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Title: Clostridium difficile in colorectal surgery : a study of local epidemiology, asymptomatic carriage, in-patient disease and surface environmental contamination
Author: Reddy, Surekha Nemakallu
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2013
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Clostridium difficile was identified as an infective agent in the late 1970s and early 1980s and causes a spectrum of disease ranging from asymptomatic carriage, mild colitis, pseudomembranous colitis (PMC) to fulminant colitis and even death. Since its recognition as an infective pathogen, C. difficile has become the principal cause of nosocomial diarrhoea in adults. The main aims of this four-part thesis were to determine the extent of Clostridium difficile infection (CDI) within the local in-patient population and to establish the epidemiology of CDI within the specialty of colorectal surgery. The first study focused on the burden of CDI to the diagnostic laboratory and the relative incidence of disease in different clinical specialties over an 8-year period (2000 to 2007) in a region that had not been affected by the hypervirulent 027 strain. A 27-fold increase in the number of faecal samples analysed by the enteric laboratory occurred from 2000 to 2006 and the total number of potential CDI cases increased over the same period, with a decline finally seen in 2007. One-fifth of all toxinpositive samples were from age groups under 60 years of age providing further evidence that CDI was not just a disease of the elderly. Although Medicine of the Elderly provided the greatest faecal analysis workload; Renal Medicine/Transplant Surgery, Intensive Care, Infectious Disease and Gastrointestinal Medicine all had higher incidences of CDI than Medicine of the Elderly. Similarly the low risk group of Paediatrics was also starting to show a small but notable increase in potential incidence. Potential excess costs for CDI in this region rose from £3.5 million to £29 million over the study period. The second study aimed to assess the potential impact of CDI within all surgical services. In the absence of 027, a further aim of this study was to assess if the more severe and extreme forms of C. difficile disease were occurring from 2000 to 2006. Colorectal surgery had the greatest number of CDI episodes followed by Upper Gastrointestinal Surgery and Urology. Despite the total number of C. difficile toxinpositive in-patients increasing each year, a similar increase was not demonstrated in the number of patients diagnosed with more severe forms of CDI or in the number of CDI patients treated with surgical intervention. In the cases requiring surgical intervention up to 40% of patients did not present with diarrhoea and up to 50% of patients did not have a C. difficile toxin-positive faecal sample prior to surgery. Demonstrating the importance of clinical recognition of the entire spectrum of C. difficile related disease. The post-operative mortality rate for fulminant CDI was 26%. High mortality figures for fulminant CDI treated surgically have not changed significantly over the last two decades and may relate to surgical referral for CDI often occurring late when the patient is in extremis. The third and fourth studies examined the specific burden of C. difficile in the colorectal surgical patient population and the environmental surface contamination within colorectal wards. An asymptomatic carrier rate of 6.1% was identified in the out-patient colorectal surgical population. Asymptomatic carriers admitted from the community play an important role in sustaining the transmission of disease within the hospital environment with 42.8% of C. difficile strains only identified in the in-patients faecal samples but not on the surface environment of the wards. Standard enteric hospital laboratory CDI diagnosis using enzyme immuno-assay for toxin A+B detection was 52% less sensitive then toxigenic culture with a false positive rate of 2.5%. Toxigenic culture identified a further 58 colorectal surgical in-patients with CDI. Of all the C. difficile isolates identified from in-patients and the surface environment ribotype 001 was the commonest strain, consistent with other local studies where ribotype 001 has emerged as the dominant strain. A large proportion of the in-patient ribotype 001 isolates showed resistance to ceftriaxone and ciprofloxacin. The ribotype 001 isolates from the surface environment showed decreased resistance to ceftriaxone compared with the in-patient strains. Similarly 4.6% of all in-patient isolates showed intermediate resistance to vancomycin but no vancomycin resistance was demonstrated in the environmental surface isolates and may represent increased development of C. difficile resistance mechanisms in the host. The patient bed frames were the commonest contaminated environmental surface with C. difficile, followed by the patient's bedside lockers and tables. Therefore the risk of a patient ingesting a C. difficile spore from the surface environment is high. Following the introduction of a new cleaning protocol during the environmental sampling study a statistically significant reduction in environmental C. difficile surface contamination and in the number of CDI colorectal in-patients was demonstrated. Acquisition of CDI from the surface environment in hospitals is not to be under-estimated and judicious application of infection control measures remains an important factor in preventing CDI transmission.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (M.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available