Nonfermenting Gram Neg Rods

Question 1

Nonfermenting GNR are:

Answer 1

1) Pseudomonas
2) Acinetobacter
3) Stenotrophomonas
4) Burkholderia
5) Moraxella / Oligella
6) Alcaligenes / Achromobacter

Question 2

Fermentation test (O/F Medium)

Answer 2

1) Low peptone
–Principal: Some organisms produce acid from carbohydrate only in the presence of O2
–Low peptone content keeps the acid production from being masked by the alkaline products of peptone
–1% carbohydrate w/ bromothymol blue indicator
–Inoculate two tubes: one open to air and one sealed
–Check for carbohydrate metabolism via yellow color

Results (Closed/Open):
*Y/Y = Ferment / Oxidize (Enterobacteriaceae)
*G/Y = Oxidizer only (Pseudomonas, Acinetobacter)
*G/G = Nonfermenter / Nonoxidizer (Alcaligenes)

Question 3

Nonoxidizers are also called…

Answer 3

Asaccharolytic

Question 4

Identifying Nonfermenters

Answer 4

1) Growth on MAC
2) Oxidase
3) Oxidizer vs Nonoxidizer

Question 5

Pseudomonas

Answer 5

1) GNR/GNCB
2) Motile
3) Ox+
4) Cat+
5) MAC+ NLF
6) Oxidizer (majority)

Question 6

P. aeruginosa

Answer 6

1) Most common nonfermenter
2) 5-15% nosocomial infections
3) Beta-hemolytic
4) Oxidizes glucose and citrate
5) Pyocyanin / Pyoverdin (fluoresces under short-wavelength UV light)
6) Inherently resistant to many Abx
–Treat with aminoglycosides, pip/tazo, 3rd/4th gen cephalosporins, fluoroquinolones
7) Can grow at 42C
8) Xylose+

Question 7

P. aeruginosa virulence factors

Answer 7

1) Endotoxin
2) H antigen
3) Pili
4) Capsule
5) Exotoxins
–Exotoxin A like Dipth toxin -> blocks protein synthesis

Question 8

P. fluoroescens / P. putida

Answer 8

-Rare but can cause disease from:
–contaminated blood products, urine, cosmetics, hospital equipment, etc
-Don’t grow at 42C or produce pyoverdin
-Gelatin hydrolysis is differentiating test
–P. putida = / P fluoro +

Question 9

Acinetobacter

Answer 9

1) A. baumanii
–Glu oxidizer (saccharolytic)
–Nonhemolytic
–UTIs, Pneumonia, bronchitis, endocarditis (22% mortality), septicemia, cellulitis, meningitis (chemo patients)
2) A. lwoffii
–Glu nonoxidizer (asaccharolytic)
–Nonhemolytic

Question 10

Acinetobacter characterisitcs

Answer 10

-Soil, skin, hospital surfaces
-45% of hospital patients are colonized
-Highly resistant
-Opportunistic
-Strict aerobe
-GNCB
-Ox=
-Cat+
-Nonmotile

Question 11

Stenotrophomonas

Answer 11

-Water, sewage, plants
-Frequent nosocomial contaminant
-Can quickly colonize resp tract
-Inherently resistant to many abx
-Endocarditis, resp tract infections

Question 12

Stenotrophomonas characteristics

Answer 12

-Nonfermentive GNR
-Ox=
-Cat+
-DNAase+
-Esculin+
-Gelatinase+
-Lysine decarb+
-ONPG+

Drug of choice: SXT

Question 13

Burkholderia

Answer 13

B. cepacia group
-low-grade nosocomial pathogen
-Pneumonia in CF patients (3% are infected)
-Chronic granulomatous disease
-Other infections

Question 14

B. cepacia characteristics

Answer 14

1) BAP+ but needs transfer w/in 3 days
2) MAC+
3) Special media
–PC (P cepacia)
–OFPBL (oxidative-ferm polymyxin B bacitracin lactose)
–BCSA (B cepacia selective agar)
4) Slow Ox+
5) Glu+, Mal+, Lac+, Man+ oxidizers
6) Lysine decarb+
7) ONPG +

Question 15

Burkholderia mallei

Answer 15

Glanders
-primarily livestock disease
-Severe local pulmonary infection
-Bioterrorism agent

Question 16

B. mallei characteristics

Answer 16

1) Nonmotile
2) GNCB
3) Nonpigmented colonies
4) MAC+/=
5) Ox+/=
6) Glu oxidizer
7) Nit+
8) ADH+

Question 17

B. pseudomallei

Answer 17

Meloidosis
-Aggressive granulomatous pulmonary disease
-Ingestion, inhalation, or inoculation
-Metastatic abscess formation in lungs, septicemia, local infections
-Pneumonia
-Water/ soil southeast Asia

Question 18

B. pseudomallei characteristics

Answer 18

1) Wrinkled colony
2) Bipolar gram stain
3) Lac+ (differentiate b/t P. stutzeri)
4) Ashdown neutral red media w/ colistin = pink colonies

-SXT and fluoroquinolones

Question 19

Moraxella osloensis

Answer 19

Normal Genitourinary flora
-Can be confused / GC
-Ox+
-Glu=