key: cord-0774022-dg3js04t
authors: Clements, Archie CA; Magalhães, Ricardo J Soares; Tatem, Andrew J; Paterson, David L; Riley, Thomas V
title: Clostridium difficile PCR ribotype 027: assessing the risks of further worldwide spread
date: 2010-06-30
journal: The Lancet Infectious Diseases
DOI: 10.1016/s1473-3099(10)70080-3
sha: 8fcb68a2b15d2cdc4008d5f2d4d248344d7f7530
doc_id: 774022
cord_uid: dg3js04t

Summary Highly virulent strains of Clostridium difficile have emerged since 2003, causing large outbreaks of severe, often fatal, colitis in North America and Europe. In 2008–10, virulent strains spread between continents, with the first reported cases of fluoroquinolone-resistant C difficile PCR ribotype 027 in three Asia-Pacific countries and Central America. We present a risk assessment framework for assessing risks of further worldwide spread of this pathogen. This framework first requires identification of potential vehicles of introduction, including international transfers of hospital patients, international tourism and migration, and trade in livestock, associated commodities, and foodstuffs. It then calls for assessment of the risks of pathogen release, of exposure of individuals if release happens, and of resulting outbreaks. Health departments in countries unaffected by outbreaks should assess the risk of introduction or reintroduction of C difficile PCR ribotype 027 using a structured risk-assessment approach.

Clostridium diffi cile is a major cause of diarrhoea in patients in hospital and long-term care facilities. 1,2 C diffi cile infection is through exposure to the organism or its spores via the faecal-oral route; the spores can persist in the environment for many months. Once infected, the person might remain asymptomatic or progress to C diffi cile disease. Infection and progression to disease are facilitated by use of antibiotics, which disrupt the normal fl ora and permit proliferation of the toxin-producing C diffi cile. A wide range of antibiotics have been implicated historically, including cephalosporins, penicillins, and clindamycin. [3] [4] [5] Infection ranges in severity; in its most severe form it can cause toxic megacolon with subsequent colonic perforation, peritonitis, shock, and death. Colectomy might be needed to avert perforation but is associated with high risk given the age and medical comorbidities of typical patients infected with C diffi cile. Infection is associated with hospitals and long-term care facilities because of frequent antibiotic use, widespread contamination of the patient's environment with spores, and the density of people at high risk (ie, elderly people with several comorbidities).

In the past two decades, the incidence of C diffi cile infection has increased in many industrialised countries, [6] [7] [8] [9] [10] [11] [12] [13] particularly among elderly people. 12 Groups previously thought to be low risk, including otherwise healthy people in the community without prior exposure to antibiotics, 14, 15 children, 16 and peripartum women, have also been aff ected. [17] [18] [19] Concurrent with an increase in incidence, an alarming increase in severity of infection has been reported, starting with reports of hospital outbreaks in Quebec, Canada, from 2003. These outbreaks were associated with high case-fatality rates 20, 21 and were estimated to have caused about 2000 deaths. 22 This happened at the same time as an increase in severity of infection in the USA, characterised by increases in reported C diffi cile infection-related admission to hospital, colectomies, and deaths, dated retrospectively from the mid-1990s. 13 ,23- 26 Muto and colleagues 8 noted a four-times increase in severe cases (resulting in colectomy or death) from 1999 to 2001 in a hospital outbreak in Pittsburgh, PA. A similar pattern of emergence has developed in Europe since 2005, with increasing incidence of infection 10, 27 and some hospital outbreaks with more severe cases and higher case-fatality rates than previously experienced. 28, 29 Outbreaks have been particularly severe in the UK, with a six-times increase in C diffi cile infectionrelated mortality from 1999 to 2006, 30,31 which preceded a stabilisation and substantial decline in incidence and mortality from 2007 to 2009. 32, 33 These North American and European outbreaks (fi gure 1) coincided with the emergence of a hypervirulent strain of C diffi cile, PCR ribotype 027/North American pulse-fi eld type 1, 34,35 that caused more severe colitis and higher mortality than other strains. 37,63-65 Increased virulence might be due to genetic mutations in a toxin regulator gene (tcdC) that cause hyperproduction of toxins A and B. 66, 67 The strain also produces a binary toxin associated with severe diarrhoea. 68, 69 Unlike isolates of C diffi cile PCR ribotype 027 obtained before 2001, isolates obtained during the North American and European epidemics were resistant to fl uoroquinolones and genetically closely related. [34] [35] [36] 64, 70 So far, continents other than North America and Europe have been spared outbreaks of C diffi cile PCR ribotype 027 infection, and evidence suggests a decline in the incidence of infection associated with this ribotype in the UK 32 and the Netherlands. 71 However, alarmingly in 2008-10, the fi rst cases of C diffi cile PCR ribotype 027 infections were reported in Western Australia, 57 South Korea, 58 Hong Kong, 59 and Costa Rica, 50 showing the potential of this organism to spread between continents beyond its current north Atlantic domain.

