Microbiology Neisseria Quiz

Gram-Negative Cocci (GNDC)

• Gram-negative cocci are clinically significant microorganisms frequently isolated.
• Neisseria and Moraxella catarrhalis are examples of GNDC.
• These organisms have specific characteristics and pathogenesis.
• Bacterial virulence is discussed regarding these organisms.
• Understanding their characteristics and pathogenesis is essential for clinical practice.

Identification Methods for GNC

• Oxidase test is used to identify GNC.
• Sugar fermentation tests use API NH strips for identification.

Pathogenicity and Host Range for Neisseria and Moraxella

• Table 17.1 details pathogenicity and host range for different Neisseria species and Moraxella catarrhalis.
• Specific species have a primary pathogen or opportunistic pathogen role.
• Host range varies—some only infect humans, others warm-blooded animals.

Neisseria - Key Characteristics

• Most Neisseria species are aerobic and nonmotile.
• They are not spore-forming.
• They are gram-negative diplococci.
• They are cytochrome oxidase and catalase-positive.
• Most species have complex growth requirements.
• They are capnophilic and grow best in moist environments.

Neisseria - Primary Human Pathogens

• Neisseria gonorrhoeae (gonococci) are always pathogenic.
• Neisseria meningitidis (meningococci) may be commensal or invasive pathogens of the upper respiratory tract of carriers.
• Both organisms are fastidious and require enriched media for optimal recovery.

Pathogenic Neisseria - Virulence Factors

• Receptors for human transferrin allow these organisms to compete for iron.
• Capsules prevent phagocytosis.
• Cell-outer membrane proteins cause useless antibody production by binding to pathogens and prevent binding of effective antibodies
• These proteins are effective against inflammatory responses and killing.
• Protein II (Opa) facilitates adherence to phagocytic and epithelial cells.
• Protein III blocks host serum bactericidal action (IgG).
• Pili provide five distinct colony types; T1 and T2 are virulent, while T3-T5 are not—they prevent phagocytosis, aid in attachment to tissues, and exchange genetic material.
• Lipooligosaccharide (LOS) or endotoxin—Lipid A moiety and core LOS differentiate it from LPS, cleaves IgA on mucosal surfaces, and causes disseminated infections.

N. gonorrhoeae - Infection in Men

• Most infections are symptomatic—acute urethritis, dysuria, and a purulent urethral discharge.
• Complications may include epididymitis, urethral stricture, or prostatitis.

N. gonorrhoeae - Infection in Women

• As many as 50% of N. gonorrhoeae infections are asymptomatic, impacting the endocervix and urethra most commonly.
• Symptoms may include dysuria, cervical discharge, and lower abdominal pain.
• Complications may include Pelvic Inflammatory Disease (PID), sterility, ectopic pregnancy, perihepatitis (Fitz-Hugh-Curtis syndrome), or pelvic peritonitis.

N. gonorrhoeae - Non-STI Infections

• Blood-borne dissemination (less than 1%) caused by untreated infection.
• Fever, intermittent bacteremia, and rash on the extremities may be present.
• Gonococcal arthritis results when bacteria migrate to joints, resulting in skin lesions.
• Extragenital infections (e.g., pharyngitis and anorectal infections) are more common in men who have sex with men. Rectal pain or bloody stools may also be present.
• Acute eye infection (ophthalmia neonatorum) caused by gonococcal eye infection during vaginal delivery. Infection can be prevented by applying erythromycin eye drops at birth.

N. gonorrhoeae - Specimen Collection and Transport

• Specimen collection depends on patient symptoms and types, including urogenital cultures (urethral swabs in males, vaginal or endocervical swabs in females), rectal cultures (insert swab 4-5 cm into canal), oral/pharyngeal specimens, eyes, and blood/joint fluids.
• Specimens should be transported to a laboratory ASAP.
• Using a commercial transport system (e.g., Bio-Bag, Gono-Pak, JEMBEC) is recommended, with avoidance of delays or cold temperatures.
• Special requirements (e.g., use of cotton tip swabs, calcium alginate swabs, or cotton buds) are necessary, along with avoiding drying and temperature extremes.

N. gonorrhoeae - JEMBEC system

• The JEMBEC system utilizes a specialized MTM agar and a CO2 generating system.
• Specimens are collected, and a Z pattern is streaked on the MTM agar surface.
• The agar is packaged and transported to the lab for analysis.

N. gonorrhoeae - Specimen Collection and Transport (Molecular Assays)

• Molecular assays for N. gonorrhoeae use unique collection and transport systems that vary.
• Specialized Hologic Aptima swab systems are examples used for Hologic systems.

