Sirvi Autor "Roasto, Mati (advisor)" järgi
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Kirje Assessment of Listeria monocytogenes growth potential and dynamics in raw readyto-eat rainbow trout marinated with juice pomaces(Eesti Maaülikool, 2024) Jortikka, Salli Josefiina; Roasto, Mati (advisor); Mäesaar, Mihkel (advisor)Ready-to-eat foods are potential sources of foodborne infections as they are usually consumed without any beforehand treatment that would eliminate or reduce the levels of microorganisms. Listeria monocytogenes is one of the most dangerous foodborne pathogen found in chilled ready-to-eat foods due to its ability to grow at refrigerator temperatures. With food additives, the growth potential of microorganisms may be reduced. By using natural additives that have bactericidal or antibacterial properties, the growth and number of pathogenic microorganisms can be reduced and at the same time, the food business operators could answer to the growing demand to produce more naturally produced food items. The aim of the study was to assess the growth potential of L. monocytogenes in marinated raw ready-to-eat rainbow trout products in which the marinades contained apple, black currant, rhubarb, or tomato pomace water extracts. It was found that by using pomace extracts from apple, black currant, rhubarb, and tomato as marinade components for rainbow trout, it is possible to classify the marinated fish samples as “ready-to-eat food unable to support the growth of L. monocytogenes”, as defined by the Commission Regulation (EC) No 2005/2073. Black currant pomace was the most effective in decreasing the growth of L. monocytogenes in the marinated fish samples during the 15day durability period.Kirje Campylobacter spp. and Listeria monocytogenes in poultry products in Estonia(Eesti Maaülikool, 2016) Praakle, Kristi; Roasto, Mati (advisor); Hänninen, Marja-Liisa (advisor); Korkeala, Hannu (advisor)Campylobacteriosis, caused by thermotolerant Campylobacter species, is continued to be one of the most commonly reported zoonosis in humans in the European Union, and Campylobacter is recognized as the most common causative agents of bacterial gastroenteritis in developed world. Listeriosis, the disease caused by Listeria monocytogenes, is a lifethreatening disease for individuals with compromised immune systems. Consumption of different foods, including poultry products, have been associated with campylobacteriosis and listeriosis. Healthy birds may shed Campylobacter spp. and L. monocytogenes in fecal material asymptomatically. Poultry meat may become contaminated with fecal matter during slaughter or through cross-contamination during processing. The main goals of the present thesis were 1) to determine the prevalence and counts of Campylobacter spp. and the prevalence of L. monocytogenes in Estonian and imported raw poultry meat, 2) to serotype and genotype using pulsed-field gel electrophoresis both Campylobacter and L. monocytogenes isolates, and 3) to determine the antimicrobial susceptibility of the Campylobacter isolates. The studies showed that the poultry products of Estonian origin and imported to Estonia were contaminated with Campylobacter spp. and L. monocytogenes. There was high sero- and genotype diversity among Campylobacter and L. monocytogenes isolates. High level of resistance to fluoroquinolones, tetracycline, ampicillin, and erythromycin among the Campylobacter isolates were detected.Kirje Campylobacter spp. in Estonian Broiler Chicken Production Chain and the Co Effect of Pro- and Prebiotics on the Campylobacter spp. Strains in vitro(Eesti Maaülikool, 2010) Meremäe, Kadrin; Elias, Priit (advisor); Roasto, Mati (advisor); Hänninen, Marja-Liisa (advisor)Termofiilsed kampülobakterid on sagedased akuutse gastroenteriidi tekitajad inimestel. Kampülobakterenteriiti haigestumise peamisteks põhjusteks on ebapiisavalt kuumtöödeldud või kuumtöötluse järgselt kampülobakteritega saastunud broileriliha tarbimine. Seepärast võib Campylobacter spp. laialdane levik broileriliha tootmise ahelas kujutada tõsist ohtu tarbija tervisele. Viimastel aastatel on esile tõusnud ka Campylobacter spp. antibiootikumidele resistentsuse probleem, kuna on avastatud kampülobakterite multiresistentseid tüvesid nii veterinaarmeditsiinis kui humaanmeditsiinis isoleeritud tüvede seas. Arvestada tuleb sellega, et antibiootikumidele resistentsete tüvede poolt põhjustatud kampülobakterenteriit ei pruugi alluda tõsisemate vaevuste korral vajalikuks osutunud antibiootikumravile. Seepärast on oluline teaduslike baasuuringute raames välja selgitada pro- ja prebiootikumide võimalused pärssimaks antibiootikumidele tundlikke ja resistentsete