APIC conducts national C. diff prevalence study
Will findings be as shocking as MRSA survey?
Clostridium difficile — which has caused a series of severe hospital outbreaks and unexplained community cases due in part to the emergence of a hypervirulent new epidemic strain (NAP1) — is the subject of a landmark prevalence study.
To gain a better perspective on this important emerging pathogen, the Association for Professionals in Infection Control and Epidemiology (APIC) is conducting the first national prevalence study of C. diff. The APIC Research Foundation C. difficilePrevalence Study will be conducted May 1-23, 2008. More than 5,000 health care facilities are being invited to participate by providing a one-day "snapshot" of C. difficile infections within their institution.
Don't expect the resulting picture to be suitable for framing. A gram-positive, spore-forming anaerobic bacillus that was first linked to disease in 1978, C. diff has always been among the nastiest of enteric pathogens. Gastrointestinal infections range in severity from asymptomatic colonization to severe diarrhea, pseudomembranous colitis, toxic megacolon, intestinal perforation, and death. C. diff took a sharp turn for the worse in the last few years when it mutated into a highly virulent form (NAP1) that is 20 times more toxic than typical strains. Sharp spikes in illness and death resulted. The strain is causing high-mortality outbreaks in hospitals, where C. diff can be easily be transmitted from environmental surfaces and on the hands of health care workers. Vulnerable patients include those exposed to high levels of antibiotics that wipe out other bacteria that may delay or prevent onset of opportunistic C. diff. Perhaps the most disturbing recent development is the pathogen appears to have left the hospital to cause serious infections in previously healthy people in the community, many of whom have no history of recent hospitalization or prolonged antibiotic use that typically precedes C. diff infection.
High prevalence predicted
The principal investigator for the APIC prevalence study is William Jarvis, MD, a private consultant who formerly was a leading investigator of hospital outbreaks for the Centers for Disease Control and Prevention. Jarvis conducted a similar landmark study for APIC last year on methicillin-resistant Staphylococcus aureus (MRSA), with findings showing prevalence in U.S. hospitals was a striking eight to 11 times higher than previous estimates. Similar results with C. diff would not surprise him.
"I feel very strongly that it will be very similar with what we found with MRSA," he says. "If you look at the data to date they have primarily been [from] a very limited number of hospitals and there have been some studies looking at administrative data [e.g., discharge data]. But there are problems associated with that as well, and I am anticipating that we are going to find much higher numbers."
L. Clifford McDonald, MD, one of the leading C. diff experts at the CDC, consulted with APIC and Jarvis in the survey effort. "It will be a snapshot of the burden of hospitalized C. diff [cases]," he says. "It will give better granularity than the discharge data because they will categorize the cases, but it will also be limited by their response rate. I suspect they will find [C. diff] numbers that are bigger than the discharge data."
Though the CDC is not receiving as many reports of hospital outbreaks, that does not necessarily mean they are not occurring, he adds. "They know that the epidemic strain is playing a role," he says. "A lot of places have had an outbreak and they know what to do and they have handled it." Though C. diff outbreaks can be labor-intensive, even hospitals battling the NAP1 strain have been successful by "bundle" approaches such as education, increased and early case finding, expanded infection-control measures, development of a C. diff infection management team, and antimicrobial management.1
Positive news indeed, but all signs suggest the burden of C. diff is increasing and will continue to present problems in both the hospital and community. McDonald provided the most current CDC estimates of the burden of C. diff-associated disease (CDAD) in a recent editorial. "The importance of controlling CDAD in U.S. inpatient health care facilities (i.e., both acute and long-term care facilities) cannot be overstated," he wrote.2 Citing unpublished CDC data, he estimated that the number of U.S. acute care hospitalizations went from 98,000 in 2000 to 178,000 in 2003. C. diff hospitalizations are thought to have topped the quarter-million mark by 2005, he noted, adding "[A]lthough there is increasing concern over the emergence of severe CDAD in previously low-risk populations, including healthy persons living in the community (some of whom have not had preceding antimicrobial exposures), the majority of human CDAD cases still occur in association with inpatient health care exposures."
