Characteristics of pathogenic Neisseria spp. isolated from homosexual men

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 new Neisseria meningitidis clonal complex 11 lineage 11.2 clade as an effective urogenital pathogen

Neisseria meningitidis (Nm) clonal complex 11 (cc11) lineage is a hypervirulent pathogen responsible for outbreaks of invasive meningococcal disease, including among men who have sex with men, and is increasingly associated with urogenital infections. Recently, clusters of Nm urethritis have emerged primarily among heterosexual males in the United States. We determined that nonencapsulated meningococcal isolates from an ongoing Nm urethritis outbreak among epidemiologically unrelated men in Columbus, Ohio, are linked to increased Nm urethritis cases in multiple US cities, including Atlanta and Indianapolis, and that they form a unique clade (the US Nm urethritis clade, US_NmUC). The isolates belonged to the cc11 lineage 11.2/ET-15 with fine type of PorA P1.5-1, 10-8; FetA F3-6; PorB 2-2 and express a unique FHbp allele. A common molecular fingerprint of US_NmUC isolates was an IS1301 element in the intergenic region separating the capsule ctr-css operons and adjacent deletion of cssA/B/C and a part of csc, encoding the serogroup C capsule polymerase. This resulted in the loss of encapsulation and intrinsic lipooligosaccharide sialylation that may promote adherence to mucosal surfaces. Furthermore, we detected an IS1301-mediated inversion of an ∼20-kb sequence near the cps locus. Surprisingly, these isolates had acquired by gene conversion the complete gonococcal denitrification norB-aniA gene cassette, and strains grow well anaerobically. The cc11 US_NmUC isolates causing urethritis clusters in the United States may have adapted to a urogenital environment by loss of capsule and gene conversion of the Neisseria gonorrheae norB-aniA cassette promoting anaerobic growth.

Evolutionary Events Associated with an Outbreak of Meningococcal Disease in Men Who Have Sex with Men

Meningococci spread via respiratory droplets, whereas the closely related gonococci are transmitted sexually. Several outbreaks of invasive meningococcal disease have been reported in Europe and the United States among men who have sex with men (MSM). We recently identified an outbreak of serogroup C meningococcal disease among MSM in Germany and France. In this study, genomic and proteomic techniques were used to analyze the outbreak isolates. In addition, genetically identical urethritis isolates were recovered from France and Germany and included in the analysis. Genome sequencing revealed that the isolates from the outbreak among MSM and from urethritis cases belonged to a clade within clonal complex 11. Proteome analysis showed they expressed nitrite reductase, enabling anaerobic growth as previously described for gonococci. Invasive isolates from MSM, but not urethritis isolates, further expressed functional human factor H binding protein associated with enhanced survival in a newly developed transgenic mouse model expressing human factor H, a complement regulatory protein. In conclusion, our data suggest that urethritis and outbreak isolates followed a joint adaptation route including adaption to the urogenital tract.

Increased sensitivity of DNA amplification testing for the detection of pharyngeal gonorrhea in men who have sex with men

We compared ligase chain reaction (LCR) assay with standard culture for the detection of pharyngeal Neisseria gonorrhoeae infection in men who have sex with men (MSM) presenting at a sexually transmitted diseases clinic in San Francisco. Pharyngeal specimens were obtained from 200 MSM who reported performing fellatio during the previous 2 weeks. Confirmatory testing of discrepant specimens was conducted using N. gonorrhoeae pilin proteins. Prevalence of pharyngeal N. gonorrhoeae was 6% by culture or 11% by LCR. The sensitivity and specificity of LCR were 94.7% and 97.8%, respectively, compared with values of 47.4% and 100% for culture. Prevalence of pharyngeal N. gonorrhoeae infection, as determined by DNA amplification testing, was higher than that suggested by traditional culture. Results support the use of DNA amplification testing in the oropharynx. The high prevalence of pharyngeal N. gonorrhoeae infection among MSM suggests that routine screening should be considered in efforts to reduce the burden of gonorrhea in this population.

Anogenital non-gonococcal neisseriae: prevalence and clinical significance

Over a 13-year period non-gonococcal neisseriae (NGN) were isolated from 114 of 88,670 patients (0.13%) screened for anogenital gonorrhoea at a Genitourinary Medicine Unit. During the same period there were approximately 9000 anogenital gonococcal infections (10%). The prevalence of NGN was 0.09% (27/31,500) in women, 0.04% (20/52,800) in heterosexual men and 1.5% (67/4370) in homosexual men: the differences in prevalence between women and heterosexual men (P < 0.01) and between heterosexual patients and homosexual men (P < 0.001) are highly significant. Neisseria meningitidis was isolated most frequently and accounted for 85% (99/114) of the NGN. Whenever possible, N. meningitidis was serogrouped and its occurrence correlated with patient symptoms. Eleven of 18 heterosexual men who had meningococci isolated from their urethras had urethritis but co-existing chlamydial infection was excluded in only 5. None of 9 women with cervical colonization had clinical evidence of pelvic inflammation. Only one of 49 men with rectal colonization had proctitis. The management of anogenital NGN infection is discussed in relation to our findings and those of previously published studies. Within each patient group the prevalence and incidence of anogenital NGN were similar at the beginning and end of the study period indicating that levels have not been influenced by the advent of AIDS.

