Characterization of Neisseria cinerea, a nonpathogenic species isolated on Martin-Lewis medium selective for pathogenic Neisseria spp

Beyond the usual suspects: Reviewing infections caused by typically-commensal Neisseria species

OBJECTIVE

Few data outside of individual case reports are available on non-meningococcal, non-gonococcal species of Neisseria as causative agents of invasive disease. This review collates disease, organism and patient information from case reports on the topic.

METHODS

A literature search was performed examining articles describing diseases caused by non-meningococcal and non-gonococcal Neisseria.

FINDINGS

Neisseria present as opportunistic pathogens causing a wide variety of diseases including serious presentations, endocarditis being the most common condition described and N. mucosa the most commonly presenting pathogen overall. Disease may occur in otherwise healthy patients, although risk factors for infection include recent surgery, an immunocompromised state, poor oral health, and intravenous drug use.

CONCLUSIONS

Commensal Neisseria infections are rare but can present serious invasive diseases. Further research is required to determine why some species cause disease more than others or why some are inclined towards particular manifestations.

Recurrent Neisseria cinerea bacteremia secondary to cardiovascular implantable electronic device infection

We present the first case of cardiac implantable electronic device (CIED) infection due to Neisseria cinerea in a 64-year-old woman from Panama. She had a history of splenectomy, aortic valve stenosis requiring transcatheter aortic valve replacement (TAVR), and permanent pacemaker placement. She presented with relapsing N. cinerea bacteremia over a 3-month period. Transesophageal echocardiography revealed a lead vegetation in the superior vena cava. She was successfully treated with pacemaker removal and 2 weeks of IV antibiotic therapy. N. cinerea is an aerobic gram-negative commensal diplococcus typically found in the human nasopharynx. Infection in humans is rare with few case reports in the literature.

Type VI secretion system killing by commensal Neisseria is influenced by expression of type four pili

Type VI Secretion Systems (T6SSs) are widespread in bacteria and can dictate the development and organisation of polymicrobial ecosystems by mediating contact dependent killing. In Neisseria species, including Neisseria cinerea a commensal of the human respiratory tract, interbacterial contacts are mediated by Type four pili (Tfp) which promote formation of aggregates and govern the spatial dynamics of growing Neisseria microcolonies. Here, we show that N. cinerea expresses a plasmid-encoded T6SS that is active and can limit growth of related pathogens. We explored the impact of Tfp on N. cinerea T6SS-dependent killing within a colony and show that pilus expression by a prey strain enhances susceptibility to T6SS compared to a non-piliated prey, by preventing segregation from a T6SS-wielding attacker. Our findings have important implications for understanding how spatial constraints during contact-dependent antagonism can shape the evolution of microbial communities.

Colistin Sensitivity and Factor H-Binding Protein Expression among Commensal Neisseria Species

Many bacterial carriage studies utilize colistin-containing media to select for Neisseria meningitidis among the diverse human pharyngeal milieu. These studies commonly report the isolation of Neisseria commensal species, with carriage rates of around 1% or less typically observed. Here, we describe the isolation of N. cinerea and N. polysaccharea from pharyngeal swabs using nonselective agar and confirm they are unable to grow on colistin-containing media. We also demonstrated colistin sensitivity among archived Neisseria commensal strains, including N. cinerea, N. polysaccharea, N. mucosa, and N. subflava. The distribution of lptA among these strains indicated that, while the phosphoethanolamine (PEA) transferase encoded by this gene confers colistin resistance, other mechanisms may lead to reduced susceptibility in some lptA-deficient strains. The majority of the N. cinerea and N. polysaccharea isolates expressed medium to very high levels of factor H-binding protein (fHbp), an important meningococcal vaccine antigen. Sequence analysis showed that the commensal fHbp peptide variants were similar in sequence to fHbp variants typically observed among invasive meningococci. Altogether, these results not only suggest that Neisseria commensal strains could be carried at much higher rates than previously reported but also raise questions about the impact of protein-based meningococcal vaccines on these unencapsulated commensals. IMPORTANCE This study highlights the need for further work to accurately determine the pharyngeal carriage prevalence of Neisseria commensal bacteria (e.g., N. cinerea and N. polysaccharea) among the general population. Previous studies have clearly demonstrated the suppressive effect these commensal species can have on meningococcal colonization, and so the carriage prevalence of these species could be an important factor in the spread of meningococci through the population. Furthermore, the surface expression of the meningococcal vaccine antigen factor H-binding protein by many of these commensal strains could have important implications for the use of fHbp-containing vaccines. Carriage of these commensal species may influence the immune response to these vaccines, or conversely, the immune response elicited by vaccination may induce clearance of these potentially important members of the pharyngeal niche.

Neisseria Cinerea Bacteremia Secondary to a Retropharyngeal Abscess

Neisseria cinerea is a commensal bacteria of the human oropharynx, not thought to be pathogenic, and is rarely associated with serious infections, including bacteremia. Case reports involving invasive N. cinerea infections are uncommon in the literature. Retropharyngeal abscesses are unusual in adults, and are usually attributable to local trauma.Based on a review of the literature, Neisseria cinerea bacteremia secondary to a retropharyngeal abscess has not been described. We present a unique case of an elderly female without clear predisposing factors for a retropharyngeal abscess, who presented with a N. cinerea bacteremia and was found to have an asymptomatic retropharyngeal abscess.

Neisseria species and their complicated relationships with human health

Neisseria spp. are a transient low abundance member of the human microbiome. This species contains the very well described pathogens, Neisseria gonorrhoeae and N. meningitidis. Recent advances in molecular typing have revealed that this genus is more diverse than previously thought and that commensal species may have important roles in inhibiting the growth the pathogens. This short review summates these new findings and examines the evidence that the relatively under-reported Neisseria commensal species maybe beneficial to human health.

