Deaths involving Clostridium difficile or MRSA, Wales: 2015

In 2015, there were 108 deaths involving Clostridium difficile (C. difficile) and 22 deaths involving Meticillin-resistant Staphylococcus aureus (MRSA) in Wales.

The C. difficile age-standardised death rate in 2015 is not statistically different to the lowest that was recorded in 1999 (34.3 deaths per 1 million persons in 2015).

The age-standardised death rate for MRSA has also dropped since its peak in the mid-2000s, to 7.0 deaths per 1 million persons in 2015.

Age-specific death rates for C. difficile and MRSA are highest in those aged 85 years and above. For MRSA, age-specific rates in males are higher than those in females.

The majority of deaths involving C. difficile or MRSA occur in NHS hospitals.

“The number of deaths involving C. difficile and MRSA continue to fall in Wales, most likely due to a greater awareness of antibiotic resistance and more effective measures to prevent the spread of these infections. However the elderly are still most likely to be affected by these diseases, due to their weaker immune systems.”

Dr. Ben Windsor-Shellard, Health Analysis and Life Events, Office for National Statistics

This bulletin presents the latest figures for deaths where either Clostridium difficile or Meticillin-resistant Staphylococcus aureus were mentioned or were identified as the underlying cause of death on death certificates. Figures are presented for Wales and are broken down by sex, age group and place of death. Comparisons are made between data for 2015, the latest year, and previously published data.

Figures are based on deaths registered in each calendar year rather than those occurring in each year. Since the majority of deaths involving Clostridium difficile or Meticillin-resistant Staphylococcus aureus registered in 2015 also occurred in the same year, registration delays are unlikely to affect our findings. Please see the section on registration delays for further information.

Clostridium difficile

Clostridium difficile (C. difficile) is a type of bacteria which is naturally present in the intestine of 2 in 3 children and 3 in 100 adults, but causes no harm to healthy people. This is because its growth is controlled by other bacteria in the body. However, certain antibiotics can interfere with the natural balance of the intestine by destroying the bacteria that usually prevent C.difficile from multiplying (Bupa, 2014). If this happens, C.difficile bacteria can grow to unusually high levels and produce toxins which attack the intestines. Some people affected by C. difficile show no symptoms; while others go on to have diarrhoea, high temperature and abdominal cramping. In extreme cases, it may cause potentially life-threatening inflammation of the bowel (NHS, 2016).

Meticillin-resistant Staphylococcus auereus

Meticillin-resistant Staphylococcus aureus (MRSA) is a type of Staphylococcus bacteria that is resistant to antibiotics known as beta-lactams. The MRSA figures presented here are a subset of the Staphylococcus aureus (S. aureus) figures. S. aureus bacteria can cause mild to life-threatening disease if there is an opportunity for it to enter the body through broken skin or a procedure requiring the use of an invasive medical device.

The concern about MRSA is in part due to the fact that it shows a higher degree of drug resistance than other types of S. aureus and also because it has become particularly associated with hospital acquired infections (Public Health Wales, 2011). There is also growing concern about community-acquired MRSA in some parts of the world, with studies (Herold et al. 1998; Salmenlinna S, Lyytikäinen O and Vuopio-Varkila J, 2002) suggesting that this type of MRSA can be found in otherwise healthy people with no previous contact with healthcare facilities or hospitalised persons.

Time coverage

In this bulletin figures for C. difficile are presented from 2001 onwards whereas figures on MRSA are presented from 1993 onwards. Since 2001, the Office for National Statistics (ONS) has been coding deaths in Wales using the Tenth Revision of the International Classification of Diseases (ICD-10; World Health Organisation). In this revision, there is a code for deaths involving C. difficile, something which was not available in the previous revision (ICD-9). For deaths involving MRSA, there are comparable codes in both revisions of the ICD, meaning that the time series for MRSA is longer. When we were testing the use of ICD-10, deaths in 1999 were dual coded using both revisions of the ICD. As such, this means that we also have figures on C. difficile for deaths registered in 1999. For further information, please see the Quality and methodology section.

In 2015, there were 108 deaths involving C. difficile in Wales, the lowest number of deaths since 2005. The number of male deaths fell from 52 in 2014 to 39 in 2015, while the number of female deaths rose somewhat from 59 in 2014 to 69 in 2015.

