Cefpodoxime 10μg disc screening test for detection of Neisseria gonorrhoeae with mosaic PBP2 and decreased susceptibility to extended-spectrum cephalosporins for public health purposes

Antimicrobial resistance (AMR) in Neisseria gonorrhoeae remains a global public health problem. Susceptibility to first-line treatment extended-spectrum cephalosporins (ESCs) is decreasing worldwide resulting in therapeutic failures with oral ESCs. This study describes a cefpodoxime 10μg disc test for screening for gonococci containing a penA mosaic allele encoding a mosaic penicillin-binding protein 2 (PBP2) and decreased ESC susceptibility. Selected clinical gonococcal isolates (n=315), containing a high proportion of gonococci with decreased ESC susceptibility and high geographical, temporal and genetic diversity, were examined using agar dilution (n=149; cefpodoxime and ceftriaxone) and Etest (n=315; cefixime), and disc diffusion using a commercially available cefpodoxime 10μg disc (n=315). penA sequencing was performed on all isolates. The 2008 WHO gonococcal reference strains (n=8) were included as quality controls. Using a≤11mm annular radius of growth inhibition as the breakpoint for the cefpodoxime 10μg disc, all 78, with exception of one isolate (13mm), mosaic PBP2-containing isolates, which also displayed decreased susceptibility to oral ESCs, were identified. In addition, 85 non-mosaic PBP2-containing isolates (44% of which contained a PBP2 A501 alteration) had annular radii ≤11mm and raised minimal inhibitory concentrations to the ESCs. Screening for detection of mosaic PBP2-containing gonococci and decreased ESC susceptibility, most pronounced to oral ESCs, using a commercially available cefpodoxime 10μg disc was rapid, inexpensive and sensitive. This test can be used in AMR surveillance programmes for public health purposes especially in less-resourced settings. Further studies to refine this disc testing-based approach are in progress. © 2011 The Authors. APMIS © 2011 APMIS.