Campylobacter spp. isolaatide elutegevust in vitro. Probiootikumideks nimetatakse inimese soolestikust isoleeritud eluvõimelisi mittepatogeenseid baktereid, mis omavad kliiniliselt tõestatud kasulikku toimet peremeesorganismile. Prebiootikumidena tuntakse lisandeid, mida ei lagundata maos ja peensooles, kuid on sobivaks toitaineks probiootilistele bakteritele nii organismi jämesooles kui ka probiootikume sisaldavates toiduainetes. Käesolevas töös uuriti aastatel 2002-2007 Campylobacter spp. levikut farmi, tapamaja ja jaemüügi tasandil, et saada ülevaade Campylobacter spp. kontaminatsiooni ulatusest broileriliha tootmise ahelas Eestis (uuring I). Töö raames määrati aastatel 2005 2006 isoleeritud Campylobacter spp. tüvede resistentsus antibiootikumide suhtes, et hinnata probleemi tõsidust Eestis (uuring II). Töös uuriti ka probiootiliste bakterite testtüvede (kombinatsioonis 1% oligofruktoosi või 1% inuliiniga ja prebiootikumideta) mõju antibiootikumidele tundlike ja resistentsete C. jejuni isolaatidele in vitro, et hinnata probiootikumide antimikroobseid omadusi nii broileriliha kui ka inimese väljaheite proovidest isoleeritud kampülobakterite suhtes (uuringud III, IV). Mueller Hintoni puljongites määrati probiootikumide poolt produtseeritud orgaaniliste hapete kontsentratsioon ning kasvukeskkonna pH, et välja selgitada orgaaniliste hapete sisalduse, pH muutuse ja C. jejuni arvukuse vahelised seosed. Töö käigus uuriti ka prebiootikumide mõju probiootikumide eluvõimelisusele ja aktiivsusele, et hinnata nende koosmõju erinevates kasvukeskkondades, ning välja töötada sobivad kombinatsioonid C. jejuni valitud tüvede elutegevuse pärssimiseks in vitro (uuringud III, IV). Uurimistöös jõuti järgmiste tulemuste ja järeldusteni. Campylobacter spp. isoleeriti 163 (12.3%) Eesti päritolu broileriliha proovist jaemüügi tasandil ja 115 (6.3%) umbsoolesisuproovist tapamaja tasandil. Farmi tasandil osutusid kõik 1254 värsket roojaproovi Campylobacter spp. suhtes negatiivseks. Järelikult oli Campylobacter spp. kontaminatsioon Eestis kõikidel broileriliha tootmise tasanditel madal võrreldes samalaadsete uuringute tulemustega Euroopa Liidus. Uurimistulemused näitasid, et Eesti broileriliha tootmise ahelas esineb Campylobacter spp. levikus kõrghooaeg juulist septembrini. Campylobacter spp. liigiline identifitseerimine näitas, et C. jejuni (98.2%) oli Eesti broileriliha tootmise ahelas kõige enam isoleeritud liik, millele järgnesid C. coli (1.4%) ja C. lari (0.4%). Uurimistulemustest selgus, et aastatel 2005-2006 osutusid 104 (79.4%) C. jejuni isolaati resistentseks ühe või enama testitud antibiootikumi suhtes. Järelikult tuleks jätkata isoleeritud Campylobacter spp. tüvede tundlikkuse määramist antibiootikumidele ning võtta kasutusele täiendavad meetmed, et minimeerida või vältida veel ulatuslikumat antibiootikumidele resistentsete C. jejuni isolaatide teket ja levikut. Saadud tulemused näitasid, et 27.5% isoleeritud C. jejuni tüvedest olid multiresistentsed, kusjuures kõik isolaadid olid resistentsed enrofloksatsiinile. Antud tulemus on murettekitav, sest multiresistentsuse kõrge näitaja Campylobacter spp. isolaatide seas oli antud uuringute põhjal üks kõrgemaid võrreldes samalaadsete uuringute tulemustega Euroopa Liidus. In vitro segatud bakterkultuuride katsed näitasid, et L. acidophilus ATCC 4356 kombinatsioonis 1% inuliini või 1% oligofruktoosiga ning B. bifidum Bb12 ja B. longum B46 kombinatsioonis 1% oligofruktoosiga inhibeerisid täielikult kõikide testitud C. jejuni isolaatide elutegevuse. Probiootikumide toime oli samalaadne (P > 0.05) nii neile testitud C. jejuni tüvedele, mis isoleeriti kas broilerilihalt või inimese väljaheitest, kui ka neile, mis olid tundlikud või resistentsed uuritud antibiootikumidele. Järelikult probiootiliste bakterite antimikroobne aktiivsus C. jejuni suhtes sõltus eelkõige probiootikumi liigist ja lisatud prebiootikumist, mitte aga C. jejuni tüvest. Saadud in vitro tulemused annavad alust arvata, et valitud probiootikumide antimikroobne aktiivsus kombinatsioonis sobiva 1% prebiootikumiga kõikide testitud C. jejuni suhtes on põhjendatav probiootikumide poolt intensiivse orgaaniliste hapete produtseerimisega, mille tagajärjel kasvukeskkonna pH vähenes kampülobakterite elutegevust pärssivale tasemele, vahemikuni 4.28-4.69. Uurimistulemustest selgus, et prebiootikumide tõhusus probiootikumide eluvõime ja aktiivsuse mõjutamisel sõltus kõige enam selle kontsentratsioonist kasvukeskkonnas. Majanduslikel kaalutlustel ja prebiootiliste lisandite efektiivsuse olemasolu tõttu osutus optimaalseks koguseks 1% (kg/l). Prebiootikumidest suurendasid probiootikumide aktiivsust ning arvukust eelkõige oligofruktoos ja seejärel