Part II Legionella biology Explaining building colonization and - - PowerPoint PPT Presentation

Part II

• Legionella biology
• Explaining building colonization and disease

Legionella are a Family of Environmental Bacteria that Live in Water

 Family of different species

• > 50 different species in genus Legionella
• Only half have been associated with disease
• L. pneumophila – 90% of disease

Legionella are a Family of Environmental Bacteria that Live in Water

 Family of different species

• > 50 different species in genus Legionella
• Only half have been associated with disease
• L. pneumophila – 90% of disease

Legionella

• L. pneumophila
• L. longbeachae
• L. bozemanii
• L. micdadei
• L. dumoffii
• L. feeleii
• L. wadsworthii
• L. anisa
• thers

Other species – only in environment 90% 10%

14 serogroups Serogroup 1 (sg1)

Serogroups 2-14

85% 5%

Sub-typing, molecular fingerprinting – outbreak investigations

Legionella are Environmental Bacteria that Live in Water

 Surface water (lakes, streams, etc)

• Virtually all have Legionella
• Low numbers - rare disease

Actually, Legionella live in a vacuole inside of amoebae and other protozoa that live in the water

In the human lung Legionella grow in amoebae-like phagocytic cells called macrophages

Legionella - Habitat

 Intracellular growth- amoebae and other protozoa

• protects Legionella from drying during aerosolization
• One inhaled amoeba could provide an infectious dose

Some protozoa spit out these vacuoles full of Legionella

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Legionella Live in Warm Water

 Surface water (lakes, streams, etc)

• Virtually all have Legionella
• Low numbers - rare disease

 Thermal areas (i.e. near hot springs)

• Elevated numbers – rare disease

• Building water – requirements to be met for Legionnaires disease
• warm (not too cold, not too hot)
• high levels of Legionella
• mechanism for airborne (aerosol) dissemination
• susceptible host (hospitalized, older, smokers, etc.)

Legionella Live in Building Water

Legionella Live in Water Biofilms

Legionella Live in Water Biofilms

Mature biofilm

Includes amoebae feeding on these bacteria

Includes escaping amoebae and vacuoles (pellets) full of Legionella Legionella

In nature there may be hundreds of different bacteria

Sharon G. Berk, Gary Faulkner, Elizabeth Garduño, Mark

• C. Joy, Marco A. Ortiz-Jimenez,3 and Rafael A. Garduño.

Appl Environ Microbiol. 74: 2187 (2008)

aerosols

City water (in low numbers)

Hospital-acquired LD (HA-LD)

• or-

Healthcare-associated LD

Hospital

aerosols Many different Legionella species and serogroups City water (in low numbers) drinking/aspiration from URT

Community-acquired LD (CA-LD)

Other buildings aerosols

Amost entirely L. pneumophila serogroup 1

Cooling towers

Legionella amplification in building water

Potable water (hot water)

Whirlpool spas Decorative fountains / Water walls

After entering from the city water in low numbers

Cooling towers

Legionella amplification in building water

Potable water (hot water)

Whirlpool spas Decorative fountains / Water walls

Vegetable misters

Legionella amplification in building water Unusual sources

Ultrasonic humidifiers Car/bus wash

New York – 2 cases (2007) Australia – 5 cases (2008) Louisiana – 32 cases/2 deaths (1990) Sweden – 8 cases/2 deaths (2008) Wales (hotel) – 5 cases, 2 deaths (2000) Cyprus (hospital) – 11 infant cases, 2 deaths (1999)

Most cases are single isolated events

Sources unknown or unconfirmed Susceptible person - wrong place at the wrong time aerosols

Disease Pathogenesis

• Legionnaires’ Disease – acute pneumonia
• Inhalation of infectious particles into the lung
• Incubation period of 2-14 days before symptoms

Disease

• Legionnaires’ Disease – acute pneumonia
• Inhalation of infectious particles into the lung
• Engulfment by alveolar macrophages, monocytes
• Rapid intracellular replication (thinks its an amoeba!)
• Acute inflammation- fluid accumulation, white cells
• Respiratory failure

Resident alveolar macrophages

phagocytic cells – amoeba-like

Replication in macrophages over 24hr

Legionnaires’ Disease - Diagnosis

 Clinical presentation – not specific  Chest X-ray – not specific

Legionnaires’ Disease Diagnosis

 Clinical presentation – not specific  Chest X-ray – not specific  Sputum- traditional laboratory tests - negative  Lack of response to antibiotics such as penicillin

↓ Atypical Pneumonia

• Legionella laboratory tests – specific

diagnosis !!

↓

May be 2-3 days post-admission

Legionnaires Disease - Diagnosis

 Sputum, bronchial aspirate, lung biopsy (autopsy)

• Culture (special media) – several days
• Low sensitivity, have an organism to characterize

Suspect colonies transferred to CYE agar with and without L-cysteine

Legionella

e.g. L.pneumophila sg1

CYE agar (selective and non-selective) With and without acid-treatment Species/serogroup antisera Sub-typing, molecular typing 5-7 days

Legionnaires Disease - Diagnosis

 Sputum, bronchial aspirate, lung biopsy (autopsy)

• Culture (special media) – several days
• Low sensitivity, have an organism to characterize

Clinical isolate

CYE agar (selective and non-selective) With and without acid-treatment Compare via sub-typing and molecular typing

Environmental isolates

?

Patient A Patient B

Legionnaires Disease - Diagnosis

 Urine antigen test - same day

• High sensitivity/specificity

Pieces of Legionella (antigens) in the blood get filtered out into the urine Results within an hour

Legionnaires Disease - Diagnosis

 Urine antigen test - same day

• High sensitivity/specificity

Only detects L. pneumophila sg 1 Results within an hour Will not detect all hospital-acquired Legionnaires’ disease

Treatment

 Resistant to penicillins and cephalosporins!  Classical treatment: erythromycin or newer

macrolides such as azithromycin, clarithromycin

 New- better survival with fluoroquinolones. In

severe cases use both a macrolide and quinolone

Patients still die (5-30%) due to delay in diagnosis along with the rapid progression of the disease, particularly in immunocompromised patients.