Neisseria Pathogenesis and Characteristics Quiz

Gram Negative Cocci

• Gram-negative cocci (GNDC) are clinically significant microorganisms.
• Common GNDC include Neisseria and Moraxella catarrhalis.
• Lecture covers characteristics and pathogenesis of these organisms.

Identification Methods for GNC

• Oxidase test is used for identification.
• Sugar fermentation tests utilizing API NH strips.

Pathogenicity and Host Range for Neisseria and Moraxella

• Table 17.1 details pathogenicity and host range for various Neisseria and Moraxella species.
• Specific species like N. gonorrhoeae and N. meningitidis are primary pathogens for humans only.
• Other species are opportunistic pathogens for warm-blooded animals.

Neisseria - Key Characteristics

• Most Neisseria spp. are aerobic and nonmotile.
• They are nonspore-forming gram-negative diplococci (GNDC).
• Cytochrome oxidase and catalase are positive.
• Most Neisseria species have complex growth requirements and are capnophilic (grow best in moist environments with high CO2).

Neisseria - Primary Human Pathogens

• N. gonorrhoeae (gonococci) is always pathogenic when present.
• N. meningitidis (meningococci) may be commensal in the upper respiratory tract.
• Both are fastidious, requiring enriched media for optimal recovery.

Pathogenic Neisseria - Virulence Factors

• Receptors for human transferrin allow competition for iron.
• Capsules prevent phagocytosis.
• Cell-outer membrane proteins exhibit antigenic variation to avoid antibody binding.
• Major outer membrane porin proteins (Por A/B, Protein II/Opa, Protein III) effectively inhibit inflammatory responses.
• Pili (T1 through T3) functions to evade the immune system and aid in attachment and genetic exchange.
• Lipooligosaccharide (LOS) or endotoxin differs from LPS.
• IgA protease cleaves IgA on mucosal surfaces.

N. gonorrhoeae - Infections in Men

• Most cases are symptomatic (90%), characterized by acute urethritis.
• Complications include epididymitis, urethral stricture and prostatitis.

N. gonorrhoeae - Infections in Women

• As many as 50% are asymptomatic, commonly affecting the endocervix and urethra.
• Symptoms include dysuria, cervical discharge and lower abdominal pain.
• Complications include pelvic inflammatory disease (PID), sterility, ectopic pregnancy, and perihepatitis.

N. gonorrhoeae - Non-STI Infections

• Blood-borne dissemination resulting from untreated infections.
• Can lead to gonococcal arthritis, skin lesions, oropharangeal infections, and anorectal infections.

N. gonorrhoeae - Ophthalmia Neonatorum

• Gonococcal eye infection can occur during vaginal delivery.
• Infection is preventable by administering erythromycin eye drops at birth.

N. gonorrhoeae - Specimen Collection and Transport

• Specimen type depends on patient symptoms.
• Typical specimens include: urogenital cultures (males and females), rectal cultures, oral/pharyngeal specimen, eyes, and blood/joint fluids.
• Specimens are highly sensitive to drying and temperature extremes.
• Special transport requirements include avoiding delays and using cold temperatures, Dacron, polyurethane, rayon, or nylon swabs, appropriate transport media, and commercial transport systems.

N. gonorrhoeae - JEMBEC system

• This system consists of modified Thayer-Martin agar and a CO2 generating system.
• Specimen is streaked on the surface of the agar.
• Agar is packaged for transport to the lab.

N. gonorrhoeae - Molecular Assays

• Molecular assays for N. gonorrhoeae provide unique collection and transport systems that vary depending on the institution and assay.
• Common molecular based transport systems include Hologic Aptima swab systems.

N. gonorrhoeae - Direct Microscopic Examination

• For general urogenital specimens, direct Gram stain is performed and culture may or may not be required.
• For pharyngeal specimens, direct Gram stain is not recommended, culture is required instead.
• Gram-stained smears from specimens such as cerebrospinal fluid (CSF) are used for identification.

N. gonorrhoeae - Cellular Morphology

• N. gonorrhoeae are gram-negative diplococci (GNDC) and can be intracellular or extracellular.
• Direct microscopic smears are often used for identification of urogenital specimens.
• For symptomatic men the presence of polymorphonuclear WBC (PMN) and intracellular GNDC is diagnostic of gonorrhea.
• For endocervical specimens, the presence of GNDC is not diagnostic.

