intramammary administration in cows with specific mastitis: relation to dose,milking frequency and udder health

Elimination of erythromycin in milk following intramammary therapy of specific mastitis in cows was studied. Five cows received therapy in one quarter (G1), and eight in two quarters with five milked twice (G2) and three thrice a day (G3). Dose infused was 300 mg/quarter 12 h × 5 times. The drug concentrations in milk were determined using microbial assay technique with Micrococcus luteus as the test organism. Considerable variations occurred in the excretion of drug; levels for treated quarters being 8.25 to 37.61 μg/ml at first milking that declined rapidly at 24 h and no drug activity was observed beyond 36 h post treatment. In total, about 6–25% of the last infused dose appeared in the milk. Drug crossed to 1/15 quarter (G1), 6/10 quarters (G2) and all the six untreated quarters (G3). Crossover levels were significantly higher in mastitic quarters and for G3 cows, but duration of excretion remained same in all cases. It seems that crossover of erythromycin to untreated quarters is related to the udder health and dose infused.     

Plasminogen activation in the bovine udder

Plasmin is a serin protease with a broad substrate specificity which might cause disintegration of basal membranes, epithelium and surrounding matrix. Plasmin might also elicit degradation of tissue (Mullins & Rohrlich 1983).     

Determination of cloxacillin residues in dairy cows after intramammary administration

The aim of this study was to perform a comparative analysis of the characteristics of cloxacillin (CLO) (MRL of withdrawal in bovine milk is 30 ng/g) after a single intramammary (IMM) dose in the dry period (DP) and lactation (LP), and to establish a high‐performance liquid chromatography (HPLC) analytical method for CLO detection in milk. The research was conducted on a group of 10 cows in DP and 10 in LP. A single dose of 600 mg of CLO was administrated by the IMM route for a single quarter in DP and 500 mg for a single quarter in LP. CLO concentration was analyzed by HPLC. CLO was monitored at a wavelength of 206 nm. Pharmacokinetic calculations were performed using Phoenix^® WinNonlin^® 6.4 software. The calibration curve was linear over the range of 13.03–28 019.00 ng/g with the coefficient of determination R² > 0.999. CLO withdrawal in both the LP and DP group had a biphasic nature. The total CLO elimination in the DP and LP group was reached after 36 and 6.5 days, respectively. A quantitative and confirmatory method for the determination of CLO in fresh milk has been established. We have confirmed that the withdrawal of CLO in the DP group is not a linear process and has a stepwise character.     

奶牛乳房内灌注头孢噻呋钠的消除动力学研究

在奶牛乳房内灌注头孢噻呋钠后,采用超高效液相色谱一串联质谱法测定牛乳中头孢噻呋的浓度,对其消除动力学进行了研究。3头实验奶牛按每个乳房0．3g头孢噻呋灌注,牛乳中药物达到的最高浓度Cmax=107．89μg／mL,达峰时间Tmax=8h,药物半衰期T1/2=13．97h。在乳房内用药后的最初56h内,头孢噻呋浓度快速下降;最后一次给药88h后,所有乳腺中头孢噻呋的浓度都低于允许限量（0．1μg／mL）。故建议头孢噻呋在牛奶中的休药期为4d。     

Determination of the intramammary dose of benzylpenicillin required to maintain an adequate concentration in the milk to inhibit Gram‐positive bacteria in the clinically normal udder for 24 hr

The aim of this study was to determine the intramammary dose of benzylpenicillin required to maintain a concentration in the milk above the MIC for the Gram‐positive bacteria that cause mastitis. The product used in this study was a commercially available procaine benzylpenicillin in an oily suspension with micronized particles. Three dose levels were used: 200,000, 300,000, and 600,000 IU. Concentrations of benzylpenicillin in cow milk and plasma were determined after a single intramammary dose was administered into one quarter of each of the five cows in each treatment group. Samples were analyzed using an HPLC‐MS/MS method, which was validated during the study. Concentrations in the milk were well above the MIC for the target pathogens for all doses tested. There was a linear dose‐dependent increase in the mean AUCs of benzylpenicillin concentrations in plasma and milk. At the first milking, 12 hr after dosing, there was a significant difference between the mean milk benzylpenicillin concentrations in cows treated with a dose of 600,000 IU, and those treated with 200,000 or 300,000 IU. Although this study shows a linear relationship between the dose of procaine benzylpenicillin administered and the concentration in the milk in the healthy udder, it would be useful to conduct studies on cows with mastitis to define the optimum dose and duration of intramammary treatment with benzylpenicillin.     

