Effect of oxazolidinone, RBx 7644 (ranbezolid), on inhibition of staphylococcal adherence to plastic surfaces.

Adhesion to biomaterial is assumed to be a crucial step in the pathogenesis of foreign body infection. Slime producing Staphylococcus epidermidis and Staphylococcus aureus have emerged as a preeminent cause of nosocomial bacteremia and infections of prosthetic medical devices. We evaluated the time-dependent anti-adhesive effect of RBx 7644 (ranbezolid), vancomycin, linezolid and quinupristin/ dalfopristin on two isolates each of S. epidermidis and S. aureus. Linezolid and quinupristin/ dalfopristin showed inhibition only at supra-inhibitory concentrations (2 and 4X MIC) following 2 and 4 h delayed treatment, whereas RBx 7644 demonstrated significant activity against adhesion of staphylococcal cells that had been treated with 2 to 6 h delay. When vancomycin treatment was delayed by 4 to 6 h, even concentrations above the MIC were unable to prevent adherence. This study indicates that RBx 7644 has anti-adhesion potential and may emerge as an important antibiotic for prevention and treatment of device-related infections caused by staphylococci.

Antifungal susceptibility testing method for resource constrained laboratories.

PURPOSE: In resource-constrained laboratories of developing countries determination of antifungal susceptibility testing by NCCLS/CLSI method is not always feasible. We describe herein a simple yet comparable method for antifungal susceptibility testing. METHODS: Reference MICs of 72 fungal isolates including two quality control strains were determined by NCCLS/CLSI methods against fluconazole, itraconazole, voriconazole, amphotericin B and cancidas. Dermatophytes were also tested against terbinafine. Subsequently, on selection of optimum conditions, MIC was determined for all the fungal isolates by semisolid antifungal agar susceptibility method in Brain heart infusion broth supplemented with 0.5% agar (BHIA) without oil overlay and results were compared with those obtained by reference NCCLS/CLSI methods. RESULTS: Comparable results were obtained by NCCLS/CLSI and semisolid agar susceptibility (SAAS) methods against quality control strains. MICs for 72 isolates did not differ by more than one dilution for all drugs by SAAS. CONCLUSIONS: SAAS using BHIA without oil overlay provides a simple and reproducible method for obtaining MICs against yeast, filamentous fungi and dermatophytes in resource-constrained laboratories.

Detection of biofilm formation among the clinical isolates of Staphylococci: an evaluation of three different screening methods.

PURPOSE: The purpose of this study was to evaluate three methods for detection of biofilm formation in staphylococci. METHODS: For detection of biofilm formation, 152 clinical isolates of Staphylococcus spp. were screened by tissue culture plate (TCP), Tube method (TM) and Congo red agar (CRA) method. RESULTS: Of the 152 Staphylococcus spp. 88(57.8%) displayed a biofilm-positive phenotype under the optimized conditions in the TCP method and strains were further classified as high 22 (14.47 %) and moderate 60 (39.4 %) while in 70 (46.0 %) isolates weak or no biofilm was detected. Though TM correlated well with the TCP test for 18 (11.8 %) strongly biofilm producing strains, weak producers were difficult to discriminate from biofilm negative isolates. Screening on CRA does not correlate well with either of the two methods for detecting biofilm formation in staphylococci. CONCLUSION: The TCP method was found to be most sensitive, accurate and reproducible screening method for detection of biofilm formation by staphylococci and has the advantage of being a quantitative model to study the adherence of staphylococci on biomedical devices.

Activity of blue green microalgae extracts against in vitro generated Staphylococcus aureus with reduced susceptibility to vancomycin.

Blue green microalgae have been identified as one of the promising groups of organism from which biochemically active natural products have been isolated. Aqueous and organic extracts of nine blue green microalgae strains were screened against in vitro generated vancomycin intermediate resistant Staphylococcus aureus (VISA) strains. Aqueous extracts of all the blue green microalgae cultures were found to be inactive, while all the organic (hexane, chloroform and methanolic) extracts of Anabaena virabilis and Anabaena sp. showed activity against VISA strains with MIC of 32-64 mug/ml.

