Non-fermentative Gram(-) bacilli Flashcards
General characteristic of Non-fermenters:
Fail to:
- acidify an oxidative-fermentative (OF)
medium when it is overlaid with mineral oil
- acidify triple sugar iron agar (TSIA) butt
Nonoxidizers or?
Asaccharolytic
General characteristic of Non-fermenters:
- prefer and grow in aerobic environment
- some oxidize carbohydrates as source of energy
- prefer moist environment (e.g: from nebulizers)
- can easily colonize hospitalized px
A feature of Non-fermenters that greatly differentiates them from Enterobacteriaceae
Oxidase +
Series of infections usually associated with Non-fermenters gram (-) bacilli
Septicemia
Meningitis
Osteomyelitis
Wound infections following surgery or trauma
Biochemical Characteristic & Identification:
Fermenters
• (+): acid (yellow) butt
• (+): acid or alkaline (red) slant on TSIA or KIA
within 18 h incubation
Biochemical Characteristic & Identification:
Non-fermenters
- fail to ferment carbohydrates
- No acid production in the slant or butt of TSIA or KIA
- no change in the butt & slant may produce an alkaline (red) slant
Biochemical Characteristic & Identification:
“true” fermenters
fastidious (e.g., Pasturella multocida) • do not easily acidify the butt or slant of a TSIA like other fermenters • but do show reactions if more enriched media are used
3 common test for Non-fermenters
- growth on MAC agar
- oxidase reaction
- glucose O-F test
4 groups of non-fermenters make up most isolates
routinely seen in clinical laboratories:
Pseudomonas aeruginosa
Acinetobacter spp.
Burkholderia spp.
Stenotrophomonas maltophilia
ID of non-fermenters:
based on the site from which they
have been isolated
if they have been recovered from a normally sterile site in pure culture
- requires definitive ID &
susceptibility testing
ID of non-fermenters:
based on the site from which they
have been isolated
if acquired from a nonsterile site in which
3 or 4 other bacterial species are also
present
- genus identification might be
appropriate thru biochemical test.
e.g: MAC agar, indole, motility, and glucose utilization
MALDI-TOF mass spectrometry
a method for the identification of
bacteria & fungi from colonies based on
analysis of the unique spectra of their peptides when separated in a mass spectrophotometer
This genus has the largest percentage of all non-fermenters isolated from clinical specimens
Pseudomonas
-specifically pseudomonas aeruginosa
Characteristic common to most Pseudomonads
- gram (-) bacillus/ coccobacillus
- strictly aerobic
- motile w/ polar flagellum or polar tuft of flagella
- oxidase (+)
- catalase (+)
- usually grows on MAC agar
Pseudomonas Fluorescent Group:
Pseudomonas aeruginosa
- is the leading cause of nosocomial
respiratory tract infections - accounts for up to 6% of all bacteremias &
as many as 75% of nosocomial bacteremias - is the 3rd most common cause of gram (-)
bacillary bacteremia (after E.coli and K. pneumoniae) - a common cause of lung infections in people with CF
P. aeruginosa is commonly isolated from
Sterile body site: blood, pleural fluid, joint fluid, tissues, CSF (constituting a true infection)
less serious conditions associated with P.aeruginosa
Otitis externa and infections of nail beds
or in swimmers or divers called as Jacuzzi or hot tub syndrome
A condition caused by P. aeruginosa characterized by necrotizing rash in drivers or swimmers
Jacuzzi or hot tub syndrome
Most important exotoxin produced by P. aeruginosa
Exotoxin A - cytotoxic; blocks protein synthesis
Identifying characteristics of
P. aeruginosa
production of:
- pyoverdin (yellow-green/ brown)
- pyocyanin (blue)
- pyorubin (red)
- pyomelanin (brown or black)
It is a yellow-green or yellow-brown water soluble pigment produce by P. aeruginosa
Pyoverdin
- fluoresces under short-wavelength UV light
A blue water-soluble pigment that when combined w/ pyoverdin produces green color colonies in MHA (mueller hinton agar)
Pyocyanin
