Jawetz Quizzes Questions & Answers

Jawetz Quizzes Questions & Answers A 23-year-old woman has 10 Escherichia coli inoculated into her bladder while having sex. This organism has a generation time of 20 minutes. After a lag of 20 minutes, the E coli enter the logarithmic phase of growth. After 3 hours of logarithmic growth, the total number of cells is (A) 2560 (B) 5012 (C) 90 (D) 1028 (E) 1,000,000 A A 73-year-old woman is admitted to the hospital for intravenous treatment of an abscess caused by Staphylococcus aureus. Subse- quent to her treatment and discharge from the hospital, it is neces- sary to disinfect the hospital room. One thousand of the S aureus cells are exposed to a disinfectant. After 10 minutes, 90% of the cells are killed. How many cells remain viable after 20 minutes? (A) 500 (B) 100 (C) 10 (D) 1 (E) 0 C The action of which of the following agents or processes on non-spore forming bacteria can be reversed? (A) A disinfectant (B) A bactericidal agent (C) A bacteriostatic agent (D) Autoclaving at 121°C for 15 minutes (E) Dry heat at 160-170°C for 1 hour C The growth rate of bacteria during the exponential phase of growth is (A) Zero (B) Increasing (C) Constant (D) Decreasing (E) Negative C A physician obtains a sputum specimen from a patient suffer- ing from tuberculosis. This sputum sample contains one viable Mycobacterium tuberculosis, an organism with a slow doubling time in vitro of 48 hours, which corresponds to a growth rate constant in vitro of (κ) of 0.04 h-1. Estimating that the bio- mass of this single mycobacterial organism is 2.3 × 10−13 g and assuming that this organism is immediately going to enter log phase growth, how many hours will it take to produce 10−6 g of biomass? (A) 4hours (B) 40 hours (C) 400 hours (D) 4000hours (E) 40,000 hours C A specimen of pasteurized goat's milk is cultured for the pres- ence of Brucella melitensis, an organism known to infect ani- mals on an adjacent farm. The milk is declared safe to consume; however, some of those who consume it develop brucellosis. Which one of the following would best explain the disparity between the culture results and the patients' illnesses? (A) Bacteria in the milk were viable but not cultivatable (B) Incomplete pasteurization of the milk (C) The organisms in the milk were in the lag phase when tested (D) The milk had a high level of a bactericidal antibiotic in it when tested (E) There was posttest contamination of the milk A Working as a medical missionary in rural India, you spray the umbilicus of a newly born infant with a solution containing the chemical structure in the associated figure to prevent a tetanus infection. Which class of chemical agent does this structure belong? + R1 R3 N X- R2 R4 (A) Alcoholclass (B) Aldehyde class (C) Bisphenol class (D) Peroxygen class (E) Quaternary ammonium class E Your superior requests that you sterilize some surgical instru- ments. Which one of the following agents would you use? (A) Benzoicacid(2%) (B) Isopropyl alcohol (2%) (C) Glutaraldehyde (2%) (D) Hydrogen peroxide (2%) (E) Quaternary ammonium compound (2%) C