Smoked drug use in patients with TB is associated with higher bacterial burden.

BACKGROUND: Smoking of illicit drugs may lead to more rapid TB disease progression or late treatment presentation, yet research on this topic is scant. We examined the association between smoked drug use and bacterial burden among patients newly initiated on drug-susceptible TB (DS-TB) therapy.METHODS: Data from 303 participants initiating DS-TB treatment in the Western Cape Province, South Africa, were analyzed. Smoked drug use was defined as self-reported or biologically verified methamphetamine, methaqualone and/or cannabis use. Proportional hazard and logistic regression models (adjusted for age, sex, HIV status and tobacco use) examined associations between smoked drug use and mycobacterial time to culture positivity (TTP), acid-fast bacilli sputum smear positivity and lung cavitation.RESULTS: People who smoked drugs (PWSD) comprised 54.8% (n = 166) of the cohort. TTP was faster for PWSD (hazard ratio 1.48, 95% CI 1.10-1.97; P = 0.008). Smear positivity was higher among PWSD (OR 2.28, 95% CI 1.22-4.34; P = 0.011). Smoked drug use (OR 1.08, 95% CI 0.62-1.87; P = 0.799) was not associated with increased cavitation.CONCLUSIONS: PWSD had a higher bacterial burden at diagnosis than those who do not smoke drugs. Screening for TB among PWSD in the community may facilitate earlier linkage to TB treatment and reduce community transmission.

Estimation of π-π Electronic Couplings from Current Measurements.

The π-π interactions between organic molecules are among the most important parameters for optimizing the transport and optical properties of organic transistors, light-emitting diodes, and (bio-) molecular devices. Despite substantial theoretical progress, direct experimental measurement of the π-π electronic coupling energy parameter t has remained an old challenge due to molecular structural variability and the large number of parameters that affect the charge transport. Here, we propose a study of π-π interactions from electrochemical and current measurements on a large array of ferrocene-thiolated gold nanocrystals. We confirm the theoretical prediction that t can be assessed from a statistical analysis of current histograms. The extracted value of t ≈35 meV is in the expected range based on our density functional theory analysis. Furthermore, the t distribution is not necessarily Gaussian and could be used as an ultrasensitive technique to assess intermolecular distance fluctuation at the subangström level. The present work establishes a direct bridge between quantum chemistry, electrochemistry, organic electronics, and mesoscopic physics, all of which were used to discuss results and perspectives in a quantitative manner.

A 17 GHz molecular rectifier.

Molecular electronics originally proposed that small molecules sandwiched between electrodes would accomplish electronic functions and enable ultimate scaling to be reached. However, so far, functional molecular devices have only been demonstrated at low frequency. Here, we demonstrate molecular diodes operating up to 17.8 GHz. Direct current and radio frequency (RF) properties were simultaneously measured on a large array of molecular junctions composed of gold nanocrystal electrodes, ferrocenyl undecanethiol molecules and the tip of an interferometric scanning microwave microscope. The present nanometre-scale molecular diodes offer a current density increase by several orders of magnitude compared with that of micrometre-scale molecular diodes, allowing RF operation. The measured S11 parameters show a diode rectification ratio of 12 dB which is linked to the rectification behaviour of the direct current conductance. From the RF measurements, we extrapolate a cut-off frequency of 520 GHz. A comparison with the silicon RF-Schottky diodes, architecture suggests that the RF-molecular diodes are extremely attractive for scaling and high-frequency operation.

An interferometric scanning microwave microscope and calibration method for sub-fF microwave measurements.

We report on an adjustable interferometric set-up for Scanning Microwave Microscopy. This interferometer is designed in order to combine simplicity, a relatively flexible choice of the frequency of interference used for measurements as well as the choice of impedances range where the interference occurs. A vectorial calibration method based on a modified 1-port error model is also proposed. Calibrated measurements of capacitors have been obtained around the test frequency of 3.5 GHz down to about 0.1 fF. Comparison with standard vector network analyzer measurements is shown to assess the performance of the proposed system.

Rise in rifampicin-monoresistant tuberculosis in Western Cape, South Africa.

