1.1.1. Isolation

Most of classical and clinical microbiology depends on the isolation of a pure culture that consists of only one species. This isolate is then later used for characterization such as species determination or an antibiotic resistance profile. For many applications it is essential to isolate and maintain a pure culture of the organism of interest. The goal is to obtain isolated colonies of the organism of interest. These colonies arise from one single cell and are therefore a clone of that original cell. The original cell is called a colony-forming unit (CFU). To obtain a pure culture, it is crucial to maintain a sterile environmental.

To accomplish the microbiological analysis and isolation of strains, water samples are collected, this should be in sterile plastic containers of 500 mL. Is performed enrichment in nutrient broth, to ensure a favorable conditioning bacteria that may be stressed by environmental conditions and ensure better isolation, for which they are placed 10 mL of sterile nutrient broth sample, duplicate it.

Incubate at 37 ° C for 24 hours and reseed poured plate technique or grooves in the selected specific culture media: nutrient agar for Bacillus sp and Pseudomonas sp; agar EMB (eosin methylene blue) for Enterobacteriaceae; agar M17 for Enterococcus. Also plantings from water samples directly on agar PDA (Potato Dextrose Agar) acidifying the medium with tartaric acid for the isolation of fungi and yeast, and incubated at 22 °C [38].