What are the effective antibiotic treatments for a patient with heavy growth of Staphylococcus aureus, few colonies of normal skin flora, moderate growth of Beta hemolytic Streptococcus group C, and heavy growth of Escherichia coli (E. coli)?

From the Guidelines

The most appropriate treatment for the patient with a heavy growth of Staphylococcus aureus and E. coli is ciprofloxacin or levofloxacin, as both are effective against the S. aureus and E. coli isolates, according to the most recent guidelines from the Infectious Diseases Society of America 1. The S. aureus is oxacillin-susceptible (MSSA), making it sensitive to many beta-lactam antibiotics, while the E. coli shows resistance to ampicillin and cefazolin but remains susceptible to third-generation cephalosporins and fluoroquinolones. Some key points to consider in the treatment of skin and soft tissue infections include:

• Cultures of blood or cutaneous aspirates, biopsies, or swabs are not routinely recommended, but may be considered in certain cases, such as in patients with malignancy on chemotherapy, neutropenia, severe cell-mediated immunodeficiency, immersion injuries, and animal bites 1.
• Typical cases of cellulitis without systemic signs of infection should receive an antimicrobial agent that is active against streptococci, while more severe cases may require broader coverage, including against MRSA 1.
• The recommended duration of antimicrobial therapy is 5 days, but treatment should be extended if the infection has not improved within this time period 1.
• Elevation of the affected area and treatment of predisposing factors, such as edema or underlying cutaneous disorders, are also recommended 1. Alternatively, trimethoprim-sulfamethoxazole could be used as both organisms are susceptible. For more severe infections, piperacillin-tazobactam or a carbapenem (imipenem or meropenem) would provide excellent coverage. The choice of oral versus intravenous therapy should be based on infection severity, with fluoroquinolones offering good bioavailability for outpatient management when appropriate. It's also important to note that the E. coli is resistant to tetracyclines, so these should be avoided despite the S. aureus being susceptible, as stated in the guidelines for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children 1. Overall, the treatment should be individualized based on the patient's clinical response and the severity of the infection, with consideration of the most recent guidelines and evidence-based recommendations 1.

From the FDA Drug Label

Meropenem for injection is indicated for the treatment of complicated skin and skin structure infections (cSSSI) due to Staphylococcus aureus(methicillin-susceptible isolates only), Streptococcus pyogenes, Streptococcus agalactiae, viridans group streptococci, Enterococcus faecalis(vancomycin-susceptible isolates only), Pseudomonas aeruginosa, Escherichia coli, Proteus mirabilis,Bacteroides fragilis,and Peptostreptococcusspecies. The meropenem is effective against Staphylococcus aureus and Escherichia coli.

• The MIC for Staphylococcus aureus is <=1 and is considered S (susceptible).
• The MIC for Escherichia coli is <=1 and is considered S (susceptible) 2. Key points:
• Meropenem is indicated for the treatment of complicated skin and skin structure infections due to Staphylococcus aureus and Escherichia coli.
• Meropenem has a MIC of <=1 for Staphylococcus aureus and Escherichia coli, indicating susceptibility.

From the Research

Staphylococcus Aureus Treatment Options

• More than 90% of S. aureus are resistant to penicillin in the United States, thus routine testing is not always indicated for penicillins 3, 4, 5, 6, 7.
• Oxacillin (cefoxitin)-susceptible staphylococci can be considered susceptible to various antibiotics, including amoxicillin-clavulanate, ampicillin-sulbactam, and cefazolin.
• Ceftaroline is a fifth-generation cephalosporin with broad-spectrum activity against Gram-positive pathogens, including S. aureus and MRSA 3, 4, 5, 7.
• Rifampin should not be used alone for antimicrobial therapy.

Antibiotic Susceptibility

• Organisms that are susceptible to tetracycline are also considered susceptible to doxycycline and minocycline.
• Results of ampicillin testing can be used to predict results for amoxicillin.
• Cefazolin results predict results for the oral agents cefaclor, cefdinir, cefpodoxime, cefprozil, cefuroxime, cephalexin, and loracarbef.

Specific Antibiotic Options

• Ceftaroline has been shown to be effective against S. aureus, including MRSA, in several studies 3, 4, 5, 7.
• Ceftaroline is also effective against other Gram-positive pathogens, including Streptococcus pneumoniae and Streptococcus pyogenes 3, 4, 5.
• Other antibiotics, such as vancomycin, daptomycin, and linezolid, may also be effective against S. aureus, but their use may be limited by resistance or other factors 6.