Defining the problem: C. diff epidemic puts new emphasis on surveillance

NJ hospitals find more ICPs, less C. diff

As an epidemic strain of Clostridium difficile continues to emerge in many U.S. hospitals, a Centers for Disease Control and Prevention working group has issued clinical definitions and is urging ICPs to increase surveillance for the pathogen.

The epidemiology of C. diff-associated disease (CDAD) is changing, with the accumulating evidence pointing to both an increased incidence and severity of infections. "However, the understanding of the magnitude of and reasons for this change is currently hampered by the lack of standardized surveillance methods," reports the Ad Hoc C. diff Surveillance Working Group, which includes CDC officials and infection control advisors. The group recently issued C. diff definitions to help ICPs identify the scope of the problem locally and determine the best strategies to prevent infections.1

Recent increases in CDAD incidence and severity have highlighted the need for standardized reporting definitions and surveillance methods. CDAD surveillance can serve several purposes. Currently, the primary purposes, from a public health standpoint, are to guide the implementation of interventions to control CDAD in health care facilities and to monitor the impact of such interventions. These purposes may be achieved by detecting outbreaks and disease trends in individual health care facilities and by comparing CDAD rates among similar institutions. To properly make such comparisons, standardized case definitions are needed, the working group emphasized.

Clostridium difficile is an anaerobic, spore-forming bacillus that is responsible for a spectrum of disease, including uncomplicated diarrhea, pseudomembranous colitis, and toxic megacolon, which can, in some instances, lead to sepsis and even death. The main modifiable risk factor for CDAD is antimicrobial use, which increases risk through an alteration in the patient's normal lower-intestinal flora and, in some instances, also selects for highly antimicrobial-resistant strains of C. difficile. It is thought that the alteration in the complex ecology of the large bowel provides C. difficile an opportunity to thrive and produce disease, the working group reports.

A changed equation

The most common cause of nosocomial infectious diarrhea in the United States, C. diff is a longstanding problem that has nevertheless not been the focus of concerted national surveillance efforts. However, a new epidemic, toxin gene-variant strain of C. difficile (ribotype 027) — which can have 20 times the toxins as typical strains — has caused deadly hospital outbreaks, unusual infections in the community and even raised concerns about the food supply. Clearly, the C. diff equation has changed and infection control and surveillance efforts must change with it.

"For the last three years, every time we have heard about an outbreak and get isolates — in except one instance I can think of — we have found this epidemic strain," says Clifford McDonald, MD, a leading CDC C. diff investigator and a member of the surveillance workgroup. "This is a strain that prior to 2000 was a very minor player. So it is clear that this strain has spread across everywhere. It probably has a major role in what's going here."

To get a handle on the problem, the CDC is recommending that ICPs track the incidence of CDAD, including the clinical outcomes of patients. "At least then they could know where they are [locally] from their own history," McDonald says. While some areas have yet to be hit, it's clear something dramatic is happening in other regions and states such as New Jersey.

To estimate the incidence of CDAD in hospitalized patients in New Jersey, researchers conducted a retrospective survey of acute care hospitals. The recently published study used an Internet-based questionnaire that was distributed to all 81 New Jersey hospitals in early 2005.2 The survey collected information on hospital characteristics, the number of CDAD cases, C. difficile-positive laboratory test results, C. difficile-associated complications, deaths due to any cause within 30 days of diagnosis with C. difficile infection, health care-associated C. difficile outbreaks, recurrent CDAD cases, diagnostic test methods, and surveillance activities.

A 12-fold jump in outbreaks

Results for the 58 responding hospitals documented a twofold increase in rates of CDAD, a sevenfold climb in C. diff-associated complications, and a 12-fold jump in outbreaks during 2000-2004. During that time period participating hospitals reported a total of 13,394 CDAD cases. The mean annual rate of CDAD increased from 3.7 per 1,000 admissions in 2000 to 7.7 per 1,000 admissions in 2004.

A CDAD case was defined as a patient with symptoms of diarrhea and at least one of the following: positive toxin assay result, diagnosis of pseudomembranous colitis on sigmoidoscopy or colonoscopy, or histopathologic diagnosis. An outbreak was defined as at least three cases of health care-associated CDAD in the same general area within seven days. A complicated case was defined as a patient with CDAD in whom toxic megacolon, perforation of the colon, colectomy, or shock requiring vasopressor therapy subsequently developed within 30 days after diagnosis with CDAD. With adverse indicators climbing across the board, it was somewhat surprising that higher mortality rates were not immediately apparent.

"Unfortunately, this study was not able to capture data of deaths directly attributable to CDAD," says Esther Tan, MD, lead author of the New Jersey hospital study. "The data we collected was that of crude death rate within 30 days, which we found did not increase as dramatically as the other measures reported. However, this could be due to underreporting by respondents."

The study has limitations, but the results demonstrate that CDAD rates and associated complications rose rapidly among New Jersey hospitals during 2000-2004. "How much of the increase reflects rising awareness and how much is a true increase in incidence is unclear," Tan and co-authors conclude. "Nevertheless, the trend is dramatic and consistent with published reports in the United States, Canada, and Europe that evaluated CDAD rates during earlier periods."

