Legionella Flashcards
Describe the morphology and staining of legionella
Gram Negative Rods
Do NOT stain with gram stain clinically
Seen with Silver stain
Which species of legionella causes most legionella based infections?
L.Pneumophila
What are the charcteristics of legionella?
Obligate Aerobe Non-fermenter FAstidious growth requirements Motile Catalase Positive Weak Oxidase Positive B-Lactamase positive -> PENICLLINS DONT WORK
Where is legionella found?
Acquatic lakes
Water systems: cooling towers, showers, fountains, whilpools
Which patients are predisposed to legionella infections?
Transplant recipient
Cigarette smoking
Chronic Lung disease
Describe the pathogenesis of Legionella
Inhale/Ingest pathogens -> OMP porins bind C3b complement receptors on mononuclear phagocytes -> endocytosis -> inhibit phagolysosome fusion -> multiply intracellularly -> kill cell with lysis of vacuol
What kind of immunity do you need to clear a legionella infection?
Cell Mediated
What are the clinical presentations of LEgionella?
Pontiac Fever
Legionellosis (severe penumonia)
Asymptomatic Infection
What is pontiac fever?
Febrile- flu like illness without respiratory component
Short incubation
Self limiting
What is legionellosis
Severe pneumonia
Multilobal pneumonia (Strep pneumo is single lobar pneumonia)
Multisystem disease-> high mortality if untreated
How is legionella diagnosed?
Microscopy: gram stain not helpful, use silver stain or DFA
Culture: BYCE: Buffered Charcoal Yeast Extract Agar Media
Urinary Antigen Test: ELISA-> only for L.Pneumophila serogroup 1
PCR
How is legionella treated?
Intracellular Activity Abx
Macrolides
Fluoroqinolones: Cipro, Moxi
