Antioxidant functions required for insusceptibility of Saccharomyces cerevisiae to tetracycline antibiotics.
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Cu,Zn superoxide dismutase (Sod1) is required for insusceptibility of Saccharomyces cerevisiae to oxytetracycline (OTC). Here we report that Sod1 is also required for insusceptibility to doxycycline (DOX). Furthermore, among a range of antioxidant and redox balance mutants, mac1 and ctr1 deletion strains exhibited marked sensitization to OTC and DOX. Certain mutants exhibited a slight sensitivity to methacycline and minocycline. Addition of copper suppressed antibiotic sensitivity. Thus, intracellular copper as well as superoxide dismutase can be critical for eukaryotic tolerance of several tetracycline antibiotics. (+info)
Incidence, distribution, and spread of tetracycline resistance determinants and integron-associated antibiotic resistance genes among motile aeromonads from a fish farming environment.
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A collection of 313 motile aeromonads isolated at Danish rainbow trout farms was analyzed to identify some of the genes involved in high levels of antimicrobial resistance found in a previous field trial (A. S. Schmidt, M. S. Bruun, I. Dalsgaard, K. Pedersen, and J. L. Larsen, Appl. Environ. Microbiol. 66:4908-4915, 2000), the predominant resistance phenotype (37%) being a combined oxytetracycline (OTC) and sulphadiazine/trimethoprim resistance. Combined sulphonamide/trimethoprim resistance (135 isolates) appeared closely related to the presence of a class 1 integron (141 strains). Among the isolates containing integrons, four different combinations of integrated resistance gene cassettes occurred, in all cases including a dihydrofolate reductase gene and a downstream aminoglycoside resistance insert (87 isolates) and occasionally an additional chloramphenicol resistance gene cassette (31 isolates). In addition, 23 isolates had "empty" integrons without inserted gene cassettes. As far as OTC resistance was concerned, only 66 (30%) out of 216 resistant aeromonads could be assigned to resistance determinant class A (19 isolates), D (n = 6), or E (n = 39); three isolates contained two tetracycline resistance determinants (AD, AE, and DE). Forty OTC-resistant isolates containing large plasmids were selected as donors in a conjugation assay, 27 of which also contained a class 1 integron. Out of 17 successful R-plasmid transfers to Escherichia coli recipients, the respective integrons were cotransferred along with the tetracycline resistance determinants in 15 matings. Transconjugants were predominantly tetA positive (10 of 17) and contained class 1 integrons with two or more inserted antibiotic resistance genes. While there appeared to be a positive correlation between conjugative R-plasmids and tetA among the OTC-resistant aeromonads, tetE and the unclassified OTC resistance genes as well as class 1 integrons were equally distributed among isolates with and without plasmids. These findings indicate the implication of other mechanisms of gene transfer besides plasmid transfer in the dissemination of antibiotic resistance among environmental motile aeromonads. (+info)
Selective uptake of 99mTc complexes and 67Ga in acutely infarcted myocardium.
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The suitability of various radiopharmaceuticals (99mTc-tetracycline analogs, 99mTc-glucoheptonate, 99mTc-diphosphonate, and 67Ga-citrate) for use in imaging acute myocardial infarction was assessed by determining their biologic distributions in experimentally infarcted dogs. The highest infarct-to-normal myocardial concentration ratio was found with 99mTc-diphosphonate (27.9:1); the highest infarct-to-liver ratio was also found with 99mTc-diphosphonate (15.9:1). The infarct-to-bone ratio, however, was 0.4:1 with 99mTc-diphosphonate. There was an excellent positive linear correlation between blood-flow reduction and uptake of the radiopharmaceutical after a threshold reduction in blood flow with 99mTc-glucoheptonate and 99mTc-tetracycline. Technetium-99m-tetracycline accumulated only in infarcted tissue while 99mTc-diphosphonate was increased in both ischemic and infarcted tissue. Thus, 99mTc-diphosphonate has characteristics best suited for scintigraphic imaging. Since 99mTc-tetracycline accumulates only in infarcted tissue, however, this tracer more accurately defines the size of an acute infarction. (+info)
Influence of cefazolin prophylaxis and hospitalization on the prevalence of antibiotic-resistant bacteria in the faecal flora.
