Epidemic levels of drug resistant tuberculosis (MDR and XDR-TB) in a high HIV prevalence setting in Khayelitsha, South Africa

Background

Although multidrug-resistant tuberculosis (MDR-TB) is emerging as a significant threat to tuberculosis control in high HIV prevalence countries such as South Africa, limited data is available on the burden of drug resistant tuberculosis and any association with HIV in such settings. We conducted a community-based representative survey to assess the MDR-TB burden in Khayelitsha, an urban township in South Africa with high HIV and TB prevalence.

Methodology/Principal Findings

A cross-sectional survey was conducted among adult clinic attendees suspected for pulmonary tuberculosis in two large primary care clinics, together constituting 50% of the tuberculosis burden in Khayelitsha. Drug susceptibility testing (DST) for isoniazid and rifampicin was conducted using a line probe assay on positive sputum cultures, and with culture-based DST for first and second-line drugs. Between May and November 2008, culture positive pulmonary tuberculosis was diagnosed in 271 new and 264 previously treated tuberculosis suspects (sample enriched with previously treated cases). Among those with known HIV status, 55% and 71% were HIV infected respectively. MDR-TB was diagnosed in 3.3% and 7.7% of new and previously treated cases. These figures equate to an estimated case notification rate for MDR-TB of 51/100,000/year, with new cases constituting 55% of the estimated MDR-TB burden. HIV infection was not significantly associated with rifampicin resistance in multivariate analyses.

Conclusions/Significance

There is an extremely high burden of MDR-TB in this setting, most likely representing ongoing transmission. These data highlight the need to diagnose drug resistance among all TB cases, and for innovative models of case detection and treatment for MDR-TB, in order to interrupt transmission and control this emerging epidemic.     

Overview of microbial biofilms

As the success of this two-issue special section of the Journal of Industrial Microbiology attests, the study of microbial biofilms is truly burgeoning as the uniqueness and the importance of this mode of growth is increasingly recognized. Because of its universality the biofilm concept impacts virtually all of the subdivisions of Microbiology (including Medical, Dental, Agricultural, Industrial and Environmental) and these two issues incorporate contributions from authors in all of these disciplines. Some time ago we reasoned that bacteria cannot possibly be aware (sic) of their precise location, in terms of this spectrum of anthrocentric subspecialties, and that their behavior must be dictated by a standard set of phenotypic responses to environmental conditions in what must seem to them (sic) to be a continuum of very similar aquatic ecosystems. In this overview I will, therefore, stress the common features of microbial biofilms that we should bear in mind as we use this simple universal concept to seek to understand bacterial behavior in literally hundreds of aquatic ecosystems traditionally studied by dozens of subspecies of microbiologists reared in sharply different scientific and academic conventions.     

Reversal of increased microvascular permeability associated with ischemia-reperfusion: role of cAMP.

Ischemia-reperfusion (IR) is a form of oxidant injury known to increase microvascular permeability in the lung. Agents that increase adenosine 3',5'-cyclic monophosphate (cAMP) levels have been shown to have beneficial effects in several models of oxidant lung injury associated with increased microvascular permeability. We investigated the role of adenylate cyclase activation with isoproterenol (ISO) or forskolin (FSK) in reversing the increased microvascular permeability associated with IR. ISO or FSK administered after 45 min of ischemia and 46 min of reperfusion caused a reduction in the capillary filtration coefficient (Kfc) from 1.25 +/- 0.13 to 0.53 +/- 0.08 and 0.55 +/- 0.10 ml.min-1.cmH2O-1.100 g tissue-1, respectively, at 90 min of reperfusion. This reduction in Kfc was accompanied by a rise in perfusate cAMP levels from 16.5 +/- 4.9 and 31.2 +/- 11.9 pmol/ml at 45 min of reperfusion to 444.2 +/- 147.8 and 276.1 +/- 91.0 pmol/ml at 105 min of reperfusion in lungs treated with ISO or FSK, respectively, at 46 min of reperfusion. Dibutyryl cAMP (DBcAMP), a membrane-permeable cAMP analogue, mimicked the permeability effect by reducing Kfc to 0.67 +/- 0.15 at 90 min of reperfusion. Significant hemodynamic changes occurred but were small and cannot explain the observed effect on Kfc. Photomicrographs from lungs treated with ISO or FSK revealed a reversal of the morphological manifestations of increased microvascular permeability. We conclude that the increased microvascular permeability associated with IR can be reversed by ISO, FSK, and DBcAMP and that cAMP produced by the lung contributes to the observed reversal.     

