ceftiofur and Staphylococcal-Infections

A new, extended long-acting tilmicosin (TLAe) preparation was tested against intramammary ceftiofur (CEF) using a non-inferiority trial model during dry-cow therapy (DCT) in a farm with high bovine population density and deficient hygiene application.. To evaluate the possibility that TLAe administered parenterally can achieve non-inferiority status compared to CEF administered intramammary for DCT.. TLAe and CEF had overall cure rates of 57% and 53% (. This study is the first successful report of parenteral DCT showing comparable efficacy as CEF, the gold-standard. The extended long-term pharmacokinetic activity of TLAe explains these results.

Topics: Animals; Anti-Bacterial Agents; Cattle; Cattle Diseases; Cephalosporins; Delayed-Action Preparations; Escherichia coli; Escherichia coli Infections; Female; Injections, Subcutaneous; Mastitis, Bovine; Staphylococcal Infections; Staphylococcus aureus; Streptococcal Infections; Streptococcus; Tylosin

OBJECTIVE To determine the concentration of tilmicosin in mammary gland secretions of dairy cows following administration of an experimental preparation once or twice during the dry period (45-day period immediately prior to calving during which cows are not milked) and to evaluate its efficacy for the treatment of cows with intramammary infections (IMIs) caused by Staphylococcus aureus at dry off (cessation of milking; first day of dry period), compared with that of an intramammary infusion of ceftiofur. ANIMALS 172 cows. PROCEDURES Milk samples were collected for microbiological culture 5 days before dry off and at calving and 15 and 30 days after calving. Cows with Staphylococcus IMIs were randomly assigned to receive an experimental preparation of tilmicosin (20 mg/kg, SC) once at dry off (n = 58) or at dry off and again 20 days later (56) or receive a long-acting intramammary preparation of ceftiofur (500 mg/mammary gland; 56) at dry off. Mammary gland secretions were collected from 5 cows in the tilmicosin-treated groups every 5 days after dry off until calving for determination of tilmicosin concentration. RESULTS Mean maximum concentration of tilmicosin in mammary gland secretions ranged from 14.4 to 20.9 μg/mL after the first dose and was 17.1 μg/mL after the second dose. The bacteriologic cure rate was 100% for all 3 treatments. Tilmicosin was detectable for 0 and 18 days after calving in the milk of cows treated with 1 and 2 doses of tilmicosin, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Administration of an experimental preparation of tilmicosin (20 mg/kg, SC) once to dairy cows at dry off might be useful for the treatment of S aureus IMIs.

Topics: Animals; Cattle; Cephalosporins; Female; Humans; Lactation; Mammary Glands, Animal; Mastitis, Bovine; Milk; Staphylococcal Infections; Staphylococcus aureus; Tylosin

The study objective was to compare the efficacy of 3 commercial dry cow mastitis formulations regarding quarter-level prevalence of intramammary infections (IMI) postcalving, cure of preexisting infections over the dry period, prevention of new infections during the dry period, and risk for a clinical mastitis case between calving and 100d in milk (DIM). A total of 1,091 cows (4,364 quarters) from 6 commercial dairy herds in 4 different states (California, Iowa, Minnesota, and Wisconsin) were enrolled and randomized to 1 of the 3 treatments at dry-off: Quartermaster (QT; 1,000,000 IU of procaine penicillin G and 1 g of dihydrostreptomycin; Pfizer Animal Health, New York, NY), Spectramast DC (SP; 500 mg of ceftiofur hydrochloride; Pfizer Animal Health), or ToMorrow Dry Cow (TM; 300mg of cephapirin benzathine; Boehringer Ingelheim Vetmedica Inc., St. Joseph, MO). Quarter milk samples were collected for routine bacteriological culture before dry cow therapy treatment at dry-off, 0 to 6 DIM, and 7 to 13 DIM and an on-farm record-keeping system was used to retrieve data on clinical mastitis cases. Noninferiority analysis was used to evaluate the effect of treatment on the primary outcome, risk for a bacteriological cure during the dry period. Multivariable logistic regression techniques were used to describe the effect of treatment on risk for presence of IMI postcalving and risk of a new IMI during the dry period. Cox proportional hazards regression was used to describe the effect of treatment on the risk and time for quarters to experience an episode of clinical mastitis between calving and 100 DIM. The overall crude quarter-level prevalence of infection at dry-off was 19.2%. The most common pathogen isolated from milk samples at dry-off was coagulase-negative Staphylococcus, followed by Aerococcus spp. and other Streptococcus spp. Noninferiority analysis showed no effect of treatment on risk for a cure between dry-off and calving [least squares means (LSM): QT=93.3%, SP=92.6%, and TM=94.0%] and secondary analysis showed no effect of treatment on risk for presence of an IMI at 0 to 6 DIM (LSM: QT=16.5%, SP=14.1%, and TM=16.0%), risk for development of a new IMI between dry-off and 0 to 6 DIM (LSM: QT=14.8%, SP=12.3%, and TM=14.2%), or risk of experiencing a clinical mastitis event between calving and 100 DIM (LSM: QT=5.3%, SP=3.8%, and TM=4.1%). In conclusion, no difference was observed in efficacy among the 3 products evaluated when assessing the aforementi

