Lecture 6 MISCELLANEOUS…BUT IMPORTANT GRAM NEGATIVE BACTERIA Flashcards
Learning outcomes
- Describe the transmission, epidemiology,
and diseases caused by - Legionella sp
- Bordetella pertussis
- Gram-negative obligate anaerobes
Fastidious Gram-negative Rods:
Legionella pneumophila: Legionaire’s Disease
Bordetella pertussis: Whooping Cough
Haemophilus influenzae: meningitis and septicaemia in children < 6 months
Gram-negative obligate anaerobes (very diverse group):
have to live in an environment without oxygen
Bacteroides
Fusobacterium
Prevotella
Porphyromonas
LEGIONELLA PNEUMOPHILA
- L. pneumophila lipids resembled those of the thermophilic
bacteria in Yellowstone National Park, and that this bacteria
tended to live as biofilm
-biofilm is a strucutre formed by bacteria
-Dr Carl fliermans
* Discovered the bacteria in thermal waters discharged from
nuclear reactor at Savannah River Laboratory. Later in natural
hot springs, air-conditioning systems and cooling towers
-Biofilm is a structure bacteria like to live in
-90% of legionella diseases are caused by this
CHARACTERISTICS OF THE GENUS LEGIONELLA
- Type species is Legionella pneumophila
- 42 species characterised, 18 associated with human illness, LP 85% of cases
- Non-spore forming, Gram-negative rods that vary from short thin forms to longer filamentous forms
- Most species motile via a single polar flagellum
- Aerobic
- Grow in tap water and water but in artificial media are nutritionally fastidious !
-it is fastidious because it is very hard to culture in lab conditions
Key facts (W.H.O. 2019) Legionellosis
- The most common form of transmission of Legionella is inhalation of
contaminated aerosols produced in conjunction with water sprays, jets
or mists. - Infection can also occur by aspiration of contaminated water or ice,
particularly in susceptible hospital patients. enjoys growing in stagnant water that is not flushed enough - Legionnaires’ disease has an incubation period of 2 to 10 days (but up
to 16 days has been recorded in some outbreaks). - Death occurs through progressive pneumonia with respiratory failure
and/or toxic shock and multi-organ failure. - Untreated Legionnaires’ disease usually worsens during the first
week. - Of the reported cases 75–80% are over 50 years and 60–70% are
male. - Community, travel or hospital acquired
LEGIONNAIRE’S DISEASE
- Acute pneumonia. Bacterium multiplies
in alveolar macrophages - the bacterium causes macrophages to produce cytokines, these are small proteins, immune mediators that act as chemical messengers in the immune system, signaling cells to fight threats and regulate inflammation, they elicit an influx of monocytes and polymorphonuclear
cells (types of white blood cells - this results in Obliteration of the air spaces which compromises respiratory function
- and causes Fevers, Cough, Breathlessness
LEGIONELLA IN THE ENVIRONMENT
legionella can infect and survive in amoeba so is a way in which legionella can survive in stagnant water and protect it from chemicals such as chlorine and handwashing
CHAIN OF CAUSATION FOR LEGIONELLA INFECTION
BORDETELLA PERTUSSIS: PHYLOGENY
BORDETELLA PERTUSSIS:GENERAL CHARACTERISTICS
-Aerobic, Gram negative, small
coccobacillus, short rods, has a metallically colour
-Specific only to humans
-Colonizes the respiratory tract to
cause Whooping Cough
(Pertussis)
-Today, whooping cough still effects
20-40 million people worldwide/year
and causes between 200,000-
400,000 fatalities
BORDETELLA PERTUSSIS: DISEASE
Symptoms
-dry and sticky mouth
- sleepiness and tiredness
- reduced urination
-no tears whilst crying
-whooping cough
-cough with fever and muscle aches
Transmission via droplets/inhalation
Colonization of upper respiratory tract, production
of toxins
Incubation period: 5-10 days
Catarrhal stage: ~ 1-2 weeks rhinorrhoea (nasal inflammation) and
mild cough
Paroxysmal stage: ~1-6 weeks , can go on for 6 months, 5-20 forceful, hacking successive coughs, title time for breathing, whoop when air rushes back into the lungs
Vomiting and frequent coughing exhausts child
- common in infants and young children
Complications - pneumonia, otitis media, asthma
BORDETELLA PERTUSSIS: EPIDEMIOLOGY
vaccination has been very important in tackling the disease
BORDETELLA PERTUSSIS: EPIDEMIOLOGY
- Increased awareness & better detection methods
- Waning immunity as many cases are in older children and adults?
- Acellular vaccines provide a shorter duration of protection?
- Vaccine research ongoing…correlate of protection?
- COVID-19?
GRAM-NEGATIVE OBLIGATE ANAEROBES
Colonise the human body’s anaerobic environments in huge numbers (large
bowel)
Predominant bacteria in upper respiratory tract, GI and GU tract
Outnumber aerobic bacteria by 10-100 fold
Many species, but few pathogens
Clinical Diseases
-Periodontal infections
-Abscess
-Intra-abdominal infections
-Gynecological infections
-Skin and soft tissue
Bacteriodes fragilis is associated with 80% of intra-abdominal infections- is fine when it is in your GI tract or bowel but can become a problem due to outgrowth when theyre in places where they should not be as they can then cause various diseases
Often polymicrobial infections
