Flashcards in Gram -ve Cocci; Chlamydia, Mycoplasmas, Treponemes and STDs Deck (21)
Describe the Gram stain appearance of Neisseria gonorrhoeae.
Why is N. gonorrhoeae a significant STD?
Rates of infection are increasing and high in 20-29 year olds, especially men. Also has high Aboriginal:Non-Aboriginal rate ratio of 18:1.
Is N. gonorrhoeae antibiotic resistant?
Yes - used to be sensitive to penicillin, now mostly resistant except rural WA. There is increasing resistance to ceftriaxone (the recommended first-line treatment).
Name the important chlamydias.
What health problems do different serovars of C. trachomatis cause?
LGV - lymphogranuloma venereum
What is the nature of C. psittaci infection?
Pneumonic illness with prominent systemic symptoms:
- Abrupt onset of fever
- Dry cough
- Pronounced headache
- Sweats and rigors
What type of infection does C. pneumoniae cause?
Respiratory - mainly lower tract infection
- 5% bronchitis and 10% community acquired cases
- highest incidence in elderly
- associated w/ pharyngitis or sinusitis
Can treponemes be Gram stained? Why?
No - it's extremely thin
Explain how dark ground microscopy works.
Applied in both light or electron microscopy where the unscattered beam is excluded, therefore showing the organism.
What is the cause of syphilis?
- Morphology: spiral
- Obligate intracellular pathogen (requires a host)
What is the duration and clinical features of primary syphilis?
- Chancre at site of inoculation (painless ulcer, raised firm edges)
What is the duration and clinical features of secondary syphilis?
- Begins with skin rash (palms/soles)
- Condyloma lata (warty lesion in moist areas, highly infectious)
- Mucous patches (highly infectious)
What is the duration and clinical features of tertiary syphilis?
Years to decades (about 25% of untreated cases)
3 possible forms:
(1) CNS - most common; damage to neurons of the cerebrum/spinal cord --> progressive dementia, sensory ataxia, pain and pupillary abnormalities. Destruction of spinal cord dorsal columns can also leave sufferers with a unique gait.
(2) Cardiovascular - small vessel vasculitis --> heart failure
(3) Gummatous - least common; granulomatous lesions of skin, bones or viscera
What is the main difference between mycoplasmas and other bacteria?
Mycoplasma are very small, and have no peptidoglycan in their cell envelopes.
How do we manage antibiotics for mycoplasma bacteria? (couldn't find answer on micromodule but it's a learning outcome)
Erythromycin, clarithromycin and azithromycin
What is the role of M. pneumoniae in human respiratory disease?
It causes tracheobronchitis, bronchiolitis and pneumonia. Pharyngitis and otitis media may accompany disease.
It's a common cause of community acquired pneumonia, especially in young people - "walking pneumonia"
What are the genital mycoplasmas, and what do they cause?
Mycoplasma hominis: PID, postpartum and postabortal fever
Ureaplasma urealyticum: urethritis, adverse pregnancy outcomes, postpartum and postabortal fever
Mycoplasma genitalium: cervicitis and PID
When does primary syphilis start following exposure? What about secondary?
Primary - 9-90 days after exposure
Secondary - 6 weeks to 6 months after exposure
If a woman has syphilis and falls pregnant, how does risk of transmission change, depending on which stage she is in?
If she's in 1st or 2nd, 60-90% risk of transmission
Early latent - 40% transmission
Late latent -
Why can Chlamydia and Mycoplasma not be seen on a gram stain?
Both lack peptidoglycan in their cell walls