An anomalous finding in a sensitivity test.
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Anti-Bacterial Agents↗
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Results for “Microbial Sensitivity Tests”
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Antifungal activity of DNA-lipid complexes and DNA-lipid films against Candida species.
In this study amphiphilic lipids, DNA-lipid complexes, and DNA-lipid films were prepared, and their antifungal activity against Candida species was examined. The amphiphilic lipids were synthesized from a reaction of glycine or L-alanine with n-alkyl alcohol in the presence of p-toluene sulfonic acid. DNA-lipid complexes, which were prepared by the simple mixing of DNA and amphiphilic lipids, were insoluble in water. Self-standing, water-insoluble DNA-lipid films were prepared by casting the DNA-lipid complexes from a chloroform/ethanol solution. The antifungal activities of the lipids and DNA-lipid complexes against the Candida species were evaluated by minimum inhibitory concentrations (MICs); those of DNA-lipid films were evaluated by the disk diffusion method. The seven kinds of lipids, DNA-lipid complexes, and DNA-lipid films showed antifungal activity, and no differences were seen in the antifungal activities between glycine and L-alanine derivatives. The lipids, DNA-lipid complexes, and DNA-lipid films, which have shorter alkyl chain length in lipids, showed antifungal activity against all Candida species. However, the effect of antifungal activity against Candida species decreased with increased alkyl chain length in lipids. In this study, it was found that lipids, DNA-lipid complexes, and films with a decyl or dodecyl group exhibit more favorable antifungal activity.
Animals↗
The product of the cysK gene of Bacillus stearothermophilus V mediates potassium tellurite resistance in Escherichia coli.
The nucleotide sequence of a 4,539 bp fragment of Bacillus stearothermophilus V mediating tellurite resistance in Escherichia coli was determined. Four ORFs of more than 150 amino acids encoding polypeptides of 244, 258, 308, and 421 residues were found in the restriction fragment. E. coli cells harboring a recombinant plasmid containing the Ter determinant express, when challenged with tellurite, a 32 kDa protein with an amino terminal sequence identical to the ten first residues of the 308 ORF. This ORF shows great similarity with the cysteine synthase gene (cysK) of a number of organisms. Recombinant clones carrying the active cysK gene have minimal inhibitory concentrations to K2TeO3 that were tenfold higher than those determined for the host strain or that of clones carrying ORFs 244, 258, and 421. Introduction of the B. stearothermophilus V cysK gene into a cysK strain of Salmonella typhimurium LT2 resulted in complementation of the mutation as well as transfer of tellurite resistance.
Cloning, Molecular↗
Retrograde root filling using antibiotic-containing, radiopaque, bone cement.
An investigation is reported on the in-vitro behaviour, characteristics and properties of three gentamicin-containing radiopaque bone cements that are considered to be promising retrograde root-filling materials. Three commercially available cements, CMW-1G, CMW-3G and Palacos R with gentamicin were studied with regard to bacteriocidal properties, tissue compatibility in cell culture, and ability to seal tooth cavities as evidenced by dye diffusion. Results were compared and contrasted with those obtained with an amalgam. The antibiotic-containing cements investigated are considered to have some distinct advantages over amalgam when used as retrograde root-filling materials in vitro. Amalgam was found to have poor bacteriocidal properties and poor tissue compatibility but slightly better apical sealing abilities than the cements. No apparent drawbacks were found with the cements.
Acrylic Resins↗
Synthesis and antiinflammatory activity of 4-amino-2-aryl-5-cyano-6-{3- and 4-(N-phthalimidophenyl)} pyrimidines.
Six new 4-amino-5-cyano-2,6-diarylpyrimidines 5a-h has been synthesized in a facile manner by reacting the appropriate arylamidines 4a-d with bisnitriles 3a-e. Reduction of the nitro group of 5a-e using Pd in ethyl acetate furnished 6a-e in good yields. Reaction of 6a-e individually with phthalic anhydride yielded 7a-e in good to excellent yields. The newly synthesized heterocycles were characterized by IR, (1)H-NMR and mass spectral data. Compounds 5f-h and 7a-e were also evaluated against inflammation. Pyrimidines 5g, h exhibited better antiinflammatory activity when compared with acetylsalicylic acid (ASA). Phthalimide derivatives 7a-e also presented antiinflammatory activity, and three of them, viz., 7a-c have been found to be twice more active than aspirin. Cytotoxical evaluations of compounds 7a-e using neoplastic cells (NCI-H(292) and Hep-2) presented 41% of growth inhibition of neoplastic cells NCI-H(292).
