Obesity & Heart Failure Increase Odds of Treatment Failure in SSTI Patients

Outpatients with uncomplicated skin and soft tissue infections (SSTIs) who have heart failure and obesity are at increased risk of failing oral antibiotic therapy, a new study suggests.

Researchers from Veterans Affairs Western New York Healthcare System published the results of their study online in Antimicrobial Agents and Chemotherapy.

“The incidence of skin and soft tissue infections in outpatients in the United States has increased from 8.6 million in 1997 to 14.2 million in 2005,” the authors write. “Hospitalization rates due to poorly managed or untreated skin infections have also continued to rise.”

Clinicians typically treat patients with SSTIs with oral antibiotics in the outpatient setting. The overall failure rate of oral antibiotic treatment is reported to range from 10% to 21%, and one study estimated that patients who fail therapy require additional medical interventions costing an estimated $1,934.

However, knowledge of risk factors for oral antibiotic failure for SSTIs in the outpatient setting is lacking.

In an interview with Contagion^®, Kari A. Mergenhagen, PharmD, BCPS AQ-ID, Veterans Affairs Western New York Healthcare System, Buffalo, New York, the study’s senior author, explained how the stewardship team had identified large numbers of patients admitted for SSTIs who had failed previous oral antibiotic therapy.

The researcher conducted a study to investigate risk factors for failure of antibiotics in the outpatient setting. “Our goal was to identify these patients to prevent morbidity and effectively treat these patients at high risk for failure,” she said.

Using the Veterans Affairs Western New York Healthcare System electronic medical record, the researchers reviewed a total of 1,060 patient visits. They included 293 patients in the final analysis, 24% of whom failed antibiotic therapy within 30 days.

Among these patients, 182 (62%) received treatment for cellulitis, 67 (23%) received treatment for abscesses, and 44 (15%) received treatment for mixed cellulitis and abscesses. Sixteen percent of the patients had a body mass index (BMI) greater than 40 kg/m².

According to Dr Mergenhagen, patients with obesity and heart failure were at greater risk for failure of oral antibiotics for SSTIs.

Patients who failed oral antibiotic therapy had a greater mean BMI than those who experienced successful treatment (34.2 kg/m² vs31.32 kg/m²; P = 0.0098); they also had an increased prevalence of heart failure (15.9% vs 7.1%; P = 0.027).

Each 10-kg/m2 unit increase in BMI was associated with a 1.62-fold odds of antibiotic failure. In addition, heart failure increased the risk by 2.6-fold, the authors say.

“Further studies are needed to discover possible solutions to avoid subsequent hospital admissions,” stressed Dr Mergenhagen. Some possible solutions might include increased doses of oral antibiotics, use of intravenous antibiotic therapy, or closer follow up with health care professionals, she added.

Dr Mergenhagen and colleagues are now completing the inpatient counterpart to this outpatient study, in order to identify factors for failure in both the inpatient and outpatient settings.

“With an expanded inpatient population, we hope to identify solutions to combat high failure rates in this population,” she concluded.

Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals, and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.