The emergence of C diffi cile PCR ribotype 027 is of worldwide concern, both for aff ected and unaff ected countries. It is uncertain if the failure to detect the strain in many countries means it is truly absent, because molecular genotyping is rarely used. Many industrialised countries now rely on enzyme-linked immunoassays for diagnosis, which do not identify specifi c strains, 72 whereas most developing countries have no C diffi cile surveillance Review or do routine diagnostic investigation. However, these countries must identify this strain if, where, and when it emerges to avoid the large epidemics of North America and parts of Europe. We review the types and sources of evidence that need to be assembled to understand the risks of further worldwide emergence of this and other international epidemic strains of C diffi cile.

Risk analysis, comprising risk management, assessment, and communication, is an emerging branch of epidemiology that provides a structured, evidence-based, approach to addressing health risks. Approaches are framed by international standards such as those of the Food and Agriculture Organization/World Health Organization Codex Alimentarius for microbiological risk assessment 73 or the Offi ce International des Epizooties (OIE) system, 74 primarily aimed at international movement of veterinary and zoonotic pathogens. Risk assessment (the technical component of risk analysis) is fundamentally based on the clear defi nition of a risk question. Using the OIE framework as an example, risk assessment comprises four consecutive analytic components: release assessment, exposure assessment, consequence assessment, and risk estimation. 74 During each of the fi rst three, all available evidence from published work and expert opinion is reviewed and organised on the basis of a diagrammatic construction of risk pathways. The fi nal risk estimation involves the combination of the results of the preceding three stages to produce an overall estimate of risk.

Quantitative risk assessment uses a probabilistic risk model to derive numerical expressions of risk and associated uncertainties, whereas qualitative risk assessment permits ranking or categorisation of risk. There are many reported applications of quantitative risk assessment to veterinary, zoonotic, and food-borne diseases, including Alban and colleagues 75 who investigated risk of human salmonellosis and campylo bacteriosis associated with consumption of pork products in Denmark, Bemrah and colleagues 76 who investigated risk of listeriosis from consumption of unpasteurised cheese, and Bronsvoort and colleagues 77 who investigated risk of importation of classic swine fever into Denmark. However, there are few examples for infectious diseases primarily involving transmission between people, and none reported for C diffi cile infection.

For C diffi cile infection, risk is likely to depend on the infection history of the country of interest. If C diffi cile PCR ribotype 027 is not known to be present (as in most countries in the Asia-Pacifi c region, Africa, and Latin America), the risk question could focus on the likelihood of introduction through specifi ed, hazardous, movements across boundaries. Alternatively, the risk question could consider endogenous emergence through a set of hazardous biological mechanisms, such as patterns of use of specifi c antibiotics. If C diffi cile PCR ribotype 027 has been detected but has not caused outbreaks (as in Figure 1 : Countries* where Clostridium diffi cile PCR ribotype 027 has been reported Sources of information include reports from the USA 8,34 and Canada, 35 reporting hospital outbreaks since 2001; the UK, 29,36 the Netherlands, [37] [38] [39] Belgium, 40 and Ireland, 41 reporting hospital outbreaks since 2005; France, 28, 42 Switzerland, 43 and Luxembourg, 44 reporting hospital outbreaks since 2006; Germany, [45] [46] [47] reporting hospital outbreaks since 2007; and Austria 27, 48 and Denmark, 44, 45, 49 reporting hospital outbreaks since 2008. Sporadic or imported cases of infection caused by C diffi cile PCR ribotype 027 have also been reported from Costa Rica, 50 Finland, 51, 52 Hungary, 45, 53 Italy, 54 Norway, 55 Poland, 44, 45 Spain, 45 Sweden, 56 Western Australia, 57 South Korea, 58 and Hong Kong. 59 The earliest known isolate from the Netherlands was collected in 2002, 37 but-like earlier strains of PCR ribotype 027 in North America, isolates from Japan, 60,61 and the majority of recent isolates from Sweden 56,62 -it was susceptible to fl uoroquinolones and is thought a historic strain not associated with the recent international epidemic. *And states or provinces of the USA, Canada, and Australia.

Outbreaks reported Sporadic or imported cases reported PCR ribotype 027 reported (not fluoroquinolone resistant) PCR ribotype 027 not reported Review Australia, Korea, Hong Kong, and parts of Europe), the risk question could focus on the likelihood of reintroduction or an outbreak due to endogenous transmission. If C diffi cile PCR ribotype 027 is present and outbreaks have happened (as in North America and parts of western Europe), the assessment of risk could focus on the likelihood of recurrence, the eff ect of a particular intervention (or no intervention) on the size or frequency of outbreaks, or of previously unaff ected groups in the population becoming aff ected. We focus on the risk of introduction, or reintroduction, of C diffi cile PCR ribotype 027 to countries that have not experienced epidemics associated with this strain.

