Neisseria meningitidis urethritis: a case report highlighting clinical similarities to and epidemiological differences from gonococcal urethritis

Meningococcal Urethritis: Old and New

Neisseria meningitidis is a common commensal bacterium found in the respiratory tract, but it can also cause severe, invasive disease. Vaccines have been employed which have been successful in helping to prevent invasive disease caused by encapsulated N. meningitidis from the A, C, W, Y, and B serogroups. Currently, nonencapsulated N. meningitidis groups are more common commensals in the population than in the prevaccine era. One emerging nonencapsulated group of bacteria is the U.S. N. meningitidis urethritis clade (US_NmUC), which can cause meningococcal urethritis in men. US_NmUC has unique genotypic and phenotypic features that may increase its fitness in the male urethra. It is diagnostically challenging to identify and distinguish meningococcal urethritis from Neisseria gonorrhoeae, as the clinical presentation and microbiological findings are overlapping. In this review, the history of meningococcal urethritis, emergence of US_NmUC, laboratory diagnosis, and clinical treatment are all explored.

Emergence of a novel urogenital-tropic Neisseria meningitidis

PURPOSE OF REVIEW

Neisseria meningitidis (Nm) is primarily associated with asymptomatic nasopharyngeal carriage and invasive meningococcal disease (sepsis and meningitis), but like N. gonorrhoea (Ng), Nm can colonize urogenital and rectal mucosal surfaces and cause disease. First noted in 2015, but with origins in 2011, male urethritis clusters caused by a novel Nm clade were reported in the USA (the US_NmUC). This review describes research developments that characterize this urogenital-tropic Nm.

RECENT FINDINGS

The US_NmUC evolved from encapsulated Nm serogroup C strains. Loss of capsule expression, lipooligosaccharide (LOS) sialylation, genetic acquisition of gonococcal alleles (including the gonococcal anaerobic growth aniA/norB cassette), antimicrobial peptide heteroresistance and high surface expression of a unique factor-H-binding protein, can contribute to the urethra-tropic phenotype. Loss-of-function mutations in mtrC are overrepresented in clade isolates. Similar to Ng, repeat US_NmUC urethritis episodes can occur. The US_NmUC is now circulating in the UK and Southeast Asia. Genomic sequencing has defined the clade and rapid diagnostic tests are being developed for surveillance.

SUMMARY

The US_NmUC emerged as a cause of urethritis due to acquisition of gonococcal genetic determinants and phenotypic traits that facilitate urogenital tract infection. The epidemiology and pathogenesis of this urogenital-tropic pathogen continues to be defined.

Neisseria Meningitidis Urethritis in a Thai Male

Although Neisseria meningitidis (N. meningitidis) urogenital infections have been reported widely, meningococcal urethritis has not been reported previously in Thailand. A 42-year-old Thai male presented at a sexual health clinic with dysuria and urethral discharge following oral and insertive anal intercourse. N. meningitidis, serogroup C was cultured from a urethral discharge specimen and the patient was treated successfully with standard treatment for gonococcal urethritis. This case reflects a growing trend of reports describing meningococcal urethritis, likely resulting from sexual contact.

Meningococcal disease and sexual transmission: urogenital and anorectal infections and invasive disease due to Neisseria meningitidis

Neisseria meningitidis is an obligate human commensal bacterium that frequently colonises the upper respiratory tract. Person-to-person transmission occurs via direct contact or through dispersion of respiratory droplets from a carrier of the bacteria, and can lead to invasive meningococcal disease. Rare sporadic cases of meningococcal urogenital and anorectal infections, including urethritis, proctitis, and cervicitis, have been reported, typically following orogenital contact with an oropharyngeal meningococcal carrier. The resulting infections were clinically indistinguishable from infections caused by Neisseria gonorrhoeae. Over the past two decades, there have also been multiple outbreaks across North America and Europe of invasive meningococcal disease among men who have sex with men (MSM). The responsible meningococci belong to a highly virulent and predominantly serogroup C lineage, including strains that are able to express nitrite reductase and grow in anaerobic environments, such as the urogenital and anorectal tracts. More recently, a distinct clade within this lineage has expanded to cause urethritis predominantly among men who have sex with women. Evolutionary events giving rise to this clade included the loss of the ability to express a capsule, and acquisition of several gonococcal alleles, including one allele encoding a highly efficient gonococcal nitrite reductase. Members of the clade continue to acquire gonococcal alleles, including one allele associated with decreased antibiotic susceptibility. This evolution has implications for the clinical and public health management of those who are infected and their close contacts, in terms of both antibiotic treatment, and prevention through vaccination.

