An outbreak of listeriosis in Sweden, consisting of nine cases, was investigated by means of molecular typing of strains from patients and strains isolated from suspected foodstuffs, together with interviews of the patients. Listeria monocytogenes was isolated from six of the patients, and all isolates were of the same clonal type. This clonal type was also isolated from a "gravad" rainbow trout, made by producer Y, found in the refrigerator of one of the patients. Unopened packages obtained from producer Y were also found to contain the same clonal type of L. monocytogenes. Based on the interview results and the bacteriological typing, we suspect that at least six of the nine cases were caused by gravad or cold-smoked rainbow trout made by producer Y. To our knowledge, this is the first rainbow trout-borne outbreak of listeriosis ever reported.
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.
Since its first isolation by Murray in 1926 Listeria monocytogenes has become recognized as a significant pathogen occurring worldwide and involving a wide range of wild and domestic animals including man. The first confirmed human listeriosis case in Canada was published by Stoot in 1951. A later survey based on records maintained at the Laboratory Centre for Disease Control, Ottawa showed 101 cases detected over a 21 year period in nine provinces. The overall mortality was 30%. The most frequently isolated serotype was 4b followed by 1 and 1b. Prior to the Nova Scotia epidemic (41 cases) of 1981, fewer than 15 cases per annum had been diagnosed based on hospital discharge records. The Nova Scotia epidemic was unique in that the source and mode of transmission of the organism were determined. Sixty-three strains isolated from this outbreak were typed, and with the exception of one 1a strain, were identified as 4b. These were subsequently classified mainly as phage type 00 042 0000 and 00 002 0000. Listeriosis appears to be a common infection in the animal population in Canada primarily in cattle, sheep, chinchillas, chickens and goats. Outbreaks have been described in rabbits, goats, and chinchillas. Chinchilla farms were affected in one outbreak (serotype 1) in Nova Scotia which was attributed to feeding a new batch of meal containing beet pulp. Many aspects of the epidemiology of listeriosis are obscure. A cycle involving contaminated soil and consumption of raw vegetables has been confirmed as the cause of the Nova Scotia epidemic and could explain a proportion of the sporadic cases.(ABSTRACT TRUNCATED AT 250 WORDS)
Between 1951 and January 1972 listeriosis was diagnosed bacteriologically in 101 Canadian patients. This study adds 80 cases to the 21 reported from Metropolitan Toronto by Sepp and Roy in 1963. The Laboratory Centre for Disease Control, Ottawa, collated epidemiological and clinical data. Serotypes of Listeria monocytogenes included 4b (53), 1 (15), 1b (6), 1a (2), 2 and 3. Clinically, 54 patients had meningitis and 23 septicemia. The mortality rate was 30%.Between 1954 and January 1972 listeriosis affected 15 British Columbian patients: nine were male and six female; 12 were less than 1 or more than 45 years old. Among the patients were a pregnant mother and the son to whom she gave premature birth. A day-old infant and an elderly man died.
Listeria monocytogenes strains that were isolated from 314 human listeriosis cases in Finland during an 11-year period were analyzed by O:H serotyping and pulsed-field gel electrophoresis (PFGE). Serotyping divided the isolates into five serotypes, the most common being 1/2a (53%) and 4b (27%). During the study period, the number of cases caused by serotype 1/2a increased from 22% in 1990 to 67% in 2001, and those caused by serotype 4b decreased from 61 to 27%, respectively. PFGE with restriction enzyme AscI divided the strains into 81 PFGE genotypes; among strains of serotypes 1/2a and 4b, 49 and 18 PFGE types were seen, respectively. PFGE type 1 (serotype 1/2a) was the most prevalent single type (37 strains). Together with six other, closely related PFGE types, PFGE type 1 formed a group of 71 strains, representing 23% of all 314 strains. Strains of PFGE type 1 have also been isolated from cold smoked fish, suggesting a source of human infections caused by this type. Moreover, PFGE type 24 (serotype 1/2c) was significantly associated with gender: 5% of 180 male subjects but none of 132 female subjects (P = 0.012). An electronic database library was created from the PFGE profiles to make possible the prompt detection of new emerging profiles and the tracing of potential infection clusters in the future.
Maternal-foetal infection by Listeria monocytogenes is a rare complication in pregnancy. In the period 1994-2005, 37 culture-confirmed cases of maternal-foetal Listeria monocytogenes infections were reported in Denmark. We examined 36 patients' files in order to evaluate risk factors, clinical and laboratory findings, response to therapy, and outcome for maternal-foetal listeriosis. Patient data and bacteriological findings were divided into 2 groups for comparison: 1 group with children born alive (n=24) and another group with abortion or stillbirth (n=12). 23 of the 36 children survived the acute infection, as did all the mothers. The mothers were generally only mildly affected by the infection. In contrast, among the children born alive, 15 were diagnosed with bacteraemia/septicaemia, 3 children with pneumonia, 3 with neonatal meningitis, and 3 were unaffected. Despite the high frequency of illness only 1 of the live-born children died from the infection and none of the surviving children showed signs of permanent damage at the time they were discharged from hospital. Listeriosis during pregnancy is a serious threat to the unborn child. One-third of culture-confirmed cases of maternal-foetal infections resulted in abortion or stillbirth; however, the prognosis for live-born children is good, even in severely ill newborns.
The records were reviewed of all patients treated at the Vancouver General Hospital over the 15 years from 1965 through 1979 for infections proved by culture to have been caused by Listeria monocytogenes. Although listeriosis is not common in humans, certain groups seem to be susceptible - immunocompromised patients, pregnant women, neonates and the elderly. All these groups were represented among the 22 cases reviewed. There were 17 adults, 3 of whom were pregnant women who had only a mild influenza-like illness. Of the remaining 14 adults 9 were immunocompromised and 5 apparently immunocompetent; 7 presented with meningitis and 7 with bacteremia only. Of the five infants with neonatal listeriosis, two had early-onset disease (bacteremia) and three had the late-onset form (meningitis). Seven patients were treated with penicillin alone, seven with ampicillin alone and eight with penicillin or ampicillin combined with kanamycin, gentamicin or chloramphenicol. There were eight deaths: several were directly attributable to the listeriosis, but in others the severity of the underlying illness was an important factor. Serotypes 1 and 4b were equally common among the 16 specimens of L. monocytogenes that were typed.