Bacterial complications of postpartum uterine involution in cattle.

The bacterial contamination of the postpartum uterus is a frequent finding which by itself does not disturb the anatomical and histological restoration of tubular genital tract. The improper balance between uterine infection and the intrauterine antimicrobial self-defence mechanisms, however, often results in complications, such as puerperal metritis, clinical endometritis, pyometra and subclinical endometritis. After reviewing the bacteriology of uterine involution, and the predisposing factors for its bacterial complications, this paper defines the different clinical forms, and summarizes their pathology, furthermore, the recent progress in diagnostic considerations and principles of current treatments for these diseases of bovine genitals.

Acyloxyacyl hydrolase activity of neutrophil leukocytes in normal early postpartum dairy cows and in cows with retained placenta.

Acyloxyacyl hydrolase (AOAH) is an enzyme of bovine polymorphonuclear neutrophil leukocytes (PMN) that is capable of detoxifying endotoxin (25). The activity of AOAH in PMN isolated from the blood was investigated in dairy cows that expelled the fetal membranes normally (Group NFM) and in cows with retained fetal membranes (Group RFM) to obtain better insight into the role of the AOAH enzyme of neutrophils in endotoxin-related diseases, which occur frequently in dairy cows during the early postpartum period, especially in RFM cows. Twenty early postpartum dairy cows were used in the study: 13 NFM cows and 7 RFM cows. In the RFM cows, the percentage of PMN in blood (29+/-4%) was significantly (P<0.05) lower than in NFM cows (43+/-4%). The average AOAH activity in RFM cows (mean +/- SEM = 89+/-13 pmol fatty acid/10(7) PMN/h) was lower than in NFM cows (107+/-6 pmol fatty acid/10(7) PMN/h), but the difference in neutrophil AOAH activity between the 2 groups was not significant. There was also a higher percentage of immature neutrophils in isolated leukocyte suspensions from RFM cows (22+/-8%) than from NFM cows (15+/-4%), so that impairment of AOAH activity in early postpartum cows could be explained, in part, by immaturity of the neutrophils. These results suggest that the decreased AOAH activity of PMN could play a role in the pathogenesis of endotoxin-related diseases in dairy cows during the early postpartum period.

Relationship between intra-uterine bacterial contamination, endotoxin levels and the development of endometritis in postpartum cows with dystocia or retained placenta.

A study was conducted to investigate the relationship between intra-uterine bacterial contamination, endotoxin levels and the development of endometritis in cows that experienced a dystocia or retained their placenta. Fifteen healthy cows, 31 cows with retained placenta (RP) and 13 cows that had dystocia were clinically examined 1 or 2 days after parturition when a uterine swab for bacteriological examination was taken. In addition, plasma and uterine lochia samples were collected to determine lipopolysaccharide (LPS) and the plasma IgG anti-LPS concentrations. Subsequently, 15 RP and 6 dystocia cows were initially left untreated and another uterine swab was collected at 2 and 4 wk postpartum. Immediately after calving, RP cows had significantly higher LPS levels in uterine lochia (average of 2.24 x 10(4) Endotoxin Units (EU)/mL) as compared to dystocia and healthy postpartum cows (average of 0.10 and 0.26 EU/mL, respectively). However, plasma LPS levels were below the detection limit (<0.036 EU/mL platelet-rich plasma) in all groups of cows. IgG anti-LPS levels in plasma were not significantly different between the 3 groups immediately postpartum (average of 26, 16 and 44 Median Units (MU)/mL) for healthy, dystocia and RP cows, respectively), but they were significantly lower when compared to plasma IgG anti-LPS levels of healthy cows at more than 2 months postpartum (mean 83 MU/mL). High LPS levels in lochia at 1 or 2 days postpartum were significantly related to abnormal cervical discharge, the presence of Escherichia coli, black pigmented gram-negative anaerobes and Clostridium spp. shortly after calving, and Arcanobacterium pyogenes and gram-negative anaerobes in the uterus at 14 days postpartum. These results suggest that the presence of E. coli and LPS (endotoxins) in lochia early postpartum favor the development of uterine infections by A. pyogenes and gram-negative anaerobes later postpartum. LPS were not observed in plasma, suggesting that either they are not absorbed into the blood, or they are efficiently detoxified by IgG anti-LPS or other detoxification mechanisms.