Topics: Animals; Anti-Bacterial Agents; California; Cattle; Cephalosporins; Cephapirin; Dihydrostreptomycin Sulfate; Escherichia coli Infections; Female; Lactation; Mastitis, Bovine; Milk; Minnesota; New York; Penicillin G; Staphylococcal Infections; Streptococcal Infections; Wisconsin

Little research has focused on treatment of cows with subclinical mastitis during lactation. Ceftiofur is a new broad-spectrum, third-generation cephalosporin antibiotic for veterinary use that inhibits bacterial cell wall synthesis by interfering with enzymes essential for peptidoglycan synthesis. Ceftiofur should be effective against a wide range of contagious and environmental mastitis pathogens. Objectives of the present study were to evaluate the efficacy of ceftiofur for treatment of subclinical mastitis in lactating dairy cows, and to determine if extended therapy regimens enhanced efficacy of ceftiofur. Holstein and Jersey dairy cows (n = 88) from 3 dairy research herds were used. Cows were enrolled in the study based on milk somatic cell counts >400,000/mL and isolation of the same mastitis pathogen in 2 samples obtained 1 wk apart. Cows with one or more intramammary infections (IMI) were blocked by parity and DIM and allocated randomly to 1 of 3 different ceftiofur treatment regimens: 2-d (n = 49 IMI), 5-d (n = 41 IMI), and 8-d (n = 38 IMI) treatment regimens. For all groups, 125 mg of ceftiofur hydrochloride was administered via intramammary infusion. Eighteen cows with 38 IMI were included as an untreated negative control group. A bacteriological cure was defined as a treated infected mammary quarter that was bacteriologically negative for the presence of previously identified bacteria at 14 and 28 d after the last treatment. Efficacy of ceftiofur therapy against all subclinical IMI was 38.8, 53.7, and 65.8% for the 2-, 5-, and 8-d ceftiofur treatment regimens, respectively. Four of 38 (10.5%) IMI in control cows were cured spontaneously without treatment. All 3 ceftiofur treatment regimens were significantly better than the negative control, and the 8-d extended ceftiofur treatment regimen treatment group was significantly better than the standard 2-d treatment group. Pathogen groups had significantly different cure rates from one another. The cure rate for the 8-d extended ceftiofur treatment regimen was 70% for Corynebacterium bovis, 86% for coagulase-negative Staphylococcus species, 36% for Staph. aureus, 80% for Streptococcus dysgalactiae ssp. dysgalactiae, and 67% for Strep. uberis.

Topics: Animals; Anti-Bacterial Agents; Cattle; Cell Count; Cephalosporins; Corynebacterium Infections; Female; Lactation; Mammary Glands, Animal; Mastitis, Bovine; Milk; Staphylococcal Infections; Streptococcal Infections

Antimicrobial drug resistance is an important problem that challenges veterinary clinicians to provide effective treatments without further spreading resistance to other animals and people. The most commonly used pharmacodynamic parameter to define potency of antimicrobial drugs is minimum inhibitory concentration (MIC). The aim of this study was to evaluate the antibiotic susceptibility of thirty-six strains of Staphylococcus aureus isolated from dairy goats with mastitis and rabbits with chronic staphylococcosis. Four cephalosporins were tested: cephalexin, cephalotin, cefonicid and ceftiofur. MIC tests were performed according to the microdilution broth method. The calculated values of sensitivity in goats and rabbits were 66.67% and 72.22% for cephalexin, 72.22 % and 94.44% for cefonicid, 77.78% and 94.44% for cephalotin and 77.78% and 100% for ceftiofur, respectively. For all antibiotics, MIC90 of S. aureus from rabbits were lower than MIC90 from goats. These data suggest that more antibiotics are used in goat milk production than in rabbit farming. According to MIC values obtained in this study, ceftiofur and cephalotin may be the best option for treating S. aureus infections in lactating goats. For rabbits, ceftiofur showed lowest MIC values, therefore, it could be an alternative to treatment the infections caused by S. aureus in this species.