inuliin. Järelikult antud prebiootikumid koostoimes valitud probiootikumidega osutusid sobilikuks inhibeerimaks C. jejuni arvukust ja elutegevust in vitro.Kirje Campylobacter spp. in fresh broiler chicken meat and pig caecal samples in Estonia(Estonian University of Life Sciences, 2024) Tedersoo, Triin; Meremäe, Kadrin (advisor); Roasto, Mati (advisor); Institute of Veterinary Medicine and Animal Sciences; Zwietering, Marcel (opponent)ABSTRACT. Campylobacteriosis has been the most frequently reported zoonosis in the European Union (EU) since 2005. A total of 127,840 confirmed cases of human campylobacteriosis were reported in 2021, with a notification rate of 41.1 per 100,000 people in the EU. Campylobacter jejuni and Campylobacter coli are the main Campylobacter species causing 80 and 10% of human infections, respectively. The majority of Campylobacter spp. infections are mild and self-limiting. However, it can result in severe systemic illness or mortality in children, older adults, and immunocompromised individuals. Several studies have confirmed that poultry meat, especially broiler chicken meat, is the primary source of human campylobacteriosis; however, the role of pork in the development of Campylobacter enteritis in humans has not been well studied. Nevertheless, pig-derived C. coli have been linked to Campylobacter infections in humans. The current study revealed that broiler chicken meat of Lithuanian and Latvian origin sold in Estonian retail stores was contaminated with highly resistant Campylobacter spp. High genetic diversity was observed among the Campylobacter isolates from fresh broiler chicken meat samples. Genotyping has revealed a link between campylobacteriosis in Estonia and imported fresh broiler chicken meat. The antimicrobial resistance profile of Lithuanian broiler chicken meat isolates overlapped with those obtained from humans in Estonia. This implies that eating Campylobacter-contaminated broiler chicken meat could pose a potential risk to Estonians. In addition to broiler chicken meat, pork consumption can also pose a potential public health risk, as this study revealed that pigs are carriers of antimicrobial-resistant C. coli. Antimicrobial-resistant bacteria in food can reach consumers and pose a threat to their health. To mitigate the incidence of antimicrobial resistance in Campylobacter spp., it is critical to adhere to treatment guidelines for both humans and animals, as well as implement proper practices at the farm level.Kirje Food safety of plant based foods : [presentation](Estonian University of Life Sciences, 2024) Mandel, Tiina; Mäesaar, Mihkel (advisor); Roasto, Mati (advisor); Reinik, Mari (advisor)The presentation took place at the EU Food Safety Forum 2024 “Youngs acting for the future of Food Safety in EU”, Rome, December 02-03, 2024.Kirje Genomic analyses of associations between Campylobacter jejuni strains isolated from humans and broiler chicken meat(Eesti Maaülikool, 2025) Takkinen, Hanna Katriina; Mäesaar, Mihkel (advisor); Roasto, Mati (advisor); Chair of Veterinary Biomedicine and Food HygieneCampylobacteriosis remains a leading cause of foodborne gastroenteritis in Europe, with Campylobacter jejuni responsible for nearly 90% of human cases. Poultry, especially broiler chicken meat, is widely recognised as a major source of human infection due to the high prevalence of Campylobacter in poultry meat. This study investigates the genomic relationships between C. jejuni strains isolated from Estonian human cases and Lithuanian broiler chicken meat using core genome multilocus sequence typing (cgMLST), with a focus on four sequence types (STs): ST122, ST464, ST7355, and ST9882. The cgMLST analysis revealed a strong genomic similarity (≤ 3 allelic differences) between human and poultry isolates of ST122, ST464, and ST7355, indicating potential direct or recent common sources of infection. In contrast, ST9882 showed greater genomic divergence (up to 18 allelic differences). These findings were corroborated by shared antimicrobial resistance (AMR) profiles. Data mining and following analysis confirmed the recurring presence of ST122 and ST464 in both poultry and human cases across Europe and associated ST122 with severe clinical outcomes, including Guillain-Barré syndrome. Despite these insights, a significant limitation of the study was the lack of detailed epidemiological metadata, such as patient exposure history, limiting the ability to confirm transmission pathways. Nonetheless, this is the first study in the Baltic States to demonstrate such genomic associations between Lithuanian poultry and Estonian human C. jejuni isolates using cgMLST. These results reinforce