Serotyping scheme for Staphylococcus aureus isolated from cows with mastitis.

OBJECTIVE: To identify the Staphylococcus aureus capsular serotypes that are not typable, using capsular serotypes 5 and 8, which are currently used to type S aureus isolated from cows with mastitis. SAMPLE POPULATION: Milk samples (n = 273) from cows with mastitis in 178 dairy herds in California, Wisconsin, Michigan, Texas, and New York that were collected by state diagnostic laboratories and S aureus-positive milk samples collected by Veterinary Health Services in the United Kingdom (15), France (22), The Netherlands (36), and Germany (21). PROCEDURE: Capsular serotyping of coded isolates was performed by use of direct cell agglutination and immunoprecipitation of cell extracts with antisera specific for capsular types 5 and 8 and a newly developed S aureus serotyping antiserum 336. RESULTS: In the United States, S aureus capsular types 5 and 8 accounted for 18 and 23% of the isolates, respectively, and type 336 accounted for 59%. Percentage of capsular serotypes in European samples were as follows: type 5 = 34%, type 8 = 34%, type 336 = 30%, and nontypable = 2%. CONCLUSIONS: Serotypes 5 and 8 accounted for only 41% of S aureus isolates from US milk samples, but accounted for 70% of isolates from European milk samples. Addition of the newly developed serotyping antiserum 336 to the typing scheme accounted for 100% of US samples and 98% of European samples and will enable development of a more comprehensive S aureus vaccine.

Effects of endotoxin-induced mastitis on the pharmacokinetic properties of aditoprim in dairy cows.

Plasma disposition of aditoprim, a new dihydrofolate reductase inhibitor, was studied in healthy cows and cows with endotoxin-induced mastitis. A single dose of 5 mg of aditoprim/kg of body weight was administered IV to 5 healthy cows and to the same cows 3 weeks later at 2 hours after intramammary infusion of 0.1 mg of endotoxin into the rear quarters. Mastitis developed in all endotoxin-infused quarters and cows had systemic signs of disease (fever, tachycardia, depression) from 2 to 10 hours after infusion of endotoxin. Pharmacokinetic characteristics of aditoprim in healthy cows were a large volume of distribution (6.28 L/kg), a systemic clearance of 0.82 L/h/kg, and an elimination half-life of 7.26 hours. In cows with mastitis, plasma concentrations of aditoprim were lower between 5 and 26 hours after injection. The systemic clearance (1.00 L/h/kg) and the volume of distribution (12.25 L/kg) were significantly higher in cows with mastitis, but elimination half-life was not significantly different. The lower plasma concentrations of aditoprim between 5 and 26 hours after injection in cows with mastitis are explained by fluid compartment shifts and/or blood flow changes induced by mastitis, although increased elimination of aditoprim in cows with mastitis cannot completely be ruled out. The antibacterial activity of aditoprim is nearly the same as that of trimethoprim. The longer elimination half-life time of aditoprim, however, indicates that it may have a practical pharmacotherapeutic advantage over trimethoprim.

Host defence and bovine coliform mastitis. Host defence mechanisms and characteristics of coliform bacteria in coliform mastitis in bovine: a review.

This paper reviews the microbial properties that underlie the virulence of coliform microorganisms causing bovine mastitis. The interaction between the coliform bacteria and teat-duct defence, humoral defence and phagocytic cells is discussed. The functioning of these host-defence mechanisms seems to exert a major role in the course of a coliform infection of the udder.

Pathophysiological effects of endotoxins in ruminants. 2. Metabolic aspects.

