HIV infection and AIDS in Latin America. Epidemiologic features and clinical manifestations

This article updates the epidemiologic situation of HIV and AIDS infection and summarizes the most common clinical manifestations in Latin American countries. As of December 1992, a total of 59,723 AIDS cases had been reported to the Pan American Health Organization from Mexico, Central America, South America, and the Latin Caribbean. The number of deaths totaled 24,500, or 41% of the reported cases. HIV transmission patterns and clinical manifestations vary by region. The most common opportunistic illnesses in Latin America and their symptoms, including gastrointestinal, pulmonary, and dermatologic complications are discussed.

Efficacy of ivermectin in the treatment of strongyloidiasis complicating AIDS

Nine adult male homosexuals who were infected with the human immunodeficiency virus (five with AIDS-defining conditions) and harbored Strongyloides stercoralis received ivermectin on a compassionate basis for persistent intestinal infection. Hyperinfection was present in all cases. Ivermectin was given either as a single oral dose (200 micrograms/kg) or on a multidose schedule (200 micrograms/kg.d) on days 1, 2, 15, and 16. All seven patients who received multiple doses showed sustained clinical and parasitological cure, whereas one of two patients who received single-dose therapy relapsed promptly and fatally. Remissions have been maintained for at least 7 months and up to 3 years of follow-up. Ivermectin appears promising in the treatment of strongyloidiasis in patients with AIDS. Because of the risk of hyperinfection and/or disseminated disease, multidose courses are warranted. We are not aware of other reports describing the efficacy of antiparasitic drugs for strongyloidiasis in patients with AIDS.

Molecular analysis of a microaerobically induced operon required for hydrogenase synthesis in Rhizobium leguminosarum biovar viciae

The nucleotide sequence (6138 bp) of a microaerobically inducible region (hupV/VI) from the Rhizobium leguminosarum bv. viciae hydrogenase gene cluster has been determined. Six genes, arranged as a single operon, were identified, and designated hypA, B, F, C, D and E based on the sequence similarities of all of them, except hypF, to genes from the hydrogenase pleiotropic operon (hyp) from Escherichia coli. The gene products from hypBFCDE were identified by in vivo expression analysis in E. coli, and their molecular sizes were consistent with those predicted from the nucleotide sequence. Transposon Tn5 insertions into hypB, hypF, hypD and hypE resulted in R. leguminosarum mutants that lacked any hydrogenase activity in symbiosis with peas, but still were able to synthesize the polypeptide for the hydrogenase large subunit. The gene products HypA, HypB, HypF and HypD contained CX2C motifs characteristic of metal-binding proteins. In addition, HypB bore a long histidine-rich stretch of amino acids near the N-terminus, suggesting a possible role in nickel binding for this protein. The gene product HypF, which was translationally coupled to HypB, presented two cysteine motifs (CX2CX18CX2C) with a capacity to form zinc finger-like structures in the N-terminal third of the protein. A role in nickel metabolism in relation to hydrogenase synthesis is postulated for proteins HypB and HypF.

[Factors associated with hypoalphalipoproteinemia]

BACKGROUND

Hypoalphalipoproteinemia (HALP) is the most frequent lipid alteration found in patients with myocardial infarction at an early age. It is defined by amounts of lipid cholesterol at high density lipoproteins (cHDL) lower than 10% according to age and sex. The aim of this study was to know the frequency of main factors which reduce the levels of cHDL in a group of subjects with and without HALP.

METHODS

Pathological antecedents, consumption of drugs, alcohol and cigarettes, the presence of obesity and levels of cholesterol, triglycerides, cHDL, glucose and urea were studied in a group of 1825 males. The study was performed in the course of medical examinations for workers.