In terms of surveillance activities, almost all participating hospitals tracked C. difficile laboratory results. However, a relatively low percentage of hospitals routinely monitored CDAD complications and deaths. Given recent reports of the emergence of hypertoxin-producing C. diff strains that are more treatment-resistant and potentially more virulent than other strains, the researchers recommended that hospitals implement or continue comprehensive surveillance programs to track the incidence of both health care-acquired and community-acquired CDAD, as well as patient outcomes. Surveillance of these entities will allow ICPs to identify quickly changes in CDAD incidence and severity that could be associated with the introduction of new, more virulent strains. In addition, rapid changes in incidence and detected outbreaks should be reported to public health officials, the paper concluded.

"We believe that there exists a severe underestimation of CDAD in the U.S.," Tan tells Hospital Infection Control. "Improving our CDAD surveillance programs, with standardization of CDAD case definitions and laboratory diagnostic strategies, will certainly be useful for us to establish the scale of the problem and evaluate disease control measures."

While the survey tracked the seemingly inexorable rise of an epidemic pathogen, the study also found that in the 2004 data more infection control professionals equaled less C. diff. Even as most adverse outcomes associated with C. diff increased in each year's data, researchers reported a "significant inverse association existed between the number of ICPs per 250 beds and C. diff-associated disease in 2004." The one ICP-to-250 bed ratio — which many say should be closer to one to 100 today — comes out of the landmark 1985 SENIC study by the Centers for Disease Control and Prevention.3 The C. diff investigators cite that report in noting, "Our observation that a higher ICP staffing level was associated with lower CDAD rates is consistent with previous studies demonstrating that a higher ICP-to-bed ratio is associated with reduction in rates of health care-acquired infections. We recommend that hospitals ensure that their infection-control programs employ sufficient personnel and other resources to implement adequate infection-control practices, with the goal of decreasing CDAD rates in their institutions."

The pattern generally trended toward a direct relationship between ICP staffing and C. diff rates, with hospitals with the highest infection control staffing levels virtually hitting ground zero in 2004. (See figure.) "While we do not presume a causal link as this was a cross-sectional survey, we do know that the day-to-day work of ICPs — such as surveillance, early detection of cases/outbreaks, frequent data analysis and application of infection control protocols — are all useful strategies for the prevention and control of health care-associated C. diff outbreaks," Tan says.

Indeed, the ICP/staff ratio could be a surrogate marker for a better overall culture of patient safety in a given hospital, McDonald notes. "There are a lot of cultural factors that we don't understand, we can't articulate much less quantitate that exist in hospitals," he says. "What is the culture of safety? Putting money into infection control programs is one aspect of that. A lot of it is just having administrators who care, who don't sleep at night when they hear about problems."

Regardless, more ICPs translates to more prevention opportunities. "They are freed up," he says. "They not just treading water, but moving out in the wards and doing prevention."

No small amount of effort is required to prevent C. diff infections, given the demands of isolating patients, maintaining contact precautions and trying to remove the stubborn spore-forming pathogen from environmental surfaces and patient rooms. The link between infection control staffing and resources was not lost on public health officials in Quebec following the deadly C. diff hospital outbreaks in the Canadian province in recent years. A $20 million cash infusion went directly to infection control programs, resulting in epidemic C. diff rates being beaten back to hailing distance of baseline.

"They put a lot of money into hospitals and ICPs after the outbreaks," McDonald says. "I think the administrators believed in that."

Still, other ICPs suspect the same protective effect found in the New Jersey hospitals could be found with other hospital infections than C. diff.

"Hospitals that have more ICPs probably have a more supportive administration that clearly sees the clinical impact that ICPs bring," says Susan Kraska, RN, CIC, an ICP at Memorial Hospital of South Bend, IN. "They probably have to fight less hard to obtain overall support, whether it be economic or administrative."

As McDonald noted, adequate staffing and resources puts the ICP in a more proactive stance. "It so much easier to plan ahead and put things in place," Kraska says. "When you have the support of your facility behind you, you are not battling everybody when you try to implement something. This [study] really says that a good program in support of infection prevention strategies and people in those positions makes a difference."

References

  1. Tan ET, Robertson CA, Brynildsen S, et al. Clostridium difficile–associated disease in New Jersey hospitals, 2000-2004. Emerg Infect Dis [serial on the Internet]. 2007 Mar. Available at www.cdc.gov/EID/content/13/3/498.htm.
  2. McDonald LC, Coignard B, Dubberke E, et al. The Ad Hoc Clostridium difficile Surveillance Working Group. Recommendations for surveillance of Clostridium difficile-associated disease Infect Control Hosp Epidemiol 2007; 28:140-145.
  3. Haley RW, Culver DH, White JW, et al. The efficacy of infection surveillance and control programs in preventing nosocomial infections in U.S. hospitals. Am J Epidemiol 1985; 121:182-205.