Metabolic disturbances following intravenous and intramammary administration of endotoxins in ruminants are described. In contrast to the similarity in response of blood biochemical parameters after intravenous and intramammary administrations of endotoxins, responses in plasma concentrations of enzyme activities, the thyroid hormones, cortisol, and somatotropin differ markedly. Biochemical changes in blood after endotoxin administration are predominantly dose-dependent; thus some of the biochemical parameters - especially plasma concentrations of Fe and Zn - serve also to evaluate the effects of certain drugs in endotoxin models. Changes in milk composition have been documented only after intramammary infusion of endotoxins and can partly be explained by the increased permeability of the blood/milk barrier. Appearance and production of milk returns to normal within a week after intramammary endotoxin treatment, indicating that the mammary gland is only temporarily damaged by endotoxin-induced mastitis.

Pathophysiological effects of endotoxins in ruminants. 1. Changes in body temperature and reticulo-rumen motility, and the effect of repeated administration.

Data from the literature on the clinical effects of bacterial endotoxins in ruminants are reviewed. Special attention is paid to the effects on body temperature and reticulo-rumen motility. Furthermore, the effects of repeated intravenous injection of endotoxin are summarised. Pathophysiological disturbances after intramammary infusion of endotoxins proved to be identical to those found after intravenous injection of non-lethal doses. Strikingly, however, no marked inhibitory effect on rumen motility nor abortion was observed after intramammary infusion of endotoxins. Moreover, in cows that were made tolerant to endotoxin by daily intravenous injections, intramammary infusion of one-fifth of this daily dose produced a maximum effect on body temperature and plasma Zn concentrations. This suggests that inflammatory endogenous mediators were released in the udder and then absorbed into the blood circulation, rather than the absorption of endotoxin.

Pharmacokinetics and renal clearance of oxytetracycline after intravenous and intramuscular administration to dairy cows.

Following intravenous administration of an oxytetracycline-HC1 and an oxytetracycline-dihydrate formulation to dairy cows, no statistical difference could be found between the pharmacokinetic parameters, derived from the three-compartment model, of these preparations. Urinary recovery was continued for a period of 72 h following intravenous or intramuscular OTC administration. The recovery of OTC in the urine in the 72-h period was in the range of 73% to 96% of the available dose administered. The renal OTC clearance, the renal creatinine clearance, the urinary flow, and the interrelationships of these were determined on the basis of urine and plasma data. The mean OTC renal clearance ranged from 482 to 1050 ml/min and the creatinine clearance from 651 to 1304 ml/min. The OTC and creatinine clearances were significantly correlated to the urine flow up to 30 ml/min. The total body clearance and renal clearance values were of the same order of magnitude, and along with the urine recovery data they provided evidence of predominantly renal route of OTC elimination in dairy cows. The renal OTC elimination is the net result of mainly glomerular filtration, partly tubular secretion, minus reabsorption in the urogenital tract.

Comparative pharmacokinetics and bioavailability of eight parenteral oxytetracycline-10% formulations in dairy cows.

In plasma and milk the oxytetracycline (OTC) concentrations were determined following a single intramuscular administration of eight 10%-formulations to dairy cows at a dose of approximately 5 mg/kg. Two of these formulations were injected intravenously to obtain reference values of the drug's pharmacokinetic parameters. The eight formulations were compared and evaluated pharmacokinetically with respect to absorption rate, peak plasma and milk OTC concentrations, biological half-life, and relative bioavailability. The mean maximum plasma OTC concentrations, ranging from 2.0 to 4.1 micrograms/ml, were achieved between 4 and 12 hours post injection, depending on the formulation involved. The mean maximum milk OTC concentrations, in the range between 0.92 and 1.43 micrograms/ml, were achieved 12 to 24 h p.i. The OTC milk concentration-time profile ran parallel to the OTC plasma concentration-time profile. After intravenous administration the time for the appearance of OTC in milk was shorter (1-2 hours p.i.), the peak milk OTC concentration was higher (1.7-1.9 micrograms/ml) and achieved earlier (6-8 h p.i.), and the OTC persistence in milk shorter than after i.m. administration. Formulations exhibiting the lowest clinically noticeable irritation showed the most favourable pharmacokinetic characteristics: rapid absorption with the highest peak plasma OTC concentrations and good bioavailability. The plasma and milk protein binding for OTC was respectively 71.7 +/- 7.4% and 84.8 +/- 5.45%. Withdrawal times for milk and edible tissues are presented on the basis of preset tolerance or detection limits.