RESULTS

The consumption of cigarettes, the index of body mass (IBM) and the prevalence of diabetes mellitus were higher in the group of subjects with HALP. Hypertriglyceridemia (triglycerides > or = 200 mg/dl) was found in 31% of the subjects with HALP vs 10% in the control group (p < 0.001); hypocholesterolemia (cholesterol < or = 150 mg/dl) was also significantly greater (9.8% vs 4.3%, p < 0.01). Altogether, in 64% of the subjects with HALP, factors which may decrease cHDL were associated. Of the factors studied, the number of triglycerides, IBM and the number of cigarettes consumed per day were the independent factors which most significantly contributed to the decrease of cHDL in the regression analysis.

CONCLUSIONS

Most of the subjects with hypoalphalipoproteinemia present other modifiable factors such as an elevated index of body mass, cigarette consumption and high amounts of triglicerydes, the correction of which constitutes the base for treatment of this disorder.

Nucleotide sequence and characterization of four additional genes of the hydrogenase structural operon from Rhizobium leguminosarum bv. viciae

The nucleotide sequence of a 2.5-kbp region following the hydrogenase structural genes (hupSL) in the H2 uptake gene cluster from Rhizobium leguminosarum bv. viciae UPM791 was determined. Four closely linked genes encoding peptides of 27.9 (hupC), 22.1 (hupD), 19.0 (hupE), and 10.4 (hupF) kDa were identified immediately downstream of hupL. Proteins with comparable apparent molecular weights were detected by heterologous expression of these genes in Escherichia coli. The six genes, hupS to hupF, are arranged as an operon, and by mutant complementation analysis, it was shown that genes hupSLCD are cotranscribed. A transcription start site preceded by the -12 to -24 consensus sequence characteristic of NtrA-dependent promoters was identified upstream of hupS. On the basis of the lack of oxygen-dependent H2 uptake activity of a hupC::Tn5 mutant and on structural characteristics of the protein, we postulate that HupC is a b-type cytochrome involved in electron transfer from hydrogenase to oxygen. The product from hupE, which is needed for full hydrogenase activity, exhibited characteristics typical of a membrane protein. The features of HupC and HupE suggest that they form, together with the hydrogenase itself, a membrane-bound protein complex involved in hydrogen oxidation.

Effects of an androgenic derivative on pre-established mammary tumours chemically induced in the rat

The effects were studied of an androgenic derivative--danazol--administered at doses of 10-12 mg kg-1 day-1 during 97 days to rats with dimethylbenz[a] anthracene-induced mammary tumours. Our main observations were as follows. (a) Danazol did not influence ovarian function at the end of the assay. (b) The treatment with danazol reduced the incidence (P less than 0.05), number of tumours (P less than 0.05) and volume of malignant mammary tumours; on the other hand, the values of these parameters for benign tumours and those of doubtful expression were similar in both experimental groups. (c) Such differential action of Danazol seems to be due to the different incidence and/or content of receptors of both types of tumours. (d) The latter results lead to a hypothesis for the mechanism of action of danazol based on its behaviour at different levels.

Differential expression of hydrogen uptake (hup) genes in vegetative and symbiotic cells of Rhizobium leguminosarum

The genetic determinants responsible for H2-uptake (hup genes) in Rhizobium leguminosarum are organized in six transcriptional units, designated regions hupI to hupVI, with region hupI coding for the hydrogenase structural genes (Leyva et al. 1990). Regulation of the expression of hup genes from R. leguminosarum was examined by using hup-lacZ fusions and mRNA dot-blot analysis. None of the six hup regions is transcribed in vegetative cells grown under normal aerobic conditions, whereas all six regions are transcribed in pea bacteroids. Additionally, exposure of cell cultures to low oxygen tensions specifically induces the expression of regions hupV and hupVI. By studying the expression of hupV- and hupVI-lacZ fusions in R. meliloti mutants it was determined that the microaerobic induction of these two regions is dependent on the regulatory fixLJ system, and that this control is exerted through fixK. Such expression was also shown to be nifA and ntrA independent. The functions of the hupV and hupVI gene products are unknown. The possibility that they play a regulatory role in hup gene expression is unlikely, since pea bacteroids from R. leguminosarum Hup- mutants carrying Tn5 insertions in regions hupV and hupVI contained normal levels of mRNA transcripts corresponding to the remaining hup regions.

