Download Legionnaire’s Disease - Newcastle University

By Louis Martin
The organism behind the disease:
•Legionnaire’s disease, or Legionellosis , is a very
severe type of pneumonia.
•It is caused by the bacterium known as Legionella
pneumophila.
•As you can see from the images to the right,
L. pneumophila is a rod bacterium which may or may
not have flagellum.
•The bacterium is also gram negative, a quality which
is characteristic of pathogenic organisms. The cells do
not stain due to the lipopolysaccharides in the cellular
membrane.
•The lipopolysaccharides do many things for the
bacterium, most importantly they present antigens
which, when combined with gram negative bacteria,
can be modified so that the immune system initially
does not see the pathogens as a threat, therefore
does not attempt to destroy the infection.
•The lipopolysaccharides also help to strengthen the
cell membranes, providing greater cellular integrity.
L. pneumophila
•The first diagnosed case of legionnaire’s disease was in 1976 when many people who had been
attending a legions convention in America were struck down with pneumonia, it was found that they
had an unrecognised bacterial infection, this bacteria was named Legionella pneumophila.
•In time it was discovered that the bacteria had came from the contaminated water cooling system
used in the air conditioning of the hotel.
•The bacteria lives in stagnant water, in this case the cooling system of the air conditioning. It reached
the people as it became air born inside the air conditioning unit and was pumped around the hotel
until it was inhaled by the attendees of the convention.
•Its capability to modify its antigens, allowed it to enter its hosts and overcome their immune systems,
the bacteria's optimum conditions are moist areas with a temperature in the region of 35-45 degrees
Celsius, so naturally they will grow rapidly once inside a human body.
•Since the identification of the bacterium, many have been found particularly in man made water
devices such as showers, Jacuzzis, water fountains and room-air humidifiers, basically in any water
using devices.
•In nature it has been found that the bacteria can live in warm stagnant water quite happily and certain
strains of the bacteria can even grow in soil.
•The disease is spread by the inhalation of water mist from contaminated water.
•The bacteria can be grown in a lab by cultivating lung tissue with the bacteria and keeping it at an
optimum temperature of approximately 37 degrees Celsius.
•The bacteria can be identified using its unique antigens or comparing the genome of the bacteria with
other bacteria for possible matches and also by using direct fluorescent antibody staining on an
infected tissue such as lung tissue.
Disease process:
Symptoms of the Disease:
•High fever
•Chills
•Muscle ache
•Cough which will likely
eventually produce
bloody sputum
•Fatigue
•Loss of appetite
•Pneumonia
1--------------- Days-------------10
•Head aches
1.
L.Pneumophila enters the
body
2.
The bacteria are inhaled
into the lungs
3.
The bacteria are attacked
and engulfed by the bodies
phagocytes via
phagocytosis
4.
Due to its special structure
the phagocytes are unable
to digest the swallowed
bacteria so the bacteria
continue to live and they
replicate
5.
After many replications the
phagocyte dies and bursts
releasing many more
L.pneumophila into the
lungs thus strengthening
the infection.
6.
This continues for 1-10
days as the disease
becomes more severe
causing the pneumonia
•The most common way to treat the disease is with drugs, there are many different
types but the two main categories are quinolones and the more modern macrolides.
•The most popular of each group being levofloxacin and azithromycin respectively.
•These tend to be the most effective as they can enter cells with relative ease and
attack the L. pneumophila inside the cells, where as other antibiotics such as penicillin
are poor at entering cells.
•The macrolides can be used on any age group but the quinolones can only be used on
people who are 18 or over.
•At this current moment in time there is nothing more effective than these drugs in the
fight against legionnaire’s disease, however the genome of L. pneumophila has been
completely mapped and scientists believe that soon they will be able to use its genetic
coding to create an effective vaccine.
As of yet there is no vaccination for legionnaire’s disease, however there are steps which can
be taken which will radically reduce the chances of bacterial growth and infection.
The bacteria can grow naturally in the wild but most cases of human infection tend to show
the source of the bacteria being industrial equipment where the water is contaminated, many
cases tend to be water cooling towers.
The main ways of prevention and control is just to ensure that any equipment, which may be
in contact with stagnant water regularly, is cleaned thoroughly and regularly.
The cleaning process involves chemical disinfectant cleaning with chlorine containing
compounds, and also mechanical cleaning to ensure all bacteria containing grime and gunk
is removed from the surfaces which come in contact with the water.
For full cleaning procedures see:
http://www.cdc.gov/ncidod/dhqp/pdf/guidelines/Enviro_guide_03.pdf (pages 239-240)
http://www.niehs.nih.gov/external/faq/legion.htm
http://www.cdc.gov/ncidod/dbmd/diseaseinfo/legionellosis_g.htm
http://www.osha.gov/dts/osta/otm/legionnaires/disease_rec.html#Causative
pages 802/807 in brock microbiology book.
http://en.wikipedia.org/wiki/Legionella_pneumophila
http://news.bbc.co.uk/1/shared/spl/hi/health/03/travel_health/diseases/html/legionnaires.stm
http://en.wikipedia.org/wiki/Legionellosis#Diagnosis_and_treatment
http://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_7.html#2-control and prevention
http://news.bbc.co.uk/2/hi/science/nature/3677756.stm
http://www.cdc.gov/ncidod/dhqp/pdf/gui
http://www.google.co.uk/imghp?hl=en&tab=wi&q=