Abstract: The activities of ampicillin, ampicillin-sulbactam, amoxicillin, amoxicillin-clavulanic acid, ticarcillin, ticarcillin-clavulanic acid, piperacillin, piperacillin-tazobactam, aztreonam, and aztreonam-clavulanic against Stenotrophomonas maltophilia strains for which the MICs of penicillins and commercially available beta-lactam-beta-lactamase inhibitor combinations were higher than the breakpoints usually recommended for Pseudomonas aeruginosa in commercially available broth microdilution methods were tested by the agar diffusion, agar dilution, and broth microdilution methods. Time-kill curve studies were performed when discrepancies between these methods were observed. The MICs obtained by the commercially available broth microdilution method, the agar dilution method, and the broth microdilution method were almost identical. Twenty-five percent of the strains tested showed inhibition diameters of > or =15 mm for ticarcillin-clavulanic acid, and 43.7% of the strains tested showed inhibition diameters of > or =18 mm for piperacillin-tazobactam by the agar diffusion method. The time-kill curves for these strains confirmed the results obtained by dilution methods. Aztreonam-clavulanic acid (2:1) at concentrations of 32-fold the MIC). With 50 times the standard inoculum, MBCs were at least 32-fold the MICs for all the strains tested.

Abstract: Resistance to antimicrobial agents is a major determinant of the efficacy of regimens to eradicate Helicobacter pylori. Clarithromycin (CLA) has become one of the most commonly used antibiotics for treatment of H pylori infection. In this study, the rate of primary resistance to CLA in H pylori isolated from patients was determined. One hundred sixty-two strains were recovered from patients before treatment. Strains were grown and inoculated onto Mueller-Hinton agar with 7% sheep blood. CLA epsilometer gradient agar diffusion test (E test) strips were used to test for susceptibility. Appropriate control organisms were tested to validate the assay. Plates were incubated at 37 degrees C in a microaerophilic atmosphere for up to five days. E test results were easy to interpret. Strains were considered resistant if the minimum inhibitory concentration (MIC) was 2 micrograms/mL or greater. Three strains were resistant (two strains with MIC 8 micrograms/mL and one strain with MIC 12 micrograms/mL) and 159 strains were sensitive (MICs ranged from less than 0.016 to 0.38 micrograms/mL). Ninety per cent of the strains had MICs of 0.023 micrograms/mL. Primary resistance was 1.8%. These susceptibility data support the use of CLA for the treatment of H pylori in the Nova Scotia population.

Abstract: A microbial method for the simultaneous detection of residues of β-lactams, sulfonamides, streptomycin and tetracyclines in meat is reported. The method, termed CPMA (Combined Plates Microbial Assay), is based on the detection of inhibitors in a sample by the agar diffusion test performed on two agar plates seeded with the same test microorganism, protected and not from the inhibitor activity of some drugs, by i) the inclusion of substance (penicillinase, para-aminobenzoic acid or cysteine) to selectively reverse the inhibitory activity of a class of antibiotics (sulfonamides or β-lactams) or of a specific molecule (streptomycin); or ii) by using the corresponding strain resistant to a class of antibiotics (tetracyclines). The presence of an inhibition zone on both plates proves the presence of an inhibitor in the sample while the disappearance of the inhibition or its reduction in one of the two plates permits the presumptive identification of the inhibitor. The CPMA draws advantage from the EEC four plate method to improve detection levels and the identification of some inhibitors.

Abstract: An evaluation to determine the optimal methods for the in vitro susceptibility testing of 41 clinical isolates and the ATCC 49619 strain ofStreptococcus pneumoniae to penicillin was undertaken. No very major or major interpretive errors were observed with the following test methods and media: agar dilution using either Mueller-Hinton medium with lysed horse blood or Haemophilus test medium; broth dilution using cation-adjusted Mueller-Hinton medium with lysed horse blood, Haemophilus test medium, or Todd-Hewitt medium; and the epsilometer test (E-test) using agar containing Mueller-Hinton medium and 5% sheep blood. The disk diffusion method using agar containing Mueller-Hinton medium and 5% sheep blood agar was an effective screening method, requiring confirmation by a dilution susceptibility test method.

Abstract: The stereoisomers of amidinomycin 7 and their intermediates 1-6, which are produced from homochiral 3-oxocyclopentanecarboxylic acids by asymmetric synthesis, are tested for their antimicrobial effects by agar diffusion test and by Bouillon serial dilution assay. Their antibiotic activities against Bacillus subtilis, Staphylococcus aureus, and Micrococcus Iuteus, respectively, are reported. Structure-activity relationships depend on the type and combination of functional groups, on only the relative stereochemistry as well as on the grade of lipophilia of the tested compounds.

Abstract: From aerial parts of Stevia triflora DC the flavonol glycoside ombuoside (7,4'-di-O-methylquercetin-3-O-beta-rutinoside) has been isolated and identified on the basis of spectral data. Ombuoside and the synthetic derivatives octa-acetylombuoside, ombuine and retusine were tested for antimicrobial activity against several strains of Gram-positive and Gram-negative bacteria and the yeast Candida albicans, using the agar diffusion method. The flavonol glycoside ombuoside and the respective aglycone ombuine, both exhibited moderated activity against Corynebacterium diphtheria, Staphylococcus aureus, Escherichia coli and Candida albicans. To a lesser degree, octaacetylombuoside and retusine showed activity against the Gram-positive bacteria C. diphtheria and S. aureus, but proved to be inactive against Gram-negative bacteria and Candida albicans. These results indicate that the presence of free hydroxyl groups, either alcoholic or phenolic, is an important chemical feature for the expression of flavonol antimicrobial activity. It is worth noting that this is the first study reported on the antibacterial and antifungal activity of these substances.