Historical perspectives and identification of Neisseria and related species

The pathogenic Neisseria spp., N. gonorrhoeae and N. meningitidis, have been studied extensively and rapid identification procedures have been designed to distinguish these species from the commensal Neisseria and related species that are normal flora of the oro- and nasopharynx. The commensal Neisseria spp. have been largely ignored except for isolated studies. It is important that we know about these species, however, because not only may some be misidentified as pathogenic species if identified with inappropriate procedures, but also they may occasionally be isolated from unusual sites and must be correctly identified to the species level for clinical purposes.

Comparison of Neisseria gonorrhoeae isolates from homosexual and heterosexual men

The gene locus known as mtr confers resistance to hydrophobic dyes, detergents, and antibiotics. It has been suggested previously that the host environment is important in the selection of gonococcal strains with this outer membrane phenotype, and thus that strains with mtr gene loci should predominate in environments high in hydrophobic molecules. Furthermore, resistance to hydrophobic molecules has been related to a sevenfold increase in a minor outer membrane protein. To test these suggestions the outer membrane phenotypes of 61 strains of Neisseria gonorrhoeae were identified using 27 rectal isolates from homosexual men and 34 urethral isolates from heterosexual men who were matched for age. The cell envelope phenotype of each strain was identified on the basis of resistance to various hydrophobic compounds. The results were compared with the protein profiles of these strains on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE); no significant correlation was found.

Relation between nutritional requirements and susceptibilities to antibiotics of strains of Neisseria gonorrhoeae from pharyngeal and anogenital sites

Auxotyping and antibiotic susceptibility testing was carried out on 100 consecutive isolates of non-penicillinase producing strains of Neisseria gonorrhoeae (non-PPNG) taken on the same occasion from throat and anogenital sites, 100 non-PPNG strains isolated from the throat only, and 100 non-PPNG strains from anogenital sites only. Non-requiring, non-requiring and phenylalanine inhibited, proline requiring, amino acid group requiring, and arginine requiring auxotypes predominated in all groups of patients. Strains of the arginine requiring type found in anogenital sites tended to have additional requirements. The auxotypes and susceptibility to antibiotics of 93 of the 100 paired cultures from the throat and anogenital sites were identical. There appeared to be a slight preponderance of moderately susceptible strains in isolates from the throat. A strong correlation was found between nutritional requirements and sensitivity to antibiotics. Auxotypes of and minimum inhibitory concentrations (MICs) for N gonorrhoeae isolated from the throat were mostly the same as the auxotypes of and MICs for strains that were circulating during the study period in Amsterdam.

Epidemiology of PPNG infections in the Netherlands: analysis by auxanographic typing and plasmid identification

We carried out auxanographic typing and plasmid identification on 1380 isolates of penicillinase producing Neisseria gonorrhoeae (PPNG) isolated in the Netherlands in 1982 and found four plasmid patterns and 24 auxotypes with noticeable local or regional variations. Among 756 strains harbouring the 3 X 2 megadalton (Mdal) resistance plasmid ("African" type), with or without the 24 Mdal transfer plasmid, 667 (88%) were non-requiring and inhibited by phenylalanine. This type was endemic in most of the cities or regions we studied. Twenty methionine requiring PPNG strains were found, all harbouring the 3.2 and 24 Mdal plasmid; virtually all of them were isolated or contracted in the region of Groningen. The predominant (443 (71%) auxotype among the 624 PPNG strains containing the 4.5 Mdal plasmid ("Asian" type) (with or without the 24 Mdal plasmid) was proline requiring. This auxotype (with the 4.5 Mdal and 24 Mdal plasmid) caused an outbreak in Amsterdam, and in Groningen replaced the local methionine requiring auxotype which had the 3.2 Mdal and 24 Mdal plasmids. Many auxotypes with the 4.5 Mdal plasmid, and requiring proline only, or proline and isoleucine, circulated in the Hague. Spread of imported strains by prostitution played an important part in the epidemiology of infection with PPNG strains.

Use of the API NeIdent system for identification of pathogenic Neisseria spp. and Branhamella catarrhalis

The API NeIdent system (Analytab Products, Plainview, N.Y.) was evaluated for identifying Neisseria spp. and Branhamella catarrhalis commonly isolated from clinical specimens. The system identified 90% of 303 Neisseria gonorrhoeae isolates, 71% of 113 Neisseria meningitidis isolates, and 63% of 16 Neisseria lactamica isolates but failed to identify any of 22 B. catarrhalis isolates. Testing of gonococcal strains of various auxotypes revealed no relationship between nutritional requirements and NeIdent profile numbers. With the Neisseria species, interpretation of the cinnamaldehyde-coupled beta-naphthylamine reactions was difficult and resulted in profile numbers not listed in the Profile Register. Positive resazurin-glucose reactions resulted in unlisted numbers for all B. catarrhalis strains. Inconsistent results were also obtained when 62 N. gonorrhoeae isolates were tested more than once on the strip. In all cases, profile variability and failure to identify these organisms were related to the beta-naphthylamide substrate tests. Expansion of the data base and modification of the substrate formulations or their interpretive criteria may increase the reliability of the NeIdent system for identifying Neisseria spp. and B. catarrhalis.