What is the color of P.aeruginosa colonies in MHA agar
green-colored colonies
What causes the green coloration of colonies of P. aeruginosa in MHA agar
- production of pyoverdin and pyocyanin
P.aeruginosa is resistant to these antibiotics
- Penicillin
- Ampicillin
- first- & second-generation cephalosporins
- trimethoprim-sulfamethoxazole
- Chloramphenicol
- tetracyclines
P.aeruginosa is susceptible to these antibiotics
- Aminoglycosides
- Semisynthetic penicillins: piperacillin and
ticarcillin
-third- and fourth generation cephalosporins
(ceftazidime and cefepime, respectively) - carbapenems (except ertapenem)
- fluoroquinolones
Treatment necessary for severe P.aeruginosa
Combination therapy
- Synthetic pencillins or carbapenems w/ aminoglycosides
Test used to differentiate P. fluorescens and P. putida
Gelatin hydrolysis
- P. putida (-)
- P. fluorescens (+)
Pseudomonas Fluorescent Group:
P. fluorescens
-isolated from blood culture bottles
- pyocyanin (-)
- pyoverdin (+)
- responsible for clusters
of pseudobacteremia, probably related to
contaminated catheters & catheter-related
devices
Pseudomonas Fluorescent Group:
P. putida
- catheter-related sepsis
in patients with cancer - pyocyanin (-)
- pyoverdin (+)
Pseudomonas Fluorescent Group:
both P.fluorescens & P. putida
- grows as 4 celcius
- cannot grow at 42 celcius
- linked to transfusion-associated septicemia
- cannot reduce nitrate to nitrite
- can produce acid from xylose
Pseudomonas Nonfluorescent Group:
P. stutzeri
- recognizable macroscopic appearance of wrinkled, leathery, adherent colonies that produces light-yellow or brown pigment.
Biochemical test that specifically distinguish P.stutzeri from other Pseudomonanas spp.
Combination of:
- Starch hydrolysis (+) and ADH (-)
Pseudomonas Nonfluorescent Group:
P. mendocina
- produces non-wrinkled, flat colonies
- yellowish-brown pigment
- motile (single polar flagellum)
- pigmentation (variable): smooth buttery appearance
Pseudomonas pseudoalcaligenes &
Pseudomonas alcaligenes
- oxidase (+)
- biochemically (-)
- capable of reduction of nitrates to nitrites
- motile by polar flagellum
Test used to differentiate P. pseudoalcaligenes and P. alcaligenes
ADH
- P. pseudoalcaligenes (+)
- P. alcaligenes (-)
Definitive differentiation of bacterial organisms.
MALDI-TOF and DNA sequencing
Pseudomonas luteola &
Pseudomonas oryzihabitans
- oxidase (-)
- catalase (+)
- motile, grow on MAC agar
- oxidize glucose (+)
- produce nondiffusible yellow pigment
- produce wrinkled or rough colonies at 48 hrs.
Acinetobacter spp.
- 45% of patients with a tracheostomy may be colonized - Ventilator-associated pneumonia and sepsis due to A. baumannii have a high mortality rate
Test used to differentiate A. baumannii and A. iwoffii
A. baumannii - glucose (+)
A. iwoffii - glucose (-)
- both are nonhemolytic strain
Acinetobacter Identifying characteristic
- oxidase (-)
- nonmotile
- catalase (+)
- resist decolonization & retain the crystal
violet stain
Characteristic of Acinobacter that could lead to misidentifiication of the certain bacteria
-resistance to decolorization & retention of crystal violet stain
Acinetobacter spp produces _______ hue that resembles lactose-fermenting bacterium
PURPLISH HUE
Stenotrophomonas maltophilia:
identifying characteristic
- oxidase (-)
- catalase (+)
- BLUISH colonies on MAC agar
Drug of choice for most Stenotrophomonas maltophilia infection.
SXT - Trimethoprim/sulfamethoxazole
Risk factors for S. maltophilia
- immunosppression
- hospitalization, presence of a central venous catheter (CVC)
Burkholderia cepacia Complex
- usually associated with
pneumonia in patients with CF or CGD - cause endocarditis, pneumonitis, UTIs, osteomyelitis, dermatitis, and other wound infections resulting from the use of contaminated water
Best selective medium for isolating B.cepacia
-BCSA
most effective in reducing overgrowth while maintaining good recovery of B.cepacia where non-wrinkled colonies are observed.