Disgust enhances the recollection of negative emotional images

Memory is typically better for emotional relative to neutral images, an effect generally considered to be mediated by arousal. However, this explanation cannot explain the full pattern of findings in the literature. Two experiments are reported that investigate the differential effects of categorical affective states upon emotional memory and the contributions of stimulus dimensions other than pleasantness and arousal to any memory advantage. In Experiment 1, disgusting images were better remembered than equally unpleasant frightening ones, despite the disgusting images being less arousing. In Experiment 2, regression analyses identified affective impact--a factor shown previously to influence the allocation of visual attention and amygdala response to negative emotional images--as the strongest predictor of remembering. These findings raise significant issues that the arousal account of emotional memory cannot readily address. The term impact refers to an undifferentiated emotional response to a stimulus, without requiring detailed consideration of specific dimensions of image content. We argue that ratings of impact relate to how the self is affected. The present data call for further consideration of the theoretical specifications of the mechanisms that lead to enhanced memory for emotional stimuli and their neural substrates.     

ADP-Ribosylation with Pertussis Toxin Modulates the GTP-Sensitive Opioid Ligand Binding in Digitonin-Soluble Extracts of Rat Brain Membranes

Pertussis toxin-catalyzed ADP-ribosylation of the guanine nucleotide-binding proteins Gi and Go is shown to proceed in Mg2+-digitonin extracts from rat brain; the Mr 41,000 and Mr 39,000 peptides are labelled there as in the membranes. The ADP-ribosylation in detergent solution retains the differential sensitivity to guanine nucleotide analogues. This reaction also removes the partial inhibition by the guanine nucleotides of the binding of opioid agonists, as does the same treatment in the membranes. The partial inhibition of agonist binding by Na+, however, is left unchanged. The binding of the antagonist naloxone is little affected by Na+ or by guanine nucleotides in the treated membranes, but the treated soluble receptors show an enhanced binding in high-Na+ medium, although still guanine nucleotide insensitive. The data suggest that the toxin reaction in the absence of guanine nucleotides and agonist stabilizes the opioid receptor in a receptor-G-protein coupled state which is no longer sensitive to guanine nucleotides but retains its sensitivity to the Na+ ions.     

Nonlinear ionizing radiation-induced changes in eye lens cell proliferation,cyclin D1 expression and lens shape

Elevated cataract risk after radiation exposure was established soon after the discovery of X-rays in 1895. Today, increased cataract incidence among medical imaging practitioners and after nuclear incidents has highlighted how little is still understood about the biological responses of the lens to low-dose ionizing radiation (IR). Here, we show for the first time that in mice, lens epithelial cells (LECs) in the peripheral region repair DNA double strand breaks (DSB) after exposure to 20 and 100 mGy more slowly compared with circulating blood lymphocytes, as demonstrated by counts of γH2AX foci in cell nuclei. LECs in the central region repaired DSBs faster than either LECs in the lens periphery or lymphocytes. Although DSB markers (γH2AX, 53BP1 and RAD51) in both lens regions showed linear dose responses at the 1 h timepoint, nonlinear responses were observed in lenses for EdU (5-ethynyl-2′-deoxy-uridine) incorporation, cyclin D1 staining and cell density after 24 h at 100 and 250 mGy. After 10 months, the lens aspect ratio was also altered, an indicator of the consequences of the altered cell proliferation and cell density changes. A best-fit model demonstrated a dose-response peak at 500 mGy. These data identify specific nonlinear biological responses to low (less than 1000 mGy) dose IR-induced DNA damage in the lens epithelium.     

