Evaluation of Dot-Blot and Phage Replication Techniques for Detection of Drug Resistant Mycobacterium Tuberculosis

We have assessed the utility of two new methods; dot-blot and bacteriophage replication techniques; for use in a routine diagnosis laboratory in poor resource settings in the screening of drug resistant Mycobacteria tuberculosis by comparing with the conventional proportion method. A total of 145 M. tuberculosis clinical isolates were tested for resistance to rifampicin; isoniazid; streptomycin and ethambutol. The dot blot had sensitivities of 91.7; 100; 93.5and 85.7 and specificities of 99.2; 99.2; 99.1and 99.2 for rifampicin; streptomycin; isoniazid and ethambutol; respectively. The phage technique had sensitivities of 92and 84.6and specificities of 99.2and 99.2for rifampicin and streptomycin; respectively. Both techniques yielded results within 48 hours of receipt of the culture on solid media.The high sensitivity and specificity coupled with rapidity of results indicate that these methods are potentially useful tools for screening resistance to anti-tuberculosis drugs in our setting. However; the phage replication technique; which is simpler and technically less demanding; seems the most suitable for routine screening of drug resistant mycobacteria in resource deprived countries such as Tanzania. We are recommending further field evaluation of the phage replication method so that it can complement; and possibly replace; the conventional proportion method in drug susceptibility testing

Visceral leishmaniasis in Teresina, state of Piauí, Brazil: preliminary observations on the detection and transmissibility of canine and sandfly infections

A Leishmania donovani-complex specific DNA probe was usedto confirm the widespread dissemination of amastigotes in apparently normal skinof dogs with canine visceral leishmaniasis. When Lutzomyia longipalpis were fed on abnormal skin of five naturally infected dogs 57 of 163 (35 per cent) fliesbecame infected: four of 65 flies (6 per cent) became infected when fed on apparently normal skin. The bite of a single sandfly that had fed seven days previouslyon a naturally infected dog transmitted the infection to a young dog from a non-endemic area. Within 22 days a lesion had developed at the site of the infectivebite (inner ear): 98 days after infection organisms had not disseminated throughout the skin, bone marrow, spleen or liver and the animal was still serologically negative by indirect immunofluorescence and dot-enzyme-linked immunosorbent assay. When fed Lu. longipalpis were captured from a kennel with a sick dog known to be infected, 33 out of 49 (67 per cent) of flies contained promastigotes. In contrast only two infections were detected among more than 200 sandflies captured in houses. These observations confirm the ease of transmissibility of L.chagasi from dog to sandfly to dog in Teresina. It is likely that canine VL is the major source of human VL by the transmission route dog-sandfly-human. the Lmet2 DNA probe was a useful epidemiological tool for detecting L. chagasi in sandflies