The movements of people, animals, vectors, and inanimate objects across international boundaries has spread many infectious diseases, including infl uenza, 78 severe acute respiratory syndrome, 79 dengue, 80 chikungunya, 81,82 and malaria. 83 However, identifi cation of imported C diffi cile PCR ribotype 027 is probably much more diffi cult than for these infections because screening of travellers is not done and outbreaks associated with importation of this strain are likely to happen months or years after importation, leading to delayed identifi cation of the incursion.

For importation of the C diffi cile epidemic strain, a major hazard of interest is international transfer of hospital patients. There is evidence that asymptomatic carriage is common among patients admitted to hospital, and these carriers can act as a source of transmission in settings where C diffi cile PCR ribotype 027 is present. 84, 85 Theoretically, either a diarrhoeic or asymptomatically infected patient transferred between health-care institutions (including those in diff erent countries) could act as a source of this strain. The fi rst documented case of infection due to PCR ribotype 027 in Ireland was in a patient transferred from a hospital in the UK, 41 and the only reported case in Western Australia was in a patient transferred from the USA. 57 Other anecdotal reports also suggest this as a possible (although unproven) means of international spread. For example, transfer of patients from Belgium was investigated as a potential source of introduction of C diffi cile PCR ribotype 027 to France in 2006 42 and the index case of infection with this strain in Switzerland had previously been admitted to hospital in Spain. 43 Another potential hazard is movement of people from the community across boundaries (eg, tourists, business travellers, international migrants, and military personnel). A tourist from the UK was reported to have had pseudomembranous colitis caused by C diffi cile PCR ribotype 027 while on holiday in Austria; endogenous cases were subsequently reported in that country. 45 A person with community-acquired, fl uoroquinolone-susceptible, C diffi cile PCR ribotype 027 infection in Sweden had previously travelled to Italy, 56 suggesting (but not confi rming) recreational travel as a potential source. However, asymptomatic carriage is less studied in the community than in hospital patients and the role of asymptomatic carriers in the movement of C diffi cile strains between jurisdictions is unknown. The often quoted prevalence of asymptomatic C diffi cile carriage in healthy adults, 2-3%, comes from a 1981 report; 86 however, recent evidence of an increase in incidence of community-acquired cases in some countries warrants studies to update estimates of prevalence of asymptomatic carriage in the community. The role of antibiotic use in the community as a factor promoting carriage of C diffi cile is also poorly understood. In a French study of people prescribed antibiotics in the community, 87 one of 262 had detectable pretreatment colonisation and seven had detectable post-treatment infection with toxigenic strains of C diffi cile.

Although animals have not previously been implicated in any known events of C diffi cile crossing boundaries, they can be symptomatically or asymptomatically infected. C diffi cile is recognised as an important cause of enteric disease in piglets [88] [89] [90] [91] and horses. 92, 93 Identical strains of C diffi cile have been isolated in people and dogs, horses, and pigs. [94] [95] [96] [97] [98] These fi ndings also pertain to C diffi cile PCR ribotype 027: studies in North America isolated this strain from calves, 99 a dog, 98,100 and a horse with colitis. 101 Toxigenic strains of C diffi cile, including PCR ribotype 027, have been isolated from commercially available meat. 102, 103 Recent studies in Arizona, USA, and four provinces of Canada, found a high proportion of retail meat samples containing C diffi cile PCR ribotype 027. 104, 105 An unspecifi ed toxigenic C diffi cile strain has been isolated from meat for consumption by pets. 106 Isolation of toxigenic strains of C diffi cile from salad in the UK 107 suggests that the bacterium could be widely distributed in a range of human foodstuff s. 108 These studies combined show a potential for transmission between animals and people (either directly or via the food chain), and international spread of toxigenic strains of C diffi cile via movement or trade in livestock, companion animals, meat, and other foodstuff s is therefore possible.

Assuming individuals with known infection are treated in the country of origin or prevented from entering the destination country, the probability of release of the pathogen is dependent on the disease status of the country of origin, the proportion of individuals screened as part of disease surveillance in the country of origin, the performance (ie, sensitivity and specifi city) of diagnostic tests used in screening, the frequency of movement between countries, and the proportion of individuals that are screened (and performance of screening tests) on arrival in the destination country.

Several countries have reported infections with C diffi cile PCR ribotype 027 (fi gure 1), but the disease status of all other countries is unknown because of a lack of routine surveillance and, in many countries, a lack of Review capacity or resources for diagnostic testing, including genotyping. Clearly, risk of release depends on surveillance practices in both the country of origin and the importing country because the eff ectiveness of surveillance establishes the probability of infected individuals moving between the originating and importing countries without being detected, and the bacterium being contained.

