Anaerobic Bacteriology Introduction

Question 1

Objective 1: Define the following terms: anaerobe

Answer 1

Anaerobe: a bacterium that is able to replicate without oxygen

Question 2

Objective 1: Define the following terms: polymicrobial

Answer 2

Polymicrobial: refers to multiple isolates of bacteria

Question 3

Objective 1: Define the following terms: pleomorphic

Answer 3

Pleomorphic: an bacterium that displays many gram stain morphologies (shapes and forms)

Question 4

Objective 2: **Differentiate between the following:
- Obligate aerobe
- Example

Answer 4

• Microorganism that requires oxygen for growth
• Pseudomonas spp., Micrococcus spp.

Question 5

Objective 2: **Differentiate between the following:
- Microaerophile
- Example

Answer 5

• Microorganism that grows in conditions of reduced oxygen and increased carbon dioxide
• Campylobacter spp.

Question 6

Objective 2: **Differentiate between the following:
- Facultative anaerobe
- Example

Answer 6

• Microorganism that does not require oxygen for growth, but will use oxygen and grow better if present
• E. coli, S. aureus

Question 7

Objective 2: **Differentiate between the following:
- Aerotolerant anaerobe
- Example

Answer 7

• Microorganism that grows best in the absence of oxygen, but can tolerate low concentrations of oxygen
• Propionibacterium, C. tertium, C. carnis, C. histolyticum

Question 8

**Differentiate between the following:
- Strict obligate anaerobe
- Example

Answer 8

• Microorganism that can only live and reproduce in a anaerobic environment
• C. novyi, C. haemolyticum

Question 9

Objective 3: Recognize in which categories most aerobes and anaerobes fit

Answer 9

• Aerobes: Facultative anaerobes
• Anaerobes: Aerotolerant anaerobes

Question 10

Objective 4: **Identify the sites where anaerobes are found as normal flora

Answer 10

• Nose
• Mouth
• Oropharynx
• Skin
• GI
• GU/Vaginal

Question 11

Objective 5: Differentiate between endogenous and exogenous infections in relationship to
anaerobes

Answer 11

Endogenous: the result of anaerobes that are normal flora of the body
Exogenous: the result of anaerobes that are located outside of the body

Question 12

Objective 6: **Recognize which source of anaerobes (exogenous or endogenous) is most common
in anaerobic infections

Answer 12

Endogenous

Question 13

Objective 7: Discuss the reason(s) that most anaerobic infections are polymicrobial

Answer 13

Lowers the redox potential of the environment creating a suitable environment for anaerobic growth

Question 14

Objective 8: Recognize the types of infections routinely caused by anaerobes

Answer 14

• Dental infections
• Intra-abdominal/Pelvic abscess
• Brain abscess
• Lung abscess
• Bacteremia

Question 15

Objective 9: List factors that predispose a person to anaerobic infection and signs of an anaerobic infection

Answer 15

• Vascular stasis
• Tooth extraction/oral surgery
• GI tract surgery/traumatic puncture of bowel
• Infection close to site containing normal flora
• Necrotic tissue
• Foul odor

Question 16

Objective 10: **Recognize the types of clinical specimens that are acceptable for anaerobic culture
and those not acceptable for culture

Answer 16

Acceptable:
- Needle aspirates
- Tissue or bone
- Sterile body fluids (except urine)

Not acceptable:
- Upper respiratory specimens
- Surface wounds
- Stool (except C. diff)

Question 17

Objective 11: Describe why aspirated specimens are preferred over specimens submitted on swabs

Answer 17

Swabs collect less material and likely to possess contaminated flora

Question 18

Objective 12: Discuss why the source (site) from which the specimen was collected affects its acceptability

Answer 18

Most anaerobic infections are endogenous – must differentiate if the organism is part of the infectious process and not normal flora

Question 19

Objective 15: Discuss the 3 supplemental requirements for anaerobic media and the storage
conditions necessary for maintaining anaerobic media

Answer 19

1. Vitamin K
2. Hemin
3. Yeast extract

Stored at room temperature
Pre-reduced (ensures redox potential stays low)

Question 20

Objective 16: **List the factor that has the largest impact on the oxidation-reduction potential of
anaerobic media.

Answer 20

pH

Question 21

Objective 17: List 5 reducing agents that can be added to media to maintain an anaerobic environment

Answer 21

1. Enriched thioglycollate (THIO)
2. Chopped meat
3. Serum
4. Cysteine
5. Rumen Fluid

Question 22

Objective 18: Define the term PRAS

Answer 22

Pre-Reduced Anaerobically Sterilized

Question 23

Objective 19: **Discuss the purpose of the various plating media presented in lecture (ABAP, PEA,
KV/PV, LKV, BBE).

Answer 23

ABAP (Anaerobic Blood Plate Agar)
- non-selective (anything that will grow in an anaerobic
environment will grow on this plate)

PEA
- selective from a mixed culture
- selective for anaerobes
- inhibits facultative anaerobic GNRs
- inhibits Proteus swarming

KV/PV/LKV (antibiotics w/ laked blood)
- selective for Gram negative anaerobes

BBE (Bacteroides Bile Esculin)
- selective for Bacteroides spp. (bile)
- differential for esculin hydrolysis (media turns black)

Question 24

Objective 20: Describe 3 anaerobic systems used in clinical laboratories

Answer 24

1. Anaerobic chambers
2. Anaerobic jars
3. Anaerobic bags and pouches

Question 25

Objective 21: **Differentiate between ambient air, CO2, microaerophilic and anaerobic incubation conditions (% of O2 and % of CO2)

Answer 25

Ambient air: 21 O2, 0.03 CO2 CO2: 15-21 O2, 5-10 CO2 Microaerophilic: 5 O2, 10 CO2 Anaerobic: 0 O2, 5-10 CO2

Question 26

Objective 22: List the 4 requirements of an anaerobe chamber

Answer 26

1. Catalyst 2. Desiccant 3. Anaerobic gas (5 H2, 5-10 CO2, 85-90 N2) 4. Redox indicator

Question 27

Objective 23: Recognize the typical catalyst used in an anaerobe chamber

Answer 27

Palladium coated aluminum pellets

Question 28

Objective 24: Identify a desiccant used in anaerobe chambers

Answer 28

Silica gel

Question 29

Objective 25: Recognize the typical gas mixture in an anaerobe chamber

Answer 29

5 H2, 5-10 CO2, 85-90 N2

Question 30

Objective 26: List 2 oxidation reduction indicators used in anaerobe chambers.

Answer 30

1. Methylene blue 2. Resazurin

Question 31

Objective 28: List the major advantages and disadvantages of anaerobe chambers, anaerobe jars, and anaerobe bags/pouches

Answer 31

Anaerobe chambers Advantage: - Specimens never exposed to oxygen during set up - Plates can be screened as often as desired - Large volume cultures Disadvantage: - Cumbersome - Airlock - Space Anaerobe jars Disadvantage: - Plates must be removed to screen Anaerobe bags/pouches Advantage: - Transport, esp. when delay is expected

Question 32

Objective 30: Recognize the importance of incubating anaerobe plates and biochemicals for 48 hours

Answer 32

Anaerobes are susceptible in the first 48 hours of growth -- may inhibit growth or kill some organisms

Question 33

Objective 32: Recognize the form of Gas Liquid Chromatography most commonly used (volatile vs. non-volatile).

Answer 33

Volatile

Question 34

Objective 33: Identify 3 tests for proteolysis

Answer 34

1. Gelatin hydrolysis 2. Milk liquefaction 3. Meat digestion