Gram Negative Cocci Identification Quiz

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Questions and Answers

What best describes the primary human pathogens of the Neisseria genus?

N. gonorrhea is always pathogenic, while N. meningitidis may be commensal. (correct)

Both N. gonorrhea and N. meningitidis are always pathogenic.

N. gonorrhea and N. meningitidis are both non-pathogenic.

N. meningitidis is always pathogenic, while N. gonorrhea can be pathogenic.

Which characteristic is NOT associated with Neisseria species?

Nonmotile

Gram-negative diplococci

Capnophilic

Spore-forming (correct)

What role do the pili of Neisseria play in its pathogenicity?

Aid in attachment and immune evasion. (correct)

Enhance motility of the bacteria.

Facilitate spore formation.

Act as a major outer membrane protein.

Which virulence factor of Neisseria is primarily responsible for enabling the bacterium to compete for iron?

Receptors for human transferrin Signup and view all the answers

What is the function of the Immunoglobulin A (IgA) protease in pathogenic Neisseria species?

Cleaves IgA on mucosal surfaces. Signup and view all the answers

Which of the following statements regarding Neisseria growth conditions is accurate?

They are fastidious and require enriched media for optimal recovery. Signup and view all the answers

What distinguishes lipooligosaccharide (LOS) from lipopolysaccharide (LPS) in pathogenic Neisseria?

LOS contains a lipid A moiety and core that differentiates it from LPS. Signup and view all the answers

Which component of Neisseria's outer membrane is involved in antigenic variation?

Major outer membrane porin proteins. Signup and view all the answers

What defines the term 'capnophile' as related to Neisseria species?

Organisms that require higher levels of carbon dioxide for growth Signup and view all the answers

Which component of pathogenic Neisseria helps to evade the immune system by preventing phagocytosis?

Capsule Signup and view all the answers

Which virulence factor of Neisseria is associated with its ability to block host serum bactericidal action?

Protein III Signup and view all the answers

What is a major characteristic of Moraxella catarrhalis that distinguishes it from Neisseria species?

Moraxella catarrhalis is typically found as a commensal organism Signup and view all the answers

Which property is indicative of Neisseria species being 'fastidious' in growth requirements?

They require enriched media for optimal recovery Signup and view all the answers

What is the role of lipooligosaccharide (LOS) in pathogenic Neisseria?

To function as an endotoxin Signup and view all the answers

Which characteristic correctly describes Neisseria gonorrhoeae?

Contains pili for facilitating adherence Signup and view all the answers

What is the primary consequence of antigenic variation in Neisseria species?

Production of non-functional antibodies Signup and view all the answers

Which method is appropriate for the identification of gram negative cocci?

API NH strips for sugar fermentation tests Signup and view all the answers

Which statement about Neisseria's growth environment is accurate?

Neisseria prefers a moist environment for optimal growth Signup and view all the answers

Study Notes

Gram Negative Cocci (GNC)

GNC are clinically significant microorganisms frequently isolated.
Include Neisseria and Moraxella catarrhalis.

Identification Methods for GNC

Oxidase test is used.
Sugar fermentation tests using API NH strips

Pathogenicity and Host Range of Neisseria and Moraxella

Neisseria gonorrhoeae is a primary pathogen affecting only humans.
Neisseria meningitidis is a primary pathogen affecting only humans.
Other Neisseria species are opportunistic pathogens affecting warm-blooded animals.
Moraxella catarrhalis is an opportunistic pathogen affecting only humans.

Neisseria Key Characteristics

Most Neisseria species are aerobic.
They are non-motile and non-spore forming.
Gram-negative diplococci.
Usually cytochrome oxidase and catalase positive.
Most species have complex growth requirements and are capnophilic (grow best in a moist environment with increased CO2).

Neisseria - Primary Human Pathogens

N. gonorrhoeae (gonococci) is always pathogenic.
N. meningitidis (meningococci) may be commensal but can become invasive pathogens in the upper respiratory tract of carriers.
Both require enriched media for optimal recovery.

Pathogenic Neisseria - Virulence Factors

Receptors for human transferrin (iron acquisition).
Capsule (prevents phagocytosis).
Cell-outer membrane proteins (antigenic variation, binding to pathogen and preventing antibody binding).
Major outer membrane porin proteins (Por A/B, protein II, and protein III).
Pili (five colony types, T1 and T2 virulent, aids in attachment, evading the immune system, exchange of genetic material cell to cell).

Lipooligosaccharide (LOS)

Lipid moiety that differentiates from lipopolysaccharide (LPS).
IgA protease (cleaves IgA on mucosal surfaces).

Neisseria gonorrhoeae Infections

Primarily an STI, humans are the only natural host.
May have asymptomatic carriers are a reservoir for disease transmission.
Confirmed cases must be reported to Public Health Unit.
Commonly transmitted by sexual contact (especially between ages 20 and 24).

