Legionella by uMYwGu

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									Legionnaires’ disease
Part 1 – Introduction to Legionella and epidemiology
Legionella– the organism causing legionellosis
    has more than 50 species, 16 of which are associated with human infection
    Legionella pneumophila accounts for 80-90% of all infections
Onset and symptoms
Incubation period is 2-10 days           10-40% mortality                 low attack rate
Symptoms include fever, headache, dry cough, flu-like illness, confusion, diarrhoea
Who’s at risk?
Smokers                Heavy drinkers             Immunosuppressed
Hospital transplant patients         Men more than women                      People aged 50 or over
Modes of infection
Via inhalation of aerosol particles small enough to penetrate lung alveoli but large enough to
contain at least one bacterial cell. Aspiration can occur – especially for patients who acquired the
infection in hospital. Case to case transmission does not occur
Chain of causation
Environmental reservoir  Multiplication  Dissemination  Inhalation  Susceptible host
Diagnosis
*Culture (sputum sample/ lung tissue)       *Serology – blood test at 3-6 – 12 weeks of the illness
*Urinary antigen detection in acute phase of illness                       *PCR – sputum sample
Reporting process in England & Wales
Hospital Microbiologist                               HPA via local HPU (SWLHPU 020 8682 6132)

                      Centre for Infections Respiratory Diseases Department
            (need to know if case is hospital acquired, community or travel associated)
                    www.hpa.org.uk/infections/topics_az/legionella/advice.htm
Effect of under diagnosis
Most pneumonia cases do not have a causative organism identified
Clinicians often treat with antibiotics without testing to identify type of pneumonia
Summary of cases 1980 – 2006
47.7 % community acquired              47% travel associated                  5.3% hospital acquired
Case definitions for hospital acquired Legionella infection
   1. Definitely hospital acquired
      Patients who spent all of the 10 days prior to onset in hospital
   2. Probably hospital acquired
      Patients who spent 1-9 days prior to onset either in a hospital associated with previous
      cases, or that yielded an isolate indistinguishable from isolates obtained from the hospital
      water system at about the same time
   3. Possibly hospital acquired
      Patients who spent 1-9 days in hospital before onset – in a hospital not known to be
      associated with any other cases of Legionella infection
Legionellosis is sometimes confused with Pontiac fever, a mild illness without pneumonia,
which has the following onset & symptoms
Incubation period 12-48 hours     Flu-like illness   0% mortality         high attack rate
Legionella is an atypical pneumonia (does not respond to penicillin). Other atypical
pneumonias include
Coxiella (Q fever)          Mycoplasma pneumoniae           Chlamydia (respiratory)
Source
Dr. Carol Joseph (16.08.07) Study Day Presentation.

Shona Ross                     Infection Control Lead                         20.08.07

								
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