Direct Susceptibility testing of Urine samples after 6, 9 and 16 hours incubation

Khaled Ghatian, Pia Littauer, Minna Fyhn Lykke Llado

    Publikation: Konferencebidrag uden forlag/tidsskriftAbstraktForskningpeer review


    Objectives: At present, susceptibility testing of infective bacteria from urine samples, according to EUCAST, is interpretation of zones after 16 hours of incubation. Using a semi-automated sample processing, the Kiestra (BD) system, to incubate of the agar plates and digital image processing, it is possible to perform very precisely inoculation and reading times. Escherichia coli and Klebsiella pneumoniae are the major causes of urinary tract infection. We wanted to study the possibility for faster reading of E. coli and K. pneumoniae, using standard EUCAST breakpoints, directly susceptibility testing on urine samples.
    Methods: In total 675 consecutive urine samples from out-patients, were inoculated directly, according to our laboratory standard, as 10µL on each part of a bi-plate (oxoid chomogene agar and 5% horse blood-agar) and 10µL on a MH plate for resistance testing, using an Inoqula (Kiestra-BD). The plates were photographed at 6, 9 and 16 hours after incubation. As a gold standard, the susceptibility test was performed according to EUCAST, as a secondary susceptibility testing, for colonies identified on the biplates, and read after 16 hours incubation.The disks used (Oxoid, TermoFisher, UK) for susceptibility testing were mecillinam 10µg (MEL), cefpodoxime 10μg (CPD), trimethoprim 5μg (W5), amoxicillin-clavulanic acid 30μg (AMC), sulfamethizol 300μg (S3) and nitrofurantoin 100μg (F100) as were routinely used for urine susceptibility testing.
    Results: In 32% (N=215) gram-negative were identified, 205 isolated of E. coli and 10 K. pneumoniae, in quantity of ≥104cfu/mL. At the 6 hour reading, only 51.2% (111 of 215 samples) could be read, and among these, we found a 9.1% deviation for Very Major Errors (VME) and Major Errors (ME). After 9 hours, the reading was possible in 90.7% (195 of 215) samples, and the VME+ME deviation was 5.1%. The direct susceptibility testing read at 16 hours, compared to the recommended secondary susceptibility testing, could all be read, 100%, and a deviation of 3.1%, see Table 1.
    Conclusion: It was possible to do direct susceptibility testing of urine samples, and read the susceptibility pattern for E. coli and K. pneumoniae already after 9 hours incubation, in 91%, and 100% after 16 hours. Our results make it possible to qualify the choice of treatment for urinary tract infection faster, and already after 9 hours.
    StatusUdgivet - 2015
    BegivenhedECCMID Konference - Bella Center Copenhagen, København, Danmark
    Varighed: 25 apr. 201528 apr. 2015


    KonferenceECCMID Konference
    LokationBella Center Copenhagen


    • bioanalytikeruddannelsen
    • klinisk mikrobiologi


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