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Biomedical subjects

G Ziv

Publications and source records attributed to G Ziv.

At least 109 records · Page 6Linked to original sources
PubMed1976

Activity of four cephalosporin antibiotics in vitro against bovine udder pathogens and pathogenic bacteria isolated from newborn calves.

The in vitro activity of chephaloridine, cephalexin, cefatrizine (BL-S640), and cephapirin (BL-P-1322) was evaluated by the serial dilution method against pathogenic gram-positive and gram-negative bacteria isolated from bovine udders and neonatal calf diseases. Cephapirin showed the comparatively greatest activity against the most common streptococcal species associated with bovine mastitis, whereas cephaloridine exhibited the best activity against Staphylococcus aureus. Cefatrizine was more active than the other cephalosporins against the gram-negative bacteria studied. In general, the minimal bactericidal concentration of each cephalosporin was two- to fourfold lower than the comparative value reported in the literature against the same type of pathogen of human origin.

Animals↗
PubMed1976

Clinical pharmacology of oxolinic acid in young dairy calves.

The in vitro sensitivity to oxolinic acid shown by pathogenic gram-negative bacterial isolates from young calves with diarrhea, pneumonia, and septicemia was investigated by the bute dilution method. Minimal bactericidal concentrations of the drug for 65.5% of the isolates were less than or equal to 1.56 mug/ml and for 90%, less than or equal to 6.25 mug/ml. Cross resistance between oxolinic acid and chloramphenicol, streptomycin, neomycin, colistin, ampicillin, gentamicin, and oxytetracycline was not observed. Oxolinic acid was orally administered to a group of calves at dose levels of 12.5 to 57.0 mg/kg, and sodium oxolinate was intramuscularly injected in another group of calves at dose levels of 12.5 and 20 mg/kg. In the 1st group, oxolinic acid was detected in blood serum 15 minutes later; peak serum concentrations averaged 25 mug/ml at 10 hours after treatment with 50 mg of the drug/kg and 3 mug/ml at 7 hours, with 12.5 mg of the drug/kg. In the 2nd group, the dose level of 20 mg of sodium oxolinate/kg resulted in mean peak serum concentration of 4 mug/ml, observed 1 hour after the drug was injected. The half-life of the drugs in serum was approximately 3.5 hours after they were orally or intramuscularly given. These investigations indicate that oxolinic acid could be used in the treatment of the common calf diseases.

Administration, Oral↗
PubMed1976

Application of the Limulus amoebocyte lysate test to the detection of gram-negative bacterial endotoxins in normal and mastitic milk.

The Limulus in vitro endotoxin assay was evaluated as a possible method for the prompt detection and measurement of endotoxins of Gram-negative bacteria in milk. Quantitative results were obtained following 1 h incubation of Limulus lysate and 10-fold dilutions of milk from normal quarters and from quarters of cows with clinical mastitis. This test was capable of detecting endotoxins associated with acute coliform mastitis. A positive Limulus reaction was recorded at dilutions ranging from 1: 10(4) to 1: 10(9) of milk from quarters affected with clinical mastitis due to coliform bacteria. Milk from normal quarters and from clinical mastitis cases due to Gram-positive bacteria was consistently negative to the test when diluted 1:10(3).

Animals↗
PubMed1976

Absorption of ampicillin derivatives from the bovine udder.

The rates at which ampicillin, amoxycillin, metampicillin, hetacillin, and pivampicillin are absorbed from the bovine udder were compared, with the absorption rate of (14C)urea as reference. Straight-line semilogarithmic plots of the percentage of unabsorbed drug against time were obtained, suggesting first-order kinetics for the absorption process. Ampicillin, metampicillin and hetacillin were most slowly absorbed. Amoxycillin was absorbed twice as fast as ampicillin. Pivampicillin was absorbed most rapidly-at more than three times the rate of ampicillin.

Amoxicillin↗
PubMed1976

Biological and ecological investigations on thiamineless dwarf-colony variants of Staphylococcus aureus of bovine udder origin.

Thiamineless dwarf-colony variants of Staphylococcus aureus (D strains) were compared with their homologous normal-colony variants and with normal S aureus. The majority of D strains tested in vitro exhibited biological features typical of S aureus. D strains, however, produced lower titres of alpha-haemolysin and this toxin was also produced by a smaller proportion of these strains. D strains and S aureus strains were equally susceptible to disinfectants used in dairy farming and were isolated with similar frequency from the skin of the udders of infected cows. Attempts at inducing and selecting D strains from normal S aureus by exposing the latter to antibiotics in vitro and in vivo have so far failed.

Animals↗
PubMed1976

Studies on the pathogenicity of thiamineless dwarf-colony variants of Staphylococcus aureus isolated from the bovine udder.

