18. A population of Pseudomonas aeruginosa is exposed to successive, short rounds of ampicillin and chloramphenicol. What will happen to the population?
Answer: A
The population will become resistant to chloramphenicol.
Repeated exposure to chloramphenicol can lead to the development of resistance in the Pseudomonas aeruginosa population, as the bacteria adapt to survive in the presence of this antibiotic.
A) The population will become resistant to chloramphenicol.
This option is correct because the repeated exposure to chloramphenicol allows the bacteria to undergo genetic mutations or acquire resistance genes, leading to a population that can withstand the effects of this antibiotic.
B) The population will die.
This option is incorrect because while antibiotic exposure can reduce a population, the specific scenario of successive, short rounds of ampicillin and chloramphenicol suggests that some bacteria may survive and adapt rather than die off entirely.
C) The population will become resistant to ampicillin and chloramphenicol.
This option is misleading because the question specifies that the focus is on chloramphenicol, and while some level of resistance to ampicillin could occur, it is not guaranteed without specific pressure from that antibiotic.
D) The population will become resistant to ampicillin.
This option is also incorrect as it implies a direct outcome of resistance to ampicillin without evidence from the scenario. The focus on chloramphenicol suggests that resistance will develop primarily to that antibiotic.
Conclusion
In summary, the correct answer is A, as the population will develop resistance specifically to chloramphenicol due to the repeated exposure to it. The other options fail because they either misinterpret the focus of the question or suggest outcomes that are less likely given the context of successive antibiotic exposure.