Resistance of Neisseria gonorrhoeae to non-oxidative killing by adherent human polymorphonuclear leucocytes

Symptomatic infection with Neisseria gonorrhoeae (Gc) is characterized by abundant neutrophil (PMN, polymorphonuclear leucocyte) influx, but PMNs cannot clear initial infection, indicating that Gc possess defences against PMN challenge. In this study, survival of liquid-grown Gc was monitored after synchronous infection of adherent, interleukin 8-treated human PMNs. 40-70% of FA1090 Gc survived 1 h of PMN exposure, after which bacterial numbers increased. Assays with bacterial viability dyes along with soybean lectin to detect extracellular Gc revealed that a subset of both intracellular and extracellular PMN-associated Gc were viable. Gc survival was unaffected in PMNs chemically or genetically deficient for producing reactive oxygen species (ROS). This result held true even for OpaB+ Gc, which stimulate neutrophil ROS production. Catalase- and RecA-deficient Gc, which are more sensitive to ROS in vitro, had no PMN survival defect. recN and ngo1686 mutant Gc also exhibit increased sensitivity to ROS and PMNs, but survival of these mutants was not rescued in ROS-deficient cells. The ngo1686 mutant showed increased sensitivity to extracellular but not intracellular PMN killing. We conclude that Gc are remarkably resistant to PMN killing, killing occurs independently of neutrophil ROS production and Ngo1686 and RecN defend Gc from non-oxidative PMN antimicrobial factors.