Comparison of Perirectal versus Rectal Swabs for Detection of Asymptomatic Carriers of Toxigenic Clostridium difficile

Abstract

bFor long-term care and spinal cord injury patients, the sensitivity, specificity, and positive and negative predictive values of perirectal versus rectal cultures for detection of asymptomatic carriers of Clostridium difficile were 95%, 100%, 100%, and 97%, respectively. Perirectal cultures provide an accurate method to detect asymptomatic carriers of C. difficile. Clostridium difficile is the most important cause of health careassociated infectious diarrhea. Asymptomatic carriage of toxigenic C. difficile is also common in hospitals and long-term-care facilities (LTCF) (1-4). Although the presence of patients with C. difficile infection (CDI) is considered the major risk for transmission, asymptomatic carriers also have the potential to shed spores and contribute to transmission (1, 2, 4). Rectal or perirectal swab cultures are commonly used for the detection of carriers of health care-associated pathogens. Because rectal swabs may cause discomfort for patients and are contraindicated in the setting of neutropenia to avoid the risk of infection with skin and mucosal breakdown (5), perirectal swabs may be preferred. Perirectal swabs have been shown to be equivalent to rectal swab specimens for the detection of other health care-associated pathogens (6, 7), but no previous studies have compared the two methods for the detection of carriers of C. difficile. We have previously shown that perirectal swabs provide excellent sensitivity in comparison to stool samples for the detection of patients with CDI (8); however, CDI patients typically have much higher levels of C. difficile in stool than asymptomatic carriers (1,8). Here, we tested the hypothesis that the collection of perirectal swab cultures would provide an accurate but less invasive diagnostic strategy for the detection of asymptomatic carriers of toxigenic C. difficile.The study was conducted at the Cleveland VA Medical Center. All residents on two LTCF wards and on a spinal cord injury unit who were available and without abdominal pain or unformed stool were approached for enrollment; these groups were chosen for study because we have previously demonstrated relatively frequent asymptomatic carriage of C. difficile in these patient populations (1, 9). Subjects with unformed stool or abdominal pain were excluded from participation. Using BD BBL CultureSwabs (Becton, Dickinson, Cockeysville, MD), cultures were first obtained from the perirectal area. A second swab was then used to collect rectal cultures through insertion into the rectum. The perirectal swab was collected first to avoid the potential for contamination of the perirectal area during collection of the rectal swab. It was noted whether the swabs had evidence of fecal staining, but all swabs were processed. The swabs were transferred to a Whitley MG1000 anaerobic workstation (Microbiology International, Frederick, MD) and cultured for C. difficile on prereduced cycloserine-cefoxitin-brucella agar containing 0.1% taurocholic acid and lysozyme at 5 mg/ml (CDBA) as previously described (10). The n...

Detection of Clostridium difficile in Feces of Asymptomatic Patients Admitted to the Hospital

“…Davies et al studied the performance of the same GDH ELFA in diarrheal samples submitted for C. difficile testing and reported a higher sensitivity of 95.8% and a similar specificity of 91% (40). The lower sensitivity found in our study could be due to presence of lower numbers of C. difficile in fecal samples of asymptomatically colonized patients than in patients with CDI (18). However, we do not exclude the possibility that the percentages change when larger number of fecal samples are tested.…”

“…The studies in asymptomatically colonized patients vary greatly in patient inclusion criteria, tested material, and applied diagnostic and gold standard tests. For instance, a great number of the studies only test rectal swabs or use a combination of stool samples and rectal swabs (4,8,18,22,23,31,34). Guerrero et al showed that asymptomatic carriers have lower numbers of C. difficile in their rectal swab than CDI patients, indicating that stool samples should be preferred (4).…”

“…Approximately 5 to 15% of newly hospital admitted patients carry C. difficile in their feces (4,5,(14)(15)(16)(17). Carriage rates of residents in long-term-care facilities vary from 4 to 51% but in general tend to be higher than in hospitalized patients (3,14,18). Asymptomatic colonization of C. difficile in the pediatric populations is very high; approximately 37% of children are asymptomatic carriers in their first year of life, decreasing to 15% for children between 1 and 8 years of age (19).…”

European Society of Clinical Microbiology and Infectious Diseases: update of the diagnostic guidance document for Clostridium difficile infection

“…Also, an exception has to be made for patients suspected of CDI who have ileus. In these patients, a rectal swab can be used with adequate sensitivity and specificity for (toxigenic) culture, NAAT or GDH EIA [89,90]. The use of perirectal swabs for NAAT or GDH EIA testing might also be an alternative in selected patient populations but may depend on the presence of faecal staining of the swab [89e91].…”

Hygienemaßnahmen bei Clostridioides difficile-Infektion (CDI)

“…Voraussetzung für eine rationale Diagnostik ist der Einschluss von ausschließlich ungeformten Stuhlproben [18,101]; Ausnahme sind Patienten mit Darmparalyse aufgrund eines toxischen Megakolons, bei denen die Diagnostik auch aus Rektalabstrichen mit ähnlich hoher Sensitivität möglich ist [102,103]. Wiederholungstests werden auf Grund der Studienlage generell nicht empfohlen.…”