Browsing by Subject "elintarvike- ja ympäristöhygienia"

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  • Kärenlampi, Rauni (Helsingin yliopisto, 2007)
    Campylobacter jejuni and C. coli are the most frequent causes of bacterial gastroenteritis in Finland. Most Campylobacter infections are sporadic and the sources of infection remain unidentified. Risk factors for Campylobacter infections include eating undercooked meat, especially chicken, drinking unpasteurized milk or contaminated water, having contact with pets and foreign travel. The asaccharolytic nature and inertness in traditional biochemical tests makes the identification of Campylobacter spp. difficult. We studied the phylogeny of 12 Campylobacter spp. based on partial 593-bp groEL gene sequences. In general, lower interspecies sequence similarities were observed for groEL (range from 65% to 94%) than for the 16S rRNA gene (range from 90% to 99%). However, the intraspecies groEL sequence similarities were high (range from 95% to 100%) making groEL gene sequencing and the PCR-RFLP method developed in our study valuable for the identification of Campylobacter species. The minimum growth temperature of around 30°C makes multiplication of Campylobacter in foods highly unlikely. However, the survival in cool and humid conditions, such as chicken meat stored refrigerated, has been shown to be good. The survival of C. jejuni was investigated on iceberg lettuce, cantaloupe, cucumber, carrot and strawberries. Survival on strawberries was significantly lower than on the other produce, as was survival at 21°C compared to 7°C. Survival on the other produce was comparable with earlier reports in water and milk, but not as good as that observed on chicken meat. The association of Penner HS serotypes and pulsed-field gel electrophoresis (PFGE) SmaI/KpnI genotypes of 208 human and 30 chicken caecal C. jejuni isolates was studied during the seasonal peak in 1999 in Finland. Of the strains from humans, 46% had overlapping sero/genotypes with those from chicken. During the seasonal peak in 2003, C. jejuni and C. coli isolates from human fecal samples showed 5.7% and 61% PFGE (KpnI) profile overlap with cattle fecal and poultry retail meat isolates, respectively, demonstrating the importance of genotypes circulating in chicken as compared to those isolated from cattle in human infections. However, in 1999, human cases were also isolated prior to the slaughter of the chicken flock colonized by the same Campylobacter sero/genotype, suggesting that common environmental sources may exist for both human infections and chicken flock contamination. Multilocus sequence typing analysis of 361 Finnish C. jejuni and C. coli isolates from human patients, cattle, chicken and turkey samples, provided new information on the potential association of some clonal groups of this diverse organism with source of isolation as well as demographic characteristics.
  • Niskanen, Taina (Helsingin yliopisto, 2010)
    Yersinia pseudotuberculosis is an animal pathogen widespread in nature. The bacterium has caused infections in humans occasionally. Most of the reported Y. pseudotuberculosis -infections are sporadic, and the sources and vehicles of Y. pseudotuberculosis remain obscure. Y. pseudotuberculosis has emerged as an outbreak -associated pathogen in Finland since 1997. Indirect evidence has indicated that Y. pseudotuberculosis is a potential food borne pathogen, but no specific food has been previously confirmed as a source of the human infections. The aim of this thesis was to determine the prevalence of Y. pseudotuberculosis in different animal species and to evaluate them as a possible source of Y. pseudotuberculosis. Clinically healthy pigs were found to carry Y. pseudotuberculosis. The prevalence of Y. pseudotuberculosis was 4 % and 14 % in fattening pigs at slaughterhouse and at farm level, respectively. All Y. pseudotuberculosis isolates from pigs were pathogenic. Migratory birds representing 57 different bird species were studied for pathogenic Y. pseudotuberculosis during spring and autumn migration. Pathogenic Y. pseudotuberculosis was recovered from two species of birds during spring migration. Y. pseudotuberculosis was first time confirmed to be the cause of a food borne outbreak through domestically produced iceberg lettuce in epidemiological study. Contamination of iceberg lettuce was investigated on farm level in a two-year survey. Several factors predisposing to Y. pseudotuberculosis contamination of lettuce were found on the farms, including a large population of deers and free access of wild animals to unfenced lettuce fields and to irrigation water sources. Pulsed-field gel electrophoresis (PFGE) analysis was optimized for efficient molecular typing method for Y. pseudotuberculosis isolates. PFGE was used to compare Y. pseudotuberculosis isolates from different origin. Y. pseudotuberculosis isolates of different sources showed high genetic diversity, while Y. pseudotuberculosis isolates found in same animal species representing the same serotype showed limited genetic diversity. Identification of environmental Y. pseudotuberculosis isolates was found to be incorrect based solely on biochemical tests. Commercial test kits misidentified some environmental Yersinia spp. isolates as Y. pseudotuberculosis. However, no specific virulence genes of Y. pseudotuberculosis were found in these isolates by polymerase chain reaction (PCR) targeting these gene areas.
