The spoilage flora of vacuum-packaged, sodium nitrite or potassium nitrate treated, cold-smoked rainbow trout stored at 4°C or 8°C

http://www.elsevier.nl/locate/01681605The spoilage flora of vacuum-packaged, salted, cold-smoked rainbow trout fillets, with or without the addition of nitrate or nitrite, stored at 4°C and 8°C, was studied. Of 620 isolates, lactic acid bacteria were the major fraction (76%), predominating in all samples of spoiled product. However, the phenotypical tests used were insufficient to identify the lactic acid bacteria to the species level. Gram-positive, catalase-positive cocci, Gram-negative, oxidase-negative rods and Gram-negative, oxidase-positive rods were found in 6%, 16% and 2% of the samples, respectively. Of 39 Gram-positive, catalase-positive cocci, 29 were identified as staphylococci and 10 as micrococci. Eighty-five isolates were found to belong to the family Enterobacteriaceae, with 45 of those being Serratia plymuthica. Eleven isolates from the nitrate treated samples stored at 8°C were identified as Pseudomonas aeruginosa. The occurrence of P. aeruginosa and staphylococci in the nitrate-containing samples, stored at 8°C, may cause problems with respect to the safety of the product. The types of lactic acid and other bacteria in the spoilage flora were generally reduced by the addition of nitrate or nitrite to fillets

Antibacterial activity of different organic honeys against food pathogenic bacterium Clostridium perfringens

Clostridium perfringens is one of the most common causes of food poisonings and is known to cause human and animal diseases. It has been reported that C. perfringens has developed resistance to antibiotics. Antimicrobial properties of honey have been studied in order to confirm its action as a potential antimicrobial agent and also as a potential food preservative through inactivation, growth delay or growth prevention of food pathogenic microorganisms. This study had two different parts related on virulence of C. perfringens. In the first part of the study antimicrobial activity of five multifloral organic honeys from different parts of Finland and one multifloral honey originated from Argentina and Hungary were investigated against C. perfringens. Honeys were tested at the concentrations of 50% (w/v), 25% (w/v), 20% (w/v), 15% (w/v) and 10% (w/v). For the antimicrobial assessment a disc diffusion method was used and zone of inhibition was expressed as diameter. The minimum concentrations (minimum inhibitory concentration, MIC) needed for inhibition of bacterial growth were determined for honeys showing activity in dilutions of 50%. Four of the studied honeys showed good inhibitory activity (diameter >8 mm) compared to control sugar solution (diameter of 6.1 ± 1.5) against C. perfringens at the concentration of 50 % (w/v). All the active honeys were of Finnish origin. The broadest zone of inhibition was induced by North Carelien multifloral organic honey with willow herb as the main floral source (referred here as F) (diameter of 14,3 mm ± 0.6), followed by other North Carelien multifloral organic honey (diameter of 11 mm ± 2) with clover as the main floral source (referred here as E). In terms of MIC values North Carelien organic honey F was also the most efficient honey against C. perfringens and showed moderate antibacterial activity (diameter of 7-8 mm) even at 10% (w/v). The other active honeys showed moderate inhibitory activity in the dilution of 15%. To our knowledge this is the first report on the antimicrobial activity of organic honeys and antimicrobial activity of honey against C. perfringens. (Oinaala et al 2015) In the second part of the work C. perfringens isolates from healthy broilers and from broilers suffering from necrotic enteritis (NE) were analyzed by polymerase chain reaction (PCR) method in order to determine the presence of gene coding the NE toxin B (NetB), a novel toxin that has been strongly associated with the pathogenesis of NE. The netB toxin gene was detected in 30% isolates from broilers with necrotic enteritis and in 32.5% isolates from healthy broilers. In this study the presence of netB gene gives not enough information for predicting the virulence of C. perfringens isolates, thus, further investigations are needed