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Faecal samples from 180 patients on admission and 108 patients at discharge were analysed for the prevalence and degree of resistance of Escherichia coli and enterococci. Discharged patients had received 24 h cefazolin prophylaxis and had a mean hospital stay of 10 +/- 5 days. The prevalence of resistance of E. coli to amoxicillin (P < 0.05), cefazolin (P < 0.05) and oxytetracycline was higher for patients at discharge (41, 12 and 35%) than for patients at admission (28, 2 and 27%). The prevalence at discharge was higher after short-term (< or =7 days) than after long-term (>7 days) hospitalization, being significant for amoxicillin only (P < 0.05). No significant changes were observed for the enterococci. (+info)
The effect of two different oxytetracycline treatments in experimental Ehrlichia phagocytophila infected lambs.
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The effect of 2 different oxytetracycline treatments in acute E. phagocytophila infected lambs was investigated. Twenty 5-month-old lambs of the Dala and Rygja breeds were used. Ten lambs were inoculated intravenously with a stabilate of an ovine E. phagocytophila strain. On the third day of fever, 4 lambs were given long-acting oxytetracycline (Terramycin prolongatum vet, Pfizer) (20 mg/kg) intramuscularly and another 4 lambs were given short-acting oxytetracycline (Terramycin vet, Pfizer) (10 mg/kg) intravenously for 5 consecutive days. The lambs were examined for the presence of Ehrlichia infection by blood smear evaluation, polymerase chain reaction (PCR) and antibody titre against E. equi. One month after the last antibiotic treatment, 250 ml citrate blood from each of these lambs were inoculated into each of 10 susceptible lambs, which were observed during the following 6 weeks. The results indicate that oxytetracycline given in the acute stage of the infection may effectively terminate the development of fever, rickettsemia and weight reduction in E. phagocytophila infected lambs. No difference was observed between the 2 treatment groups. However, at least 3 of 8 antibiotic treated lambs (37.5%) were still infected with granulocytic Ehrlichia 3 months after treatment. (+info)
Influence of ileo-caecal cannulation and oxytetracycline on ileo-caecal and rectal coliform populations in pigs.
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The effect of surgery (insertion of an ileo-caecal cannula) and a subsequent parenteral treatment with oxytetracycline on the ileo-caecal and rectal coliform populations in 7 Swedish Yorkshire castrates were studied. Samples were collected during surgery as well as 3, 7, 14 and 20 days post surgery. The diversity of the enteric coliform flora was initially high both in the ileo-caecal ostium and in rectum. No alteration in the diversity of the enteric coliform flora was observed following surgery and treatment with oxytetracycline. As the insertion of ileo-caecal cannulas did not affect the intestinal coliform flora this study gives support to the use of this technique to mirror processes in the small intestine of pigs. Further, the diversity of the enteric coliform flora was unaffected by the parenteral treatment with oxytetracycline. (+info)
New Mg2+-dependent oxytetracycline resistance determinant tet 34 in Vibrio isolates from marine fish intestinal contents.
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A new oxytetracycline (OTC) resistance (Otc(r)) determinant, Tet 34, was cloned from chromosomal DNA of Vibrio sp. no. 6 isolated from intestinal contents of cultured yellowtail (Seriola quinqueradiata). The transformant, containing cloned Tet 34, could grow in broth containing 25 microg of drug per ml with 10 mM MgCl2. Tet 34 encoded an open reading frame (ORF) 154 amino acids long. The amino acid sequence of the ORF was homologous to sequences of several bacterial xanthine-guanine phosphoribosyltransferases (XPRTs), which act in purine nucleotide salvage synthesis. Mg2+ binding site residues and the active site were highly conserved in XPRT and the ORF of Tet 34. The results suggest that Tet 34 encodes a new Mg2+-dependent Otc(r) mechanism. (+info)
The effect of administering long-acting oxytetracycline and tilmicosin either by dart gun or by hand on injection site lesions and drug residues in beef cattle.
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Forty yearling cattle were injected intramuscularly with long-acting oxytetracycline and subcutaneously with tilmicosin by dart gun or by hand in a chute 28 days prior to slaughter. The drugs caused injection site lesions and antibiotic residues in the neck and thigh that varied by technique, dose, and site. (+info)