Mannheimia haemolytica IgA-specific proteases

Mannheimia haemolytica colonizes the nasopharynx of cattle and can cause severe fibrinous pleuropneumonia. IgA proteases are metalloendopeptidases released by bacteria that cleave IgA, enhancing colonization of mucosa. The objectives of these studies were to characterize M. haemolytica IgA1 and IgA2 proteases in vitro and in silico, to clone and sequence the genes for these proteases, and to demonstrate immunogenicity of components of the entire IgA protease molecule. Both IgA protease genes were cloned, expressed, and sequenced. Sequences were compared to other published sequences. Components were used to immunize mice to determine immunogenicity. Sera from healthy cattle and cattle that recovered from respiratory disease were examined for antibodies to IgA proteases. In order to assay the cleavage of bovine IgA with IgA1 protease, M. haemolytica culture supernatant was incubated with bovine IgA. Culture supernatant cleaved purified bovine IgA in the presence of ZnCl₂. Both IgA proteases contain three domains, 1) IgA peptidase, 2) PL1_Passenger_AT and 3) autotransporter. IgA1 and IgA2 peptidases have molecular weights of 96.5 and 87 kDa, respectively. Convalescent bovine sera with naturally high anti-M. haemolytica antibody titers had high antibodies against all IgA1 & IgA2 protease components. Mouse immunizations indicated high antibodies to the IgA peptidases and autotransporters but not to PL1_Passenger_AT. These data indicate that M. haemolytica produces two IgA proteases that are immunogenic, can cleave bovine IgA, and are produced in vivo, as evidenced by antibodies in convalescent bovine sera. Further studies could focus on IgA protease importance in pathogenesis and immunity.

Neisseria cinerea in a Post-splenectomy Patient: A Rare Potentially Fatal Bacteremia

Neisseria cinerea is a commensal which usually resides in the human respiratory tract. Very rarely, the organism finds its way into the bloodstream causing severe bacteremia. So far, very few cases of Neisseria bacteremia have been reported. We report a case of a 78-year-old male, post-splenectomy, who presented with high fever, cough and shortness of breath. The patient was initially managed for septic shock with fluid resuscitations, vasopressors and broad-spectrum antibiotics. Later, the blood cultures grew gram-negative coccobacilli, Neisseria cinerea. The patient was successfully treated with intravenous ceftriaxone. This is the first case ever of Neisseria cinerea bacteremia in a post-splenectomy patient and ninth case overall. This case illustrates that the physicians should maintain heightened awareness for Neisseria cinerea bacteremia in post-splenectomy patients.

Non-typeable Haemophilus influenzae protects human airway epithelial cells from a subsequent respiratory syncytial virus challenge

Respiratory syncytial virus (RSV) and the common commensal and opportunistic pathogen, non-typeable Haemophilus influenzae (NTHi) both serve as a frequent cause of respiratory infection in children. Although it is well established that some respiratory viruses can increase host susceptibility to secondary bacterial infections, few studies have examined how commensal bacteria could influence a secondary viral response. Here, we examined the impact of NTHi exposure on a subsequent RSV infection of human bronchial epithelial cells (16HBE14o-). Co-culture of 16HBE14o- cells with NTHi resulted in inhibition of viral gene expression following RSV infection. 16HBE14o- cells co-cultured with heat-killed NTHi failed to protect against an RSV infection, indicating that protection requires live bacteria. However, NTHi did not inhibit influenza A virus replication, indicating that NTHi-mediated protection was RSV-specific. Our data demonstrates that prior exposure to a commensal bacterium such as NTHi can elicit protection against a subsequent RSV infection.

Uncovering oral Neisseria tropism and persistence using metagenomic sequencing

Microbial epidemiology and population genomics have previously been carried out near-exclusively for organisms grown in vitro. Metagenomics helps to overcome this limitation, but it is still challenging to achieve strain-level characterization of microorganisms from culture-independent data with sufficient resolution for epidemiological modelling. Here, we have developed multiple complementary approaches that can be combined to profile and track individual microbial strains. To specifically profile highly recombinant neisseriae from oral metagenomes, we integrated four metagenomic analysis techniques: single nucleotide polymorphisms in the clade's core genome, DNA uptake sequence signatures, metagenomic multilocus sequence typing and strain-specific marker genes. We applied these tools to 520 oral metagenomes from the Human Microbiome Project, finding evidence of site tropism and temporal intra-subject strain retention. Although the opportunistic pathogen Neisseria meningitidis is enriched for colonization in the throat, N. flavescens and N. subflava populate the tongue dorsum, and N. sicca, N. mucosa and N. elongata the gingival plaque. The buccal mucosa appeared as an intermediate ecological niche between the plaque and the tongue. The resulting approaches to metagenomic strain profiling are generalizable and can be extended to other organisms and microbiomes across environments.

Meningitis and Bacteremia Due to Neisseria cinerea following a Percutaneous Rhizotomy of the Trigeminal Ganglion

Neisseria cinerea is a human commensal. The first known case of meningitis and bacteremia due to Neisseria cinerea following percutaneous glycerol instillation of the trigeminal ganglion is reported. Conventional phenotypic methods and complete 16S RNA gene sequencing accurately identified the pathogen. Difficulties in differentiation from pathogenic neisseriae are discussed.

