Anaerobes, Lecture 7

Question 1

Anaerobe Definition

Answer 1

• Lack Super Oxide Dismutase and oxygen is toxic.
• Many are facultative anaerobes that like low Eh
• Large contributor to normal flora in gut and mouth

Question 2

Metronidazole

Answer 2

• Metabolized intracellularly by anaerobic bacteria and generates toxic metabolite that injures DNA.
• Highly effective against Clostridium and gm+ anaerobes, also some against others.
• Highly available and enters CNS.
• Has major interaction with alcohol and leaves patient sick

Question 3

Clindamycin (lincosamide)

Answer 3

• Binds 50s ribosomal subunit and prevents protein synthesis.
• Effective against a number of bacteria, Gm - and positive rods. Also active against many aerobes
• Does not enter CNS and causes alterations in gut flora that can lead to C Dif induced colitis

Question 4

Chloromphenicol

Answer 4

• Binds 50s ribosomal subunit, very effective against many bacteria
• Not used commonly because of neonatal toxicity and aplastic anemia
• May be used against spirochettes if tetracyclins don’t

Question 5

Common Anaerobes

Answer 5

• C Botulinim, Tetani, Perfringes, Dificile
• Bacteroides fragilis
• Actinomyces
• Fusobacteria

Question 6

Clostridium Botulinim

Answer 6

• Spore forming gm + anaerobe. Produces protein toxin that inhibits release of Ach at NMJ causing descending flaccid paralysis. Comes from not properly cooking or canning food. Also can colonize gut of infants and cause a floppy baby flacid paralysis.
• Treatment is often supportive and antitoxin not antibiotics although metronidazole is effective

Question 7

Clostridium Tetani

Answer 7

• Releases a toxin that blocks Cl channels and prevents neuronal inhibition leading to a descending spastic paralysis. Comes from soil and often enters through a wound.
• Penicilin can be used but crucial to provide supportive care and antitoxin. Toxin is problem, not bacteria
• Clinical infection does not confer immunity and patients infected must be immunezed upon disscharge.

Question 8

Clostridium Perfringes

Answer 8

• Can cause food poisoning and gas gangrene. Preformed enterotoxins cause self limiting disease from improperly cooked foods. Lecithinase alpha toxin can cause gas gangrene and large amounts of necrosis, and is a surgical emergency.
• If food poisoning do nothing except supportive care, if gas gangrene carefully clean and debride wound and provide appropriate antibiotics.

Question 9

Clostridium Dificile

Answer 9

• Normal member of gut flora but can grow out of control if patient is treated with antibiotics (clindamycin and quinolones) that kill other anaerobes in gut. Causes colitis. Spores are very easily transmissible and are not removed with alcohol washing, must use soap and water and be very careful.
• Treat with metroniadizole, can also use vancomycin and flaxomicin. Fecal transplants are also very effective.

Question 10

Bacteriodes Fragilis

Answer 10

• Gm negtive anaerobe that is normal component of gut flora but causes infection if it escapes anywhere else. Think infections below diaphragm. Most importantly bacteremia and peritonitis. Can be released by ruptured appendix and trauma. Can cause UTI infections and can infect ulcers.
• Treat with metroniadizole, carbapenems, or beta lactam.

Question 11

Actinomyces

Answer 11

-Can cause head and neck infections as well as brain abcesses.