Lecture 1 - Intro to Anaerobes

Question 1

Classify clinically important anaerobes.

Answer 1

Question 2

Classification of Bacteria #1

Answer 2

Question 3

Classification of Bacteria #2

Answer 3

Question 4

Characteristics of Anaerobes #1, where are they usually found and hence how do they cause infection?

Answer 4

They are ubiquitous and commensals of skin, pulmonary, intestinal and
urogenital tracts and so in infections the sources of the infecting microbes are mostly the host’s endogenous flora. An alteration of the host’s tissue provide suitable niche for acquiring
opportunistic infection (eg trauma, other infections).

Question 5

Characteristics of Anaerobes #2, 1. how pathogenic are anaerobes and when are they usually seen in infections, 2. In anaerobic infections what do they cause and produce?

Answer 5

1. They are weak pathogens but are involved in polymicrobial infections with aerobes.
2. They are supparative, causing abscess formation and tissue necrosis and often
   gas formation and some produce most potent paralytic toxins

Question 6

Epidemiology # 1, where are anaerobes usually found?

Answer 6

They are widespread and found in soil, water, food and on animals as well as form a prevalent proportion of the normal flora of the body.

Question 7

Epidemiology #2, what are the incidence numbers for bacteremic episodes in cases of anaerobic infections?

Answer 7

They vary but are roughly between 5-15%

Question 8

Epidemiology #3, what are the commonest isolates of anaerobes?

Answer 8

Bacteroides fragilis (75%), Clostridium spp (10-20%), Peptostreptococcus and Fusobacterium spp (10-15%), Propionibacteriun acnes (2-5%)

Question 9

Epidemiology #4, how are exogenous infections caused by anaerobes?

Answer 9

People come into contact with spore -forming organisms in soil, water and sewage. (Less likely but also possibly in food or on/near animals).

Question 10

Epidemiology #5, which anaerobes cause endogenous infections (indigenous flora) and where are they found?

Answer 10

Skin:Propionibacterium, Peptostreptococcus
Upperrespiratory: Propionibacterium Mouth:Fusobacterium,Actinomyces
Intestines:Clostridium,Bacteroides, Fusobacterium
Vagina:Lactobacillus

Question 11

Classify Bacteria in Relation to Aerotolerance #1

Answer 11

Question 12

Classify Bacteria in Relation to Aerotolerance #2

Answer 12

Question 13

Epidemiology #6 - with regard to Endogenous infections where the infectious agent already resided within the body

Answer 13

Question 14

Epidemiology #7 - with regard to exogenous infections where the infecting agent is from and resided outside the body prior to infecting the host

Answer 14

Question 15

Describe the Pathogenesis of Anaerobic Infections

Answer 15