While C. difficile may contribute to a death, sometimes it directly causes death. In 2015, of the 108 death certificates mentioning C. difficile, 50 (46%) also identified it as the underlying cause. This represents a 19% increase from the previous year.

C. difficile caused more deaths in females than males in 2015. Among females, 37 deaths recorded C.difficile as the underlying cause. For males, 13 deaths recorded C. difficile as the underlying cause.

In 2015, there were 22 death certificates mentioning MRSA and 45 mentioning S. aureus (including those resistant to meticillin). A roughly equal proportion of deaths involving MRSA and S. aureus occurred in males and females.

The proportion of S. aureus deaths that are reported as meticillin-resistant tend to fluctuate annually. In 2015, approximately 49% of deaths involving S. aureus were identified as being resistant to meticillin. This is the first time the proportion of meticillin resistant S. aureus infections has been below 50% since 1995.

While MRSA and S. aureus infections may contribute to a death, sometimes they directly cause death. Approximately 27% (6 out of 22) of death certificates mentioning MRSA also recorded it as the underlying cause of death, while around 31% (14 out of 45) of those mentioning S. aureus recorded this as the underlying cause of death.

Age-standardised rates of deaths involving C. difficile rose sharply to their highest levels in the late-2000s. For all persons, the rate peaked in 2008 with 164.8 deaths per 1 million. Since this time, rates have progressively decreased to 34.3 deaths per 1 million in 2015. Since 2014, the all person rate of deaths involving C. difficile has not been significantly different to the lowest rate recorded in 1999.

For males, in 2015 the rate of death involving C. difficile was 31.7 deaths per 1 million. In recent years, the rate of death amongst males has improved, with the 2015 rate being significantly lower than that observed two years ago in 2013. In 2015, the rate of death involving C. difficile for males is the lowest observed since 2001.

For females, in 2015 the rate of death involving C. difficile was 37.4 deaths per 1 million. This rate is somewhat higher than that observed in 2014, where the rate was 31.2 deaths per 1 million. However, the difference between these two rates is not statistically significant.

The age-standardised rates presented here are for all persons (males and females combined). This is because the number of deaths in each year since the 2005 peak has fallen to the extent that there are no longer sufficient deaths to calculate robust sex-specific age-standardised rates.

Since the early 1990s, age-standardised rates of deaths involving MRSA and S. aureus rose to their highest levels in the mid-2000s. Rates of death involving MRSA and S. aureus both peaked in 2005 with 40.2 and 49.7 deaths per 1 million persons, respectively.

Rates of death involving MRSA are generally on a downward trend. In 2015, with 7.0 deaths per 1 million persons, the rate of death involving MRSA is significantly lower than its 2005 peak.

Rates of death involving S. aureus have fallen significantly since the 2005 peak to 14.4 deaths per 1 million persons in 2015. Since 2011 there has been relatively little change in rates of death involving S. aureus.

The majority of deaths involving C. difficile, MRSA, and S. aureus occur in those aged 85 years and over. This highlights the greater vulnerability of older people as they are likely to have relatively weaker immune systems compared with younger people.

Deaths involving C. difficile

In each period from 2001 to 2003, the age-specific rate for deaths mentioning C. difficile increased with age. In the latest period, 2013 to 2015, the age-specific death rate for all persons aged 85 years and over was 845.1 deaths per 1 million. For those aged below 55 years, the rate was just 1.0 death per 1 million persons.

Since the early 2000s, there have not been statistically significant changes in rates for people in age groups below 65 years. For those in age groups 65 years and over, there were statistically significant changes, with rates initially increasing before peaking in the late 2000s and then decreasing. On the whole, this pattern is true for both males and females.

For males, the highest recorded rate was in the period 2007 to 2009 for those aged 85 years and over (2,634.3 per million males). Since this time, the rate in 2013 to 2015 (965.5 deaths per 1 million males aged 85 and over) has dropped to the lowest level observed since 2003 to 2005.

For females, the highest recorded rate was in the period 2008 to 2010 for those aged 85 years and over (2,777.1 per million females). Despite a small increase since the previous period, the rate in 2013 to 2015 (783.5 deaths per 1 million females aged 85 and over) is significantly lower than when it peaked.

Deaths involving MRSA and S. aureus

Due to the small number of death certificates mentioning MRSA and S. aureus in each year, we have pooled data from 5-year periods in order to observe differences between the sexes and age groups.

