Legionella: Difference between revisions
From IDWiki
Legionella
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==Background== |
==Background== |
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===Microbiology=== |
===Microbiology=== |
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+ | |||
− | * Small, fastidious Gram-negative bacilli |
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+ | *Small, fastidious [[Stain::Gram-negative]] [[Cell shape::bacillus]] |
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− | * Uses proteins rather than carbohydrates as an energy source |
||
+ | *Uses proteins rather than carbohydrates as an energy source |
||
− | ** Requires media enriched with L-cysteine |
||
+ | **Requires media enriched with L-cysteine |
||
− | * ''L. pneumophila'' is an facultative intracellular parasite of a number of amoebae |
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+ | *''L. pneumophila'' is an facultative intracellular parasite of a number of amoebae |
||
− | * Close relative of ''Coxiella burnetti'' |
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+ | *Close relative of ''[[Coxiella burnetti]]'' |
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− | * Also have a quiescent state that is "viable but not cultivable" |
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+ | *Also have a quiescent state that is "viable but not cultivable" |
||
====Species==== |
====Species==== |
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+ | |||
− | * ''L. pneumophila'' serogroup 1: most common cause (70-80%) |
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+ | *''L. pneumophila'' serogroup 1: most common cause (70-80%) |
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− | * ''L. micdadei'': sometimes referred to as the "Pittsburgh pneumonia agent" or ''Tatlockia micdadei'' |
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+ | *''L. micdadei'': sometimes referred to as the "Pittsburgh pneumonia agent" or ''Tatlockia micdadei'' |
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− | * ''L. pneumophila'' serogroups 2-15 |
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− | * |
+ | *''L. pneumophila'' serogroups 2-15 |
− | * |
+ | *''L. dumoffi'' |
− | * |
+ | *''L. longbeachae'' |
+ | *''L. bozemanii'' |
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===Epidemiology=== |
===Epidemiology=== |
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+ | |||
− | * Ubiquitous in water: lakes, streams, oceans |
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+ | *Ubiquitous in water: lakes, streams, oceans |
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− | ** Warm water has higher burden of bacteria |
||
+ | **Warm water has higher burden of bacteria |
||
− | ** Free-living water amoebae support intracellular growth of ''Legionella'' |
||
+ | **Free-living water amoebae support intracellular growth of ''Legionella'' |
||
− | * No person-to-person transmission (one case report) |
||
+ | *No person-to-person transmission (one case report) |
||
− | * Most cases are sporadic, but there are also epidemics |
||
− | * |
+ | *Most cases are sporadic, but there are also epidemics |
+ | **Half of cases are associated with travel |
||
− | ** Other risk factors include cell-mediated immunocompromise (e.g. anti-TNF-alpha) |
||
+ | **Other risk factors include cell-mediated immunocompromise (e.g. anti-TNF-alpha) |
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− | ** Also spas, hot tubs, potting mix |
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+ | **Also spas, hot tubs, potting mix |
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− | * Most common strain is ''L. pneumophila'' Pontiac subtype serogroup 1 (90%) |
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+ | *Most common strain is ''L. pneumophila'' Pontiac subtype serogroup 1 (90%) |
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===Pathophysiology=== |
===Pathophysiology=== |
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+ | |||
− | * Inhalation or microaspiration |
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+ | *Inhalation or microaspiration |
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− | * Phagocytosed by alveolar macrophages |
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+ | *Phagocytosed by alveolar macrophages |
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− | ** Replicate intracellularly, then escape and are rephagocytosed by other macrophages |
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+ | **Replicate intracellularly, then escape and are rephagocytosed by other macrophages |
||
− | * The population of bacteria increases in the lungs |
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+ | *The population of bacteria increases in the lungs |
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− | ** Infiltration by neutrophils etc causes pulmonary edema |
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+ | **Infiltration by neutrophils etc causes pulmonary edema |
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==Clinical Manifestations== |
==Clinical Manifestations== |
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+ | |||
− | * Incubation period of 2 to 10 days (median 4 to 6 days); at most 28 days |
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+ | *Incubation period of 2 to 10 days (median 4 to 6 days); at most 28 days |
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===Legionnaires' disease=== |
===Legionnaires' disease=== |
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+ | |||
− | * Presents as a community-acquired or healthcare-associated pneumonia |
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+ | *Presents as a community-acquired or healthcare-associated pneumonia |