Information on C diffi cile surveillance can be obtained for most countries aff ected by outbreaks of C diffi cile PCR ribotype 027 from published questionnaire studies of hospital laboratory practices. A study in eight European countries found that the reasons for C diffi cile testing (eg, physician request vs routine screening for samples fulfi lling preset criteria such as age of patient and stool consistency) and the tests used, varied widely between laboratories and countries. 109 Findings were similar in studies in Australia, 110 the UK, 11, 111 Ireland, 112 Canada, 113 and the USA. 7, 114 In some European countries, national laboratory surveillance has been instigated in response to emergence of C diffi cile PCR ribotype 027. A national laboratory network was set up in France to characterise strains of C diffi cile. 28 In Belgium, laboratorybased surveillance of clusters of cases of C diffi cile infection and prospective hospital-based surveillance have been set up, fi nding PCR ribotype 027 strains in 150 (52·1%) of 288 isolates. 115 A national laboratory surveillance system was also set up in the Netherlands, fi nding that 218 (25·3%) of 863 cases were caused by PCR ribotype 027 in 2005-06. 37 Additionally, laws and mandates relating to diagnosis and reporting of C diffi cile can be reviewed to understand surveillance practices. In the UK, laboratory surveillance was made mandatory by the Health Protection Agency (HPA) in January, 2004. 111, 116 All stool specimens from diarrhoeic patients older than 65 years were tested for C diffi cile toxins A and B, with the number of C diffi cile infections in each hospital required to be reported to the HPA; 117 in 2007, mandatory reporting was extended to include individuals older than 2 years. 118 Isolates from hospital outbreaks and a sample of other isolates are sent to a national reference laboratory for genetic typing. 119 Some provinces in Canada have mandatory reporting of C diffi cile infections, 120,121 as do a few US states, and some countries of the European Union. 45 Continent-wide surveillance studies in Europe are under development, 45 but surveillance in the USA and Canada is hampered by the lack of a nationwide approach.

Risk of release is proportional to the frequency of movement of individuals between countries. This can be estimated from various sources that are illustrated here by examples from Australia. All people visiting Australia, apart from citizens of Australia and New Zealand, require an entry visa from the Department of Immigration and Citizenship and, for an assessment of risk focusing on international spread via tourists or business visitors, annual numbers of visitors from specifi c countries of origin can be estimated by the number of off shore visas granted (table 1) . Alternatively, the frequency of movement of individuals can be estimated by the carrying capacity of international airlines on specifi c international routes (fi gure 2). For the assessment of risk focusing on international transfers of patients, numbers of patients entering from aff ected countries can be obtained from medical retrieval companies. Australia has strict regulations regarding the species of domestic animals entering and countries from which animals can be imported, and a risk assessment focusing on animal sources could make use of quarantine records to estimate the number of domestic animals entering by country of origin (table 2) . Importation of livestock is highly regulated in Australia and this is an unlikely source of C diffi cile PCR ribotype 027, but for other countries livestock trade data can be used to establish the number of animals entering. Similarly, for Australia and other countries, data on trade in meat products could also be obtained (eg, from the UN Commodity Trade Statistics Database).

Exposure to C diffi cile, leading to transmission, can be via several pathways. In hospitals, workers' hands and the environment are major modes of transmission; 85, [124] [125] [126] aerial dissemination is also possible. 127 Transmission is also increasing in the community and recent studies have raised the possibility of additional means of transmission, such as via the food chain 102 or contact with companion animals or livestock.

Establishing the risk of exposure to C diffi cile requires information on contact rates between infected carriers and individuals free of infection; the contact pattern, either via direct contact or indirect contact with a healthcare worker or contaminated environment; the duration of shedding by asymptomatic individuals with the infection; the amount of environmental contamination Observational studies to establish values for variables such as contact rates between infected and susceptible individuals, duration of shedding and survival of pathogens, and eff ect of intervention strategies are diffi cult and expensive to do, and suff er from issues such as poor generalisability, inadequate statistical power, and many types of inherent bias. Therefore, many investigations of infectious-disease transmission use mathematical models, which are built using multiple sources of available evidence to estimate plausible values for many of these parameters. Uncertainties surrounding these estimates are often captured by use of a stochastic Monte Carlo simulation approach. Only two publications, 128,129 both by the same group, present mathematical models for C diffi cile transmission and focus exclusively on the health-care setting, using a single ward-based model. Exposure assessment is likely to be the most challenging aspect of C diffi cile risk assessment and substantial future research is needed to understand the transmission dynamics of this organism.