Topics: Animals; Anti-Bacterial Agents; Cefonicid; Cephalexin; Cephalosporins; Cephalothin; Farms; Female; Goat Diseases; Goats; Lactation; Monobactams; Rabbits; Spain; Staphylococcal Infections; Staphylococcus aureus

Mastitis is a major disease affecting dairy sheep. It is caused by microorganisms that generate inflammation of the mammary gland in response to tissue invasion. This syndrome affects the welfare of ewes, as well as the production and quality of the milk, thereby reducing its productive efficiency. Because mastitis causes inflammation process, it also increases the production of free radicals that cause lesions via lipoperoxidation, causing damage to proteins, cells and tissues. One way to minimize the impact of the disease is antimicrobial treatment. Nevertheless, the continuous use of antimicrobials contributes to microbial resistance, in addition to producing residues in the milk and derivatives if not given during the grace period. Therefore, the objective of this study was to evaluate the consequences of subclinical mastitis on ewe health, milk production, milk composition and quality. We also evaluated the susceptibility of the bacteria in vitro using disk diffusion antibiograms. Finally, we performed two-way testing of efficacy of treatment in Lacaune ewes using the same agents. In the first stage of the study, 30 lactating ewes (±90 days) were used, 10 of which were negative on the CMT (California Mastitis Test) used as control group (CG) and 20 sheep with subclinical mastitis diagnosed by CMT (MG). Samples were collected and several analyses were performed on the milk and blood. We found that ewes in the MG had higher lipid peroxidation in serum and milk, as well as lower production, with reduction of the total dry extract in milk. There were 15 isolates of Staphylococcus hyicus, four isolates of each S. epidermidis and S. intermedius, and two isolates of Corynebacterium spp. The primary hematological result was leukocytosis in ewes with mastitis. Based on the antibiogram, we chose ceftiofur for in vivo tests. In this stage, we divided the sheep with subclinical mastitis into two subgroups of 10 ewes each, to receive drug by two routes: intramuscular (IM) and intramammary (IMM). In the IMM group, of the 10 CMT-positive ewes at the beginning of the experiment, seven were already negative by the racket test 120 h after the last application (70% efficacy). In the IM group, of the 10 positive ewes, only four were negative after 120 h of the final application, a low efficacy treatment (40%). We evaluated antimicrobial residues in the milk of treated animals. We found this material within 5 days after treatment in the two forms used; despite the fact t

Topics: Animals; Anti-Bacterial Agents; Cephalosporins; Corynebacterium; Female; Food Quality; Mammary Glands, Animal; Mastitis; Microbial Sensitivity Tests; Milk; Oxidative Stress; Sheep; Sheep Diseases; Staphylococcal Infections; Staphylococcus epidermidis; Staphylococcus hyicus; Staphylococcus intermedius; Streptococcal Infections; Treatment Outcome

Staphylococcus aureus intramammary infections (IMIs) have low cure rates using standard antibiotic treatment and increasing the duration of treatment usually improves therapeutic success. Chronic IMIs are thought to be caused by bacteria presenting a specific virulence phenotype that includes the capacity to produce greater amounts of biofilm. In this study, antibiotic susceptibility and biofilm production by S. aureus isolates recovered from IMIs that were cured or not following an extended therapy with cephapirin, pirlimycin or ceftiofur for 5, 8 and 8 days, respectively, were compared. An isolate was confirmed as from a persistent case (not cured) if the same S. aureus strain was isolated before and after treatment as revealed by the same VNTR profile (variable number of tandem repeats detected by multiplex PCR). The antibiotic minimal inhibitory concentrations (MICs) were determined for these isolates as well as the capacity of the isolates to produce biofilm. Isolates from persistent cases after extended therapy with cephapirin or ceftiofur had higher MICs for these drugs compared to isolates from non-persistent cases (p < 0.05) even though the antibiotic susceptibility breakpoints were not exceeded. Isolates of the ceftiofur study significantly increased their biofilm production in presence of a sub-MIC of ceftiofur (p < 0.05), whereas isolates from the pirlimycin group produced significantly less biofilm in presence of a sub-MIC of pirlimycin (p < 0.001). Relative antibiotic susceptibility of the isolates as well as biofilm production may play a role in the failure of extended therapies. On the other hand, some antibiotics may counteract biofilm formation and improve cure rates.

