The antibacterial activity of plant extracts of the Lamiaceae family was evaluated against clinical isolates of multi-resistant Gram-negative bacteria by broth microdilution technique. Promising results were obtained considering that all extracts were active for at least two bacterial species with MIC ranging from 0.5 to 2.0 mg/mL.

Infections caused by multidrug-resistant bacteria are a problem of public health, turning the search for natural products an alternative to antibiotics of great importance. The aim of this study was to investigate the in vitro antimicrobial activities of Hymenaea courbaril and Stryphnodendron adstringens against bacterial clinical isolates. The crude extracts of both vegetal species in study showed bacteriostatic activity against almost all bacteria evaluated, with minimum inhibitory concentration (MIC) ranging from 125 to 1250 µg/ml. The bacteriostatic activity was observed in all the fractions of H. courbaril and S. adstringens against at least one bacterial strain, except in the fraction dichloromethane of S. adstringens. In regard to bactericidal activity, H. courbaril was active only against E. faecalis, and S. adstringens showed activity against all bacterial strains, except to Enterococcus faecalis. The combination of extracts showed potent synergistic antimicrobial activity, with MIC values of 31.25 µg/ml against Acinetobacter baumannii, Escherichia coli and Staphylococcus aureus. S. adstringens were considered less cytotoxic compared to H. courbaril and the half-maximum cytotoxic concentration (CC 50) resulting from the combination of the two plants was 0.0082 ± 3.19 mg/ml. The results showed for the first time the synergic antibacterial activities of H. courbaril and S. adstringens against resistant bacteria, suggesting their potential use to development of new drugs.

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Agaricus brasiliensis is a medicinal mushroom native to Brazil. It was first identified as Agaricus blazei and its scientific name continues to be debated. We examined the cytology of different Brazilian commercial strains of A. brasiliensis and the nuclear behavior of strain CS1 during basidiospore development using fluorescent microscopy. All strains have multinucleate hyphae and no significant differences in nuclei numbers were observed between them. Basidia from A. brasiliensis strain CS1 are typically tetrasporics and produce binucleate basidiospores, demonstrating that a postmeiotic mitosis occurs during basidiospore development. This result suggests that A. brasiliensis is primarily a heterothallic species.

Baccharis trimera (Less.) (Asteraceae), popularly know as "carqueja", is a species commonly used in folk medicine for the treatment or prevention of diseases. In this context, the purpose of this work was to study the antibacterial activity of crude hydroalcoholic extract from Baccharis trimera against Gram-positive bacterial strains (Staphylococcus aureus ATCC 29213, Staphylococcus saprophyticus ATCC 15305, Staphylococcus epidermidis ATCC 12228, Enterococcus faecalis ATCC 19433) and Gram-negative bacteria (Escherichia coli EHEC ATCC 43895, Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae ATCC 27736, Salmonella typhi ATCC 19430) of clinical interest. Antibacterial susceptibility was evaluated by broth microdilution assay following the CLSI (formerly the NCCLS) guidelines. The extract from B. trimera showed antibacterial activity against Gram-positive bacteria and the most interesting result was obtained against S. epidermidis that presented Minimal Inhibitory Concentration of 250μg/mL. These results indicate that B. trimera have bacterisostatic potential against Gram-positive bacterial strains of medical interest and could serve as a base for further studies on the use of isolated compounds from this species as future antimicrobials.