Urinary pathogens' resistance to common antibiotics: a retrospective analysis

The susceptibility of urinary pathogens to common antibiotics was investigated and the results analysed retrospectively using the WHONET computer program. Of 1776 urine samples (44 catheterized) processed, 510 (28.7%) urinary pathogens were isolated. Of these 510 positive cultures, 455 (89.2%) were gram-negative bacilli, 45 (8.8%) Candida species and 10 (1.9%) gram-positive cocci. Of the 44 catheterized samples, 32 (72.7%) yielded significant bacteriuria and these were mainly gram-negative bacteria (24/32). The commonest pathogen isolated was Escherichia coli (47.3%) followed by Klebsiella species (10.3%), non-fermenters other than Pseudomonas species (9%), Candida species (8.8%), Providentia species (7%), Pseudomonas species (5.6%), Citrobacter species (3.7%), Enterobacter species (3.3%) and Proteus species (2.5%). The isolation of gram-negative bacteria among inpatients and outpatients was 71.6% and 28.3%, respectively. The critical care unit, nephrourology, obstetric and gynaecology, medical and surgical wards were found to be high-risk areas constituting 58.7% of the major isolates. The highest and lowest mean resistance among gram-negative bacteria to common antibiotics was 93.5% to ampicillin and to 61% gentamicin. The mean resistance to norfloxacin, amoxy-clavulanic acid, nitrofurantoin, trimethoprim-sulfamethoxazole and cefazolin was 65%, 67%, 75.5%, 76% and 77.5%, respectively. The most resistant pathogen to common antibiotics was found to be Proteus species (resistance 80% and above). Overall susceptibility testing demonstrated decreased usefulness of common antibiotics and demonstrates a need for a re-evaluation of common antibiotics used in the therapy for urinary tract infection.