Topics: Animals; Anti-Bacterial Agents; Biofilms; Breast Diseases; Cattle; Cattle Diseases; Cephalosporins; Cephapirin; Clindamycin; Drug Resistance, Bacterial; Female; Microbial Sensitivity Tests; Minisatellite Repeats; Staphylococcal Infections; Staphylococcus aureus

Ceftiofur hydrochloride (CEF) is occasionally used for the intramammary (IMM) treatment of mastitis. This extralabel manner could result in a drug-residue violation of the milk. The objective of this study was to determine the elimination kinetics of IMM CEF in lactating dairy cattle. The pharmacokinetic profile of CEF after repeated IMM administration in nine healthy cows and nine Staphylococcus aureus infected cows was investigated, alongside determining the MICs of Staph. aureus field strains. The MIC 90 value for CEF in Staph. aureus field strains (n = 31) was 0.25 μg/mL. The t >MIC CEF values for low- production quarters were longer than those for high- and mid- production quarters. The results showed that ceftiofur was detected in milk up to 108 h after the last infusion in both healthy and infected cows. Cows with low milk production eliminate IMM drugs more slowly than cows with higher production. Our findings suggest that this extralabel use is not encouraged and a prudent use is recommended for mastitis therapy. The use of CEF should be reserved for infections where susceptibility tests indicate its efficacy and when alternatives are not available.

Topics: Animals; Anti-Bacterial Agents; Area Under Curve; Cattle; Cephalosporins; Female; Mammary Glands, Animal; Mastitis, Bovine; Microbial Sensitivity Tests; Milk; Staphylococcal Infections; Staphylococcus aureus

Five dairy goats were used to determine the milk and serum concentrations along with elimination characteristics of ceftiofur following intramammary administration. One udder half of each goat was infused twice with 125 mg ceftiofur with a 24-h interval between infusions. Milk samples were collected at 1, 2, 8, and 12 h after the last infusion and then every 12 h for a total of 7 days. Blood was collected from each animal at 3, 8, 12, and 24 h after infusion and then every 24 h for 6 days. Following a washout period of 1 week, the experiment was repeated using the opposite udder half. The elimination half-life of ceftiofur from the mammary gland was 4.7 h. The concentration of ceftiofur was greater than published MIC90 values for Staphylococcus spp. bacteria for 24 h. Ceftiofur was absorbed into systemic circulation from the mammary gland. The maximum concentration was 552 ng/mL at 3 h after infusion, and the serum elimination half-life was 10 h. Intramammary infusion of 125 mg ceftiofur every 24 h can be expected to maintain drug concentration in milk above published MIC90 for Staphylococcus spp.

Topics: Animals; Anti-Bacterial Agents; Cephalosporins; Drug Administration Routes; Female; Goat Diseases; Goats; Mammary Glands, Animal; Mastitis; Microbial Sensitivity Tests; Milk; Staphylococcal Infections

Antimicrobials are often used for treatment of bovine mastitis and the possibility of selection for resistant bacteria must be considered. The objectives of this study were to determine the minimum inhibitory concentration of Staphylococcus aureus recovered from cases of clinical and subclinical bovine mastitis, and to determine the prevalence of multidrug resistance in this population. Milk samples were collected from cows on commercial dairy herds (n=13), including quarters (n=1,574) of cows with subclinical mastitis cases, and cows experiencing clinical mastitis cases (n=608). Selected Staph. aureus isolates, obtained from clinical (n=58) and subclinical (n=58) mastitis cases, were used to determine minimum inhibitory concentrations of 12 selected antimicrobials. Of Staph. aureus isolates tested, 87 (75%) did not exhibit resistance to any antimicrobial, 28 (24.1%) exhibited resistance to 1 (n=21) or 2 (n=7) classes of antimicrobials, and 1 (0.9%) exhibited multidrug resistance. All Staph. aureus (clinical and subclinical cases) were inhibited by the range of concentrations tested for ceftiofur and oxacillin. Moreover, no isolates obtained from clinical mastitis cases exhibited resistance to cephalothin, penicillin-novobiocin, or sulfadimethoxine. Of isolates, 3 exhibited resistance to enrofloxacin. Of isolates exhibiting resistance to more than 1 antimicrobial, independent of antimicrobial class, the combination of erythromycin and tetracycline, and ampicillin and penicillin accounted for the majority of resistance. Of isolates tested, 19% were resistant to tetracycline and 14% were resistant to penicillin. Survival curves of Staph. aureus relative to minimum inhibitory concentration demonstrated heterogeneity among case types for ceftiofur, cephalothin, and erythromycin. Multidrug resistance was identified in only 1 isolate obtained from a single farm.