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− | * May have a prodrome of hours to days that involves headaches, myalgias, asthenia, and anorexia, possibly fevers |
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+ | *May have a prodrome of hours to days that involves headaches, myalgias, asthenia, and anorexia, possibly fevers |
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− | ** Diarrhea and abdominal pain |
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+ | **Diarrhea and abdominal pain |
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− | ** Cough, sometimes chest pain, sometimes productive |
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+ | **Cough, sometimes chest pain, sometimes productive |
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− | * Fevers with pulse-temperature dissociation, myalgias, nonproductive cough, diarrhea, confusion, hyponatremia, hypophosphatemia, and elevated liver enzymes |
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+ | *Fevers with pulse-temperature dissociation, myalgias, nonproductive cough, diarrhea, confusion, hyponatremia, hypophosphatemia, and elevated liver enzymes |
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− | * Can have leukopenia, thrombocytopenia, DIC, leukocytosis, pyuria |
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+ | *Can have leukopenia, thrombocytopenia, DIC, leukocytosis, pyuria |
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===Extrapulmonary infections=== |
===Extrapulmonary infections=== |
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+ | |||
− | * Rare, in immunocompromised patients or severe illness |
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+ | *Rare, in immunocompromised patients or severe illness |
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− | ** Except for pleural effusions, which are common |
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+ | **Except for pleural effusions, which are common |
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− | * Can develop abscesses in brain, spleen, extrathoracic lymph nodes, and skeletal and myocardial myscles |
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+ | *Can develop abscesses in brain, spleen, extrathoracic lymph nodes, and skeletal and myocardial myscles |
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− | * Case reports of endocarditis |
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+ | *Case reports of endocarditis |
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===Pontiac fever=== |
===Pontiac fever=== |
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+ | |||
− | * Incubation period 4 hours to 3 days |
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+ | *Incubation period 4 hours to 3 days |
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− | * Self-limited, short febrile illness |
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+ | *Self-limited, short febrile illness |
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− | ** Fevers, myalgias, headaches, and asthenia |
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+ | **Fevers, myalgias, headaches, and asthenia |
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− | ** Only diagnosed when there's an outbreak, since they're usually not sick enough to present to healthcare |
||
+ | **Only diagnosed when there's an outbreak, since they're usually not sick enough to present to healthcare |
||
− | ** Outbreaks associated with industrial processes using sprayed water, recreational spas, decorative water fountains, and cooling towers |
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+ | **Outbreaks associated with industrial processes using sprayed water, recreational spas, decorative water fountains, and cooling towers |
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− | * Can have cough, dyspnea, anorexia, arthralgia, and abdominal pain |
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+ | *Can have cough, dyspnea, anorexia, arthralgia, and abdominal pain |
||
==Diagnosis== |
==Diagnosis== |
||
+ | |||
− | * Legionella urine antigen if the most widely-used test |
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+ | *Legionella urine antigen if the most widely-used test |
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− | ** Most sensitive for ''L. pneumophila'' serogroup 1, less sensitive for others |
||
+ | **Most sensitive for ''L. pneumophila'' serogroup 1, less sensitive for others |
||
− | * Cultured best on buffered charcoal yeast extract (BCYE) agar is preferred |
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+ | *Cultured best on buffered charcoal yeast extract (BCYE) agar is preferred |
||
− | ** Colistin |
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+ | **Colistin |
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− | ** Needs cysteine |
||
+ | **Needs cysteine |
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− | * Stained best with Warthin-Starry or Dieterle, but stains poorly |
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+ | *Stained best with Warthin-Starry or Dieterle, but stains poorly |
||
{| class="wikitable" |
{| class="wikitable" |
||
− | ! |
+ | !Test |
− | ! |
+ | !Specimens |
− | ! |
+ | !Sensitivity |
− | ! |
+ | !Specificity |
− | ! |
+ | !Notes |
|- |
|- |
||
− | | |
+ | |Culture |
− | | |
+ | |Spurum, other lower respiratory tract secretions, lung, pleural fluid, blood, extrapulmonary tissues, fluids |
− | | |
+ | |20-95% |
− | | |
+ | |100% |
− | | |
+ | |Positive several days after treatment, needs special media |
|- |
|- |
||
− | | |
+ | |Antigen |
− | | |
+ | |Urine |
− | | |
+ | |60-95% |
− | | |
+ | |>99% |
− | | |
