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POC Antibiotic Susceptibility Testing Evaluated in General Practice

By Labmedica International staff writers
Posted on 16 Nov 2017
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Image: The Flexicult SSI-Urinary Kit is a chromogenic agar allowing identification, quantification and susceptibility testing of Urinary Tract Infection pathogens (Photo courtesy of SSI DIagnostica).
Image: The Flexicult SSI-Urinary Kit is a chromogenic agar allowing identification, quantification and susceptibility testing of Urinary Tract Infection pathogens (Photo courtesy of SSI DIagnostica).
Urinary tract infection (UTI) is a common condition in general practice and the second leading cause for the prescribing of antibiotics. Urine culture gives a definite answer for UTI in the symptomatic patient.

However, sending urine to the microbiological laboratory for culture and susceptibility testing can delay treatment for several days. Point-of- care (POC) tests for urine culture and urine culture susceptibility testing are commercially available. They can provide a result within 24 hours, a delay to treatment, which the majority of patients would accept.

Scientists at the University of Copenhagen (Denmark) carried out an individually randomized controlled trial to investigate the effect of adding POC susceptibility testing to POC culture on appropriate use of antibiotics as well as clinical and microbiological cure for patients with suspected uncomplicated urinary tract infection (UTI) in general practice. The participants in the trial were women with suspected uncomplicated UTI, including elderly patients above 65, patients with recurrent UTI and patients with diabetes.

The participants were divided into groups and the culture-only group was tested with The ID Flexicult that is a chromogenic agar allowing identification and quantification of (1) E. coli, (2) other Enterobacteriaceae (Gram-negative rods), (3) enterococci, (4) Proteus spp., (5) Staphylococcus saphrophyticus and (6) Pseudomonas aeruginosa. The Flexicult SSI-Urinary Kit was used for the culture and susceptibility testing group. This kit consists of an agar dish consisting of a large compartment containing the same agar material as in the ID Flexicult and five small compartments, each containing agar with a specific antibiotic. Urine samples were also sent to a reference laboratory and were analyzed on Inoqul A Bi-plate with CHROMagar and blood agar with 10 μL on each half of the agar.

The team had from 20 general practices recruited 191 patients for culture and susceptibility testing and 172 for culture only. They report that 63% of the patients had UTI and 12% of these were resistant to the most commonly used antibiotic, pivmecillinam. Patients randomized to culture only received significantly more appropriate treatment (OR: 1.44). There was no significant difference in clinical or microbiological cure.

The team concluded that adding POC susceptibility testing to POC culture did not improve antibiotic prescribing for patients with suspected uncomplicated UTI in general practice. Susceptibility testing should be reserved for patients at high risk of resistance and complications. If all patients had been treated with first-line antibiotics based on clinical history and positive dipstick finding, then about 45% of patients would have been inappropriately treated compared with 29% in the study. The study was published on October 18, 2017, in the journal BMJ Open.

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