A certain disinfectant has a 6-log killing power against E.coli. Your initial concentration of bacteria is 6.0x10^9 cfu/mL. What concentration of E.coli will you end up with after applying the disinfectant above?
A) 1.0 x 10^9 cfu/mL
B) 6.0 x 10^3 cfu/mL
C) 6.0 x 10^15 cfu/mL
D) 1.0 x 10^3 cfu/mL
E) 3.6 x 10^8 cfu/mL
2. What is the mechanism of action of tetracyclines:
A) Inhibition of DNA transcription
B) Prevent a peptide bond formation in the growing polypeptide chain
C) Inhibit the synthesis of DNA precursors
D) Inhibition of DNA replication
E) Block the attachment of the amino acid-carrying tRNA to the 30S subunit of the ribosome
3. Biguanides are:
A) Sporicidal
B) Non-sporicidal
4. The concentration of your overnight E.coli culture happens to be 4.5x10^7 cfu/mL. You were asked to achieve 300 colonies with a pour-plate method. At some point in your dilution schedule you will have to perform the following dilution:
A) 3mL of culture and 4.5mL of buffer
B) 3mL of culture and 1 mL of buffer
C) 4.5mL of culture and 3 mL of buffer
D) 3mL of culture and 1.5mL of buffer
E) none of the above
5. A bacterial sample was serially diluted according to the following dilution schedule: 1ml culture + 5ml diluent, 0.7ml of the last dilution + 6.3ml of diluent, 1.5 ml of that dilution + 4.5ml diluent. What is the dilution factor?
A) 300
B) 100
C) 240
D) 150
E) 200
6. Which type of antibiotic is better at promoting resistance of bacteria:
A) Narrow-spectrum
B) Natural
C) Synthetic
D) Broad-spectrum
E) Semisynthetic
7. What is the mechanism of action of macrolides:
A) Inhibition of DNA transcription
B) Prevention of peptide bond formation in the growing polypeptide chain
C) Inhibition of synthesis of DNA precursors
D) Inhibition of DNA replication
E) Block the attachment of the amino acid-carrying tRNA to the 30S subunit of the ribosome
8. The process/modification of the antibiotic that generally improves its spectrum of activity, effectiveness, and reduces host toxicity is known as:
A) Semisynthesis
B) Isomerization
C) Potentiation
D) Purification
E) Neutralization
9. Is Hydrogen peroxide (H2O2) sporicidal?
A) Yes, at visually any concentration
B) Not sporicidal at any concentration
C) Depends on the concentration of peroxide. Sporicidal at 10~30% and higher
10. Which of the antimicrobials below uses the highest concentration of the active ingredient in its formulation:
A) Disinfectant
B) Preservation
C) Antiseptic
D) Antibiotic
E) None of the above