The aetiological agents of onychomycosis that we found differ from those found in other countries, suggesting that the heat and humidity of the Colombian climate could favour yeast nail infections. The lowest MICs for Candida species (obtained with voriconazole, followed by itraconazole) may be explained by emerging resistant strains. Against dermatophytes, the lowest MICs were obtained with terbinafine, followed by voriconazole. MIC values for the evaluated agents were higher for non-dermatophyte filamentous fungi than for other fungi. As MIC breakpoints have not yet been established for onychomycosis therapies, it remains unclear if in vitro activities of antifungal drugs are predictive of clinical outcome. Well-designed clinical studies are necessary to assist clinicians in choosing the best antifungal agents.

The emergence of multidrug-resistant strains of Mycobacterium tuberculosis underscores the need of continuous developments on new and efficient methods to determine the susceptibility of isolates of M. tuberculosis in the search for novel antimicrobial agents. Natural products constitute an important source of new drugs, but design and implementation of antimycobacterial susceptibility testing methods are necessary for evaluate the different extracts and compounds. A number of biological assay methodologies are in current use, ranging from the classical disk diffusion and broth dilution assay format, to radiorespirometric (BACTEC), dye-based, and fluorescent/luminescence reporter assays. This review presents an analysis on the in vitro susceptibility testing methods developed for determinate antitubercular activity in natural products and related compounds (semi-synthetic natural products and natural products-derived compounds) and the criteria to select the adequate method for determination of biological activity of new natural products.

Tuberculosis (TB) is the most ancient epidemic disease in the world and a serious opportunistic disease in HIV/AIDS patients. The increase in multidrug resistant Mycobacterium tuberculosis (MDR-TB, XDR-TB) demands the search for novel antimycobacterial drugs. Essential oils (EOs) have been widely used in medicine and some EOs and their major components have been shown to be active against M. tuberculosis. The aim of this work was to evaluate the antimycobacterial and cell toxicity activities of three EOs derived from Salvia aratocensis, Turnera diffusa and Lippia americana, aromatics plants collected in Colombia. The EOs were isolated by hydrodistillation and analyzed by GC/MS techniques. The EOs were tested against 15 Mycobacterium spp using a colorimetric macrodilution method and against mammalian Vero and THP-1 cells by MTT. The activity was expressed as minimal concentration in µg/mL that inhibits growth, and the concentration that is cytotoxic for 50 or 90% of the cells (CC 50 and CC 90). The major components were epi-α-cadinol (20.1%) and 1,10-diepi-cubenol (14.2%) for Salvia aratocensis; drima-7,9(11)-diene (22.9%) and viridiflorene (6.6%) for Turnera diffusa; and germacrene D (15.4%) and trans-β-caryophyllene (11.3%) for Lippia americana. The most active EO was obtained from S. aratocensis, with MIC values below 125 µg mL-1 for M. tuberculosis Beijing genotype strains, and 200 to 500 µg mL-1 for nontuberculous mycobacterial strains. The EOs were either partially or non toxic to Vero and THP-1 mammalian cells with CC 50 values from 30 to >100 µg mL-1 , and a CC 90 >100 µg mL-1. The EOs obtained from the three aromatic Colombian plants are an important source of potential compounds against TB. Future studies using the major EO components are recommended.

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Biofilm is a reservoir of drug resistant microorganisms that can increase the failure rate of anti-infective therapy and is a public health concern. Antibiofilm drug discovery is necessary for developing new drugs, biocides and wound management protocols. This makes the standardization and implementation of in vitro antibiofilm screening platforms a challenge in the search for new antibiotics, because current antimicrobials are active against planktonic bacteria and have poor diffusion across biofilm matrix. Usually, based in the research topic, the antibiofilm methods have been classified in static and flow depending of continuous supply of nutrients that affect the microbial growth, the final aim of these assays is obtain Minimal Biofilm Inhibitory Concentration (MBIC) and Minimal Biofilm Eradication Concentration (MBEC) values as efficacy parameter of the compound or procedure evaluated, but is very important correlates data from different models in order to give real results of activity. This review aims at describing the initial tools for to establishing an antibiofilm drug discovery-prospecting program.