Susceptibility of Nectomys rattus (Pelzen, 1883) to experimental infection with Schistosoma mansoni (Sambon, 1907): a potential reservoir in Brazil

The aim of the present research was to evaluate the potential of Nectomys rattus, the "water rat", to develop Schistosoma mansoni infection. Comparison with N. squamipes was carried out. Both species of rodents were submitted to transcutaneous infection using different infective cercariae loads: 50, 100 or 500. N. rattus showed high susceptibility to S. mansoni, with an infection rate of 71%. Rodents were able to excrete viable eggs of S. mansoni in the feaces during all infection period. For both species, the small intestine, followed by the liver and the large intestine, presented the highest concentration of eggs among the surveyed organs. Infection caused no animal death. Moreover, N. rattus accomplished the parasite's life cycle, by infecting the snails Biomphalaria glabrata and later Mus musculus. These evidences indicate that both N. rattus, as for N. squamipes are potential reservoirs for schistosomiasis in Brazil. Considering the fact that N. rattus and N. squamipes exist in the same natural ecosystems of S. mansoni, we suggest that these rodents must be regarded as influential factors in epidemiology surveys.

Differential gene expression during Trypanosoma cruzi metacyclogenesis

The transformation of epimastigotes into metacyclic trypomastigotes involves changes in the pattern of expressed genes, resulting in important morphological and functional differences between these developmental forms of Trypanosoma cruzi. In order to identify and characterize genes involved in triggering the metacyclogenesis process and in conferring to metacyclic trypomastigotes their stage specific biological properties, we have developed a method allowing the isolation of genes specifically expressed when comparing two close related cell populations (representation of differential expression or RDE). The method is based on the PCR amplification of gene sequences selected by hybridizing and subtracting the populations in such a way that after some cycles of hybridization-amplification genes specific to a given population are highly enriched. The use of this method in the analysis of differential gene expression during T. cruzi metacyclogenesis (6 hr and 24 hr of differentiation and metacyclic trypomastigotes) resulted in the isolation of several clones from each time point. Northern blot analysis showed that some genes are transiently expressed (6 hr and 24 hr differentiating cells), while others are present in differentiating cells and in metacyclic trypomastigotes. Nucleotide sequencing of six clones characterized so far showed that they do not display any homology to gene sequences available in the GeneBank.

Usefulness of microsatellite typing in population genetic studies of Trypanosoma cruzi

Through microsatellite analysis of 53 monoclonal populations of Trypanosoma cruzi, we found a remarkable degree of genetic polymorphism with no single multilocus genotype being observed more than once. The microsatellite profile proved to be stable during 70 generations of the CL Brener clone in culture. The microsatellite profiling presented also high diagnostic sensitivity since DNA amplifications could be achieved with less than 100 fg DNA, corresponding to half parasite total DNA content. Based on these technical attributes the microsatellite assay turns out to be an important tool for direct typing T. cruzi in biological samples. By using this approach we were able to type T. cruzi in feces of artificially infected bugs and in single cells sorted by FACS. The microsatellites have shown to be excellent markers for T. cruzi phylogenetic reconstruction. We used maximum parsimony based on the minimum number of mutational steps to build an unrooted Wagner network, which confirms previous conclusions based on the analysis of the D7 domain of the LSU rDNA gene that T. cruzi is composed by two major groups. We also obtained evidence that strains belonging to rRNA group 2 are subdivided into two genetically distant clusters, and that one of these clusters is more related to rRNA group 1/2. These results suggest different origins for these strains.

Pneumònia postoperatòria: elaboració d’un protocol terapèutic guiat per la bacteriologia local en una unitat de crítics quirúrgics

Introducció: Aquest treball descriu les característiques de la pneumònia postoperatòria (POP) en una unitat de crítics quirúrgics (UCQ). Material i mètodes: Estudi retrospectiu de pacients amb sospita clínica de POP. Descriu entre altres: característiques dels pacients i de la pneumònia i antibioteràpia prescrita. Resultats: La POP resultà més freqüent en homes, després de cirurgia abdominal. La majoria de les POP van ser precoces, causades per BGN aerobis. Hi hagué un baix percentatge d’aïllaments de gèrmens multirresistents (MR). Conclusió: El tractament empíric de la POP d’inici precoç ha de cobrir els BGN aerobis. No és necessari cobrir els gèrmens MR.