the role of poultry, especially from cross-border trade, as a key source of human Campylobacter infections in Estonia. Future research should focus on integrating genomic data into the surveillance and guide effective public health interventions aimed at reducing campylobacteriosis incidence and the spread of antimicrobial-resistant strains in the food production and consumption chainKirje Listeria monocytogenes-positive food samples from 2014 to 2023 and reported human listeriosis cases in Estonia(Eesti Maaülikool, 2025) Plym, Nora; Roasto, Mati (advisor); Mäesaar, Mihkel (advisor); Chair of Veterinary Biomedicine and Food HygieneReady-to-eat foods can be a significant source of foodborne illnesses, as they are typically consumed without any prior processing that would eliminate or lower microbial levels. One of the most harmful pathogens in these foods can be Listeria monocytogenes, which poses a particular risk in refrigerated ready-to-eat foods with long shelf life because it can grow at low temperatures, and can achieve high concentrations in foods. Additionally, the presence of L. monocytogenes in low concentrations can pose a significant risk to vulnerable groups, such as immunocompromised individuals, for whom consuming contaminated food may lead to listeriosis. The main aim of the study was to retrospectively analyse L. monocytogenes-positive food samples in ready-to-eat food products in Estonia in ten years and to see if there are statistically significant differences between various food groups. The highest proportion of L. monocytogenes-positive samples from detection analyses were revealed for categories raw fish, raw fishery products and cold-smoked fish. According to the enumeration method, the numeric criterion of 100 CFU/g of product was exceeded in categories cold-smoked fish products, followed by poultry meat and products thereof, hot-smoked fish, other food, fishery products ready-to-eat, pig meat and products thereof.Kirje Nitrate and Nitrite Contents in Vegetables and Vegetable-based Foods, Transformation Dynamics and Dietary Intake(Eesti Maaülikool, 2010) Elias, Terje; Kiis, Alida (advisor); Püssa, Tõnu (advisor); Roasto, Mati (advisor)Present research is the first complex study in Estonia about nitrate and nitrite contents, which comprises the complete vegetable production chain from raw material to final product. In accordance with data from literature, the vegetables and vegetable-based foods are the main source of nitrates for man. High doses of nitrates and nitrites are the risks for human health, especially for infants and for small children. Final aim for present work was to expose the possible exceeding of ADI values for nitrate and nitrite, especially in the case of small children who belong to the main risk group. In the present investigation, the mean values and contents of nitrates and nitrites in vegetable products were determined. For the first time in Estonia the daily intake of nitrates from vegetables or vegetable-based foods by children and the whole population was estimated. The results of the analyses of nitrate and nitrite contents demonstrated that permitted nitrate limit concentrations were exceeded only a few cases. The nitrate content is dependent on the harvesting period and on the growing conditions. Vegetables grown under cover showed higher levels of nitrate than those grown in the open field conditions. The results of this study showed that nitrate content varied highly between the species of vegetables used for the raw juice production. Lower initial contents of nitrate were detected in industrial carrot juice and in home-made carrot and cabbage raw juices. Initial microbial counts and pH-values were similar for all raw juices. The nitrate contents decreased and nitrite contents increased after 24 h and 48 h of storage. The changes in nitrate and nitrite contents were lower in industrial raw vegetable juices compared to home-made raw juices but tendencies were generally similar. All microbial counts, such as total viable counts, coliform counts, mold and yeast counts, increased. The highest increase of total viable counts was reported in home-made raw juices after 48 h of storage at ambient temperatures. The microbial growth had correlation with the decrease of pH-values. The raw juices should be consumed soon after preparation and stored only shortly at refrigerated temperatures. The decreases of nitrate contents in industrial vegetable-based infant foods were registered along the entire technological production line. At first stage the nitrate contents were analysed from vegetables before and after peeling and washing. The decrease of nitrates from 17 to 52% was