1. Staph aureus with cefazolin: SUSCEPTIBLE. This report means that the isolated bacteria is sensitive to the first generation cephalosporin. It means that the organism is most likely MSSA and it is appropriate to treat the infection with cephalexin (Keflex), a first-generation cephalosporin.
2. Staph aureus with cefazolin: RESISTANT. This report indicates MRSA and one should treat it with doxycycline, clindamycin, trimethoprim/sulfamethoxazole or linezolid for oral therapy, or vancomycin, linezolid, daptomycin (Cubicin, Cubist Pharmaceuticals) or tigecycline (Tygacil, Pfizer) for IV therapy, based on the culture and sensitivity report.
3. Coagulase-negative Staphylococcus. This is a common skin flora and rarely a disease-causing agent. This could mean one of two things. You may not have taking a good enough culture sample to isolate the disease-causing bacteria. Alternately, this finding could mean the wound is not infected but is perhaps red and inflamed from other reasons. For example, one may consider an allergic reaction to the wound dressing.
Pertinent Insights On Diagnosing And Treating Infected Wounds
Dr. Satterfield says it may be helpful to go back to the basics and look for rubor, calor and tumor but on a localized basis. If the patient has localized redness, heat and edema, she says you are probably dealing with an infection.
What is your empiric choice of antibiotics in the outpatient setting?
Although Dr. Satterfield says broad spectrum antibiotics are the safe choices, she notes that clinicians have become smarter about what organisms they are going to find. She questions whether it is unsafe to just use a first generation cephalosporin empirically for uncomplicated foot infections when Staph aureus is reportedly the number one organism found in uncomplicated foot infections. When it comes to mild outpatient infections, Dr. Satterfield notes that physicians will be seeing the patient back in a week.
When considering antibiotics, Dr. Joseph questions the location and appearance of the infection. He asks if the patient is predisposed to methicillin-resistant Staph aureus (MRSA) following a previous infection and considers the local rates of MRSA prevalence. If he suspects MRSA, Dr. Joseph prefers doxycycline 100 mg BID. Likewise, for outpatient wound patients, Dr. Suzuki prefers using doxycycline 100 mg BID for seven to 10 days, saying the oral medication covers most MRSA infections with minimal side effects and drug interactions.
Although some clinicians have suggested high-dose trimethoprim/sulfamethoxazole (Bactrim, Roche) or two pills of trimethoprim/sulfamethoxazole DS BID for seven to 10 days, Dr. Suzuki has had better outcomes and much less drug interaction issues with doxycycline. Likewise, Dr. Joseph avoids trimethoprim/sulfamethoxazole because of its adverse event profile. If he does not suspect MRSA but does suspect MSSA or Streptococcus, he would consider cephalexin.
Many of Dr. Suzuki’s patients are on warfarin (Coumadin) for atrial fibrillation and other conditions. He notes that trimethoprim/sulfamethoxazole is contraindicated for those patients on this common anti-coagulation drug. Dr. Suzuki notes levofloxacin (Levaquin, Janssen Pharmaceuticals) can be effective for some MRSA infections but he prefers to reserve levofloxacin for more serious gram-negative infections such as Pseudomonas. He has seen several cases of Achilles tendon ruptures after the patients took ciprofloxacin (Cipro, Bayer) and levofloxacin so Dr. Suzuki suggests reserving the quinolone class of drugs for serious infections only. Dr. Joseph agrees and suggests that one not rely too heavily on the quinolones.
What is your empiric choice of antibiotics for hospitalized patients with infected wounds?
Dr. Suzuki often starts the IV antibiotic therapy with a combination of vancomycin and piperacillin/tazobactam (Zosyn, Pfizer), which he readjusts based on wound culture sensitivity results. He will consult the infectious disease doctors on staff for antibiotic management, especially if the patients are immunocompromised or if they need long-term antibiotics with a peripherally inserted central catheter (PICC) line for bone infection treatment.
For moderate to severe infections as defined by the IDSA guidelines, Dr. Joseph generally practices “de-escalation” therapy. He starts with a combination effective against MRSA and then changes this based on culture results. His usual empiric choice is a combination of ertapenem and vancomycin. Although he formerly used piperacillin/tazobactam in place of ertapenem, Dr. Joseph says one almost never needs the anti-Pseudomonal activity of piperacillin/tazobactam and ertapenem can be a once daily dose. He will also substitute linezolid for vancomycin in appropriate patients.