Animals↗
Characterization of Salmonella dublin and Salmonella typhimurium (Copenhagen) isolates from cattle.
Eight Salmonella typhimurium (Copenhagen) and eight Salmonella dublin isolates from cattle were compared by their antibiotic resistance patterns, by their production of colicin, aerobactin, haemolysin and capsule, by their possession of transmissible R plasmids and the spvC gene, and by their ability to invade and replicate within cultured epithelial cells. The two groups differed in their antibiotic resistance profiles, with more of the host-adapted S. dublin isolates resistant to tetracycline than were the non-host-adapted S. typhimurium (Copenhagen) group, but more of the S. typhimurium (Copenhagen) isolates resistant to the other antibiotics tested. None of the isolates produced colicin, but all produced aerobactin. One isolate in each group was encapsulated. All of the S. typhimurium (Copenhagen) and S. dublin isolates contained plasmids, and all of them contained the spvC-homologous sequences. Four of the S. typhimurium (Copenhagen) isolates were able to transfer an R plasmid to a recipient organism by conjugation. One of the five S. dublin isolates, which showed resistance to some of the antibiotics tested, was able to transfer an R plasmid by conjugation. Both groups of isolates invaded cultured epithelial cells to a similar degree after 1 h, but the S. dublin isolates reached significantly higher levels within the cells than did S. typhimurium (Copenhagen) after 9 h. This ability may, in part, explain the association of S. dublin with more severe forms of salmonellosis and prolonged carrier states. Further study of the intracellular growth of these isolates seems warranted.
Animals↗
Yersinia pestis infection in Vietnam. I. Clinical and hematologic aspects.
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Adolescent↗
Bactericidal activity of beta-lactams and amikacin against Haemophilus influenzae: effect on endotoxin release.
Ampicillin or cefotaxime, alone or in combination with amikacin, were tested at levels achievable in CSF for bactericidal activity against eight clinical isolates of Haemophilus influenzae serotype b. Endotoxin release was determined by the limulus amoebocyte lysate test and by macrophage tumour necrosis factor production for each beta-lactam antibiotic, alone and in combination with amikacin. Accelerated killing was observed when amikacin was added to ampicillin or cefotaxime; however, the additional antibiotic-induced bacterial lysis observed after the addition of amikacin to beta-lactam antibiotics was not associated with an increase in endotoxin release.
Amikacin↗
Randomized, double-blind study of grepafloxacin versus amoxycillin in patients with acute bacterial exacerbations of chronic bronchitis.
This randomized, multicentre, double-blind, double-dummy study compared the efficacy and safety of grepafloxacin and amoxycillin in acute bacterial exacerbations of chronic bronchitis (ABECB). Patients were randomized to receive grepafloxacin 400 mg or 600 mg od, or amoxycillin 500 mg tds, for 7 or 10 days. The trial recruited 656 patients, of whom 566 (86%) completed the study. Clinical success rates at the 2 week follow-up visit for the population evaluable for clinical efficacy were 82% (165/202 patients) in the grepafloxacin 400 mg group, 85% (175/206) in the grepafloxacin 600 mg group and 85% (172/203 patients) in the amoxycillin group. The 95% confidence interval confirmed the equivalence of the two grepafloxacin doses and amoxycillin, with no significant difference between the grepafloxacin groups. The microbiological success rates at follow-up showed equivalence between the grepafloxacin 400 mg and amoxycillin groups: 86% (144/168 isolates) and 83% (162/195), respectively. The grepafloxacin 600 mg group achieved a statistically significantly higher eradication rate (92%, 150/164; 95% CI 2.0%, 16.1%) than the amoxycillin group in the follow-up assessment for microbiological and clinical efficacy (evaluable population). There was no significant difference between the two grepafloxacin treatment groups (95% CI -13.3%, 0.9%; P= 0.087). All three treatment regimens successfully eradicated the pathogens most commonly isolated during the study, including Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae. Grepafloxacin had a good safety profile, comparable to that of amoxycillin, although grepafloxacin 600 mg was associated with a higher incidence of nausea, dyspepsia and taste perversion than amoxycillin. It can be concluded that grepafloxacin 400 mg or 600 mg od is as effective as amoxycillin 500 mg tds in the treatment of ABECB.