Detection of vancomycin resistant Staphylococcus aureus: a comparative study of three different phenotypic screening methods.

The objective of this study was to investigate screening methodologies, to detect Staphylococcus aureus strains with decreased susceptibility to vancomycin. Three methods were used to screen 160 Staphylococcus aureus clinical isolates along with ATCC quality control strains. Subsequently, MIC of all these 160 strains were determined by NCCLS methodology. The MIC of all the 160 clinical isolates was < or = 4 microg/mL and were classified as vancomycin susceptible by NCCLS criteria but 23 strains were positive by Hiramatshu method, two grew on MHA (5 microg/mL vancomycin) while CDC method correctly identified no vancomycin intermediate S.aureus (VISA) or vancomycin resistant S.aureus (VRSA) strains with reference to there MIC. CDC method was found to be the most appropriate screening methodology for detection of VISA or VRSA for diagnostic laboratories.

Evaluation of methods for AmpC beta-lactamase in gram negative clinical isolates from tertiary care hospitals.

The purpose of this study was to simultaneously screen for Extended-spectrum beta-lactamases (ESBL) and AmpC beta-lactamases in gram negative clinical isolates from four tertiary care hospitals and further to compare two detection methods three-dimensional extraction method and AmpC disk test for AmpC beta-lactamases. A total of 272 isolates were screened for ESBL and AmpC beta-lactamase by modified double disk approximation method (MDDM). Synergy observed between disks of ceftazidime/cefotaxime and clavulanate were considered as ESBL producer. Isolates showing reduced susceptibility to either of the test drugs (ceftazidime or cefotaxime) and cefoxitin were considered as presumptive AmpC producers and further confirmed by three-dimensional extraction method and AmpC disk test. A total of 173 (64%) of the isolates were found to be ESBL positive and 61 (23%) showed resistant to cefoxitin. ESBL was detected in 80 (62%) isolates of E. coli and 71 (73%) of Klebsiella spp. The occurrence of AmpC beta-lactamases was found to be 8% (22) of the total isolates and the two detection methods for AmpC beta-lactamase showed concordant results. Screening for ESBL and AmpC can be simultaneously done by MDDM method and confirmation for AmpC beta-lactamase should be carried out routinely in tertiary care hospitals by AmpC disk test, as it is a simple and rapid procedure.

Scatter and veiling glare estimation based on sampled primary intensity.

Scatter and veiling glare are predominant sources of error in videodensitometric iodine quantification. Standard beam stop techniques such as lead strips or an array of lead discs, placed before the patients, have previously been used to measure scatter and veiling glare in digital radiographic images. However, these techniques significantly increase patient x-ray exposure. In order to overcome this limitation, a scatter measurement technique based on sampled primary intensity has been investigated. This technique uses an array of apertures in a lead sheet to sample the primary x-ray intensity. The scatter-glare intensity in these locations is calculated by subtracting the sampled primary intensity from an open field image which contains both primary and scatter-glare. The calculated scatter-glare values can be interpolated or combined with digital filtration to estimate the scatter-glare intensity on a pixel by pixel basis. The technique was evaluated using a Lucite step phantom and an anthropomorphic chest phantom. The average rms percentage errors of scatter and veiling glare estimation using bi-cubic interpolation and digital filtration techniques were 8.02% and 7.53%, respectively. The average rms percentage errors of primary intensity estimation using bi-cubic interpolation and digital filtration techniques were 10.01% and 8.91%, respectively. The x-ray exposure-area product (EAP) from the aperture array was only 4.38% of the EAP from the open field. These results indicate that the scatter-glare intensity can be accurately estimated with minimal x-ray exposure using sampled primary intensity.