In each 5-year period from 1993 to 1997, the age-specific rate for deaths mentioning MRSA and S. aureus increased with age and tended to be higher for males than females. Across time, and for both sexes, rates were lowest among those under the age of 55 years and highest among those aged 85 years and over. There has been no significant change in the age-specific MRSA death rates for males and females under 55 years and females aged 55 to 64 years over time. In other age groups, rates initially increased before falling to levels similar to those observed in the period 1993 to 1997.

For males, the highest recorded rates were in the period 2003 to 2007 for those aged 85 years and over. In 2011 to 2015, in the same age group, rates for both MRSA and S. aureus have both fallen by more than 50%. Specifically, for deaths involving MRSA there were 224.8 deaths per 1 million males. For S. aureus, there were 317.8 deaths per 1 million males.

For females, the highest recorded rates were in the period 2004 to 2008 for those aged 85 years and over. In 2011 to 2015, in the same age group, the rate for MRSA has fallen by 75%, whereas for deaths involving S.aureus the reduction is around 60%. Specifically, for deaths involving MRSA there were 73.4 deaths per 1 million females. For S. aureus, there were 139.1 deaths per 1 million females.

Deaths involving C. difficile

Deaths involving C. difficile accounted for 0.4% of all deaths registered in Wales in the period 2013 to 2015.

A breakdown by place of death shows that around 94% of deaths involving C.difficile in Wales occurred in NHS hospitals. These deaths represent 0.7% of deaths in NHS hospitals over the period. A similar pattern has been observed in each 3-year period from 2001 to 2003.

Although relatively small in comparison with NHS hospitals, care homes consistently had the second highest proportion of deaths involving C. difficile over time.

Deaths involving MRSA and S. aureus

Deaths involving S. aureus (including MRSA) accounted for 0.2% of all deaths registered in Wales in the period 2011 to 2015.

A breakdown by place of death shows that 93% of deaths involving S. aureus and 90% of MRSA deaths in Wales occurred in NHS hospitals. These figures represent 0.2% and 0.1% of all deaths in NHS hospitals over the period. A similar pattern has been observed in each 4-year period from 1993 to 1997 onwards.

Care homes had the second highest number and percentage of all deaths involving S. aureus and MRSA.

Incidence and mortality data for C. difficile, MRSA, and S. aureus infections in Wales are primarily used by Public Health Wales to highlight the burden of these infections and to monitor and evaluate intervention programs aimed at reducing this burden. These data are also used by local health boards and individual healthcare establishments.

In 2004, the Welsh government published its strategy for reducing healthcare associated infections in hospitals in Wales. In addition, the Welsh Healthcare Associated Infection Programme (WHAIP; Public Health Wales) conducts comprehensive surveillance of both C. difficile and MRSA. These surveillance programmes provides Health Boards with information about rates of various infections in their institutions, highlighting potential areas for investigation and action.

The information used to produce mortality statistics is based on the details collected when deaths are certified and registered. In Wales, deaths should be registered within five days of the death occurring, but there are situations where this isn’t possible. Deaths considered unexpected, accidental or suspicious will be referred to a coroner who may order a post-mortem or carry out a full inquest to ascertain the reasons for the death.

Statistics on deaths involving the infections described in this bulletin are presented based on the number of deaths registered in each calendar year, rather than the number of deaths that occurred. This method is used because there is a requirement for consistent and timely data, despite a potential limitation in data quality caused by registration delays.

In 2015, the average (median) number of days between date of death and death registration for deaths where any of the infections in this bulletin were mentioned on the death certificate or selected as the underlying cause was 4 days.

The majority of deaths mentioning C. difficile and those identifying it as the underlying cause were registered in 5 days (70% and 68% respectively) while 86% and 80% were registered within 30 days.

The majority of deaths mentioning MRSA and those identifying it as the underlying cause were registered in 5 days (73% and 66% respectively) while 86% and 100% were registered within 30 days.

The majority of deaths mentioning S. aureus and those identifying it as the underlying cause were registered in 5 days (80% and 79% respectively) while 89% and 93% were registered within 30 days.

For all of the infections described in this bulletin, practically all deaths which were registered in 2015 occurred during the same year. As such, registration delays are likely to have no impact on the trends reported in this bulletin.

BUPA (2014), Clostridium difficile infection [accessed 2 August 2016].