The consequences of transmission, including infections and outbreaks, depend on the risk profi le of the population into which the pathogen has been introduced. Antibiotic use is the main factor determining susceptibility to infection in an individual exposed to C diffi cile and data on levels of use of diff erent types of antibiotic will probably provide the most important source of information for assessing the risk of infections and outbreaks. Availability of antimicrobial drugs varies widely between countries, with those countries that do not have good systems for regulating the use of antimicrobial drugs (particularly developing countries) also being the countries with the poorest systems for monitoring use and associated disease risks.

Studies have shown variation in levels of antibiotic prescribing between countries 130 and over time. 131 Goossens and colleagues 132 investigated levels of antibiotic prescribing in the community in 26 European countries, with estimates ranging from 10·0 defi ned daily doses per 1000 people in the Netherlands to 32·2 defi ned daily doses per 1000 people in France (although diff erent assessment methods were used in each country), and varying by season, with a marked winter peak. Patrick and colleagues 130 also showed seasonal variation (characterised by a winter peak) in antibiotic prescribing in Denmark and British Columbia, Canada. Interestingly, seasonal variation in rates of C diffi cile infection, with a winter peak, have also been reported in the USA. 6 Fluoroquinolone use has been identifi ed as a major risk factor for infection in settings where C diffi cile PCR ribotype 027 is present, 8, 21, 35, 65, 133, 134 and increasing fl uoroquinolone use in hospitals has been shown to precede outbreaks of infection associated with this strain, 8 possibly because fl uoroquinolone resistance gives the strain a selective advantage. 34 Linder and colleagues 131 reported on fl uoroquinolone prescribing patterns in the USA, using data from national surveys of emergency department and outpatient clinic visits. They found a rapid (three times) increase in fl uoro quinolone prescriptions from 1995 to 2002, and that fl uoro quinolones had become the most common class of antibiotics prescribed to adults in 2002. Patrick and colleagues 130 also showed an increase in fl uoro quinolone prescribing in British Columbia from 1997 to 2000. Clindamycin was the predominant risk factor for infection in a study by McFarland and colleagues 135 and some recent isolates of C diffi cile PCR ribotype 027 are resistant to this antibiotic. 43, 136 Monitoring of veterinary antibiotic use, potentially including manufacturing, sales, distribution, prescribing, and administration data, has been highlighted as an area of importance for risk assessment of emerging antibiotic resistance in human pathogens. 137, 138 In livestock, prolonged oral administration of broad-spectrum antibiotics and inadvertent under dosing increase the risk of emergence of antibiotic resistance that can then be passed to human pathogens. 139 Comprehensive veterinary prescription surveillance systems exist in the Netherlands and Nordic countries (Denmark, Finland, Norway, and Sweden). However, there is a lack of comprehensive, systematically collected, or readily available veterinary prescribing data in the USA 137 and other countries 138 and a lack of consensus on the optimum approach to surveillance of antibiotic use in animals. 140 Other established risk factors for C diffi cile infection are advanced age and presence of comorbidities, 4, 8, 21, 135, [141] [142] [143] [144] [145] current or previous admission to hospital, 4, 21, 133, 135, 141, 146, 147 and sharing an environment with other people infected with C diffi cile. 4 

Pépin and colleagues 21, 148 give a compelling theory of the evolution of the international C diffi cile PCR ribotype 027: a new, fl uoroquinolone-resistant, hyper-virulent strain 149 causing more severe diarrhoea and, therefore, more intense environmental contamination, was circulating at low levels across a wide geographical region 150 until widespread, increasing, use of fl uoroquinolones 131 in highly susceptible populations (characterised by increasing age and frequency of comorbidities, located in underresourced, overcrowded, health-care facilities) precipitated a rapidly emerging epidemic that spread internationally. Many of the factors that precipitated the epidemics in North America and Europe are present in countries without known circulation of C diffi cile PCR ribotype 027, such as hospital overcrowding and understaffi ng, high levels of antibiotic (particularly fl uoroquinolone) use, and an ageing population of hospital patients with increasing numbers and severity of comorbidities. Additionally, international travel is increasing and there is a high volume of international travel between aff ected and unaff ected countries. It is highly probable that C diffi cile PCR ribotype 027 already has been or will be introduced undetected into countries not aff ected at present, via hospital transfers, asymptomatic carriers, or other vehicles, due to a lack of screening and the frequent movement of people and commodities across boundaries. If C diffi cile PCR ribotype 027 is introduced into an unaff ected country or if a highly pathogenic strain emerges, it is improbable with current surveillance that they would be identifi ed until a large outbreak of severe C diffi cile infection happens, leading to otherwise preventable illness, colectomies, deaths, and huge costs to health services. Now is the time to act to assemble an evidence base for reducing the risk and consequences of future outbreaks in unaff ected countries.

