Patient population
As shown in Figure 1, 800 adult patients were admitted to the ICU during the study period. Of these, 115 developed diarrhea and 33 (28.70%) were identified to have CDI. Another 25 toxigenic C. difficile strains were isolated from patients without diarrhea, and defined as CDC cases. The overall prevalence of CDI and CDC was 4.12% and 3.12%, respectively, and all cases were healthcare facility-associated. One patient had recurrence of infection, one patient transitioned from CDC to CDI, and two patients had infections with two different types. The CDI and CDC patients had median age of 54.15 and 62 years, male proportion of 66.7% and 68%, and period from admission until positive test result of 17.06±12.97 and 31.16±33.85 days, respectively. Neither age nor sex showed any significant difference between the groups. To assess the potential risk factors and clinical characteristics, 66 non-CDI and 50 non-CDC patients were included as control groups.
Clinical characteristics and risk factors for ICU patients with CDI
As illustrated in Table 1, univariate analyses were conducted to determine the differences between the CDI group and the non-CDI control group in terms of clinical characteristics, diagnosis, and treatment. The CDI patients were more likely to suffer from fever (OR, 6.786; 95% CI, 2.634–17.483; P<0.001) and metabolic disorders (OR, 3.28; 95% CI, 1.363–7.893; P<0.05) than the non-CDI patients. The CDI patients also had a larger number of comorbidities (P<0.05). Compared with the non-CDI patients, the CDI patients more frequently received enteral feeding (78.8% vs. 50%; OR, 3.714; 95% CI, 1.416–9.74), antiviral drugs (15.2% vs. 1.52%; OR, 11.607; 95% CI, 1.296–103.948), and fluoroquinolone (21.2% vs. 3%; OR, 8.615; 95% CI, 1.678–44.247) during their hospitalization (P<0.05). Furthermore, a larger proportion of CDI patients were administered more than one type of antibiotic (P<0.05). To further assess the potential risk factors for CDI, a multivariable logistic regression analysis was performed. The results showed that fever, metabolic disorder, and treatment with fluoroquinolone or combined antibiotics were risk factors associated with development of CDI among ICU patients. However, treatment with metronidazole was found to be a protective factor (OR, 0.042; 95% CI, 0.006–0.288; P=0.001).
Clinical characteristics and risk factors for ICU patients with CDC
The median hospital stay for CDC patients was 62 days and significantly longer than that for non-CDC patients (P<0.05). This difference was further verified by the multivariable logistic regression model. Colonization of C. difficile did not cause any significant differences in laboratory test indices, including leukocyte count and serum albumin or creatinine levels. However, patients with respiratory or neurological disease were more likely to acquire asymptomatic CDC. Number of comorbidities was a potential risk factor for CDC patients (OR, 36.509; 95% CI, 2.602–512.183; P=0.08). For treatment procedures, surgical intervention, enteral feeding, antifungal agent usage, and carbapenem medication were more frequently found in CDC patients than in non-CDC patients (P<0.05). The multivariable model analysis showed that vancomycin was an independent risk factor (OR, 18.168; 95% CI, 1.036–318.503; P=0.047), while metronidazole was a protective factor (OR, 0.013; 95% CI, 0–0.512; P=0.021) for CDC (Table 2).
Molecular characteristics of C. difficile
The toxin types were detected for the 58 C. difficile strains isolated from the CDI and CDC patients. In total, 34 (58.6%) were A+B+ (positive for both tcdA and tcdB) and 24 (41.3%) were A−B+ (negative for tcdA and positive for tcdB). Specifically, 20 (60.6%) were A+B+ and 13 (39.4%) were A−B+ in the CDI group, while 14 (56%) were A+B+ and 11 (44%) were A−B+ in the CDC group.
MLST was also performed on the strains, and 18 sequence types (STs) were identified (Figure 2). In the CDI group, ST2, ST81, ST54, and ST3 were the major STs, constituting 19%, 15%, 12%, and 12% of the strains, respectively. In the CDC group, ST81, ST35, ST37, and ST54 were the dominant types, accounting for 20%, 12%, 12%, and 12% of the strains, respectively.
Based on the STs of the strains, a map was constructed to compare the temporospatial relationships of the same STs in the two groups during the study period (Figure 3). Two overlaps were detected within the CDI group for ST2 and one overlap was detected between the CDI and CDC groups for ST103. No overlaps were detected among the other STs.