Dr. Ramkesh Prasad
Department of Community Medicine
Gauhati Medical College
Caused by Legionella pneumophila
Ranks fourth among the causes of pneumonia
(S. pneumoniae, H. influenzae, Chlamydophila
One of the atypical pneumonias, Gram stained
sputum smear does not show organisms.
Each year, between 8,000 and 18,000 people are
hospitalized with Legionnaires' disease in the
While Legionellae are ubiquitous in freshwater
environments, and likely have been for
centuries, it is their unique growth
requirements in the environment coupled with
the advent of human technology favoring
complex water systems that has led to the
designation of legionellosis as an emerging
infectious disease in the late twentieth century.
Year City Venue Source Cases Deaths
Benidorm, Spain Rio Park Hotel Not known 4 4 100%
221 34 15.4%
175 28 16.0%
Hot tub 318 32 10.0%
2005 Toronto, Canada
Home for the
Cooling tower 127 21 16.5%
Year City Venue Source Cases Deaths
Cooling tower 95
Murcia, Spain Hospital Cooling towers
Air conditioning 172 7 4.1%
Factory Air scrubber 56 4 4.2%
2008 New Jersey
Drinking water 6 3 0.3%
Feb 2012 Calp, Spain
Not known 14 3 17%
The 1976 Philadelphia epidemic
Legionnaires' disease was first recognized as a
distinct entity during an epidemic of
pneumonia that occurred in Philadelphia, in
About 4,000 members of the Pennsylvania State
American Legion, an organization of former military
veterans, met in July for American Bicentennial
celebration, which lasted from 21 - 24 July.
On 27th July, one of the legionnaire died of a
pneumonia like illness
On 30th July a physician in Bloomsburg, realized that the 3 patients he was
treating from similar condition had all attended the convention
On the same day, a nurse in Chambersburg Hospital noted a similar
condition in 3 patients who had gone to the convention
By Aug 2nd it was realized that there was some undeniable connection
By August, 18 legionnaires had already died, it attracted huge media
Out of the 221 cases - 72 were people who were not involved in the
American Legion convention - people who had either been inside the
Bellevue Stratford Hotel, or had walked past it.
On January 18, 1977 CDC announced that the cause of Legionnaire’s
disease was isolated. (Thanks to the works of Dr Joseph McDade * )
The source of the breeding site of the organism traced to the cooling
towers that were connected to the air conditioners of the hotel.
Gram negative, aerobic bacteria
bacterial cells are 0.5–1 µm wide and 2–50 µm long
and motile, with one or more polar or lateral
Do not grow on routine microbiologic media.
Requires Iron, L cystiene and temperature 25-45 °C
Grown on Buffered charcoal yeast extract (BCYE)
Found in lakes, streams, and other bodies of water,
Grows inside free living ameba (Acanthameba, Naegleria,
Grows best in warm water, like
in hot tubs,
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
Age: Elderly are more susceptible
chronic lung disease;
treatment with glucocorticoids or tumor necrosis
Inhalation of Legionellae in aerosolized droplets is the primary means of
These aerosolized droplets must be of a respirable size (1–5 μm).
No person-to-person transmission of Legionnaires’ disease has been
A number of devices have been implicated as sources of aerosol transmission of
These sources are associated with both potable and non-potable water.
Sources producing aerosols of contaminated potable water include showers,
faucets, and respiratory therapy equipment.
Sources utilizing non-potable water include cooling towers, heated spas,
decorative fountains, humidifiers, ultrasonic mist machines, and industrial
exposure to aquatic settings that promote
bacterial growth—the aquatic environment is
the water is warm (25°C – 42°C),
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
Legionella enters the lungs through aspiration or
Attachment to host cells is mediated by bacterial
type IV pili, heat-shock proteins, a major outer-
membrane protein, and complement.
Because the organism possesses pili that mediate
adherence to respiratory tract epithelial cells,
conditions that impair mucociliary clearance,
including cigarette smoking, lung disease, or
alcoholism, predispose to Legionnaires' disease.
Mortality rates vary with
patient's underlying disease and its severity,
the patient's immune status,
the severity of pneumonia, and
the timing of administration of appropriate
With appropriate and timely antibiotic treatment,
mortality rates in immunocompetent patients
range from 0 to 11%;
without treatment, the figure may be as high as 31%
There is no vaccine for legionellosis,
Antibiotic prophylaxis is not effective always.
Travelers 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
Chemoprophylaxis with a macrolide antibiotic has
been effective in immunocompromised patients
during nosocomial epidemics of the disease
Routine environmental culture of hospital water
supplies is recommended as an approach to the
prevention of hospital-acquired Legionnaires'
Hyperchlorination and superheating of water can
help control the multiplication of legionellae in
water and in air-conditioning systems.
