Chapter 22 Nonfermenting G Rods

1
Chapter 22 Nonfermenting G- Rods
Miscellaneous G- Rods

• MLAB 2434 Clinical Microbiology
• Keri Brophy-Martinez

2
General Characteristics of Nonfermenters

• Nonfermentative organisms that break down
  carbohydrates oxidatively (aerobically) are also
  called oxidizers or saccharolytic
• Organisms that are NOT able to break down
  carbohydrates fermentatively or oxidatively are
  called biochemically inert, nonoxidizersor
  nonsaccharolytic

3
General Characteristics of Nonfermenters (contd)

• Nonfermenters are ubiquitous in the environment
• Predominantly opportunistic
• Also isolated in hospitals from nebulizers,
  dialysate fluids, saline, and catheter devices
• Somewhat resistant to disinfectants antibiotics

4
Nonfermenter Clinical Infections

• Nonfermenters make up 15 of all isolates of g-
  rods
• Achromobacter
• Acidovorax
• Acinetobacter
• Agrobacterium
• Alcaligenes
• Burkholderia
• Stenotrophomonas
• Chryseobacterium
• Chryseomonas
• Comamonas
• Flavimonas
• Flavobacterium

• Methylobacterium
• Moraxella
• Weeksekka
• Ochrobactrum
• Oligella
• Pseudomonas
• Psychrobacter
• Roseomonas
• Shewanella
• Sphingobacterium

5
Clinical Infections

• Septicemia
• Meningitis
• Osteomyelitis
• Wound infections following surgery or trauma

6
Nonfermenter Clinical Infections (contd)

• Risk factors for nonfermenter infection
• Immunosuppression
• Foreign body implantation
• Traumatic break in a host barrier
• Antibiotic therapy
• Underlying disease

7
Nonfermenter Clinical Infections (contd)

• Pseudomonas infection of skin and nail

8
Biochemical Characteristics of Nonfermenters

• Nonfermenters vary in biochemical and morphologic
  characteristics
• All are nonreactors on TSI slants
• Oxidative vs. fermentative properties can be
  demonstrated with use of OF (oxidative/fermentativ
  e) medium

9
Initial Clues to Nonfermenters

• Long, thin g- rods or cb
• Oxidase positive (not ALL nonfermenters)
• Nonreactive in 24 hours on commercial kit systems
• TSI nonreactive
• Resistant to antibiotics ( penicillin, ampicillin
  cephalosporins)
• Treat with aminoglycosides, quinolones and
  anti-pseudomonal penicillins ( ticarcillin,
  piperacillin)

10
Nonfermenter Organization

• Nonfermenters are grouped according to three
  characteristics
• Growth on MacConkey
• Not all nonfermenters grow on MAC
• All nonfermenters that grow on MAC are lactose
  negative
• Oxidase reaction
• OF test

11
Commonly Encountered Nonfermentative Organisms

• Pseudomonas characteristics
• Associated with water and moist environments
• Strict aerobe
• G- rods or cb
• Usually motile with polar or polar tufts of
  flagella
• Oxidase and catalase positive
• Usually grows on MacConkey agar
• Usually oxidizes carbohydrates

12
Commonly Encountered Nonfermentative Organisms
(contd)

• Pseudomonas aeruginosa
• Most common nonfermenter isolated from clinical
  specimens
• Not common as normal flora

13
Pseudomonas aeruginosa

• Types of infections
• Bacteremia with ecthyma gangrenosum of skin
• Wound infections
• Pulmonary disease (esp. in Cystic Fibrosis)
• Nosocomial UTI
• Endocarditis
• Meningitis
• Otitis externa (swimmers ear)
• Hot tub syndrome

14
Commonly Encountered Nonfermentative Organisms
(contd)

• Virulence factors for P. aeruginosa
• Endotoxins, hemolysins, proteases, slime, pili etc

15
Commonly Encountered Nonfermentative Organisms
(contd)

• P. aeruginosa identifying characteristics
• Beta-hemolytic on blood agar
• Green metallic sheen due to production of pigment
  pyocanin (bluish-green)
• Most strains also produce pigment pyoverdin
  (yellowish-green fluorescence)
• Odor described as grape-like or Frito-like

16
Commonly Encountered Nonfermentative Organisms
(contd)

• P. aeruginosa P. aeruginosa
• on MacConkey producing pyoverdin

17
Commonly Encountered Nonfermentative Organisms
(contd)

• Pseudomonas fluorescens Pseudomonas putida
• Produces pyverdin but not pyocyanin
• Rarely causes clinical disease
• Found in water and soil, usually environmental
  contaminants

18
Commonly Encountered Nonfermentative Organisms
(contd)

• Stenotrophomonas maltophilia
• Third most common nonfermenter cultured,
  ubiquitous in nature
• Common in the hospital environment
• Implicated in infections of wounds, RT, UT and
  blood

19
Other Nonfermenters

• Acinetobacter found in hospital environments
  can cause opportunistic infection, skin/vaginal
  normal flora. On BAP transluscent-opaque, MAC
  colorless. On gram stain, short plump gncb
• Pseudomonas stutzeri wrinkled, leathery
  colonies that may be light yellow or brown, non-
  fluorescent
• Burkholderia cepacia most often associated with
  pneumonia in Cystic Fibrosis
• Burkholderia pseudomallei causes melioidosis
• Alcalingenes found in water and resistant to
  disinfectants