Flunixin meglumine and flurbiprofen in cows with experimental Escherichia coli mastitis.

The effect of flunixin meglumine and flurbiprofen on the course of experimental Escherichia coli mastitis was examined. Nine cows (within one month post partum) were inoculated intramammarily with 20 x 10(5) viable E coli in both rear quarters. Three cows remained untreated (controls); three cows received three injections of flunixin meglumine and three cows received flurbiprofen as two intravenous infusions. Flunixin meglumine and flurbiprofen were initially given before clinical signs were observed. Treatment was repeated if the cows' temperature increased by more than 1 degree C. In the untreated cows, rectal temperature and heart rate increased from three hours after infection, and rumen motility (both frequency and amplitude) decreased from four hours after infection. Treatment with flunixin meglumine or flurbiprofen almost completely abolished the febrile response during the first nine hours after infection, and the decrease in rumen motility was less pronounced in the treated animals. These results suggest that the decrease in rumen motility during E coli mastitis is at least partly due to a mechanism involving prostaglandin.

[Escherichia coli mastitis in cattle. I. Clinical diagnosis and epidemiological aspects]. / Escherichia coli-mastitis bij het rund. I. Klinische diagnostiek en epidemiologische aspecten.

The diagnostic aspects, incidence, risk factors and prevention of coliform mastitis are reviewed in the present paper. It is concluded that it is not possible to establish an accurate diagnosis of coliform mastitis, which is based on a specific clinical symptom differentiating it from other forms of mastitis. Not any single symptom or combination of symptoms is specific for coliform mastitis. The importance of coliform mastitis in dairy cattle showed a marked increase during the last few decades. Successful programmes for the prevention of mastitis reduced the importance of contagious organisms, but the overall incidence of mastitis has remained unchanged; therefore, the proportion of cases of coliform mastitis increased. The observation that coliform micro-organisms are common bacteria causing mastitis in herds with low bulk milk somatic cell counts implies that the future of the dairy industry will be associated with particular risks. Factors involving the risk of coliform mastitis are divided into cow level factors and herd level factors. The most important cow level factors were: leaking milk in between milkings, lesions of the teats and a reduced capacity of the immune system. Risk factors on the herd level include: the bedding material, the design of cubicles, exposure to daylight in summer-time, exposure to dirt and the use of dry-cow therapy. The possible role of antibiotic dry-cow treatment and teat dipping in colonisation resistance is discussed. Preventive programmes designed to reduce the incidence of coliform mastitis have not been very successful so far.

[Escherichia coli mastitis in cattle. II. Pathogenesis and symptomatic therapy]. / Escherichia coli-mastitis bij het rund. II. Pathogenese en symptomatische therapie.

The pathogenesis, course run by the disease, and symptomatic treatment of mastitis due to Escherichia coli in dairy cattle are reviewed in relation to the functioning of cellular and humoral defence mechanisms. The systemic symptoms of disease during mastitis caused by E. coli are attributed to the release and subsequent absorption from the udder of endogenous inflammatory mediators, rather than the direct absorption of endotoxins into the circulation. The course run by the disease during mastitis due to E. coli varies considerably. Reasons for these variations include genetic variation, stage of lactation and the function of humoral and cellular defence mechanisms.

[Escherichia coli mastitis in cattle. III. Antibacterial therapy]. / Escherichia coli-mastitis bij het rund. III. Antibacteriële therapie.

This review paper is concerned with antibacterial therapy of mastitis caused by Escherichia coli. The choice of an antibacterial agent is discussed, and nine criteria are referred to, on which this choice should be based. In the second part possible forms of antibacterial treatment are discussed. Literature on parenteral and local treatment of mastitis due to E. coli is scarcely available. The evaluation of antibacterial drugs is mainly based on MIC values and pharmacokinetic studies in normal animals. Unfortunately, results of clinical trials are hardly available. Today combinations of trimethoprim/sulphonamide apparently are the best available choice for the parenteral treatment of mastitis caused by E. coli. Infusion of polymyxins or gentamycin is discussed as a method of intramammary therapy.

