In vitro infection assay allows the assessment of the ability of different bacteria to interact with more complex eukaryotes, colonise them and persist in the organism. The evaluation of this capacity is particularly relevant in the healthcare field, where serious infections and mortality are increasing due to the ability of pathogens to colonise different pathways, such as the respiratory or gastrointestinal tract. Thus, to perform the cell infection studies, the most relevant cell lines (lung adenocarcinoma (A549), liver (HEPG2), intestine (HT29), etc.) and bacterial strains (Pseudomonas aeruginosa PAO1, Acinetobacter baumannii ATCC 17978, Staphylococcus aureus CECT 5190, Enterococcus faecium CECT 5253, etc.) will be selected, depending on the type of sample and the route of exposure.