The pathogenic characteristics of thiamineless dwarf-colony variants of Staphylococcus aureus (D strains) were compared with those of normal S aureus isolated from the bovine udder. Intravenous injection of D strains into embryonated hen's eggs and intracranial inoculations into mice produced similar results to those with normal S aureus. Intramammary infusion of D strains into normal cows resulted in mastitis which was indistinguishable from the type produced by infusion of S aureus. Intramuscular injection of thiamine HCl into cows with chronic mastitis due to D strains did not alter the course of the disease, although normal sized S aureus colonies were isolated several days after thiamine injection.

Animals↗
PubMed1975

Distribution of labeled antibiotics in different components of milk following intramammary and intramuscular administrations.

In crossover trials, four lactating goats were given intramammary infusions and intramuscular injections of radioactivelabeled benzylpenicillin, spiramycin, chloramphenicol, dihydrostreptomycin, and tetracycline. Milk was collected after each treatment and the antibiotic contents in whole milk, skim milk, and whey were determined microbiologically and radiochemically and in cream and casein by radiochemical assay methods. Uptake of antibiotics by cream and casein was highly dependent on drug concentration, increasing with the decrease in antibiotic content in whole milk. Lipophilic chloramphenicol and tetracycline were concentrated in cream to a higher degree than the less lipophilic benzylpenicillin and dihydrostreptomycin. Antibiotic uptake by cream separated from whole milk after intramuscular injection was higher than after intramammary infusion. Antibiotic uptake by casein was independent of the route of administration and was highest for dihydrostreptomycin and tetracycline and lowest for benzylpenicillin.

Animals↗
PubMed1975

Absorption of antibiotics by the bovine udder.

Absorption of 39 antibiotics from the nonlactating bovine udder was compared with absorption of [carbon-14] urea as reference. First order kinetics characterized the absorption of urea and most of the antibiotics during the first 8 to 12 h after intramammary infusion. The absorption of polymyxin B, colistin, neomycin, spiramycin, and several tetracyclines was biexponential. The physicochemical properties of drugs which appeared to govern their absorption from the udder were the degree of lipid-solubility of the nonionized fraction and the dissociation constant. Antibiotic protein binding also influenced absorption. Lipid-solubility was the rate-limiting factor with drugs that are mainly dissociated in milk at pH 6.8. These compounds were absorbed at rates related to their degree of lipid-solubility of nonionized fraction. The concentration of the nonionized molecule in milk was the rate-limiting factor with drugs that were highly lipid-soluble. Results with a number of structurally-related antiobiotics, and with others of diverse structures and physical properties, added considerable confidence to the assumption that antibiotics are absorbed from the udder by nonionic (passive) diffusion. The blood-milk barrier behaves as an inert lipoid membrane to these drugs.

Absorption↗
PubMed1974

Evaluation of rifamycin SV and rifampin kinetics in lactating ewes.

Serum and milk concentrations of rifamycin SV and rifampin were determined in lactating ewes after a single intravenous injection, and pharmacokinetic parameters were evaluated by the two-compartment open-system model. Rifampin was distributed throughout a greater volume than rifamycin SV and was eliminated more slowly from the body. The concentrations of the two drugs, both lipophilic weak acids, in milk after intravenous or intramuscular injection were lower than in serum, but rifampin was detected in milk sooner and for longer periods than rifamycin SV. Under constant serum drug concentrations, the observed milk/serum ultrafiltrate concentrations ratios (0.19 to 0.29 for rifamycin SV, and 0.90 to 1.28 for rifampin) were close to the calculated ratios derived from the pH-pK passive diffusion concept.

Animals↗
PubMed1974

Epidemiological and biochemical studies on thiamine-less dwarf-colony variants of Staphylococcus aureus as etiological agents of bovine mastitis.

Dwarf-colony (D) variants of Staphylococcus aureus are relatively widespread etiological agents of bovine mastitis in Israel. D strains grow on ordinary solid nutrient media with pinpoint, transparent colonies. An epidemiological study indicated that these variants are more communicable than normal (N) S. aureus strains. Biochemically, several types of metabolic defects have been demonstrated among the D strains: strains from one herd were pantothenate-less, most of the other isolates were thiamine-less, and a few of them were both thiamine-and pantothenate-less. Among the thiamineauxotrophs were a few (from one herd) which were unable to concentrate thiamine-thiazole, whereas all of the other strains required thiamine-pyrimidine (HMP) in the form of pyrophosphate (HMP-PP). At least some of these D strains were defective in three functions: concentrative uptake of HMP, phosphorylation of HMP, and phosphorylation of HMP-monophosphate. Since mutants with normal growth occurred readily, we assumed that the information for these three functions exists on a polycistronic operon. Quantitative requirements for HMP-PP varied highly among the D strains, and other data also indicated that HMP-PP-requiring strains had not developed from a common source.

Animals↗