This is an extract of our Legionella Tb document, which we sell as part of our Respiratory Notes collection written by the top tier of University Of Leicester students.
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Legionella Three epidemiological patterns of disease 1) Outbreaks among previously fit individuals staying in hotels, institutions or hospitals whose showers and cooling systems have been contaminated with the organism 2) Sporadic cases where the source of infection is unknown. Most cases involve middle-aged and elderly men who are smokers (but also seen in children) 3) Outbreaks occurring in immune-compromised patients The organism
- Gram negative pleomorphic bacteria
- More than 39 species but L.Pneumophila is most frequently implicated in human disease
- Reside in swimming pools, Jacuzzis, air conditioning systems, fountains and domestic and natural water supplies.
- The organism replicates between 20 and 40 degrees
- Infection is spread by aerosol route
- Incubation period is 2-10 days Pathogenesis
- Outer membrane protein inhibits acidification of phagolysosome
- L. Pneumopila exhibits a potent exoprotease Signs and symptoms Legionellosis can exhibit a mild flu- Malaise like illness whereas L. Pneumophila
- Pyrexia (Legionairres disease) can be
- Fever with rigors severe with respiratory failure and
- GI symptoms (half of patients) - D+V, high mortality abdo pain
- Haematuria leading to AKI
- Dry cough that later may become productive and purulent L.Pneumophilia (Pneumonia)
- A presumptive diagnosis is possible in majority of patients if they have three of following features o Prodromal viral-like illness o Dry cough, confusion or diarrhea o Lymphopenia without marked leukocytosis o Hyponatraemia (inappropriate naturetic hormone production) Investigations Microbiology
- Sputum or broncheoalveolar lavage fluid cultured (can take up to 3 weeks)
- Rapid diagnosis by immunofluorescence or antigen detection in urine
- Serum antibodies rise after 10-14 days Biochemistry
- Low serum sodium, raised CRP Imaging Chest xray usually shows multi-lobar consolidation sometimes with pleural effusion
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