Topics: Animals; Anti-Bacterial Agents; Cattle; Cephalosporins; Drug Resistance, Bacterial; Enrofloxacin; Female; Fluoroquinolones; Mastitis, Bovine; Microbial Sensitivity Tests; Milk; Oxacillin; Staphylococcal Infections; Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) have emerged in animals. Testing 98 mecA negative and 71 mecA positive S. aureus we compared the usefulness of ceftiofur and cefquinome to cefoxitin, for detection of MRSA and found that these cephalosporins are not as efficient as cefoxitin.

Topics: Animals; Anti-Bacterial Agents; Cephalosporins; Disk Diffusion Antimicrobial Tests; Humans; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Phenotype; Sensitivity and Specificity; Staphylococcal Infections; Swine; Swine Diseases

Ceftiofur concentrations in an infected and uninfected environment were compared and the efficacy of locally administered ceftiofur was evaluated in an experimental infection with Staphylococcus aureus in tissue cages. Eight ponies had tissue cages (TCs) implanted s.c. on each side of the neck. Into one of the cages 150 mg of ceftiofur was administered and fluid samples were taken to determine ceftiofur concentrations. After 1 week the other TC was infected with S. aureus and subsequently treated with 150 mg ceftiofur administered locally into the TC once daily for 21 days. Samples of fluid were taken to determine ceftiofur concentrations and for bacterial counts. Ceftiofur concentrations did not differ significantly in the infected and uninfected environments after single dose of 150 mg of ceftiofur. Concentrations were considerably in excess of the minimum inhibitory concentration (MIC) of the S. aureus strain used. A marked decrease of viable bacteria in tissue cage fluid (TCF) occurred. In five of seven ponies; however, the infection was not eliminated and abscess formation occurred. Therefore, local application of ceftiofur alone is not advisable for infections with S. aureus in secluded sites in horses, but should be used only with adjunctive therapy.

Topics: Animals; Cephalosporins; Horses; Male; Staphylococcal Infections; Staphylococcus aureus; Treatment Failure

Two antibiotic preparations, tilmicosin and ceftiofur, were tested intramammarily and parenterally against Staphylococcus aureus mastitis in lactating cows. Neither product was effective as a lactating cow treatment at the doses and durations of treatment tested. Injection or infusion of tilmicosin and infusion of ceftiofur resulted in reductions of bacteria present in milk; however, only one quarter treated with infusion of tilmicosin was cured, and no cures were observed for the other treatments. Somatic cell counts were transiently reduced by infusion of ceftiofur and by infusion and injection of tilmicosin; however, they returned to pretreatment values by 28 d posttreatment.

Topics: Animals; Anti-Bacterial Agents; Cattle; Cephalosporins; Female; Infusions, Intravenous; Injections, Subcutaneous; Lactation; Macrolides; Mammary Glands, Animal; Mastitis, Bovine; Milk; Staphylococcal Infections; Staphylococcus aureus; Treatment Outcome; Tylosin

The activity of selected antimicrobial agents was determined against strains of Staphylococcus aureus that were isolated from bovine intramammary infections and that were positive or negative for beta-lactamase. A total of 107 S. aureus strains (70 that were positive for beta-lactamase and 37 that were negative for beta-lactamase) were used in the study. Production of beta-lactamase was determined using a chromogenic cephalosporin disk method. Minimum inhibitory concentrations (MIC) for each test strain were determined using a commercially available microdilution panel. The following compounds were tested: penicillin, ampicillin, oxacillin, cephapirin, ceftiofur, penicillin plus novobiocin, erythromycin, and pirlimycin. Of the five beta-lactam compounds tested, penicillin and ampicillin were most affected by beta-lactamase activity, but oxacillin, cephapirin, and ceftiofur were not affected. Penicillin plus novobiocin also demonstrated excellent activity against strains of S. aureus that were both positive and negative for beta-lactamase. Erythromycin and pirlimycin demonstrated good activity against the S. aureus strains that were negative for beta-lactamase; 90% of the isolates had an MIC of < or = 0.5 microgram/ml (MIC90). The MIC90 for erythromycin and pirlimycin for strains that were positive for beta-lactamase was > 64.0 micrograms/ml. However, 8 strains, in addition to producing beta-lactamase, were also resistant to macrolides and lincosaminides. Recalculation of the MIC90 without these 8 strains yielded equivalent values for both erythromycin and pirlimycin with strains that were positive or negative for beta-lactamase (MIC90 < or = 0.5 microgram/ml).