Adolescent↗
Randomized, double-blind, comparative study of grepafloxacin and amoxycillin in the treatment of patients with community-acquired pneumonia.
This randomized, multicentre, double-blind, double-dummy study assessed the efficacy and safety of 7 or 10 day regimens of grepafloxacin, 600 mg od, compared with amoxycillin, 500 mg tds, in the treatment of community-acquired pneumonia (CAP). A total of 264 patients were recruited at 43 centres (127 received grepafloxacin and 137 received amoxycillin), of whom 207 patients (78%) completed the study. Clinical and microbiological efficacy were assessed at the end-of-treatment visit (3-5 days after the last dose) and at the follow-up visit (28-42 days after the last dose). At follow-up, patients in the evaluable population treated with grepafloxacin demonstrated a clinical response rate (76%; 87/114) equivalent to that seen with amoxycillin (74%, 85/111, 95% CI = -12%, 10%) while, in the intent-to-treat population with a documented bacterial pathogen, the clinical success rate in the grepafloxacin group (78%, 29/37) was significantly higher than in the amoxycillin group (58%, 28/48), 95% CI = 2%, 43%). In patients from the evaluable population in whom the pathogens were documented the clinical success rate favoured grepafloxacin, compared with amoxycillin (79%, 26/33 versus 63%, 26/42, respectively; 95% CI = -5.2%, 38.1%). Microbiological eradication with grepafloxacin was statistically superior to amoxycillin in the evaluable population; the success rate was 89% (32/36) in the grepafloxacin group compared with 71% (32/45) for the amoxycillin group (95% CI = 2%, 37%). The pathogens most commonly isolated from patients were Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pneumoniae. The success rates for infections caused by S. pneumoniae and H. influenzae at follow-up were higher with grepafloxacin than with amoxycillin. Grepafloxacin was well tolerated, with a safety profile comparable to that of amoxycillin. The therapeutic judgement of patients and investigators at the patient's last visit, as well as the assessment of individual respiratory signs and symptoms, yielded comparable results with both treatments. The results of this study indicate that grepafloxacin, 600 mg od for 7-10 days, is equivalent to or better than amoxycillin, 500 mg tds for 7-10 days in achieving a successful clinical and microbiological response in the treatment of patients with CAP.
Adolescent↗
Genotypic versus phenotypic characterization, with respect to susceptibility and identification, of 17 clinical isolates of Staphylococcus lugdunensis.
OBJECTIVES: To compare different methods for the identification and determination of susceptibility to penicillin and methicillin of Staphylococcus lugdunensis. METHODS: Seventeen clinical isolates of S. lugdunensis (identified by PCR amplification and sequencing of the rpoB gene) were studied using the ATB32-Staph, Crystal, Vitek 2 and Wider commercial systems. The clumping factor test and the tube coagulase test were also performed. Beta-lactamase production was studied by chromogenic methods. Methicillin resistance was phenotypically studied by the MRSA slide latex agglutination test, growth in MRSA agar, and the Vitek 2 and Wider systems (based on oxacillin MIC), and genotypically studied by detection of the mecA gene by PCR. RESULTS: The clumping factor test was negative in 35.3% of strains. All isolates were correctly identified to species level by the ATB32-Staph system. Species misidentification rates were 5.9%, 23.5% and 29.4% with the Crystal, the Vitek 2 and the Wider systems, respectively, mostly as Staphylococcus haemolyticus. Beta-lactamase was present in 11.8% of strains. Whereas 76.5% and 47.1% of strains exhibited oxacillin resistance (MIC range 0.5-2 mg/L) by the Vitek 2 system and the Wider system, respectively, none of the strains was positive in the MRSA slide latex agglutination test or grew in MRSA agar. All strains lacked the mecA gene. CONCLUSIONS: The clumping factor test and some commercial systems may misidentify S. lugdunensis. Oxacillin resistance detected by commercial systems is not indicative of the presence of the mecA gene. These facts, together with beta-lactamase production, may preclude adequate treatment of infections by this virulent coagulase-negative Staphylococcus.
Cross Infection↗
Effect of various mixing ratios on antibacterial properties and hardness of endodontic sealers.