  • Ortiz Martínez, Pilar (Helsingin yliopisto, 2010)
    Enteropathogenic Yersinia can enter the food chain and infect consumers via pork. Although yersiniosis is the third most common bacterial enteric disease in Europe, there has been a lack of studies concerning the prevalence and bioserotypes of enteropathogenic Yersinia in pigs from European countries. This study was conducted in order to gain further information on the prevalence of enteropathogenic Yersinia in pigs from separate European countries. In order to examine the transmission routes of enteropathogenic Yersinia in the pork production chain from the farm to the slaughterhouse, enteropathogenic Yersinia strains were characterised in Finland by PFGE. Because the conditions on a farm can affect the prevalence of enteropathogenic Yersinia, possible farm factors associated with Yersinia prevalence were also investigated by using a questionnaire and on-farm observations. Pathogenic Yersinia enterocolitica was a common finding among all European countries included in the study. The highest (93%) and lowest (32%) prevalence of pathogenic Y. enterocolitica was observed among pigs from Spain and Italy, respectively. The prevalence in Estonia and Latvia in Northern Europe was lower than in Spain, but still at a high level of 89% and 64%, respectively, among pigs. The Leningrad region of Russia showed one of the lowest prevalence among the studied European countries. In addition, pathogenic Y. enterocolitica was present among 44% of pigs from Belgium and England or Central Europe and Western, respectively. The highest prevalence of Yersinia pseudotuberculosis was detected among English pigs (18%). Furthermore, 7%, 5% and 2% of pigs examined from the Leningrad region of Russia, Latvia and Belgium, respectively, and 1% in Italy and Estonia were positive for Y. pseudotuberculosis. Cold enrichment for 7 and 14 days combined was a more efficient method to isolate enteropathogenic Yersinia when compared to selective enrichment. The most common human pathogenic bioserotype 4/O:3 of Y. enterocolitica was also present in all studied European countries, predominating among Belgian (91%), Estonian (100%), Italian (99%), Latvian (100%), Russian (100%) and Spanish (100%) pigs, but not among English pigs (11%). In England, the most common human pathogenic bioserotypes of Y. enterocolitica were 2/O:9 (33%) and 2/O:5 (26%). Y. enterocolitica bioserotype 2/O:5 was also found among Italian (1%) pigs. In addition, less frequently isolated European human pathogenic bioserotypes 2/O:3 and 3/O:3 were respectively found in 7% and 0.3% of pigs from England, and 3/O:9 in 9% of pigs from Belgium. Bioserotype 2/O:3 of Y. pseudotuberculosis, the most commonly isolated type in pigs in Finland, predominated among Belgian (60%), English (34%), Estonian (100%), Latvian (100%) and Russian (100%) pigs, and was present among Italian pigs (20%). Bioserotypes such as 1/O:1, 1/O:2, 1/O:3, 1/O:4, 2/O:1, 2/O:5 and 3/O:3 were also found. Y. pseudotuberculosis 1/O:1 was predominant in Italy (60%), and also found in England (26%) and Belgium (20%). Y. pseudotuberculosis 1/O:2 was isolated from Belgian (20%) and English (7%) pigs. Bioserotypes 1/O:3 (5%), 1/O:4 (24%), 2/O:1 (3%), 2/O:5 (1%) and 3/O:3 (1%) were additionally found in England, showing the highest diversity of different bioserotypes in this country. In Finland, only bioserotype 4/O:3 of Y. enterocolitica and 2/O:3 of Y. pseudotuberculosis were isolated. Undistinguishable genotypes of Y. enterocolitica and Y. pseudotuberculosis isolated from a farm and a slaughterhouse indicated that carcass contamination has its origin on the farm and enteropathogenic Yersinia is transported with the pig to the slaughterhouse. Based on Y. enterocolitica genotypes, Y. enterocolitica-positive pigs are contaminating pluck sets, and pluck sets can also be contaminated with Y. enterocolitica from other sources in the