Incidence and severity
The incidence of CDAD is generally higher in the winter months, probably associated with the increased incidence of infections such as community-acquired pneumonia requiring hospitalization and the use of broad-spectrum antibiotics. The overall incidence of CDAD is increasing,10 as the major risk factors for development of CDAD, namely increased age, antimicrobial use, increased severity of underlying illness, and surgical manipulation of the gastrointestinal tract, are more prevalent in hospitalized patients.
The severity of disease may also be increasing related to changes in susceptibility to antimicrobials (clindamycin-resistance11 and fluoroquinolone-resistance), the expression of a "binary toxin," or variations in a gene that down regulates toxin production.12,13
Over the past 2 years, several states have reported increased rates of C. difficile-associated disease, noting more severe disease and an associated increase in mortality. It is not clear at this time if the population at risk (those most susceptible to acquiring C. difficile-associated disease) is changing. The new strain appears to be more virulent, with ability to produce greater quantities of toxins A and B. In addition, it is more resistant to the antibiotic group known as floroquinolones.
As of November 2007, this strain, called BI/NAP1/027 has been reported in 38 states in the United States (Figure 2).
ref. http://www.cdc.gov/ncidod/dhqp/id_Cdiff_data.html
In addition to the increased severity of disease, a review of US death certificates for the period 1999-2002 indicates an increase in the annual number of deaths attributed to C. difficile that is most pronounced in those >60 years of age (Figure 3).13
