BACKGROUND: In the rather rare urinary pathogen Proteus mirabilis resistance to antibiotics and ability to form biofilm were studied. MATERIAL AND METHODS: The strains Proteus mirabilis were isolated from urine samples from ambulatory and hospitalized patients diagnosed with urinary tract infection (UTI) between April 2008 and April 2010. Resistance to antibiotics was investigated using a disk diffusion antimicrobial susceptibility test. Biofilm formation was demonstrated by modified Christensen method. RESULTS: Two hundred and thirteen of P. mirabilis strains were tested. Eighty-two (38.5 %) strains were resistant to ampicillin, 49 (23.0 %) to cefalotin, 83 (39.0 %) to sulfamethoxazole/trimetoprim, 75 (35.2 %) to ciprofloxacin, 95 (44.6 %) to oxolinic acid, 54 (25.4 %) to gentamicin, and 72 (33.8 %) to chloramphenicol. There was significantly lower resistance to cefotaxime - 8 strains (3.8 %), ceftazidime - 8 (3.8 %), amoxicillin/clavulanic acid 17 (8.0 %) and aztreonam - 8 (3.8 %). No resistance to imipenem as well as to meropenem was found. Eight P. mirabilis strains were found to produce extended-spectrum beta-lactamase (ESBL). From the total of 213 strains tested, 28 (13.1 %) were able to form a biofilm. CONCLUSIONS: P. mirabilis was found to be more frequent in urine of men and older patients. Biofilm formation in urinary P. mirabilis strains was relatively low. The strains showed higher resistance to beta-lactams and quinolones; in the other cases, resistance was low.

Microbiological Department Masaryk University St Anne's University Hospital Brno Czech Republic