Legionella
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Introduction
Aerobic gram negative bacilli. Motile. Ubiquitous in aquatic environments. There are 22 Legionella species & 33 serotypes identifiable by a slide agglutination test.
Epidemiology
- natural habitat is water
- epidemics have occurred
- contaminaed air-conditioning cooling towers
- construction or excavation in contaminated soil
- contaminated hospital showers
- most cases occur in summer & early autumn
- 7% of community-acquired pneumonia
- 25% of atypical pneumonias
- 10% of nosocomial infections
Pathology
- aerosolized & inhaled bacteria
- human to human transmission does not occur
- 50% of adults have serologic evidence of prior infection
- risk factors
- debilitated & immunocompromised patients
- COPD
- tobaccoism (smoking)
- cancer
- diabetes mellitus
- chronic heart disease
- chronic renal failure
Clinical manifestations
(see Legionella pneumophila)
Laboratory
- Legionella antigen in tissue/body fluid
- direct fluorescent antibody (DFA): 50% sensitivity
- Legionella antigen in urine
- sensitivity for Legionella pneumophila 60-80%; specificity > 99%
- Legionella serology
- indirect fluorescent antibody (IFA): 50% sensitivity, identifies only serogroup 1
- 4-fold rise in titer over 3 weeks to at least 1:128
- single titer of 1:256
- false positive titers may be seen with
- Legionella identified in isolate
- Legionella identified by culture:
- Legionella DNA 70% sensitive, 99% specific[4]
- Legionella rRNA
Management
- antimicrobial therapy
- erythromycin
- Rifampin 600 mg PO QD may be synergistic
- alternative antibiotics
- Legionella endocarditis
- valve replacement
- 3-12 months of antibiotic therapy
More general terms
More specific terms
- Legionella anisa
- Legionella birminghamensis
- Legionella bozemanii
- Legionella cherrii
- Legionella cincinnatiensis
- Legionella dumoffii
- Legionella feeleii
- Legionella gormanii
- Legionella hackeliae
- Legionella jordanis
- Legionella lansingensis
- Legionella longbeachae
- Legionella maceachernii
- Legionella micdadei
- Legionella oakridgensis
- Legionella pneumophila
- Legionella sainthelensi
- Legionella tucsonensis
- Legionella wadsworthii
Additional terms
References
- ↑ Harrison's Principles of Internal Medicine, 13th ed. Companion Handbook, Isselbacher et al (eds), McGraw-Hill Inc. NY, 1995, pg 228-29
- ↑ Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 797
- ↑ Medical Knowledge Self Assessment Program (MKSAP) 11, 19American College of Physicians, Philadelphia 1998, 2021
- ↑ 4.0 4.1 Harrison's Principles of Internal Medicine, 13th ed. Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 657