Most chemically cured two-component dental materials, including endodontic sealers, are marketed with mixing instructions but with no strict mixing ratios. The present study evaluated the antibacterial properties and hardness of three endodontic sealers: Roth's cement (RC), CRCS, and AH26, mixed to four controlled consistencies within the range of the manufacturer recommendations. Using Enterococcus faecalis as the test microorganism, antibacterial activity was evaluated by agar diffusion and direct contact test. Surface hardness of sealers with the same consistency was evaluated on week-old specimens by the Knoop Hardness Number tester. In the agar diffusion test, light consistency of RC showed larger zones of inhibition than heavier consistency, whereas no significant differences were found with AH26 or CRCS. In the direct contact test, RC and CRCS exhibited complete inhibition of bacterial growth at all consistencies, whereas AH26 with the heavier consistencies did not inhibit bacterial growth at 24 h samples. The hardness of AH26 and CRCS was significantly lower with lighter consistencies. It is concluded that endodontic sealers possess different antibacterial and physical properties according to their mixing consistencies.
Anti-Infective Agents, Local↗
Cryptococcus neoformans Ilv2p confers resistance to sulfometuron methyl and is required for survival at 37 degrees C and in vivo.
Acetolactate synthase catalyses the first common step in isoleucine and valine biosynthesis and is the target of several classes of inhibitors. The Cryptococcus neoformans ILV2 gene, encoding acetolactate synthase, was identified by complementation of a Saccharomyces cerevisiae ilv2 mutant. C. neoformans is highly resistant to the commercially available acetolactate synthase inhibitor, sulfometuron methyl (SM). Expression of C. neoformans ILV2 in S. cerevisiae conferred SM resistance, indicating that the SM resistance of C. neoformans is due, at least in part, to C. neoformans Ilv2p. The C. neoformans ILV2 gene was disrupted. The ilv2 mutants were auxotrophic for isoleucine and valine and the auxotrophy was satisfied by these amino acids only when proline, and not ammonium, was the nitrogen source, indicating nitrogen regulation of amino acid transport. ilv2 mutants rapidly lost viability at 37 degrees C and when starved for isoleucine and valine. Consistent with these phenotypes, an ilv2 mutant was avirulent and unable to survive in mice. Because C. neoformans Ilv2p is required for virulence and survival in vivo, inhibitors of branched-chain amino acid biosynthesis may make valuable antifungal agents.
Acetolactate Synthase↗
Molecular cloning and characterization of a genetic region from Serratia marcescens involved in DNA repair.
We report here the molecular isolation of a DNA fragment which encodes Tag-like activity from the Gram-negative bacterium Serratia marcescens. A recombinant plasmid encoding Tag-like activity was isolated from a S. marcescens plasmid gene library by complementation of an Escherichia coli tag mutant, which is deficient in 3-methyladenine DNA glycosylase I. The clone complements E. coli tag, recA, alkA, but not alkB, mutants for resistance to the DNA-damaging agent methyl methanesulphonate (MMS). The coding region of the Tag activity, initially isolated on a 6.5kb BamHI fragment, was defined to a 1.8kb BglII-SmaI fragment. Labelling of plasmid-encoded proteins using maxicells revealed that the 1.8kb fragment encodes two proteins of molecular weights 42,000 and 16,000. Data presented here suggest that the cloned fragment encodes a DNA repair protein(s) that has similar activity to the 3-methyladenine DNA glycosylase I of E. coli.
Cloning, Molecular↗
Key genes involved in heavy-metal resistance in Pseudomonas putida CD2.
A cadmium-resistant bacterium Pseudomonas putida CD2 was isolated from sewage sludge samples. Strain CD2 exhibited high maximal tolerant concentrations (MTC) for a large spectrum of divalent metals. Screening a library obtained using Tn5-B21 insertion mutagenesis resulted in identification of 12 mutants with a substantial decrease in resistance to 3 mM cadmium. The DNA sequences of the contiguous region from the Tn5 insertion sites were determined by inverse PCR. Six genes involved in cadmium resistance were identified. These genes were from three gene clusters: czcCBA1, cadA2R and colRS. The homologs of the first two gene clusters were predicted to be metal efflux systems, whereas the products of colRS, ColR and ColS, were thought to be a two-component signal transduction (TCST) system. In this study, we have demonstrated that ColRS also function in regulating multi-metal resistance using genetic complementation.
Anti-Bacterial Agents↗
Berberine sulfate blocks adherence of Streptococcus pyogenes to epithelial cells, fibronectin, and hexadecane.