Herold B, Immergluck L, Maranan M, Lauderdale D, Gaskin R, Boyle-Vavra S, Leitch C, Daum R (1998) Community-acquired Methicillin-Resistant Staphylococcus aureus in children with no identified predisposing risk. Journal of the American Medical Association, 279(8).pp 593-598.

National Health Service (2016). Clostridium difficile [accessed 2 August 2016].

Public Health Wales (2016) Clostridium difficile and Staphylococcus aureus bacteraemia Surveillance Update [accessed 2 August 2016].

Public Health Wales (2011) Staphylococcus aureus (MRSA) [accessed 2 August 2016].

Salmenlinna S, Lyytikäinen O, and Vuopio-Varkila J (2002) Community-acquired Methicillin-Resistant Staphylococcus aureus, Finland. Emerging Infectious Disease Journal [e-journal], 8(6), June.

Welsh government (2004) Healthcare Associated Infections – A Strategy for Hospitals in Wales. [accessed 2 August 2016].

World Health Organisation (1992) International Classification of Diseases and Health Related Problems. World Health Organisation, Geneva.

World Health Organisation (1975) Manual of the International Classification of diseases, injuries, and causes of death. World Health Organisation, Geneva.

Statistics on mortality are derived from the information provided when deaths are certified and registered. Information about the underlying mortality data, including details on how the data is collected and coded are available in the mortality metadata. The Mortality Statistics and Deaths involving Clostridium difficile and MRSA in Wales Quality and Methodology Information documents contain important information on:

• the strengths and limitations of the data
• the quality of the output: including the accuracy of the data and how it compares with related data
• uses and users
• how the output was created

Data source

The information used in this bulletin is based on the details collected when deaths are certified and registered. All deaths are coded by ONS according to the International Classification of Diseases (ICD) produced by the World Health Organisation (WHO).

Since 1993, ONS has stored the text of death certificates on a database, along with all the ICD coding related to causes identified on the death certificate. The Tenth Revision of ICD (ICD-10) has been used to code deaths in Wales since 2001.

Since 1986, ONS has used the internationally recommended death certificate for neonatal deaths (infants under 28 days old). This certificate was only designed to record all conditions found at death. This means that neonates cannot be assigned an underlying cause of death. However, as the data were based on deaths where C. difficile, MRSA, or S. aureus were mentioned on the death certificate, neonates have been included. Neonatal deaths were extracted in the same way as described for post-neonatal deaths (see below).

Approach used in selecting deaths – C.difficile

The text on death certificates were used in combination with ICD-10 codes to identify those mentioning C. difficile.

In ICD-10 there is a specific code (A04.7) for ‘Enterocolitis due to Clostridium difficile’. While this code identifies the vast majority of deaths involving C. difficile, a small number of C. difficile-related deaths are not captured by this code alone.

In addition to extracting all deaths related to the specific A04.7 ICD-10 code, deaths mentioning other codes to which diseases including C. difficile could be coded were also extracted. The text of these death certificates was searched manually for mentions of Clostridium difficile, C. difficile or pseudomembranous colitis. The ICD-10 codes used to select deaths in order to search manually are shown in Box 1 in the accompanying data set.

Deaths registered in 1999 were coded to both ICD–9 and ICD–10 as part of a special study to compare the two ICD revisions.

Approach used in selecting deaths – MRSA and S. aureus

The text on death certificates were used in combination with ICD-10 codes to identify those mentioning MRSA and S. aureus in a two step process.

A number of infections are specifically related to S. aureus or other staphylococcal species. First, all deaths were extracted where any of these infections was mentioned on the death certificates. These deaths were extracted using the ICD-10 codes given in Box 1 in the accompanying data set. The text of these death certificates was then searched, both electronically and manually, to identify MRSA and S. aureus.

Conversely, some infections have different causative organisms and may be caused by Staphylococcus species or other pathogens. The second step therefore involves extracting all deaths which had these non-specific infections mentioned on the death certificate. The codes used to identify these infections are given in Box 2 in the accompanying data set. The text of these death certificates was then searched manually to identify MRSA and S. aureus.

Deaths with an underlying cause of S. aureus were identified by selecting those deaths with a mention of S. aureus that also had as the underlying cause one of the infections listed in Box 1 or Box 2. The same procedure was followed in order to identify deaths with MRSA as the underlying cause.