Use of a selective medium with potassium tellurite to follow intestinal colonization of hospitalized patients by drug-resistant Enterobacteriaceae

Nosocomial infections are a relevant factor in complicating the recovery of patients interned for even minor causes. In attempt to determine their origin it is crucial to consider that their origin is of an endogenous nature. Looking for an acessible expression of intestinal colonization we analyzed fecal samples from 3 separate groups of hospital patients collected after different lenghts of time. For practical reasons one group was studied prospectively and two other groups (patients hospitalized for up to 7 days and patients hospitalized for more than 7 days) were compared to one another. We looked for the emergence of tellurite resistance among Enterobacteriaceae using a selective medium. MacConkey potassium tellurite (MCPT). The frequence of prospectively studied patients with tellurite resistant strains was significantly greater after 7 days of hospitalization. For the two other groups, patients with more than 7 days of hospitalization showed a significant increase of bacterial species and of strains with new antimicrobial resistance markers. High molecular weigth plasmids were detected in some of these strains. These data show that the MCPT medium is a useful tool for the investigation of bowel colonization in hospitalized patients by drug-resistant Enterobacteriaceae.

Use of PCR for the determination of the frequency of the deltaF508 mutation in Brasilian cistic fibrosis patients

The [Delta]F508 mutation in the cystic fibrosis (CF) gene was studied in a population of 18 Brazilian CF patients and their 17 families by use of PCR and differential hybridization with oligonucleotides. In a total of 34 chromosomes considered, 12 (35%) carried the F508 deletion, a frequency much lower than that reported in most other populations. As a consequence, CF in Brazil would be predominantly caused by mutations different from the F508 deletion

The use of ferromagnetic dacron as solid-phase in enzyme immunoassays

Ferromagnetic dacron is proposed as an alternative solid-phase for magnetic enzyme immunoassays. Human serum albumin (HSA) was covalentlyimmobilized onto ferromagnetic dacron and as enzyme immunoassay was developed using anti-HSA rabbit sera. Peroxidase, o-phenylenediamine (OPD) and hydrogen peroxide were used anti-HSA rabbit sera. Peroxidase, o-phenylenediamine (OPD) and hydrogen peroxide were used as the enzymatic label and substrates, respectively. Best results were observed when particles of 63-100 µm (diameter) and 10 µg of immobilized antigen were used. Positive reactions were detected until dilutions of1:51200 of immune sera. Its reproducibility was similar to standard ELISA. Disruption of the immunocomplexes formed and recuperation of the immobilized antigen in other immunoassays also proved to be reliable.

Use of molecular probes and PCR for detection and typing of Leishmania - a mini-review

The use of molecular tools to detect and type Leishmania species in humans, reservoirs or sandflies has been pursued using different approaches. The polymerase chain reaction provided sensitivity to case this task, since the use of hybridization procedures alone employing specifics probes is hampered due to the low detection limit. In this report, we describe the different molecular targets used in our laboratory, aiming at the detection and specific typing of these protozoa. Different kits based on hybridization assays and PCR amplification using kinetoplast and nuclear targets are described and the results obtained from their use are reported.

Transport pathways in the malaria-infected erythrocyte: characterization and their use as potential targets for chemotherapy

The intraerythrocytic malarial parasite is involved in an extremely intensive anabolic activity while it resides in its metabolically quiescent host cell. The necessary fast uptake of nutrients and the discharge of waste product, are guaranteed by parasite-induced alterations of the constitutive transporters of the host cell and the production of new parallel pathways. The membrane of the host cell thus becomes permeable to phospholipids, purine bases and nucleosides, small non-electrolytes, anions and cations. When the new pathways are quantitatively unimportant, classical inhibitors of native transporters can be used to inhibit parasite growth. Several compounds were found to effectively inhibit the new pathways and consequently, parasite growth. The pathways have also been used to introduce cytotoxic agents. The parasitophorous membrane consists of channels which are highly permeable to small solutes and display no ion selectivity. Transport of some cations and anions across the parasite membrane is rapid and insensitive to classical inhibitors, and in some cases it is mediated by specific antiporters which respond to their respective inhibitors. Macromolecules have been shown to reach the parasitophorous space through a duct contiguous with the host cell membrane, and subsequently to be endocytosed at the parasite membrane. The simultaneous presence of the parasitophorous membrane channels and the duct, however, is incompatible with experimental evidences. No specific inhibitors were found as yet that would efficiently inhibit transport through the channels or the duct.