Susceptibility of urinary pathogens in a Dublin teaching hospital.

The range and resistance patterns of organisms causing urinary tract infections (UTI) vary with time and place. A prospective study of midstream urine (MSU) specimens, received over a 3 month period, was therefore undertaken. The antibiotic sensitivities of 528 isolates from 196 domiciliary and 332 hospitalised patients with significant bacteriuria (> 10(5) organisms/ml) were determined using the modified Stokes method. Escherichia coli accounted for 79% of domiciliary isolates and 57% in hospitalised patients. Gram positive organisms causing UTI have become increasingly common and were isolated from 8% and 15% of domiciliary and hospitalised patients respectively. Resistance levels for co-amoxiclav (Augmentin) were low (7% domiciliary, 14% hospitalised). However 46 Gram negative isolates (10%) had intermediate sensitivities to co-amoxiclav on disc testing. Breakpoint testing showed 89% of these to be sensitive at the urinary breakpoint but only 52% were sensitive at the systemic breakpoint. Forty nine percent of E. coli from hospital specimens were resistant to pipercillin, due to TEM-1 beta lactamase production. A 6% resistance level to ciprofloxacin in domiciliary E. coli is considerably higher than previous reports and gives cause for concern. Gentamicin resistance was found in 4% of Gram negative hospital isolates, a finding of some significance in the empiric treatment of septicaemia of urinary tract origin.