+ | |Highest sensitivity for serogroup 1, Pontiac type; positive for days to months |
|- |
|- |
||
− | | |
+ | |Immunofluorescent microscopy |
− | | |
+ | |Same as culture |
− | | |
+ | |20-50% |
− | | |
+ | |99% |
− | | |
+ | |Highest specificity with monoclonal antibody |
|- |
|- |
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− | | |
+ | |Antibody |
− | | |
+ | |Paired serum (acute and convalescent) |
− | | |
+ | |20-70% |
− | | |
+ | |95-99% |
− | | |
+ | |Highest specificity for serogroup 1 |
|- |
|- |
||
− | | |
+ | |Molecular amplification |
− | | |
+ | |Sputum (ideally BAL), other lower respiratory tract secretions, urine |
− | | |
+ | |70-95% |
− | | |
+ | |90-95% |
− | | |
+ | |Not well standardized, good performance in reference labs |
|} |
|} |
||
==Management== |
==Management== |
||
+ | |||
− | * First-line: Levofloxacin 750mg PO or IV once daily or Moxifloxacin 400mg PO or IV once daily |
||
+ | *First-line: [[Is treated by::Levofloxacin]] 750mg PO or IV once daily or [[Is treated by::moxifloxacin]] 400mg PO or IV once daily |
||
− | * Alternative: Azithromycin 500mg PO or IV once daily |
||
+ | *Alternative: [[Is treated by::azithromycin]] 500mg PO or IV once daily |
||
− | * Usual duration 7-10 days |
||
+ | *Usual duration 7-10 days |
||
− | * No need to treat Pontiac fever |
||
+ | *No need to treat Pontiac fever |
||
==Prevention== |
==Prevention== |
||
+ | |||
− | * [https://www.cdc.gov/legionella/health-depts/index.html https://www.cdc.gov/legionella/health-depts/index.html] |
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+ | *https://www.cdc.gov/legionella/health-depts/index.html |
||
{{DISPLAYTITLE:''Legionella'' species}} |
{{DISPLAYTITLE:''Legionella'' species}} |
Revision as of 06:55, 2 August 2020
Background
Microbiology
- Small, fastidious Gram-negative bacillus
- Uses proteins rather than carbohydrates as an energy source
- Requires media enriched with L-cysteine
- L. pneumophila is an facultative intracellular parasite of a number of amoebae
- Close relative of Coxiella burnetti
- Also have a quiescent state that is "viable but not cultivable"
Species
- L. pneumophila serogroup 1: most common cause (70-80%)
- L. micdadei: sometimes referred to as the "Pittsburgh pneumonia agent" or Tatlockia micdadei
- L. pneumophila serogroups 2-15
- L. dumoffi
- L. longbeachae
- L. bozemanii
Epidemiology
- Ubiquitous in water: lakes, streams, oceans
- Warm water has higher burden of bacteria
- Free-living water amoebae support intracellular growth of Legionella
- No person-to-person transmission (one case report)
- Most cases are sporadic, but there are also epidemics
- Half of cases are associated with travel
- Other risk factors include cell-mediated immunocompromise (e.g. anti-TNF-alpha)
- Also spas, hot tubs, potting mix
- Most common strain is L. pneumophila Pontiac subtype serogroup 1 (90%)
Pathophysiology
- Inhalation or microaspiration
- Phagocytosed by alveolar macrophages
- Replicate intracellularly, then escape and are rephagocytosed by other macrophages
- The population of bacteria increases in the lungs
- Infiltration by neutrophils etc causes pulmonary edema
Clinical Manifestations
- Incubation period of 2 to 10 days (median 4 to 6 days); at most 28 days
Legionnaires' disease
- Presents as a community-acquired or healthcare-associated pneumonia
- May have a prodrome of hours to days that involves headaches, myalgias, asthenia, and anorexia, possibly fevers
- Diarrhea and abdominal pain
- Cough, sometimes chest pain, sometimes productive
- Fevers with pulse-temperature dissociation, myalgias, nonproductive cough, diarrhea, confusion, hyponatremia, hypophosphatemia, and elevated liver enzymes
- Can have leukopenia, thrombocytopenia, DIC, leukocytosis, pyuria
Extrapulmonary infections
- Rare, in immunocompromised patients or severe illness
- Except for pleural effusions, which are common
- Can develop abscesses in brain, spleen, extrathoracic lymph nodes, and skeletal and myocardial myscles
- Case reports of endocarditis
Pontiac fever
- Incubation period 4 hours to 3 days
- Self-limited, short febrile illness
- Fevers, myalgias, headaches, and asthenia
- Only diagnosed when there's an outbreak, since they're usually not sick enough to present to healthcare
- Outbreaks associated with industrial processes using sprayed water, recreational spas, decorative water fountains, and cooling towers
- Can have cough, dyspnea, anorexia, arthralgia, and abdominal pain
Diagnosis
- Legionella urine antigen if the most widely-used test
- Most sensitive for L. pneumophila serogroup 1, less sensitive for others
- Cultured best on buffered charcoal yeast extract (BCYE) agar is preferred
- Colistin
- Needs cysteine
- Stained best with Warthin-Starry or Dieterle, but stains poorly
Test | Specimens | Sensitivity | Specificity | Notes |
---|---|---|---|---|
Culture | Spurum, other lower respiratory tract secretions, lung, pleural fluid, blood, extrapulmonary tissues, fluids | 20-95% | 100% | Positive several days after treatment, needs special media |
Antigen | Urine | 60-95% | >99% | Highest sensitivity for serogroup 1, Pontiac type; positive for days to months |
Immunofluorescent microscopy | Same as culture | 20-50% | 99% | Highest specificity with monoclonal antibody |
Antibody | Paired serum (acute and convalescent) | 20-70% | 95-99% | Highest specificity for serogroup 1 |
Molecular amplification | Sputum (ideally BAL), other lower respiratory tract secretions, urine | 70-95% | 90-95% | Not well standardized, good performance in reference labs |
Management
- First-line: Levofloxacin 750mg PO or IV once daily or moxifloxacin 400mg PO or IV once daily
- Alternative: azithromycin 500mg PO or IV once daily
- Usual duration 7-10 days
- No need to treat Pontiac fever