Depletion of florfenicol in lactating dairy cows after intramammary and subcutaneous administration

Eighteen Holstein dairy cows ranging in body weight from 500–700 kg and with an average milk yield of 37 ± 6 kg/day were used to investigate the depletion of florfenicol (FFL) in milk and plasma of dairy cows. Three groups of six were administered FFL: Group A, intramammary (IMM) infusion of ~2.5 mg FFL/kg BW at three consecutive milking intervals (total amount of ~7.5 mg/kg BW); Group B, one IMM infusion (20 mg/kg BW) into one quarter and Group C, one subcutaneous (SC) treatment (40 mg/kg BW). IMM infusions were into the right front quarter. Cows were milked daily at 06:00 and 18:00 h. The highest concentrations (C_max) and time to C_max (T_max) were: 1.6 ± 2.2 μg·FFL/mL milk at 22 h (Group A), 5.5 ± 3.6 μg·FFL/mL milk at 12 h (Group B), and 1.7 ± 0.4 μg·FFL/mL milk at 12 h (Group C). The half‐lives (t_1/2) were ~19, 5.5, and 60 h, for Groups A, B, and C, respectively. FFL was below the limit of detection (LOD) by 60 h in three Group B cows, but above the LOD at 72, 84, and 120 h in three cows. FFL was above the LOD in milk from Group C's cows for 432–588 h. Plasma values followed the same trends as milk. The results demonstrate that IMM‐infused FFL is bioavailable and below the LOD within 72–120 h. The concentration of FFL was detectable in both plasma and milk over the course of 2–3 weeks after SC administration. The absence of residue depletion data presents problems in determining safe levels of FFL residues in milk and edible tissues. The data presented here must not be construed as approval for extra‐label use in food animals.     

Elimination kinetics of ceftiofur hydrochloride after intramammary administration in lactating dairy cows

OBJECTIVE: To determine the elimination kinetics of ceftiofur hydrochloride in milk after intramammary administration in lactating dairy cows. DESIGN: Prospective study. ANIMALS: 5 lactating dairy cows. PROCEDURE: After collection of baseline milk samples, 300 mg (6 mL) of ceftiofur was infused into the left front and right rear mammary gland quarters of each cow. Approximately 12 hours later, an additional 300 mg of ceftiofur was administered into the same mammary gland quarters after milking. Milk samples were collected from each mammary gland quarter every 12 hours for 10 days. Concentrations of ceftiofur and its metabolites in each milk sample were determined to assess the rate of ceftiofur elimination. RESULTS: Although there were considerable variations among mammary gland quarters and individual cows, ceftiofur concentrations in milk from all treated mammary gland quarters were less than the tolerance (0.1 microg/mL) set by the FDA by 168 hours (7 days) after the last intramammary administration of ceftiofur. No drug concentrations were detected in milk samples beyond this period. Ceftiofur was not detected in any milk samples from nontreated mammary gland quarters throughout the study. CONCLUSIONS AND CLINICAL RELEVANCE: Ceftiofur administered by the intramammary route as an extra-label treatment for mastitis in dairy cows reaches concentrations in milk greater than the tolerance set by the FDA. Results indicated that milk from treated mammary gland quarters should be discarded for a minimum of 7 days after intramammary administration of ceftiofur. Elimination of ceftiofur may be correlated with milk production, and cows producing smaller volumes of milk may have prolonged withdrawal times.