DR.T.V.RAO MD 1

Dr.T.V.Rao MD

LEGIONNAIRES’ DISEASE

DR.T.V.RAO MD 2

• Legionellosis is caused by gram-negative bacteria of the genus Legionella.

• Legionellosis is a potentially fatal infectious disease caused by gram negative, aerobic bacteria belonging to the genus Legionella.] Over 90% of Legionellosis cases are caused by Legionella pneumophila, a ubiquitous aquatic organism that thrives in temperatures between 25 and 45 °C (77 and 113 °F), with an optimum temperature of 35 °C

LEGIONELLOSIS A BACTERIAL INFECTION

DR.T.V.RAO MD 3

SCIENTIFIC BEGINNING OF LEGIONNAIRES DISEASE

• Legionnaires' disease acquired its name in July 1976 when an outbreak of pneumonia occurred among people attending a convention of the American Legion at the Bellevue-Stratford Hotel in Philadelphia. On January 18, 1977 the causative agent was identified as a previously unknown strain of bacteria, subsequently named Legionella.

DR.T.V.RAO MD 4

• A thin and flagellated gram-negative bacterium.

• Non-capsulated rod-like bacteria.

• Dot/Icm secretion system to inject large numbers of protein effectors into the host cells.

• Pseudopod acts as a phagocytosis.

• Incubation period: two to ten days.

BACTERIOLOGY – LEGIONARIES DISEASE

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EPIDEMIOLOGY OF LEGIONELLOSIS• Legionellae are ubiquitous worldwide. Most cases of

Legionellosis are caused by Legionella pneumophila. Disease occurs after exposure to aquatic settings that promote bacterial growth—the aquatic environment is somewhat stagnant, the water is warm (77°F–108°F [25°C–42°C]), and the water must be aerosolized so that the bacteria can be inhaled into the lungs. These 3 conditions are met almost exclusively in developed or industrialized settings. Disease does not occur in association with natural settings such as waterfalls, lakes, or streams.

DR.T.V.RAO MD 6

BREEDING OF LEGIONARIES DISEASE

• The bacteria grow best in warm water, like the kind found in hot tubs, cooling towers, hot water tanks, large plumbing systems, or parts of the air-conditioning systems of large buildings. Indoor ornamental fountains have been confirmed as a cause of Legionnaires' disease outbreaks, in which submerged lighting as a heat source was attributed to the outbreak in all documented cases

DR.T.V.RAO MD 7

HOW THE LEGIONELLA THRIVE

• Legionella thrive in man-made aquatic environments where the water temperature is higher than ambient temperature: whirlpool spas, cooling towers (air-conditioning units from large buildings), water used for drinking and bathing, water fountains, humidifiers, ice machines, and vegetable misters, etc. In fact, most cases of Legionellosis can be traced to using such systems. It is a major concern for health professionals and construction and water systems maintenance workers.

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• Opportunistic Disease: underlying illness/weak immune system.

• Nosocomial infections are major concerns.

• Middle-aged, elderly, COPD, smokers and other genetic susceptible patients are primary targets.

WHO ARE AT RISK

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TRANSMISSION OF LEGIONELLA• L. pneumophila is NOT

spread by human-human interaction.

• Mist or vapour contaminated with the bacteria.

• Warm stagnant water (90-122 F) in complex systems is ideal.

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• Interest in this bacterium stems from its ability to manipulate host cell vesicular-trafficking pathways and establish a membrane-bound replication vacuole, making it model for intracellular or, more specifically, intravacuolar pathogens

HOW BACTERIUM THRIVE

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DR.T.V.RAO MD 12

COMPLEX MECHANISMS IN LEGIONELLA INFECTION

CLINICAL OBSERVATIONS

Wide age distribution Very high fever Diarrhoea Hepatorenal dysfunction Raised troponin T Often looked disproportionally well Sudden deterioration common

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CLINICAL PRESENTATIONS• Early Symptoms

• Malaise, muscle aches, lethargy and slight headaches.

• High Fever, non-productive cough, abdominal pain, diarrheal.

• Late Symptoms

• Extreme lethargy, comatose state

• Impaired kidney and liver functioning

• Nervous System disorders

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CLINICAL PRESENTATIONS OF LEGIONNAIRES DISEASE

• Legionnaires’ disease typically presents with pneumonia, which usually requires hospitalization and can be fatal in 10%–15% of cases. Symptom onset occurs 2–14 days after exposure. In outbreak settings, <5% of people exposed to the source of the outbreak develop Legionnaires’ disease.

