Comparison of gene expression profiles between pansensitive and multidrug-resistant strains of Mycobacterium tuberculosis

Mycobacterium tuberculosis has developed resistance to anti-tuberculosis first-line drugs. Multidrug-resistant strains complicate the control of tuberculosis and have converted it into a worldwide public health problem. Mutational studies of target genes have tried to envisage the resistance in clinical isolates; however, detection of these mutations in some cases is not sufficient to identify drug resistance, suggesting that other mechanisms are involved. Therefore, the identification of new markers of susceptibility or resistance to first-line drugs could contribute (1) to specifically diagnose the type of M. tuberculosis strain and prescribe an appropriate therapy, and (2) to elucidate the mechanisms of resistance in multidrug-resistant strains. In order to identify specific genes related to resistance in M. tuberculosis, we compared the gene expression profiles between the pansensitive H37Rv strain and a clinical CIBIN:UMF:15:99 multidrug-resistant isolate using microarray analysis. Quantitative real-time PCR confirmed that in the clinical multidrug-resistant isolate, the esxG, esxH, rpsA, esxI, and rpmI genes were upregulated, while the lipF, groES, and narG genes were downregulated. The modified genes could be involved in the mechanisms of resistance to first-line drugs in M. tuberculosis and could contribute to increased efficiency in molecular diagnosis approaches of infections with drug-resistant strains.

Occurrence of killer yeasts in isolates of clinical origin

A total of 1 025 strains belonging to different Candida species of clinical origin were evaluated for their killer activity against sensitive strains of Saccharomyces cerevisiae. Isolates were identified by standard morphological and biochemical analyses. For the evaluation of the killer activity, potential killer isolates were streaked on plates previously seeded with the sensitive strain. A total of 52 Candida isolates (5%) exhibited killer activity against both sensitive yeast strains. The occurrence of the killer phenomenon was proportionally higher in isolates recovered from closed cavities. Candida glabrata was the species with the most occurrences of killer strains, but a bigger proportion of killer activity was observed in Candida utilis. Secretion of killer toxins could represent at least partially, an advantage against other candida and non-Candida strains in the colonization process, especially for uncommon Candida species.

Entamoeba histolytica: cyst-like structures in vitro induction

The cyst of Entamoeba histolytica is responsible for amebiasis infection. However, no axenic in vitro system exists that promotes mass encystation for studying this process of this human-infecting parasite. Cyst-like structures of E. histolytica obtained in this work were induced using TYI-S-33 media in combination with enterobacterias Escherichia coli and Enterococcus faecalis conditioned media, high CO2 tension and histamine. Cyst-like structures showed the same characteristics of a typical E. histolytica cyst: aggregation, resistance to 0.15% sarcosyl for 10 min, high signal of fluorescence under UV light when stained with 10% calcofluor M2r and the surface topology showed a wrinkled wall. In addition these structures are multinucleated with condensed chromatin attached to nuclear membrane, contain big vacuoles and ribonucleoproteic helices in the cytoplasm and also present a thin cell wall. Last all characteristics are all the same as a typical of E. histolytica cyst.

Entamoeba invadens: in vitro axenic encystation with a serum substitute

The current media for axenic cultivation of Entamoeba histolytica and Entamoeba invadens are supplemented with bovine or equine serum, which provides several essential nutrients to amoebas. Serum has also been considered an essential component in encystation media for E. invadens. A substitute of serum, PACSR has been described as an alternative for growth of E. histolytica and also maintains growth of E. invadens. When PACSR was used instead of serum for encystation of E. invadens the efficiency was the same as for serum. Our present data show that PACSR can support the growth and induction of encystation of E. invadens strain IP-1.