slaughterhouse. Factors associated with the high prevalence of Y. enterocolitica on farms according to correlation and two-level logistic regression analysis were drinking from a nipple, the absence of coarse feed or bedding for slaughter pigs, and no access of pest animals to the pig house. Those farms with an organic or low-production capacity showed a lower prevalence than high-production capacity conventional farms. Farm factors associated with the presence of Y. pseudotuberculosis in Finnish farms were contact with pest animals and the outside environment and a rise in the number of pigs on the farm. Organic production farms had a higher prevalence than conventional farms.
  • Sjöman, Maria (Helsingin yliopisto, 2010)
    Two different typing methods, serotyping and pulsed-field gel electrophoresis (PFGE) typing, were used to study Listeria monocytogenes contamination in food processing plants and human foodborne L. monocytogenes infections. L. monocytogenes contamination was studied in two different types of food processing plants: one ice cream plant and two broiler abattoirs. A dominant L. monocytogenes PFGE type of serotype 1/2b was found to have persisted in this ice cream plant for at least seven years. This strain was found in the production environment, ice cream, and equipment, especially in the packaging machine. Two broiler abattoirs were evaluated for L. monocytogenes contamination of the processing environment, broiler meat, and broiler meat products. Contaminated sites in the broiler processing environment included the air chiller, the conveyor belt leading to the meat packaging area, and the skin removing machine, possibly suggesting important contamination points of broiler meat. The two broiler abattoirs harboured different L. monocytogenes PFGE types. Retail broiler meat samples were also analyzed in order to compare the results to those from the broiler abattoirs. Of the raw broiler meat pieces bought from retail stores, 62% tested positive for L. monocytogenes. PFGE types found in the retail raw broiler meat pieces were identical to the PFGE types found at the broiler abattoirs where they had been processed. PFGE characterized these industrial strains and enabled targeted cleaning and disinfection practices at these food processing plants. L. monocytogenes isolates from human invasive infections from 1990-2001 in Finland were studied in order to detect a possible clustering of cases. The most common L. monocytogenes serotype was 1/2a. Altogether 81 different PFGE types were found using one restriction enzyme (AscI). A strain of an identical PFGE type of serotype 1/2a had appeared in 1994, accounting for 12% of the invasive infections. In addition to the human invasive infections, we studied two foodborne L. monocytogenes outbreaks in Finland. In the first outbreak in 1997, five healthy persons fell ill with febrile gastroenteritis. The outbreak was associated with the consumption of vacuum-packed cold-smoked rainbow trout containing L. monocytogenes. Indistinguishable L. monocytogenes PFGE types of serotype 1/2a were isolated from the incriminated fish product lot and human stool samples. This same L. monocytogenes PFGE type was identical to the most common PFGE type in human invasive L. monocytogenes infections in Finland during 1994-2001. The second outbreak studied occured in 1999, when 25 patients acquired listeriosis from butter, 6 of whom died. This outbreak was initially identified with the help of timely serotyping and PFGE typing, and resulted from a globally uncommon strain of L. monocytogenes of serotype 3a and unique PFGE type. For regular epidemiological surveillance of human L. monocytogenes infections with PFGE typing, the use of one restriction enzyme is sufficient, but in the case of contamination studies or suspected outbreaks, the use of at least two restriction enzymes is recommended in order to increase the discrimination power of PFGE typing.