RT-PCR Could be a More Rapid Test for C Difficile on Environmental Surfaces

Mattresses, toilet floors, and room floors were places where C difficile was commonly detected in areas inhabited by C difficile infection positive populations.

There might be a new way to detect clostridiodes difficile on surfaces rapidly, which could be especially crucial in hospital settings.

A team, led by Rachel J. Grainger, Department of Clinical Microbiology, RCSI Education and Research Centre, Royal College of Surgeons in Ireland, Beaumont Hospital, compared the detection of C difficile by RY-PCR to culture-based strategies and determined which is more sensitive and specific in a clinical environment.

Detecting C Difficile

Detection of C difficile from the environment is generally done using bacterial culture, which can take several days to receive results. In addition, environmental surveillance is not usually done routinely and only conducted during outbreak investigations or as part of research.

“Environmental surveillance for Clostridioides difficile is challenging,” the authors wrote. “There are no internationally agreed recommendations on which method should be used when environmental surveillance is undertaken.”

Currently, culture-based tests are the most commonly used testing methods but can take 48 hours for results. Molecular methods also offer lower TATs, but these methods are not yet optimized.

There is a need for more rapid methods to detect C difficile, which could aid in preventing infections.

“Unlike culture for CD, which takes too long, molecular methods such as PCR have potential in monitoring the patient environment in hospitals for CD and might be used to provide reassurance to patients and hospitals before patients are admitted to a hospital bed,” the authors wrote.

The study included 44 near patient areas of patients who are C difficile positive, each 1 sampled using contact plates and moistened flocked swabs. The investigators took environmental samples over a 6-month period in an adult 820-bed tertiary referral hospital from the floor of the room, the bed rail, the tray table, the call bell, the mattress, the toilet floor, the toilet flush handle, and the internal bathroom door handle.

Finding Results From Samples

There were 352 samples taken using flocked swabs, resulting in 59 positive samples. This was more than the 35 positive samples found with alcohol treated and sub-cultured onto C difficile selective agar (P = 0.01).

Moreover, there were 23 samples positive using both culture methods, 36 samples positive using the CHROMID agar only, and 12 samples positive using the alcohol treatment and culture method only.

There were 71 samples culture-positive for C difficile using the flocked swab method compared to 29 samples using the contact plates.

The results also show 5.43% (n = 19) of samples were positive using both methods, 14.86% (n = 52) were positive only by the flocked swab and culture-method, and 2.86% (n = 10) were positive only by contact plates.

Finally, 15.14% (n = 53) of samples were positive using both the tcdB RT-PCR assay and the culture-based method, while 4.86% (n = 17) were positive using the RT-PCR negative for tcdB and 7.43% (n = 26) were RT-PCR positive for tcdB but culture-negative.

The investigators also analyzed positive samples taken from specific area of the infected patient areas.

The surface with C difficile most frequently found on it was mattresses (n = 15; 36 %), followed by room floors (n = 14; 29 %) and toilet floors (n = 9; 31 %) using a flocked swab followed by RT-PCR for tcdB.

However, after using the flocked swab sampling technique and culture, the investigators detected C difficile from mattresses (n = 11; 26 %), toilet floors (n = 8; 28 %), and room floors (n = 13; 27 %). When they used contact plates, they detected C difficile most frequently from the room floor (n = 5; 10 %), toilet floor (n = 7; 24 %), and the arm of armchair (n = 4; 27 %).

The results show detection using moistened flocked swabs followed by RT-PCR or culture resulted in more C difficile detected compared to using the contact pates. The sensitivity of a RT-PCR assay for tcdB was 76% compared to the culture methods, while the specificity was 91%.

“Despite the lower sensitivity and specificity, RT-PCR could potentially offer a more rapid and practical alternative,” the authors wrote. “While culture picked up more positive samples for CD, PCR detected about three-quarters of the positive samples but the results from PCR were available within hours and not days.”

The investigators suggested future research should focus on confirming the role of PCR in the prevention and control of C difficile in hospitals.

The study, “A comparison of culture methods and polymerase chain reaction in detecting Clostridioides difficile from hospital surfaces,” was published online in the Journal of Medical Microbiology.