ACAC had the original idea for the Review, searched the published work, created fi gures and tables, and drafted the paper. RJSM oversaw the risk assessment component and contributed to the drafts. AJT provided fi gures and contributed to the drafts. DLP oversaw the epidemiological description of Clostridium diffi cile infection and contributed to the drafts. TVR oversaw the microbiological description of C diffi cile and contributed to the drafts. All authors approved the fi nal version.

We declare that we have no confl icts of interest.

Data for this Review were obtained from publications identifi ed by a systematic search of PubMed, focusing on those published from January, 2001, to March, 2010. Search terms included "Clostridium diffi cile", "ribotype 027", "NAP 1", "international epidemic strain", "risk", and "surveillance". Abstracts of English, French, and Spanish language papers were read and considered for inclusion, although only English language papers were selected for the fi nal review. Secondary, manual, searches of the cited references of these articles were done and relevant articles were included, some of which were published before 2001. The last search of published work was done on March 17, 2010.

Clostridium diffi cile and the aetiology of pseudomembranous colitis

Role of Clostridium diffi cile in antibiotic-associated pseudomembranous colitis

Antibiotics and hospital-acquired Clostridium diffi cile-associated diarrhoea: a systematic review

The role of physical proximity in nosocomial diarrhea

Risk factors for Clostridium diffi cile carriage and C diffi cile-associated diarrhea in a cohort of hospitalized patients

Secular trends in hospital-acquired Clostridium diffi cile disease in the United States

Clostridium diffi cile-associated disease in Oregon: increasing incidence and hospital-level risk factors

A large outbreak of Clostridium diffi cile-associated disease with an unexpected proportion of deaths and colectomies at a teaching hospital following increased fl uoroquinolone use

Epidemic Clostridium diffi cile

Clostridium diffi cile in discharged inpatients

Incidence and impact of Clostridium diffi cile infection in the UK, 1993-1996

Clostridium diffi cile infection in patients discharged from US short-stay hospitals

Increasing prevalence and severity of Clostridium diffi cile colitis in hospitalized patients in the United States

Severe Clostridium diffi cile-associated disease in populations previously at low riskfour states

Changing epidemiology of Clostridium diffi cile-associated disease in children

Peripartum Clostridium diffi cile infection: case series and review of the literature

Recurrent infection with epidemic Clostridium diffi cile in a peripartum woman whose infant was asymptomatically colonized with the same strain

Clostridium diffi cileassociated diarrhea: an emerging threat to pregnant women

Clostridium diffi cile-associated diarrhea in a region of Quebec from 1991 to 2003: a changing pattern of disease severity

Emergence of fl uoroquinolones as the predominant risk factor for Clostridium diffi cile-associated diarrhea: a cohort study during an epidemic in Quebec

C diffi cile may have killed 2000 in Quebec: study

Clostridium diffi cile colitis: an increasingly aggressive iatrogenic disease?

Increase in deaths related to enterocolitis due to Clostridium diffi cile in the United States

Increase in adult Clostridium diffi cile-related hospitalizations and case-fatality rate

Increase in Clostridium diffi cile-related mortality rates

First cases of Clostridium diffi cile PCR ribotype 027 acquired in Austria

Emergence of Clostridium diffi cile toxinotype III, PCR-ribotype 027-associated disease

Outbreak of Clostridium diffi cile infection in a hospital in south east England

Offi ce for National Statistics. Deaths involving Clostridium diffi cile: England and Wales

Offi ce for National Statistics. Deaths involving Clostridium diffi cile: England and Wales

Clostridium diffi cile ribotyping network for England and Northern Ireland 2008/09 report. London: Health Protection Agency

) and fi nancial year (2007/2008) Clostridium diffi cile data derived from Mandatory Surveillance

An epidemic, toxin gene-variant strain of Clostridium diffi cile

A predominantly clonal multiinstitutional outbreak of Clostridium diffi cile-associated diarrhea with high morbidity and mortality

Outbreak of Clostridium diffi cile infection in an English hospital linked to hypertoxin-producing strains in Canada and the US

Spread and epidemiology of Clostridium diffi cile polymerase chain reaction ribotype 027/toxinotype III in The Netherlands

Isolation of Clostridium diffi cile ribotype 027, toxinotype III in the Netherlands after increase in C diffi cile-associated diarrhoea

Clostridium diffi cile ribotype 027, toxinotype III, the Netherlands

First isolation of Clostridium diffi cile PCR ribotype 027, toxinotype III in Belgium

First isolation and report of clusters of Clostridium diffi cile PCR 027 cases in Ireland

First cluster of C diffi cile toxinotype III, PCR-ribotype 027 associated disease in France: preliminary report

