Relationship of pulsed-field profiles with key phage types of Salmonella enterica serotype Enteritidis in Europe: results of an international multi-centre study.

Salmonella is one of the most common causes of foodborne infection in Europe with Salmonella enterica serovar Enteritidis (S. Enteritidis) being the most commonly identified serovar. The predominant phage type for S. Enteritidis is phage type (PT) 4, although PT 8 has increased in incidence. Within these phage types, pulsed-field gel electrophoresis (PFGE) provides a method of further subdivision. The international project, Salm-gene, was established in 2001 to develop a database of PFGE profiles within nine European countries and to establish criteria for real-time pattern recognition. It uses DNA fingerprints of salmonellas to investigate outbreaks and to evaluate trends and emerging issues of foodborne infection within Europe. The Salm-gene database contains details of about 11 700 S. Enteritidis isolates, demonstrating more than 65 unique PFGE profiles. The clonal nature of S. Enteritidis is evidenced by the high similarity and distribution of PFGE profiles. Over 56% (6603/11 716) of the submitted isolates of several different phage types were profile SENTXB.0001, although this profile is most closely associated with PT 4. The next most common profiles, SENTXB.0002 and SENTXB.0005, were closely associated with PT 8 and PT 21 respectively. Studies to investigate the relationship of profile types with outbreaks and possible vehicles of infection suggest that the incidence of PFGE profile SENTXB.0002, and thus PT 8, in some countries may be due to importation of foods or food production animals from Eastern Europe, where PT 8 is amongst the most frequently identified phage types. Collation of subtyping data, especially in the commonly recognized phage types, is necessary in order to evaluate trends and emerging issues in salmonella infection.

Distribution of molecular subtypes within Salmonella enterica serotype Enteritidis phage type 4 and S. Typhimurium definitive phage type 104 in nine European countries, 2000-2004: results of an international multi-centre study.

This study investigates the distribution of pulsed-field gel electrophoresis (PFGE) profiles within Salmonella enterica serotype Enteritidis phage type (PT) 4 and S. Typhimurium definitive phage type (DT) 104, from cases of human infection in nine European countries from 2000 to 2004. Isolates were subtyped using standardized methods and gel images submitted by each participating country to the coordinating centre (Health Protection Agency Centre for Infections, London, UK), where they were entered into a central database, developed within BioNumerics software, and designated using an agreed nomenclature. S. Enteritidis PT4 (n=3637) was differentiated into 38 different profiles. Simpson's index of diversity (D) of profiles ranged from 0.2 to 0.4. Profile SENTXB.0001 represented at least 80% of all profiles in each country. S. Typhimurium DT104 (n=1202) was differentiated into 28 different profile types. Simpson's D was at least 0.6 in all countries except in Austria and Italy. In both these countries over 74% of S. Typhimurium DT104 profiles were STYMXB.0013. Profile STYMXB.0061, was predominant in Denmark, Spain, Finland and England and Wales where it represented between 36% and 45% of profiles. Profile STYMXB.0001 represented nearly half of all profiles in Scotland and 23% in England and Wales. PFGE is proving useful for further discrimination within S. Enteritidis PT4 and S. Typhimurium DT104. Ascertainment of international outbreaks involving common serotypes and phage types may be increased by the timely pooling of PFGE profiles within a central database readily accessible to all participating countries.

The Enter-net and Salm-gene databases of foodborne bacterial pathogens that cause human infections in Europe and beyond: an international collaboration in surveillance and the development of intervention strategies.

The free movement of people and foodstuffs between countries are effective ways of distributing disease internationally. There is a requirement for a mechanism whereby data and information on potential outbreaks of foodborne pathogens can be disseminated rapidly to those who need to know. The Enter-net dedicated surveillance network provides this mechanism, complemented by the Salm-gene molecular typing network. Data on epidemiological and microbiological features on current cases, as well as background levels of infections are immediately available within the Enter-net databases. The Salm-gene network with its database of harmonized salmonella PFGE patterns from the participating European countries provides immediate, and electronically exchangeable, DNA fingerprints of outbreak strains. This prompt electronic dissemination of information regarding unusual events with international implications ensures that public health interventions can be implemented and cases of foodborne disease prevented.

An outbreak due to peanuts in their shell caused by Salmonella enterica serotypes Stanley and Newport--sharing molecular information to solve international outbreaks.

