Neisseria and Gonococcus Overview

Study Notes

Neisseria are commonly found in the upper respiratory tract, mouth, throat, pharynx and vagina
Two highly pathogenic members:
- Neisseria gonorrhoeae (Gonococcus)
- Neisseria meningitidis (Meningococcus)
Gram-negative cocci, arranged in pairs
Occur intracellularly in pus cells and extracellularly
Requires enriched media (heated blood agar) e.g. chocolate agar, and selective Thayer Martin agar medium (MTM) with 5-10% CO2

Causes venereal diseases:
- Male infection of the anterior urethra (Urethritis) with yellow creamy pus and painful urination, chronic cases may be asymptomatic
- Female: endocervical infection causing vaginal discharge, 50% are asymptomatic
Non venereal infections:
- Ophthalmia neonatorum
- Vulvovaginitis
- Oral infections ranging from pharyngitis to painful erythema, ulceration of the soft palate, gingival and buccal mucosa.
Urogenital gonorrhea can be diagnosed by testing urine or urethral discharge (for men), or endocervical or vaginal discharge (for women)
Accurate tests include:
- Nucleic acid amplification testing (NAAT)
- Gonorrhea culture, which requires endocervical or urethral swab specimens.
Gram stain:
- Neisseria are gram-negative cocci, capsulated and arranged in pairs found both inside the pus cells of the inflammatory exudate-urethral discharge (intracellular) and outside (extracellular).
Treatment:
- Penicillin
- If resistant, Ciprofloxacin or streptomycin are recommended

Causes epidemic Cerebrospinal Meningitis
May also cause pharyngitis and rarely myocarditis.
Spread through droplets from infected individuals or carriers
Main harbor of the organism is the nasopharynx
Pathogenesis:
- Organism in nasopharynx to lymphatic system, then to the blood, causing meningococcemia
- Meningococcemia is characterized by: fever, skin rash, stiffness in the neck, back pain, severe headache and projectile vomiting.
Diagnosis:
- Specimen is cerebrospinal fluid (CSF) obtained by lumbar puncture under complete aseptic precaution and is subjected to the following analyses:
  - Direct examination:
    - CSF is examined microscopically by using Gram stain and Zeihl-Neelsen stain.
    - Latex agglutination test to detect antigen in CSF.
  - Culture on chocolate agar (enriched) and Thayer Martin agar media (selective)
  - blood culture
Treatment:
- Penicillin G is the drug of choice.
- Third-generation Cephalosporin is used in patients allergic to penicillin
- Chloramphenicol
- Penicillin and chloramphenicol have an antagonistic effect
Prevention and Control:
- Refampicin for 2 days given to contacts.
- Vaccination: CDC recommends routine MenACWY vaccination for all teens at 11-12 years with a booster dose at 16.

Most important pathogenic member in this genus is Bacillus anthracis
Other members are saprophytes in water, soil and air and are collectively termed anthracoids
Bacillus cereus and B. subtilis may act as opportunistic pathogens in debilitated individuals, causing bacteremia, meningitis, endocarditis or endophthalmitis
Bacillus cereus causes food poisoning after consuming cooked rice (Koshary) in which the spores grow profusely and produce enterotoxin

Causes anthrax
Anthrax is a disease of animals that can infect humans through direct contact with infected animals
Clinical types:
- Cutaneous anthrax (malignant pustule)
- Pneumonic anthrax (wool sorter disease) due to inhalation of spores
- Intestinal anthrax due to ingestion of infected meat is rare

Saprophytes found in the environment (soil and water)
Examples include:
- B. cereus, which causes food poisoning
- Antibiotic producer e.g., polymyxin
Used to test the efficiency of sterilization procedures:
- Spores of B. stearothermophilus to test the efficiency of the autoclave
- Spores of B. subtilis to test ethylene oxide gas sterilizer
- Spores of B. pumilis for ionizing irradiation