field gel electrophoresis type 1 (B1/NAP1) based on the different techniques of its
identification. The new strain B1/NAP1 differs from previous strains ofC. difficilein several
aspects including fluoroquinolone resistance and presence of the binary toxin. In March 2007,
B1/NAP1 had been found in 24 U.S. states as well as in the United Kingdom and parts of
continental Europe (12).
Nosocomial Infection
CDI is now the leading cause of identified nosocomial infectious diarrhea in the developed
world (13,14). U.S. hospital discharges for which CDI was listed as a diagnosis doubled from
82,000 or 31/100,000 population in 1996 to 178,000 or 61/100,000 in 2003 with the steepest
increase occurring from 2000 to 2003. The overall rate of acquiring CDI was especially high in
persons>65 years of age (228/100,000) compared with the age group with the next highest
rate, 45- to 64-year old (40/100,000) (9).
The majority of CDI are acquired nosocomialy and most patients remain asymptomatic
following acquisition (15). The risk of acquiringC. difficilewhile hospitalized is proportional to
the length of hospital stay, with 13% colonization after two weeks and 50% at greater than four
weeks of hospitalization (3,16). The carrier rate among healthy adults is approximately 3%.
Symptomatic and asymptomatic infected patients are the major reservoirs and sources for
environmental contamination. C. difficile can persist as spores for many months on
environmental surfaces within institutions including commodes, bathing tubs, electronic
thermometers as well as hands, clothes, and stethoscopes of personnel (15). Strict adherence to
infection control measures is critical in the control of CDI.
A study from 2004 showed that incidence is higher during winter months, which may
reflect increased patient census, severity of illness, and antibiotic use due to high rates of
respiratory infections (16).
Overall,C. difficileincurs more than an estimated $1 billion in health care costs in the
United States annually (17).
Community-Acquired Infection
In 2005, the CDC reported the occurrence of severe CDI, resulting in colectomy and death,
affecting several peripartum women and healthy persons living in the community (7). These
patient groups had generally been considered at low risk of acquiring CDI. Previous reports of
CA-CDI from the United States indicated that it was a very uncommon entity. However, a
retrospective Swedish study from 2004 (18) found that as many as 22% of 267 patients had
acquired their first episode of CDI in the community. Interestingly, most patients with CA-CDI
do not have a history of preceding antibiotic use (8).
TRANSMISSION
C. difficileis ubiquitous and has been cultured from soil; swimming pools; and salt, fresh, and
tap water (19). It persists as a highly resistant spore that may survive for months in the
environment. The gastrointestinal tract of young mammals, including humans, appears to be a
reservoir.C. difficileis transmitted via the fecal-oral route, either directly [hand carriage by
health care workers (HCWs), patient-to-patient contact] or indirectly (from a contaminated
environmental source) (16).
In the hospital setting, the bacteria has been cultured from telephones, call buttons, and
shoes of HCWs, fingernails, and numerous other objects, and it has been found in infected
patients’ rooms up to 40 days after discharge (3). Most cases of disease appear to be caused by
acquisition of the organism from an exogenous source, rather than from endogenous
colonization. In fact, colonization with either toxigenic or nontoxigenic strains appears to
protect from clinical disease (20). Fecal carriage among HCWs is rare.
RISK FACTORS
The major risk factors forC. difficileare antibiotic exposure, hospitalization, and advanced age
(>65 years of age) (Table 1).
272 Hjalmarson and Gorbach