O21.3 Fitness Studies onNeisseria GonorrhoeaeHarboring MosaicpenAAlleles from Ceftriaxone-Resistant Isolates Predict the Spread of Resistance to Extended-Spectrum Cephalosporins

Novel Genes Related to Ceftriaxone Resistance Found among Ceftriaxone-Resistant Neisseria gonorrhoeae Strains Selected In Vitro

The emergence of ceftriaxone-resistantNeisseria gonorrhoeaeis currently a global public health concern. However, the mechanism of ceftriaxone resistance is not yet fully understood. To investigate the potential genes related to ceftriaxone resistance inNeisseria gonorrhoeae, we subcultured six gonococcal strains with increasing concentrations of ceftriaxone and isolated the strains that became resistant. After analyzing several frequently reported genes involved in ceftriaxone resistance, we found only a single mutation inpenA(A501V). However, differential analysis of the genomes and transcriptomes between pre- and postselection strains revealed many other mutated genes as well as up- and downregulated genes. Transformation of the mutatedpenAgene into nonresistant strains increased the MIC between 2.0- and 5.3-fold, and transformation of mutatedftsXincreased the MIC between 3.3- and 13.3-fold. Genes encoding the ABC transporters FarB, Tfq, Hfq, and ExbB were overexpressed, whilepilM,pilN, andpilQwere downregulated. Furthermore, the resistant strain developed cross-resistance to penicillin and cefuroxime, had an increased biochemical metabolic rate, and presented fitness defects such as prolonged growth time and downregulated PilMNQ. In conclusion, antimicrobial pressure could result in the emergence of ceftriaxone resistance, and the evolution of resistance ofNeisseria gonorrhoeaeto ceftriaxone is a complicated process at both the pretranscriptional and posttranscriptional levels, involving several resistance mechanisms of increased efflux and decreased entry.

Summary and highlights of the scientific tracks at the STI & AIDS World Congress 2013, Vienna

The joint meeting of International Society for Sexually Transmitted Diseases Research (ISSTDR) and International Union against Sexually Transmitted Infections (IUSTI) was held in July 2013 in Vienna, Austria. The conference had attracted over 1300 submissions and was divided into six tracks. The track chairs reviewed all presentations and identified key themes and data that delegates should be aware of. In a conference summary session, each track chair presented these highlights. This conference report details and expands on this summary.