Catalina Rivas-Morales

Stenotrophomonas maltophilia in Mexico: antimicrobial resistance, biofilm formation and clonal diversity

Stenotrophomonas maltophilia is an important multidrug-resistant nosocomial pathogen associated with high mortality. Our aim was to examine antimicrobial susceptibility, biofilm production and clonal relatedness of clinical isolates of S. maltophilia. S. maltophilia isolates were collected between 2006 and 2013 from two tertiary care hospitals in Mexico. Antimicrobial susceptibility was evaluated by the broth microdilution method. PCR was used to determine the presence of β-lactamase genes L1 and L2. Biofilm formation was assessed with crystal violet staining. Clonal relatedness was determined by PFGE. Among the 119 collected S. maltophilia isolates, 73 (61.3%) were from the respiratory tract. Resistance levels exceeded 75% for imipenem, meropenem, ampicillin, aztreonam, gentamicin and tobramycin. Resistance to trimethoprim-sulfamethoxazole was 32.8%. L1 and L2 genes were detected in 77.1% (91/118) and 66.9% (79/118) of isolates, respectively. All S. maltophilia strains were able to produce biofilms. Strains were classified as weak (47.9%, 57/119), moderate (38.7%, 46/119), or strong (13.4%, 16/119) biofilm producers. A total of 89 distinct PFGE types were identified and 21.6% (22/102) of the isolates were distributed in nine clusters. This is the first study in Mexico to reveal characteristics of clinical isolates of S. maltophilia. Clonal diversity data indicate low cross-transmission of S. maltophilia in a hospital setting. The high antibiotic resistance underscores the need for continuous surveillance of S. maltophilia in hospital settings in Mexico.

In vitro Amoebicidal Activity of Borage (Borago officinalis) Extract on Entamoeba histolytica

Borage (Borago officinalis) is a plant with nutritional value that is also used in traditional medicine to treat gastrointestinal disease. This study investigated the amoebicidal activity of a methanol extract of borage. The 50% inhibitory concentration (IC₅₀) of the extract for Entamoeba histolytica was 33 μg/mL. The 50% lethal dose of the extract for brine shrimp was greater than 1,000 μg/mL. The IC₅₀ of the extract for Vero cells was 203.9 μg/mL. These results support the use of borage to prevent diseases associated with E. histolytica infection.

Antioxidant comparative effects of two grape pomace Mexican extracts from vineyards on erythrocytes.

Maceration and Soxhlet methods were used to obtain methanol extracts from a Mexican grape (Ruby Cabernet) pomace and the biological activity and phenolic profiles were compared. The antioxidant capacity was used to evaluate the mechanism of action, using a physiological model (erythrocytes) of damage induced by AAPH-generated free radicals. The extract obtained by maceration presented a total phenolic content twice the one obtained using the Soxhlet method. It also contained the most potent antioxidants, reducing anisotropy in the presence of AAPH to the levels of untreated cells, restoring membrane fluidity, preventing the morphological changes, as demonstrated by scanning electron microscopy (SEM), and providing protection against protein oxidation at the higher concentration. Our work showed that both extracts presented significant antioxidant activity through positive interactions with the lipid bilayer.

Miconia sp. Increases mRNA Levels of PPAR Gamma and Inhibits Alpha Amylase and Alpha Glucosidase.

Diabetes mellitus is a public health problem worldwide. For this reason, ethanolic extract of Miconia sp. from Oaxaca, Mexico, was selected in search of an alternative against this disease. The effect of Miconia sp. on mRNA expression of PPARγ on cell line 3T3-L1, its effect on alpha amylase and alpha glucosidase, lipid accumulation during adipogenesis, and cell viability on VERO cells were evaluated. The mRNA levels of PPARγ increased on 1.393 ± 0.008 folds, lipid accumulation was increased by 29.55% with Miconia sp. extract and 34.57% with rosiglitazone, and α-amylase and α-glycosidase were inhibited with IC50 values from 28.23 ± 2.15 μg/mL and 1.95 ± 0.15 μg/mL, respectively; the IC50 on antiproliferative activity on VERO cells was 314.54 ± 45.40 μg/mL. In case of α-amylase and α-glycosidase assays, IC50 (inhibitory concentration 50) refers to necessary extract amounts to inhibit 50% of enzymatic activity. On the other hand, on antiproliferative activity, IC50 (inhibitory concentration 50) refers to necessary extract amounts to inhibit 50% of cell proliferation. It was concluded that the compounds present in Miconia sp. ethanolic extract increase mRNA expression of PPARγ, inhibit α-amylase and α-glucosidase, and increase lipid accumulation. It constitutes an alternative as adjuvant in diabetes mellitus treatment; therefore, we recommend continuing identifying the compounds responsible for its promising in vivo antidiabetic activity.

Free radical scavengers from the Mexican herbal tea "poleo" (Hedeoma drummondii).

The aerial parts of the Lamiaceae Hedeoma drummondii (Benth.) are used in Mexico to prepare a herbal tea and by North American Amerindians as a spice. The methanolic extract of the aerial parts exhibited a strong antioxidant effect measured by the scavenging of the free diphenyl picrylhydrazyl (DPPH) radical. Assay-guided fractionation of the crude methanolic extract allowed the identification of three major active constituents, chlorogenic, caffeic and rosmarinic acid, as well as sideritoflavone derivatives and simple phenolics. The TEAC, FRAP, total phenolic and flavonoid content were determined. The high content of caffeic acid and rosmarinic acid relates to the antioxidant activity of H. drummondii.

In Vitro Cytotoxic Activity of Isostichopus badionotus, a Sea Cucumber from Yucatan Peninsula Coast

The in vitro cytotoxic activity of hexane, ethyl acetate and butanol extracts of the sea-cucumber Isostichopus badionotus (Holothuroidea) was tested against normal cells (Vero), human cervical carcinoma (HeLa) and breast adenocarcinoma (MCF-7 and MDA-MB-231) ATCC cells by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Hexane extracts from body walls and viscera showed high cytotoxic activity against HeLa cells (IC 50 ’s = 48.5 and 42.5 µg mL -1 , respectively), while the ethyl acetate extract of body walls was considered low active (IC 50 = 98.3 μg mL -1 ). In addition, the body walls hexane extract showed a good selectivity index value of 12.0.