Evaluation of the New BD Max GC Real-Time PCR Assay, Analytically and Clinically as a Supplementary Test for the BD ProbeTec GC Qx Amplified DNA Assay, for Molecular Detection of Neisseria gonorrhoeae

The new BD Max GC real-time PCR assay showed high clinical and analytical sensitivity and specificity. It can be an effective and accurate supplementary test for the BD ProbeTec GC Qx amplified DNA assay, which had suboptimal specificity, and might also be used for initial detection of Neisseria gonorrhoeae.

Fatal bacteremia by neisseria cinerea in a woman with myelodysplastic syndrome: a case report

Neisseria cinerea has been rarely found in blood cultures. In this study, we are reporting a case of a Myelodysplastic Syndrome (MDS) patient in whose blood Neisseria cinerea was found and led a fatal consequence. This case will call our attentions to the uncommon pathogens in the pathogenicity of end-stage patients.

Non-pathogenic Neisseria: members of an abundant, multi-habitat, diverse genus

The genus Neisseria contains the important pathogens Neisseria meningitidis and Neisseria gonorrhoeae. These Gram-negative coccoid bacteria are generally thought to be restricted to humans and inhabit mucosal surfaces in the upper respiratory and genito-urinary tracts. While the meningococcus and gonococcus have been widely studied, far less attention has been paid to other Neisseria species. Here we review current knowledge of the distribution of commensal Neisseria in humans and other hosts. Analysis of the microbiome has revealed that Neisseria is an abundant member of the oropharyngeal flora, and we review its potential impact on health and disease. Neisseria also exhibit remarkable diversity, exhibiting both coccoid and rod-shaped morphologies, as well as environmental strains which are capable of degrading complex organic molecules.

Identifying Neisseria species by use of the 50S ribosomal protein L6 (rplF) gene

The comparison of 16S rRNA gene sequences is widely used to differentiate bacteria; however, this gene can lack resolution among closely related but distinct members of the same genus. This is a problem in clinical situations in those genera, such as Neisseria, where some species are associated with disease while others are not. Here, we identified and validated an alternative genetic target common to all Neisseria species which can be readily sequenced to provide an assay that rapidly and accurately discriminates among members of the genus. Ribosomal multilocus sequence typing (rMLST) using ribosomal protein genes has been shown to unambiguously identify these bacteria. The PubMLST Neisseria database (http://pubmlst.org/neisseria/) was queried to extract the 53 ribosomal protein gene sequences from 44 genomes from diverse species. Phylogenies reconstructed from these genes were examined, and a single 413-bp fragment of the 50S ribosomal protein L6 (rplF) gene was identified which produced a phylogeny that was congruent with the phylogeny reconstructed from concatenated ribosomal protein genes. Primers that enabled the amplification and direct sequencing of the rplF gene fragment were designed to validate the assay in vitro and in silico. Allele sequences were defined for the gene fragment, associated with particular species names, and stored on the PubMLST Neisseria database, providing a curated electronic resource. This approach provides an alternative to 16S rRNA gene sequencing, which can be readily replicated for other organisms for which more resolution is required, and it has potential applications in high-resolution metagenomic studies.

Neisseria gonorrhoeae activates the proteinase cathepsin B to mediate the signaling activities of the NLRP3 and ASC-containing inflammasome

Neisseria gonorrhoeae is a common sexually transmitted pathogen that significantly impacts female fertility, neonatal health, and transmission of HIV worldwide. N. gonorrhoeae usually causes localized inflammation of the urethra and cervix by inducing production of IL-1beta and other inflammatory cytokines. Several NLR (nucleotide-binding domain, leucine-rich repeat) proteins are implicated in the formation of pro-IL-1beta-processing complexes called inflammasomes in response to pathogens. We demonstrate that NLRP3 (cryopyrin, NALP3) is the primary NLR required for IL-1beta/IL-18 secretion in response to N. gonorrhoeae in monocytes. We also show that N. gonorrhoeae infection promotes NLRP3-dependent monocytic cell death via pyronecrosis, a recently described pathway with morphological features of necrosis, including release of the strong inflammatory mediator HMBG1. Additionally, N. gonorrhoeae activates the cysteine protease cathepsin B as measured by the breakdown of a cathepsin B substrate. Inhibition of cathepsin B shows that this protease is an apical controlling step in the downstream activities of NLRP3 including IL-1beta production, pyronecrosis, and HMGB1 release. Nonpathogenic Neisseria strains (Neisseria cinerea and Neisseria flavescens) do not activate NLRP3 as robustly as N. gonorrhoeae. Conditioned medium from N. gonorrhoeae contains factors capable of initiating the NLRP3-mediated signaling events. Isolated N. gonorrhoeae lipooligosaccharide, a known virulence factor from this bacterium that is elaborated from the bacterium in the form of outer membrane blebs, activates both NLRP3-induced IL-1beta secretion and pyronecrosis. Our findings indicate that activation of NLRP3-mediated inflammatory response pathways is an important venue associated with host response and pathogenesis of N. gonorrhoeae.

Chloramphenicol is a substrate for a novel nitroreductase pathway in Haemophilus influenzae

The p-nitroaromatic antibiotic chloramphenicol has been used extensively to treat life-threatening infections due to Haemophilus influenzae and Neisseria meningitidis; its mechanism of action is the inhibition of protein synthesis. We found that during incubation with H. influenzae cells and lysates, chloramphenicol is converted to a 4-aminophenyl allylic alcohol that lacks antibacterial activity. The allylic alcohol moiety undergoes facile re-addition of water to restore the 1,3-diol, as well as further dehydration driven by the aromatic amine to form the iminoquinone. Several Neisseria species and most chloramphenicol-susceptible Haemophilus species, but not Escherichia coli or other gram-negative or gram-positive bacteria we examined, were also found to metabolize chloramphenicol. The products of chloramphenicol metabolism by species other than H. influenzae have not yet been characterized. The strains reducing the antibiotic were chloramphenicol susceptible, indicating that the pathway does not appear to mediate chloramphenicol resistance. The role of this novel nitroreductase pathway in the physiology of H. influenzae and Neisseria species is unknown. Further understanding of the H. influenzae chloramphenicol reduction pathway will contribute to our knowledge of the diversity of prokaryotic nitroreductase mechanisms.

