What are the best oral antibiotics for Staphylococcus aureus (S. aureus) infections in the groin folds, excluding Methicillin-resistant Staphylococcus aureus (MRSA), in a patient with an allergy to Nitrofurantoin (Nitrofurantoin)?

From the Guidelines

For methicillin-sensitive Staphylococcus aureus (MSSA) infections in the groin folds, first-line oral antibiotic treatment would be cephalexin (Keflex) 500 mg four times daily for 7-10 days. This recommendation is based on the most recent and highest quality study available, which is the 2014 update by the Infectious Diseases Society of America 1. Alternative options include dicloxacillin 500 mg four times daily, or clindamycin 300-450 mg three times daily if beta-lactam allergies are present. Trimethoprim-sulfamethoxazole (Bactrim DS) one tablet twice daily is another effective option, particularly for patients with penicillin allergies. The nitrofurantoin allergy is not a concern here as this medication is not typically used for skin infections.

When treating groin fold infections, it's essential to maintain good hygiene by keeping the area clean and dry, using mild soap, and wearing loose-fitting cotton underwear to reduce moisture and friction. Warm compresses may help with comfort and drainage if furuncles are present. These antibiotics are effective because they specifically target the cell wall synthesis of gram-positive bacteria like Staphylococcus aureus, with good tissue penetration in skin infections. If symptoms don't improve within 48-72 hours or worsen at any point, medical reassessment is necessary.

Some key points to consider:

• The choice of antibiotic should be based on the severity of the infection, patient allergies, and local resistance patterns.
• Incision and drainage may be necessary for abscesses or furuncles, in addition to antibiotic therapy.
• Patients with severe or extensive disease, systemic illness, or comorbidities may require hospitalization and intravenous antibiotics.
• Cultures from abscesses and other purulent infections are recommended to guide antibiotic therapy and detect potential resistance patterns 1.

Overall, the goal of treatment is to reduce morbidity, mortality, and improve quality of life by effectively managing the infection and preventing complications.

From the FDA Drug Label

Adults: The usual dose of oral doxycycline is 200 mg on the first day of treatment (administered 100 mg every 12 hours) followed by a maintenance dose of 100 mg/day

• Doxycycline is an option for the treatment of staph aureus infections, including those in the groin folds.
• The recommended dose for adults is 200 mg on the first day, followed by a maintenance dose of 100 mg/day.
• Since there is no mention of MRSA and the patient is allergic to nitrofurantoin, doxycycline can be considered as a treatment option 2.

From the Research

Treatment Options for Staph Aureus Infections

• For methicillin-susceptible S. aureus (MSSA) infections, penicillinase-resistant penicillins (flucloxacillin, dicloxacillin) are the antibiotics of choice 3.
• First generation cephalosporins (cefazolin, cephalothin and cephalexin), clindamycin, lincomycin and erythromycin can also be used for less serious MSSA infections such as skin and soft tissue infections or in patients with penicillin hypersensitivity 3.
• However, cephalosporins are contra-indicated in patients with immediate penicillin hypersensitivity (urticaria, angioedema, bronchospasm or anaphylaxis) 3.

Considerations for Groin Fold Infections

• Skin and soft tissue infections (SSTIs) are among the most common infections worldwide and can range in severity from minor to life-threatening diseases 4.
• Staphylococcus aureus is a common cause of SSTIs, including those in the groin area 4.
• Treatment of SSTIs caused by S. aureus typically involves antibiotics, with the choice of antibiotic depending on the severity of the infection and the presence of methicillin resistance 5, 6.

Alternatives to Nitrofurantoin

• Since the patient is allergic to nitrofurantoin, alternative antibiotics such as clindamycin, lincomycin, or erythromycin may be considered for the treatment of MSSA infections in the groin area 3.
• However, the most appropriate antibiotic should be chosen based on the severity of the infection, the presence of any underlying medical conditions, and the results of antibiotic susceptibility testing 5, 6.