Effect of priming with carrier on response to conjugate vaccine

To examine whether prior immunity against a carrier protein modulates the serological response to injected peptide haptens attached to the same carrier in man, baseline tetanus antitoxin levels in volunteers who received a malaria sporozoite peptide-tetanus toxoid conjugate vaccine were compared with post-vaccination IgM and IgG antibody titres against the sporozoite antigen. In tetanus-vaccinated North American recipients of low doses of conjugate vaccine there were significant dose-dependent negative correlations between these variables, which suggests that epitopic suppression may occur in man. In contrast, Venezuelans living in non-malarious areas and mostly naive to tetanus toxoid showed a notable IgM response to the sporozoite antigen. The findings indicate that epitopic suppression and immune enhancement occur in man, and that the specific immunological responses to conjugate peptide vaccines may be difficult to predict.

Occurrence of H(2)-Uptake Hydrogenases in Bradyrhizobium sp. (Lupinus) and Their Expression in Nodules of Lupinus spp. and Ornithopus compressus

Fifty-four strains of Bradyrhizobium sp. (Lupinus) from worldwide collections were screened by a colony hybridization method for the presence of DNA sequences homologous to the structural genes of the Bradyrhizobium japonicum hydrogenase. Twelve strains exhibited strong colony hybridization signals, and subsequent Southern blot hybridization experiments showed that they fell into two different groups on the basis of the pattern of EcoRI fragments containing the homology to the hup probe. All strains in the first group (UPM860, UPM861, and 750) expressed uptake hydrogenase activity in symbiosis with Lupinus albus, Lupinus angustifolius, Lupinus luteus, and Ornithopus compressus, but both the rate of H(2) uptake by bacteroids and the relative efficiency of N(2) fixation (RE = 1 - [H(2) evolved in air/acetylene reduced]) by nodules were markedly affected by the legume host. L. angustifolius was the less permissive host for hydrogenase expression in symbiosis with the three strains (average RE = 0.76), and O. compressus was the more permissive (average RE = 1.0). None of the strains in the second group expressed hydrogenase activity in lupine nodules, and only one exhibited low H(2)-uptake activity in symbiosis with O. compressus. The inability of these putative Hup(+) strains to induce hydrogenase activity in lupine nodules is discussed on the basis of the legume host effect. Among the 42 strains showing no homology to the B. japonicum hup-specific probe in the colony hybridization assay, 10 were examined in symbiosis with L. angustifolius. The average RE for these strains was 0.51. However, one strain, IM43B, exhibited high RE values (higher than 0.80) and high levels of hydrogenase activity in symbiosis with L. angustifolius, L. albus, and L. luteus. In Southern blot hybridization experiments, no homology was detected between the B. japonicum hup-specific DNA probe and total DNA from vegetative cells or bacteroids from strain IM43B even under low stringency hybridization conditions. We conclude from these results that strain IM43B contains hup DNA sequences different from those in B. japonicum and in other lupine rhizobia strains.

Cyanide-resistant respiration in photosynthetic organs of freshwater aquatic plants

