Non Fermenter gram negative bacilli Flashcards
What are the two large groups of aerobic Gram-negative bacilli?
1) Fermentative (fermenters)
2) Nonfermentative (nonfermenters)
Nonfermenters can be further classified as oxidizers or non-oxidizers.
What is a common biochemical feature of nonfermenting Gram-negative bacilli regarding TSI or KIA?
No reaction, showing red (no change) in butt or slant (NC/NC) or may produce an alkaline slant (K/NC)
This indicates their inability to ferment carbohydrates.
What is the significance of the Hugh-Leifson Oxidation-Fermentation (OF) media?
It detects small amounts of acid or weak acids produced by nonfermenters or fastidious fermenters
The peptone concentration in Hugh-Leifson OF media is reduced to 0.2% from 2.0%.
What are initial clues to identify a nonfermenter?
1) Long, thin Gram-negative bacilli/coccobacilli
2) Oxidase positive (with exceptions)
3) Non-reactive with commercial kits for Enterobacteriaceae
4) TSI nonreactive
These clues help differentiate nonfermenters from other bacteria.
What is Pseudomonas aeruginosa classified as?
A non-fermentative Gram-negative rod
It does not ferment glucose and is commonly found in hospitals.
What infections can Pseudomonas aeruginosa cause?
1) UTIs in catheterized patients
2) Septicaemia in intravenous drug users and transplant patients
3) Respiratory infections in cystic fibrosis patients
4) Wound infections, including burns
5) Otitis externa
Pseudomonas aeruginosa is known for its antibiotic resistance.
What are the identifying characteristics of Pseudomonas aeruginosa?
1) BA colonies can be mucoid or nonmucoid
2) Metallic sheen
3) Produces pyocyanin
4) NLF on MAC
5) Grape-like odour
Pyocyanin is used to differentially identify Pseudomonas aeruginosa.
What is the resistance profile of Pseudomonas aeruginosa?
Usually resistant to:
* Penicillin
* Ampicillin
* Many cephalosporins
* Chloramphenicol
It is typically susceptible to aminoglycosides and certain semisynthetic penicillins.
What is Acinetobacter baumannii commonly associated with?
Pneumonia, urinary tract infections, and catheter infections in immunocompromised patients
Acinetobacter species are prevalent in the human skin and pharynx.
What are the identifying characteristics of Acinetobacter species?
1) Coccobacilli
2) Oxidase negative
3) BA: Smooth, opaque, raised colonies
4) NLF on MAC
Some species may be beta-hemolytic.
What is Stenotrophomonas maltophilia known for?
Lower respiratory tract infections in cystic fibrosis patients and septicaemia in cancer patients
It is resistant to most antibiotics.
What infections can Burkholderia cepacia cause?
1) Pneumonia in cystic fibrosis patients
2) Endocarditis
3) UTIs
4) Osteomyelitis
5) Dermatitis
It is a relatively infrequent nosocomial pathogen.
What are the identifying characteristics of Moraxella species?
1) Gram-negative bacillus or coccobacillus
2) Strongly oxidase positive
3) Nonmotile
4) Biochemically inert
They are susceptible to penicillin, which is unusual for nonfermenters.
What is the most commonly isolated species of Alcaligenes?
Alcaligenes faecalis
It can cause bacteremia, sepsis, and other opportunistic infections.
Chryseobacterium meningosepticum is most commonly associated with which condition?
Septicemia and meningitis in newborns
It can also cause pneumonia and endocarditis in adults.
What is a notable characteristic of Chryseobacterium species?
Long, thin bacilli often with bulbous ends
They are Gram-negative and oxidase positive.
