Homologous recombination between bacterial strains is theoretically capable of preventing the separation of daughter clusters, and producing cohesive clouds of genotypes in sequence space. However, ...numerous barriers to recombination are known. Barriers may be essential such as adaptive incompatibility, or ecological, which is associated with the opportunities for recombination in the natural habitat. Campylobacter jejuni is a gut colonizer of numerous animal species and a major human enteric pathogen. We demonstrate that the two major generalist lineages of C. jejuni do not show evidence of recombination with each other in nature, despite having a high degree of host niche overlap and recombining extensively with specialist lineages. However, transformation experiments show that the generalist lineages readily recombine with one another in vitro. This suggests ecological rather than essential barriers to recombination, caused by a cryptic niche structure within the hosts.
Anisakiasis is an emerging zoonosis caused by the fish parasitic nematode Anisakis. Spain appears to have the highest reported incidence in Europe and marinated anchovies are recognised as the main ...food vehicle. Using data on fishery landings, fish infection rates and consumption habits of the Spanish population from questionnaires, we developed a quantitative risk assessment (QRA) model for the anchovy value chain. Spaniards were estimated to consume on average 0.66 Anisakis per untreated (non-frozen) raw or marinated anchovy meal. A dose-response relationship was generated and the probability of anisakiasis was calculated to be 9.56 × 10
per meal, and the number of annual anisakiasis cases requiring medical attention was predicted between 7,700 and 8,320. Monte Carlo simulations estimated post-mortem migration of Anisakis from viscera to flesh increases the disease burden by >1000% whilst an education campaign to freeze anchovy before consumption may reduce cases by 80%. However, most of the questionnaire respondents who ate untreated meals knew how to prevent Anisakis infection. The QRA suggests that previously reported figures of 500 anisakiasis per year in Europe is a considerable underestimate. The QRA tool can be used by policy makers and informs industry, health professionals and consumers about this underdiagnosed zoonosis.
A nationwide multi-locus sequence typing (MLST) survey was implemented to analyze patterns of host association among
Campylobacter jejuni and
Campylobacter coli isolates from clinical disease in ...Scotland (July 2005–September 2006), food animals (chickens, cattle, sheep, pigs and turkey), non-food animals (wild birds) and the environment. Sequence types (STs) were determined for 5247 clinical isolates and 999 from potential disease sources (augmented with 2420 published STs). Certain STs were over represented among particular sample sets/host groups. These host-associated STs were identified for all sample groups in both
Campylobacter species and host associated clonal complexes (groups of related STs) were characterized for
C. jejuni. Some genealogical lineages were present in both human disease and food animal samples. This provided evidence for the relative importance of different infection routes/food animal sources in human disease. These results show robust associations of particular genotypes with potential infection sources supporting the contention that contaminated poultry is a major source of human disease.
Background. Campylobacter species cause a high proportion of bacterial gastroenteritis cases and are a significant burden on health care systems and economies worldwide; however, the relative ...contributions of the various possible sources of infection in humans are unclear. Methods. National-scale genotyping of Campylobacter species was used to quantify the relative importance of various possible sources of human infection. Multilocus sequence types were determined for 5674 isolates obtained from cases of human campylobacteriosis in Scotland from July 2005 through September 2006 and from 999 Campylobacter species isolates from 3417 contemporaneous samples from potential human infection sources. These data were supplemented with 2420 sequence types from other studies, representing isolates from a variety of sources. The clinical isolates were attributed to possible sources on the basis of their sequence types with use of 2 population genetic models, STRUCTURE and an asymmetric island model. Results. The STRUCTURE and the asymmetric island models attributed most clinical isolates to chicken meat (58% and 78% of Campylobacter jejuni and 40% and 56% of Campylobacter coli isolates, respectively), identifying it as the principal source of Campylobacter infection in humans. Both models attributed the majority of the remaining isolates to ruminant sources, with relatively few isolates attributed to wild bird, environment, swine, and turkey sources. Conclusions. National-scale genotyping was a practical and efficient methodology for the quantification of the contributions of different sources to human Campylobacter infection. Combined with the knowledge that retail chicken is routinely contaminated with Campylobacter, these results are consistent with the view that the largest reductions in human campylobacteriosis in industrialized countries will come from interventions that focus on the poultry industry.
