Identification of MDR-TB Beijing/W and other Mycobacterium tuberculosis genotypes in Nairobi, Kenya.

SETTING: Suspected tuberculosis (TB) patients in Nairobi, Kenya. OBJECTIVE: To identify the presence of multidrug-resistant (MDR) Beijing/W type and other genotypes of Mycobacterium tuberculosis. METHODS: Thirty-three isolates resistant to one or more drugs (resistance ratio method), including 15 MDR isolates and 40 susceptible isolates selected at random, were analysed by dot-blot hybridisation for mutations associated with resistance to isoniazid, rifampicin, streptomycin and ethambutol. All strains were genotypically classified using spoligotyping. RESULTS: Of the 33 drug-resistant isolates, 21 (64%) were from males and 12 (36%) were from females. Mutations associated with resistance to isoniazid (katG 315) and rifampicin (rpoB526, 531) were confirmed in 83.3% and 100% of the isolates, respectively, and in 87% of the MDR isolates. Mutations were detected in 25% and 71.5% of the isolates resistant to streptomycin (rpsL43) and ethambutol (embB306), respectively. No mutations were detected in drug-susceptible isolates. Spoligotyping grouped the isolates into 25 groups. Ten of these groups corresponded to previously identified strain groups, including seven families in the international database. One of these families (CAS1) comprised six (40%) of the 15 MDR isolates. Another family (Beijing) had six (8.3%) isolates, of which two (33.3%) were MDR (Beijing/W). CONCLUSION: This study is the first in Kenya and the second in sub-Saharan Africa to report the presence of MDR Beijing/W type and other possible drug-resistant outbreak strains. Application of the molecular techniques and markers will allow us to monitor the spread of existing drug-resistant strains and the appearance of new ones.

Anti-tuberculous initial drug resistance of Mycobacterium tuberculosis in Kenya: a ten-year review.

Our experience at the Respiratory Diseases Research Unit (RDRU), over the last 10 years (1981-1990) on the initial drug resistance pattern, focusing on three drugs viz: isoniazid (H), streptomycin (S) and rifampicin (R) is presented. Records on all isolates of M. tuberculosis from one specimen of every newly diagnosed patient recruited countrywide between 1981-1990 were reviewed. We analyzed records of 6,514 isolates and found that total resistance to the three drugs had increased from 8.9% to 14.4%. Resistance to H alone increased from 6.8% to 10.2% while that of S alone from 0.8% to 1.8%. Resistance to R was between 0.1% and 0.3%. Generally, the increase in the resistance trend to both H and S was statistically significant (p = < 0.05 and 0.03, respectively). Although in our analysis we did not address the possible impact of HIV infection, we hope that these findings form a basis for evaluation of this and other possible factors on the emergence of anti-TB drug resistance in future studies.

PIP: A retrospective review of medical records of 6514 Mycobacterium tuberculosis isolates of newly diagnosed patients at the Respiratory Diseases Research Unit of the Kenya Medical Research Institute between 1981 and 1990 aimed to determine the initial drug-resistance pattern for isoniazid, streptomycin, and rifampicin. Overall resistance increased from 8.9 to 14.4% (p 0.001). The increase in the resistance trend to isoniazid and to streptomycin were statistically significant (6.8-10.2; p 0.05 and 0.8-1.8; p = 0.03, respectively) as well as the trend among isolates resistant to both isoniazid and streptomycin (1.2.4; p = 0.03). The trend was more pronounced during 1987-1990 than during 1981-1986. There was no trend in the resistance to rifampicin alone (0.1-0.3%). Just 4 isolates were resistant to both isoniazid and rifampicin. Only 1 was resistant to both streptomycin and rifampicin. None were resistant to all 3 antibiotics. These first-line drugs are used widely in Kenya. These rates of initial resistance to the drugs are lower than those in other developing countries. The lower resistance rate is unlikely to continue, however, due to higher prevalence of HIV infection and the associated increase in tuberculosis incidence. These findings provide researchers a baseline with which to study M. tuberculosis drug resistance and other risk factors as drug resistance increases in Kenya.

Use of common reagent containers to stain sputum smears for acid fast bacilli using ziehl-neelsen technque

The use of common reagent containers for mass staining of sputum smears for acid fast bacilli (AFB) by the Ziehl-Neelsen (ZN:) Technique has previously been discouraged for fear of cross contamination. We undertook the present study to ascertain whether this fear has any justification. Out of 1296 smears prepared from 198 specimens including 9 known negative controls; 108 stainings were performed. 70 specimens and all positive controls were repeatedly positive on different stainings. 69 (99) cases and all positive controls were confirmed by culture. No carry over of AFB from positive to negative smears was experienced. Time; cost and staining mess was significantly reduced during mass eestaining. The use of a common container for staining of sputum smears for AFB by the ZN technique is not only economical but also ideal for laboratories where space is insufficient and larg numbers of sputum specimens are involved