The distribution of Biomphalaria spp. in different habitats in relation to physical, biological, water contact and cognitive factors in a rural area in Minas Gerais, Brazil

A total of 256 sites in 11 habitats were surveyed for Biomphalaria in Melquiades rural area (State of Minas Gerais) in August and November 1999 and in March 2000. Of the 1,780 Biomphalaria collected, 1,721 (96.7%) were B. glabrata and 59 (3.3%) B. straminea. Snails were found in all habitats except in wells, with the largest mean numbers in tanks, seepage ponds and canals, and the smallest numbers in springs, rice fields and fishponds. People's knowledge of the occurrence of Biomphalaria at the collection sites and the presence of Biomphalaria ova were strongly correlated with the occurrence of snails, and distance between houses and collection sites, as well as water velocity were inversely correlated with Biomphalaria occurrence (p < 0.001). The strongest predictor o f Biomphalaria occurrence was the presence of tilapia fish in fishponds. Fourteen Biomphalaria (0.8% of all snails) found at 6 sites were infected with Schistosoma mansoni. Suggestions are made for the utilization of local people's knowledge in snail surveys and further studies are recommended on the possible use of tilapia for biological control of Biomphalaria in fishponds, as well as modeling of S. mansoni transmission and reinfection.

Experimental evidence and ecological perspectives for the adaptation of Schistosoma mansoni Sambon, 1907 (Digenea: Schistosomatidae) to a wild host, the water-rat, Nectomys squamipes Brants, 1827 (Rodentia: Sigmodontinae)

Due to the semi aquatic habits and the overlap of the geographical distribution of the water-rat, Nectomys spp., with schistosomiasis endemic areas, these wild rodents are very likely to acquire Schistosoma mansoni infection in their daily activities. The role of the water-rat in the S. mansoni cycle would be substantiated if one could prove that these rodents acquire the parasite during their own activity time, a completely independent time schedule of human activities. To pursue this goal, we performed two field experiments in the municipality of Sumidouro, State of Rio de Janeiro, Brazil, a schistosomiasis endemic area where N. squamipes is found naturally infected. One experiment was devised as a series of observations of activity time of the water-rat. The other experiment was a test of the occurrence of late transmission of S. mansoni to the water-rat. The daily activity pattern showed that the water-rat is active chiefly just after sunset. At both diurnal and late exposition essays the water-rat sentinels got infected by S. mansoni. These findings clarify ecological and behavioral components necessary to the adaptation of S. mansoni to the water-rat as a non human definitive host and the existence of a transmission cycle involving this animals as a reservoir.

Evaluation of the impact of Bacillus thuringiensis serovar israelensis and Temephos, used for the control of Simulium (Chirostilbia) pertinax Kollar, 1832 (Diptera, Simuliidae) on the associated entomofauna, Paraty, state of Rio de Janeiro, Brazil

The study was set up to evaluate the impact of two commercial larvicide formulations, Bacillus thuringiensis serovar israelensis base (Bti) at 15 ppm/1 min and temephos at 0.03 ppm of active ingredient, used to control Simulium pertinax populations, on associated non-target entomofauna occupying the same breeding sites. The experiments were carried out on the Pedra Branca and Muricana rivers, on the slopes of Serra do Mar massif, municipality of Paraty, state of Rio de Janeiro, Brazil. Bti was applied to the river Pedra Branca and temephosto theriver Muricana. On both rivers, treatment and control sections were labeled as such, each one with two observation posts: slow moving water and fast water regions respectively. Artificial substrata was used to evaluate the abundance of associated entomofauna. Attached immature stages of arthropods were removed from both of its surfaces fortnightly. Were collected, from the two rivers, 28 477 specimens of the entomofauna associated with S. pertinax. The families Hydropsychidae, Chironomidae, Bactidae, Simuliidae, Blephariceridae and Megapodagrionidae were represented. These was an impact of temephos on the entomofauna associated with S. pertinax only in Simuliidae and Chironomidae, and to Bti only in Simuliidae. However, the reduction in their numbers was not statistically significant.

Improved surgical technique for laparoscopic Roux-en-Y gastric bypass reduces complications at the gastrojejunostomy.