The prevalence of proline iminopeptidase negative Neisseria gonorrhoeae throughout England and Wales

BACKGROUND

The accurate laboratory identification of Neisseria gonorrhoeae is an essential element of the diagnosis of gonorrhoea and is particularly important for medicolegal cases. The detection of proline iminopeptidase (Pip) activity is widely used as a marker for gonococci, although Pip negative N gonorrhoeae isolates have been shown to generate false negative identifications when using biochemical kits. This study aimed to determine the frequency of Pip negative gonococci in England and Wales.

METHODS

A total of 2055 isolates were collected from consecutive patients attending 26 genitourinary medicine centres as part of the Gonococcal Resistance to Antimicrobials Surveillance Programme (GRASP). Upon receipt the identity of all isolates was confirmed using N gonorrhoeae specific monoclonal antibodies and the Pip status was determined using the Gonochek II kit.

RESULTS

The overall prevalence of Pip negative isolates was found to be 4.33%. Significant geographical variation was observed between isolates from centres outside London (p< or =0.001). Variation was also observed within London between the nine different clinics submitting isolates (p = 0.025). There was also a higher frequency of these isolates among men who have sex with men (p< or =0.001), which may account for geographical variations.

CONCLUSION

Pip negative N gonorrhoeae isolates are a very serious cause for concern as currently all biochemical test kits available within the United Kingdom require the presence of the Pip enzyme for an unambiguous identification of this pathogen. Raising awareness of the current prevalence of Pip negative N gonorrhoeae isolates is critical for the successful control of gonorrhoea.

Evaluation of commercial kits for the identification of Neisseria gonorrhoeae

Eight identification methods were evaluated against 100 isolates of Neisseria gonorrhoeae and 21 non-gonococcal Neisseria strains. The methods examined included four commercial biochemical kits, API NH, RapID NH, Gonochek II and Neisseria Preformed Enzyme Test (PET), three immunological kits, Phadebact Monoclonal GC test, GonoGen II and MicroTrak, and one in-house carbohydrate-utilization method, cystine trypticase agar (CTA) sugars. The percentage of isolates unambiguously identified as N. gonorrhoeae by each of the methods was as follows: API NH, 66 %; RapID NH, 64 %; GonoChek II, 66 %; Neisseria PET, 66 %; Phadebact Monoclonal GC OMNI test, 99 %; GonoGen II, 100 %; MicroTrak, 100 %; and CTA sugars, 96 %. The low sensitivity of the biochemical kits for the identification of N. gonorrhoeae was due to a lack of the enzyme proline iminopeptidase (Pip) in 34 % of the isolates examined. All the biochemical kits utilized the presence of this enzyme as a marker for N. gonorrhoeae. The Phadebact Monoclonal GC kit, GonoGen II, MicroTrak, CTA sugars and the API NH kit all exhibited high specificity, but non-gonococcal Neisseria were misidentified as N. gonorrhoeae using RapID NH (two strains), Gonochek II (11 strains) and Neisseria PET (11 strains). Whilst the isolates examined in this study may not be truly representative, they do indicate that N. gonorrhoeae isolates lacking the enzyme Pip can give anomalous results when using commercially available biochemical tests and that some non-pathogenic Neisseria species are still being misidentified using some biochemical kits. This further reinforces the recommendation that any dubious biochemical result should be confirmed with an immunological test.

[Bacterial conjunctivitis: most prevalent pathogens and their antibiotic sensitivity]

INTRODUCTION

Bacterial conjunctivitis is a self-limiting process, but topical antibiotic treatment is recommended to eradicate the pathogen and reduce symptom duration. Since this treatment is usually empirical and prior cultures are not normally taken, the etiological agents involved in the process are unknown.

PATIENTS AND METHODS

A total of 596 conjunctival exudates from pediatric outpatients with a diagnosis of acute conjunctivitis in Medical Area 6 of Madrid, Spain, were studied over 3 years (from 2000 to 2002 inclusive). The patients were divided into three age groups: group 1 (infants), group 2 (2- to 6-year-olds) and group 3 (7- to 14-year-olds).

RESULTS

A total of 428 bacteria were isolated. The most prevalent bacteria were Haemophilus influenzae (44.8 %) and Streptococcus pneumoniae (30.6 %) followed by Staphylococcus aureus (7.5 %), S. viridans (7.2 %), Moraxella catarrhalis (6.8 %) and Enterobacteriaceae (4.2 %). In 56 exudates (15.1 %), two or more bacteria were isolated and S. pneumoniae 1 H. influenzae were found in 8.1 % of the cases. By age group, S. aureus was significantly more prevalent (p < 0.0001) in group 3 than in groups 1 and 2. Isolation of Enterobacteriaceae, S. viridans and non-fermentative Gram negative bacilli was significantly more frequent (p < 0.05) in group 1 and isolation of S. pneumoniae (p < 0.05) was significantly more frequent in group 2. S. pneumoniae showed the greatest level of resistance to antibiotics used in eye drops and ophthalmic ointments. Ciprofloxacin, chloramphenicol and rifampin were active in the most prevalent pathogens.