Atypical, Yet Not Infrequent, Infections with Neisseria Species

Neisseria species are extremely well-adapted to their mammalian hosts and they display unique phenotypes that account for their ability to thrive within niche-specific conditions. The closely related species N. gonorrhoeae and N. meningitidis are the only two species of the genus recognized as strict human pathogens, causing the sexually transmitted disease gonorrhea and meningitis and sepsis, respectively. Gonococci colonize the mucosal epithelium of the male urethra and female endo/ectocervix, whereas meningococci colonize the mucosal epithelium of the human nasopharynx. The pathophysiological host responses to gonococcal and meningococcal infection are distinct. However, medical evidence dating back to the early 1900s demonstrates that these two species can cross-colonize anatomical niches, with patients often presenting with clinically-indistinguishable infections. The remaining Neisseria species are not commonly associated with disease and are considered as commensals within the normal microbiota of the human and animal nasopharynx. Nonetheless, clinical case reports suggest that they can behave as opportunistic pathogens. In this review, we describe the diversity of the genus Neisseria in the clinical context and raise the attention of microbiologists and clinicians for more cautious approaches in the diagnosis and treatment of the many pathologies these species may cause.

[Neisseria meningitidis isolated from patients in men who have sex with men]

During the periods 2000-2004 and 2014-2015, Neisseria meningitidis was investigated in men who have sex with men, 1143 and 544 respectively, who consulted in the sexually-transmitted disease program. Prevalence, serogroup distribution and susceptibility to antibiotics were determined. Pharyngeal, rectal and urethral swabs were cultivated on selective Thayer-Martin modified medium. The identification was performed by biochemical tests and mass spectrometry by MALDI-TOF. Serogroups B, C, W and Y were investigated by PCR in 85 isolates recovered from the pharynx belonging to the second period. MICs of penicillin, ceftriaxone, rifampicin, azithromycin and ciprofloxacin were determined for 66 and 102 isolates from periods 1 and 2 respectively, according to CLSI. The prevalence of N. meningitidis was 17.8% and 28.1%, in periods 1 and 2 respectively; the isolates were mainly recovered from the pharynx. The distribution of serogroups was B 31.5%; Y 7.6%; W 3.3% and 9.8% non-capsulated and the rest would belong to other serogroups. Isolates classified as intermediate to penicillin were 34.8% and 63.7% (first and second periods, respectively); moreover, 11.8% of the isolates from the second period were resistant. All isolates were susceptible to ceftriaxone, to ciprofloxacin (except 3 isolates with MIC values between 0.25 and 0.5μg/ml), 3% were resistant to rifampicin and 2% were not susceptible to azithromicin. The prevalence of N. meningitidis carriage in men who have sex with men was high with a high rate of penicillin non-susceptible isolates. B was the prevalent serogroup.

Expansion of a urethritis-associated Neisseria meningitidis clade in the United States with concurrent acquisition of N. gonorrhoeae alleles

BACKGROUND

Increased reports of Neisseria meningitidis urethritis in multiple U.S. cities during 2015 have been attributed to the emergence of a novel clade of nongroupable N. meningitidis within the ST-11 clonal complex, the "U.S. NmNG urethritis clade". Genetic recombination with N. gonorrhoeae has been proposed to enable efficient sexual transmission by this clade. To understand the evolutionary origin and diversification of the U.S. NmNG urethritis clade, whole-genome phylogenetic analysis was performed to identify its members among the N. meningitidis strain collection from the Centers for Disease Control and Prevention, including 209 urogenital and rectal N. meningitidis isolates submitted by U.S. public health departments in eleven states starting in 2015.

RESULTS

The earliest representatives of the U.S. NmNG urethritis clade were identified from cases of invasive disease that occurred in 2013. Among 209 urogenital and rectal isolates submitted from January 2015 to September 2016, the clade accounted for 189/198 male urogenital isolates, 3/4 female urogenital isolates, and 1/7 rectal isolates. In total, members of the clade were isolated in thirteen states between 2013 and 2016, which evolved from a common ancestor that likely existed during 2011. The ancestor contained N. gonorrhoeae-like alleles in three regions of its genome, two of which may facilitate nitrite-dependent anaerobic growth during colonization of urogenital sites. Additional gonococcal-like alleles were acquired as the clade diversified. Notably, one isolate contained a sequence associated with azithromycin resistance in N. gonorrhoeae, but no other gonococcal antimicrobial resistance determinants were detected.

CONCLUSIONS

Interspecies genetic recombination contributed to the early evolution and subsequent diversification of the U.S. NmNG urethritis clade. Ongoing acquisition of N. gonorrhoeae alleles by the U.S. NmNG urethritis clade may facilitate the expansion of its ecological niche while also increasing the frequency with which it causes urethritis.

Large Cluster of Neisseria meningitidis Urethritis in Columbus, Ohio, 2015

Background

Neisseria meningitidis (Nm) is a Gram-negative diplococcus that normally colonizes the nasopharynx and rarely infects the urogenital tract. On Gram stain of urethral exudates, Nm can be misidentified as the more common sexually transmitted pathogen Neisseria gonorrhoeae.

Methods

In response to a large increase in cases of Nm urethritis identified among men presenting for screening at a sexually transmitted disease clinic in Columbus, Ohio, we investigated the epidemiologic characteristics of men with Nm urethritis and the molecular and phylogenetic characteristics of their Nm isolates. The study was conducted between 1 January and 18 November 2015.

