Abstract:
Tuberculosis is still one of the major health problems worldwide, with
high mortality and morbidity. While third of the world population is
infected with TB bacilli, the situation is getting worse by the rising
emergence of drug resistant strains of Mycobacterium tuberculosis.
Conventional method for drug susceptibility testing requires months
before results can be reported. However, rapid methods such as phage
assay have been developed and recorded as useful tool for quick
diagnosis.
This study is descriptive cross-sectional laboratory based study which
aimed to evaluate the usefulness of phage assay compared to proportional
method and PCR in the diagnosis of MDR TB, to estimate the prevalence
of MDR TB among tuberculosis patients and to detect the presence of
rpoB gene among multidrug resistant isolates.
This study was conducted in Kassala State during the period from August
2009 to January 2012. Sputum specimens were collected from ninety acid
fast bacilli consented patients (54 males and 36 females). Sputum
specimens were processed for direct D29 and culture. All successful
cultured isolates were subjected to biochemical tests for phenotypic
characterization and further genotypic confirmation was made by
amplification of IS 6110. For drug susceptibility testing, proportional
method was adopted followed by both indirect D29 and amplification of
rpoB gene.
The results showed that both males and females in different age groups
were infected with TB and those between 21-50 are of the highest
infection rate. 21 (23.3%) of the specimens were categorized as
rifampicin resistant by direct D29 method, 75/90 (83.3%) of the
specimens showed growth on LJ medium similar to MTB complex
colonies while 5/90 (3.3%) were identified as rapid growers.60 out of the
75 slow growers (80%) were confirmed as MTB complex members
depending on their biochemical characters (PNB, catalase and nitrate
reduction). DST result for the 60 MTB isolates showed that 31/60 were
drug resistant and that isoniazid compose for the highest percentage of
resistance (20/31), followed by rifampicin (19/31) while MDR was
detected in 18/60 of the isolates. All the 60 slow growers were confirmed
as MTB by their positive IS 6110 results and 15/60 were rpoB positive.
In conclusion, the study highlighted the high prevalence of MDR TB in
Kassala State. Moreover D29 phage method in its first trial of application
in Sudan revealed high sensitivity and specificity, which when combined
to its major character of time saving (3 days compared to 70 days in DST)
makes it a promising method for rapid uncostly diagnosis of MDR TB.