SETTING: Brewelskloof Hospital, Western Cape, South Africa. OBJECTIVES: To verify the perceived increase in rifampicin monoresistant tuberculosis (RMR-TB) in the Cape Winelands-Overberg region and to identify potential risk factors. DESIGN: A retrospective descriptive study of trends in RMR-TB over a 5-year period (2004-2008), followed by a case-control study of RMR and isoniazid (INH) monoresistant TB cases, diagnosed from April 2007 to March 2009, to assess for risk factors. RESULTS: The total number of RMR-TB cases more than tripled, from 31 in 2004 to 98 in 2008. The calculated doubling time was 1.63 years (95%CI 1.18-2.66). For the assessment of risk factors, 95 RMR-TB cases were objectively verified on genotypic and phenotypic analysis. Of 108 specimens genotypically identified as RMR cases, 13 (12%) were misidentified, multidrug-resistant TB. On multivariate analysis, previous use of antiretroviral therapy (OR 6.4, 95%CI 1.3-31.8), alcohol use (OR 4.8, 95%CI 2.0-11.3) and age ≥ 40 years (OR 5.8, 95%CI 2.4-13.6) were significantly associated with RMR-TB. CONCLUSION: RMR-TB is rapidly increasing in the study setting, particularly among patients with advanced human immunodeficiency virus (HIV) disease. Routine drug susceptibility testing should be considered in all TB-HIV co-infected patients, and absence of INH resistance should be confirmed phenotypically if genotypic RMR-TB is detected.

Note: Quantitative (artifact-free) surface potential measurements using Kelvin force microscopy.

The measurement of local surface potentials by Kelvin force microscopy (KFM) can be sensitive to external perturbations which lead to artifacts such as strong dependences of experimental results (typically in a ∼1 V range) with KFM internal parameters (cantilever excitation frequency and/or the projection phase of the KFM feedback-loop). We analyze and demonstrate a correction of such effects on a KFM implementation in ambient air. Artifact-free KFM measurements, i.e., truly quantitative surface potential measurements, are obtained with a ∼30 mV accuracy.

Drug-resistant tuberculosis epidemic in the Western Cape driven by a virulent Beijing genotype strain.

Temporal analysis of drug-resistant tuberculosis (TB) cases in the Western Cape, South Africa, showed a 1.5-fold increase over a 2-year period, suggesting a doubling time of 8.2 years. This increase was strongly associated with multidrug resistance and the Beijing genotype. Forty-two per cent of the overall increase was due to the Beijing genotype strain R220, suggesting that this strain had evolved unique properties that allowed for both acquisition and transmission of drug resistance. To curb the drug-resistant TB epidemic in this setting, it will be essential to implement rapid diagnostics and efficient infection control measures, improve contact screening and ensure treatment adherence.

Influence of Sutherlandia frutescens extracts on cell numbers, morphology and gene expression in MCF-7 cells.

Sutherlandia frutescens is a well-known South African herbal remedy traditionally used for stomach problems, internal cancers, diabetes, various inflammatory conditions and recently to improve the overall health in cancer and HIV/AIDS patients. The influence of crude Sutherlandia frutescens extracts (prepared with 70% ethanol) was investigated on cell numbers, morphology, and gene expression profiles in a MCF-7 human breast adenocarcinoma cell line. Time-dependent (24, 34, 48 and 72 h) and dose-dependent (0.5-2.5 mg/ml) studies were conducted utilizing spectrophotometrical analysis with crystal violet as DNA stain. A statistically significant decrease to 50% of malignant cell numbers was observed after 24 h of exposure to 1.5 mg/ml Sutherlandia frutescens extract when compared to vehicle-treated controls. Morphological characteristics of apoptosis including cytoplasmic shrinking, membrane blebbing and apoptotic bodies were observed after 24h of exposure. A preliminary global gene expression profile was obtained by means of microarray analysis and revealed valuable information about the molecular mechanisms and signal transduction associated with 70% ethanolic Sutherlandia frutescens extracts.

The importance of cholesterol in maintenance of P-glycoprotein activity and its membrane perturbing influence.

In tumour cell lines that display multidrug resistance, expression of P-glycoprotein (P-gp) alters many aspects of biomembrane organization in addition to its well-characterized drug transport activity. We have developed a reconstitution system to directly investigate the effect of purified P-gp on the biophysical properties of lipid bilayers. Using a mixed detergent system it was possible to efficiently reconstitute P-gp at lipid:protein ratios as low as 2.5 (w/w) by removal of detergent using adsorption to SM-2 BioBeads. P-gp was able to alter many biophysical parameters associated with lipid organization within bilayers. For example, the changes in overall fluidity and excimer formation by lipid analogues indicate modified packing organization of bilayer constituents. Surprisingly, given its role in conferring drug resistance, P-gp insertion into bilayers also caused significantly increased permeability to aqueous compounds, also reflecting a modified phospholipid environment. Translocation of various phospholipid species between leaflets of the bilayer was increased in the presence of P-gp; however, the effect was not dependent on ATP hydrolysis by the protein. Physiological concentrations of cholesterol modified P-gp function and the degree to which it perturbed bilayer organization. The basal ATPase activity of P-gp was increased in a dose-dependent fashion by the incorporation of cholesterol in PC:PE liposomes. In addition, the degree to which the modulator verapamil was able to stimulate this basal ATPase activity was reduced by the presence of cholesterol in proteoliposomes. However, the potency of verapamil was unaltered, suggesting a specific effect, not simply caused by lower drug penetration into the cholesterol containing bilayers. In summary, P-gp is able to cause perturbation in the organization of bilayer constituents. Cholesterol imparted "stability" to this perturbation of bilayer organization by P-gp and moreover this led to altered protein function.

