Outbreaks of food-borne listeriosis have often involved strains of serotype 4b. Examination of multiple isolates from three different outbreaks revealed that ca. 11 to 29% of each epidemic population consisted of strains which were negative with the serotype-specific monoclonal antibody c74.22, lacked galactose from the teichoic acid of the cell wall, and were resistant to the serotype 4b-specific phage 2671.
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In February 1999, an outbreak of listeriosis caused by Listeria monocytogenes serotype 3a occurred in Finland. All isolates were identical. The outbreak strain was first isolated in 1997 in dairy butter. This dairy began delivery to a tertiary care hospital (TCH) in June 1998. From June 1998 to April 1999, 25 case patients were identified (20 with sepsis, 4 with meningitis, and 1 with abscess; 6 patients died). Patients with the outbreak strain were more likely to have been admitted to the TCH than were patients with other strains of L. monocytogenes (60% vs. 8%; odds ratio, 17.3; 95% confidence interval, 2.8-136.8). Case patients admitted to the TCH had been hospitalized longer before cultures tested positive than had matched controls (median, 31 vs. 10 days; P=.008). An investigation found the outbreak strain in packaged butter served at the TCH and at the source dairy. Recall of the product ended the outbreak.
A total of 245 strains of Listeria monocytogenes were investigated. These strains were isolated from human and animal cases of listeriosis as well as from different kinds of raw and processed foods. Thirty-three electrophoretic types (ETs) were identified among the 245 strains. The strains investigated included all human clinical strains isolated in Denmark during 1989 and 1990. Seventy-three percent of the strains isolated in this period were assigned to one of only two ETs (ET 1 and ET 4). ET 1, which was found to be the most frequently occurring ET among strains isolated from human clinical cases, was also found to occur rather frequently in animal clinical cases. ET 1 was, however, found only sporadically among strains isolated from foods and food factories. The data indicate that there might be something distinctive about the physiology or ecology of the ET 1 clone which makes it more likely to bring about disease in human beings either because of high pathogenicity or because of a special ability to multiply to infectious doses in processed foods. Another type, designated ET 4, was found to be the next most frequently occurring ET, after ET 1, among human clinical isolates. This could be explained by the fact that ET 4 was found to be the most frequently occurring ET within food isolates.
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We studied the association between drinking water, agriculture and sporadic human campylobacteriosis in one region of British Columbia (BC), Canada. We compared 2992 cases of campylobacteriosis to 4816 cases of other reportable enteric diseases in 2005-2009 using multivariate regression. Cases were geocoded and assigned drinking water source, rural/urban environment and socioeconomic status (SES) according to the location of their residence using geographical information systems analysis methods. The odds of campylobacteriosis compared to enteric disease controls were higher for individuals serviced by private wells than municipal surface water systems (odds ratio 1·4, 95% confidence interval 1·1-1·8). In rural settings, the odds of campylobacteriosis were higher in November (P = 0·014). The odds of campylobacteriosis were higher in individuals aged ?15 years, especially in those with higher SES. In this region of BC, campylobacteriosis risk, compared to other enteric diseases, seems to be mediated by vulnerable drinking water sources and rural factors. Consideration should be given to further support well-water users and to further study the microbiological impact of agriculture on water.
Listeria monocytogenes, a psychrotrophic organism capable of growing at refrigeration temperatures, is of major concern in extended shelf life, refrigerated foods. Considering that as much as 80-90% of human listeriosis cases are linked to the ingestion of contaminated food, human cases are predominantly seen in high-risk individuals, including organ-transplant recipients, patients with AIDS and HIV-infected individuals, pregnant women, cancer patients, and the elderly. In 2001, the Canadian Listeriosis Reference Service (LRS) was created by the Bureau of Microbial Hazards (Health Canada) and the National Microbiology Laboratory (now part of the Public Health Agency of Canada). Major goals of the LRS include investigation of listeriosis cases and maintenance of a national collection of isolates. The LRS intends to create a comprehensive molecular epidemiological database of all isolates in Canada for use as a resource for outbreak investigations, research and other microbiological investigations. The PFGE profiles are being established and stored for clinical, food, environmental, and possibly animal strains of L. monocytogenes. The LRS pursues research activities for investigation and implementation of other molecular methods for characterizing L. monocytogenes isolates. Ribotyping, Multi-locus Sequence Typing (MLST), Variable Number of Tandem Repeats (VNTR), Multi-locus virulence sequence typing (MLVA), microarray- based technologies and sequence-based typing schemes, are being investigated on selected diversity sets. The LRS has also used PFGE typing for outbreak investigations. The molecular epidemiological data, timely coordination and exchange of information should help to reduce the incidence of listeriosis in Canada. In Canada, listeriosis is not a national notifiable disease, except for the province of Quebec, where it has been since 1999. The LRS, Canadian Public Health Laboratory Network, and federal epidemiologists are currently working on making human listeriosis notifiable throughout Canada.