N. gonorrhoeae - Cultural Characteristics

• N. gonorrhoeae grows best in a microaerophilic atmosphere (35–37°C, 3%–5% CO2).
• It is better incubated in warm media.
• Growth is best on chocolate agar.
• Colonies are small, gray-white, and convex in color, also translucent and shiny with smooth or irregular margins.
• Older colonies undergo autolysis, and up to five different colony types may be present.

Special Media for Growth of N. gonorrhoeae

• Chocolate agar supplemented with inhibitors (e.g., antibiotics).
• Common media for culture include Thayer-Martin, NYC and Martin-Lewis.

N. gonorrhoeae - ID (Biochemicals)

• Oxidase test is positive.
• Nitrogen reduction test is negative.
• Carbohydrate utilization test shows dextrose (glucose) to be positive and maltose, lactose and sucrose negative.
• Hydroxyprolylaminopeptidase is positive.
• Superoxol (30% H2O2) is positive.

N. gonorrhoeae - ID (Immunological Assays)

• Use of monoclonal antibodies attached to killed S. aureus cells for coagglutination.
• Fluorescent antibody testing is performed using monoclonal antibodies to Por protein.
• Sensitivity of these tests is generally high.

N. gonorrhoeae - ID (Molecular Methods)

• Matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry identifies the organisms based on their unique protein signatures and often used for faster identification.

N. gonorrhoeae - Treatment

• Ceftriaxone (a cephalosporin) is the recommended treatment, often with azithromycin to treat co-infection with Chlamydia.

N. gonorrhoeae - Antimicrobial Resistance

• N. gonorrhoeae can display plasmid-mediated penicillinase, chromosomally-mediated penicillin resistance, alterations in penicillin-binding proteins, and plasmid-mediated tetracycline resistance.

N. meningitidis - General Characteristics

• Only found in humans, often called meningococcus.
• May be commensal in the upper respiratory tract in 30% of the population.
• Often associated with meningococcemia and/or meningitis (disease uncommon in developed countries).
• Rarely associated with pneumonia, purulent arthritis, or endophthalmitis
• Has been recovered from urogenital and rectal sites.

N. meningitidis - Infections

• Incubation period is usually 1 to 10 days.
• Infection spreads to the bloodstream and potentially the central nervous system (CNS).

N. meningitidis - Infections (Symptoms and Characterization of Meningitis)

• Symptoms include frontal headaches, stiff neck, confusion, photophobia, nausea, vomiting.
• Meningitis is an inflammation of the meninges (membranes surrounding the brain)
• Spread of bacteria in meningococcemia leads to the appearance of skin petechiae, purpura, tachycardia and hypotension, severe cases are associated with Friderichsen syndrome with lesions and internal bleeding leading to shock.
• Symptoms can progress rapidly to be fatal (12-48 hours).
• Infections are common in 3–12 months old children.

N. meningitidis - Specimen Collection and Transport

• Specimens should be transported to the lab immediately—it is considered a medical emergency.
• Specimens should be kept from extreme heat or cold, never refrigerated.
• Specimens should include Cerebrospinal fluid (CSF), blood, nasopharyngeal swabs or aspirates, and joint fluids.

N. meningitidis - Direct Microscopic Examination

• Gram-stained smears of specimens—especially CSF—may show intracellular and/or extracellular gram-negative diplococci;
• High concentration improves detection.
• At least 1mL of CSF should be centrifuged at 1000xg for 10 minutes.
• Sediment is used for Gram stain and culture.
• Cytocentrifugation is a recommended technique.

N. meningitidis - Cultural Characteristics

• Organisms grow well on sheep blood agar (SBA) and chocolate agar in a microaerophilic atmosphere at 35-37°C.
• Selective media may be used for specimens with normal flora.
• Suspected isolates should be handled using biosafety level 2 (BSL-2) cabinet.

N. meningitidis - Laboratory-Acquired Disease

• Two laboratory-acquired cases of meningococcal disease were reported to the CDC in 2000.
• The victims were microbiologists and examined specimens without using appropriate biosafety protocols (open bench work).

N. meningitidis - Colonial Morphology

• Colonies take 18-24 hours and are medium-sized, gray, convex in shape;
• Encapsulated strains appear mucoid.
• Blood under colonies shows green tinge.
• Gamma hemolytic on BAP (Blood Agar Plates).