N. gonorrhoeae Infection in Men

Often symptomatic (90%).
Causes acute urethritis (abrupt onset of dysuria and purulent urethral discharge).
Can lead to complications like epididymitis, urethral stricture, and prostatitis.

N. gonorrhoeae Infection in Women

As many as 50% are asymptomatic.
Common sites of infection are endocervix and urethra.
Symptoms (if symptomatic) include dysuria, cervical discharge, and lower abdominal pain.
Can lead to complications like pelvic inflammatory disease (PID), sterility, ectopic pregnancy, and perihepatitis (Fitz-Hugh-Curtis syndrome), and pelvic peritonitis.

N. gonorrhoeae - Non-STI Infections

Blood-borne dissemination (less than 1%) from untreated infection (fever, intermittent bacteremia, rash on extremities)
Gonococcal arthritis (bacteria migrates to joints).
Skin lesions.
Extragenital infections (pharyngitis, anorectal infections, most common in men who have sex with men. Rectal pain or bloody stools possible).
Acute eye infection in newborns (gonococcal ophthalmia neonatorum) during vaginal delivery through infected birth canal.

Specimen Collection and Transport for N. gonorrhoeae

Specimen collection depends on patient symptoms (urogenital, rectal, oral/pharyngeal, eye, blood/joint fluids).
Should be transported swiftly (specimens sensitive to drying and temperature extremes; DO NOT refrigerate and use commercial transport systems).
Special requirements for culture from most sites (avoid cotton swabs, long delays, and cold temperatures. Dacron, polyurethane, rayon, or nylon tipped swabs required; Transport media like Amie's charcoal).
Notification to the lab is necessary.
Specimen collection for N. gonorrhoeae must use sterile techniques.
JEMBEC system: consists of MTM agar (specialized for N. gonorrhoeae) and a CO2 generating system. The agar is then streaked on the MTM agar surface and packaged and transported.
Molecular assays for N. gonorrhoeae: Provide unique collection and transport systems varying according to assay needs.

N. gonorrhoeae - Direct Microscopic Examination

In general, direct Gram stain is performed on urogenital specimens to identify the bacteria.
Direct Gram stain is not often recommended on pharyngeal specimens as commensal Neisseria spp. can be present. A culture is required.
N. gonorrhoeae cell morphology (intracellular/extracellular gram-negative diplococci). A Gram stain must be performed.
Specimen preparation must be handled carefully.

N. gonorrhoeae - Cultural Characteristics

Grown in 35 Degrees Celsius to 5% carbon dioxide (CO2), higher humidity levels.
Warm media must be inoculated to room temperature.
Grow on CHOC media but not on BAP or MAC.
Colonial morphology is small, grayish, convex, translucent, shiny with smooth or irregular margins.
Older colonies undergo autolysis.
Specialized media (e.g., Thayer-Martin, Martin-Lewis, NYC, GC-LECT) with inhibitors are required to grow N. gonorrhoeae from clinical specimens.

N. gonorrhoeae - Identification (Biochemical and Immunologic)

Biochemical assays: N. gonorrhoeae identification using oxidase, carbohydrate utilization tests (e.g., dextrose, maltose, lactose/sucrose, superoxol), and nitrogen reduction.
Immunological assays: Coagglutination (monoclonal antibodies to killed S. aureus cells) and Fluorescent antibody testing (monoclonal antibodies to Por protein with fluorescent tags).

N. Gonorrhoeae - Identification (Molecular/Chromogenic)

Using molecular assays for identification (Matrix-assisted laser desorption ionization-time-of-flight [MALDI-TOF] mass spectrometry, Amplification tests and Polymerase chain reactions).
Chromogenic tests are also used.

N. meningitidis - General Characteristics

Found only in humans.
Commonly called meningococcus.
Often commensal in the upper respiratory tract (up to 30% of the population).
Meningococcal disease is less common in developed countries. It can become an invasive pathogen.
May be an important etiologic agent of epidemic meningitis and meningococcemia.
Rarely associated with pneumonia, purulent arthritis, or endophthalmitis.

N. meningitidis - Infections

Incubation period is 1–10 days.
Infection involves colonization of the mucosa with bacteria entering the bloodstream to potentially affect the CNS.
Leads to meningococcemia and/or meningitis.
Transmitted by close contact with respiratory droplet secretions from carriers to new hosts.

N. meningitidis - Signs and Symptoms

Signs: Meningitis (inflammation of the meninges), symptoms that include confusion, photophobia, nausea, and vomiting.
Development of meningitis occurs from the spread to the roof of the nasal cavity, as the area is highly vascular and can lead to the blood-brain barrier. Infection spreads into the cerebrospinal fluid and the meninges.
Meningococcemia involves bacteria in the bloodstream. Clinical signs include skin petechiae, purpura, tachycardia, and hypotension. Can lead to Waterhouse-Friderichsen syndrome (large lesions, internal bleeding, shock, and fast fatality).