[Pathogenic studies of Escherichia coli mastitis]. / Pathogenetisch onderzoek naar Escherichia coli mastitis.

In this paper research about the pathogenesis of Escherichia coli mastitis, executed by the Department of Herd Health and Reproduction, is reviewed. The use of experimental infection models to study the systemic clinical symptoms of an Escherichia coli mastitis and the effect of anti-inflammatory drugs on this symptoms are described. Additionally, correlations between pre-infection in vitro leucocyte function tests and the severity of an Escherichia coli infection are discussed. Finally, some future developments and their possible applications are revealed.

Pharmacodynamics of ibafloxacin in micro-organisms isolated from cats.

The pharmacodynamic properties of ibafloxacin were investigated in micro-organisms isolated from cats. Minimal inhibitory concentrations (MIC) of ibafloxacin (racemate, R- and S-enantiomers) and its metabolites (7-hydroxy- and 8-hydroxy-ibafloxacin) and time-kill kinetics were determined against Gram-negative and Gram-positive bacteria isolated from dermal and respiratory and urinary tract infections in cats. Racemic ibafloxacin has a broad spectrum of bactericidal activity against Gram-negative and some Gram-positive bacteria. Escherichia coli and Pasteurella, Klebsiella and Staphylococcus spp. are commonly isolated from feline infections and all are susceptible to ibafloxacin (MIC90 < or = 0.5 microg/mL), whereas Pseudomonas aeruginosa, Proteus mirabilis and Streptococcus spp. are considered intrinsic resistant. Microbiological activity resides primarily in the S-enantiomer of ibafloxacin whereas the R-enantiomer is less active. Killing curves using concentrations of racemic ibafloxacin and 8-hydroxy-ibafloxacin, which are representative of the in vivo situation observed in cats, showed at least 99.9% reduction in viable bacterial isolates from feline clinical samples over 24 h. Bacterial eradication was achieved in cats with Cmax/MIC and AUC/MIC values much lower than the target values previously established in man and laboratory animals. Additional studies in dogs and cats are necessary to define more clearly the surrogate markers of antibacterial activity (i.e. Cmax/MIC, AUC/MIC ratios), which are associated with a good clinical response.

Pharmacokinetics of ibafloxacin in healthy cats.

The pharmacokinetics of ibafloxacin following single and repeated administration of an oral gel formulation and the effect of food intake were investigated in cats. Ibafloxacin is a chiral fluoroquinolone available for clinical use as a racemic mixture of the R- and S-enantiomers. Plasma concentrations of ibafloxacin and its metabolites were determined using microbiological, LC-MS-MS and enantioselective capillary zone electrophoresis assays. Ibafloxacin was absorbed rapidly [time of maximum concentration (tmax) 2-3 h], reaching a mean maximum concentration (Cmax) of approximately 2.1 and 1.6 microg/mL for R- and S-ibafloxacin, respectively, following a single oral administration of the racemate at 15 mg/kg. Once absorbed, ibafloxacin was metabolized to 7-hydroxy-ibafloxacin and mainly to 8-hydroxy-ibafloxacin. Following repeated oral administration, significant increases in Cmax and AUC of ibafloxacin and its less active metabolites (racemic or enantiomers) were observed between the first and the tenth day of treatment. This twofold exposure increase in concentrations of ibafloxacin and its metabolites may contribute additionally to the efficacy of this drug in the treatment of feline bacterial infections. Single and repeated doses of ibafloxacin were well tolerated by cats. Food promoted the absorption of ibafloxacin, doubling Cmax and increasing AUC and slightly delaying tmax. High concentrations of the metabolites, mainly 8-hydroxy- and 7-hydroxy-ibafloxacin were excreted in urine, either unchanged or as glucurono-conjugates.

Effect of cephapirin and mecillinam on the phagocytic and respiratory burst activity of neutrophil leukocytes isolated from bovine blood.