Topics: Ampicillin; Animals; Anti-Bacterial Agents; beta-Lactamases; beta-Lactams; Cattle; Cephalosporins; Cephapirin; Dose-Response Relationship, Drug; Drug Resistance, Microbial; Erythromycin; Female; Mammary Glands, Animal; Mastitis, Bovine; Novobiocin; Oxacillin; Penicillins; Staphylococcal Infections; Staphylococcus aureus

Because somatic cell counts (SCC) of caprine milk are higher than SCC of bovine milk, the performance of antibiotic residue tests for screening bovine milk was investigated for caprine milk. Eighty-five does that were free of antibiotic usage for at least 30 d and that were free of clinical mastitis were sampled at three milkings during a 37-d period. At each sampling, foremilk was collected for bacteriological analysis, and composite bucket milk samples were collected for antibiotic testing and SCC. Day of lactation, parity, 305-d mature equivalent milk yield, and SCC averaged 221 d (57 to 577 d), 2.3 lactations (one to nine lactations), 1160 kg (623 to 1750 kg), and 2.2 x 10(6)/ml (0.3 to 30.7 x 10(6)/ml), respectively. The mean Dairy Herd Improvement Association test day milk yield for the month of sample collection was 3 kg (1.4 to 6.4 kg). Intramammary infections were present in 54% of the goats and in 36% of the udder halves. Assays included positive (5 and 10 ppb of penicillin-G and 50 ppb of ceftiofur) and negative controls that had been prepared in caprine milk and controls supplied by the manufacturers. One false-negative outcome and one false-positive outcome were recorded. For one sampling day, a positive linear relationship existed between SCC and the results of one test, and a quadratic relationship existed between SCC and the results of another test. The antibiotic residue screening tests for milk from individual goats adequately identified milk that was free of antibiotic. These tests are therefore recommended for use with caprine milk.

Topics: Animals; Anti-Bacterial Agents; Arthritis-Encephalitis Virus, Caprine; Cephalosporins; Drug Residues; False Negative Reactions; False Positive Reactions; Female; Goat Diseases; Goats; Lentivirus Infections; Mass Screening; Milk; Prevalence; Regression Analysis; Sensitivity and Specificity; Staphylococcal Infections; Time Factors; United States; United States Department of Agriculture; United States Food and Drug Administration

Twenty-five Staphylococcus aureus strains isolated from bovine mastitis were tested for their susceptibility to ceftiofur. Zone diameter for 30 micrograms disks averaged 39 mm, and minimum inhibitory concentrations ranged from .5 to 1 microgram/ml. Tissue and milk concentrations were determined from biopsy and quarter milk samples collected from eight cows treated with either intramammary infusion of 100 or 200 mg of ceftiofur, one or two intramuscular injections of 500 mg of ceftiofur, or combination therapy of intramammary infusion coupled with intramuscular injection. Three additional cows received two intramammary infusions of 200 mg of cephapirin at 24-h intervals. Intramuscular injections of ceftiofur resulted in tissue and milk concentrations below detectable limits. Staphylococcus aureus was not eliminated from infected mammary glands by infusion of 100 mg of ceftiofur or by injection of 500 mg of ceftiofur by 48 h after treatment. Combination therapy of 100 mg of ceftiofur infused and 500 mg injected reduced S. aureus numbers in milk and tissue markedly, as did infusion of 200 mg of ceftiofur. Cows receiving intramammary infusion of 200 mg of ceftiofur (two doses at 24-h intervals) had highest concentrations in milk (450 micrograms/ml at 4 and 6 h) and in tissue (.08 microgram/mg at 30 h). These concentrations are similar to those obtained with two 200-mg doses of cephapirin at 24-h intervals. Histologic analysis of mammary parenchymal tissues showed that combination therapy resulted in higher percentages of alveolar luminal area and lower percentages of interalveolar stroma compared with infusion or injection alone. Histology of quarters receiving combination therapy was not different from that of quarters receiving cephapirin infusion alone.

Topics: Animals; Cattle; Cephalosporins; Cephapirin; Female; Infusions, Parenteral; Injections, Intramuscular; Mammary Glands, Animal; Mastitis, Bovine; Microbial Sensitivity Tests; Milk; Staphylococcal Infections; Staphylococcus aureus