Which biochemical tests are needed to differentiate Burkholderia cepacia from S. maltophilia? *
A. Pigment on blood agar, oxidase, DNase
B. Pigment on MacConkey agar, flagellar stain, motility
C. Glucose, maltose, lysine decarboxylase
D. TSI, motility, oxidase
- A Pigment on blood agar, oxidase, DNase
Burkholderia mallei
- Causes “glanders”
- nonmotile
- oxidase (-)
- a potential bioterrorism agent
-broth microdilution with Brucella broth: as
recommended by CLSI - a potential bioterrorism agent
Burkholderia pseudomallei
- causes MELIOIDOSIS/ Whitmore’s
disease
most common presentation: orbital
cellulitis, dacryocystitis, & draining abscesses
Burkholderia pseudomallei: Identifying characteristic
-uses lactose
- Selective medium: ASHDOWN MEDIUM (with colistin)
- deep pink colonies because of the
absorption of neutral red in the medium + earthy odor
is an infectious disease that is caused by the bacterium Burkholderia mallei. While people can get the disease, glanders is primarily a disease affecting horses. It also affects donkeys and mules and can be naturally contracted by other mammals such as goats, dogs, and cats.
CGD bacteremia endocarditis glanders melioisis none of the choices
- Glanders
(a respiratory tract zoonosis
primarily affecting livestock such as horses, mules, &
donkeys)
A 20-year-old horse groomer exhibited a“GLANDERS-like” infection. His history indicated he had suffered several open wounds on his hands 2 weeks before the swelling of his lymph nodes. A gram-negative rod was recovered from a blood culture that grew well on blood and McConkey agars. Most of the biochemical tests were negative, including the cytochrome oxidase test. What is the most likely identification?
A. Burkholderia mallei
B. Pseudomonas aeruginosa
C. Pseudomonas stutzeri
D. Burkholderia pseudomallei
- A. Burkholderia mallei
Which organism is associated with the disease MELIOIDOSIS? *
a. Burkholderia ralstonia
b. Burkholderia pseudomallei
c. Burkholderia mallei
d. Burkholderia cepacia
- B Burkholderia pseudomallei
MELIOIDOSIS or Whitmore’s disease
MELIOIDOSIS or Whitmore’s disease
an aggressive,
granulomatous, pulmonary disease
caused by ingestion, inhalation, or inoculation of
the organisms, with METASTATIC ABSCESS FORMATION
in lungs and other viscera
= overwhelming septicemia
a potential bioterrorism agent(its occurrence should be reported to local or state public health depts)
Burkholderia mallei Pseudomonas stutzeri Oligella ureolytica Psychrobacter Moraxella spp.
-A. Burkholderia mallei
Members of the family Moraxellaceae
Moraxella, Oligella, and Psychobacter
Identifying characteristic:
Moraxella, Oligella, and Psychobacter
- nonmotile
- strongly oxidase (+)
- asaccharolytic
• strictly aerobic
• usually susceptible to penicillin
• are opportunists
Oligella:
O. urethralis & O. ureolytica
do not grow on MAC agar • are nonoxidative • phenylalanine deaminase (PDA) + • oxidase (+) • nitrate & nitrite + with gas formation • susceptible to penicillin
A motile organism by means of its peritrichous flagella, that causes bacteremia in AIDS patients is? *
O. urethralis
O. ureolytica
Stenotrophomonas maltophilia
Burkholderia mallei
- O. ureolytica
Identifying characteristic between:
O. urethralis & O. ureolytica
O. ureolytica
- motile
- peritrichous flagella
- bacteremia in AIDS
O. urethralis
- non-motile
- genitourinary tract commensal
Differentiation of Stenotrophomonas maltophilia and Burkholderia cepacia is best accomplished by which of the following tests? *
a. Oxidase test
b. Maltose and glucose medium
c. Tyrosine-enriched heart infusion agar
d. Growth at 42 C
a. Oxidase test
Which tests are most appropriate to differentiate between Pseudomonas aeruginosa and Pseudomonas putida? *
A. Oxidase, motility, pyoverdin
B. Oxidase, motility, lactose
C. Oxidase, ONPG, DNase
D. Mannitol, nitrate reduction, growth at 42°C
D. Mannitol, nitrate reduction, growth at 42°C
- P.putida
- cannot grow on 42°C temp.
- nitrate reduction (-)