Salmonellosis is a global problem caused by the international movement of foods and high incidence in exporting countries. In September 2001, in an outbreak investigation Australia isolated Salmonella Stanley from imported peanuts, which resulted in a wider investigation in Canada, England & Wales and Scotland. Patients infected with Salmonella serotypes known to be isolated from peanuts and reported to surveillance systems were interviewed to determine exposure histories. Tagged image file format (TIFF) images of pulsed-field gel electrophoresis (PFGE) patterns of Salmonella isolates were shared electronically amongst laboratories. Laboratories tested packets of 'Brand X' peanuts from various lots and product lines. In total, 97 cases of S. Stanley and 12 cases of S. Newport infection were found. Seventy-three per cent (71/97) of S. Stanley cases were in persons of Asian ethnicity. Twenty-eight per cent of cases recalled eating Brand X peanuts and a further 13% had peanuts in their house in the previous month or had eaten Asian-style peanuts. Laboratories isolated S. Stanley, S. Newport, S. Kottbus, S. Lexington and S. Unnamed from Brand X peanuts. Isolates of S. Stanley from peanuts and human patients were indistinguishable by PFGE. This international outbreak resulted from a product originating from one country affecting several others. Rapid sharing of electronic DNA images was a crucial factor in delineating the outbreak; multinational investigations would benefit from a harmonized approach.

International trends in salmonella serotypes 1998-2003 - a surveillance report from the Enter-net international surveillance network.

One of the objectives of any surveillance activity is to monitor trends in infections. The international surveillance network for human enteric infections, Enter-net, has been collecting and reporting data on laboratory-confirmed human salmonella infections since 1993. The number of cases identified rose in the mid-1990s, with the peak being in 1997. This paper describes the subsequent decline in salmonella serotypes being reported by the national reference laboratories participating in the Enter-net surveillance network between 1998-2003. The total number of human cases of salmonellosis reported by the Enter-net participating countries has fallen from 220 698 to 142 891 during this period. Even at these reported levels salmonellosis remains a major cause of morbidity in humans.

Dramatic shift in the epidemiology of Salmonella enterica serotype Enteritidis phage types in western Europe, 1998-2003 - results from the Enter-net international salmonella database.

Salmonella enterica serotype Enteritidis is the predominant salmonella serovar identified by the Enter-net national reference laboratories in western Europe. As it is the most commonly recognised serotype, it is important that phage typing is carried out so that outbreaks can be recognised and confirmed, and trends in infections identifed. Data from the Enter-net salmonella database show that there has been a dramatic shift between phage types identified in Europe from 1998-2003. In 1998, the proportion of phage type (PT) 4 was 61.8%, making it the most frequently identified phage type in humans (21 630 cases), whereas by 2003 the proportion of PT4 had fallen to 32.1% (8794 cases) with other strains increasing, both in proportion and numbers. This paper identifies the emerging strains that are becoming more relevant in public health terms.

Trends in antimicrobial drug resistance in Salmonella enterica serotypes Typhi and Paratyphi A isolated in Europe, 1999-2001.

Results of antimicrobial sensitivity tests for strains of Salmonella enterica serotypes Typhi and Paratyphi A isolated from patients in ten European countries between 1999 and 2001 have been transferred electronically to the Enter-net surveillance hub. For Typhi between 22 and 29% of isolates were multiresistant (to four drugs or more) with decreased susceptibility to ciprofloxacin (MIC 0.25-1.0 mg/l) increasing from 20% in 1999 to 26% in 2001. Nineteen of 169 (11%) strains with decreased ciprofloxacin susceptibility were sensitive to nalidixic acid. For Paratyphi A multiple resistance increased from 9% in 1999 to 25% in 2001 and decreased ciprofloxacin susceptibility from 6 to 17%. Clinicians should be aware of the possibility of treatment failures when fluoroquinolones are used as the first-line drug for infections with Typhi and Paratyphi A, particularly for patients recently returning from areas where drug-resistant strains are endemic.

A European outbreak of Salmonella enterica serotype Typhimurium definitive phage type 204b in 2000.