CONCLUSIONS

The most prevalent bacteria were H. influenzae and S. pneumoniae. The most active antibiotics in these pathogens were ciprofloxacin, chloramphenicol and rifampin.

Evaluation of the specificities of five DNA amplification methods for the detection of Neisseria gonorrhoeae

The intragenus specificities of five molecular diagnostic methods for Neisseria gonorrhoeae were determined. Three assays were considered suboptimal. Molecular detection of N. gonorrhoeae from sites where other Neisseria spp. commonly occur or from any site in low-prevalence settings should be confirmed by a test targeting a different genetic locus.

[Moraxella catarrhalis: virulence and resistance mechanisms]

It is more than a century ago that Moraxella catarrhalis was discovered and described in some detail. However, it was not until the last decade that M. catarrhalis was recognized as a facultative pathogen, namely in otitis media (predominantly in children), sinusitis and nosocomial pneumonia in the group of elderly, debilitated patients. Liberation of endotoxin, histamine, and chemotactically active factors can be considered the major pathogenicity factors. The pathogen can protect itself, on the one hand by binding of the Clq subcomponent of the complement system followed by subsequent formation of a functionally inactive complex with Cl, and on the other hand by inactivation of the terminal (lytic) complement complexes by means of a specific protein on the surface of the outer cell wall. Routine diagnostic procedures require, above all, culture of the pathogen: up to now the detection of specific IgA-antibodies has not been routinely available. More than half of the clinical isolates are known to exhibit beta-lactamase production (BRO-enzymes). This is the reason why combinations of a penicillin compound with a beta-lactamase inhibitor, the group of the newer cephalosporins (including the orally active ones), doxycycline and the macrolides are therapeutically effective.

Recurrent bacterial peritonitis caused by Neisseria cinerea in a chronic ambulatory peritoneal dialysis (CAPD) patient

We present an unusual case of recurrent (chronic ambulatory peritoneal dialysis) CAPD-associated peritonitis caused by Neisseria cinerea. Using DNA restriction fragment length polymorphism (RFLP) analysis, we determined that the recurrent infection was caused by reinfection with a different N. cinerea strain rather than relapse with the index strain and that the probable origin of the reinfecting organism was the patient's upper respiratory tract.

Genetic diversity of the iron-binding protein (Fbp) gene of the pathogenic and commensal Neisseria

The pathogenic Neisseria and most commensal Neisseria species produce an iron-binding protein (Fbp) when grown under iron-limited conditions. In the current study, we confirmed the presence of Fbp, as well as DNA sequences homologous to the gonococcal fbp, in strains of N. gonorrhoeae, N. meningitidis, N. cinerea, N. lactamica, N. subflava, N. kochii and N. polysaccharea. The fbp genes from these strains were amplified by the polymerase chain reaction, digested with StuI or RsaI, and the restriction patterns examined. The patterns for the gonococcal and meningococcal fbp were virtually identical; however, variations were observed in the fbp sequences of the commensal Neisseria species. N. flavescens, N. mucosa, N. sicca, N. ovis and Branhamella catarrhalis, did not produce Fbp as detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and reactivity with an Fbp specific monoclonal antibody, nor did they hybridize to an fbp-specific DNA probe.

Comparative evaluation of AccuProbe culture identification test for Neisseria gonorrhoeae and other rapid methods

The AccuProbe chemiluminescent culture identification test for Neisseria gonorrhoeae (Gen-Probe Inc., San Diego, Calif.) was assessed in a comparative evaluation with other rapid methods by using 269 isolates of oxidase-positive, gram-negative diplococci. Chemiluminescence was read with a PAL luminometer, and results were expressed as PAL light units (PLUs): the cutoff value for a positive identification was 1,500 PLUs. All 200 isolates of gonococci confirmed by carbohydrate utilization and serotyped with monoclonal antibodies were identified correctly by AccuProbe on initial testing. The API Quadferm system (Bio Merieux, Marcy l'Etoile, France) identified 95% (n = 190) of the gonococci correctly on initial testing and 99.5% (n = 199) on repeat testing, while the Phadebact Monoclonal GC test (Kara Bio Diagnostics AB, Huddinge, Sweden) identified 95.5% (n = 191) of the gonococci on both initial and repeat testing; 8 of the Phadebact-negative isolates were all of the same rare serovar (serovar 1B-17). The mean PLU for the gonococcal isolates was 9,014 (range 2,264 to 10,845) compared with a mean of 51 (range, 8 to 109) for the 69 nongonococcal isolates. We conclude that the AccuProbe culture confirmation test provides a rapid and accurate objective means of identifying cultured N. gonorrhoeae isolates.

Branhamella catarrhalis: an organism gaining respect as a pathogen

Branhamella catarrhalis was formerly regarded as a common, essentially harmless inhabitant of the pharynx. This misapprehension was caused, in part, by confusion with another pharyngeal resident, Neisseria cinerea. The two organisms can now be differentiated by the positive reactions of B. catarrhalis in tests for nitrate reduction and hydrolysis of tributyrin and DNase. B. catarrhalis is currently recognized as the third most frequent cause of acute otitis media and acute sinusitis in young children. It often causes acute exacerbations of chronic bronchopulmonary disease in older or immunocompromised adults and is incriminated occasionally in meningitis, endocarditis, bacteremia, conjunctivitis, keratitis, and urogenital infections. Virulence-associated factors, such as pili, capsules, outer membrane vesicles, iron acquisition proteins, histamine-synthesizing ability, resistance to the bactericidal action of normal human serum, and binding to the C1q complement component, have been identified in some strains. beta-Lactamase producing strains, first detected in 1976, have risen to approximately 75% worldwide. Thus far, however, practically all American strains of B. catarrhalis remain susceptible to alternative antibiotics. A possible selective advantage of recent isolates is their reportedly heightened tendency for adherence to oropharyngeal cells from patients with chronic bronchopulmonary disease.

