Urinary bactericidal activity of oral antibiotics against common urinary tract pathogens in an ex vivo model.

In this investigation, the urine samples obtained in a single oral-dose pharmacokinetic study were examined for their bactericidal activity against a range of relevant urinary tract pathogens. Six healthy volunteers received a single oral dose of ten oral antibiotics available in Croatia. Urine samples were taken every 2 h during the whole dosing interval of the particular antibiotic. The urinary bactericidal activity was tested by determination of urinary bactericidal titers. All antibiotics showed a significant urinary bactericidal activity against non-extended spectrum beta-lactamase Escherichia coli and Proteus mirabilis. Fluoroquinolones displayed high and persisting levels of urinary bactericidal activity against all gram-negative bacteria and Staphylococcus saprophyticus. Average urinary bactericidal activity can be predicted from in vitro susceptibility testing, but we expect that there will be patients with a low level of urinary bactericidal activity.