THE RATE AND SENSITIVITY TO INHIBITORS (KCN AND SALICYLHYDROXAMIC ACID[SHAM]) OF RESPIRATORY OXYGEN UPTAKE HAS BEEN INVESTIGATED IN PHOTOSYNTHETIC ORGANS OF SEVERAL FRESHWATER AQUATIC PLANT SPECIES: six angiosperms, two bryophytes, and an alga. The oxygen uptake rates on a dry weight basis of angiosperm leaves were generally higher than those of the corresponding stems. Leaves also had a higher chlorophyll content than stems. Respiration of leaves and stems of aquatic angiosperms was generally cyanide-resistant, the percentage of resistance being higher than 50% with very few exceptions. The cyanide resistance of respiration of whole shoots of two aquatic bryophytes and an alga was lower and ranged between 25 and 50%. These results suggested that the photosynthetic tissues of aquatic plants have a considerable alternative pathway capacity. The angiosperm leaves generally showed the largest alternative path capacity. In all cases, the respiration rate of the aquatic plants studied was inhibited by SHAM alone by about 13 to 31%. These results were used for calculating the actual activities of the cytochrome and alternative pathways. These activities were generally higher in the leaves of angiosperms. The basal oxygen uptake rate of Myriophyllum spicatum leaves was not stimulated by sucrose, malate or glycine in the absence of the uncoupler carbonylcyanide-m-chlorophenylhydrazone (CCCP), but was greatly increased by CCCP, either in the presence or in the absence of substrates. These results suggest that respiration was limited by the adenylate system, and not by substrate availability. The increase in the respiratory rate by CCCP was due to a large increase in the activities of both the cytochrome and alternative pathways. The respiration rate of M. spicatum leaves in the presence of substrates was little inhibited by SHAM alone, but the SHAM-resistant rate (that is, the cytochrome path) was greatly stimulated by the further addition of CCCP. Similarly, the cyanide-resistant rate of O(2) uptake was also increased by the uncoupler.

[Ecology of Lutzomyia longipalpis (Lutz & Neiva, 1912) and possibilities of the existence of visceral leishmaniasis in Costa Rica]

A semiarid area of northwest Costa Rica where Lutzomyia longipalpis is common in corrals around houses is described. Monthly captures of the sandfly during two consecutive years for fixed periods of time indicated that the insect bites avidly cows, horses, pigs, dogs and humans. From a total of 14,215 specimens, 90.5% were males and the species is markedly more abundant during the dry season decreasing considerably when rain comes. The possibility that visceral leishmaniasis could become in the future established in the area is discussed, in view of the fact that it already exists endemically in other Central American countries.

Prophylaxis against enterococcal endocarditis: comparison of the aminoglycoside component of parenteral antimicrobial regimens

Prophylactic antibiotics for the prevention of enterococcal endocarditis are recommended for patients with valvular heart disease undergoing surgery or instrumentation of the genitourinary and gastrointestinal tracts. To evaluate the most active aminoglycoside antibiotic to include in these regimens, we administered streptomycin, gentamicin, or amikacin, each in combination with ampicillin, to six healthy adult volunteers in a crossover manner. When the sera from the volunteers were tested for bactericidal activity against 16 strains of enterococci, the gentamicin-ampicillin combination produced higher serum bactericidal levels for a longer duration of time against more strains than the other two regimens. At 1 h after antibiotic administration (a time when surgical procedures are likely to be performed), mean geometric bactericidal titers against the enterococci were 1: 7.0 for the gentamicin-ampicillin regimen, as compared with 1:3.6 and 1:3.2 for the streptomycin-ampicillin and amikacin-ampicillin combinations, respectively. Despite the lower serum levels for gentamicin, we feel that this aminoglycoside should be used in combination with ampicillin for prophylactic regimens against enterococcal endocarditis.

Gentamicin and ticarcillin serum levels

Ticarcillin disodium and gentamicin sulfate serum levels were measured one and five hours after intravenous administration. Patients receiving ticarcillin plus gentamicin had a significantly lower mean gentamicin level one and five hours after antibiotic administration than patients receiving cephalothin sodium plus gentamicin. The serum ticarcillin levels were significantly lower five hours after administration in patients receiving ticarcillin plus gentamicin than in those receiving ticarcillin plus cephalothin. Low antibiotic serum levels in patients with serious infections treated with these antibiotic combinations are of potential clinical significance; therefore, to ensure an optimal antimicrobial therapy, it is advisable to determine the drug serum concentrations (especially aminoglycoside) even in patients with normal renal function when treating with combinations of antimicrobials.