Ophthalmia neonatorum caused by Neisseria cinerea

Neisseria cinerea is an organism that has only recently been implicated as a human pathogen. In this case, N. cinerea was identified as the cause of ophthalmia neonatorum (conjunctivitis) in a 2-day-old girl.

Identification of Neisseria spp., Haemophilus spp., and other fastidious gram-negative bacteria with the MicroScan Haemophilus-Neisseria identification panel

The Haemophilus-Neisseria identification (HNID) panel (American MicroScan, Sacramento, Calif.) is a 4-h microdilution format system for identification of Haemophilus and Neisseria spp., Branhamella (Moraxella) catarrhalis, and Gardnerella vaginalis. The HNID panel was evaluated by using 423 clinical isolates and stock strains of these organisms, and HNID identifications were compared with those obtained by conventional methods. In addition, 32 isolates representing six genera not included in the HNID data base were tested to determine whether these organisms would produce unique biotype numbers for possible inclusion in the data base. The HNID panel correctly identified 95.3% of 86 Neisseria gonorrhoeae strains, 96% of 25 G. vaginalis strains, and 100% of 28 Neisseria lactamica strains and 48 B. catarrhalis strains. Only 64.7% of 68 Neisseria meningitidis isolates were identified correctly owing to false-negative or equivocal carbohydrate and/or aminopeptidase reactions. Among the Haemophilus spp., 98.8% of 83 H. influenzae strains, 97.1% of 34 H. parainfluenzae strains, and 80% of 15 H. aphrophilus and H. paraphrophilus strains were correctly identified. Eight strains of Neisseria cinerea, a species not included in the data base, produced profiles identical with those for B. catarrhalis and N. gonorrhoeae. Isolates of other species not included in the data base, including Eikenella corrodens, Kingella spp., and Cardiobacterium hominis, produced unique biochemical reaction patterns on the panel. Modification of interpretative criteria for certain tests, expansion of the data base to include other species, and suggestions for additional confirmatory tests will increase the accuracy and utility of the HNID panel.

Characterization of the neisserial lipid-modified azurin bearing the H.8 epitope

The pathogenic Neisseria have multiple genes encoding proteins that bind monoclonal antibody (MAb) H.8. We previously reported the cloning and sequencing of a meningococcal gene (laz) encoding an H.8 MAb-binding protein with a consensus lipoprotein processing site, an N-terminal domain containing the epitope for H.8 MAb binding, and a C-terminal domain with extensive similarity to the sequences of azurins from other organisms. In the current study, we showed that the product of the cloned gene could be labelled with palmitic acid, that it was subject to globomycin-sensitive processing, and that it was immunologically cross-reactive with azurin from Pseudomonas aeruginosa. All neisserial species tested, both pathogens and commensals, produced a protein recognized by anti-azurin serum. Southern blots with oligonucleotide probes specific for the azurin domain of the gene showed that it was present in a single copy in the chromosome; it was highly conserved in gonococci and meningococci, and less conserved in commensal Neisseria species.

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.

Prevalence and persistence of Neisseria cinerea and other Neisseria spp. in adults

Neisseria cinerea is a commensal Neisseria sp. which was first described in 1906 but was subsequently misclassified as a subtype of Branhamella catarrhalis. N. cinerea resembles Neisseria gonorrhoeae in both cultural and biochemical characteristics and, thus, may also have been misidentified as N. gonorrhoeae. Of 202 patients whose oropharynges were colonized by Neisseria spp., N. cinerea was isolated in 57 (28.2%) patients, including 25 (30.1%) of 83 women, 22 (23.9%) of 92 heterosexual men, and 10 (37.0%) of 27 homosexual men in Seattle, Wash., in 1983 to 1984. N. cinerea was isolated from the urethra of only one (1.1%) patient. The oropharynges of many individuals were colonized persistently by strains of N. cinerea and other Neisseria spp.

Evaluation of a ten-minute chromogenic substrate test for identification of pathogenic Neisseria species and Branhamella catarrhalis

A ten-minute chromogenic substrate test was evaluated for its ability to rapidly identify pathogenic Neisseria spp. and Branhamella catarrhalis. Identifications obtained with this system were compared to those obtained using conventional procedures. The test correctly identified 98.9% of 90 Neisseria gonorrhoeae, 98.3% of 60 Neisseria meningitidis, 96.2% of 26 Neisseria lactamica, and 100% of 36 Branhamella catarrhalis strains. Eight Neisseria subflava strains that grew on modified Thayer-Martin agar were prolyl aminopeptidase positive and were misidentified as Neisseria gonorrhoeae. Other strains of saprophytic Neisseria spp. also reacted with the chromogenic substrates. The system was accurate and reliable for identifying the commonly encountered pathogenic species. In light of recent reports describing new species and atypical Neisseria strains, however, careful attention to the salient features of both common and atypical organisms is necessary for proper use of rapid enzymatic identification tests.

