19 Opportunistic Gram Negatives

Question 1

T/F- Almost any pathogen that can grow at 37 degrees can cause an opportunistic infection

Answer 1

True

Question 2

Characteristics of Klebsellia?

Answer 2

• Opportunistic enterobacteriacea
• Gram negative non-motile rod
• Prominent mucoid capsule enhances virulence
• Lactose positive

Question 3

What are the two most common species of Klebsiella isolated from medical patients?

Answer 3

K. pneumoniae

K. oxytoca

Question 4

T/F- Antibiotic resistance is not a significant problem in Klebsiella

Answer 4

False. Select Klebsiellas produce extended spectrum beta lactamases (ESBLs) and are resistant to many antibiotics. Choose antibiotic treatment based on local susceptibility patterns.

Question 5

Symptoms of Klebsiella infection?

Answer 5

fever
productive cough (often blood tinged)
May cause community acquired or hospital acquired pneumonia

Question 6

T/F- Klebsiella has a low mortality rate

Answer 6

False. A high mortality rate (over 50% even with Antibiotic treatment) is observed, likely due to the underlying concomitant medical conditions

Question 7

Characteristics of Proteus species?

Answer 7

• gram neg. rod
• swarming motility
• lactose negative
• urease positive

Question 8

Which species of proteus causes 90% of all proteus infections?

Answer 8

P. mirabilis

Question 9

What are the typical infections caused by proteus?

Answer 9

UTI
wound 
septicemia
pneumonia
(These mostly occur in hospitalized patients)

Question 10

What organism causes urinary stones (struvite)? And how?

Answer 10

Proteus produces high levels of urease=>hydrolyzes urea to ammonia=>increased alkalinity=>precipitates Mg and Ca

Question 11

Characteristics of Pseudomonas aeruginosa?

Answer 11

• Gram negative aerobic motile rod
• oxidase positive
• non fermenting (unlike enterobacteriacieae)
• mucoid exopolysaccharide (slime layer)
• grape-like odor
• blue-green pus

Question 12

Does pseudomonas aeruginosa produce any pigments? If so, which ones?

Answer 12

Yes
-pyocyanin: blue pigment
-pyoverdin: yellow pigment (siderophore)
-pyorubrum: red pigment.
REMEMBER P.  cepacia (Burkholderia cepacia) does not produce pigments!

Question 13

Where is pseudomonas found?

Answer 13

soil, water, plants

Question 14

What groups of patients are especially at risk for pseudomonas opportunistic infection? What are common infections?

Answer 14

• Burn patients (can’t bring plants into burn unit), cystic fibrosis
• swimmer’s ear (otitis externa), septicemia, pneumonia.

Question 15

T/F- Lungs of most children w/ cystic fibrosis become colonized with P. aeruginosa before the age of 10

Answer 15

True

Question 16

T/F- Pseudomonas bacteria have not yet acquired many antibiotic resistant genes

Answer 16

False

Question 17

Pseudomonas tend to form biofilms, how does this protect the bacteria?

Answer 17

Increased adhesion, immune evasion, and interferes with antibiotic treatment. They express new genes when biofilm forms!

Question 18

Burkholderia cepacia is related to P. aeruginosa. What type of infection is it associated with?

Answer 18

lung infections in CF patients

Question 19

What type of people are associated with Stenotrophomonas maltophila (p. maltophila) infections?

Answer 19

Hospital patients
HIV patients
immunocompromised patients

Question 20

Characteristics of Acinetobacter baumannii?

Answer 20

• Gram negative, non-motile rod
• Oxidase negative
• Strict aerobe
• Utilizes organic compounds other than sugars as a carbon source

Question 21

T/F- A rapidly increasing problem in hospitals and soldiers coming home from iraq/afghanistan wars is infection with multiply-resistant strains of acinetobacter baumanni?

Answer 21

True

Question 22

T/F- Gram negative rods (enterobacteria and others) are most frequently associated with infections of compromised hosts and cause a variety of infections (UTI, RTI, sepsis, device infections)?

Answer 22

True

Question 23

T/F Gram negative rods (enterobacteria and others) can be difficult to treat due to antibiotic resistance?

Answer 23

True

Question 24

T/F Gram negative rods (enterobacteria and others) are not frequently found in the environment?

Answer 24

False

Question 25

Do gram positive bacteria grow on MacConkey agar?

Answer 25

No

Question 26

T/F- enterobacteriaceae are oxidase positive?

Answer 26

False, they are all oxidase negative