As the number of lepromatous patients with acquired DDS-resistant leprosy increases,
the likelihood that they will become the source of infection of new cases showing
primary DDS-resistance, also increase. However, DDS-resistant leprosy, either primary
or secondary, can only be diagnosed by DDS-sensitivity test using the mouse footpad
sensitivity tests performed in 27 new patients with previously untreated lepromatous
leprosy and 43 relapsed lepromatous leprosy patients. The biopsied skin was
homogenized for the preparation of suspensions of Mycobacterium leprae for the
inoculation of hind footpads of mice. For the assessment of the DDS-sensitivity of the
strains of blycobacterium leprae, the inoculated mice were divided into four groups. One
group aetea as a control and the other groups received DDS incorporated in different
concentrations in their diet, such as 0.01%, 0.001% and 0.0001% DDS in the diet.
Of the 27 new cases, 18 (75%) had strains of Mycobacterium leprae that were fully
sensitive to DDS and six(25%) had DDS-resistant strains, however the other three
cases were control negative because of low bacterial index in the biopsied skin.
Of the six primary DDS-resistant cases, two showed high degree of resistance (0.01
% DDS diet), one was moderate resistance (0.001 % DDS diet) and three was low
resistance(0,0001% DDS diet).
Of the 43 relapse4 cases, five (21.7%) had strains of Mycobacterium leprae that were
fully sensitive to DDS and 18 (78.3%) had DDS-resistant strains, but the other 20 cases
were control negative due to low bacterial index in biopsied skin materials. Of the 18
acquired DDS-resistant cases, seven showed high resistance, nine moderate resistance
and two low resistance.
DDS resistance may be either acquired or primary. Acquired DDS resistance occurs as
a result of the selective multiplication of spontaneous drug resistant mutant bacilli
during the course of 335 therapy. Primary DDS resistance implies that the bacilli which
infected the patients were DDS-resistant from the beginning. Acquired DDS resistance
is now commonly seen among the relapsed leprosy patients, and is becoming a major
problem for many leprosy control services. In our observation, the prevalence of
suspected acquired DDS resistance is about eight per cent of known multibacillary cases
and the incidence of that may be about l.5% per annum among multibacillary cases
under treatment. All the leprosy patients tested were suffering from lepromatous leprosy.
DDS resistance in non-lepromatous leprosy cases has not yet been reported, and will
only be diagnosable on clinical grounds. However, all leprosy patients are likely to
derive their infections from the same index cases. It is therefore probabte that in areas
where primary DDS-resistant lepromatous leprose is found, non-lepromatous cases will
also often be DDS resistant.
The finding of primary DDS resistance on a significant scale in the country has
several important implications,
1. The stress is given to find out the acquired DDS resistant cases as many as
possible.
2. Multiple drugs therapy must become routine practice in leprosy control programmes.
3. Experimental chemotherapy is needed to determine optional drug regimens for the
treatment as well as the prevention of drug resistant leprosy.
4. To determine the extent of the problems, the survey of DDS resistance and other
drug-resistance using mouse foot-pad tests of patients with previously untreated
lepromatous leprosy should be planned.
5. Education of leprosy patients is more important in a combined chemotherapy
especially for domicilliary cases with multibacillary leprosy.
Since the survey has not covered the entire areas, we could not estimate the
prevalence of primary DDS resistance in the country. However, the results obtained
show the presence of primary DDS-resistant leprosy in the country in a significant
scale.
|