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Chapter 21 NON-FERMENTERS
Describe and interpret different reactions of the O -F media.
Differentiate Enterobacteriaceae from non-fermenting gram-negative bacilli.
List the organisms classified as fluorescent pseudomonads and explain why they are grouped together.
Explain the clinical significance of Pseudomonas aeruginosa .
List the pigments produced by Pseudomonas aeruginosa .
Identify Pseudomonas based on biochemical reactions and colony morphology.
Describe the colony morphology and gram stain morphology of Pseudomonas aeruginosa .
Describe the colony morphology of Pseudomonas stutzeri .
OBJECTIVES
CLUES THAT INDICATE A NON-FERMENTER
Lack of fermentation
TSI = Alk/Alk
Positive cytochrome oxidase
TSI
GENERAL CHARACTERISTICS
Gram negative bacilli
Ubiquitous
Opportunistic pathogens
Obligate aerobes
Slow growers
BIOCHEMICAL CHARACTERISTICS
Oxidase positive
Non-lactose fermenters
Motile (in most cases)
Utilization of glucose in the O -F media tests
O-F TUBES
Purpose
Substrate utilization
Oxidative
Fermentative
Interpretation
Fermenter
Non-fermenter (Oxidase)
Non-utilizer
O-F TUBES
Fermenter
Oxidizer (Non-fermenter)
Assaccharolytic
ORGANISMS OF CLINICAL INTEREST
PSEUDOMONAS AERUGINOSA
EPIDEMIOLOGY
Found in soil, water & plants
Hospital environments
Not part of the human normal flora
CLINICAL SIGNIFICANCE
Respiratory infections
Ear infections “Swimmer’s ear”
Wound infections in burn patients
Respiratory infections in cystic fibrosis patients
UTIs
Eye infections
LABORATORY FINDINGS
Gram stain Gram negative Long, thin bacilli
COLONY MORPHOLOGY
Grows on MAC and BAP
Spready, flat colonies with serrated edges
Metallic sheen
Bluish -green, red or brown pigmentation
Colonies are often beta-hemolytic on BAP
Grape-like or corn taco-like odor
Mucoid colonies see in cystic fibrosis patients
MAC = non-fermenter
BIOCHEMICAL CHARACTERISTICS
Oxidase positive
TSI = Alk/Alk
Bluish-green, red or brown pigment seen on Mueller -Hinton or trypticase soy agar
Growth at 42°C
PSEUDOMONAS STUTZERI
CLINICAL SIGNIFICANCE
Opportunistic pathogen
Exposure of contaminated medical devises and solutions
COLONY MORPHOLOGY
Dry, wrinkled colonies
Buff to brown in color
Non-lactose fermenter
BIOCHEMICAL CHARACTERISTICS
Oxidase positive
Glucose oxidizer
Grows at 42°C
Nitrate reduced to nitrogen gas (4+ reaction)
All decarboxylases negative
BURKHOLDERIA (PSEUDOMONAS)
CEPACIA
EPIDEMIOLOGY
Found in plants, soil and water
Able to survive in medical devises and solutions (including disinfectant solutions)
Infections result from direct contact with:
Contaminated food
Medical solutions
Medical devises
CLINICAL SIGNIFICANCE
Nosocomial infections
Often isolated from cystic fibrosis patients
Opportunistic pathogen
LABORATORY FINDINGS
Gram stain Small gram negative rod
Colony morphology May appear as sulfur yellow or may be colorless
Convex colonies
Biochemical characteristics Motile
Oxidase negative or weak positive
Glucose oxidizer
Lysine decarboxylase positive
Ornithine decarboxylase positive
Arginine dehydrolase negative
Review Mahon, chapter 21
Complete AUMoodle Review
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