Legionella
Bacteriology
HISTORY ● 8,000 and 18,000 people/year are
• Who – 4000 members of the Pennsylvania hospitalized with Legionnaires’ disease in
State American legion the U.S
• Where – Philadelphia Convention ● Underdiagnosed
• When – July 21 to 24, 1976 ● Unreported
• What – Many people suffered from ● Summer and early fall, but it can happen
pneumonia any time of year
• July 27 – first patient died ● Ubiquitous in freshwater for centuries
• July 30 – a physician in Bloomberg realized ● Unique growth requirements in the
that the 3 patients he was treating from environment
similar condition had all attended the ● Human technology favoring complex water
convention systems
o On the same day, a nurse in ● Legionellosis - emerging infectious
Chambersburg Hospital noted a disease in the late 20th century
similar condition in 3 patients who LEGIONNAIRE’S DISEASE
had gone to the convention • Legionella pneumophila
• August 18 – legionnaires had already • 4th among the causes of pneumonia
died, huge media coverage o S. pneumonia
• Out of the 221 cases, 72 were not involved o H. influenza
in the American legion convention o Chlamydophila pneumoniae
o People who had either been inside • Atypical
the Bellevue Stratford Hotel or • Gram-stained sputum – no organisms
o Had walked past it • Prevalent
• January 18, 1977 – CDC announced that LEGIONELLA
the cause of Legionnaires disease • Kingdom: Bacteria
o Dr. Joseph McDade – person who • Division: Proteobacteria
isolated legionella • Class: Gamma Proteobacteria
• Order: Legionellales
• Family: Legionellaceae
• Genus: Legionella
• 50 species
o ½ of species implicated in human
disease
2 SPECIES OF CLINICAL IMPORTANCE
• Legionella pneumophila
o Causes ~ 90% of all cases of
legionellosis
o Majority of all confirmed cases are
Dr. Joseph McDade caused by serogroups 1-6
• Source of the breeding site – traced to the • Legionella micdadei
cooling towers that were connected to o Most common after L. pneumophila
the air conditioners of the hotel
EPIDEMIOLOGY
● Although this type of bacterium was around
before 1976, more illness from
legionnaires disease is being detected
BS BIOLOGY (MICROBIOLOGY TRACK) | 1
Bacteriology
HISTORY ● 8,000 and 18,000 people/year are
• Who – 4000 members of the Pennsylvania hospitalized with Legionnaires’ disease in
State American legion the U.S
• Where – Philadelphia Convention ● Underdiagnosed
• When – July 21 to 24, 1976 ● Unreported
• What – Many people suffered from ● Summer and early fall, but it can happen
pneumonia any time of year
• July 27 – first patient died ● Ubiquitous in freshwater for centuries
• July 30 – a physician in Bloomberg realized ● Unique growth requirements in the
that the 3 patients he was treating from environment
similar condition had all attended the ● Human technology favoring complex water
convention systems
o On the same day, a nurse in ● Legionellosis - emerging infectious
Chambersburg Hospital noted a disease in the late 20th century
similar condition in 3 patients who LEGIONNAIRE’S DISEASE
had gone to the convention • Legionella pneumophila
• August 18 – legionnaires had already • 4th among the causes of pneumonia
died, huge media coverage o S. pneumonia
• Out of the 221 cases, 72 were not involved o H. influenza
in the American legion convention o Chlamydophila pneumoniae
o People who had either been inside • Atypical
the Bellevue Stratford Hotel or • Gram-stained sputum – no organisms
o Had walked past it • Prevalent
• January 18, 1977 – CDC announced that LEGIONELLA
the cause of Legionnaires disease • Kingdom: Bacteria
o Dr. Joseph McDade – person who • Division: Proteobacteria
isolated legionella • Class: Gamma Proteobacteria
• Order: Legionellales
• Family: Legionellaceae
• Genus: Legionella
• 50 species
o ½ of species implicated in human
disease
2 SPECIES OF CLINICAL IMPORTANCE
• Legionella pneumophila
o Causes ~ 90% of all cases of
legionellosis
o Majority of all confirmed cases are
Dr. Joseph McDade caused by serogroups 1-6
• Source of the breeding site – traced to the • Legionella micdadei
cooling towers that were connected to o Most common after L. pneumophila
the air conditioners of the hotel
EPIDEMIOLOGY
● Although this type of bacterium was around
before 1976, more illness from
legionnaires disease is being detected
BS BIOLOGY (MICROBIOLOGY TRACK) | 1
