Electrophoretic karyotype of environmental isolates of Paracoccidioides brasiliensis.

Five of the 12 environmental isolates of the dimorphic fungus Paracoccidioides brasiliensis known to date, were analysed by contour-clamped homogeneous electric field gel electrophoresis (CHEF). The electrophoretic pattern was shown to consist of five bands, with molecular size ranging from 3.2 to 10 Mb, a model quite similar to the one found in the clinical isolates previously tested and used here as controls. However, one of the bands in the environmental isolates had a lesser weight (7.2 Mb), than the one corresponding to the clinical counterparts (8.8 Mb). This resulted in a smaller genome, approximately 29.7 Mb. The small differences that were found indicate the presence of chromosome polymorphism in this fungus.

Electrophoretic karyotype of clinical isolates of Paracoccidioides brasiliensis.

Chromosomal DNA molecules were obtained from eight clinical isolates of Paracoccidioides brasiliensis during the early staged of the yeast to mycelial transformation process and were separated by contour-clamped homogeneous electric field gel electrophoresis. In seven of the isolates, it was possible to separate five bands, albeit with two different migration patterns (A and B). In the remaining isolate only four bands were observed (pattern C). The isolated chromosomes showed molecular sizes ranging from 3.2 to 10 Mb according to Schizosaccharomyces pombe molecular size standards. The three different patterns observed had bands of 3.2, 3.8, 4.1, 5.2, 6.7, 7.2, 8.8, and 10 Mb. These data imply that at least 30 Mb of the genome are organized as chromosomal macromolecules. Due to the fact that P. brasiliensis spheroplasts are difficult to obtain, technical details are provided.

Blood groups and malaria.

The possible relationship between erythrocyte antigens and the presence of malaria infection by P. vivax and P. falciparum was sought in four different ethnic groups of two departments of Colombia. Malaria infection by P. falciparum was found in 91.4% of malaria infected blacks. No significant differences were found between the presence of malaria infection and ABO antigens. In the other blood groups, it was observed that groups MNSs conferred black people a greater Rr for malaria by both species of Plasmodium and that Duffy-negative blacks and indians appeared to be resistant to P. vivax infection. A predominance of P. vivax infection was observed in Katio Indians while P. falciparum was predominant in Kuna Indians; the reason for this finding still needs to be explored.

A new serotype of Bacillus thuringiensis from Colombia toxic to mosquito larvae.

During a survey conducted in Colombia a new isolate of Bacillus thuringiensis that showed toxicity toward Culex quinquefasciatus, Cx. pipiens, Aedes aegypti, and Anopheles stephensi larvae was isolated. Parasporal crystals were spherical in shape and showed a great degree of similarity with those produced by the reference strain of Bacillus thuringiensis subsp. israelensis. Supernatant fraction of the whole culture was not toxic, and heat-stable exotoxin production was negative. Catalase, urease, arginine dihydrolase, amylase, lecithinase, acetyl-methyl-carbinol, and gelatinase production were positive. Hemolysis on sheep blood agar was alpha-type. The isolate 163-131 showed natural resistance to azolocillin and was sensible to cephoperazone, cephalotin, nalidixic acid, and trimetoprin sulfametoxazole. Flagellar agglutination showed a specific H 30 antigen which allows individualization of this strain as a new serotype and the subspecies name of medellin is proposed.

Reduction of malaria prevalence after introduction of Romanomermis culicivorax (Mermithidae: Nematoda) in larval Anopheles habitats in Colombia.

The worldwide resurgence of malaria has become a major public health problem. New methods of controlling the vectors of the disease are required, and we therefore studied the biological control of Anopheles albimanus by Romanomermis culicivorax in Colombia. The investigation was carried out in El Valle and Nuquí, two towns on the northern Pacific coast of the country. All of the mosquito larval habitats surrounding El Valle were seeded with the eggs and adults of R. culicivorax. The nematode established itself in the new habitat and recycled over 27 months. The larval population of A. albimanus, the only malarial vector detected in the two towns, decreased in El Valle. In contrast, no change in the larval populations of the vector was detected in ponds located near Nuquí, the untreated control town. A rapid and progressive decrease of the prevalence of malaria among schoolchildren in El Valle was observed during the 2-year evaluation period.