Send the link below via email or IMCopy
Present to your audienceStart remote presentation
- Invited audience members will follow you as you navigate and present
- People invited to a presentation do not need a Prezi account
- This link expires 10 minutes after you close the presentation
- A maximum of 30 users can follow your presentation
- Learn more about this feature in our knowledge base article
Transcript of Legionella Infections
Pathogenesis and Immunity
Legionella enters the lungs through
aspiration or direct inhalation.
adheres to respiratory tract epithelium
impair mucociliary clearance -
smoking, lung disease, or alcoholism
, predispose to Legionnaires' disease.
macrophages phagocytose legionellae
inhibits phagosome-lysosome fusion
Although many legionellae are killed, some proliferate intracellularly until the cells rupture;
The humoral immune system is active against Legionella.
IgM and IgG antibodies
are measurable within weeks of infection.
Antibodies promote killing of Legionella by phagocytes (neutrophils, monocytes, and alveolar macrophages).
Chronic lung disease;
transplantation, HIV, treatment with glucocorticoids or tumor necrosis factor blockers
- hospital-acquired infection -
Transplant recipients at highest risk
occurs in epidemics. The high attack rate (>90%) reflects airborne transmission.
into the lungs during respiratory tract manipulations.
- predominant mode of transmission,
it is unclear whether Legionella enters the lungs via
or directly via the drinking water.
have been linked to hospital-acquired Legionnaires' disease;
30% of postoperative Legionnaires' disease - among patients undergoing
head and neck surgery
at a hospital with a
contaminated water supply;
Aerosolization by devices filled with tap water, including
whirlpools, nebulizers, and humidifiers
, has been implicated.
A mist machine
in a grocery store was the source in a community outbreak
causes 80–90% of human infections
Buffered charcoal yeast extract
agar is needed for growth
lakes and streams.
wide range of conditions
- can live for years in refrigerated water
Once they enter
human-constructed water reservoirs
), they grow and proliferate.
Warm temperatures 25°–42°C enhance colonization
microcolonies within biofilms
eradication requires disinfectants that can penetrate the biofilm.
The organisms can invade and multiply within free-living protozoa
Rainfall and humidity
are environmental risk factors.
Modes of transmission:
The incidence of Legionnaires' disease depends on:
degree of contamination
of water reservoir,
of the exposed persons to water from that reservoir,
The availability of
specialized laboratory tests
on which the correct diagnosis can be based.
Legionella is among the top 4 bacterial causes of community-acquired pneumonia: (2–9% of cases)
18,000 cases occur annually in the United States and that
only 3% are correctly diagnosed
Legionella causes 10–50% of nosocomial pneumonia
when a hospital's water system is colonized with the organisms.
, flu-like illness
Incubation period of 24–48 h.
Malaise, fatigue, and myalgias
- the most common symptoms ( 97%)
(with chills) in 80–90% of cases
In <50% of cases - Other symptoms:
arthralgia, nausea, cough, abdominal pain, and
Complete recovery occurs within a few days;
antibiotic therapy is unnecessary.
A few patients may experience
for many weeks after recovery.
The diagnosis is established by
C. pneumoniae, Chlamydophila psittaci, Mycoplasma pneumoniae, Coxiella burnetii
, and some
and a low incidence of purulent sputum.
clinical manifestations of Legionnaires' disease are more severe than those of other "atypical" pneumonias
The incubation period is usually 2–10 days,
The symptoms range from a
mild cough and a slight fever to stupor with widespread pulmonary infiltrates and multisystem failure
slightly productive mild cough
sputum is streaked with blood.
—when coupled with hemoptysis, can lead to an incorrect diagnosis of pulmonary embolism.
Shortness of breath
abdominal pain, nausea, vomiting in 10–20% of patients,
Diarrhea (watery) - in 25–50%
or changes in mental status;
- in older patients with severe pneumonia.
Rales early in the course
Abdominal examination may reveal tenderness
from the lung.
Legionella has been identified in
lymph nodes, spleen, liver, or kidneys
in autopsied cases.
The most common site of extrapulmonary legionellosis is the
myocarditis, pericarditis, postcardiotomy syndrome
Organisms may gain entry through a
postoperative sternal wound
Sinusitis, peritonitis, pyelonephritis, skin and soft tissue infection, septic arthritis, and pancreatitis
with Legionnaires' disease have abnormal chest radiography
Radiologic findings are nonspecific
- in 28–63% of patients
In immunosuppressed patients, esp. those
rounded nodular opacities
may be seen - may expand and cavitate
Abscesses can occur in immunosuppressed hosts.
The progression of infiltrates and pleural effusion on chest radiography despite appropriate antibiotic therapy
within the first week is common
Complete clearing of infiltrates requires
Legionella urinary antigen test
—is recommended for
with community-acquired pneumonia
Hospitals in which the drinking water is known to be colonized should search for Legionella in all patients with
Thoracentesis should be performed if pleural effusion is found, and the fluid should be evaluated by
direct fluorescent antibody (DFA) staining and culture
2. TRACHEAL ASPIRATE
Direct fluorescent antibody staining of sputum
Urinary antigen testing
of material from normally sterile sites
sputum Gram's stain -
numerous leukocytes but
rapid and highly specific
More likely to be
positive in advanced disease
The definitive method
3–5 days is required
Antibiotics are added to suppress the growth of other bacteria
The use of
is necessary for maximal sensitivity.
- A 4X rise in titer is diagnostic;
- rapid, inexpensive,
easy to perform and highly specific.
test is available
only for serogroup 1
- cause 80% of Legionella infections.
Detectable 3 days after the onset
Disappears over 2 months
quinolones (levofloxacin, moxifloxacin, gemifloxacin
) - preferred
for transplant recipients
tetracycline, doxycycline and minocycline
Two-drug combination - For severely ill patients with extensive pulmonary infiltrates
A clinical response is seen in 3–5 days, after which oral therapy can be substituted.
The total duration of therapy in the immunocompetent host is
a longer course (3 weeks) may be needed for immunosuppressed patients
Pontiac fever requires only
not antimicrobial therapy
for Legionnaires' disease are
who do not receive appropriate antimicrobial therapy early in the course of illness.
With appropriate antibiotic treatment, mortality rates among
patients range from
0 to 11%;
without treatment - may be as high as 31%.
Routine culture of hospital water supplies
Disinfection of the drinking water
supply is effective.
Tap water filters
- effective for high-risk patient areas, such as transplantation or intensive care units.
Harrison's Principles of In Internal medicine - 18th edition
Hyperchlorination - no longer recommended because of its
expense, carcinogenicity, corrosive effects on piping, and unreliable efficacy.