Use of monochloramine, rather than chlorine to
treat public drinking water to reduce colonization
Proper building and plumbing design and
construction can reduce frequency and intensity of L.
pneumophila contamination of potable water.
Proper insulation of hot water pipes to prevent
warming of water in adjacent cold water pipes.
Maintaining hot water temperature above 50 °C and
cold water below 20 °C
Recreational spas must be properly constructed,
regularly maintained and closely monitored to
prevent high level of bacterial growth.
An acute, self-limiting, flu-like illness with an
incubation period of 24–48 h. Pneumonia does
Malaise, fatigue, and myalgia are the most
Complete recovery occurs within a few days;
antibiotic therapy is unnecessary.
Agrawal L, Dhunjibhoy KR, Nair KG. Isolation of
Legionella pneumophila from patients of respiratory tract
disease and environmental samples. Indian J Med Res 1991;
In this preliminary study, 45 patients suffering from
pneumonia were screened for L. pneumophila.
17 random environmental samples, water from a cooling
system used for air conditioning units, and samples from a
respirator-humidifier were screened.
Four of the 45 clinical specimens (9 %) and 13 of the 17
environmental samples (76 %) showed the presence of L.
pneumophila. This is the 1st report from India of the
isolation of L. pneumophila
Chaudhry R, Dhawan B, Dey AB. The incidence of
Legionella pneumophila: a prospective study in a tertiary
care hospital in India. Trop Doct 2000; 30: 197-200.
Between April 1997 and December 1998, 60 patients with CAP
admitted to the All India Institute of Medical Sciences were
included in the study.
Etiological diagnosis was based on the results of routine
microbiological blood culture for bacteria and serological test by
ELISA for L. pneumophila serogroup 1-7.
Eight patients (13 %) had a conventional bacterial etiology and 9
patients (15 %) had serological evidence of recent infection with L.
Sero diagnosis of Legionella infection in community
acquired pneumonia, Sabah Javed, Rama Chaudhry, Kapil
Passi, Sutikshan Sharma, Padmaja K., Benu Dhawan &
A.B. Dey, Indian J Med Res 131, January 2010, pp 92-96
All 113 clinical samples of paediatric (27) and
adult (86) patients were collected during May 2005
to January 2008 on their first visit to the AIIMS,
New Delhi, with the symptoms of pneumonia
Thirty one of the 113 cases (27.43%) were
Isolation of Legionella pneumophila from clinical &
environmental sources in a tertiary care hospital, S.
Anbumani, A. Gururajkumar & A. Chaudhury, Indian J
Med Res 131, June 2010, pp 761-764
Study done at Sri Venkateswara Institute of Medical Sciences,
A total of 470 lower respiratory tract samples and 24
water samples from hospital outlets were examined.
Culture was done on buffered charcoal yeast extract
agar with supplements and identification of the
isolates was done by microscopy and biochemical tests.
L. pneumophila could be isolated from 12 (2.55%)
patients suffering from community-acquired lower
respiratory tract infection, unassociated with other
aetiological agents of bacterial pneumonia. Of the 24
water samples tested, 8 (33.3%) grew the same
A 53 years old British tourist had come to India in
November 2003, and had visited Delhi, Agra, Jaipur,
and Goa. He went back to the United Kingdom on 5
Dec 2003 and died 2 days later.
According to the British High Commission, the
person died of Legionnaire’s disease
It was no ordinary microbe. It could not be grown
under typical conditions, being dependent upon
ridiculous demands: high levels of the amino acid
cysteine and inorganic iron supplements, low
sodium concentrations, as well as activated
charcoal to absorb free radicals. In addition, it
preferred elevated temperatures, which was highly
abnormal among pathogens, who preferred near-
It did not help that the team of CDC researchers
had been using the wrong animal model at the
start, and had only gotten results when they
switched from mice to guinea pigs
Dr Carl Fliermans solved the first part of the puzzle
when he discovered that L pneumophila lipids
resembled those of the thermophilic bacteria he'd
found in the thermal regions of the Yellowstone
National Park, and that this bacteria tended to live as
biofilm (scum) associated with certain species of algae.
Subsequently, Fliermans began poking around aquatic
habitats and found - guess what? - this bacteria
residing in thermal waters discharged from a nuclear
reactor at Savannah River Laboratory.
This bacteria was later found to be living in natural hot
springs all over the United States and, most
importantly, in air-conditioning cooling towers.
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