Antibiotic discordance occurs when the causative organism demonstrates in vitro nonsusceptibility to the empiric antibiotic therapy that was administered before the urine culture results became available.
In this five-hospital study, discordant antibiotic therapy was associated with a significantly increased length of stay, Dr. Karen E. Jerardi said.
“For most of the cases of antibiotic discordance, the antibiotics were clinically appropriate in the setting of presumed [urinary tract infection], but the bacteria themselves were more resistant,” said Dr. Jerardi of Cincinnati Children's Hospital.
The implication is: Know your local uropathogen resistance patterns, and align the initial empiric antibiotic therapy accordingly, she said.
The study involved 192 patients aged 3 days to 18 years who were hospitalized for urinary tract infection (UTI), with a median 3-day length of stay.
The major uropathogens identified were Escherichia coli in 66% of cases, Klebsiella species in 11%, Enterococcus species in 6%, and Pseudomonas species in 5%. Mixed-organism UTIs accounted for 5% of the total.
The most common initial antibiotics were third-generation cephalosporins in 39% of cases, followed by ampicillin plus a third- or fourth-generation cephalosporin in 16%, and ampicillin plus gentamicin in 11%, with other agents being employed in the low single digits.
Antibiotic discordance was most frequent in UTIs caused by Klebsiella species, with a 7% rate. The other causative organisms where antibiotic discordance was common were mixed-organism infections, with a 5% antibiotic discordance rate, and E. coli and enterococcus, each with a 3% rate.
There were no significant differences between the concordant and discordant groups in terms of patient age, sex, chronic care conditions, presence of vesicoureteral reflux, or the use of prophylactic antibiotics.
In a multivariate linear regression analysis adjusted for these factors, length of stay was a median 1.8 days shorter for patients treated initially with a concordant antibiotic.
For the two-thirds of patients with an E. coli UTI, concordant antibiotic therapy was associated with a 3.1-day shorter stay, she reported at the annual meeting of the Pediatric Academic Societies in Denver.
As UTI is a common condition – accounting for 2% of all pediatric hospitalizations – selecting an initial antibiotic based on local uropathogen resistance patterns could result in significant cost savings as well as reduced exposure to unnecessary antibiotics, Dr. Jerardi observed.