N. gonorrhoeae - Direct Microscopic Examination

• Urogenital specimens' direct Gram stain is performed, and culture may or may not be required.
• Direct Gram stain is not recommended for pharyngeal specimens due to commensal Neisseria spp. presence, with culture being required.
• Gram stain is crucial to verify the presence of gram-negative diplococci.

N. gonorrhoeae - Cellular Morphology

• N. gonorrhoeae are gram-negative diplococci that can be intracellular or extracellular.
• Gram stain is performed on suspected isolates.
• Direct microscopic smears are common for urogenital specimen identification.

N. gonorrhoeae - Cultural Characteristics

• Atmospheric conditions require 35°C, 3-5% CO2, and increased humidity.
• Specimens are incubated up to 72 hours.
• Organisms do not grow on BAP, MAC, but do on CHOC.
• Colonies can show varied morphologies (e.g., small, smooth, opaque, various sizes, etc.).
• Specialized media (e.g., Thayer-Martin, Martin-Lewis, NYC, GC-LECT) that inhibit gram-positive, gram-negative species, and yeast organisms is necessary to culture this organism.

N. gonorrhoeae - ID (Biochemical)

• Oxidase test is positive using filter paper or directly on the plate.
• Nitrogen reduction tests are negative.
• Carbohydrate utilization tests are positive for dextrose, and Hydroxyprolylaminopeptidase and negative for maltose/lactose/sucrose etc.
• Superoxol (30% H2O2) is positive in the test.

N. gonorrhoeae - ID (Immunologic Assays)

• Monoclonal antibodies—attached to killed S. aureus cells—are used in coagglutination.
• Sensitivity is generally high, but false-positives due to cross-reactions with other Neisseria species can occur.
• Fluorescent antibody tests use monoclonal antibodies to detect Por protein using fluorescent tags.

N. gonorrhoeae - ID (Molecular Assays)

• Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry identifies organisms by their unique protein signatures.
• Nucleic acid amplification tests (NAATs) are used; however, they cannot be used to test for susceptibility and are not useful for pharyngeal or rectal specimen analysis.
• NAATs are useful for high-volume testing on non-invasive samples like urine.

N. gonorrhoeae - Treatment

• CDC recommends ceftriaxone.
• Coinfection with Chlamydia trachomatis is frequent and frequently treated with ceftriaxone plus azithromycin.

N. gonorrhoeae - Antimicrobial Resistance

• N. gonorrhoeae exhibits resistance to antimicrobial agents, including various penicillinase-producing bacteria (e.g., PPNG), chromosome-mediated penicillin resistance, alterations in penicillin binding proteins, and plasmid-mediated tetracycline resistance.

N. meningitidis - General Characteristics

• Found only in humans.
• Can be a commensal in the upper respiratory tract (30% of population).
• It's considered an uncommon cause of meningococcal disease in developed countries.
• It may become invasive, causing epidemic meningitis and meningococcemia.
• Rarely associated with pneumonia, purulent arthritis, or endophthalmitis.
• Can be found in urogenital and rectal areas.

N. meningitidis - Infections

• Incubation period: 1 to 10 days
• Bacteria enter the bloodstream and potentially the central nervous system (CNS).
• Can cause meningococcemia and/or meningitis.
• Spread by close contact with respiratory droplets from a carrier to a new host

N. meningitidis - Infections (Characterizations, development, clinical)

• Meningitis, inflammation of the meninges, with symptoms such as frontal headache, stiff neck, confusion, photophobia, nausea and vomiting, and occasionally fever.
• Meningococcemia, N. meningitidis in bloodstream, with symptoms including petechiae, purpura, tachycardia, and hypotension. Severe cases may result in Waterhouse-Friderichsen syndrome and rapid fatality.

N. meningitidis - Specimen Collection and Transport

• Specimens should be transported to the lab immediately and not refrigerated.
• CSF is the primary specimen of choice, along with blood, nasopharyngeal swabs, joint fluids, and less commonly sputum or urogenital specimens.

N. meningitidis - Direct Microscopic Examination

• Direct Gram-stained smears of CSF specimens are used, focusing on whether the meningococci are intracellular or extracellular.
• Concentration of CSF is crucial for detection efficiency.

N. meningitidis - Culture and Incubation

• Organisms grow on sheep blood agar (SBA), chocolate agar, and special GC media.
• Selective media is used for specimens with normal flora.
• Incubation is typically at 35°C with 3-5% CO2 and elevated humidity.
• Examination of plates occurs daily for 72 hours.
• Work is performed in BSL-2 cabinets.

N. meningitidis - Laboratory-Acquired Disease

• Two laboratory-acquired cases of meningococcal disease were reported in 2000.
• Clinical microbiologists who examined or manipulated cultures made mistakes during Gram stain, subcultures, or slide agglutination.
• This likely occurred due to a lack of BSL-2 safety cabinet procedures.

