The nurse should teach a patient to observe which side effects when taking ampicillin.

A. Obtaining all cultures before the antibiotic is administered: While obtaining cultures is important for identifying the specific pathogen causing the infection and guiding targeted antibiotic therapy, waiting for culture results can take time. During this time, the infection can progress. Therefore, it's generally recommended to initiate broad-spectrum antibiotics first and then adjust the treatment based on culture results.

B. Delaying administration of the antibiotic until the culture results are available: Delaying antibiotics until culture results are available can be risky, as it allows the infection to progress, potentially leading to sepsis or other severe complications.

C. Administering antipyretics as soon as possible: Administering antipyretics like acetaminophen or ibuprofen can help reduce fever and make the patient more comfortable. However, the primary intervention for a suspected infection is antibiotic therapy, as it targets the underlying cause of the fever.

D. Administering the antibiotic immediately: When dealing with a patient with a fever of unknown origin and a suspected infection, the priority is to start appropriate antibiotic therapy promptly. Delaying antibiotic administration can allow the infection to worsen, leading to serious complications.

A. "Cephalosporins are assigned to generations based on their relative costs to administer."
This statement is incorrect. The classification of cephalosporins into generations is based on their antimicrobial spectrum and activity against specific bacteria, not their cost.

B. "Later generations of cephalosporins have lower resistance to destruction by beta-lactamases."
This statement is not accurate. In fact, later generations of cephalosporins have increased resistance to destruction by beta-lactamases, which are enzymes produced by bacteria that can break down certain antibiotics.

C. "Cephalosporins have increased activity against gram-negative bacteria with each new generation."
This statement is correct. Cephalosporins are grouped into generations (first to fifth) based on their antibacterial spectrum. As the generations progress, there is an increase in activity against gram-negative bacteria, among other improvements in their spectrum.

D. "First-generation cephalosporins have better penetration of the cerebrospinal fluid."
This statement is generally true. First-generation cephalosporins have better penetration into the cerebrospinal fluid, making them useful for treating certain central nervous system infections.