Historically, animal modeling of gonorrhea has been hampered by the exclusive adaptation of Neisseria gonorrhoeae to humans. Genital tract infection can be established in female mice that are treated with 17β-estradiol, however, and many features of experimental murine infection mimic human infection. Here we review the colonization kinetics and host response to experimental murine gonococcal infection, including mouse strain differences and evidence that IL-17 responses, toll-like receptor 4, and T regulatory cells play a role in infection. We also discuss the strengths and limitations of the mouse system and the potential of transgenic mice to circumvent host restrictions. Additionally, we review studies with genetically defined mutants that demonstrated a role for sialyltransferase and the MtrC–MtrD–MtrE active efflux pump in evading innate defenses in vivo, but not for factors hypothesized to protect against the phagocytic respiratory burst and H2O2-producing lactobacilli. Studies using estradiol-treated mice have also revealed the existence of non-host-restricted iron sources in the female genital tract and the influence of hormonal factors on colonization kinetics and selection for opacity (Opa) protein expression. Recent work by others with estradiol-treated mice that are transgenic for human carcinoembryonic adhesion molecules (CEACAMs) supports a role for Opa proteins in enhancing cellular attachment and thus reduced shedding of N. gonorrhoeae. Finally we discuss the use of the mouse model in product testing and a recently developed gonorrhea chlamydia coinfection model.

Background. Quinolone-resistant Neisseria gonorrhoeae (QRNG) arise from mutations in gyrA (intermediate resistance) or gyrA and parC (resistance). Here we tested the consequence of commonly isolated gyrA 91/95 and parC 86 mutations on gonococcal fitness.Methods. Mutant gyrA 91/95 and parC 86 alleles were introduced into wild-type gonococci or an isogenic mutant that is resistant to macrolides due to an mtrR −79 mutation. Wild-type and mutant bacteria were compared for growth in vitro and in competitive murine infection.Results. In vitro growth was reduced with increasing numbers of mutations. Interestingly, the gyrA 91/95 mutation conferred an in vivo fitness benefit to wild-type and mtrR −79 mutant gonococci. The gyrA 91/95 , parC 86 mutant, in contrast, showed a slight fitness defect in vivo, and the gyrA 91/95 , parC 86 , mtrR −79 mutant was markedly less fit relative to the parent strains. A ciprofloxacin-resistant (Cip R ) mutant was selected during infection with the gyrA 91/95 , parC 86 , mtrR −79 mutant in which the mtrR −79 mutation was repaired and the gyrA 91 mutation was altered. This in vivo-selected mutant grew as well as the wild-type strain in vitro.Conclusions. gyrA 91/95 mutations may contribute to the spread of QRNG. Further acquisition of a parC 86 mutation abrogates this fitness advantage; however, compensatory mutations can occur that restore in vivo fitness and maintain Cip R .Neisseria gonorrhoeae is a Gram-negative diplococcus that plays a major role in urogenital tract and perinatal infections [1]. Gonorrhea is the second most frequently reported bacterial sexually transmitted infection (STI) in the United States, with an estimated 700 000 new cases each year. The rate of gonorrhea is

Phosphoethanolamine (PEA) on Neisseria gonorrhoeae lipid A influences gonococcal inflammatory signaling and susceptibility to innate host defenses in in vitro models. Here, we evaluated the role of PEA-decorated gonococcal lipid A in competitive infections in female mice and in male volunteers. We inoculated mice and men with mixtures of wild-type N. gonorrhoeae and an isogenic mutant that lacks the PEA transferase, LptA. LptA production conferred a marked survival advantage for wild-type gonococci in the murine female genital tract and in the human male urethra. Our studies translate results from test tube to animal model and into the human host and demonstrate the utility of the mouse model for studies of virulence factors of the human-specific pathogen N. gonorrhoeae that interact with non-host-restricted elements of innate immunity. These results validate the use of gonococcal LptA as a potential target for development of novel immunoprophylactic strategies or antimicrobial treatments.IMPORTANCE Gonorrhea is one of the most common bacterial sexually transmitted infections, and increasing antibiotic resistance threatens the use of currently available antimicrobial therapies. In this work, encompassing in vitro studies and in vivo studies of animal and human models of experimental genital tract infection, we document the importance of lipid A’s structure, mediated by a single bacterial enzyme, LptA, in enhancing the fitness of Neisseria gonorrhoeae. The results of these studies suggest that novel agents targeting LptA may offer urgently needed prevention or treatment strategies for gonorrhea.

eThe induction of an intense inflammatory response by Neisseria gonorrhoeae and the persistence of this pathogen in the presence of innate effectors is a fascinating aspect of gonorrhea. Phosphoethanolamine (PEA) decoration of lipid A increases gonococcal resistance to complement-mediated bacteriolysis and cationic antimicrobial peptides (CAMPs), and recently we reported that wild-type N. gonorrhoeae strain FA1090 has a survival advantage relative to a PEA transferase A (lptA) mutant in the human urethral-challenge and murine lower genital tract infection models. Here we tested the immunostimulatory role of this lipid A modification. Purified lipooligosaccharide (LOS) containing lipid A devoid of the PEA modification and an lptA mutant of strain FA19 induced significantly lower levels of NF-B in human embryonic kidney Toll-like receptor 4 (TLR4) cells and murine embryonic fibroblasts than wild-type LOS of the parent strain. Moreover, vaginal proinflammatory cytokines and chemokines were not elevated in female mice infected with the isogenic lptA mutant, in contrast to mice infected with the wild-type and complemented lptA mutant bacteria. We also demonstrated that lptA mutant bacteria were more susceptible to human and murine cathelicidins due to increased binding by these peptides and that the differential induction of NF-B by wild-type and unmodified lipid A was more pronounced in the presence of CAMPs. This work demonstrates that PEA decoration of lipid A plays both protective and immunostimulatory roles and that host-derived CAMPs may further reduce the capacity of PEA-deficient lipid A to interact with TLR4 during infection.

H2O2-producing commensal lactobacilli inhibit N. gonorrhoeae in vitro and clinical data suggest they are associated with reduced risk of gonorrhea. Here we pre-colonized mice with Lactobacillus crispatus and then challenged them with N. gonorrhoeae to measure the effects of H2O2-producing lactobacilli on gonococcal infection. We found no difference in the duration of infection or number of gonococci recovered from untreated mice and mice colonized with L. crispatus. A gonococcal catalase mutant and a catalase, cytochrome C peroxidase mutant exhibited greater susceptibility to L. crispatus in vitro than wild type bacteria; however, recovery of these mutants from mice was not affected by L. crispatus. We also found no evidence that utilization of lactobacillus-produced lactate by N. gonorrhoeae balances the detrimental effects of H2O2 during infection. We conclude the relationship between lactobacilli and gonococci is complex and may be subject to factors that have not been reproduced in vitro.