First cluster of clindamycin-resistant Clostridium diffi cile PCR ribotype 027 in Switzerland

Update of Clostridium diffi cile-associated disease due to PCR ribotype 027 in Europe

Update of Clostridium diffi cile infection due to PCR ribotype 027 in Europe

Confi rmed cases and report of clusters of severe infections due to Clostridium diffi cile PCR ribotype 027 in Germany

A case of Clostridium diffi cile-associated disease due to the highly virulent clone of Clostridium diffi cile PCR ribotype 027

Outbreak of Clostridium diffi cile 027 infection in

Emergence of Clostridium diffi cile NAP1 in Latin America

Clostridium diffi cile ribotype 027-associated disease in children with norovirus infection

First isolation of Clostridium diffi cile PCR ribotype 027 in Finland

First isolation of Clostridium diffi cile PCR ribotype 027 from a patient with severe persistent diarrhoea in Hungary

First report of hypervirulent strains polymerase chain reaction ribotypes 027 and 078 causing severe Clostridium diffi cile infection in Italy

First confi rmed cases of Clostridium diffi cile PCR ribotype 027 in Norway

Community acquired Clostridium diffi cile infection due to a moxifl oxacin susceptible ribotype 027 strain

First Australian isolation of epidemic Clostridium diffi cile PCR ribotype 027

The fi rst case of antibioticassociated colitis by Clostridium diffi cile PCR ribotype 027 in Korea

Clostridium diffi cile ribotype 027 arrives in Hong Kong

First isolation of Clostridium diffi cile 027 in Japan

Molecular analysis of Clostridium diffi cile at a university teaching hospital in Japan: a shift in the predominant type over a fi ve-year period

Community acquired Clostridium diffi cile infection due to a moxifl oxacin susceptible ribotype 027 strain

Health care-associated Clostridium diffi cile infection in Canada: patient age and infecting strain type are highly predictive of severe outcome and mortality

Prospective study of Clostridium diffi cile infections in Europe with phenotypic and genotypic characterisation of the isolates

Clostridium diffi cile infections in a Canadian tertiary care hospital before and during a regional epidemic associated with the BI/NAP1/027 strain

Increased sporulation rate of epidemic Clostridium diffi cile Type 027/NAP1

Toxin production by an emerging strain of Clostridium diffi cile associated with outbreaks of severe disease in North America and Europe

Clinical features of Clostridium diffi cile-associated diarrhoea due to binary toxin (actin-specifi c ADP-ribosyltransferase)-producing strains

Clinical features of Clostridium diffi cile-associated infections and molecular characterization of strains: results of a retrospective study

In vitro susceptibility of Clostridium diffi cile clinical isolates from a multi-institutional outbreak in Southern Quebec

Decrease of hypervirulent Clostridium diffi cile PCR ribotype 027 in the Netherlands

Epidemic Clostridium diffi cile

Principles and guidelines for the conduct of microbiological risk assessment. Geneva: World Health Organization

Antimicrobial resistance: risk analysis methodology for the potential impact on public health of antimicrobial resistant bacteria of animal origin

A human health risk assessment for macrolide-resistant Campylobacter associated with the use of macrolides in Danish pig production

Quantitative risk assessment of human listeriosis from consumption of soft cheese made from raw milk

Quantitative assessment of the likelihood of the introduction of classical swine fever virus into the Danish swine population

A variety of respiratory viruses found in symptomatic travellers returning from countries with ongoing spread of the new infl uenza A(H1N1)v virus strain

Experience of severe acute respiratory syndrome in singapore: importation of cases, and defense strategies at the airport

Multiple outbreaks of dengue serotype 2 in north Queensland

Chikungunya virus infection in travellers to Australia

Chikungunya infection in a French traveller returning from the Maldives

An outbreak of Plasmodium vivax malaria in Far North Queensland

Asymptomatic carriers are a potential source for transmission of epidemic and nonepidemic Clostridium diffi cile strains among long-term care facility residents

Clostridium diffi cile in a geriatric unit: a prospective epidemiological study employing a novel S-layer typing method

Isolation rates and toxigenic potential of Clostridium diffi cile isolates from various patient populations

Antibiotic-associated diarrhoea and Clostridium diffi cile in the community

Infection of neonatal swine with Clostridium diffi cile

The emergence of Clostridium diffi cile as a pathogen of food animals

Typhlocolitis caused by Clostridium diffi cile in suckling piglets

A survey of agents associated with neonatal diarrhea in Iowa swine including Clostridium diffi cile and porcine reproductive and respiratory syndrome virus

Clostridium diffi cile: prevalence in horses and environment, and antimicrobial susceptibility

Molecular analysis of Clostridium diffi cile isolates recovered from horses with diarrhea

