WEEK 13: NONFERMENTING GRAM NEGATIVE BACILLI Flashcards
a. Grow in MacConkey as colorless colonies
b. Fail to acidify O-F Media, overlaid with mineral oil
c. Fail to acidify TSI Agar
d. Most isolates is Oxidase Positive
e. Resistance to a variety of classes of
antimicrobial agents (beta lactamase and aminoglycosides)
NONFERMENTING GRAM NEG. BACILLI
No change in color in both tube in O-F Media. Nonsaccharolytic organisms.
Alcaligenes, Oligella
Change in color in tubes
w/out mineral oil (Open tube)
Oxidative
Organisms that are negative in Oxidase Test (colorless)
Acinetobacter and Stenotrophomonas
Organisms that are positive in Oxidase Test (dark purple)
Pseudomonas and Burkholderia
- Most commonly isolated species
▪ 75% of nonfermenters in nosocomial bacteremias and 5% to 15% of nosocomial infections - Causes bacteremia, wound infection, pulmonary disease (Cystic fibrosis patients), UTI, endocarditis, meningitis
- Otitis media and Jacuzzi/hot tub syndrome
Pseudomonas aeruginosa
Pseudomonas aeruginosa can cause bacteremia leading to?
ecthyma gangrenosum
most important exotoxin in Pseudomonas aeruginosa; blocks protein synthesis
Exotoxin A
Polysaccharide polymer in mucoid strains
Alginate
- Strict aerobic
- Pigmented
- Fruity, Grapelike or
“corn tortilla-like” Odor
(2-aminoacetophenone) - Growth at 42°C
- Grows in Cetrimide Agar
- Acetamide Positive
Pseudomonas aeruginosa
Fluorescein (Pyoverdin)
P.fluorescens/P. putida
Pyomelanin
P. stutzeri
- Bluish-green, red, or brown pigmentation, β-hemolytic in BAP
- Bluish-green, red, or brown diffusible pigment in Mueller Hinton
Pseudomonas aeruginosa
Organism that is often mistaken as Neisseria
Acinetobacter spp.
- Associated with ventilators, humidifiers, catheters, etc.
- Opportunistic (1-3% of all nosocomial infection, 2nd most commonly isolated non-fermenter); burns, trauma
- About 25% of adults present in skin; 7% in pharynx
- Ubiquitous; found in soil, water, foodstuffs
Acinetobacter spp.
- Saccharolytic (glucose oxidizing), nonhemolytic strains.
- may exhibit purplish hue (due to lactose
oxidation) - appears with a blue-grey (cornflower blue) center in EMB.
A. baumannii
Asaccharolytic, nonhemolytic strains.
A. lwoffii
β-hemolytic strains.
A. haemolyticus
Plump, paired gram negative coccobacilli
Acinetobacter spp.
- Contaminants in blood drawing equipment (collection tubes, disinfectants, transducers, venous catheters, etc.)
- Opportunistic (3rd most commonly isolated among nonfermenters)
- Intrinsic resistance commonly used antibacterial agent (aminoglycosides and beta lactams)
Stenotrophomonas maltophilia
- Oxidase negative
- Catalase, Dnase positive
- Esculin and Gelatin hydrolysis (+)
- Lysine decarboxylase positive
Stenotrophomonas maltophilia
- Pneumonia in patients with cystic fibrosis or chronic granulomatous disease
- Isolated from irrigation fluids, anesthetics, nebulizers, detergents and disinfectants.
- Onion bulb rot in plants and foot rot in humans
- Intrinsic resistance to antibiotics
Burkholderia cepacia
Organism that is positive in Acetamide Utilization
Pseudomonas aeroginusa
▪ “Melioidosis” (pulmonar disease) formation of abscess
- Bipolar staining (safety pin) in Gram Stain
- Smooth to wrinkled colonies in BAP
- Wrinkled and deep pink in Ashdown media
- “Earthy odor”
- “Sniffing” of plate is discouraged (work on BSC)
▪ Culture- Ashdown media
Burkholderia pseudomallei
- Smooth, non-wrinkled and slightly raised; dirtlike odor in BAP
- NLF; become dark pink to red after 4-7 days in Mac
- Most strains are ONPG positive
- Specific selective media (PC, OFPBL, BCSA)
- Produces a nonfluorescing yellow/green pigment
Burkholderia cepacia
- lavender green pigment in BAP
- Ammonia-like smell
- Oxidizes glucose: W(+/-)
- Oxidizes maltose: S(+)
Stenotrophomonas maltophilia
“Associated with patients with CF (cystic fibrosis) and CGD (chronic granulomatous disease)
Burkholderia gladioli
Selective and differential media used for Pseudomonas aeroginusa that enhances pigment (pyoverdid and pyocyanin)
Cetrimide Agar
▪ Glanders- zoonosis affecting horses, mules, donkeys. Formation of nodular lesions in lungs. Coughing, fever and release of infectious nasal discharge.
▪ Potential bioterrorist agent
▪ Nonmotile; non-pigmented colonies; no distinct odor
Burkholderia mallei
Good growth at both 35°C and 42°C
Pseudomonas aeroginusa
Stenotrophomonas maltophilia
No growth at 42°C but good growth at 35°C
Pseudomonas fluorescens
Pseudomonas putida
