Microbiology - Bacterial Pneumonia I and II

Question 1

What are the unique presentations of Pseudomonas aeruginosa in special populations?

Answer 1

P. aeruginosa has a few community-acquired presentations: endocarditis in IV drug addicts,
Otitis externa in underchlorinated hot tubs,
Osteochondritis in sneaker punctures,
corneal infections under contact lenses

Question 2

How is infection (pneumonia) with a pseudomonad treated?

Answer 2

Treat with latest combinations of antibiotics, test Ab sensitivity both before and during treatment.

All, but particularly P. aeruginosa, have extreme antibiotic resistance from combination of low-permeability outer membrane and efflux pumps.

Question 3

How is infection (pneumonia) with pseudomonas diagnosed?

Answer 3

Diagnose by culture and Gram stain

Question 4

Where is pseudomonas aeruginosa infection most commonly found?

Answer 4

Hospitals

All pseudomonas infections can present as septicemia/pneumonia with poor prognosis.

P. aeruginosa and B. cepacia have minimal growth requirements ➔ contaminate hospital sol’ns

Question 5

Where is B. cepacia (pseudomonas) most commonly found?

Answer 5

CF centers

All can present as septicemia/pneumonia with poor prognosis.

Question 6

In what populations is B. pseudomallei (pseudomonas) most commonly found?

Answer 6

B. pseudomallei in previously-ill travelers/immigrants or Vietnam veterans
All can present as septicemia/pneumonia with poor prognosis.

Question 7

In what population is B. mallei most commonly found?

Answer 7

B. mallei in previously-ill travelers/immigrants with animal handling history.
All can present as septicemia/pneumonia with poor prognosis.

Question 8

What are the pseudomonas pathogens?

Answer 8

Four P/B pathogens:
P. aeruginosa a common&serious nosocomial pathogen;
B. cepacia common, serious in context of CF;
B. pseudomallei and B. mallei rare in US but can be lethal

Question 9

How is P. aeruginosa unique when growing it in culture?

Answer 9

P. aeruginosa produces green pyocyanin in culture.

Question 10

Are the pseudomonads gram + or -?

Answer 10

All Gram(-), strict aerobes, nonfermenters, Oxidase(+), grow easily in culture.

Question 11

What is the treatment for chlamydial pneumonia?

Answer 11

Treat with tetracyclines (doxycycline) EXCEPT for pregnant/pediatric/allergic patients, who get erythromycin or other alternatives. Patients who get alternatives may need follow-up testing and retreatment.

Question 12

What are the unique factoids about chlamydia?

Answer 12

Chlamydia is a small, obligate intracellular bacterium (so must use drugs that penetrate the human cell membrane).

Question 13

How does chlamydia replicate?

Answer 13

Chlamydia replicate in a unique manner beginning with tiny, infectious, rugged, elementary bodies which “unpack” into reticulate bodies after infection.

Reticulate bodies form intracellular inclusions that are visible on microscopy; within the inclusions they multiply by binary fission, forming new reticulate bodies and later new elementary bodies.

Question 14

What special virulence factor does chlamydia have?

Answer 14

Unusual life cycle complicates research; one known virulence factor is T3SS used for entry & establishing inclusion body.

Question 15

What kind of chlamydia causes the urogenital infection?

Answer 15

C. trachomatis is the cause of several human diseases, particularly the common urogenital infection (safe sex practices!)

Question 16

C. pneumoniae, C. psittaci, and C. trachomatis can all cause _______

Answer 16

These are the chlamydias that cause pneumonia.

Question 17

What is problematic about P. aeruginosa as a nosocomial infection?
A Extreme antibiotic resistance
B Propensity to grow in low-nutrient aqueous solutions
C Ability to cause bacteremia
D All of the above

Answer 17

1: D: P aeruginosa is a formidable opponent for your hospital infection control

Question 18

What is SIMILAR about B. cepacia and B. pseudomallei?

