Presentation Abstract

Session: 018-Clostridium difficile
Tuesday, Sep 10, 2013, 12:00 PM - 2:00 PM
Presentation Title: K-168a - Investigating Clostridium difficile Transmission Using Whole Genome Sequencing (WGS): Few Cases Follow Direct Contact with a Symptomatic Donor
Location: Exhibit Hall A
Presentation Number: K-168a
Pres. Time: Tuesday, Sep 10, 2013, 12:00 PM - 2:00 PM
Category: K
Keywords: Clostridium difficile; Transmission; WGS
Author(s): J. Martin1, D. Eyre2, D. Mawer1, W. Fawley1, A. S. Walker2, T. Peto2, D. Crook2, M. Wilcox1;
1Leeds Teaching Hosp. NHS Trust, Leeds, United Kingdom, 2NIHR Oxford BioMed. Res. Ctr., Oxford, United Kingdom
Financial Disclosures:  J. Martin, None..
D. Eyre, None..
D. Mawer, None..
W. Fawley, None..
A. S. Walker, None..
T. Peto, None..
D. Crook, None..
M. Wilcox, None.
Abstract: Background: Control of C. difficile infection (CDI) has centred on source isolation of symptomatic patients to prevent transmission. We investigated the proportion of CDI cases that are acquired following ward contact with a donor matched by WGS. Methods: We carried out a 21 month (Aug10-Apr12) observational study of consecutive CDI cases in Leeds, UK. All cell culture cytotoxin assay positive diarrhoeal samples were analysed by ribotyping and WGS. Single nucleotide variants (SNPs) between isolates were compared. A donor was sought for all new CDI cases between Dec10 and Apr12. Donor-recipient matches suggesting transmission were based on ward contact within defined infectious periods (≤56 days after donor’s positive test) and incubation periods (≤90 days before recipient positive test), and matching ribotype or WGS (≤2 SNPs). Persistent ward contamination (≤90 days) with spores was explored as a source for cases with no direct ward donor. Results: Donors were sought for 495 new CDI cases (15% ribotype 027) in 445 patients (median age 77 years). Table 1 shows new CDI cases for which a ribotype/sequence-matched donor was found.
Of 338 cases without direct ward/‘spore’ donors (as defined above) by WGS, 128 had a sequence which matched a previous case representing either lengthy or unexplained transmission. However, 44% of cases had no previous sequence match at all. Conclusions: Only a sixth of CDI cases in a large UK centre could be attributed to ward contact with a symptomatic patient using WGS to identify transmission. A further 10% have a possible donor when spore contamination of wards is considered as a source. This is the first study using a reference method diagnostic test and WGS to demonstrate such low CDI transmission rates. Further investigation is urgently required to establish other sources of CDI.
Table 1 - new cases of CDI for which a ribotype/sequence matched donor was found
Type of contactRibotype matchSequence match
Direct ward contact between donor and recipient97 (20)78 (16)
Ward 'spore' exposure only(max. 90 day ward contamination time)96 (19)49 (10)
No donor found within direct/'spore' contact periods302 (61)338 (68)
No data(sequencing failed or low quality)0 (0)30 (6)
Total number of cases495 (100)495 (100)

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