Atypical Pneumonia: Chlamydia, Legionella, and Mycoplasma Flashcards
Classify Chlamydia:
~Gram negative (inhibited by ampicillins although doesn’t have peptidoglycan cell wall)
Biphasic life cycle (infectious Elementary body and parasitic Reticulate body)
Obligate intracellular parasite
Classify Legionella:
Aerobic, gram negative rod.
Nonencapsulated
Facultative intracellular parasite
Classify Mycoplasma:
Lack a cell wall. Smallest free-living organisms known.
Nutritionally require cholesterol (uniqure for prokaryotes)
What is the poorly understood VF of chlamydia?
Type Three Secretions (TTS)
–interferes with host cell response pathways
What is the most common subtype of legionella?
Where does it replicate?
Legionella pneumophila.
Replicates in alveolar macrophages after inhalation
What are some mechanisms underlying the virulence of legionella?
1) avoids phagolysosome formation
2) Injected proteins alter host cell vesicle trafficking, forming a specialized vacuole that makes a bacterial endoplasmic reticulum
3) The bacterial ER supports replication
What are mechanisms underlying mycoplasma’s virulence?
1) Produce an adhesin complex that allows attachment to epithelial lung cells
2) A diacyl-lipoprotein interacts with TLR-2 and TLR-6 to cause inflammation
What is the hallmark of chlamydial infection?
Some people have mild to no apparent disease, while others have severe disease.
What is psittacosis also called?
What is it’s reservoir?
What is it’s symptoms?
Also called “Parrot Fever” (Chylamydia psittaci)
Birds are the reservoir. Spread by inhaling dried bird feces.
Gives a mild to sever respiratory tract infection.
Give 3 facts about Chlamydia pneumoniae:
1) Accounts for 6-10% of CA pneumonia
2) Humans = reservoir; spread by the respiratory route
3) Implicated in exacerbating asthma, causing coronary heart disease, and contributing to atherosclerosis via interactions with a serum lipoprotein.
What does Chylamydia trachomatis cause?
It’s reservoir?
Pertinent fact about it?
Ocular, respiratory, and genital tract infections.
Reservoir = humans.
It is the most common STD in industrialized countries. Most cases (50-70%) are clinically silent.
What is Trachoma?
What is a pertinent fact we need to know about it?
Trachoma = infection of the conjunctiva, caused by C. trachomatis infection immunotypes A - C.
It is the world’s leading preventable cause of blindness.
Which C. trachomatis immunotypes cause genital tract infections?
What are some serotypes associated with?
Immunotypese D - K.
Some are associated with cervical squamous cell carcinoma.
A neonate, shortly after birth, develops pneumonia and inclusion conjunctivitis that scars over. What is the problem?
The neonate became infected with C. trachomatis while being delivered through the vaginal canal.
**prevent this with erythromycin eye drops at birth
How is Legionnaires Disease spread?
Spread by contaminated water/mists. NOT human to human.
** Common contaminated sources: hot water tanks, water cooler, spas, hot tubs, air conditioners, grocery store produce mists.
** Outbreaks of pneumonia on cruise ships or at spas ** (however, most cases are single and isolated)
Who is at risk of getting Legionnaires Disease?
Elderly, immunocompromised, heavy smokers, alcoholics, Males 2x more than females
What is Pontiac fever?
A mild form of L. pneumophila, causing flu-like symptoms.
95% of those who are exposed get sick
What 3 conditions does Mycoplasma cause?
1) Primary atypical pneumonia
2) Nonspecific (nongonococcal) urethritis
3) Postpartum fever/Pelvic inflammatory disease
Describe primary atypical pneumonia:
1) 5-10% of CA pneumonias
2) Seen especially in 5-20 y/o’s in later summer/early fall
3) 3 week incubation compared to 3 days (influenza)
What causes nonspecific, nongonococcal urethritis?
Ureaplasma urealyticum
What causes Postpartum fever/pelvic inflammatory disease?
Mycoplasma hominis
Presentation of Chylamydia pneumonia?
1) 3-4 week incubation, gradual onset (most are asymptomatic)
2) Scant sputum
3) Prominent cough even with abx’s
4) Rhonchi, rales, hoarseness
**5) Headache and sinus percussion tenderness is more characteristic of this type of atypical pneumonia
Presentation of Legionnaires Disease?
Very much like other pneumonias. (fever, chills, cough, flu-like sx)
NOTE: legionella also causes a mild nephritic syndrome, so you can see some hematuria and electrolyte abnormalities.
Pneumonia with hyponatremia*
Presentation of Mycoplasma pneumonia?
1) Insidious onset of days-weeks.
* *2) Slowly worsening dry cough causing chest tenderness
3) other atypical pneumonia signs/sx
**Most likely to infect you in your first 2 decades of life
How do you diagnose a chylamydia infection?
1) IgM titer 1:1t
2) 4x increase in IgG titer
3) rapid PCR test from a swab (experimental only)
**serologic tests are not always reliable for C. pneumonia
How do you diagnose Legionnaires’ Disease?
1) CXR can confirm (since legionella grow in alveolar macrophages)
2) Urinary Ag test (UAT)
3) serology
***Pneumonia symptoms + hyponatremia = Legionnaires’ Disease
How do you diagnose mycoplasma pneumonia?
nothing specific was given to us in the document
**Persistent dry coughing with chest tenderness for 3 or more weeks*
How do you treat chylamydia?
1) Doxycycline (unless < 9y/o, causes bad bone growth and stained teeth, and don’t give to preggers)
2) Erythromycin or azithromycin (macrolides)
***60% are mixed infections
How do you treat legionella?
1) Levofloxacin/azithromycin (quinolone + macrolide)
2) Macrolides for all ages; tetracyclines over age 12; quinolones over 18
increased mortality if treatment is delayed
How do you treat mycoplasma?
Macrolides or doxycycline prophylaxis only for IC patients.