Nematodes of the genus Anisakis parasitize many commercial fish species and are responsible for a fish-borne zoonosis (anisakiasis) and allergic reactions. Anisakis can also cause consumer distrust ...in fishery products and economic losses to the fish industry.
We review current socioeconomic, legislative, risk management and human health problems caused by the occurrence of Anisakis in fishery products and discuss possible strategies to mitigate them.
Visual inspection (and candling) of fishery products as required by EU legislation is not efficient for parasite detection. Consequently, visible (and non-visible) Anisakis reach the market and may be detected (and eaten) by consumers. Marine fish appears to be the only industrial food product that is at high risk of containing parasites when placed on the market.
Anisakiasis and allergy to Anisakis are hidden, underestimated emerging zoonoses worldwide. There is a need to better understand the impact of these zoonoses on individual health and particularly exposed human populations, and to assess the risk posed by Anisakis allergens in fishery products. Quantitative risk assessment (QRA) is identified as an appropriate methodology as it estimates the risk from fishing ground to human disease.
Improvements in parasite control legislation and procedures (e.g. establishment of research-based and standardized parasite detection methodologies, appropriate sampling strategies, development of non-destructive methods for detection and removal of nematodes from fish products), suitable for use by seafood businesses, are recommended to improve protection of consumers and to protect the industry by minimizing Anisakis-associated economic losses. QRA may help to provide the scientific basis for improved food safety legislation and strategies to reduce the risk of anisakiasis/allergy in humans.
•Anisakid control measures implemented by seafood businesses are not efficient.•Visible Anisakis reach the fish market and may be detected and eaten by consumers.•The health risk posed by Anisakis allergens in fish products needs to be assessed.•We need to better understand the impacts of anisakiasis and Anisakis allergy.•Improved food safety legislation and procedures are needed; QRA methods may help.
Hybridization between distantly related organisms can facilitate rapid adaptation to novel environments, but is potentially constrained by epistatic fitness interactions among cell components. The ...zoonotic pathogens Campylobacter coli and C. jejuni differ from each other by around 15% at the nucleotide level, corresponding to an average of nearly 40 amino acids per protein‐coding gene. Using whole genome sequencing, we show that a single C. coli lineage, which has successfully colonized an agricultural niche, has been progressively accumulating C. jejuni DNA. Members of this lineage belong to two groups, the ST‐828 and ST‐1150 clonal complexes. The ST‐1150 complex is less frequently isolated and has undergone a substantially greater amount of introgression leading to replacement of up to 23% of the C. coli core genome as well as import of novel DNA. By contrast, the more commonly isolated ST‐828 complex bacteria have 10–11% introgressed DNA, and C. jejuni and nonagricultural C. coli lineages each have <2%. Thus, the C. coli that colonize agriculture, and consequently cause most human disease, have hybrid origin, but this cross‐species exchange has so far not had a substantial impact on the gene pools of either C. jejuni or nonagricultural C. coli. These findings also indicate remarkable interchangeability of basic cellular machinery after a prolonged period of independent evolution.