DR.T.V.RAO MD 16

PONTIAC FEVER • Pontiac fever is milder than Legionnaires’ disease

and presents as an influenza like illness, with fever, headache, and myalgia's, but no signs of pneumonia. Pontiac fever can affect healthy people, as well as those with underlying illnesses, and symptoms occur within 72 hours of exposure. Most patients fully recover. Up to 95% of people exposed in outbreak settings can develop symptoms of Pontiac fever

Urinary antigen testing

SerologyCulture

LABORATORY DIAGNOSIS OF LEGIONELLA INFECTION

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WHO SHOULD BE TESTED FOR LEGIONNAIRES' DISEASE? IDSA GUIDELINES

• Hospitalized patients with enigmatic pneumonia

• Patients with enigmatic pneumonia sufficiently severe to require care in the ICU

• Compromised host with pneumonia

• Patients with pneumonia in the setting of a Legionellosis outbreak

• Patients who fail to respond to treatment to a ß-lactam or cephalosporin

• Patients with a travel history [Patients that have traveled away from their home within two weeks before the onset of illness.]

• Patients suspected of nosocomial pneumonia with unknown etiology

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• Urinary Antigen Test

• The serogroups of Legionella often times overlap with other immunocompromised diseases.

• Culture

• Lung biopsy, respiratory secretions, sputum

• Less preferable technique

DIAGNOSIS

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DIAGNOSIS• Isolation of Legionella from respiratory

secretions, lung tissue, pleural fluid, or a normally sterile site is an important method for diagnosis of Legionnaires’ disease. Clinical isolates are often necessary to interpret the findings of an environmental investigation. Because of differences in mechanism of disease, Legionella cannot be isolated in people who have Pontiac fever.

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• The culture method remains the "gold standard" for detecting Legionella from environmental sources. This technique, , requires up to 10 days to complete, precious time that could be used to pinpoint Legionella sources and prevent additional exposures.

CULTURING FOR LEGIONELLA

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PCR IN DIAGNOSIS OF LEGIONELLA INFECTION

• Another Legionella detection method is polymerase chain reaction (PCR), a molecular technique that offers a very sensitive method and only requires a few hours to complete. The PCR method provides an extremely powerful screening tool for the rapid Legionella detection in environmental samples, although it doesn't distinguish between living and dead cells. But unless the environment has been recently altered, such as with a biocide application, moderate to high populations of Legionella detected by PCR are usually indicative of an existing or potential future problem.

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DIAGNOSIS • The most used diagnostic method is the

Legionella urinary antigen assay. However, the assay can only detect L. pneumophila serogroups 1, the most common cause of Legionellosis. Paired serology showing a 4-fold rise in antibody titer between acute- and convalescent-phase specimens confirms the diagnosis. A single antibody titer of any level is not diagnostic of legionellosis.

DR.T.V.RAO MD 24

TREATMENT OF LEGIONELLOSIS • There is no vaccine for Legionellosis, and antibiotic

prophylaxis is not effective. Travellers at increased risk for infection, such as the elderly or those with immunocompromising conditions such as cancer or diabetes, may choose to avoid high-risk areas, such as whirlpool spas. If exposure cannot be avoided, travelers should be advised to seek medical attention promptly if they develop symptoms of Legionnaires’ disease or Pontiac fever.

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• Wide-range antibiotics to treat pneumonia

• Fluoroquinolones (levofloxacin, Moxifloxacin)

• Macrolides (azithromycin)

• Mechanism

• Quinolones: DNA gyrase inhibitors

• Macrolides: binds to 50S subunit of ribosomes

AN EFFECTIVE ANTIBIOTIC TREATMENT IS ESSENTIAL

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PREVENTION OF LEGIONELLA'S • Regularly maintain and clean cooling towers and evaporative

condensers to prevent growth of Legionnaires’ disease Bacteria (LDB). This should include twice-yearly cleaning and periodic use of chlorine or other effective biocide.

• Maintain domestic water heaters at 60°C (140°F). The temperature of the water should be 50°C (122°F) or higher at the faucet.

• Avoid conditions that allow water to stagnate. Large water-storage tanks exposed to sunlight can produce warm conditions favourable to high levels of LDB. Frequent flushing of unused water lines will help alleviate stagnation.

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MEASURES TO TRAVELLERS • There is no vaccine for Legionellosis, and antibiotic

prophylaxis is not effective. Travellers at increased risk for infection, such as the elderly or those with immunocompromising conditions such as cancer or diabetes, may choose to avoid high-risk areas, such as whirlpool spas. If exposure cannot be avoided, travellers should be advised to seek medical attention promptly if they develop symptoms of Legionnaires’ disease or Pontiac fever.

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