N. meningitidis - Colonial Morphology

• Colonies typically appear within 18-24 hours.
• They are typically medium-sized, gray, and convex.
• Encapsulated strains are often mucoid with a green tinge underneath, and are gamma hemolytic on BAP.

N. meningitidis - Identification

• Colony morphology, microscopic morphology, and oxidase tests are used.
• Tests include oxidase tests, nitrate tests, carbohydrate utilization tests, and gamma-glutamylaminopeptidase testing.
• Using API NH testing is suitable for Moraxella.

N. meningitidis - Identification (Direct ID tests, Molecular techniques)

• Antigen detection tests detect capsular polysaccharide antigen.
• Latex agglutination and coagglutination tests are used for positive identification.
• Molecular techniques such as MALDI-TOF MS can be used for identification and verification.

N. meningitidis - Treatment

• Penicillin is used for confirmed meningitis.
• Third-generation cephalosporins are used for meningococcemia.
• Close contacts can receive prophylactic treatment with rifampin or ciprofloxacin, or azithromycin if ciprofloxacin exhibits resistance.
• Routine susceptibility testing is typically not recommended.

N. meningitidis - Prevention

• Quadrivalent polysaccharide-protein conjugated vaccines are available for some subtypes (A, C, Y, and W-135) for high-risk groups which include military recruits, splenic patients over two years old, laboratory scientists that work with N. meningitidis, and other high-risk groups.

Diseases of Nonpathogenic Neisseria Species

• Neisseria species are divided into three groups (pathogenic, selective media growers, and non-selective media growers).
• Nonpathogenic Neisseria are implicated in some infections.

Commensal Neisseria Species

• These organisms are typically found in respiratory specimens.
• Identification often relies on Gram stain and gross colony morphology.
• Further testing may not be necessary unless the organism is found in sterile sites.

Characteristics of Significant Species of Neisseria, Moraxella, and Kingella

• Table 17.5 shows characteristics of significant species.

Neisseria subflava

• Species name means "less yellow."
• Part of the upper respiratory microbiota.
• Consists of three biovars differentiated by carbohydrate utilization patterns.
• Can cause serious infections like bacteremia, meningitis, and septicemia.
• May be confused with N. meningitidis.

Moraxella catarrhalis - General Information

• Formerly known as Neisseria catarrhalis and Branhamella catarrhalis, it is a gram-negative coccus.
• A normal commensal of the respiratory tract.
• Important opportunistic pathogen, isolated only from humans.
• More common in children and the elderly.

Moraxella catarrhalis - Infections

• Upper respiratory tract infections in otherwise healthy children and the elderly.
• Lower respiratory tract infections, especially in patients with chronic obstructive pulmonary disease (COPD).
• Predisposing factors include advanced age, immunodeficiency, neutropenia, and chronic debilitating diseases.

Moraxella catarrhalis - Clinical Infections

• Considered the third most common cause of acute otitis media in children.
• Rare cause of life-threatening systemic diseases like endocarditis, meningitis, and bacterial tracheitis.
• Severe infections may occur in immunocompromised hosts, with hospital outbreaks being a concern.

M. catarrhalis - Specimen Collection and Morphology

• Specimen collection includes middle ear effusions, nasopharynx, sinus aspirates, sputum, or bronchial aspirates.
• No special requirements like for Neisseria species.
• Cells are similar to Neisseria species, typically extracellular, and can sometimes resist decolorization in Gram stains resulting in a falsely positive gram-stain.

M. catarrhalis - Cultural Characteristics

• Optimum growth occurs at 35-37°C with increased CO2.
• Organisms are inhibited on gonococcal selective media that contains colistin.
• Grows on BAP and CHOC, not MAC.
• Colonies are smooth, opaque, gray to white, and may appear as a hockey puck and are not motile.
• Older colonies may resemble a "wagon-wheel" appearance.

M. catarrhalis - Identification

• Oxidase and catalase are positive.
• Nitroreduction tests are positive.
• Asaccharolytic with negative results in the dextrose/maltose/lactose/sucrose test.
• Positive results are observed in DNase, butyrate esterase, and lipase tests.
• API NH is suitable for testing Moraxella.

M. catarrhalis - Treatment

• Most isolates produce beta-lactamase, rendering them resistant to ampicillin and amoxicillin.
• Antimicrobial therapy includes amoxicillin-clavulanic acid, extended-spectrum cephalosporins, azithromycin, quinolones, and trimethoprim-sulfamethoxazole.

Test your knowledge about Neisseria species, including their classification, pathogenicity, and growth requirements. This quiz covers essential aspects of the genus Neisseria, including key pathogens like N. gonorrhoeae and N. meningitidis. Perfect for microbiology students and enthusiasts!