In order to try to improve the results of direct smear microscopy, we used the mucus-digesting quality of chitin in tuberculosis (TB) laboratories. For this purpose, a total of 430 sputum specimens were processed by the N-acetyl-L-cysteine concentration, sodium hypochlorite (NaOCl) liquefaction, chitin sedimentation, and direct microscopy methods. Then, the smear sensitivity for acid-fast bacillus detection by chitin-treated sputum was compared with the sensitivity of smears prepared by other methods. Our results showed that the chitin solution took less time to completely homogenize the mucoid sputum than did the N-acetyl-L-cysteine and NaOCl methods. The N-acetyl-L-cysteine concentration method demonstrated sensitivity and specificity levels of 83 and 97%, respectively. In comparison, the sensitivity of chitin sedimentation was 80%, with a specificity of 96.7%. The NaOCl liquefaction method showed a sensitivity of 78%, with a specificity of 96%. Finally, the sensitivity of direct microscopy was lower than those of the other tested methods and was only 46%, with a specificity of 90%. The chitin and NaOCl liquefaction methods are both easy to perform, and they do not require additional equipment (centrifuges). Also, our results demonstrated that the chitin method is less time-consuming than the NaOCl method, since only 30 min of incubation is required to bring complete sedimentation of bacilli in chitin-treated sputum whereas the NaOCl method needs 10 to 12 h to give the same results in the same sputum specimens. Therefore, the chitin liquefaction and sedimentation method may provide better results in TB laboratories of developing countries than the N-acetyl-L-cysteine concentration, NaOCl overnight sedimentation, and direct smear microscopy methods.The microscopic examination of acid-fast bacilli (AFB) remains the main bacteriological tool for tuberculosis (TB) detection (1, 10). Previous studies showed that the technique sensitivity may vary depending on smearing, staining, and smear reading (5, 16). For proper smearing, N-acetyl-L-cysteine (CH 3 -CO-NH-CH-COOH-CH 2 SH) with 2% sodium hydroxide (NaOH) is considered the best (15). N-acetyl-L-cysteine (NaLc) acts as a strong mucus digester, and the processed smear has less debris and a greater concentration of AFB (15). However, since the method is costly and time-consuming and requires special equipment, it is not applicable in the vast majority of TB laboratories in developing countries (2, 11). In these countries, limited resources allow only direct microscopy (unconcentrated sputum) as the best available option for TB diagnosis (5,11,15). The technique has a low sensitivity, because it requires meticulous preparation of smears and is labor-intensive (14). In recent years, interest in improving the direct smear microscopy technique in developing countries has arisen (7, 13). For example, Miorner et al. demonstrated that the simple liquefaction and overnight sedimentation of sputum with sodium hypochlorite (NaOCl) would significantly augment smear sensitivity,...
A majority of the MDR-TB patients in Iran can be cured with the use of appropriate treatment regimens. An even greater success could be achieved by providing more second-line drugs.
The malachite green microtube (MGMT) susceptibility assay was performed directly on sputum specimens (n ؍ 80) and indirectly on Mycobacterium tuberculosis clinical isolates (n ؍ 60). The technique is based on the malachite green dye, which changes color in response to M. tuberculosis growth. The MGMT assay is simple and rapid and does not require expensive instruments.Recent advances in technology have introduced many rapid and reliable methods to differentiate between susceptible and resistant Mycobacterium tuberculosis strains (7,10,12,16). However, due to their high cost and equipment requirement, these new methods are not feasible in the clinical laboratories of developing countries in the diagnosis of tuberculosis (TB). Instead, these countries use the proportional method, which is very time-consuming (2, 11). Consequently, physicians base their diagnosis of TB on microscopy results. Therefore, supplementary rapid and reliable methods are highly needed for clinical laboratories with limited resources. In 1995, Yajko et al. (15) used an oxidation-reduction indicator, Alamar blue, which changes color in response to the growing bacteria. In 2004, we demonstrated the viability of M. tuberculosis in sputum specimens of TB patients using malachite green indicator dye, a compound routinely used in Löwenstein-Jensen (LJ) medium (3, 4). Malachite green is a triphenylmethane dye and has a dark green color, which becomes colorless during M. tuberculosis metabolism (6).In the present study, the malachite green indicator dye was used to assess the susceptibility of M. tuberculosis clinical isolates against first-and second-line anti-TB drugs. The test was also performed directly on sputum specimens of patients with pulmonary TB. In total, 80 sputum specimens from TB patients and 30 sputum specimens from patients without mycobacterial infection (e.g., with lung cancer or asthma) were collected. Furthermore, the malachite green microtube (MGMT) assay was tested indirectly on 60 M. tuberculosis clinical isolates and the M. tuberculosis H 37 R V ATCC 27294 reference strain (American Type Cell Culture Collection, Rockville, MD). The accuracy and feasibility of the MGMT assay were compared to those of the standard LJ culture method for drug susceptibility testing.Sputum specimens were digested and decontaminated by the Petroff method with a 2% final concentration of NaOH.
BackgroundDespite many prospective and retrospective studies about the association of dietary habit and lung cancer, the topic still remains controversial. So, this study aims to investigate the association of lung cancer with dietary factors.MethodIn this study 242 lung cancer patients and their 484 matched controls on age, sex, and place of residence were enrolled between October 2002 to 2005. Trained physicians interviewed all participants with standardized questionnaires. The middle and upper third consumer groups were compared to the lower third according to the distribution in controls unless the linear trend was significant across exposure groups.ResultConditional logistic regression was used to evaluate the association with lung cancer. In a multivariate analysis fruit (Ptrend < 0.0001), vegetable (P = 0.001) and sunflower oil (P = 0.006) remained as protective factors and rice (P = 0.008), bread (Ptrend = 0.04), liver (P = 0.004), butter (Ptrend = 0.04), white cheese (Ptrend < 0.0001), beef (Ptrend = 0.005), vegetable ghee (P < 0.0001) and, animal ghee (P = 0.015) remained as risk factors of lung cancer. Generally, we found positive trend between consumption of beef (P = 0.002), bread (P < 0.0001), and dairy products (P < 0.0001) with lung cancer. In contrast, only fruits were inversely related to lung cancer (P < 0.0001).ConclusionIt seems that vegetables, fruits, and sunflower oil could be protective factors and bread, rice, beef, liver, dairy products, vegetable ghee, and animal ghee found to be possible risk factors for the development of lung cancer in Iran.
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