Culture conditions
37C aerobic blood agar
Colonial morphology
Metallic sheen,
large smooth
sweet odour
Gram stain
Gram negative bacilli
small rods
Biochemical tests
KOH positive
Catalase - weak positive
Oxidase - positive
Presumptive pseudomonas spp tests
- Growth at different temperatures
- Growth on P. aeruginosa selective agar
Growth at different temperature test procedure
- Split blood agar into 3
- Zig zag inoculate the test and controls
Controls = P.aeruginosa, P.fluorescens - Incubate one plate (P.A is +ve control, P.f is -ve control)
at 42C for 48hrs. - Incubate the other plate (swap controls) at 4C for 72hrs.
Growth at different temperature test results
42C agar plate after 48 hrs = P aeruginosa grows
4C plate after 72hrs = P.fluorescens grows.
Growth on P.aeruginosa selective agar test procedure
- Split agar into 2
- Streak inoculate test organisms + controls (P.aeruginosa, P.fluorescens, E.coli)
- Incubate at 37C for 48hrs.
Growth on P.aeruginosa selective agar test results
P. aeruginosa grows fluorescent green colonies.
Additional confirmatory tests for Pseudomonas spp
NOT Maldi-tof or Vitek
Use API-20-NE
Pseudomonas spp infections
Opportunistic pathogen
Very common HAI
Targets immunocompromised = neonates, elderly, CF, AIDS, immune-deficient, chemotherapy…
Targets those with breach in physical barriers e.g. burn victims, IV lines, catheters.
Pseudomonas spp disease
Respiratory = pneumonia, cystic fibrosis
Ear = otitis media
Eye = bacterial keratitis
GI = enterocolitis, enteritis, diarrhoea
Bones + joints = osteomyelitis
UTI
BSI - endocarditis, CNS, tissue infections.
Clinically significant
AST - automated is not reliable
Instead use
E-tests or manual disk diffusion tests.
Specimens
Sputum, urine, blood, pus