Characterisation of Branhamella catarrhalis and differentiation from Neisseria species in a diagnostic laboratory

To distinguish Branhamella catarrhalis from Neisseria species a study of 140 strains was made on simple laboratory media, with particular reference to deoxyribonuclease (DNase) production, superoxol reaction, and growth characteristics. All 97 clinical isolates of B catarrhalis (58 of which were beta-lactamase positive) and eight strains of B catarrhalis from the National Collection of Type Cultures were DNase positive and superoxol positive. None grew on modified New York City medium, modified Thayer Martin medium, MacConkey agar, crystal violet blood agar, nor under anaerobic conditions. Of the 16 different non-pathogenic Neisseria species tested, all were DNase negative, eight (50%) were superoxol reaction negative, and 13 (81%) grew on crystal violet blood agar. Using simple laboratory media, DNase, and superoxol tests, it was possible to identify B catarrhalis and to distingish it from pathogenic and non-pathogenic Neisseria species.

API QuadFERM+ with rapid DNase for identification of Neisseria spp. and Branhamella catarrhalis

The QuadFERM+ system (Analytab Products, Plainview, N.Y.), a 2-h carbohydrate degradation method for the identification of Neisseria spp., was evaluated along with a rapid DNase test for confirmation of Branhamella catarrhalis. QuadFERM+ identified 100% of 82 N. gonorrhoeae and 96% of 54 N. meningitidis strains. The two misidentified meningococcal strains were biochemically atypical and were also misidentified by the conventional method. Of 26 N. lactamica strains, 25 (96%) were correctly identified. Of 21 Neisseria spp., 14 (67%) produced carbohydrate reactions in agreement with the conventional procedure, and 7 strains produced detectable acid in the QuadFERM+ from maltose and sucrose but not glucose. All 9 N. cinerea and 30 B. catarrhalis strains were asaccharolytic by QuadFERM+. The rapid DNase test was positive for all B. catarrhalis strains and negative for all other organisms. Two beta-lactamase-positive N. gonorrhoeae strains and 25 (93%) of 27 beta-lactamase-positive B. catarrhalis strains were detected by the 2-h acidometric beta-lactamase test on the strip. QuadFERM+ with rapid DNase is a simple and easily interpretable method for identification of these organisms in the clinical laboratory.

Clinical evaluation of the Vitek Neisseria-Haemophilus Identification card

A clinical evaluation of the Vitek Neisseria-Haemophilus Identification (NHI) card (Vitek Systems, Inc., Hazelwood, Mo.) was performed with 480 clinical isolates and stock strains of Neisseria spp., Haemophilus spp., and other fastidious microorganisms included in the data base of the system. Identifications obtained with the NHI card were compared with those determined by conventional methods. The card identified 83.2% of 244 Neisseria spp. and Branhamella catarrhalis, 54.9% of 164 Haemophilus spp., and 84.7% of 72 fastidious gram-negative species with no further testing required. Some isolates produced good confidence-marginal separation identifications, in which the correct identification was listed with one or two other possible identifications and extra tests were required and suggested. When isolates producing good confidence-marginal separation identifications were included, correct identifications of these organism groups increased to 97.1, 92.7, and 94.4%, respectively. Among the commonly isolated microorganisms, the NHI card identified 99.1% of 110 N. gonorrhoeae, 98.5% of 68 N. meningitidis, 93.9% of 98 H. influenzae, and 95.6% of 46 H. parainfluenzae strains. All of these organisms produced excellent to very good confidence level identifications except for H. influenzae biotypes II, III, and VII, for which hemolytic reactions were required for differentiation from H. haemolyticus. The NHI card reliably identified other fastidious gram-negative species, including H. aphrophilus, Eikenella corrodens, Gardnerella vaginalis, and Kingella denitrificans.

Deoxyribonucleic acid relatedness among Neisseria gonorrhoeae, N. meningitidis, N. lactamica, N. cinerea and "Neisseria polysaccharea"

Deoxyribonucleic acid relatedness studies (S1 nuclease method with DE-81 filters method) indicated that Neisseria gonorrhoeae, N. meningitidis, N. lactamica and "N. polysaccharea" form a single genospecies, in which four subspecies can be delineated. However, from a clinical and practical viewpoint, it seems desirable to maintain N. gonorrhoeae, N. meningitidis, N. lactamica and "N. polysaccharea" as separate species. N. cinerea is a valid species, closely related to N. gonorrhoeae, N. meningitidis, N. lactamica and "N. polysaccharea". These five species were O to 46% related to the other known species of the genus Neisseria.

Exemplification of serological cross-reactivity of Neisseria lipopolysaccharides

Antibodies against the Gc2 serotype determinant of gonococcal lipopolysaccharides (LPS) and antisera against strains of meningococci were tested by ELISA against the Gc2 LPS, and the antibodies examined for inhibition by bacteria of prototype strains of gonococci and meningococci. From one of the anti-meningococcal sera and anti-lactose (anti-lac) type of antibody was isolated. The results showed that antigenic sites belonging to the serotype, variable, and common sets of determinants as defined for gonococcal LPSs, may cross-react with meningococci. The anti-lac antibody combined with all of 34 strains of gonococci, with 41 out of 44 strains of meningococci tested, and with a Neisseria cinerea strain. The anti-lac showed no reactivity with any of a number of other Gram-negative cocci or bacilli examined. The results indicate that LPS from most strains of the pathogenic Neisseria species share a lactosyl moiety, presumably an inner core structure, of similar or identical configuration.

