17 -chapter_21_-_non-fermenters

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

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