994. Performance of the InTrayTM GC System versus Modified Thayer-Martin Agar for Diagnosis of Urethral Gonorrhea
Session: Poster Abstract Session: Diagnostic Microbiology: Quality Improvement and Rapid Diagnostics
Friday, October 9, 2015
Room: Poster Hall
Background: Antibiotic-resistant Neisseria gonorrhoeae poses a substantial threat to STD control efforts.  Phenotypic antibiotic susceptibility testing (AST) is an essential component of the evaluation of suspected gonorrhea (GC) treatment failures and requires culture of live isolates.  However, in clinical settings, GC culture largely has been replaced by nucleic acid amplification tests (NAATs), which are recommended for GC screening and diagnosis but do not allow for AST.  Given the importance of maintaining access to GC culture in order to conduct AST, we evaluated the sensitivity of the InTray™ GC system (BioMed Diagnostics), an alternative GC culture medium with a self-contained CO2 production system and a long storage period, compared to modified Thayer-Martin (MTM) agar for GC culture in men with urethral discharge.

Methods: Adult men with urethral discharge were enrolled from February through September 2014. Urine specimens for NAAT, and urethral swabs for Gram stain, GC culture on MTM medium, and GC culture on the InTray™ GC system were obtained.  Order of specimen collection (MTM or InTray™) was alternated.  Plates were incubated at 37°C for up to 48 hours and examined for growth.  Sensitivity of the InTray™ GC system and MTM were determined, defining a true GC positive as ≥2 positive results among NAAT, Gram stain, MTM, and InTray™.  The relative performance of the MTM and InTray™ GC system was assessed with McNemar’s Test.

Results: Of 190 specimens, 112 (58.9%) were determined to be true GC positives.  Among these 112 positives, the overall sensitivity of the MTM was 97.3% and the InTray™ GC system was 87.5%.  There were 96/112 (85.7%) specimens with positively concordant results (MTM+/InTray™+).  Fifteen specimens were discordant (2 were MTM−/InTray™+ and 13 were MTM+/InTray™−).  One GC case was missed by both (MTM−/InTray™−).  MTM performed significantly better than the InTray™ GC system (p=0.007) for diagnosis of GC.

Conclusion: MTM agar had a higher sensitivity than the InTray™ GC system for the culture of GC among men with symptomatic urethral GC.  MTM agar remains the gold standard medium for GC diagnosis via culture. The InTray™ GC system is an FDA-approved option which could improve access to GC culture for clinics and public health STD programs.

Juliet Stoltey, MD, MPH1, Stephanie Cohen, MD, MPH2, Severin Gose, Dr.P.H.2, Tina Noohi, BA2 and Ina Park, MD, MS1, (1)California Department of Public Health-STD Control Branch, Richmond, CA, (2)San Francisco Department of Public Health, San Francisco, CA


J. Stoltey, BioMed Diagnostics: Investigator , Donation of test kits

S. Cohen, BioMed Diagnostics: Investigator , Donation of test kits

S. Gose, None

T. Noohi, BioMed Diagnostics: Investigator , Donation of test kits

I. Park, BioMed Diagnostics: Investigator , Donation of test kits

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