Branhamella catarrhalis: significance in pulmonary infections and bacteriological features

A three-month survey revealed 29 patients at our hospital with symptoms of acute pulmonary infection, from whom Branhamella catarrhalis was isolated from lower respiratory tract specimens, in 18 cases in pure culture. Approximately 2% of all respiratory tract specimens examined during the period yielded growth of B. catarrhalis. All except one patient suffered from chronic pulmonary disease, notably chronic bronchitis. A phenotypic comparison was made between 55 strains of B. catarrhalis, of which 50 were recent isolates from lower respiratory tract specimens, and 23 Neisseria strains representing Neisseria meningitidis, Neisseria gonorrhoeae, Neisseria cinerea, Neisseria flavescens, Neisseria mucosa, Neisseria pharyngis, and Neisseria lactamica. The morphology of B. catarrhalis colonies is very characteristic, and when the diagnosis is suspected, testing for the ability to hydrolyze tributyrin may confirm it within hours. Ability to produce deoxyribonuclease is another property which differentiates B. catarrhalis from the Neisseria species. Otherwise, the combination of nitrate reduction and failure to produce acid from glucose, maltose, and sucrose establishes the diagnosis.

Branhamella catarrhalis. New methods of bacterial diagnosis

A total of 176 strains identified as Branhamella catarrhalis were isolated from various clinical specimens, mainly sputum (71), pharynx (49), eye (24), nose (11), ear (6) and tracheal aspirate (7). B. catarrhalis appeared as Gram-negative cocci in white colonies which were oxidase- and catalase-positive and which did not produce acidification of sugars. The 3 related species, Neisseria caviae, N. ovis and N. cuniculi were also white but the 'true asaccharolytic Neisseria' studied presented a yellow pigment. Only a few strains of B. catarrhalis were able to grow on selective medium. However, when Catlin's chemically defined medium was used, all strains of B. catarrhalis had a unique requirement for arginine. This characteristic differentiated B. catarrhalis from N. caviae and N. ovis (non-requiring), N. cuniculi (required cystine, proline and arginine) and N. canis and N. elongata (both non-requiring). All strains of B. catarrhalis reduced nitrate and nitrite, possessed deoxyribonuclease activity and hydrolysed tributyrin to butyric acid. B. catarrhalis liberated high concentrations of butyric acid, N. caviae, N. ovis and N. cuniculi moderate concentrations and other species of Neisseria minimal concentrations. All strains of B. catarrhalis were resistant to acetazolamide and the absence of gamma-glutamyl transferase activity differentiated B. catarrhalis from atypical meningococci which were always positive.

Difficulties in differentiating Neisseria cinerea from Neisseria gonorrhoeae in rapid systems used for identifying pathogenic Neisseria species

Neisseria cinerea and Neisseria gonorrhoeae may occur at the same body sites and may have similar colony morphologies. Ideally, systems used for rapid identification of N. gonorrhoeae should be able to differentiate N. cinerea from gonococci. We tested seven N. cinerea strains using the Gonochek II (Du Pont Diagnostics), Minitek (BBL Microbiology Systems), RapID-NH (Innovative Diagnostics, Inc.), RIM-N (American Microscan), and Phadebact (Pharmacia Diagnostics) systems. We found that the reactions produced by N. cinerea in Gonochek II, Minitek, and RapID-NH kits could be confused with the results produced by some strains of N. gonorrhoeae. The susceptibility of N. cinerea to colistin, its ability to grow on tryptic soy or Mueller-Hinton agar, and its inability to grow on modified Thayer-Martin medium help differentiate it from gonococci.

Production of 14C-labeled gas in BACTEC Neisseria Differentiation kits by Neisseria cinerea

Six strains of Neisseria cinerea were tested in BACTEC Neisseria Differentiation kits (Johnston Laboratories, Inc., Towson, Md.), and all yielded positive glucose growth indices and negative maltose and fructose growth indices. These results were similar to those achieved with Neisseria gonorrhoeae. However, most of the N. cinerea isolates tested yielded 3-h glucose growth indices that were lower than those obtained with gonococci. 14C-labeled gas was produced significantly faster (P less than 0.02) by N. gonorrhoeae than by N. cinerea. Additional studies suggested that the 14C-labeled gas produced by N. cinerea was carbon dioxide. N. cinerea strains were similar to Branhamella catarrhalis strains because both species failed to produce detectable acid from glucose, maltose, sucrose, fructose, and lactose in cysteine-tryptic agar media. However, in contrast to N. cinerea strains, B. catarrhalis strains did not metabolize glucose in BACTEC Neisseria Differentiation kits.

Proctitis associated with Neisseria cinerea misidentified as Neisseria gonorrhoeae in a child

An 8-year-old boy developed proctitis. Rectal swabs yielded a Neisseria sp. that was repeatedly identified by API (Analytab Products, Plainview, N.Y.), Minitek (BBL Microbiology Systems, Cockeysville, Md.), and Bactec (Johnston Laboratories, Towson, Md.) methods as Neisseria gonorrhoeae. Subsequent testing in a reference laboratory yielded an identification of Neisseria cinerea. It is suggested that identification of a Neisseria sp. isolated from genital or rectal sites in a child be confirmed by additional serological, growth, and antibiotic susceptibility tests and, if necessary, by a reference laboratory. The implications of such misidentifications are discussed.

Nosocomial pneumonia caused by a glucose-metabolizing strain of Neisseria cinerea

We describe what appears to be the first reported case of nosocomial pneumonia caused by Neisseria cinerea. The isolate metabolized glucose when tested in BACTEC Neisseria Differentiation Kits (Johnston Laboratories), but did not produce detectable acid in cystine-Trypticase (BBL Microbiology Systems) agar medium or in modified oxidation-fermentation medium. Clinical laboratories that rely on the BACTEC method for differentiation of pathogenic neisseriae should be aware of the fact that N. cinerea may mimic N. gonorrhoeae when tested in BACTEC Neisseria Differentiation kits. The ability of N. cinerea to grow well on tryptic soy and Mueller-Hinton agars and its inability to grow on modified Thayer-Martin medium are characteristics which help to distinguish N. cinerea from N. gonorrhoeae.