Evaluation of platelet function by flow cytometry

Platelet function in whole blood can be comprehensively evaluated by flow cytometry. Flow cytometry can be used to measure platelet reactivity, circulating activated platelets, platelet-platelet aggregates, leukocyte-platelet aggregates, procoagulant platelet-derived microparticles, and calcium flux. Clinical applications of whole blood flow cytometric assays of platelet function in disease states (e.g., acute coronary syndromes, angioplasty, and stroke) may include identification of patients who would benefit from additional antiplatelet therapy and prediction of ischemic events. Circulating monocyte-platelet aggregates appear to be a more sensitive marker of in vivo platelet activation than circulating P-selectin-positive platelets. Flow cytometry can also be used in the following clinical settings: monitoring of GPIIb-IIIa antagonist therapy, diagnosis of inherited deficiencies of platelet surface glycoproteins, diagnosis of storage pool disease, diagnosis of heparin-induced thrombocytopenia, and measurement of the rate of thrombopoiesis.     

Basolateral K channels in an insect epithelium. Channel density, conductance, and block by barium

K channels in the basolateral membrane of insect hindgut were studied using current fluctuation analysis and microelectrodes. Locust recta were mounted in Ussing-type chambers containing Cl-free saline and cyclic AMP (cAMP). A transepithelial K current was induced by raising serosal [K] under short-circuit conditions. Adding Ba to the mucosal (luminal) side under these conditions had no effect; however, serosal Ba reversibly inhibited the short-circuit current (Isc), increased transepithelial resistance (Rt), and added a Lorentzian component to power density spectra of the Isc. A nonlinear relationship between corner frequency and serosal [Ba] was observed, which suggests that the rate constant for Ba association with basolateral channels increased as [Ba] was elevated. Microelectrode experiments revealed that the basolateral membrane hyperpolarized when Ba was added: this change in membrane potential could explain the nonlinearity of the 2 pi fc vs. [Ba] relationship if external Ba sensed about three-quarters of the basolateral membrane field. Conventional microelectrodes were used to determine the correspondence between transepithelially measured current noise and basolateral membrane conductance fluctuations, and ion-sensitive microelectrodes were used to measure intracellular K activity (acK). From the relationship between the net electrochemical potential for K across the basolateral membrane and the single channel current calculated from noise analysis, we estimate that the conductance of basolateral K channels is approximately 60 pS, and that there are approximately 180 million channels per square centimeter of tissue area.     

An aggregation-specific enzyme-linked immunosorbent assay: detection of conformational differences between recombinant PrP protein dimers and PrP(Sc) aggregates

The conversion of the normal cellular prion protein, PrP(C), into the protease-resistant, scrapie PrP(Sc) aggregate is the cause of prion diseases. We developed a novel enzyme-linked immunosorbent assay (ELISA) that is specific for PrP aggregate by screening 30 anti-PrP monoclonal antibodies (MAbs) for their ability to react with recombinant mouse, ovine, bovine, or human PrP dimers. One MAb that reacts with all four recombinant PrP dimers also reacts with PrP(Sc) aggregates in ME7-, 139A-, or 22L-infected mouse brains. The PrP(Sc) aggregate is proteinase K resistant, has a mass of 2,000 kDa or more, and is present at a time when no protease-resistant PrP is detectable. This simple and sensitive assay provides the basis for the development of a diagnostic test for prion diseases in other species. Finally, the principle of the aggregate-specific ELISA we have developed may be applicable to other diseases caused by abnormal protein aggregation, such as Alzheimer's disease or Parkinson's disease.