Nonfermenting GN Rods

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Nonfermenting GN Rods Miscellaneous GN Rods

• MLAB 2434 Microbiology
• Keri Brophy-Martinez

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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

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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

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The Nonfermenters

• Achromobacter
• Acidovorax
• Acinetobacter
• Agrobacterium
• Alcaligenes
• Burkholderia
• Stenotrophomonas
• Chryseobacterium
• Chryseomonas
• Comamonas
• Flavimonas
• Flavobacterium

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

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Clinical Infections

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

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Clinical Infections

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

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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)

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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

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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

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Pseudomonas aeruginosaClinical Infections

• 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 (skin rash)

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Pseudomonas aeruginosaVirulence Factors

• Endotoxins
• Hemolysins
• Cytotoxins
• Proteases
• Slime
• Pili

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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

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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

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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

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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

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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.
• http//www.microbelibrary.org/library/laboratory-t
  est/2862-blood-agar-plates-and-hemolysis-non-ferme
  nting-gram-negative-rods-including-pseudomonas-aer
  uginosa