Answer 18

Normally freeliving water microbes

Question 19

2. To which patient(s) is a B. cepacia infection dangerous despite treatment?
   A A pediatric CF patient
   B A geriatric cancer patient
   C A previously-healthy woman undergoing urinary catheterization
   D A and B not C
   E All of the Above

Answer 19

2: A: Cystic Fibrosis is the most important predisposition for poor outcomes of cepacia infection.

Question 20

Why has Legionella only recently emerged as a human pathogen?

Answer 20

Humans have created a new, human-proximal, habitat for it

Question 21

All these patients have Legionella infections – which is at highest risk for a bad outcome?
22yr old previously-healthy female with a fever
55yr old previously-healthy female with pneumonia
77yr old smoker male with pneumonia

Answer 21

77yr old smoker male with pneumonia

Question 22

Mycoplasma pneumonia resolves:
Spontaneously
With antibiotic treatment 
With antitoxin treatment
With antiviral treatment

Answer 22

Spontaneously; and

With antibiotic treatment

Question 23

What kind of bacteria is legionella?

Answer 23

Gram (-) rod;
Free-living form is motile (flagella); intracellular form is non-motile;
Opportunistic facultative intracellular pathogen with variable infection outcome

Question 24

How do you trace a legionella outbreak?

Answer 24

LD outbreaks trace to contaminated locations (NOT people)

Question 25

T/F: LD pneumonia is life-threatening even when treated with antibiotics

Answer 25

True

Question 26

How is legionella diagnosed?

Answer 26

Optimal diagnosis is by BOTH urine antigen test and culture of respiratory secretions (fastidious, special media required)

For geriatric community-acquired pneumonias in general, take samples for culture/ELISA first, start treatment w/ levofloxacin second, get labs back third

Question 27

How does legionella survive endocytosis?

Answer 27

Legionella survives endocytosis by monocytes&macrophages by altering endosomes so that it can multiply in them and then escape

Question 28

Is legionella contagious?

Answer 28

Exposure is from aspiration or inhalation of contaminated water - NOT contagious

Question 29

How is infection with C. burnetti diagnosed?

Answer 29

Diagnose by immunohistochemistry

Question 30

What bacteria causes Q fever?

Answer 30

C. burnetti

Question 31

What kind of bacteria is C. burnetti?

Answer 31

C. burnetii is a small coccus to short rod, zoonotic infection from ruminants.

Question 32

How is C. Burnetti transmitted?

Answer 32

Transmitted by aerosols, grows in aveolar monocyte/macrophages, survives endolysosomal fusion, extremely infectious, long-lived in environment,

Question 33

What is the presentation of infection with C. burnetti?

Answer 33

causes pneumonia+hepatitis = Q Fever

Question 34

How is Q fever (Infection with C. burnetti) treated?

Answer 34

treat with tetracyclines or fluoroquinolones

Question 35

What CBC finding does mycoplasma pneumonia cause?

Answer 35

Immunopathology: antibodies against mycoplasma cross-react with red blood cells (cold agglutinins) → anemia during infection.

Question 36

How are Mycoplasma structurally unique?

Answer 36

Mycoplasma are unique among bacteria in lacking a cell wall and including cholesterol in their cell membrane.

Question 37

What is the most common infection caused by mycoplasma?

Answer 37

Causes “walking” pneumonia: mild and self-limited

Question 38

What virulence factor does mycoplasma use to exacerbate the cough it causes?

Answer 38

CARDS exotoxin-induced ciliostasis, local inflammation, local tissue destruction.

Ciliostasis → dry cough, exacerbates bronchitis, asthma

Question 39

How is pneumonia caused by mycoplasma treated?

Answer 39

Treat as needed with tetracyclines or macrolides (fluoroquinolones also fine)

Question 40

How does mycoplasma survive initial immune response to cause pneumonia?

Answer 40

Persistence through slow growth and intracellular hiding