Neisseria and Moraxella Species

Gram Staining & Morphology
- Neisseria species present as gram-negative diplococci on a gram stain.
- Appearance includes shapes similar to kidney beans or coffee beans.
- Misidentification possible if gram staining is inadequate, particularly with gram-positive cocci.
- Important to specify gram negative diplococci rather than just gram negative cocci, as only clinically significant species are diplococci.

Small size, non-motile organisms.
Biochemical Testing Initiation
- Begin with the oxidase test: Neisseria species are oxidase positive.
Environmental Requirements
- Capnophilic: Thrive in environments with 5-7% CO₂.
- Require humidity for growth; normal flora in human and animal mucous membranes.
- Pathogenic potential increased in immunosuppressed individuals.

Neisseria gonorrhoeae
- Always a pathogen.
Neisseria meningitidis
- May be commensal but can cause invasive disease (e.g., meningitis).
Neisseria lactamica
- Opportunistic pathogen.
Neisseria sicca
- Opportunistic pathogen.

Most of these species are normal flora in upper respiratory tract and genitourinary tract, acting as commensal organisms (benefit without harming the host).

Growth on sheep blood agar (except for N. gonorrhoeae, which grows poorly on this medium).
N. gonorrhoeae: Very small colonies on blood agar; better growth on chocolate agar.
Selective media developed for isolation:
1. Modified Thayer Martin
  - Chocolate agar with vancomycin (inhibits gram positives), colistin (inhibits gram negatives), and nystatin (inhibits yeast) + trimethoprim (to inhibit Proteus).
2. Martin Lewis agar
  - Similar to Thayer Martin but with increased vancomycin.
3. New York City agar
  - Contains lysed horse blood and plasma, effective for mycoplasma isolation.
Incubation at body temperature, optimized for CO₂ levels.
Plates checked at intervals (24, 48, and 72 hours) for negative results.

Oxidase Test: Essential for Neisseria, confirming oxidase positivity.
Superoxal Test: 30% hydrogen peroxide for rapid identification of N. gonorrhoeae; distinct bubbling indicates a reaction.
CTA Sugars Test:
- Utilizes tubes with 1% of a singular carbohydrate (up to 5 tubes).
- Incubation should prevent CO₂ influx to avoid false positives due to acidity.
- Yellow color indicates acid production from carbohydrates, utilized for speciation.
- Correlations of sugars with species:
  - N. gonorrhoeae: Positive for glucose.
  - N. meningitidis: Positive for glucose and maltose.
  - N. lactamica: Positive for lactose.
  - N. sicca: Positive for sucrose.

Receptors for transferrin: Aid in iron acquisition by breaking down lactoferrin.
Polysaccharide capsule: Prevents phagocytosis.
Outer membrane protein antigens: Mediate immune evasion.
IgA proteases: Neutralize mucosal antibodies, aiding infection establishment.
Pili: Facilitate attachment to host tissues; contribute to genetic exchange.

Pathogen in all encounters; primarily infected via sexual contact.
High infection rates in ages 20-24.
Causes gonorrhea, potentially leading to gonococcal arthritis and other complications.
Women can be asymptomatic; up to 50% risk in women versus 3-5% in men.
Infections can occur in multiple sites (vagina, endocervix, urethra, pharynx, anal canal).
Consequences for untreated infections: pelvic inflammatory disease, sterility, and ectopic pregnancy.
Gonococcal ophtymalia neonatorum: Infection in newborns from birth canal, preventable with treatment (silver nitrate, penicillin).

Dacron/rayon swabs preferred; initiate plating within 6 hours of collection.
GEMBEC system: Maintains optimum growth conditions during transport, using modified Behr Martin or New York City agar.

Confirmation via oxidase test, glucose positivity on CTA sugars, and various rapid tests (including MALDI TOF and nucleic acid tests).
Treatment: Current recommendation is ceftriaxone, often tested alongside Chlamydia trachomatis due to occurrence of co-infection.

Inhabitants of the human mucosal surfaces (nasopharynx, oropharynx).
Source for epidemic meningitis and meningococcemia, transmitted via respiratory droplets in close communities.
Typical onset of symptoms: stiff neck, fever, headaches.
Associated mortality rate of 25% even with treatment; individuals lacking certain immune factors at increased risk.
Waterhouse-Friedrichsen syndrome: A severe form due to adrenal failure associated with the infection.

Cerebrospinal fluid, blood (avoid SPS in culture systems), nasopharyngeal swabs/aspirates essential.
Similar growth conditions to N. gonorrhoeae (blood agar, chocolate agar, CO₂ incubation).

Confirmed positive results via oxidase test; useful metabolic properties include glucose and maltose utilization.
Treatment of choice: penicillin, though susceptibility testing is usually irrelevant due to safety considerations.
Two vaccines available:
1. Conjugated vaccine for group B strains, effective primarily in young adults.
2. Quadrivalent conjugated vaccine for subtypes A, C, Y, and W135 for high-risk individuals.

Neisseria lactamica
- Typically non-pathogenic; peaks in young children.
- Utilizes lactose in carbohydrate tests.
Neisseria sicca
- Found in adult respiratory systems, oxidase positive; glucose, maltose, and sucrose utilization.

Previously known as Neisseria catarrhalis; now a distinct Moraxella species.
Commensal in respiratory tract but can cause opportunistic infections.
Associated diseases: otitis media, sinusitis, and exacerbations in COPD patients.

Similar growth on blood and chocolate agar, but colony morphology resembles a hockey puck.
Differential Tests:
- Butyrate esterase test: Positive for Moraxella, indicated by a blue color.
- DNase Test: Indicates hydrolysis of DNA; Moraxella produces positive results.
- Tributarine Test: Rapid test for presumptive identification based on butyrate esterase activity.

Most isolates produce beta-lactamase, necessitating the use of alternative antibiotics like extended-spectrum cephalosporins, azithromycin, or fluoroquinolones.