Results

Seventy-five Nm urethritis cases were confirmed by biochemical and polymerase chain reaction testing. Men with Nm urethritis were a median age of 31 years (interquartile range [IQR] = 24-38) and had a median of 2 sex partners in the last 3 months (IQR = 1-3). Nm cases were predominantly black (81%) and heterosexual (99%). Most had urethral discharge (91%), reported oral sex with a female in the last 12 months (96%), and were treated with a ceftriaxone-based regimen (95%). A minority (15%) also had urethral chlamydia coinfection. All urethral Nm isolates were nongroupable, ST-11 clonal complex (cc11), ET-15, and clustered together phylogenetically. Urethral Nm isolates were similar by fine typing (PorA P1.5-1,10-8, PorB 2-2, FetA F3-6), except 2, which had different PorB types (2-78 and 2-52).

Conclusions

Between January and November 2015, 75 urethritis cases due to a distinct Nm clade occurred among primarily black, heterosexual men in Columbus, Ohio. Future urogenital Nm infection studies should focus on pathogenesis and modes of sexual transmission.

Notes from the Field: Increase in Neisseria meningitidis-Associated Urethritis Among Men at Two Sentinel Clinics - Columbus, Ohio, and Oakland County, Michigan, 2015

Neisseria meningitidis (Nm) urogenital infections, although less common than infections caused by Neisseria gonorrhoeae (Ng), have been associated with urethritis, cervicitis, proctitis, and pelvic inflammatory disease. Nm can appear similar to Ng on Gram stain analysis (gram-negative intracellular diplococci) (1-5). Because Nm colonizes the nasopharynx, men who receive oral sex (fellatio) can acquire urethral Nm infections (1,3,5). This report describes an increase in Nm-associated urethritis in men attending sexual health clinics in Columbus, Ohio, and Oakland County, Michigan.

Comparison between conventional culture and NAATs for the microbiological diagnosis in gonococcal infection

Gonorrhea is a public health problem. Fast diagnostics is necessary. The aim of this study was to compare the diagnostic yield of culture with that of polymerase chain reaction (PCR) in gonococcal infection. This is a study comparing the results of Neisseria gonorrhoeae detection by culture versus PCR from July to December 2012. Molecular diagnosis was performed by real-time PCR using the Versant CT/GC DNA 1.0 assay. In the 768 specimens, 96.9% the results were concordant. In 3.1%, the results were discordant, being PCR-positive and culture-negative in 21 cases and PCR-negative and culture-positive in 3. The sensitivity, specificity, positive predictive value, and negative predictive value for culture were 86.2%, 99.8%, 99.2%, and 96.7%, and for PCR, 98.7%, 100%, 100% and 99.7%, respectively. In laboratories where antimicrobial susceptibility is monitored, an effective approach would be to perform culture in addition to PCR in symptomatic patients.

A misleading urethral smear with polymorphonuclear leucocytes and intracellular diplococci; case report of urethritis caused by Neisseria meningitidis

The primary pathogens found in men with urethritis are Chlamydia trachomatis and Neisseria gonorrhoeae. Rapid diagnosis of N. gonorrhoeae infection can be made based on a Gram- or methylene blue-stained urethral smear. We describe a case of a man with purulent penile discharge, in which microscopic examination led to the presumptive diagnosis of gonorrhoea. A nucleic acid amplification test was negative for N. gonorrhoeae but positive for C. trachomatis. Culture showed Gram-negative diplococci which were identified as Neisseria meningitidis. N. meningitidis can be sporadically pathogenic in the genito-urinary tract and mimicks gonococcal urethritis, and appears identical by microscopy. When a gonococcal urethritis is suspected based on clinical signs and microscopic examination, but investigatory tests cannot confirm the diagnosis, a N. meningitidis infection should be considered.

Description of an unusual Neisseria meningitidis isolate containing and expressing Neisseria gonorrhoeae-Specific 16S rRNA gene sequences

An apparently rare Neisseria meningitidis isolate containing one copy of a Neisseria gonorrhoeae 16S rRNA gene is described herein. This isolate was identified as N. meningitidis by biochemical identification methods but generated a positive signal with Gen-Probe Aptima assays for the detection of Neisseria gonorrhoeae. Direct 16S rRNA gene sequencing of the purified isolate revealed mixed bases in signature regions that allow for discrimination between N. meningitidis and N. gonorrhoeae. The mixed bases were resolved by sequencing individually PCR-amplified single copies of the genomic 16S rRNA gene. A total of 121 discrete sequences were obtained; 92 (76%) were N. meningitidis sequences, and 29 (24%) were N. gonorrhoeae sequences. Based on the ratio of species-specific sequences, the N. meningitidis strain seems to have replaced one of its four intrinsic 16S rRNA genes with the gonococcal gene. Fluorescence in situ hybridization (FISH) probes specific for meningococcal and gonococcal rRNA were used to demonstrate the expression of the rRNA genes. Interestingly, the clinical isolate described here expresses both N. meningitidis and N. gonorrhoeae 16S rRNA genes, as shown by positive FISH signals with both probes. This explains why the probes for N. gonorrhoeae in the Gen-Probe Aptima assays cross-react with this N. meningitidis isolate. The N. meningitidis isolate described must have obtained N. gonorrhoeae-specific DNA through interspecies recombination.