OBJECTIVE: To describe the clinical, epidemiologic and microbiological features of a large outbreak of infection with a multiresistant Salmonella enterica serotype Typhimurium definitive type DT204b infection involving at least 392 people in five European countries. METHODS: Icelandic public-health doctors responded to a report on an Internet news site of an outbreak of infection with a multiresistant strain of Typhimurium DT104 in England by contacting the Public Health Laboratory Service (PHLS) Communicable Disease Surveillance Centre (CDSC). An international alert was sent out through Enter-net. All strains from England & Wales, The Netherlands, Scotland and Germany, and 17 of the outbreak isolates from Iceland, were phage-typed, screened for antimicrobial resistance, and subjected to molecular typing. Hypothesis-generating interviews were conducted, followed by case-control studies performed in Iceland and England. RESULTS: Isolates from cases in Iceland, England and Wales, The Netherlands, Scotland and Germany were identified as Typhimurium DT204b. The antimicrobial resistance pattern was ACGNeKSSuTTmNxCpL. All strains tested displayed an identical plasmid profile. Strains from five cases in England & Wales and five cases in Iceland possessed identical pulsed-field profiles. Although a common source was suspected, only Iceland implicated imported lettuce as a vehicle, with an analytic epidemiologic study (OR = 40.8; P = 0.005; 95% CI 2.7-3175). CONCLUSION: The identification of international outbreaks, necessary for investigation and control, can be facilitated by standardized phage-typing techniques, the electronic transfer of molecular typing patterns, formal and informal links established through international surveillance networks, and the early reporting of national outbreaks to such networks.

Antimicrobial drug resistance in isolates of Salmonella enterica from cases of salmonellosis in humans in Europe in 2000: results of international multi-centre surveillance.

The Enter-net surveillance system received results of antimicrobial sensitivity tests for isolates from over 27 000 cases of human salmonellosis in 2000 in 10 European countries. Almost 40% of isolates were resistant to at least one antimicrobial, with 18% multiresistant. Resistance to ampicillin, streptomycin, sulphonamides and tetracyclines was common, with over 20% of isolates resistant to at least one of these antimicrobials. Clinical resistance to ciprofloxacin was rare, with only 0.5% of isolates exhibiting such resistance (MIC >1.0 mg/l). Resistance to nalidixic acid coupled with a decreased susceptibility to ciprofloxacin (MIC 0.25-1.0 mg/l) was more common, with 14% of isolates showing these properties. Resistance to third-generation cephalosporins was rare with only 0.6% of isolates resistant to cefotaxime. In all countries multiple resistance was most common in Salmonella enterica serotype Typhimurium, with 51% of isolates multiresistant in total. In England and Wales multiple resistance was also prevalent in S. Virchow and S. Hadar, whereas in other countries multiple resistance was common in serotypes such as S. Blockley.

The Salm-gene project - a European collaboration for DNA fingerprinting for food-related salmonellosis.

An external quality assessment of PFGE method to discriminate between salmonella serotypes and lysotypes was carried out by the Salm-Gene project in Europe. A set of 16 strains of S. Enteritidis was sent to 9 national salmonella reference laboratories. By using a harmonised protocol, the PFGE profiles produced were comparable between each centre. In most cases, there was at least 90% similarity between isolates tested in the different European laboratories and there was usually >95% similarity. This suggests that PFGE analyses are reproducible and therefore can be used as a valuable investigation tool combined with epidemiological data.

The Enter-net international surveillance network - how it works.

Enter-net is an international network for the surveillance of human gastrointestinal infections, which monitors salmonellosis and Vero cytotoxin producing Escherichia coli (VTEC) O157, including their antimicrobial resistance. When the network began it in

Salmonella enteritidis in Western Europe 1995-98 - a surveillance report from Enter-net.

A decline in the incidence of Salmonella enteritidis infections in western Europe was identified by the Salm-Net (forerunner of Enter-net) salmonella database between 1993 and 1995, when the numbers of S. enteritidis isolates fell from 37 647 to 31 482. T

Management of the investigation by Enter-net of international foodborne outbreaks of gastrointestinal organisms.

The free circulation of people, goods, and foods within the European Union (EU) states has increased the opportunity for international outbreaks of foodborne infections despite prevention efforts to reduce microbiological contamination of foodstuffs. The

Salmonella enteritidis and S. typhimurium in Western Europe for 1993-1995: a surveillance report from Salm-Net.

Surveillance has been defined as the ongoing systematic collection, collation and analysis of data and the prompt dissemination of the resulting information to those who need to know so that an action can result. This is achieved in two ways. Firstly, i

Salm-Net: a network for human salmonella surveillance in Europe.

Salm-Net aims to prevent human salmonellosis within the EU by strengthening international laboratory based human salmonella surveillance and creating an on-line European database of compatible data available to all participants. Salm-Netis funded by DG XI