Roux-en-Y gastric bypass (RYGBP) is one of the most commonly performed bariatric procedures for morbidly obese patients. It is associated with effective long-term weight loss, but can lead to significant complications, especially at the gastrojejunostomy (GJS). All the patients undergoing laparoscopic RYGBP at one of our two institutions were included in this study. The prospectively collected data were reviewed retrospectively for the purpose of this study, in which we compared two different techniques for the construction of the GJS and their effects on the incidence of complications. In group A, anastomosis was performed on the posterior aspect of the gastric pouch. In group B, it was performed across the staple line used to form the gastric pouch. A 21-mm circular stapler was used in all patients. A total of 1,128 patients were included between June 1999 and September 2009-639 in group A and 488 in group B. Sixty patients developed a total of 65 complications at the GJS, with 14 (1.2%) leaks, 42 (3.7%) strictures, and 9 (0.8%) marginal ulcers. Leaks (0.2% versus 2%, p = 0.005) and strictures (0.8% versus 5.9%, p < 0.0001) were significantly fewer in group B than in group A. Improved surgical technique, as we propose, with the GJS across the staple line used to form the gastric pouch, significantly reduces the rate of anastomotic complications at the GJS. A circular 21-mm stapler can be used with a low complication rate, and especially a low stricture rate. Additional methods to limit complications at the GJS are probably not routinely warranted.

Paleoepidemiology: is there a case to answer?

Paleopathology is the study of disease, physiological disruptions and impairment in the past. After two centuries of mainly descriptive studies, efforts are being made towards better methodological approaches to the study of diseases in human populations of ancient times whose remains are recovered by archaeology. Paleoepidemiology can be defined as an interdisciplinary area that aims to develop more suitable epidemiological methods, and to apply those in current use, to the study of disease determinants in human populations in the past. In spite of the limits of funerary or other archaeological series of human remains, paleoepidemiology tries to reconstruct past conditions of disease and health in those populations and its relation to lifestyle and environment. Although considering the limits of studying populations of deceased, most of them represented exclusively by bones and teeth, the frequency of lesions and other biological signs of interest to investigations on health, and their relative distribution in the skeletal remains by age and sex, can be calculated, and interpreted according to the ecological and cultural information available in each case. Building better models for bone pathology and bone epidemiology, besides a more complex theoretical frame for paleoepidemiological studies is a big job for the future that will need the incorporation of methods and technology from many areas, including the tools of molecular biology.

Usefulness of a Nested-polymerase chain reaction for molecular diagnosis of human T-cell lymphotropic virus type I/II

This study aimed at implementing a Nested-polymerase chain reaction (Nested-PCR) for the molecular diagnosis of human T-cell lymphotropic virus type I/II (HTLV-I and HTLV-II) infections in peripheral blood mononuclear cells of infected subjects in Argentina. The sensitivity and specificity of the assay for the detection of regional strains were assessed by comparing them with the molecular assay of reference PCR-hybridization. The Nested-PCR detected 1 MT-2 cell (³ 8 proviral copies)/1x106 non-infected cells showing high sensitivity for provirus detection. While both molecular assays showed high specificity (100%) for HTLV-I and HTLV-II detection, the sensitivity values differed: 100% for Nested-PCR and 67% for PCR-hybridization assay. Moreover, this technique showed less sensitivity for the detection of DNA sequences of HTLV-II (33%) than for the detection of DNA sequences of HTLV-I (75%). The high sensitivity and specificity of the Nested-PCR for regional strains and its low costs indicate that this assay could replace the PCR-hybridization assay for the molecular diagnosis of HTLV-I/II infections. It will be interesting to assess the usefulness of this assay as a tool for the molecular diagnosis of HTLV-I/II infections in other developing countries. Other studies that include a greater number of samples should be conducted.

The use of the polymerase chain reaction and restriction fragment length polymorphism technique associated with the classical morphology for characterization of Lymnaea columella, L. viatrix, and L. diaphana (Mollusca: Lymnaeidae)

The specific identification of Lymnaeid snails is based on a comparison of morphological characters of the shell, radula, renal and reproductive organs. However, the identification is complicated by dissection process, intra and interspecific similarity and variability of morphological characters. In the present study, polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) techniques targeted to the first and second internal transcribed spacers (ITS1 and ITS2) rDNA and to the mitochondrial 16S ribosomal gene (16S rDNAmt) were used to differentiate the species Lymnaea columella, L. viatrix, and L. diaphana from some localities of Brazil, Argentina, and Uruguay as well as to verify whether the molecular results corroborates the classical morphological method.PCR-RFLP analysis of the ITS1, ITS2, and 16S using 12 restriction enzymes revealed characteristic patterns for L. columella and L. diaphana which were concordant with the classical morphology. On the other hand, for L. viatrix populations a number of 1 to 6 profiles were generated while morphology provided the species pattern results.