Diagnostic efficacy of Ziehl-Neelsen method against fluorescent microscopy in detection of acid fast bacilli

A Comparative Study of Ziehl-Neelsen Stain and Fluorescent Stain Microscopy in the Diagnosis of Pulmonary Tuberculosis

Tuberculosis remains a global disease, killing over 2 million people each year. India accounts for two-third of the global total i.e. 26%. A good, fast, and economical test to diagnose a disease is urgently needed so that effective treatment can begin as soon as possible. Various investigations can be done for TB diagnosis and these include clinical suspicion, Chest imaging, acid-fast bacilli staining, MTB culture, serological methods and Assays for amplification of nucleic acids. For developing countries like India due to the enormous number of patients and budget restrictions, the assessment of a quick and low-cost diagnostic procedure is critical. A present prospective study was undertaken to compare Ziehl-Neelsen stain with Fluorescent stain microscopy in detecting of Mycobacterium tuberculosis in TB patient’s sputum samples. Among 274 sputum samples collected from suspected TB cases, 50 (18.2%) were positive by ZN and 116 (42.3%) were positive by fluorescent microscopy. The sensitivity, specificity, Positive predictive value (PPV) & Negative predictive value (NPV) of FM microscopy was 98%, 70%, 42%, and 99% respectively. FM microscopy was superior to ZN microscopy in detecting pulmonary tuberculosis cases as it could detect 24.1% more positive cases than ZN staining. Fluorescence staining provides better sensitivity and specificity and can detect accurately more paucibacillary cases hence is of diagnostic value and can help in the early treatment of pulmonary tuberculosis.

The yield of Auramine O staining using led microscopy with bleach treated sputum samples for detection of pulmonary tuberculosis at St. Peter tuberculosis specialized hospital, Addis Ababa, Ethiopia

Background

Smear microscopy is the mainstay for diagnosis of Tuberculosis (TB) in Ethiopia. This technique; however, is insensitive to detect Mycobacteria from most clinical specimens. Currently, light emitting diode (LED) fluorescence microscope is advocated to be used in high Tuberculosis (TB) burden settings by World Health Organization (WHO). However, the utility of this method is not evaluated for bleach treated sputum samples in Ethiopia.

Objective

The objective of the study is to evaluate the diagnostic importance of Auramine O (AO) staining in direct and concentrated sputum against conventional Zehil-Neelsen (ZN) and culture from the sputum samples of suspected pulmonary tuberculosis patients.

Methods

A cross-sectional study was conducted on 346 adult new pulmonary TB suspected patients at St. Peter's Specialized Hospital, Addis Ababa, Ethiopia. Three sputum samples (spot-morning-spot) were collected in sterile cups for direct Zehil-Neelsen and AO staining. Morning sputum samples were used for Mycobacterial culture on Mycobacterial Growth Indicator Tube (MGIT) 960. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were evaluated against the gold standard culture method. Data were analyzed using STATA version 13.0. All statistical tests were considered as statistically significant if the two sided P-value was < 0.05.

Results

Bleach treated sputum samples with AO staining yielded more cases as compared to direct ZN and direct AO by 6.3% and 11.5%, respectively. The sensitivity of concentrated AO and direct AO were remarkably high as compared to conventional ZN (71.8% vs. 44.5% and 62.7% vs. 44.5%). The concentrated sputum with staining of AO had a high rate (18.6%) of detecting scanty graded smears as compared to conventional ZN method.

Conclusions

Our findings indicated that the concentrated sputum with AO staining yielded high rate of sensitivity (71.8%) as compared to the conventional ZN method (44.5%). Moreover, the concentrated sputum with AO staining had superior ability in detecting scanty graded smears compared to the conventional ZN method. Therefore, it is recommended to utilize AO staining with LED microscopy for better diagnosis of Acid Fast Bacilli (AFB) from TB suspected cases and patients with pauci-bacillary TB in Ethiopia.

Smartly Engineered PEGylated Di-Block Nanopolymeric Micelles: Duo Delivery of Isoniazid and Rifampicin Against Mycobacterium tuberculosis

In an attempt to deliver multiple drugs through a nanoparticulate platform, the present study was designed to deliver isoniazid (INH) and rifampicin (RMP) together through conjugation/encapsulation approaches using PEG-PLA (polyethylene glycol-poly-L-lactic acid) polymeric micelles. The objective of this study is to identify the preparation and evaluation of PEGylated polymeric micelles with dual drug delivery of INH and RMP for the effective treatment of tuberculosis (TB). Synthesized PEG-PLA di-block-copolymer was further conjugated to INH-forming PEG-PLA-INH (PPI) conjugate. Separately, these conjugates were loaded with RMP building the rifampicin-loaded PEG-PLA-INH polymeric micelles (PMC). The critical micelle concentration (CMC) for the PEG-PLA copolymer was found to be 8.9 ± 0.96 mg/L, and the size and zeta potential were observed to be 187.9 ± 2.68 nm and - 8.15 ± 1.24 mV (0.251 ± 0.042 pdi), respectively. Percent drug loading of PMC was 16.66 ± 1.52 and 23.07 ± 1.05 with entrapment efficiency of 72.30 ± 3.49 and 78.60 ± 2.67% for RMP and INH, respectively. RBC hemolysis capacity of PMC was significantly less than pure RMP and INH. Microplate Alamar blue assay (MABA) along with microscopy showed that the nanoconstructed PMC were more effective than the drugs, and approximately 8-fold reduction in overall minimum inhibitory concentration (MIC) was observed. The prepared duo drug-loaded nano-engineered polymeric micelles were highly effective against sensitive Mycobacterium tuberculosis strains and found to be less hemolytic in nature. The micelles could be further explored (in the future) for in vivo anti-TB studies to establish further to achieve better treatment for TB.

Diagnosis of Mycobacterium tuberculosis using molecular biology technology

OBJECTIVE

To present an integrated molecular biology dedicated system for tuberculosis diagnosis.

METHODS

One hundred and five sputum specimens from patients strongly suspected by clinical parameters of tuberculosis were studied by Ziehl-Neelsen staining, by cultivation on solid medium and by a balanced heminested fluorometric PCR system (Orange G3TB) that could preserve worker safety and produce a rather pure material free of potential inhibitors. DNA amplification was performed in a low cost tuberculosis termocycler-fluorometer. Produced double stranded DNA was flurometrically detected. The whole reaction was conducted in one single tube which would not be opened after adding the processed sample in order to minimize the risk of cross contamination with amplicons.

RESULTS

The assay was able to detect 30 bacillus per sample mL with 99.8% interassay variation coefficient. PCR was positive in 23 (21.9%) tested samples (21 of them were smear negative). In our study it showed a preliminary sensitivity of 94.5% for sputum and an overall specificity of 98.7%.

CONCLUSIONS

Total run time of the test is 4 h with 2.5 real working time. All PCR positive samples are also positive by microbiological culture and clinical criteria. Results show that it could be a very useful tool to increase detection efficiency of tuberculosis disease in low bacilus load samples. Furthermore, its low cost and friendly using make it feasible to run in poor regions.