Transcript Chapter 16 - Enterobacteriaceae

Nonfermenting GN
Rods & Miscellaneous
GN Rods
MLAB 2434 – Microbiology
Keri Brophy-Martinez
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
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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
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The Nonfermenters
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Achromobacter
Acidovorax
Acinetobacter
Agrobacterium
Alcaligenes
Burkholderia
Stenotrophomonas
Chryseobacterium
Chryseomonas
Comamonas
Flavimonas
Flavobacterium
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Methylobacterium
Moraxella
Weeksekka
Ochrobactrum
Oligella
Pseudomonas
Psychrobacter
Roseomonas
Shewanella
Sphingobacterium
Clinical Infections
Septicemia
 Meningitis
 Osteomyelitis
 Wound infections following surgery
or trauma
 Nosocomial Infections
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Clinical Infections
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Risk factors
Immunosuppression
 Foreign body implantation
 Traumatic break in a host barrier
 Antibiotic therapy
 Underlying disease
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Initial Clues to
Nonfermenters
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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)
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Treat with aminoglycosides, quinolones and antipseudomonal penicillins ( ticarcillin, piperacillin)
Nonfermenter
Organization
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Nonfermenters are grouped according
to three characteristics
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Growth on MacConkey
• Not all nonfermenters grow on MAC
• All nonfermenters that grow on MAC are lactose negative
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Oxidase reaction
OF test
Commonly Encountered
Nonfermentative Organisms
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Pseudomonas characteristics
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Associated with water and moist
environments
• Not common as normal flora
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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
Pseudomonas aeruginosa:
Clinical Infections
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Types of infections
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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)
Pseudomonas aeruginosa:
Virulence Factors
Endotoxins
 Hemolysins
 Cytotoxins
 Proteases
 Slime
 Pili
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P. aeruginosa:
Laboratory identification
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Beta-hemolytic on blood agar
Green metallic sheen due to
production of pigment pyocyanin
(bluish-green)
Most strains also produce
pigment pyoverdin (yellowishgreen fluorescence)
Odor described as “grape-like”
or “Frito-like”
Honorable mentions…
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Pseudomonas fluorescens & Pseudomonas
putida
 Produces pyoverdin but not pyocyanin
 Rarely causes clinical disease
 Found in water and soil, usually
environmental contaminants
Pseudomonas stutzeri
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Wrinkled, leathery colonies that may be light
yellow or brown, non- fluorescent
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
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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
References
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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/laboratorytest/2862-blood-agar-plates-and-hemolysis-nonfermenting-gram-negative-rods-including-pseudomonasaeruginosa