Public health authorities place a high priority on investigating listeriosis outbreaks, and these epidemiological investigations remain challenging. Some approaches have been described in the literature to address these challenges. This review of listeriosis clusters and outbreaks investigated in the Province of Quebec (Quebec) highlights investigative approaches that contributed to identifying the source of these outbreaks.
The Laboratoire de Santé Publique du Québec (LSPQ) implemented pulsed-field gel electrophoresis (PFGE) molecular subtyping in 1997 to identify Listeria monocytogenes clusters among isolates from invasive listeriosis cases identified throughout Quebec. A cluster was defined as three cases or more with the same or similar PFGE profiles (=3 band difference) occurring over a 4-month period. An investigation was initiated if the epidemiologic indicators suggested a common source. Listeriosis data from LSPQ's database were reviewed to identify and describe clusters detected from 1997 to 2011, including those that led to an outbreak investigation. Epidemiological reports prepared following each outbreak were also reviewed.
Eleven clusters were identified in the province by LSPQ between 1997 and 2011. Outbreak investigations were initiated for six clusters, four of which involved more than 10 cases. Factors that contributed to identifying the source for three of these outbreaks highlighted the value of (1) making all stakeholders (food safety and inspection services, public health authorities, and laboratories) aware of any ongoing investigation and sharing relevant information even if the source is not yet identified; (2) promptly collecting food samples identified and considered as possible vehicles of infection identified during the interview of a Listeria case; (3) collecting food items and/or environmental samples in locations reported in common by cases in the same cluster.
Multiple approaches should be considered when investigating L. monocytogenes clusters. Networks to facilitate continuous exchange of human and food data between public health and food safety partners should be encouraged.
A total of 84 strains of Listeria monocytogenes were analysed by multilocus enzyme electrophoresis at twelve enzyme loci. Eight enzyme loci were polymorphic with between 2 and 4 alleles per locus. Fourteen electrophoretic types (ETs) were identified. Among 62 human clinical isolates from Denmark, 8 different ETs were defined. Two ETs, designated ET 1 and ET 6, accounted for 77% of the human clinical isolates investigated. These ETs are identical with those responsible for several epidemics in Switzerland and in the United States. Comparison of 58 isolates of L. monocytogenes, typed by MEE, in relation to phage typing showed that phage typing was more discriminatory than MEE. The ability of MEE to distinguish between phage types of Epi-type and other phage types, however, was almost optimal. MEE typed 23 of 24 strains of Epi-type as belonging to ET 1. In contrast ET 1 was not found in 26 strains with phage types other than the Epi-type.
Listeria monocytogenes was isolated from critical control points in a Danish turkey processing plant, from turkey products and from cases of human listeriosis. During processing in the plant the prevalence of L. monocytogenes ranged from 25.9 to 41.4%. Cleaning and disinfection decreased the prevalence to 6.4%. Isolates of L. monocytogenes were characterized by pulsed-field gel electrophoresis (PFGE) using restriction endonuclease ApaI. Identical DNA types were obtained from turkey products and the processing line even after cleaning and disinfection. Two identical DNA types were demonstrated among isolates from turkey products and human cases of listeriosis. The prevalence of L. monocytogenes in turkey products ranged from 7.3 to 17.4% for ready-to-eat products and raw products, respectively. Since none of the 27 flocks examined before slaughter sampled positive for L. monocytogenes and the prevalence increased during processing, the potential risk from turkey meat was apparently due to factory hygiene rather than intrinsic contamination of the turkeys.
At least three outbreaks of listeriosis associated with seafood have been reported. Listeria monocytogenes is widely distributed in the general environment including fresh water, coastal water and live fish from these areas. Contamination or recontamination of seafood may also take place during processing and low levels (
Forty Listeria monocytogenes isolates obtained in European and Far East regions of Russia were differentiated on the basis of polymorphism of 5 markergenes. Total length of concatemers obtained after sequencing of internal fragments of genes inlA, inlB, inlC, inlE and prs was 3029 b.p. Comparative analysis of concatemers' sequences revealed 237 variable nucleotides. Totally, 25 sequence types were revealed, and isolates from European and Far East regions belonged to different types. On the dendrogram isolates split on 2 clusters, which correspond to early described phylogenetic lines of L. monocytogenes specie. Isolates obtained in European and Far East regions formed independent subclusters within main clusters. Fifteen clinical isolates of L. monocytogenes belonged to 7 different types. Analysis of epidemiologic data on time and place of isolates obtaining suggested that isolates of the same sequence type are epidemiologically related and might represent one strain; index of discrimination for proposed typing method was calculated as 0.982.