Tuberculosis

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  • Publicado : 29 de febrero de 2012
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There are many infectious diseases that despite modern technological advances have not yet been able to put aside the use of laboratory procedures developed in the late 19th century. The list of diseases includes tuberculosis, malaria, bartonellosis, leishmaniasis, etc with high prevalence in developing countries. In 1993, the World Health Organization (WHO) declared Tuberculosis (TB) a globalpublic health emergency [12].Tuberculosis is a contagious disease caused by a bacterium called Mycobacterium tuberculosis (the most common agent) [1]. TB remains an important public health problem worldwide, with nearly nine million new cases and more than 1.7 million deaths reported worldwide each year [6]. Diagnosis of pulmonary TB (PTB) in resource-poor settings has traditionally relied on sputumsmear microscopy using the Ziehl-Neelsen (ZN) staining technique, which is inexpensive and not technically demanding [5]. However, compared with culture, the method has low sensitivity, particularly in patients co-infected with the human immunodeficiency virus (HIV). As a result, patients with smear-negative but culture-positive TB pass undetected through health care systems where smearmicroscopy is the only diagnostic modality available, and are told incorrectly that they do not have TB. Some, but presumably not all, find their way back to the clinic when their disease has advanced sufficiently to be detectable by smear microscopy. In the interim, such individuals will have accrued greater morbidity and will have continued transmitting M. tuberculosis to their contacts. Culture of M.tuberculosis from clinical material is the “gold standard” for diagnosis of TB which normally requires 3-8 weeks time due to long doubling time (18 h) of M. tuberculosis [4]. The identification of Mycobacterium to the species level in all positive cultures is important because of the clinical significance. The identification of M. tuberculosis is time-consuming using conventional biochemicalmethods, that can take as long as eight to ten weeks. It is therefore not commonly used as a method for diagnosis of TB. The increasing number of multi-drug resistant strains of M. tuberculosis has increased the need for rapid and reliable methods of diagnosis and drug susceptibility testing (DST). The Lowenstein-Jensen (LJ) or agar proportion method (PM) and the radiometric method in BACTEC TB-460system (Becton-Dickinson) are the current standard methods recommended to perform susceptibility testing of M. tuberculosis [2, 3]. However they are either time consuming or require the use of radioisotopes, that should be disposed of. The turnaround time is important in order for the patient to receive an appropriate treatment. Recently, new commercial methods were developed, including MycobacterialGrowth Indicator Tube (MGIT) and molecular tests such as INNOLIPA Rif TB (Innogetics, Ghent, Belgium). However they are rapid, but expensive, making them impractical for use in developing countries. Therefore, the field of research into new technologies for the diagnosis of TB is constantly evolving. Nowadays, no single diagnostic test satisfies all the demands of “quick”, “cheap”, and “easy”.On the other hand, coordinated microbial collectives are associated with numerous public health issues and the origin of significant expenses aimed at their control and removal. In the clinical practice, the procedures related to the implantation of catheters are among the activities with a highest occurrence of bacterial biofilm growth [7]. A significant ratio of the morbidity and mortality inend-stage renal disease patients treated with hemodialysis is caused by bacteriemia [8], which are frequently associated with biofilm growth. As evidence of the magnitude of this problem, catheter-related bloodstream infections (CRBSI) in France, Germany, Italy and UK have an incidence of 14400, 8400, and 8500, 8940 cases per year [9]. Their associated cost in USA for hemodialysis patients is of...
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