CASEONE: ES, a 50-year-old male on a 2-week vacation with his family, presents to the mountain resort's infirmary complaining of 3 days of abdominal cramps and diarrhea. He describes the diarrhea as initially looking clear but has become bloody and more voluminous. He also reports experiencing headache and malaise. Although he did not have a thermometer, he believes he has been running a fever for the last 2 days.

During the workup, the physician learns that ES has a history of angina and congestive heart failure. Prior to this vacation, ES had not experienced any chest pain in 4 weeks. He does routinely require 2 pillows to assist his breathing while sleeping. Over the last 24 hours, ES reports experiencing frequent episodes of chest pain along with shortness of breath on exertion.

The physician documents the following findings on physical examination:

• Vital signs: blood pressure, 170/95 mm Hg; heart rate, 105; respiratory rate, 25; temperature, 38.6ºC; weight, 100 kg
• General: well-developed, obese male in mild distress
• Head, eyes, ears, nose, and throat: dry mucous membranes, mild jugular venous distention
• Coronary: regular rate and rhythm without murmur
• Abdomen: soft, nontender
• Extremities: 1+ lower extremity edema
• A culture of ES' stool revealed organisms of the Salmonella species

If ES had presented with mild or asymptomatic Salmonella diarrhea, the physician would not prescribe antibiotics. In light of the severity of ES'diarrhea in combination with his chest pain and shortness of breath, the clinician decides to treat ES with antibiotics. After confirming that ES does not have any medication allergies, the clinician searches the infirmary's medicine supply for an appropriate antibiotic. In the medication closet, he finds:

10 tablets of azithromycin, 250 mg
25 capsules of penicillin, 250 mg
14 tablets of ciprofloxacin, 500 mg
25 tablets of cefuroxime, 500 mg

Which antibiotic, and at what dose and length of therapy, should the clinician choose to treat ES' diarrhea?

CASE TWO: While on semester break from pharmacy school, ML joins a medical missionary trip to a developing country. Near the end of the trip, ML develops severe diarrhea. Along with more than 5 unformed stools per day, he also has abdominal cramping and nausea. He has a high fever accompanied by shaking chills. When he notices blood in his stool, ML decides his diarrhea is severe enough to warrant care from the trip's physician.

With no means available for culturing stool, the physician must choose an antibiotic to treat ML's diarrhea without knowing the identity of the offending bacteria. The physician explains that 75% of dysentery cases are caused by bacteria, with more than 50% caused by Escherichia coli. He also explains the importance of covering for Shigellae because the presence of bloody diarrhea is suspicious for shigellosis.

When the physician and ML examine the antibiotic supply, they are disappointed to see that there are only a few doses of antibiotics still available. The available medications include:

20 tablets of ciprofloxacin, 500 mg
6 tablets of sulfamethoxazole-trimethoprim, double strength
30 capsules of penicillin VK, 250 mg
25 capsules of cephalexin, 500 mg

The physician decides to use the opportunity to test ML's knowledge of antibiotic spectrums of activity. He asks ML to determine which medication, at what dose, and for how long would be best considering the limited supply.

What antibiotic and regimen should ML select?

Dr. Schlesselman is an assistant clinical professor at the University of Connecticut School of Pharmacy.