Background: For the empiric therapy of urinary tract infections (UTI) in the extra-hospital setting the susceptibility patterns of potential pathogens, among some other factors, should be considered. Thus, the evolution in susceptibility, mainly influenced by the previous consume of antibiotic, can be observed when comparing with susceptibility patterns in the previous years.
Material and methods: All isolates obtained from patients with bacteriuria from 4 Health Areas in Madrid for a 3-week period were collected. The susceptibility to 4 quinolones and other 9 antibiotics was determined by the agar dilution method. The chi square test was used to compare the results obtained with Escherrichia coli isolates with those obtained with the same method in 1992.
Results: A total of 945 isolates were recovered. E. coli accounted for 71.4% of isolates; other gram-negative bacilli for 20.2% and gram-positive cocci for 8.4%. The percentages of E. coli isolates susceptible to ampicillin, cotrimoxazole, norfloxacin and ciprofloxacin, phosphomycin, cefuroxime, and cefuroxime-axetil were 40.5, 74.7, 91.6, 97.8, 98.1 and 75.9, respectively. Isolates with cefotaxime MIC higher than 0.5 mg/l were not detected. Significant differences were observed (p < 0.01) for susceptibilities recorded in 1992 and 1995 for amoxycillin/clavulanic acid, cefazolin, and the four quinolones. The antibiotics with the best in vitro activity against the remaining gram-negative bacilli were norfloxacin and ciprofloxacin (98% of susceptible isolates), gentamicin (97%) and cefotaxime (95%).
Conclusions: Changes in susceptibility results for E. coli between 1992 and 1995 have been observed. By 1995, there are commercially available antibiotics with good in vitro activity against pathogens with the potential of causing extra-hospital UTI in our setting.