A patient comes to see you complaining of a spider bite. He shows you a sore on his wrist—the area around it is red and swollen, and the lesion is leaking pus. The patient tells you he found a spider in his car, which is why he thinks this is a bite. He also tells you that he has been taking penicillin tablets that his wife had left over after being prescribed the drug a few months previously for pneumonia. Even though he has taken the tablets for four days, the lesion is not healing and that he is really feeling terrible, with pain, fever, and chills. You suspect that your patient has a wound infection, so you sample the pus and send it to the lab for analysis.
-Further tests indicate that your patient has a methicillin-resistant Staphylococcus aureus (MRSA) infection. You explain to the patient that these bacteria are not impacted by penicillin or the related drug methicillin. This resistance is thought to have arisen originally by a random change in the cell's chromosome through a process called
A) spontaneous mutation.
B) antigenic variation.
C) quorum sensing.
D) vertical gene transfer.
E) indirect selection.

Question

A patient comes to see you complaining of a spider bite. He shows you a sore on his wrist—the area around it is red and swollen, and the lesion is leaking pus. The patient tells you he found a spider in his car, which is why he thinks this is a bite. He also tells you that he has been taking penicillin tablets that his wife had left over after being prescribed the drug a few months previously for pneumonia. Even though he has taken the tablets for four days, the lesion is not healing and that he is really feeling terrible, with pain, fever, and chills. You suspect that your patient has a wound infection, so you sample the pus and send it to the lab for analysis.
-Further tests indicate that your patient has a methicillin-resistant Staphylococcus aureus (MRSA) infection. You explain to the patient that these bacteria are not impacted by penicillin or the related drug methicillin. This resistance is thought to have arisen originally by a random change in the cell's chromosome through a process called 
A) spontaneous mutation.
B) antigenic variation.
C) quorum sensing.
D) vertical gene transfer.
E) indirect selection.

Quizplus · Accepted Answer

Methicillin-resistant Staphylococcus aureus (MRSA) infections are caused by strains of bacteria that have developed resistance to methicillin and other beta-lactam antibiotics such as penicillin. This resistance is primarily due to the acquisition of the mecA gene, which encodes for a modified penicillin-binding protein that is not affected by these antibiotics. The mecA gene is believed to have originated in a different species of bacteria and was transferred to S. aureus through horizontal gene transfer. While vertical gene transfer (inheritance from parent to offspring) can also contribute to the spread of antibiotic resistance, in the case of MRSA, it is primarily due to spontaneous mutation and horizontal gene transfer.

A Patient Comes to See You Complaining of a Spider