What is the next step in managing a 48-year-old female with post-coital dysuria, low-grade fever, and pyuria, who was initially treated with a 3-day course of cefadroxil (Cefadroxil), but still presents with fever and tachycardia, and has a urine culture growing methicillin-sensitive Staphylococcus aureus?

From the Guidelines

The next step in managing this patient is to switch to intravenous antibiotics with good coverage against methicillin-sensitive Staphylococcus aureus (MSSA), such as cefazolin 1-2g IV every 8 hours or oxacillin 2g IV every 4-6 hours. The patient should be admitted to the hospital for treatment and further evaluation due to the presence of fever and tachycardia, which suggest systemic involvement and possible progression to pyelonephritis or bacteremia. Blood cultures should be obtained before starting antibiotics to rule out bloodstream infection. A renal ultrasound or CT scan should be considered to evaluate for complications such as abscess formation or obstruction. The initial treatment failure with cefadroxil may be due to inadequate dosing, poor penetration into the urinary tract, or the development of resistance. Staphylococcus aureus is an unusual urinary pathogen and its presence suggests either hematogenous seeding of the urinary tract, an anatomical abnormality, or an underlying condition predisposing to infection. After clinical improvement, typically after 48-72 hours of IV therapy, the patient can be transitioned to an appropriate oral antibiotic based on susceptibility testing, such as trimethoprim-sulfamethoxazole or cephalexin, to complete a 10-14 day course 1.

Some key points to consider in the management of this patient include:

• The use of intravenous antibiotics with good coverage against MSSA, such as cefazolin or oxacillin, is recommended for the treatment of complicated skin and soft tissue infections caused by MSSA 1.
• The addition of gentamicin to the treatment regimen may not be necessary, as it has not been shown to provide a significant clinical benefit and may increase the risk of renal toxicity 1.
• The patient should be closely monitored for signs of clinical improvement, such as resolution of fever and tachycardia, and for potential complications, such as abscess formation or obstruction.
• The use of oral antibiotics, such as trimethoprim-sulfamethoxazole or cephalexin, may be considered for the completion of the treatment course after clinical improvement has been observed 1.

It is also important to note that the patient's condition and response to treatment should be closely monitored, and adjustments to the treatment plan should be made as necessary to ensure the best possible outcome. The patient's renal function should also be monitored closely while on gentamicin therapy, if it is decided to add it to the regimen 1.

In terms of specific antibiotic regimens, the following options may be considered:

• Cefazolin 1-2g IV every 8 hours or oxacillin 2g IV every 4-6 hours for the treatment of MSSA infections 1.
• Trimethoprim-sulfamethoxazole or cephalexin for the completion of the treatment course after clinical improvement has been observed 1.

Overall, the management of this patient requires careful consideration of the potential causes of the infection, the most effective treatment options, and the potential risks and benefits of different antibiotic regimens. The patient's condition and response to treatment should be closely monitored, and adjustments to the treatment plan should be made as necessary to ensure the best possible outcome 1.

From the FDA Drug Label

Oxacillin is indicated in the treatment of infections caused by penicillinase producing staphylococci which have demonstrated susceptibility to the drug. The next step is to consider using oxacillin to treat the methicillin-sensitive Staphylococcus aureus infection, as it is indicated for the treatment of infections caused by susceptible staphylococci.

• The patient's urine culture shows methicillin-sensitive Staphylococcus aureus, which suggests that oxacillin may be effective.
• However, it is essential to note that oxacillin should not be used in infections caused by organisms susceptible to penicillin G. Since the Staphylococcus aureus is methicillin-sensitive, oxacillin can be considered as a treatment option 2.

From the Research

Patient Management

The patient is a 48-year-old female with post-coital dysuria, low-grade fever, and pyuria, who was initially treated with a 3-day course of cefadroxil. Despite this treatment, she still presents with fever and tachycardia, and her urine culture grows methicillin-sensitive Staphylococcus aureus (MSSA).

Treatment Considerations

• The initial treatment with cefadroxil was likely ineffective against the MSSA infection, as evidenced by the persistent symptoms and positive urine culture 3.
• MSSA infections are typically treated with anti-staphylococcal beta-lactams, such as cefazolin, nafcillin, or oxacillin 4, 5.
• Cefazolin has been shown to be effective in treating MSSA infections complicated by bacteremia, with a lower risk of mortality and similar odds of recurrent infections compared to nafcillin or oxacillin 5.
• Once-daily treatment options for MSSA bacteremia, such as ceftriaxone or daptomycin, may not be sufficient, and traditional second-line agents may be preferred 6.

Next Steps

• Consider switching to a more effective antibiotic, such as cefazolin, to treat the MSSA infection 5.
• Ensure the patient receives adequate treatment duration, as shorter courses may not be sufficient to clear the infection 3.
• Monitor the patient's symptoms and urine culture results to assess the effectiveness of the new treatment regimen 3.