Antimicrobial therapy is the most commonly used treatment of bacterial infections in dairy cows. Polymorphonuclear neutrophil leukocytes (PMN) play an important role in the first line defence against invading bacteria and it is important that the function of PMN is not compromised by antibiotics. We investigated the in vitro effect of cephapirin, a first generation cephalosporin, and mecillinam, an amidinopenicillin with activity against mainly Gram-negative bacteria, on phagocytosis and respiratory burst activity of PMN isolated from bovine blood. After in vitro incubation of PMN with different concentrations of the antibiotics, phagocytosis was evaluated by flow cytometry and respiratory burst activity was evaluated by registration of chemiluminescence (CL) with a luminometer. None of the investigated concentrations of cephapirin and mecillinam had an effect in vitro on phagocytosis of Escherichia coli by PMN. At high concentrations (100 and 1000 microg/mL), cephapirin and mecillinam reduced the respiratory burst activity of PMN. Part of these suppressive effects could be ascribed to oxidant scavenging. Inhibitory effects of cephapirin were stronger than mecillinam. In conclusion, cephapirin and mecillinam did not seem to affect antibacterial activity of PMN isolated from bovine blood in vitro at therapeutic concentrations.

In vitro and in vivo pharmacodynamic properties of the fluoroquinolone ibafloxacin.

The pharmacodynamic properties of a new veterinary fluoroquinolone antimicrobial agent, ibafloxacin, were evaluated. Minimal inhibitory concentrations (MIC), time-kill kinetics, postantibiotic effect (PAE) and postantibiotic subminimal inhibitory concentration effects (PA-SME) were determined against pathogenic canine Gram-negative and Gram-positive bacterial isolates from dermal, respiratory and urinary tract infections. The synergistic interactions between ibafloxacin and its main metabolite, 8-hydroxy-ibafloxacin were investigated. Finally, the efficacy of ibafloxacin was tested in in vivo canine infection models. Ibafloxacin had good activity against Pasteurella spp., Escherichia coli, Klebsiella spp., Proteus spp. and Staphylococcus spp. (MIC90=0.5 microg/mL), moderate activity against Bordetella bronchiseptica, Enterobacter spp. and Enterococcus spp. (MIC50=4 microg/mL) and low activity against Pseudomonas spp. and Streptococcus spp. The time-killing analysis confirmed that ibafloxacin was bactericidal with a broad spectrum of activity. The PAE and PA-SME were between 0.7-2.13 and 1-11.5 h, respectively. Finally, studies in dog models of wound infection and cystitis confirmed the efficacy of once daily oral ibafloxacin at a dosage of 15 mg/kg. Additional studies are needed to better define the importance of AUC/MIC (AUIC) and Cmax/MIC ratios on the outcome of fluoroquinolone therapy in dogs.

Pharmacokinetics of ibafloxacin following intravenous and oral administration to healthy Beagle dogs.

The pharmacokinetics of ibafloxacin, a new veterinary fluoroquinolone antimicrobial agent, was studied following intravenous (i.v.) and oral administration to healthy dogs. The mean absolute bioavailability of ibafloxacin after oral doses of 7.5, 15 and 30 mg/kg ranged from 69 to 81%, indicating that ibafloxacin was well absorbed by dogs. Ibafloxacin was also absorbed rapidly [time of maximum concentration (t(max)) 1.5 h], reaching a mean maximum concentration (C(max)) of 6 microg/mL at 15 mg/kg, well distributed in the body [large volume of distribution at steady state (V(ss)) and V(area) of 1.1 L/kg and 4 L/kg, respectively], and exhibited an elimination half-life of 5.2 h and a low total body clearance (8.7 mL/min/kg). Both C(max) and area under the concentration-time curve (AUC) showed dose proportionality over the dose range tested (7.5-30 mg/kg). The pharmacokinetics of ibafloxacin was similar following single and repeated dosage regimens, implying no significant accumulation in plasma. Food promoted the absorption of ibafloxacin by increasing C(max) and AUC, but did not change t(max). High amounts of the metabolites, mainly 8-hydroxy- and, 7-hydroxy-ibafloxacin were excreted in urine and faeces, either unchanged or as glucuronide conjugates. Following oral administration of 15 mg ibafloxacin/kg, the total recovery of ibafloxacin, its metabolites and conjugates in urine and faeces was 61.9-99.9% of the dose within 48 h.