N. meningitidis - Specimen Collection

Specimens are sensitive to drying and extreme temperatures; therefore, never refrigerated.
Specimens should be transported to the lab stat.
Specific specimens include cerebrospinal fluid (CSF), blood (non-SPS-containing blood collection system), nasopharyngeal swabs or aspirates, joint fluids, sputum, and less commonly, urogenital sites.

N. meningitidis - Direct Microscopic Examination

Gram stains are typically used to identify N. meningitidis in specimens such as CSF.
Meningococci appear as intracellular and extracellular gram-negative diplococci.
Higher concentration of CSF can better facilitate detection on direct exam.
At least 1 mL of the CSF specimen should be centrifuged.
A cytocentrifuge is often beneficial for ensuring the best outcome.

N. meningitidis - Cultural Characteristics

Growth on sheep blood agar (SBA), chocolate agar, and special GC media.
Speciments with normal flora should use selective media.
Incubate at 35° C with 3–5% CO2 and increased humidity.
Examine plates daily for 72 hours, and isolate suspected isolates using biosafety level-2 (BSL-2) cabinets to prevent laboratory-acquired disease.

N. meningitidis - Colonial Morphology

Colonies typically grow within 18 to 24 hours
Colonies on BAP and CHOC are medium sized; gray, and convex.
Encapsulated strains may be mucoid (have a tinge of green coloring). Gamma hemolytic is observed on BAP.

N. meningitidis - Identification

Based on colony morphology, microscopic morphology, and the oxidase test.
Biochemical tests: Oxidase test positive, Nitrogen reduction test negative, Carbohydrates utilization tests (e.g. Dextrose, Maltose, and Gamma Glutamyl-aminopeptidase).
Molecular tests, including antigen detection tests and polymerase chain reactions, are also used for faster specimen identification.

N. meningitidis - Treatment

Penicillin is used for confirmed meningitis.
Third-generation cephalosporins for meningococcemia.
Close contacts of patients may receive chemoprophylaxis (with rifampin or ciprofloxacin, or azithromycin if required).

N. Meningitidis Prevention

Vaccinations using 2-valent/4-valent conjugate vaccines.
Vaccinations recommended for: Military recruits, asplenic patients over 2 years of age, laboratory workers, and other high-risk groups.

Moraxella catarrhalis - General Information

Formerly known as Neisseria catarrhalis and Branhamella catarrhalis.
Moraxella species, M. catarrhalis is the only cocci.
Normal commensal of the respiratory tract.
Important opportunistic pathogen (isolated only from humans).
More common in children and older adults.

Moraxella catarrhalis - Infections

Causes: Upper respiratory tract infections in otherwise healthy children and older adults. Can also lead to chronic obstructive pulmonary disease (COPD).
Predisposing factors: Advanced age, immunodeficiency, neutropenia, and chronic debilitating diseases.

M. catarrhalis - Clinical Infections

Considered the third most common cause of acute otitis media, sinusitis, endocarditis, meningitis, and bacterial tracheitis in children.
Severe infections may occur in immunocompromised hosts, such as during hospital outbreaks.

M. catarrhalis - Specimen Collection

Specimens collected from body sites such as middle ear effusion, nasopharynx, or sinus aspirates/sputum/bronchial aspirates.

M. catarrhalis - Morphology

Cells look similar to Neisseria species, usually extracellular, gram-negative diplococci, and capable of resisting decolorization during Gram staining (so can incorrectly appear Gram-positive).

M. catarrhalis - Cultural Characteristics

Optimal growth 35–37°C with increased CO2.
Grows on BAP, CHOC, and NOT MAC.
Grows as smooth, opaque, gray-to-white colonies (Gamma hemolytic on BAP).
Colonies resemble hockey pucks.
Older colonies appear pink-ish, resembling wagon wheels.

M. catarrhalis - Identification

Biochemical assays used.
Positive Oxidase and catalase, Negative carbohydrate Utilization (Dextrose, Maltose, Lactose, Sucrose); Positive DNase, Butyrate esterase and Lipase.
API NH can be used.

M. catarrhalis - Treatment

Most isolates produce β-lactamase, making them resistant to ampicillin and amoxicillin.
Uses extended-spectrum cephalosporins, azithromycin, quinolones, and trimethoprim-sulfamethoxazole.

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Description

Test your knowledge on Gram negative cocci, specifically Neisseria and Moraxella catarrhalis. This quiz covers identification methods, pathogenicity, and key characteristics of these significant microorganisms. Perfect for microbiology enthusiasts and students.