1. Nonfermenting GN Rods & Miscellaneous GN Rods
MLAB 2434 – 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,” “nonoxidizers”or nonsaccharolytic

3. General Characteristics of Nonfermenters (cont’d)
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. The Nonfermenters Achromobacter Methylobacterium Acidovorax Moraxella
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
Nosocomial Infections

6. Clinical Infections Risk factors Immunosuppression
Foreign body implantation
Traumatic break in a host barrier
Antibiotic therapy
Underlying disease

7. Initial Clues to Nonfermenters
Long, thin gn rods or cb
Oxidase positive (not ALL nonfermenters)
No or slow growth of MacConkey agar
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)

8. 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

9. Commonly Encountered Nonfermentative Organisms
Pseudomonas characteristics
Associated with water and moist environments
Not common as normal flora
Strict aerobe
GN rods or cb
Usually motile with polar or polar tufts of flagella
Oxidase and catalase positive
Usually grows on MacConkey agar
Usually oxidizes carbohydrates

10. Pseudomonas aeruginosa: Clinical Infections
Types of infections
Bacteremia with ecthyma gangrenosum of skin
Wound infections
Pulmonary disease (esp. in Cystic Fibrosis)
Nosocomial UTI
Endocarditis
Meningitis
Otitis externa (“swimmer’s ear”)
“Hot tub” syndrome (skin rash)

11. Pseudomonas aeruginosa: Virulence Factors
Endotoxins
Hemolysins
Cytotoxins
Proteases
Slime
Pili

12. P. aeruginosa: Laboratory identification
Beta-hemolytic on blood agar
Green metallic sheen due to production of pigment pyocyanin (bluish-green)
Most strains also produce pigment pyoverdin (yellowish-green fluorescence)
Odor described as “grape-like” or “Frito-like”

13. Honorable mentions… Pseudomonas fluorescens & Pseudomonas putida
Produces pyoverdin but not pyocyanin
Rarely causes clinical disease
Found in water and soil, usually environmental contaminants
Pseudomonas stutzeri
Wrinkled, leathery colonies that may be light yellow or brown, non- fluorescent

14. Stenotrophomonas maltophilia
Third most common nonfermenter cultured, ubiquitous in nature
Common in the hospital environment
Implicated in infections of wounds, RT, UT and blood
Frequent isolate of Cystic Fibrosis patients

15. 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
Burkholderia cepacia – most often associated with pneumonia in Cystic Fibrosis
Burkholderia pseudomallei – causes melioidosis( an aggressive pulmonary disease causing pneumonia, abscesses and septicemia)
Alcalingenes – found in water and resistant to disinfectants

16. References
Engelkirk, P. G., & Duben-Engelkirk, J. (2008). Laboratory Diagnosis of Infectious Diseases: Essentials of Diagnostic Microbiology . Baltimore, MD: Lippincott Williams & Willkins.
Kiser, K. M., Payne, W. C., & Taff, T. (2011). Clinical Laboratory Microbiology: A Practical Approach . Upper Saddle River, NJ: Pearson Education, Inc.
Mahon, C. R., Lehman, D. C., & Manuselis, G. (2011). Textbook of Diagnostic Microbiology (4th ed.). Maryland Heights, MO: Saunders.