Invasive disease due to extended spectrum beta-lactamase-producing Klebsiella pneumoniae in a neonatal unit: the possible role of cockroaches.

We recently experienced an outbreak of nosocomial disease due to extended spectrum beta-lactamase-producing Klebsiella pneumoniae in a neonatal unit infested with cockroaches. Organisms isolated from cockroaches were indistinguishable by pulsed-field gel electrophoresis from those colonizing infants or causing clinical disease using. Cockroach elimination together with standard infection-control measures resulted in control of the outbreak. We suggest cockroaches are possible vectors of pathogenic bacteria in the hospital environment.

Effect of Temperature and Media on Adenosine Triphosphate Cell Content in Enterobacter aerogenes.

During cold storage (2°C) of Enterobacter aerogenes for 15 min, 2, 4, 6 and 8 d in glucose mineral salts medium (GMS) and skim milk (SM), substantial differences were noticed in ATP/cell levels. At the appropriate interval, ATP was determined with the firefly bioluminescent method on a portion of the culture, while another portion was activated at 30°C for 40 min and ATP determined at 10-min intervals. Initial ATP content after 15 min of storage in SM was 0.55 femtogram (fg)/cell as compared to 0.84 fg/cell in GMS. Upon cold storage for longer periods (2, 4, 6 and 8 d), the ATP/cell concentrations were relatively stable (0.82, 0.73,0.62 and 0.72 fg) in GMS, while they declined to levels below 0.2 fg in SM. However, activation of only 30 min increased cell ATP concentration in SM to 1.06, 0.92, 0.77, 0.66 and 0.72 fg, and narrowed the difference between ATP/cell levels in the two media. As a realistic ATP concentration/cell value is necessary to calculate bacterial numbers in milk by the bioluminescent technique, a 30-min activation period at 30°C is recommended to replenish the A TP lost during refrigerated storage.

Effect of Water Activity and Temperature on Staphylococcus aureus Growth and Thermonuclease Production in Smoked Snoek.

Smoked snoek at different water activity (aw) values (0.966, 0.956 and 0.944) were inoculated with Staphylococcus aureus at a concentration of approximately log 4.7 colony forming units per gram (CFU/g) and incubated at different temperatures (4, 12, 24 and 37 C) for various periods. Samples of inoculated and control snoek were taken at different intervals to determine the microbial populations ( S. aureus , total organisms and enterococci), pH and presence of thermonuclease. No growth of S. aureus nor thermonuclease production occurred at 4 C. At 12 C, notwithstanding high S. aureus log counts of 6.75/g, 9.74/g and 9.69/g in the inoculated 0.966, 0.956 and 0.944 aw samples, respectively, thermonuclease was absent after 21 days of incubation. At 24 and 37 C at all three aw levels, very high S. aureus counts were recorded and were accompanied by thermonuclease production before the end of the relative incubation periods (5 and 3 days, respectively). A reduction of the aw of the snoek resulted in a slightly slower S. aureus growth rate at 37 C and also delayed thermonuclease production at 24 and 37 C. The thermonuclease test was an effective means of detecting S. aureus growth except in samples incubated at 12 C. Enterococcus numbers increased in all control samples during storage, but none were found to produce thermonuclease.

Staphylococcal food poisoning from infected snoek.

Snoek was implicated in the food poisoning of 2 people in Bloemfontein. The patients' symptoms and culture of snoek samples suggested Staphylococcus aureus as the causative agent. Enumeration of S. aureus by selective procedures gave counts of 200 000 per gram in snoek obtained from the patients and from the butchery supplying the snoek. Investigations indicated that the snoek was heavily contaminated with S. aureus before arrival at the butchery and that the organisms grew as a result of mishandling after processing.