reported, depending on vegetable species. The analyses of nitrate contents from different technological stages of industrial infant food production showed that from the stage of vegetable mixture, all the other technological stages until to the final product decreased the concentration of nitrate. The total average decrease of the nitrate content was 45%. Nitrates are easily soluble in water and after adding the drinking water with low nitrate content, the overall nitrate content of food mixture is decreasing. According to the results of this study the final nitrate concentration in infant foods depended mainly on the initial nitrate content of the raw-vegetable mixture and on the amounts of the food ingredients. The imported infant food cans, purchased from retail markets, contained nitrate in lower concentrations compared to commercial infant foods produced in Estonia. It was related with the fact that in Estonian infant foods the vegetable-based ingredients percentage was higher than in imported products. In this study, the levels of nitrates in the final products ranged from 72 to 145 mg kg-1, which remains below the EU maximum permitted level, 200 mg kg-1. The infant foods storage experiments were performed after 24 h and 48 h of storage of opened infant food cans at different storage temperatures. In opened infant foods the nitrate content decreased, being the highest for the foods containing several vegetable species. Our results of analyses proved that the self-life of opened infant foods at refrigerated temperatures is at least two days. Higher nitrate concentration decrease was registered in opened infant foods stored at ambient temperatures. The nitrite contents in all infant food samples stayed below detection limit, <5 mg kg-1. Nitrate intake by 1 to 3-year-old children was found to be 26 mg per day (52% of ADI). The average daily intake of nitrates by children in the age group of 4–6 years was 30 mg (41% of ADI). The infants’ average daily intake of nitrates from consumption of vegetable-based foods was 7.8 mg (22% of ADI). During the storage of raw juices at ambient temperatures, fast decrease of nitrate levels and increase of nitrite levels was reported. Consumption of these juices means that the doses of nitrites may exceed ADI values several times.Kirje Prevalence and counts of Listeria monocytogenes and Campylobacter spp. in food and molecular characterisation of the isolates in Estonia(Estonian University of Life Sciences, 2022) Mäesaar, Mihkel; Roasto, Mati (advisor); Institute of Veterinary Medicine and Animal Sciences; Møller Nielsen, Eva (opponent)Listeria monocytogenes is a bacterial zoonotic agent and a major cause of listeriosis in humans. The invasive form of listeriosis causes severe illness and can be fatal. In the European Union (EU), 2,621 cases of listeriosis were reported in humans in 2019, with a 17.6% case fatality rate. A study carried out in 2012–2013 found that 16.8% of the 185 samples of ready-to-eat fish (RTE) products tested positive, but only one salted and sliced salmon fillet product exceeded the European Union food safety criterion of 100 CFU/g at the end of its shelf-life. Unlike L. monocytogenes, infections caused by Campylobacter jejuni are significantly more common in humans. Campylobacteriosis usually affects people with mild symptoms and is typically a self-limiting disease. In 2019, 220,682 cases of campylobacteriosis were registered in the EU, but the mortality rate per case was only 0.03% compared to listeriosis. A survey conducted in 2012 found that 35.0% of the 220 samples of fresh broiler chicken meat from Estonia, Latvia and Lithuania sold in Estonia were contaminated with campylobacters. Higher prevalence, counts and antibiotic resistance of campylobacters were associated with imported chicken broiler products. These indicators were low in fresh broiler chicken meat products of Estonian origin. The molecular methods used in the study allowed the strain of L. monocytogenes isolated from Estonian food to be associated with a multi-country outbreak of listeriosis in several European countries in 2014–2019. A retrospective survey also revealed that the same strain was already in the company's RTE fish products before the outbreak was first registered. Molecular studies also showed that the primary source of human cases of campylobacteriosis in Estonia is mainly related to poultry, including poultry meat. Systematic application of whole-genome sequencing in routine surveillance will contribute to the effectiveness of investigating food-borne outbreaks and thus to the prevention of related cases.Kirje Prevalence and counts of Listeria monocytogenes and Campylobacter spp. in