Legionella: Difference between revisions
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Legionella
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− | == |
+ | ==Background== |
+ | ===Microbiology=== |
||
− | * |
+ | *Small, fastidious [[Stain::Gram-negative]] [[Shape::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 burnetii]] |
− | * |
+ | *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 [[Usual incubation period::2 to 10 days]] (median 4 to 6 days); at most [[Incubation period range::up to 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 |
+ | {| 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, even up to a year |
|- |
|- |
||
− | | |
+ | |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== |
− | * |
+ | *Treatments include: [[Is treated by::Levofloxacin]] 750 mg PO or IV once daily, [[Is treated by::moxifloxacin]] 400 mg PO or IV once daily, or [[Is treated by::azithromycin]] 500 mg PO or IV once daily |
− | * |
+ | *Alternative is [[Is treated by::doxycycline]] 100 mg p.o. twice daily |
− | * |
+ | *Usual duration 7-10 days |
− | * |
+ | *No need to treat Pontiac fever |
− | == |
+ | ==Prevention== |
− | * |
+ | *https://www.cdc.gov/legionella/health-depts/index.html |
− | {{DISPLAYTITLE:''Legionella'' |
+ | {{DISPLAYTITLE:''Legionella''}} |
[[Category:Gram-negative bacilli]] |
[[Category:Gram-negative bacilli]] |
Latest revision as of 11:19, 12 December 2023
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 burnetii
- 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 up to 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, even up to a year |
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
- Treatments include: Levofloxacin 750 mg PO or IV once daily, moxifloxacin 400 mg PO or IV once daily, or azithromycin 500 mg PO or IV once daily
- Alternative is doxycycline 100 mg p.o. twice daily
- Usual duration 7-10 days
- No need to treat Pontiac fever