Atypical Pneumonia: Chlamydia, Legionella, and Mycoplasma

Question 1

Classify Chlamydia:

Answer 1

~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

Question 2

Classify Legionella:

Answer 2

Aerobic, gram negative rod.

Nonencapsulated

Facultative intracellular parasite

Question 3

Classify Mycoplasma:

Answer 3

Lack a cell wall. Smallest free-living organisms known.

Nutritionally require cholesterol (uniqure for prokaryotes)

Question 4

What is the poorly understood VF of chlamydia?

Answer 4

Type Three Secretions (TTS)

–interferes with host cell response pathways

Question 5

What is the most common subtype of legionella?

Where does it replicate?

Answer 5

Legionella pneumophila.

Replicates in alveolar macrophages after inhalation

Question 6

What are some mechanisms underlying the virulence of legionella?

Answer 6

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

Question 7

What are mechanisms underlying mycoplasma’s virulence?

Answer 7

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

Question 8

What is the hallmark of chlamydial infection?

Answer 8

Some people have mild to no apparent disease, while others have severe disease.

Question 9

What is psittacosis also called?

What is it’s reservoir?

What is it’s symptoms?

Answer 9

Also called “Parrot Fever” (Chylamydia psittaci)

Birds are the reservoir. Spread by inhaling dried bird feces.

Gives a mild to sever respiratory tract infection.

Question 10

Give 3 facts about Chlamydia pneumoniae:

Answer 10

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.

Question 11

What does Chylamydia trachomatis cause?

It’s reservoir?

Pertinent fact about it?

Answer 11

Ocular, respiratory, and genital tract infections.

Reservoir = humans.

It is the most common STD in industrialized countries. Most cases (50-70%) are clinically silent.

Question 12

What is Trachoma?

What is a pertinent fact we need to know about it?

Answer 12

Trachoma = infection of the conjunctiva, caused by C. trachomatis infection immunotypes A - C.

It is the world’s leading preventable cause of blindness.

Question 13

Which C. trachomatis immunotypes cause genital tract infections?

What are some serotypes associated with?

Answer 13

Immunotypese D - K.

Some are associated with cervical squamous cell carcinoma.

Question 14

A neonate, shortly after birth, develops pneumonia and inclusion conjunctivitis that scars over. What is the problem?

Answer 14

The neonate became infected with C. trachomatis while being delivered through the vaginal canal.

**prevent this with erythromycin eye drops at birth

Question 15

How is Legionnaires Disease spread?

Answer 15

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)

Question 16

Who is at risk of getting Legionnaires Disease?

Answer 16

Elderly, immunocompromised, heavy smokers, alcoholics, Males 2x more than females

Question 17

What is Pontiac fever?

Answer 17

A mild form of L. pneumophila, causing flu-like symptoms.

95% of those who are exposed get sick

Question 18

What 3 conditions does Mycoplasma cause?

Answer 18

1) Primary atypical pneumonia
2) Nonspecific (nongonococcal) urethritis
3) Postpartum fever/Pelvic inflammatory disease

Question 19

Describe primary atypical pneumonia:

Answer 19

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)

Question 20

What causes nonspecific, nongonococcal urethritis?

Answer 20

Ureaplasma urealyticum

Question 21

What causes Postpartum fever/pelvic inflammatory disease?

Answer 21

Mycoplasma hominis

Question 22

Presentation of Chylamydia pneumonia?

Answer 22

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

Question 23

Presentation of Legionnaires Disease?

Answer 23

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*

Question 24

Presentation of Mycoplasma pneumonia?

Answer 24

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

Question 25

How do you diagnose a chylamydia infection?

Answer 25

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

Question 26

How do you diagnose Legionnaires’ Disease?

Answer 26

1) CXR can confirm (since legionella grow in alveolar macrophages)
2) Urinary Ag test (UAT)
3) serology

***Pneumonia symptoms + hyponatremia = Legionnaires’ Disease

Question 27

How do you diagnose mycoplasma pneumonia?

Answer 27

nothing specific was given to us in the document

**Persistent dry coughing with chest tenderness for 3 or more weeks*

Question 28

How do you treat chylamydia?

Answer 28

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

Question 29

How do you treat legionella?

Answer 29

1) Levofloxacin/azithromycin (quinolone + macrolide)
2) Macrolides for all ages; tetracyclines over age 12; quinolones over 18

increased mortality if treatment is delayed

Question 30

How do you treat mycoplasma?

Answer 30

Macrolides or doxycycline prophylaxis only for IC patients.