Berberine sulfate is an alkaloid extracted from the roots and bark of various plants and possesses antibacterial, antifungal, and antiprotozoal activities. Most studies have focused on the bacteriostatic or bactericidal activities of this compound. In this study, we report that berberine sulfate is bacteriostatic for streptococci and that sub-MICs of berberine blocked the adherence of streptococci to host cells, immobilized fibronectin, and hexadecane. Concentrations of berberine below its MIC caused an eightfold increase in release of lipoteichoic acid from the streptococci. Higher concentrations of berberine directly interfered with the adherence of streptococci to host cells either by preventing the complexing of lipoteichoic acid with fibronectin or by dissolution of such complexes once they were formed. Thus, berberine sulfate interferes with the adherence of group A streptococci by two distinct mechanisms: one by releasing the adhesin lipoteichoic acid from the streptococcal cell surface and another by directly preventing or dissolving lipoteichoic acid-fibronectin complexes.
Alkanes↗
Contributions of individual mechanisms to fluoroquinolone resistance in 36 Escherichia coli strains isolated from humans and animals.
Twenty-eight human isolates of Escherichia coli from Argentina and Spain and eight veterinary isolates received from the Ministry of Agriculture Fisheries and Foods in the United Kingdom required 2 to > 128 micrograms of ciprofloxacin per ml for inhibition. Fragments of gyrA and parC encompassing the quinolone resistance-determining region were amplified by PCR, and the DNA sequences of the fragments were determined. All isolates contained a mutation in gyrA of a serine at position 83 (Ser83) to an Leu, and 26 isolates also contained a mutation of Asp87 to one of four amino acids: Asn (n = 14), Tyr (n = 6), Gly (n = 5), or His (n = 1). Twenty-four isolates contained a single mutation in parC, either a Ser80 to Ile (n = 17) or Arg (n = 2) or a Glu84 to Lys (n = 3). The role of a mutation in gyrB was investigated by introducing wild-type gyrB (pBP548) into all isolates; for three transformants MICs of ciprofloxacin were reduced; however, sequencing of PCR-derived fragments containing the gyrB quinolone resistance-determining region revealed no changes. The analogous region of parE was analyzed in 34 of 36 isolates by single-strand conformational polymorphism analysis and sequencing; however, no amino acid substitutions were discovered. The outer membrane protein and lipopolysaccharide profiles of all isolates were compared with those of reference strains, and the concentration of ciprofloxacin accumulated (with or without 100 microM carbony cyanide m-chlorophenylhydrazone [CCCP] was determined. Twenty-two isolates accumulated significantly lower concentrations of ciprofloxacin than the wild-type E. coli isolate; nine isolates accumulated less then half the concentration. The addition of CCCP increased the concentration of ciprofloxacin accumulated, and in all but one isolate the percent increase was greater than that in the control strains. The data indicate that high-level fluoroquinolone resistance in E. coli involves the acquisition of mutations at multiple loci.
Animals↗
Role of the multidrug efflux system MexXY in the emergence of moderate resistance to aminoglycosides among Pseudomonas aeruginosa isolates from patients with cystic fibrosis.
This study investigates the role of active efflux system MexXY in the emergence of aminoglycoside (AG) resistance among cystic fibrosis (CF) isolates of Pseudomonas aeruginosa. Three genotypically related susceptible and resistant (S/R) bacterial pairs and three other AG-resistant CF strains were compared to four non-CF strains moderately resistant to AGs. As demonstrated by immunoblot experiments, pump MexY was strongly overproduced in all of the resistant bacteria. This MexXY upregulation was associated with a 2- to 16-fold increase in the MICs of AGs in the S/R pairs and lower intracellular accumulation of dihydrostreptomycin. Alterations in mexZ, the repressor gene of operon mexXY, were found in all of the AG-resistant CF isolates and in one non-CF strain. Complementation of these bacteria with a plasmid-borne mexZ gene dramatically reduced the MICs of AGs, thus highlighting the role played by MexXY in the development of moderate resistance in CF patients. In contrast, complementation of the three non-CF strains showing wild-type mexZ genes left residual levels of resistance to AGs. These data indicate that a locus different from mexZ may be involved in overproduction of MexXY and that other nonenzymatic mechanisms contribute to AG resistance in P. aeruginosa.
Aminoglycosides↗