C. difficile incidence ‘underestimated’

Guys & St Thomas’ Hospital Trust recently hosted a symposium on C. difficile in partnership with molecular diagnostics company, Cepheid – bringing together a selection of the world’s leading authorities on infection control. Speakers included Professor Brian Duerden CBE, inspector of microbiology and infection control at the Department of Health, Dr Fred Tenover, senior director of scientific affairs at Cepheid, and Professor Mark Wilcox, consultant/clinical director of microbiology, Leeds General Infirmary. The symposium asked: “Why have we seen such a rise of C. difficile in the UK when we have known about the infection since the 70s?” Healthcare-associated diarrhoea has plagued hospitalised patients for decades. For many years, antibiotic-associated diarrhoea was attributed to Staphylococcus aureus. Although the organism Clostridium difficile was described by researchers Hall and O’Toole in 1935,1 it was not until 1977 that Bartlett and colleagues identified C. difficile as the causative agent of “antibiotic-associated pseudomembranous colitis”.2 Today, concern about the rise in the rate of Clostridium difficile infections (CDI) now rivals concerns about methicillin resistant Staphylococcus aureus infections. C. difficile infections, particularly healthcare-associated diarrhoea, have been increasing in incidence and severity, and are associated with an increase in lengths of hospital stay, costs, morbidity, and mortality among patients. C. difficile is a gram-positive spore forming anaerobic bacillus found in approximately 20% of hospitalised patients. It can cause severe diarrhoea and lead to serious infection of the colon.

The organism’s spores are very resilient to heat and desiccation and can remain viable in the hospital environment for weeks to years. C. difficile has evolved from an uncommon healthcare-associated pathogen that primarily affected elderly patients, to a global healthcare concern affecting not only the elderly, but otherwise healthy young adults and children both in healthcare and community settings. Factors contributing to this dramatic increase include widespread use of broad-spectrum antimicrobials, and increased resistance of C. difficile isolates to many antimicrobial agents, which enhance their spread in communities and institutions. Control of outbreaks of CDI, especially those caused by the 027/NAP1/BI strain and other emerging epidemic strains, is difficult, and requires significant infection control efforts and judicious antimicrobial stewardship. The availability of rapid and accurate C. difficile tests represents an important advancement in addressing this growing epidemic. Immediate identification of CDI enables clinicians to administer appropriate therapy sooner, and supports immediate and prompt infection control measures to reduce the risk of this dangerous infectious agent spreading within an institution. The Government has been fighting the C. difficile battle head on but the emergence of more virulent strains and the links between infections means that the battle is far from won. While some hospitals have shown a significant decline in rates, others have seen an increase, and it is now thought that C. difficile could be twice as high as previously recorded because the current testing methods only detect between 20% to 80% of C. difficile cases.

Having known about the infection for a number of years, infection experts have been debating the causes for the continual spread of the infection. Three key reasons were identified at the conference. Firstly, the emergence of new strains with greater virulence and greater spore production is a major factor in facilitating the spread of the infection. Secondly, sub-optimal EIA tests with only 50% sensitivity are likely to miss a significant number of culture-positive (i.e. infectious) C. difficile cases (false negative results). This results in a large number of patients not being subjected to isolation conditions necessary to interrupt the spread. Lastly, the increased use of antibiotics – particularly fluoroquinolones – predisposes patients to infection. It was also pointed out that an increase in flu (H1N1) patients could lead to patients demanding unnecessary antibiotics, leading to added pressure on staff, which could then cause potential for more CDI cases. So, where are we now and what do we need to do to improve infection control?