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
With a hospitalized patient has a serious infection, Dr. Satterfield says her facility’s clinicians are bound to following hospital protocol. On a recent conference call, she contacted Dr. Joseph via Skype and they discussed hospital antibiograms. She notes the antibiograms reveal the most common organisms in that particular hospital and after admitting the patient, one treats to the antibiogram. “(Dr. Joseph) said something amazing to me,” she recalls, “that many doctors don’t realize an antibiogram exists. That is your roadmap for treatment.”
When do you consider taking a wound culture and how?
Dr. Joseph will culture a wound that appears infected but will not culture clinically non-infected wounds. Saying he does not believe in superficial swabs, Dr. Joseph notes deep tissue or surgical cultures are the most reliable. He says one can use “semi-quantitative” swab methods, such as the “Levine technique.”3 As he explains, with this technique, one rolls a swab with pressure over a 1 cm2 area of a debrided and cleansed wound. Dr. Joseph says this allows the capture of deeper wound fluid.
Except for a mild or very superficial wound infection, Dr. Suzuki prefers to take a wound culture using a swab prior to initiating an antibiotic therapy. In his outpatient wound clinic, he debrides the wound first, irrigates it well with sterile saline and then takes a piece of tissue from the wound bed for tissue culture. In an operating room setting, he uses the same method to take deep tissue samples, including a piece of bone or bone marrow if he suspects bone infection.
On a few occasions, Dr. Suzuki says one may not be able to get a good tissue culture or the portal of entry is not obvious. In these cases, he would still use empirical antibiotics and follow the clinical course closely. To that end, Dr. Suzuki checks the wound daily in hospitalized patients or every other day to a few days in the outpatient clinic.
Dr. Satterfield would not consider taking a wound culture. As she notes, the consensus preference of her physicians at her institution is taking a wound biopsy for culture when there is an open portal. However, Dr. Satterfield says this doesn’t seem to be standard practice among podiatrists yet.
“I still hear about people taking a swab culture from the surface of the wound without prepping the wound. That is worthless,” claims Dr. Satterfield.
Dr. Satterfield notes if the wound has purulent drainage, it is all right to take a culture from deep inside the wound, getting some of the purulence after thoroughly cleansing the outer surface of the wound. However, she says in order to obtain the most optimal culture, she recommends cleansing the wound with an agent like Hibiclens (Molnlycke Health Care), debriding away the surface tissue and then sending a deep tissue culture.
When would you consider admitting a patient for wound infection?
Dr. Satterfield says one must admit patients for IV antibiotics, wound biopsy/culture, I&D of a wound, debridement of a wound and to get studies and consults that would otherwise not be efficiently available outside of the hospital.
One should admit patients who have failed outpatient therapy, when they need significant surgical intervention/incision and drainage, when IV antibiotics are necessary or when the patient is metabolically unstable and systemically unwell, according to Dr. Joseph. He says these patients would fall under the IDSA definition of having a “severe” infection.
For Dr. Suzuki, admitting a patient depends on the clinical findings and the overall medical status of the patient. When he encounters the new onset of cellulitis on a lower extremity wound, he draws a line with a surgical marking pen along the erythema demarcation line. Then he would recommend admission for IV antibiotics if the erythema is not receding as it should with oral antibiotics. Dr. Suzuki also recommends admission if a patient complains of high fever or chills as these may be early signs of sepsis.