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Abstract
SUMMARY AND CONCLUSION
Tuberculosis is an infectious disease caused by mycobacteria. It is still of wide spread despite the great advance in therapeutic regimens. The WHO estimates that each year more than eight million new cases of tuberculosis occur, ninety five percent of them in developing countries. In Egypt, tuberculosis is the second most important public health problem after bilharziasis. So accurate and rapid detection of mycobacteria is essential for treatment of the patients and for control the spread of the disease in the community.
The aim of this work was to evaluate the value of the modern laboratory techniques including radiometric culture system BACTEC- 460 and flow cytometer in antimycobacterial drug susceptibility methods in active tuberculous patients.
This study was carried out at Clinical Pathology and Chest departments, Zagazig university and Zagazig chest hospital. It included twenty patients with pulmonary tuberculosis (15 denovo cases and 5 previously treated cases). They were subjected to full history taking, clinical examination, chest x- ray. Sputum samples from these patients were prepared and subjected to Z. N stain, culture on L.J medium, culture and drug susceptibility test on radiometric BACTEC- 460 culture system, and also flow cytometer to six antimycobacteiral drugs ;isoniazid, rifampicin, ethambutol, streptomycin, ciprofloxacin and ofloxacin.
The results of our study showed that:
-Flow cytometric study for susceptibility test for 20 cases using the six antimycobacterial drugs at their critical concentrations for 3 successive days:- The susceptibility to four drugs was increased in the 3rd day as follows: INH 12/20 (60%), RIF 15/20 (75%), ETM 12/20 (60%), STP 11/20 (55%) except for OFX of CIP the susceptibility was increased in the second day to 13/20 (65%) for both.
-Radiometric culture system was used for culture and susceptibility test of mycobacteria for 10 clinical cases to the six antimycobacterial drugs and the results of sensitivity were as follows: INH 4/10 (40%), RIF 7/10 (70%), ETM 5/10 (50%), STP 4/10 (40%), OFX 5/10 (50%) and CIP 6/10 (60%).
-Comparing the results of susceptibility between the BACTEC and flow cytometry on 10 clinical isolates showed that the BACTEC- 460 TB culture system is more sensitive as it discovered 3 resistant cases than the flow cytometry.
-The validity of flow cytometry for 3 successive days comparing it to the standard radiometric BACTEC- 460 TB for 10 clinical cases showed that.
-The sensitivity was 100% for the six drugs.
-The specificity was 83.3% for INH and STP and was 100% for RIF, ETM, CIP and OFX.
-The percentage of agreement was 90% for INH and STPand 100% for RIF, ETM, CIP and OFX.
-There was highly significant results of susceptibility tests to: RIF, ETM, OFX and CIP.
CONCLUSIONS
Flow cytometry and FDA staining can be used for rapid screening of resistant and susceptible clinical isolates of M. tuberculosis. This may allow the rapid initiation of effective treatment against M. tuberculosis and avoidance of unnecessary therapy that increase toxicity of antimycobacterial drugs and help the emergence of resistant strains. The assay is extremely simple, can be completed in 72 hours and does not require multiplication of the organism.
BACTEC- 460 culture system has also the ability of rapid, accurate screening for resistant and susceptible isolate of M. tuberculosis within a week and also the advantage of differenting of atypical mycobacteria from MTB complex by using NAP test. BACTEC- 460 culture system is more sensitive in detecting resistant strains than flow cytometry. Thus TB culture and susceptibility testing using BACTEC- 460 culture system could be considered the gold standard method.