Abstract:
Simple, rapid, and sensitive methods that enhance the detection of Mycobacterium
tuberculosis (M. tuberculosis) from sputum specimens are needed. This study
compared the sensitivity of ZN stain and polymerase chain reaction (PCR) in the
detection of M. tuberculosis from sputum specimens to achieve early and proper
diagnosis in order to start accurate regimen.
this is a cross-sectional laboratory-based study in which ١٧١ sputum specimens
were collected from patients suspected of having pulmonary tuberculosis attending
Abu-Anga Teaching Hospital, El Sha’ab Teaching Hospital and the Tuberculosis
Reference Laboratory at the national Health Laboratory in Khartoum, Sudan,
during the period from January to March 2010.
Sputum specimens were examined using Ziehl-Neelsen stain; all sputum
specimens extracted by Isopropanol method to obtain DNA and subjected to PCR
amplified IS6110 insertion sequence in terms of sensitivity. At same time all
sputum specimens were inoculated in Lowenstein Jensen (LJ) media and incubated
at 37°C.
Only 37(22%) were acid fast bacilli positive, whereas 145(85%) were PCR
positive with bands typical to the target sequence of IS6110 as showed by the
standard DNA marker, Ziehl-Neelsen technique sensitivity was found to be ٢٦%
compared to PCR assay.
Concerning cultivation of all sputum specimens on LJ media there were only
23.4% showed MTC-like colonies in LJ media (dry, rough and pale yellow),
whereas 5.8% were considered rapidly growing Mycobacterium, and 70.8%
samples revealed contamination or no growth. Further biochemical tests were used
beside colonial morphology in order to confirm the existence of Mycobacterium
tuberculosis complex.
The study concluded that though the sensitivity of ZN stain was quietly decreased,
PCR assay provides a significant improvement in diagnosis of pulmonary
tuberculosis.
