Non-fermentative GNB Flashcards
List the main identifying features of Pseudomonas aeruginosa?
- GNB
- Obligate aerobe
- Motile
- catalase +ve
- Oxidase: +ve
- O-F: Oxidative
- Colony morphology: Flat, matte, uneven/rough border, Yellow & Green pigment, metallic sheen, grape-like odor
What is an obligate anaerobe? Give an example (genus and species)
Grows in the abscence of O2
e.g. Clostridium sp
What is an obligate aerobe? Give an example (genus and species)
Requires O2 to grow
e.g. P.aeruginosa, Stenotrophomanoas maltophilia
What does fermentation refer to? (definition)
Break down glucose anaerobically to make energy
Which metabolic process is used by a non-fermenter?
Oxidative metabolic pathways that require O2
What types of organisms are the API20NE and RapID NF designed to identify?
Detect non-fermenting GNB
What common superficial infections does Ps. aeruginosa cause? (7)
- Burns
- Otitis externa - swimmers ear
- Lower RTI (esp. Hx cystic fibrosis)
- Eye infections
- bacteremia
- noscomial infections: UTI
- Skin lesions/wounds
Which two genera of bacteria are frequently isolated from sputum specimens from patients with cystic fibrosis?
(mucoid) Pseudomonas aeruginosa & Burkholderia cepacia
Describe how you would differentiate between the four genera described in this lecture using rapid tests (to genus level only).
- Pseudomonas sp
- Burkholderia so.
- Stenotrophomonas maltophilia
- Acinetobactrr sp
- Pseudomonas sp.: GNB, *oxidase pos, motile, flat, metallic sheen colonies w/ green/yellow pigment
- Burkholderia sp.: GNB, *oxidase v (slow), motile, pigmented?
- Stenotrophomonas sp.: GNB, *oxidase neg, motile
- Actinobacter sp.: *GNC/B, *Oxidase neg, *non-motile
Why is an EDTA disc sometimes tested with antimicrobial susceptibilities? Explain.
bc EDTA chelate Zn = no growth = detect metallo-carbapenamase
What primary test characteristic do S.maltophilia and Acinetobacter sp. have in common? What primary feature is different?
Common: Oxidase neg
Different: motililty. Pos = S.maltophilia. Neg= Actinobacter sp.
Even before the advent of multi-drug resistant strains of these organisms, explain why the non-fermenting organisms in this lecture are well placed to cause significant nosocomial infections?
bc they are R to carbapenem (P.aeruginosa & Acinetobacter sp)
Why do the non-fermenters in this lecture have a strong association with respiratory infections?
found in respiratory equipment in hospital that contain water as humindifier
Why is a mucoid strain of Pseudomonas likely to be more virulent than a non-mucoid isolate?
Because the mucoid capsule allows them to adhere better and protects them from being phagocytosed = not removed by coughing or by phagocytosis
If a carbapenemase producing strain of Acinetobacter were isolated and it was negative for the MCR-1 gene, what 3 likely treatment options would be available? (subject to susceptibility testing – see ESBL lecture)
Collistin, tygelicine, aztroneam
