Processing of pus & wound swabs

Question 1

Define these terms:

a) Facultative anaerobe
b) Obligate anaerobe
c) Obligate aerobe

Answer 1

a) FAna: Can grow at aer & anarobic cond.
b) OAna: Only grow at anarobic cond.
c) OAer: Only grow at aerobic cond.

Question 2

List 4-6 clinical factors which might cause you to consider the presence of anaerobes in a swab specimen?

Answer 2

• Closed lesions (wound from ‘deep’ cut)
• Deep lesions or abscess (pus)
• Lesions adjacent to mucous membranes
• Poor circulation
• Gut wounds
• Diabetes

Question 3

If a SAB plate is included for the culture of a specimen, why is it the last agar plate to be inoculated?

Answer 3

Bc the SAB plate contains high level of chloramphenicol = will kill microbes on specimen. Done last to ensure other plates have sufficient microbes grown

Question 4

What is the purpose of the MTZ disc*? What does MTZ stand for?

Answer 4

Distnguish anaerobes growing on BA bc they’re S

MTZ: metronidazole

Question 5

Which organism is commonly associated with dog and cat bites? (full genus + species)

Answer 5

Pasteurella multocida (GNB)

Question 6

What additional selective culture media may be set up for wounds associated with a water origin? What genera are these designed to culture?

Answer 6

a) TCBS: Thiosulphate, Citrate, Bile, Sucrose sugar => Vibrio sp.
b) BAMP: BA w/ Amp => Aeromonas hydrophilia

Question 7

Why is pus from a wound usually a better specimen than a wound swab?

Answer 7

bc contains material deep within wound = more accurate representation of bacteria causing infection & less likely to be contaminated w/ NF

Question 8

What type of WBC is associated with a bacterial infection? What is the correct name when in the blood vs when in tissue?

Answer 8

PMN (Polymorphonuclear leukocytes) in tissue (out of blood)

Neutrophil in blood

Question 9

Which genera produces large oval purple staining cells in a Gram smear?

Answer 9

Yeast (Candida sp)

Question 10

Which genera produces large cigar shaped cells in a Gram smear? And it’s a yeast

Answer 10

Sporotrhix schenkii

Question 11

Name two genera that appear as Gram positive branching rods? How could you attempt to determine which one will be isolated (before culture has been completed)? Name the test/method used and what results each genera would give?

Answer 11

1. Actinomyces => non-acid fast
2. Norcardia => Acid fast
   * Acid fast: resistant to decolourising w/ acids

Question 12

Is CNA selective, differential or both? How does it work? What grows and what doesn’t?

Answer 12

CNA is a selective media: BA + colistin nalidixic acid
Inhibits: GNeg
Allows: GPC +++, GPB, (Yeast+++)

Question 13

Name a Gram positive organism (genus + species) that can appear as a banana shaped rod?

Answer 13

Erysipelothrix rhusiopathiae (GPC banana -shaped rod)

Question 14

According to the CDS method, what agar and what atmospheric conditions should be used for testing Pasteurella sp.? (look in the charts in the lab manual)

Answer 14

Blood sensitised agarin 5% CO2

Question 15

Is LBAG selective, differential or both? How does it work? What grows and what doesn’t?

Answer 15

LBAG (lysed BA w/ Gent) is a selective media bc gent inhibits facultative GNB.
Allows growth of GPC obligate AnO2

Question 16

What’s the controls for AnO2 conditions? (for control plate)

Answer 16

AnO2 = Clostridium sp.
O2 = Pseudomonas sp.

Question 17

What are Diphtheroids?

Answer 17

miscellaneous GNB (rods)