Anaerobes

Question 1

What can be added as reducing agents to anaerobic media?

Answer 1

thioglycollate and L-cysteine

Question 2

What most affects the redox potential, aka Eh, of anaerobic media?

Answer 2

pH

Question 3

What media is best for selective isolation of gram-negative anaerobes and what does each component do?

Answer 3

KVLB: Kanamycin inhibits FACULTATIVE gram-negs (not obligate), Vancomycin inhibits gram-positives, and Laked blood enhances pigment production

Question 4

What are some common genera that KVLB would isolate?

Answer 4

Gram neg anaerobes such as Bacteroides, Prevotella, and Fusobacterium

Question 5

What does PEA inhibit?

Answer 5

facultative gram neg bacteria such as Enterobacterialis; It will grow both gram pos aerobes and anaerobes AND gram neg obligate anaerobes

Question 6

WHat is Cycloserine-cefoxitin-fructose agar selective for?

Answer 6

C. difficile

Question 7

What are the end products of anaerobic bacteria grown in PYG (prereduced peptone-yeat extract-glucose) and how are these products used to identify anaerobes?

Answer 7

volatile fatty acids which are analyzed by gas-liquid chromatography, analyzing peaks for acetic, formic, or butyric acids for example, and comparing to standards

Question 8

What are some identifying characteristics of Clostridium perfringens and how does it differ in enzyme production from C. botulinum, C. difficile, and C. tetani?

Answer 8

It is: lecithinase positive, lipase negative, produces a double zone of hemolysis on Blood agar, and has subterminal spores if seen;
C. tetani and C. difficile are both lecithinase and lipase negative (neg-tits is diff!)
C. botulinum is both lecithinase and lipase positive (pos-bot!)

Question 9

If both C. tetani and C. diff are lipase and lecithinase negative, what are some differentiating factors?

Answer 9

C. tetani has ROUND Terminal spores and is INDOLE POSitive

C, diff has SUBterminal spores and is INDOLE NEG

Question 10

which Clostridium is both lecithinase and lipase positive?

Answer 10

C. botulinum

Question 11

Which clostridium is the non-motile (of the major ones)?

Answer 11

C. perfringens

Question 12

compare the infant botulism and the classic foodborne botulism

Answer 12

In infants, it is due to spore ingestion; In adults and children’s cases it is preformed toxin

Question 13

C. botulinum and C. sporogenes both are lipase and motility positive with subterminal spores; what test confirms C. botulinum infection?

Answer 13

toxin neutralization for neurotoxins in serum or feces

Question 14

what does clinical testing for C. diff encompass?

Answer 14

both culture (takes 3 days) and immunoassays for either A toxin or both A and B toxin

Question 15

Why are clinical findings needed to ID C. tetani infection?

Answer 15

Because the culture and gram stain of wound does not usually show evidence of the bacteria

Question 16

The Bacteroides group of obligate gram positive anaerobes grow well in: _____, versus?; Bacteroides ureolyticus differs from most, including B. fragilis, in what way(s)?

Answer 16

20% bile; versus other obligate anaerobic gram positive bacilli such as Prevotella and Porphyromonas
B. ureolyticus is susceptible to Vanc and Kanamycin, where B. fragilis is resistant