And that's exactly where the APIC survey will focus, though Jarvis will try to glean some indicators on other C. diff issues in the analysis. "The survey questionnaire will include some of the same questions as [the MRSA survey] about demographics, hospital location and type," he tells Hospital infection Control. "In addition, we will have some information on laboratory tests commonly used at the facility, so I have a better sense of what tests are used where."
The survey will include a series of questions regarding infection control for C. diff, including patient isolation, environmental cleaning, and hand hygiene practices and agents. (The alcohol gel products now ubiquitous in hospitals are not generally considered as effective against C. diff as soap and water.) "We are also asking about antibiotic control programs since antibiotic exposures are clearly a very more important part of the epidemiology and risk factors for C. diff."
Infection control professionals at the responding hospitals will be asked to give the number of patients known to be infected or colonized with C. diff on the day the survey is done. "There is a detailed questionnaire on each of the C. difficile patients identified, [including] whether they were infected or colonized and exposures that they had prior to acquiring C. diff," Jarvis explains. The survey will not include any patient or institutional identifiers and will only be released as aggregate data, he emphasized. Though the effort is aimed at hospitals, public health officials are hopeful the survey will provide some information on community-acquired C. diff.
Community cases, NAP1 strain
"If the patients have only been in the hospital one or two days, then that might provide a little bit of a snapshot of community [cases]," says James Hadler, MD, state epidemiologist and director of the infections disease section at the Connecticut Health Department. "That would be helpful. [Regardless], in the era of this toxigenic strain it is important to know how prevalent C. diff is, because many hospitals are still struggling with how best to try and control it. To know the size of the problem might help determine how feasible [various infection control] strategies might be."
The survey may yield some useful data on community-acquired cases, but it will be harder to determine whether the infecting agent is the NAP1 strain, Jarvis said. CDC definitions will be included to cite whether the infection or colonization is considered of a community source. "In addition we are trying to get a sense of severity of illness, so we are asking questions such as the number of patients who died, who responded to therapy within five or six days, or who required emergency surgery," Jarvis says.
Data on severe cases may suggest the NAP1 strain was the infecting agent, but Jarvis concedes confirmation will be impossible in most cases. "The only way to really know that is genetic testing and most hospitals don't have that capability," he says. "It is probably underreported. We will collect data so we can stratify patients by severity of illness, get information on mortality, and also we are asking them about whether they know if it is that strain. If they sent it to a reference lab or to CDC, they would know that."
The survey originally was not going to include any questions on surveillance cultures or testing nonsymptomatic patients, but Jarvis decided to include the topic after hearing anecdotal accounts of such practices. "In my travels around the country, I have been talking to ICPs about this issue. Actually, a number of them commented that they do screen for C. diff," he says. "I'm not anticipating we are going to see a huge number of people that are [screening] and identifying patients who may be colonized with C. diff. But I think that part of it will be very interesting. I don't think anybody has ever looked at that before."
The survey also should provide much-needed insight on the level of C. diff in the small hospital that may not be included in academic studies and research, he says. "We hoping that this study will shed more light on the extent and magnitude of the problem," he tells Hospital Infection Control. "Then through APIC and other education programs we can come up with a strategy for the control of C. diff. Obviously, it is going to be a challenge."
Following the survey, APIC will develop a guide to the elimination of C. diff, including strategies for controlling transmission as well as an educational Webinar series. The association also will hold a conference in late 2008, featuring results of the prevalence study, along with the latest science, epidemiology and best practices for the elimination of C. diff transmission.
References
- Muto CA, Blank MK, March JW, et al. Control of an outbreak of infection with the hypervirulent Clostridium difficile BI Strain in a university hospital using a comprehensive "bundle" approach. Clin Infect Dis 2007; 45:1,266-1,273.
- McDonald, LC. Confronting Clostridium difficile in inpatient health care facilities. Editorial commentary. Clin Infect Dis 2007; 45:1,274-1,276.
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