According to a new study(wwwnc.cdc.gov) from researchers at Boston Medical Center and Boston University School of Medicine, obesity may be an independent risk factor for Clostridium difficile infection (CDI). The study's findings were published online in Emerging Infectious Diseases.
Inflammatory bowel disease (IBD) previously has been identified as an independent risk factor for C. difficile colonization and disease, as has use of antibacterial drugs -- a relationship that appears to be modulated by a dysbiosis of intestinal microbiota. Recently, studies have shown that obesity also may be associated with decreased diversity and changes in composition of the intestinal microbiome, which could translate into a similar risk profile.
The current retrospective analysis looked at 132 cases gleaned from infection control database records, microbiology results and medical records of adult patients at a medical center who had laboratory-confirmed CDI from November 2011 to April 2012. By comparing a relatively low-risk group of patients with CDI to those with more traditional risk factors for the disease, such as exposure to health care facilities, antibacterial drug use and IBD, the researchers were able to identify an association between obesity and CDI.
Prevalence and Epidemiology
According to the CDC, CDIs cause about 14,000 deaths each year, and the annual number of hospital discharge diagnoses of CDI has doubled during the past decade, rising from about 139,000 to 336,600.
In addition, the epidemiology of CDI has shifted during that time, with an increasing number of cases that originate in the community being seen in traditionally low-risk populations. This shift has sparked concerns that unidentified risk factors may be increasing the likelihood of contracting CDI in this population subset.
The study's authors note that before 2010, guidelines developed by the Society for Healthcare Epidemiology of America and the Infectious Diseases Society of America (SHEA-IDSA) defined CDIs as "having community onset (CO) or inpatient health care facility onset (HO)." In recognition of the changing epidemiology of CDI, that definition was expanded in a 2010 guideline update to include an additional category of disease: community-onset health care facility-associated (CO-HCFA). This category refers to CDI cases that occur among patients in the community who had exposure to health care facilities during the previous four weeks.
For the purposes of this study, hemodialysis centers, day surgery centers, chemotherapy suites and long-term care facilities, in addition to traditional inpatient facilities, were grouped under the "health care facility" designation.
The chief goal of the study, according to researchers, was to pinpoint potential demographic and risk factor differences between patients who develop CO CDIs and those with HO or CO-HCFA infections. "In particular," they said, "we examine whether obesity is overrepresented in patients with community-onset infections who did not have exposure to health care facilities, antibacterial drugs or the diagnosis of IBD."
In addition, the researchers noted, identifying the specific health care delivery sites represented among patients with CO-HCFA infections could facilitate targeted staff training and education, as well as improved allocation of infection control resources.
Using the former SHEA-IDSA classification, the 132 patients shown to have lab-confirmed CDI were categorized as having either community or nosocomial onset disease. Patients then were reclassified according to the new SHEA-IDSA guidelines as having CO, CO-HCFA or HO disease.
Initially, 91 cases were counted as CO disease, and 41 were determined to be HO disease. By using the definitions described in 2010, 35.2 percent of the CO cases were found to be HCFA-CO. Of these, 62.5 percent had a prior hospital admission as a risk factor, and 28.1 percent were from a long-term care facility. Other risk factors (accounting for those with more than one risk factor) included recent surgery (12.5 percent), hemodialysis (9.4 percent) and outpatient chemotherapy (3.4 percent).
Additional Study Findings
Univariate analysis testing for differences across the three groups revealed lower percentages of patients with IBD in the HO and CO-HCFA categories compared with the CO group. A higher percentage of patients in the CO category were noted to be obese; in fact, the percentage of patients in the CO group who were obese (34 percent) was statistically higher than the state average (23 percent). HO cases were more likely to have had previous exposure to antibacterial drugs compared with the CO and CO-HCFA groups.
"Patients with community onset infections had higher body mass indices than the general population, and those with community onset after exposure to a health care facility had higher rates of IBD and lower prior antibacterial drug exposure than patients who had CDI onset in a health care facility," the researchers wrote. "Obesity may be associated with CDI, independent of antibacterial drug or health care exposures."