ACINETOBACTER, STENOTROPHOMONAS, AND OTHER ORGANISMS

Question 1

Nonfermenting gram-negative bacilli
Oxidase negative
Grow well on MacConkey agar
Oxidize glucose (saccharolytic) or non-oxidizers (asaccharolytic)

Answer 1

Acinetobacter, Stenotrophomonas, and related organisms

Question 2

Primary habitat of Acinetobacter and Stenotrophomonas

Answer 2

Most often inhabit environmental niche (water or soil)
Can contaminate potable or chlorinated water

Question 3

Where Acinetobacter species were initially recovered from patients

Answer 3

Humid climates
Also colonize the skin
Human sources: sputum, urine, feces, and vaginal secretions

Question 4

Ubiquitous in nature

Answer 4

Stenotrophomonas maltophilia

Question 5

Patients most often infected by Acinetobacter spp.

Answer 5

ICU patients
Patients residing in long-term facilities

Question 6

Water organism, often found in irrigating solutions and IV solutions

Answer 6

Acinetobacter baumanii

Question 7

Risk factors for Acinetobacter spp. infection

Answer 7

Mechanical ventilation
Tracheostomy
Central venous catheterization
Enteral feeding

Question 8

Virulence factors of Acinetobacter spp.

Answer 8

Lipopolysaccharide capsule
Survival in dry environments
Adherence to mucosal epithelium via fimbriae

Question 9

Risk factors for Stenotrophomonas maltophilia infection

Answer 9

Central venous catheterization
Cystic fibrosis
Residing in the ICU
Malignancy
Mechanical ventilation
Neutropenia
Previous broad-spectrum antibiotic therapy
Recent surgery
HIV infection

Question 10

Plump coccobacilli
Tend to resist alcohol decolorization (may appear gram-positive)
May be mistaken for Neisseria spp. due to similar microscopic appearance

Answer 10

Gram stain appearance of Acinetobacter spp.

Question 11

Short to medium-sized straight rods

Answer 11

Gram stain appearance of Stenotrophomonas maltophilia

Question 12

Media of Choice for Cultivation (Acinetobacter spp., Stenotrophomonas maltophilia)

Answer 12

Routine media: trypticase soy agar with 5% sheep blood agar (BA) and chocolate agars
Grow well in MacConkey agar (Mac)
Blood culture systems
Nutrient broths: thioglycollate and brain-heart infusion

Question 13

Smooth, opaque, raised, creamy, and smaller than Enterobacteriaceae
Some genospecies are beta-hemolytic

Answer 13

Acinetobacter spp. on BA

Question 14

Non-lactose fermenter
Colonies exhibit a purplish hue that may be mistaken as a lactose fermenter

Answer 14

Acinetobacter spp. on MacConkey agar

Question 15

Large, smooth, glistening colonies with uneven edges
Lavender-green to light purple pigment
Greenish discoloration underneath growth
Ammonia smell

Answer 15

Stenotrophomonas maltophilia on BA

Question 16

Non-lactose fermenter

Answer 16

Stenotrophomonas maltophilia on MacConkey