Anaerobic Infections Austin

Question 1

Body’s normal flora is predominantly anaerobic and nearly all mucosal surfaces are heavily colonized by obligate anaerobes

Answer 1

1. In the colon, 90% of the fecal matter is bacteria and obligate anaerobes outnumber facultative anaerobes by >1000:1.
2. Obligate and facultative anaerobes outnumber other bacteria in the mouth by >10:1; obligate anaerobes are able to survive in the mouth in the presence of oxygen because oral/viridans streptococci lower the red-ox potential.

Question 2

Synergistic mechanisms enhance survival and virulence

Answer 2

○ Bacteroides spp. That require vitamin K get it form nonpathogenic streptococci or other anaerobes.
○ B. asaccharolyticus causes severe spreading lesions supplied with succinate from klebsiella and other helper bacteria
Facultative anaerobes such as E. coli provide a more favorabloe env. For anerobes by removing oxygen and adding reducing substances as the infection matures; anaerobes return the favor by producing leukotoxins and depleting opsonins and complement.

Question 3

Basic information for culturing for anaerobes

Answer 3

1. Improved laboratory methods have significantly increased isolation rates of anaerobes in recent years; newer commercial methods have become available for identifying anaerobes and for measuring antibiotic susceptibility (MIC).
   2. However, these specialized methods are expensive and time-consuming plus multiple isolates must be processed; therefore, cost is higher and turnaround time is longer than for routine aerobic cultures.
2. Specimens are cultured on special media and incubated in evacuation replacement anaerobic jars or the GasPakTM system or anaerobic glovebox chambers.

Question 4

Clostridia disease associations

Answer 4

○ C. perfringens, toxin type A-E cause enteritis in canine, porcine, possible in equine and bovine
○ C. difficile: psudomembranous colitis (abx associated). Single molecule of O2 will kill it. Need abx misuse to occur
○ C. spiroforme: diarrhea in weaned rabbits
○ F. necrophorum also causes foot rot or pododermatitis
Histotoxic clostridia or gas gangrene group

Question 5

Clostridium perfringens

Answer 5

□ Most common soil bacteria, most common lab contaminant, normal in mammals
□ Alpha toxin is important Virulence factor
® Phospholipase C
Gast production interferes with venous return

Question 6

Clostridium chauvoei

Answer 6

□ Lower intestine and tissue of animals
□ BLACKLEG
Results from activation of latent spores deposited in muscle after being transported in blood from liver or intestine.

Question 7

Clostridium septicum

Answer 7

□ Malignant edema
® More edema muscles pit on pressure and are gelatinous, moist, red with little gas
® Braxy: frozen feed damages abomasum
Chickens: gangrenous dermatitis of the head

Question 8

Clostridium sordelli

Answer 8

Sudden death syndrome

Question 9

Clostridium novyi

Answer 9

□ 3 types based on 5 toxins produced
® Type A produces: alpha, gamma, delta, epsilon
® Type B produces: alpha, beta
® Type C is nontoxigenic
® Alpha increases capillary permeability and necrosis
The major virulence factor
□ Gas gangrene
□ Big Head
Black disease: infectious necrotic hepatitis

Question 10

Clostridium Haemolyticum

Answer 10

Bacillary hemoglobinuria or redwater disease

Question 11

Anaerobic genus morphologies: Bacteroides

Answer 11

GN; very pleomorphic and may be beaded, coccoid or slender; often stain poorly and are difficult to see sometimes bipolar staining

Question 12

Anaerobic genus morphologies: Clostridium

Answer 12

GP rods; large, chains, spores well the sporangium (mother cell) greatly

Question 13

Anaerobic genus morphologies: Fusobacterium

Answer 13

GN rods; thin, pale, with tapered or pointed ends and a cigar or needle shape

Question 14

Anaerobic genus morphologies: Acitomyces

Answer 14

GP rods (or gram variable); small, thin; may form branched filaments or tangled mats; may be beaded or poorly visible; may form sulfur granules

Question 15

Anaerobic genus morphologies: Peptococcus and peptostreptococcus

Answer 15

GP cocci; SMALL singly, pairs or clusters in pairs and chains. Smaller but cannot be distinguished from aerobic cocci.

Question 16

Successful treatment requires elimination of conditions favorable for growth of anaerobes and prevention of spread into healthy tissues

Answer 16

• Antibiotic treatment includes:
• Penicillins, chloramphenicol, clindamycin, and metronidazole are most efficacious
• Aminoglycosides: gentamycin, amakacin, etc are NOT EFFICACIOUS
• Some cepalosporins are efficacious against both GN enterics and anaerobes
• Tetracycline, suflonamides, and trimethoprim-sulfonamides are not useful for anaerobes

Question 17

Anaerobic organisms

Answer 17

1. GP spore forming rods: Clostridium
   
   2. GP non-sporeforming rods: Actinomyces, Propionbacterium, and Eubacterium
   3. GN rods: Bacteroides and Fusobacterium
2. GP cocci: Peptococcus and Peptostreptococcus

Question 18

Bacterins for Clostridia

Answer 18

Whole cell culture bacterins and toxoids

Question 19

Clostridia purfinges both histotoxic and endotoxic

Answer 19

○ Septicum and what it does (maybe)