LEGIONELLA spp!!! MICROM442 Deck 18 Flashcards
Non-pneumophila species include
– L. micdadei
– L. bozemanii
– L. longbeachae
– L. macheachernii
Environmental life cycle
– Facultative parasite of free-living amoebae!
– Multi-organism biofilm growth; water supplies
> Up to 80% of air conditioning cooling towers (102 – 108 cfu/mL)
> 5-30% of home/industrial water heaters, plumbing
Human infection
– Transmitted by aerosolized H2O, Inhalation, micro-aspiration
(?)
– Invades phagocytes, lives inside
Gm???
negative, and tough to stain, looks different in vitro vs in vivo
Colonies
– Grey-white, round/convex
– “Cut glass”
energy source? (fastidious bacteria)
amino acids, NOT carbohydrates in vitro
> L-cysteine (ALL spp require this)
– Optimal growth: a-ketoglutarate, iron supplementation
type of aerobe?
obligate
media?
Buffered Charcoal Yeast Extract (BCYEa)
Environmental conditions
35-37C, pH 6.7 – 6.9 (whoa!) & salt sensitive (remember the amino acids)
Urine antigen testing
– L. pneumophila serogroup 1 ONLY
> Not other serogroups and NOT Non-pneumophila (5-40%)
> Detects 60-70% Pontiac-type epidemic strains, 90% sporadic
cases
– Sickest patients most likely to be urine Ag positive
PCR
16S rDNA, usually
L. pneumophila has 16 serogroups which include the group serogroup 1 (65-90%), and within serogroup 1 there is?
serogroup 1 pontiac subtype
legionnaires disease
Bacterial pneumonia, acquired from aerosolized water
legionnaires dz characteristics
> CFR = generally <10%, cure >90%
– higher if wrong Abx, patient pop (male, older, steroids…)
Tx eryth/tetracycline = 10%, other drugs higher CFR
Low attack rate
RARE in kids (<1% CAP)
legionella pneumophila pathology
> Pontiac Fever
– URI, not a pneumonia
– High attack rate, non-fatal (self-limited)
– Compare: LD is high fatality, low attack
– Sx within 4-60hrs of exposure
Cough, fever, loss of appetite, aches and belly pain, fever, incr
HR
– Recovery within 3-5days, often no medical care
– Children do get dz
