Lecture 6 MISCELLANEOUS…BUT IMPORTANT GRAM NEGATIVE BACTERIA

Question 1

Learning outcomes

Answer 1

• Describe the transmission, epidemiology,
  and diseases caused by
• Legionella sp
• Bordetella pertussis
• Gram-negative obligate anaerobes

Question 2

Fastidious Gram-negative Rods:

Answer 2

Legionella pneumophila: Legionaire’s Disease

Bordetella pertussis: Whooping Cough

Haemophilus influenzae: meningitis and septicaemia in children < 6 months

Question 3

Gram-negative obligate anaerobes (very diverse group):

Answer 3

Bacteroides
Fusobacterium
Prevotella
Porphyromonas

Question 4

LEGIONELLA PNEUMOPHILA

Answer 4

• L. pneumophila lipids resembled those of the thermophilic
  bacteria in Yellowstone National Park, and that this bacteria
  tended to live as biofilm

-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

Question 5

CHARACTERISTICS OF THE GENUS LEGIONELLA

Answer 5

• 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

Question 6

Key facts (W.H.O. 2019) Legionellosis

Answer 6

• 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.
• 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

Question 7

LEGIONNAIRE’S DISEASE

Answer 7

• Acute pneumonia. Bacterium multiplies
  in alveolar macrophages
• Produce cytokines that elicit an influx of monocytes and polymorphonuclear
  cells
• Obliteration of the air spaces
  compromises respiratory function
• Fevers, Cough, Breathlessness

Question 8

LEGIONELLA IN THE ENVIRONMENT

Answer 8

Question 9

CHAIN OF CAUSATION FOR LEGIONELLA INFECTION

Answer 9

Question 10

BORDETELLA PERTUSSIS: PHYLOGENY

Answer 10

Question 11

BORDETELLA PERTUSSIS:GENERAL CHARACTERISTICS

Answer 11

-Aerobic, Gram negative, small
coccobacillus

-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

Question 12

BORDETELLA PERTUSSIS: DISEASE

Answer 12

Transmission via droplets/inhalation

Colonization of upper respiratory tract, production
of toxins

Incubation period: 5-10 days

Catarrhal stage: ~ 1-2 weeks rhinorrhoea 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

Complications - pneumonia, otitis media, asthma

Question 13

BORDETELLA PERTUSSIS: EPIDEMIOLOGY

Answer 13

Question 14

BORDETELLA PERTUSSIS: EPIDEMIOLOGY

Answer 14

• 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?

Question 15

GRAM-NEGATIVE OBLIGATE ANAEROBES

Answer 15

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

Often polymicrobial infections

Question 16

GRAM-NEGATIVE OBLIGATE ANAEROBES

Answer 16

• Bacteriodes: most commonly found
  anaerobes, intra-abdominal infections and abcesses, eg. B. fragilis
• Acute nectrotizing gingivitis: Caused by a mixed bacterial infection that includes anaerobes such as Prevotella, Fusobacterium and spirochetes, such as Treponema

Question 17

FURTHER READING: Legionella and Bordetella

Answer 17

• Khodr et al., Molecular epidemiology, phylogeny and evolution of
  Legionella. Infection, Genetics and Evolution 43 (2016) 108–122
• Nieves and Heininger. Bordetella pertussis. Microbiol Spectr. 2016
  Jun;4(3) doi: 10.1128/microbiolspec.EI10-0008-2015.