We examined whole-genome-sequenced Campylobacter jejuni and C. coli from 2012-2015 isolated from birds and human stool samples in North East Scotland for the presence of antimicrobial resistance ...genes. We found that sequence type (ST) 5136 (clonal complex 464) was the most prevalent multidrug-resistant strain of C. jejuni exclusively associated with poultry host reservoirs and recovered from human cases of campylobacteriosis. Tetracycline resistance in ST5136 isolates was due to a tet(O/32/O) mosaic gene, ampicillin resistance was conferred by G → T transversion in the -10 promoter region of bla
, fluoroquinolone resistance was due to C257T change in gyrA, and aminoglycoside resistance was conferred by aac. Whole-genome analysis showed that the strain ST5136 evolved from ST464. The nationwide emergence of ST5136 was probably due to stepwise acquisition of antimicrobial resistance genes selected by high use of β-lactam, tetracycline, fluoroquinolone, and aminoglycoside classes of drugs in the poultry industry.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Salmonella is a key human pathogen worldwide, most often associated with food poisoning incidences. There is a small number of predominant serotypes found in human cases. The role of exposure in the ...epidemiology of
Salmonella can be explained using dose–response assessment both for infection and acute enteric illness. Dose–response studies are traditionally based on human challenge experiments but an alternative is to use outbreak data. Such data were collected from the published literature which included estimates of the dose ingested and the attack rate. Separate dose–response models for infection and illness given infection were fitted using a multi-level statistical framework. These models incorporated serotype and susceptibility as categorical covariates, and adjusted for heterogeneity in exposure. The results indicate that both the risk of infection and the risk of illness given infection increase with dose. The dose–response model incorporating data from all outbreaks had an infection ID50 of 7 CFU's and illness ID50 of 36 CFUs. This is indicative of much higher infectivity and pathogenicity compared with feeding studies of healthy human volunteers with laboratory adapted strains. No differences were found in the outbreak models between serotypes and susceptibility categories. However, for serotypes other than
S. Enteritidis or
S. Typhimurium, results indicate that a minor proportion of individuals exposed will not fall ill even at high doses. The dose–response relations indicate that outbreaks are associated with higher doses making it more likely to have a higher attack rate. Applications of the dose–response model in outbreak situations where either dose or attack rate is missing were successfully used to clarify the epidemiology. Finally, the dose–response models described here can be readily used in quantitative microbiological risk assessment to predict human infection and illness rates. A simple Excel spreadsheet implementing the model has been prepared and is available from the authors.
The impact of the extent of testing infectious individuals on suppression of COVID-19 is illustrated from the early stages of outbreaks in Germany, the Hubei province of China, Italy, Spain and the ...UK. The predicted percentage of untested infected individuals depends on the specific outbreak but we found that they typically represent 60-80% of all infected individuals during the early stages of the outbreaks. We propose that reducing the underlying transmission from untested cases is crucial to suppress the virus. This can be achieved through enhanced testing in combination with social distancing and other interventions that reduce transmission such as wearing face masks. Once transmission from silent carriers is kept under control by these means, the virus could have been fully suppressed through fast isolation and contact tracing of tested cases.
Bacterial populations can display high levels of genetic structuring but the forces that influence this are incompletely understood. Here, by combining modelling approaches with multilocus sequence ...data for the zoonotic pathogen Campylobacter, we investigated how ecological factors such as niche (host) separation relate to population structure. We analysed seven housekeeping genes from published C. jejuni and C. coli isolate collections from a range of food and wild animal sources as well as abiotic environments. By reconstructing genetic structure and the patterns of ancestry, we quantified C. jejuni host association, inferred ancestral populations, investigated genetic admixture in different hosts and determined the host origin of recombinant C. jejuni alleles found in hybrid C. coli lineages. Phylogenetically distinct C. jejuni lineages were associated with phylogenetically distinct wild birds. However, in the farm environment, phylogenetically distant host animals shared several C. jejuni lineages that could not be segregated according to host origin using these analyses. Furthermore, of the introgressed C. jejuni alleles found in C. coli lineages, 73% were attributed to genotypes associated with food animals. Our results are consistent with an evolutionary scenario where distinct Campylobacter lineages are associated with different host species but the ecological factors that maintain this are different in domestic animals such that phylogenetically distant animals can harbour closely related strains.
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