Evaluation of Clostridium diffi cile in dogs and the household environment

Emergence of Clostridium diffi cile infection due to a new hypervirulent strain, polymerase chain reaction ribotype 078

PCR ribotyping of Clostridium diffi cile isolates originating from human and animal sources

Prevalence of PCR ribotypes among Clostridium diffi cile isolates from pigs, calves, and other species

Prevalence of zoonotic agents in dogs visiting hospitalized people in Ontario: implications for infection control

Clostridium diffi cile PCR ribotypes in calves

Epidemic Clostridium diffi cile strain in hospital visitation dog

Equine colitis X associated with infection by Clostridium diffi cile NAP1/027

Clostridium diffi cile in retail ground meat

Possible seasonality of Clostridium diffi cile in retail meat

Clostridium diffi cile in retail meat products, USA

Detection and enumeration of Clostridium diffi cile spores in retail beef and pork

Bacteriological evaluation of commercial canine and feline raw diets

Clostridium diffi cile in ready-to-eat salads

Clostridium diffi cile in food-innocent bystander or serious threat?

A European survey of diagnostic methods and testing protocols for Clostridium diffi cile

More on Clostridium diff cileassociated diarrhoea in Australia

Clostridium diffi cile: a questionnaire survey of laboratory practice in England, Wales, and Northern Ireland

Laboratory diagnosis of Clostridium diffi cile-associated disease in the Republic of Ireland: a survey of Irish microbiology laboratories

Survey of incidence of Clostridium diffi cile infection in Canadian hospitals and diagnostic approaches

Varying rates of Clostridium diffi cile-associated diarrhea at prevention epicenter hospitals

Epidemiology of Clostridium diffi cile toxinotype III, PCR-ribotype 027 associated disease in Belgium

Surveillance of Clostridium diffi cile associated disease: report of the national standards group

Report to the Department of Health

Letter from the Chief Medical Offi cer and Chief Nursing Offi cer: infection caused by Clostridium diffi cile. London: Department of Health

Epidemiology, pathogenesis, and management of Clostridium diffi cile infection

Ontario's hospitals surpass those of Quebec in C diffi cile rates

Need for national surveillance for hospital infections

Canberra: Australian Government

Climatic similarity and biological exchange in the worldwide airline transportation network

Molecular epidemiology of endemic Clostridium diffi cile infection and the signifi cance of subtypes of the United Kingdom epidemic strain (PCR ribotype 1)

Prospective evaluation of environmental contamination by Clostridium diffi cile in isolation side rooms

Clinical and molecular epidemiology of sporadic and clustered cases of nosocomial Clostridium diffi cile diarrhea

Aerial dissemination of Clostridium diffi cile spores

Mathematical modeling of Clostridium diffi cile infection

Spatio-temporal stochastic modelling of Clostridium diffi cile

Per capita antibiotic consumption: how does a North American jurisdiction compare with Europe?

Fluoroquinolone prescribing in the United States: 1995 to 2002

Outpatient antibiotic use in Europe and association with resistance: a crossnational database study

A hospital outbreak of diarrhea due to an emerging epidemic strain of Clostridium diffi cile

Fluoroquinolone use and Clostridium diffi cile-associated diarrhea

Fluoroquinolone use and risk factors for Clostridium diffi cileassociated disease within a Veterans Administration health care system

Clindamycin-resistant clone of Clostridium diffi cile PCR Ribotype 027

Introduction to animal antimicrobial use data collection in the United States: methodological options

Overview of issues pertaining to the manufacture, distribution, and use of antimicrobials in animals and other information relevant to animal antimicrobial use data collection in the United States

Guidelines for prudent use of antimicrobials and their implications on antibiotic usage in veterinary medicine

Deliberations of an Advisory Committee regarding priorities, sources, and methods for collecting animal antimicrobial use data in the United States

Clostridium diffi cileassociated disease in a setting of endemicity: identifi cation of novel risk factors

Moxifl oxacin therapy as a risk factor for Clostridium diffi cile-associated disease during an outbreak: attempts to control a new epidemic strain

Risk factors and mortality associated with Clostridium diffi cile-associated diarrhoea at a VA hospital

Evaluation of Clostridium diffi cile-associated disease pressure as a risk factor for C diffi cileassociated disease

Underlying disease severity as a major risk factor for nosocomial Clostridium diffi cile diarrhea

Clostridium diffi cile among hospitalized patients receiving antibiotics: a casecontrol study

Risk factors for acquisition of Clostridium diffi cile-associated diarrhea among outpatients at a cancer hospital

Mortality attributable to nosocomial Clostridium diffi cile-associated disease during an epidemic caused by a hypervirulent strain in Quebec

The challenges posed by reemerging Clostridium diffi cile infection

Molecular analysis of Clostridium diffi cile PCR ribotype 027 isolates from eastern and western Canada