A longitudinal study of Campylobacter distribution in a turkey

Background: Campylobacter is the most common cause of bacterial enteritis worldwide. Handling and eating of contaminated poultry meat has considered as one of the risk factors for human campylobacteriosis.Campylobacter contamination can occur at all stages of a poultry production cycle. The objective of this study was to determine the occurrence of Campylobacter during a complete turkey production cycle which lasts for 1,5 years of time. For detection of Campylobacter, a conventional culture method was compared with a PCR method. Campylobacter isolates from different types of samples have been identified to the species level by a multiplex PCR assay. Methods: Samples (N = 456) were regularly collected from one turkey parent flock, the hatchery, six different commercial turkey farms and from 11 different stages at the slaughterhouse. For the detection of Campylobacter, a conventional culture and a PCR method were used. Campylobacter isolates (n = 143) were identified to species level by a multiplex PCR assay. Results: No Campylobacter were detected in either the samples from the turkey parent flock or from hatchery samples using the culture method. PCR detected Campylobacter DNA in five faecal samples and one fluff and eggshell sample. Six flocks out of 12 commercial turkey flocks where found negative at the farm level but only two were negative at the slaughterhouse. Conclusion: During the brooding period Campylobacter might have contact with the birds without spreading of the contamination within the flock. Contamination of working surfaces and equipment during slaughter of a Campylobacter positive turkey flock can persist and lead to possible contamination of negative flocks even after the end of the day's cleaning and desinfection. Reduction of contamination at farm by a high level of biosecurity control and hygiene may be one of the most efficient ways to reduce the amount of contaminated poultry meat in Finland. Due to the low numbers of Campylobacter in the Finnish turkey production chain, enrichment PCR seems to be the optimal detection method here

A longitudinal study of Campylobacter distribution in a turkey production chain

Background: Campylobacter is the most common cause of bacterial enteritis worldwide. Handling and eating of contaminated poultry meat has considered as one of the risk factors for human campylobacteriosis.Campylobacter contamination can occur at all stages of a poultry production cycle. The objective of this study was to determine the occurrence of Campylobacter during a complete turkey production cycle which lasts for 1,5 years of time. For detection of Campylobacter, a conventional culture method was compared with a PCR method. Campylobacter isolates from different types of samples have been identified to the species level by a multiplex PCR assay. Methods: Samples (N = 456) were regularly collected from one turkey parent flock, the hatchery, six different commercial turkey farms and from 11 different stages at the slaughterhouse. For the detection of Campylobacter, a conventional culture and a PCR method were used. Campylobacter isolates (n = 143) were identified to species level by a multiplex PCR assay. Results: No Campylobacter were detected in either the samples from the turkey parent flock or from hatchery samples using the culture method. PCR detected Campylobacter DNA in five faecal samples and one fluff and eggshell sample. Six flocks out of 12 commercial turkey flocks where found negative at the farm level but only two were negative at the slaughterhouse. Conclusion: During the brooding period Campylobacter might have contact with the birds without spreading of the contamination within the flock. Contamination of working surfaces and equipment during slaughter of a Campylobacter positive turkey flock can persist and lead to possible contamination of negative flocks even after the end of the day's cleaning and desinfection. Reduction of contamination at farm by a high level of biosecurity control and hygiene may be one of the most efficient ways to reduce the amount of contaminated poultry meat in Finland. Due to the low numbers of Campylobacter in the Finnish turkey production chain, enrichment PCR seems to be the optimal detection method here

Genome analysis of Clostridium perfringens isolates from healthy and necrotic enteritis infected chickens and turkeys

Objective: Clostridium perfringens causes gastrointestinal diseases in both humans and domestic animals. Type A strains expressing the NetB toxin are the main cause of necrotic enteritis (NE) in chickens, which has remarkable impact on animal welfare and production economy in the international poultry industry. Three pathogenicity loci NELoc-1, -2 and -3 and a collagen adhesion gene cnaA have been found to be associated with NE in chickens, whereas the presence of these has not been investigated in diseased turkeys. The purpose was to investigate the virulence associated genome content and the genetic relationship among 30 C. perfringens isolates from both healthy and NE infected chickens and turkeys, applying whole-genome sequencing. Results: NELoc-1, -3, netB and cnaA were significantly associated with NE isolates from chickens, whereas only NELoc-2 was commonly observed in both diseased turkeys and chickens. A putative collagen adhesion gene that encodes a von Willebrand Factor (vWF) domain was identified in all diseased turkeys and designated as cnaD. The phylogenetic analysis based on single nucleotide polymorphisms showed that the isolates generally were not closely related. These results indicate that virulence factors and pathogenicity loci associated with NE in chickens are not important to the same extent in diseased turkeys except for NELoc-2. A putative collagen adhesion gene which potentially could be of importance in regard to the NE pathogenesis in turkeys was identified and need to be further investigated. Thus, the pathogenesis of NE in turkeys appears to be different from that of broiler chickens

