Hospital acquired infection
Authors: John Starr
Journal: BMJ (2007)

Recent data published by the Health Protection Agency (HPA) show that each year in England around 7000 inpatients have methicillin resistant Staphylococcus aureus (MRSA) bacteraemia and more than 50 000 inpatients aged 65 years and over have Clostridium difficile infections.1C difficile cases rose by 5.5% in 2006 compared with 2005, whereas MRSA cases fell by 4.3% over a similar period. HPA spokespeople said they thought that the rate of increase of C difficile was slowing and MRSA rates had reached a plateau.

My own time series analyses of the reported data failed to detect any significant change in rates of C difficile or MRSA, though C difficile increases significantly during winter (www.geriatric.med.ed.ac.uk/john_starr.htm). The seasonal variation may be a result of many older people who require antibiotic treatment being admitted to hospital at that time of year. Despite the HPA data, there is a consensus that hospital acquired infection rates remain high and that recent control measures are having only a limited effect, especially on C difficile. With more than 2200 deaths attributed to C difficile on death certificates in England and Wales in 2004, the mortality rate is fast approaching that for road traffic accidents and is now around half that for suicide.2

Control of C difficile is difficult because, unlike MRSA, alcohol hand scrubs are ineffective and its spores are resistant to routine hospital cleaning.3 Moreover, old and frail patients are at highest risk of infection with C difficile. Since older people are living longer, hospital admissions of people over 85 years have increased relative to other age groups.4 This continuing change in case mix is likely to increase the absolute number of reported cases.

In December 2006, the Department of Health issued a letter on healthcare associated infections, in particular infection caused by C difficile, which called for urgent action.5 In addition to hand hygiene and environmental cleaning, recommendations include prudent antibiotic prescribing, isolation of infected patients, and use of personal protective equipment. Although there is a trend for reduced prescription of antibiotics in the community, it remains high in hospitals and accounts for 59% of prescription costs.6 7 Theoretically, isolation of infected patients should not be difficult. The National Health Service in England still has around 150 000 beds and even if just 20% of these are single rooms that can be used for isolation purposes, there should still be more than adequate capacity. However, the clustering of cases can put a strain on local resources. This is a particular concern with the emergence of hypervirulent strains.8

Another factor that may be driving the incidence of infection with C difficile is the community reservoir. Carriage rates in healthy people in the community may be around 5%, perhaps substantially higher in those connected with hospitals, and this may lead to community acquired infection.9 Indeed, the relative increase in community acquired C difficile far outstrips that seen in hospital, despite reduced antibiotic use, and may relate to increased use of proton pump inhibitors and other drugs that suppress gastric acid production.10 More than 13 000 cases of community acquired C difficile occur each year in the UK, three quarters of which are in people who have not been in hospital during the previous year. In contrast, the HPA identified fewer than 100 community acquired cases of MRSA between 2003 and 2005. This raises the question of whether C difficile can still be thought of as purely a hospital acquired infection and, if not, whether other infection control measures are needed, such as screening people in the community before they are admitted electively.

Early accurate diagnosis is fundamental to any infection control programme, whether based in hospital or the community. Laboratory methods to detect C difficile have varied considerably in the UK.11 Though variation has been reduced in England, it is still difficult to make comparisons with data from other countries, and thus assess the effects of their infection control policies. Denmark, for example, preferred culture to toxin detection as a diagnostic tool. Denmark also reported two fatal cases of C difficile enterocolitis in elephants in 2006, a reminder that animals, including household pets, can be a reservoir for the organism.

A report from the HPA published last year recommended greater international cooperation to tackle C difficile by sharing information about the appearance of new strains or changes in the prevalence of known strains.

It also emphasised that infection control guidelines have stayed essentially the same for more than a decade, and were implemented inconsistently across England.12 The recent HPA report presents a mixed message. Although both C difficile and MRSA are closely associated with use of antibiotics, in other ways they are quite different. Infection control policies for MRSA have been more successful than for C difficile, yet data on hospital acquired infections are often grouped together. In particular, because of the rise in community acquired infection it is important to consider whether a C difficile infection control policy solely focused on hospitals remains appropriate.