food and molecular characterisation of the isolates in Estonia(Estonian University of Life Sciences, 2022) Mäesaar, Mihkel; Roasto, Mati (advisor); Institute of Veterinary Medicine and Animal Sciences; Møller Nielsen, Eva (opponent)Listeria monocytogenes is a bacterial zoonotic agent and a major cause of listeriosis in humans. The invasive form of listeriosis causes severe illness and can be fatal. In the European Union (EU), 2,621 cases of listeriosis were reported in humans in 2019, with a 17.6% case fatality rate. A study carried out in 2012–2013 found that 16.8% of the 185 samples of ready-to-eat fish (RTE) products tested positive, but only one salted and sliced salmon fillet product exceeded the European Union food safety criterion of 100 CFU/g at the end of its shelf-life. Unlike L. monocytogenes, infections caused by Campylobacter jejuni are significantly more common in humans. Campylobacteriosis usually affects people with mild symptoms and is typically a self-limiting disease. In 2019, 220,682 cases of campylobacteriosis were registered in the EU, but the mortality rate per case was only 0.03% compared to listeriosis. A survey conducted in 2012 found that 35.0% of the 220 samples of fresh broiler chicken meat from Estonia, Latvia and Lithuania sold in Estonia were contaminated with campylobacters. Higher prevalence, counts and antibiotic resistance of campylobacters were associated with imported chicken broiler products. These indicators were low in fresh broiler chicken meat products of Estonian origin. The molecular methods used in the study allowed the strain of L. monocytogenes isolated from Estonian food to be associated with a multi-country outbreak of listeriosis in several European countries in 2014–2019. A retrospective survey also revealed that the same strain was already in the company's RTE fish products before the outbreak was first registered. Molecular studies also showed that the primary source of human cases of campylobacteriosis in Estonia is mainly related to poultry, including poultry meat. Systematic application of whole-genome sequencing in routine surveillance will contribute to the effectiveness of investigating food-borne outbreaks and thus to the prevention of related cases.Kirje Source attribution of Estonian human Campylobacter spp. isolates(Eesti Maaülikool, 2025) Ivanov, Ilijana; Mäesaar, Mihkel (advisor); Takkinen, Johanna (advisor); Roasto, Mati (advisor); Chair of Veterinary Biomedicine and Food HygieneHuman campylobacteriosis remains a major foodborne gastrointestinal disease in the European Union, contributing to a global burden of approximately 2.1 million disabilityadjusted life years annually. Affecting individuals across all age groups, it poses particular risks for immunocompromised populations, where long-term complications are more likely. Campylobacter jejuni and C. coli, the primary species responsible for human infections, are prevalent in different sources. Transmission typically occurs through contaminated food or water, yet the precise mechanisms enabling bacterial survival along these pathways remain poorly understood. Accurate source attribution is essential for assessing disease risk and clarifying possible transmission routes. While microbial subtyping has become a valuable tool for source attribution, its efficacy is constrained by the availability, genotyping resolution and quality of reference data. Machine learning approaches, such as the aiSource algorithm, address this limitation by leveraging comprehensive core genome multilocus sequence typing profiles from open-access databases to predict infection sources with greater precision. Although poultry is widely recognised as the predominant source of C. jejuni infections, joint analysis of C. jejuni and C. coli may uncover additional reservoirs and transmission pathways. The present thesis confirmed poultry as the primary source of C. jejuni in Estonia, followed by cattle, aligning with prior studies. For C. coli, novel insights highlight sheep and wild birds as possible emerging sources, suggesting that underrepresented reservoirs may contribute significantly to human campylobacteriosis in Estonia. The novel genotype ST11001, detected globally for the first time in humans, showed lower than average attribution probability, likely due to its absence from the machine learning algorithm’s training dataset, emphasising the need for continuous model updates to account for genomic diversity and data gaps. These results indicate the need for expanded sampling, particularly for C. coli, and refined machine learning models to enhance source attribution accuracy and inform targeted infection prevention strategies.