Small Group: Anaerobic Bacterial Infections

Question 1

1. Name the organism (genus and species) that is the most common cause of gas gangrene.

Answer 1

Clostridium perfringens

Question 2

2. Define and explain the terms debridement and crepitation. Note: crepitus and crepitation are interchangeable.

Answer 2

debridement: removal of devitalized tissue
crepitation: build up of gas in subcutaneous tissues usually due to C. perfingens

grating, crackling or popping sounds and sensations experienced under the skin and joints or a crackling sensation due to the presence of air in the subcutaneous tissue.

Question 3

1. Discuss the microbiological and physiological predisposing factors for the development of gas gangrene.

Answer 3

poorly controlled diabetes (circulatory damage and nerophahy)
high blood pressure can effect PMN function
previous infection or colonization
open infection (culture medium)
increased age
hygiene

Question 4

2. Explain the rationale of antibiotic treatment in the containment of gas gangrene and the reasons that containment is difficult.

Answer 4

poor circulation to site of infection because of tissue damage

devitalized tissue may serve as a reservoir of infection if not removed

Question 5

3. Discuss and evaluate the role of debridement in the treatment of gas gangrene.

Answer 5

very important in removing devitalized tissue (anaerobic culture) and organism burden (decrease bug, decrease a toxin)

Question 6

4. Explain the role of clinical findings and laboratory testing to diagnose cases of gangrene.

Answer 6

can be important in syndrome recognition, testing may be time consuming and organism may be difficult to grow

Question 7

5. Explain the importance of appropriate specimen collection and handling when anaerobes are suspected.

Answer 7

transport with an anaerobic chamber with reducing agents and anaerobic transport media, may be fastidious to grow

Question 8

6. List the clinical signs of gas gangrene.

Answer 8

crepitus, dishwater discharge, early onset of pain, rapid evolution of damage, cyanosis

Question 9

1. Name the organism (genus and species) most commonly associated with antibiotic associated diarrhea.

Answer 9

Clostridium dificile

Question 10

2. Explain why this organism is problematic as a hospital-acquired pathogen, how it is transmitted and what preventative strategies can be used to reduce rates.

Answer 10

can be spread by very hardy spores (shed in feces) that are not killed by certain cleaning products

requires practitioners to wash their hands with soap and water and also for rooms to be cleaned with a chlorine solution

can be transmitted on hands, equipment, bedding etc.

Question 11

3. Describe the disease spectrum seen with this organisms.

Answer 11

patients can be asymptomatic or they can have membranous colitis, require colectomy or die (Septicemia or antibiotic resistance), most common can be mild-severe diarrhea that is persistent (strains that do not produce the a toxin is not pathogenic, cannot tell without PCR)

Question 12

4. Discuss therapeutic strategies that can be used to treat this disease.

Answer 12

limit antibiotic use, private rooms (continue precaution until diarrhea stops
tx: oral vancomycin or or oral metronidazole, fidaxomicin ($$ less relapse)
probiotics or fecal transplant
IV IgG from donor antibodies to help against C. diff toxin

shorten hospital time, reduce GI surgery (advanced age is also a risk factor)

Question 13

5. Discuss reasons why recurrences are common for this disease.

Answer 13

relapse (spores remain in gut) or reinfection

patient may not develop antibodies to the toxin

Question 14

1. Name the most common genera of normal anaerobic and facultative gut microflora (bacteria.)

Answer 14

Bacteriodes fagilus

Question 15

2. Explain the biphasic development of peritonitis as it relates to aerobes or facultative anaerobes v. strictly anaerobic bacteria.

Answer 15

anaerobe infection creates devitalized tissue infection that allows for the growth of anaerobic organisms

Phase I occurs in peritoneal fluid and phase 2 at localized sites

Question 16

1. Name the common genera of microflora found in the oral cavity.

Answer 16

Provetella
Fusiform
Peptostreptococci
Bacterioides
Streptococci
Lactobaccilli
Staphylococci

Question 17

2. Define the term “aspiration pneumonia.”

Answer 17

foods, liquids or saliva from the mouth enter into the respiratory system and cause an inflammatory (infection)

possible complications include empyema

Question 18

1. List and discus the major conditions predisposing a patient to aspiration pneumonia and relate each to the host defenses that are defeated.

Answer 18

alcohol, smoking, poor dentition, esophageal motility, stroke, Epilepsy, drug use, GERD, head and neck cancers, MS, ALS, nasogastric tube

inhalation of fluids blocks airway (vomitus or other liquid)

Question 19

2. Identify the most common bacterial agents (to genus) involved in aspiration pneumonia.

Answer 19

Provatella
Fusiform
Peptostreptococcus
+ anything living in the mouth

use clindamycin or ampicillin/sulbactam to treat

Question 20

3. List and describe those conditions within the lung that can lead to development of an anaerobic microenvironment.

Answer 20

obstruction of the alveoli (COPD, foreign body etc.)

disruption of blood flow (ie. PE)