Back to Annual Meeting Program

Background: Recurrence of C. difficile colitis (CDC) is common, yet the ability to predict CDC recurrences is virtually non-existent. Certain C. difficile virulence factors have been implicated in the development of severe forms of CDC, including toxins A and B, binary toxin, tcdC mutation (leading to higher toxin production) and certain strains of the bacteria such as ribotype 027. However, the role these factors play in the development of CDC recurrence is unknown. This study tested the hypothesis that bacterial virulence factors predict CDC recurrence and the need for admission to the hospital.

Methods: Patients ≥ 18 years of age treated at our institution for CDC of any severity were consecutively enrolled. CDC was defined as symptoms of colitis with a positive PCR stool test. Each bacterial isolate was studied for virulence factors: tcdC mutation, binary toxin and ribotype 027 by PCR, and the presence of toxins A and B using restriction fragment length polymorphism. Chi Square tests, t-tests and logistic and linear regression were used to determine which virulence factors predicted the number of recurrent episodes and the need for admission to the hospital for treatment.

Results: Sixty-nine patients (male: 57%) were studied, with a mean age of 64±13 years. Twenty-one (30%) patients were initially diagnosed as outpatients, while the remainder developed CDC during hospitalization. A majority of patients harbored at least one virulence factor (Table 1). There was no difference (p>0.05) between virulence factors among inpatients and outpatients. Binary toxin was the single virulence factor independently associated with CDC recurrence (p=0.02). A higher number of CDC recurrences was also observed with toxin A (p=0.01) and tcdC mutation (p=0.001) when either was present with binary toxin, with the combination of binary toxin and tcdC mutation being the strongest predictor, increasing the number of recurrences by an average of two episodes. The need for hospital admission for CDC recurrence was strongly associated with tcdC mutation (p=0.04), binary toxin (p=0.02) and ribotype 027 (p=0.02). The combination of toxins A, B and binary toxin exerted an additive effect by increasing risk of readmission three-fold when all three toxins were present (p=0.02). No resistance to metronidazole or vancomycin was encountered based on measurement of minimum inhibitory concentrations.

Conclusions: 1) Binary toxin is an independent predictor of CDC recurrence, which has not previously been reported. 2) The combination of binary toxin and tcdC mutation is associated with the highest number of CDC recurrences, such that their combined presence is associated with a 70% recurrence rate. 3) C. difficile which produces binary toxin may require longer antibiotic regimens to prevent disease recurrence.

Association of Virulence Factors with Recurrence and Admission for C. difficile Colitis

Virulence factor	Incidence (n=69)	Association with recurrence (p value)	Association with admission (p value)
Toxin A	61 (88%)	0.56	0.78
Toxin B	66 (96%)	0.73	0.60
Binary toxin	42 (61%)	0.02	0.02
tcdC mutation	39 (56%)	0.18	0.04
Ribotype 027	26 (38%)	0.32	0.02