Besides natural and acquired mechanisms of resistance, bacteria can cope with presence of antibiotics by using complex mechanisms such as persistence or tolerance. The main purpose of this study was to evaluate the suitability of newly developed Tolerance Disk Test (TDtest) (Gefen et al., 2017) to detect persistent or tolerant bacterial cells in clinical isolates of Staphylococcus aureus. The principle of the test is to resuscitate the subpopulation of persistent or tolerant bacterial cells following a disk diffusion test by glucose. Results of the TDtest were evaluated using time killing experiments for three pairs of consecutive S. aureus isolates from lower respiratory airway samples of three cystic fibrosis patients with chronic staphylococcal infections. TDtest enabled semi-quantitative detection of persistent or tolerant bacterial populations in all analyzed isolates for oxacillin, vancomycin, and ciprofloxacin to which isolates studied were susceptible. Therefore, TDtest is a promising method for rapidly determining persistence/tolerance in clinical isolates of S. aureus.

Department of Genetics and Microbiology Faculty of Science Charles University Albertov 6 128 00 Prague 2 Czech Republic

Department of Medical Microbiology 2nd Faculty of Medicine Charles University 5 Úvalu 84 15006 Prague 5 Czech Republic

Department of Pediatrics 2nd Faculty of Medicine Charles University 5 Úvalu 84 15006 Prague 5 Czech Republic

Department of Pneumology 2nd Faculty of Medicine Charles University and Motol University Hospital 15006 Prague 5 Prague Czech Republic

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