Spread of avian pathogenic Escherichia coli ST117 O78:H4 in Nordic broiler production

BACKGROUND: Escherichia coli infections known as colibacillosis constitute a considerable challenge to poultry farmers worldwide, in terms of decreased animal welfare and production economy. Colibacillosis is caused by avian pathogenic E. coli (APEC). APEC strains are extraintestinal pathogenic E. coli and have in general been characterized as being a genetically diverse population. In the Nordic countries, poultry farmers depend on import of Swedish broiler breeders which are part of a breeding pyramid. During 2014 to 2016, an increased occurrence of colibacillosis on Nordic broiler chicken farms was reported. The aim of this study was to investigate the genetic diversity among E. coli isolates collected on poultry farms with colibacillosis issues, using whole genome sequencing. METHODS: Hundred and fourteen bacterial isolates from both broilers and broiler breeders were whole genome sequenced. The majority of isolates were collected from poultry with colibacillosis on Nordic farms. Subsequently, comparative genomic analyses were carried out. This included in silico typing (sero- and multi-locus sequence typing), identification of virulence and resistance genes and phylogenetic analyses based on single nucleotide polymorphisms. RESULTS: In general, the characterized poultry isolates constituted a genetically diverse population. However, the phylogenetic analyses revealed a major clade of 47 closely related ST117 O78:H4 isolates. The isolates in this clade were collected from broiler chickens and breeders with colibacillosis in multiple Nordic countries. They clustered together with a human ST117 isolate and all carried virulence genes that previously have been associated with human uropathogenic E. coli. CONCLUSIONS: The investigation revealed a lineage of ST117 O78:H4 isolates collected in different Nordic countries from diseased broilers and breeders. The data indicate that the closely related ST117 O78:H4 strains have been transferred vertically through the broiler breeding pyramid into distantly located farms across the Nordic countries. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12864-016-3415-6) contains supplementary material, which is available to authorized users

Behavior under vague standards : evidence from the laboratory

Doctrinal lawyers strive to reduce legal uncertainty based on the premise that difficult to predict legal consequences discourage socially desirable activities. Contributions from the economic theory of law suggest that increasing legal uncertainty can be socially beneficial. We test in an innovative laboratory experiment whether increasing the variability of an exogenous choice threshold (legal standard) increases or reduces socially desirable behavior. The results indicate a U-shaped relationship between increases in variability and activity choices: increases in variability first induce lower than optimal choices under an efficient standard (overcompliance), but eventually lead to greater than optimal choices under an efficient standard (undercompliance). We also find that overcompliance arises only under low degrees of standard variability. Moreover, increasing variability gradually crowds-out compliant choices. Finally, in the experiment minimal variability of the legal standard induces erratic individual behavior beyond socially satisfactory levels such that the standard loses its coordination function

Defensive behavior in principal-agent relationships

In this doctoral thesis, I explore how vague behavioural or legal standards affect agents decision-making. In particular, I test the extent to which agents engage in defensive behaviour in order to signal a professional qualification or in the face of vague legal standards. I measure defensive behaviour as the extent to which agents make less than efficient decisions for their principals in order to increase the probability of complying with the vague standard. This behaviour is of great interest as it is associated with vast costs to principals and to society as a whole.I find that defensive behaviour is not easily eroded and very sensitive to legal standard vagueness. Policy makers seeking to minimize defensive behaviour face a complex task in which the reduction of legal uncertainty or financial liability is not always an effective strategy. All three papers are based on economic experiments