Leishmania herreri sp. n. from sloths and sandflies of Costa Rica

Leishmania herreri sp. n. is described after isolation in pure culture from blood, viscera and skin of two-toed (Choloepus hoffmanni) and three-toed (Bradypus griseus) sloths from Costa Rica. Also, it was isolated from the following sandflies: Lutzomyia trapidoi, L. ylephiletor and L. shannoni. The amastigote forms were not seen in the final hosts but they were obtained in tissue culture at 33 C. Both promastigotes and amastigotes failed to infect hamsters. The new parasite is isolated frequently in culture, mixed with other hemoflagellates such as L. braziliensis, Endotrypanum sp. and Trypanosoma rangeli.

Axillary lesions in patients with acute leukemia: evaluation of a preventive program

Axillary skin lesions can cause significant morbidity in patients with acute nonlymphocytic leukemia. The incidence in relation to the level of circulating granulocytes and the microbiology of 15 such lesions among 150 patients over a three year period were determined. Lesions occurred predominantly during periods of profound granulocytopenia (0-499 cells/microliter). Gram-negative bacilli were the most common pathogens isolated from these lesions. The initiation of a supervised preventive program for 84 patients over 19 months which includes the regular swabbing of each axilla with povidone-iodine cotton sticks in addition to measures to avoid skin trauma has virtually eliminated inflammatory axillary lesions in this high risk patient population.

Parenteral prophylaxis against enterococcal endocarditis

Three commonly used antibiotic regimens for the prevention of enterococcal endocarditis were administered parenterally to six healthy men in a crossover manner. The regimens included 1 gm of streptomycin intramuscularly (IM) in combination with (1) procaine penicillin 600,000 units plus aqueous penicillin G 200,000 units IM; or (2) ampicillin 25 mg/kg intravenously (IV); or (3) ampicillin 1 gm IM. The combinations containing ampicillin IM or IV with streptomycin produced bactericidal activity at dilutions of 1:2 or greater for the majority of the strains, whereas the penicillin-streptomycin regimen did not. All regimens were poorly bactericidal against three strains of enterococci which were highly resistant to streptomycin. These data suggest that ampicillin plus streptomycin is the preferred regimen for prophylaxis.

Invasive aspergillosis in acute leukemia: correlation with nose cultures and antibiotic use

Aspergillosis in cancer patients is a problem. Because not all patients can undergo invasive procedures, we sought other methods for diagnosis. We reviewed the data from all patients with acute nonlymphocytic leukemia treated at our center during a 3-year period. Of 125 patients, 18 had invasive aspergillosis (cases). Eleven patients had nose cultures growing Aspergillus flavus or A. fumigatus; 10 of these 11 had aspergillosis, whereas only eight of 114 without such nose cultures had invasive disease (P less than 0.000001). Thus, A. flavus on nose culture appears "predictive" for aspergillosis. Absence of such a culture does not preclude infection. Of 125 patients, 61 had sterile nose culture(s) and 14 of the 18 cases had such a sterile nose culture. Only four of the 64 patients without sterile nose cultures developed aspergillosis (P less than 0.008), suggesting a relation between sterile nose culture and aspergillosis. Carbenicillin was used for a longer period among cases and patients with predictive nose cultures than among patients without aspergillosis. These data may help identify patients at risk of aspergillosis and help determine antifungal therapy when invasive procedures are contraindicated.

Gastrointestinal tuberculosis mimicking cancer--a reminder

Tuberculous involvement of the gastrointestinal tract may be suspected in the presence of active pulmonary tuberculosis. This case demonstrates that tuberculous enteritis may develop in the absence of obvious pulmonary involvement. The diagnosis in such instances is established by a combination of roentgenographic studies and surgical exploration.