Unique lipoproteins secreted by primary astrocytes from wild type, apoE (-/-), and human apoE transgenic mice.

Composition of central nervous system lipoproteins affects the metabolism of lipoprotein constituents within the brain. The epsilon4 allele of apolipoprotein E (apoE) is a risk factor for Alzheimer's disease via an unknown mechanism(s). As glia are the primary central nervous system cell type that synthesize apoE, we characterized lipoproteins secreted by astrocytes from wild type (WT), apoE (-/-), and apoE transgenic mice expressing human apoE3 or apoE4 in a mouse apoE (-/-) background. Nondenaturing size exclusion chromatography demonstrates that WT, apoE3, and apoE4 astrocytes secrete particles the size of plasma high density lipoprotein (HDL) composed of phospholipid, free cholesterol, and protein, primarily apoE and apoJ. However, the lipid:apoE ratio of particles containing human apoE is significantly lower than WT. ApoE localizes across HDL-like particle sizes. ApoJ localizes to the smallest HDL-like particles. ApoE (-/-) astrocytes secrete little phospholipid or free cholesterol despite comparable apoJ expression, suggesting that apoE is required for normal secretion of astrocyte lipoproteins. Further, particles were not detected in apoE (-/-) samples by electron microscopy. Nondenaturing immunoprecipitation experiments indicate that apoE and apoJ reside predominantly on distinct particles. These studies suggest that apoE expression influences the unique structure of astrocyte lipoproteins, a process further modified by apoE species.

Absolute volumetric coronary blood flow measurement with digital subtraction angiography.

The problems associated with visual interpretation of coronary arteriograms have been well-documented. There is a need for more physiologic means of assessing coronary artery stenosis during routine coronary arteriography. Volumetric coronary blood flow assessed as a function of time can be a valuable aid in the analysis of functional significance of arterial obstruction. A volumetric coronary blood flow measurement technique was investigated in a swine animal model using phase matched temporal subtraction images. The left anterior descending (LAD) coronary artery of swine animal models were instrumented with an ultrasound flow probe (US) and a vascular occluder producing stenosis. Contrast material injections (2-4 ml/sec for 3 sec) were made into the left coronary ostium during image acquisition. Phase-matched temporal subtraction (DSA) images were used to measure volumetric coronary blood flow in the LAD. In addition, a technique for automatic estimation of iodine calibration slope was also investigated. In 49 independent comparisons, the mean coronary blood flow (FPA) correlated extremely well with the mean US flow (FPA = 0.92US + 1.42 ml/min, r = 0.99, standard error of estimate (SEE) = 4.32 ml/min). Further more, the automatic iodine calibration technique was shown to be very accurate. In conclusion, accurate volumetric coronary blood flow measurements can be made before the onset of significant changes in coronary blood flow due to contrast injection.

Study of sperm antibodies in the sera of vasectomized males.

PIP: Agglutination and immobilization tests were performed to detect the presence of sperm antibodies in the sera of 100 vasectomized men. Overall, 52% of subjects had sperm antibodies. 50% showed agglutinating antibodies, while immobilizing antibodies were present in 40%. Of the 52 positive cases, 23 showed agglutinating antibody alone in their sera. 73 had both agglutinating and immobilizing antibodies, and 3.8% had sperm immobilizing activity alone. The age incidence of the presence of sperm antibodies was as follows: under 35 years, 66%; 36-40 years, 50%; 41-45 years, 50%; and 46 years and above, 33.3%. The highest percentage of presence of sperm antibodies was recorded in men who had been vasectomized less than 1 year previously (75%). Significantly high titers of sperm agglutinating activity were found in 20% of the positive cases, while high titers of sperm immobilizing activity were noted in 40% of positive cases. It has been suggested that the development of sperm antibodies after vasectomy may prevent subsequent successful restoration of fertility by reanastomosis.^ieng