Neisseria spp. & Moraxella Flashcards
What are the general characteristics of pathogenic Neisseria species?
Aerobic, Gram-negative diplococci
* Oxidase-and catalase-positive
* Capnophilic organisms
* Exist as normal flora in upper respiratory and urogenital tracts
Which species are considered primary pathogens among Neisseria?
N. gonorrhoeae and N. meningitidis
N. gonorrhoeae is always pathogenic, while N. meningitidis may be a commensal inhabitant
What is the morphology of Neisseria gonorrhoeae?
Gram-negative cocci, often found as diplococci
Commonly referred to as ‘Gonococcus’
How is Neisseria gonorrhoeae primarily spread?
By sexual contact
What complications can arise from Neisseria gonorrhoeae infections in males?
Epididymitis, urethral stricture, prostatitis
What percentage of women with gonorrhea are asymptomatic?
Up to 50%
What are common symptoms of gonorrhea in females?
Burning on urination, vaginal discharge, vaginal bleeding, fever, abdominal pain
What is disseminated gonococcal disease and who is it most commonly seen in?
Less than 1% of infections; usually seen in women
What are the preferred clinical specimens for diagnosing Neisseria gonorrhoeae in males and females?
Urethra in males and cervix in females
What medium should be used for transporting inoculated swabs of Neisseria gonorrhoeae?
Amies medium with charcoal
What is the correlation percentage of Gram stain results with culture results in males with discharge?
95%
What are the characteristics of Neisseria gonorrhoeae when viewed under a microscope?
Extracellular or intracellular Gram-negative diplococci
What is the incubation period for cultures of Neisseria gonorrhoeae?
Cultures should be held for 72 hours, with colonies appearing after 24-48 hours
What type of media is required for culturing Neisseria gonorrhoeae?
Selective media that reduces contaminating organisms
* Examples: Thayer-Martin, Modified Thayer-Martin, Martin-Lewis
What is the purpose of the oxidase test in identifying Neisseria gonorrhoeae?
To detect the presence of cytochrome oxidase
Fill in the blank: Neisseria gonorrhoeae is the second most commonly reported sexually transmitted disease after _______.
[chlamydia]
True or False: Neisseria meningitidis is always pathogenic.
False
What is the clinical significance of the pili in Neisseria gonorrhoeae?
Responsible for evading phagocytosis and exchange of genetic material
What are the primary sites of gonorrhea infection?
Urethra, endocervix, anal canal, pharynx, conjunctiva
What is the maximum time colonies can be held before identification?
72 hrs.
Colonies can appear after 24-48 hrs.
What is the presumptive identification for Neisseria gonorrhoeae?
Neisseria gonorrhoeae
What test must be completed on all isolates of Neisseria?
Oxidase test
What does the oxidase test detect?
Presence of cytochrome oxidase
What is the method used to perform the oxidase test?
Filter paper method or directly on agar medium
What indicates a positive reaction in the oxidase test using filter paper?
Purple colour
What is the oxidase reagent used in the oxidase test?
1% dimethyl-p-phenylene-diamine-dihydrochloride
What is the color change indicating a positive reaction when the oxidase reagent is placed directly on colonies?
Pink colour that turns to black
What is required for a definitive diagnosis of oxidase-positive Gram-negative diplococci?
Further testing must be completed
Name three oxidase-positive Gram-negative diplococci that can grow on gonococcal selective media.
- Moraxella spp.
- Neisseria meningitidis
- N. cinerea
What is the traditional method for identifying Neisseria species?
Carbohydrate utilization method
What does a positive result in the carbohydrate utilization test indicate for Neisseria gonorrhoeae?
Acid produced only in the glucose tube
What are the carbohydrate utilization test results for Neisseria species?
- Glucose only – N. gonorrhoeae
- Glucose and maltose – N. meningitidis
- Asaccharolytic – M. catarrhalis
What is the incubation period for the carbohydrate utilization test?
24-72 hours
What is the rapid carbohydrate test used for?
Tests for preexisting enzymes for carbohydrate utilization instead of bacterial growth
What is the superoxyl test used to differentiate?
N. gonorrhoeae produces vigorous and immediate bubbling
What are the immunologic methods for identifying N. gonorrhoeae?
Coagglutination or fluorescent antibody testing
What is the significance of the encapsulated strains A, B, C, Y, and W135 of Neisseria meningitidis?
Most often associated with epidemics
What are the virulence factors of Neisseria meningitidis?
- Pili
- Capsule
- Endotoxin production
- IgA protease
How is bacterial meningitis transmitted?
By respiratory droplets or oral secretions
What are common symptoms of bacterial meningitis?
- Fever
- Headache
- Stiff neck
- Nausea
- Vomiting
What is the mortality rate associated with meningococcemia?
25%
What specimens are collected for culture of Neisseria meningitidis?
- CSF
- Blood
- Nasopharyngeal swabs
- Aspirates
What agar supports the culture of Neisseria meningitidis?
Chocolate agar and sheep blood agar
What is a distinguishing feature of Moraxella catarrhalis in laboratory diagnosis?
Produces beta-lactamase
What type of colonies does Moraxella catarrhalis produce on culture?
Smooth, opaque, gray to white colonies
How is Moraxella catarrhalis differentiated from Neisseria species?
Positive DNase and butyrate esterase reactions
