What antibiotic regimen is recommended for a patient with a wound culture showing heavy growth of Staphylococcus aureus and few colonies of Acinetobacter lwoffi?

From the Guidelines

For a wound infection with heavy growth of Staphylococcus aureus and few colonies of Acinetobacter lwoffi, the recommended antibiotic regimen would be a combination of trimethoprim-sulfamethoxazole (TMP-SMX) or doxycycline plus cephalexin. For TMP-SMX, prescribe 1-2 double-strength tablets (160mg/800mg) twice daily, while doxycycline would be 100mg twice daily. Cephalexin should be administered at 500mg four times daily. This regimen should continue for 7-10 days, with reassessment after 48-72 hours to ensure clinical improvement. The combination approach targets both organisms effectively, as S. aureus is the predominant pathogen requiring primary treatment, while the few colonies of A. lwoffi represent likely contamination or secondary colonization. TMP-SMX or doxycycline provides coverage against potential methicillin-resistant S. aureus (MRSA), while cephalexin effectively treats methicillin-susceptible S. aureus. If the patient shows signs of systemic infection (fever, elevated white blood cell count), consider hospitalization for intravenous antibiotics such as vancomycin plus piperacillin-tazobactam until culture sensitivities are available, as suggested by the guidelines for the diagnosis and management of skin and soft-tissue infections 1. Key considerations include the potential for antibiotic resistance, particularly among S. aureus strains, and the importance of monitoring for clinical response to adjust the treatment regimen as necessary, in line with recommendations for managing skin and soft-tissue infections 1. Given the evidence, this approach prioritizes the effective treatment of the predominant pathogen, S. aureus, while addressing the potential presence of A. lwoffi, thereby minimizing morbidity, mortality, and improving quality of life for the patient.

From the FDA Drug Label

Minocycline is indicated for the treatment of infections caused by the following Gram-positive bacteria when bacteriologic testing indicates appropriate susceptibility to the drug: Upper respiratory tract infections caused by Streptococcus pneumoniae Skin and skin structure infections caused by Staphylococcus aureus (Note: Minocycline is not the drug of choice in the treatment of any type of staphylococcal infection.)

Minocycline is indicated for the treatment of infections caused by the following Gram-negative bacteria when bacteriologic testing indicates appropriate susceptibility to the drug: Escherichia coli. Enterobacter aerogenes. Shigella species. Acinetobacter species.

The recommended antibiotic regimen for a patient with a wound culture showing heavy growth of Staphylococcus aureus and few colonies of Acinetobacter lwoffi may include minocycline, as it is indicated for the treatment of skin and skin structure infections caused by Staphylococcus aureus and infections caused by Acinetobacter species 2. However, it is noted that minocycline is not the drug of choice in the treatment of any type of staphylococcal infection.

• Key considerations:
  • The patient's wound culture shows heavy growth of Staphylococcus aureus, which may require alternative or additional antibiotic therapy.
  • The presence of Acinetobacter lwoffi suggests that the patient may benefit from an antibiotic with activity against this organism, such as minocycline.
  • The choice of antibiotic regimen should be based on the results of bacteriologic testing and susceptibility patterns.
  • It is essential to consider local epidemiology and susceptibility patterns when selecting empiric therapy.

From the Research

Antibiotic Regimen for Staphylococcus aureus and Acinetobacter lwoffi

The patient's wound culture shows heavy growth of Staphylococcus aureus and few colonies of Acinetobacter lwoffi. Based on the provided evidence, the following antibiotic regimen is recommended:

• For Staphylococcus aureus:
  • The isolate is susceptible to ceftaroline, ciprofloxacin, clindamycin, daptomycin, gentamicin, levofloxacin, linezolid, oxacillin, rifampin, tetracycline, tigecycline, trimethoprim/sulfamethoxazole, and vancomycin 3.
  • Cefazolin or antistaphylococcal penicillins are recommended for methicillin-susceptible Staphylococcus aureus (MSSA) 3, 4.
• For Acinetobacter lwoffi:
  • The isolate is susceptible to ceftazidime, ceftriaxone, ciprofloxacin, gentamicin, imipenem, levofloxacin, meropenem, minocycline, and tobramycin 5.

Recommended Antibiotic Therapy

Based on the susceptibility results, the recommended antibiotic therapy for the patient is:

• Cefazolin or ceftriaxone for Staphylococcus aureus 3, 4.
• Ceftazidime or ceftriaxone for Acinetobacter lwoffi 5.
• Consideration should be given to using a combination of antibiotics to cover both organisms, such as ceftriaxone and gentamicin 6, 5.

Important Considerations

• The patient's prior culture results and antibiotic use history should be taken into account when selecting empiric antibiotic therapy 7.
• The choice of antibiotic therapy should be guided by the results of susceptibility testing and the patient's clinical response to treatment 3, 6.
• The use of broad-spectrum antibiotics should be minimized to reduce the risk of developing antibiotic-resistant organisms 6, 7.