N. meningitidis - Identification

• Identification is based on colony morphology, microscopic morphology and an oxidase test.

N. meningitidis - Identification (Direct ID)

• Antigen detection tests: antigen detection tests (commercially available) directly identify capsular polysaccharide antigens in body fluids like CSF, urine, and serum.
• Common antigen detection tests are latex agglutination and coagglutination.
• If the result shows the isolate as N. meningitidis then serotyping (determining specific strains) is necessary.
• Molecular techniques (e.g. MALDI-TOF MS) are used for identification as well.

N. meningitidis - Treatment

• Penicillin is the first line treatment for confirmed meningitis.
• Third-generation cephalosporins are used for meningococcemia.
• Risk factors include close contact with patients.
• Chemoprophylaxis may be done using rifampin or ciprofloxacin.
• Azithromycin may be the treatment if ciprofloxacin is resistant.
• Routine susceptibility testing is generally not recommended.
• Chemoprophylaxis is generally not recommended for asymptomatic carriers.

N. meningitidis - Prevention

• Quadrivalent polysaccharide–protein conjugated vaccines are available.
• Vaccination is recommended for military recruits, asplenic patients over 2, laboratory scientists, and other high-risk groups.

Diseases of Nonpathogenic Neisseria Species

• Three groups are; traditional pathogens, commensal Neisseria spp. that grow on selective media, and commensal Neisseria spp. that do not grow on selective media.
• Nonpathogenic Neisseria species can be implicated in some infections.

Commensal Neisseria Species

• Usually identified by Gram stain and gross colony morphology.
• Considered as part of the usual oral biota.

Characteristics of Significant Species of Neisseria, Moraxella, and Kingella

• Table 17.5 provides a summary of characteristics of various significant species, aiding in differentiation.

Neisseria subflava

• Species name means "less yellow".
• Part of the upper respiratory and normal flora.
• Consists of three biovars.
• Can cause serious infections such as bacteremia, meningitis, and septicemia.

Moraxella catarrhalis - General Information

• Formally known as Neisseria catarrhalis or Branhamella catarrhalis.
• Normal commensal organism of the respiratory tract of humans and more common in children and elderly.
• Important opportunistic pathogen in predisposing factors such as age, immunodeficiency, neutropenia and chronic debilitating diseases.

Moraxella catarrhalis - Infections

• Common in otherwise healthy children and older adults, also causes upper and lower respiratory infections.
• Occurs especially in patients with COPD.

Moraxella catarrhalis - Clinical Infections

• Associated with acute otitis media, sinusitis, rare but dangerous systemic infections like endocarditis and meningitis, and bacterial tracheitis.

M. catarrhalis - Specimen Collection and Culture Morphology

• Specimen collection includes middle ear effusion, nasopharynx, sinus aspirates, sputum, and bronchial aspirates.
• No special requirements.

M. catarrhalis - Cellular Morphology

• Cells look similar to Neisseria species.
• Usually extra cellular.
• Can resist decolorization during Gram staining, which means that they can appear Gram-positive.

M. catarrhalis - Cultural Characteristics

• Optimal growth is at 35-35°C, prefers increased CO2, and inhibited on many Gonococcal selective media by colistin.
• Grows well on BAP, and CHOC media but not MAC.
• Colonial morphology is smooth, opaque, gray-white colonies and may resemble hockey pucks, pink-ish wagon-wheel appearance in older colonies.

M. catarrhalis - Identification

• Oxidase and catalase are positive.
• Nitrogen reduction test is positive.
• Organisms are asaccharolytic and dextrose/maltose/lactose/sucrose are negative.
• DNase and butyrate esterase are positive.
• Lipase test is positive.
• API NH can also be used.

M. catarrhalis - Treatment

• Most isolates of M. catarrhalis produce Beta-lactamases, and are resistant to ampicillin and amoxicillin.
• Common treatments include; extended-spectrum cephalosporins, azithromycin, quinolones, trimethoprim-sulfamethoxazole and amoxicillin-clavulanate acid.

Knowledge Checks (Questions and Answers)

• Knowledge checks covering various aspects of the organisms discussed in the lecture provide self-assessment.

Test your knowledge on the characteristics and virulence factors of Neisseria species. This quiz covers aspects such as immune evasion, specific pathogens, and optimal growth conditions for these bacteria. Perfect for microbiology students and enthusiasts!