Microvesicles released from pneumolysin-stimulated lung epithelial cells carry mitochondrial cargo and suppress neutrophil oxidative burst

Microvesicles (MVs) are cell-derived extracellular vesicles that have emerged as markers and mediators of acute lung injury (ALI). One of the most common pathogens in pneumonia-induced ALI is Streptococcus pneumoniae (Spn), but the role of MVs during Spn lung infection is largely unknown. In the first line of defense against Spn and its major virulence factor, pneumolysin (PLY), are the alveolar epithelial cells (AEC). In this study, we aim to characterize MVs shed from PLY-stimulated AEC and explore their contribution in mediating crosstalk with neutrophils. Using in vitro cell and ex vivo (human lung tissue) models, we demonstrated that Spn in a PLY-dependent manner stimulates AEC to release increased numbers of MVs. Spn infected mice also had higher levels of epithelial-derived MVs in their alveolar compartment compared to control. Furthermore, MVs released from PLY-stimulated AEC contain mitochondrial content and can be taken up by neutrophils. These MVs then suppress the ability of neutrophils to produce reactive oxygen species, a critical host-defense mechanism. Taken together, our results demonstrate that AEC in response to pneumococcal PLY release MVs that carry mitochondrial cargo and suggest that these MVs regulate innate immune responses during lung injury.

Transmission dynamics of tuberculosis in a high-incidence country: prospective analysis by PCR DNA fingerprinting

We have prospectively analyzed the DNA fingerprints of Mycobacterium tuberculosis strains from a random sample of patients with newly diagnosed tuberculosis in Windhoek, Namibia. Strains from 263 smear-positive patients in whom tuberculosis was diagnosed during 1 year were evaluated, and the results were correlated with selected epidemiological and clinical data. A total of 163 different IS6110 fingerprint patterns were observed among the 263 isolates. Isolates from a high percentage of patients (47%) were found in 29 separate clusters, with a cluster defined as isolates with 100% matching patterns. The largest cluster included isolates from 39 patients. One predominant strain of M. tuberculosis caused 15% of cases of smear-positive pulmonary tuberculosis in Windhoek. That strain was also prevalent in the north of the country, suggesting that in contrast to other African countries with isolates with high levels of diversity in their DNA fingerprint patterns, only a restricted number of different strains significantly contribute to the tuberculosis problem in Namibia.

Surveillance of resistance to antituberculosis drugs in developing countries

Resistance to antituberculosis drugs is caused by poor management of tuberculosis control. It gives rise to treatment failure, relapse, further transmission of resistant tuberculosis, and multidrug-resistant tuberculosis. Widespread occurrence of multidrug-resistant tuberculosis would constitute a major threat to tuberculosis control in resource-poor countries. Although the impact of HIV on drug resistance is not yet fully understood, it is likely to exacerbate problems caused by drug resistance. In particular, HIV-related adverse effects of thiacetazone, together with the risks of transmission of HIV by parenteral administration of streptomycin, reduce the armamentarium available to tuberculosis control programmes in high HIV prevalence countries, and could encourage the development of resistance to the remaining drugs. While the prime need is to ensure, by good management and supervision, that resistance does not occur in the first place, surveillance of drug resistance is essential to determine the current scale and nature of the drug resistance problem, as well as to define the correct solutions.

The diagnosis of pulmonary tuberculosis by gaschromatographic detection of tuberculostearic acid using flame ionisation detectors

It has been shown that the detection of tuberculostearic acid (TBSA) with gas chromatography-mass-spectrometry provides a highly specific, sensitive and rapid method for the diagnosis of various forms of tuberculosis. However, the need for complex and expensive equipment prevented the more widespread use of this method. We report on the application of conventional gas chromatography with flame ionization detectors in the detection of TBSA in sputum samples. TBSA was detected in all patients with proven pulmonary tuberculosis before treatment or under treatment for less than 4 weeks (n = 18). Six of these patients (33%) had a negative microscopy result at the time of the study. Sputum samples from patients under therapy for longer than 4 weeks (n = 20) were TBSA-positive in 15 cases (75%). Only in two cases was the diagnosis by microscopy and/or culture not met by TBSA-detection. All sputa of 20 control patients with lung diseases other than tuberculosis were TBSA negative. Additional analysis of patients' data showed a significant relationship (P < 0.005) between the relative amounts of TBSA detectable in the sputum samples and the duration of therapy. It is concluded that conventional capillary gaschromatography may be sensitive and specific enough to be used for the detection of TBSA in sputum of patients with pulmonary tuberculosis.

Drug-resistant tuberculosis: laboratory issues. World Health Organization recommendations

There is a suggestion that drug resistance rates decreased in developing countries over the period 1962-85, while recent data suggest that resistance may be increasing. The initial decrease in resistance appears to be associated with well-functioning National Tuberculosis Control Programmes (NTP), while the recently observed increase may be due either to understaffed, resource-poor programmes or to the effect of the HIV epidemic, or to both. It is possible that the HIV epidemic may overwhelm the NTP, resulting in decreased programme efficiency and ultimately increased drug resistance. Resistance surveillance appears to be a good measure of programme efficiency. For research purposes, primary drug resistance surveys should be done on a sample of relevant patients which includes and distinguishes between HIV-positive and HIV-negative patients. At this time, there is not enough information to warrant a recommendation regarding HIV testing of TB patients for surveillance purposes. In order for resistance surveys to be relevant from the public health perspective, one must know the proportion of patients presenting for treatment having previously received treatment. The meaningful denominator for drug resistance surveys from the programme evaluation perspective should be the number of patients presenting for treatment. For initial drug resistance surveys the measurement should be the number of people never having received prior TB treatment with resistant bacilli, divided by the number of new patients presenting for treatment. For acquired resistance, one should look at all patients who begin treatment with susceptible bacilli who become resistant 6 months later.