CH 21: Non-glucose fermenting and miscellaneous GNB

Oxidation vs fermentation

• yellow color change means using sugars

• oxidation = uses oxygen, fermentation = no oxygen

• asaccharolytic

  • don’t use sugars as food source

General characteristics of glucose (=) GNB

• ubiquitous and found in most environments

  • soil, water, plants, decaying vegetation, and food

• prefer moist environments

  • nebulizers, catheters, saline fluids

• rarely part of normal host microbiota

• testing

  • alkaline butt in TSI and KIA

  • No acidification of fermentative tube in

    O/F Glucose test

Pseudomonas spp.

• largest percentage of non-fermenters isolated from clinical specimens

• morphology

  • flat, spreading colonies

  • usually beta hemolytic

• testing

  • oxidase (+)

  • motile

  • oxidizer

Pseudomonas aeruginosa

• most clinically significant

  • biofilm

• grows in MANY water sources: pools, hot tubs, humidifiers, ventilation

• UTI, wound infx, septicemia, meningitis, pneumonia

• most known for:

  • otitis externa: ‘swimmer’s ear’

  • keratitis

    • inflammation of the conjunctiva

    • bright green

    • sleeping in CL

  • infx after burns

    • wash in sterile saline

Pseudomonas aeruginosa - morphology

• produces two pigments

  • pyoverdin - green and fluorescent

  • pyocyanin - blue pigment

• metallic sheen

  • ‘oil spill’

• fruity, grape-like odor

• known for being incredibly antibiotic resistant

Acinetobacter baumannii

• ubiquitous in environment

  • water, soil, food products

• causes nosocomial infx

  • ventilators, humidifiers, catheters

  • UTIs, pneumonia

  • immunocompromised pts

• morphology

  • gram-variable coccobacilli

  • purple on MAC

  • glucose oxidizer

  • usually oxidase (=)

Stenotrophomonas maltophilia

• ubiquitous in environment

  • water, sewage, and plant material

• most known for endocarditis after IV drug abuse or heart sx

  • wound infx, cellulitis, and bacteremia

• inherently resistant to several drug cats. most used for GNB

• morphology

  • lavender to green colonies on BAP

  • ammonia-like odor

  • oxidase (=)

  • asaccharolytic

Burkholderia cepacia

• plant pathogen arisen as opportunistic hm pathogen

  • immunocompromised

• causing respiratory infx in pts w/ cystic fibrosis or chronic granulomatous dx

• morph/testing

  • yellow-green pigment

  • oxidizes glucose, lactose, maltose, and mannitol

  • weak/slow oxidase (+)

Burkholderia mallei

• Glander’s dx in horses, donkeys, and other mammals

  • rare in humans since 1940s

Burkholderia pseudomallei

• causes meliodosis

Ingestion, inhalation, or direct contact

with soil

○ Pulmonary, skin, and blood infections

• Category B bioterrorism agent

● Morphology/Testing

○ Wrinkled colonies

○ Earthy odor

○ Oxidase (+

Alcaligenes faecalis

• grow in fresh water sources

  • tap, hot tubs, chlorinated pools, dialysis fluids

• usually in hospitalized pts

  • UTIs, wound infx, respiratory infx

• morphology

  • distinctive spreading colonies, greenish/purple hue

  • green apple smell

  • oxidase (+)

  • asaccharolytic

Elizabethkingia meningoseptica

• meningitis and septicemia in newborns

• morphology

  • yellow pigment on BAP

  • oxidase (+)

  • DNase (+)

  • glucose oxidizer