Campylobacter Jejuni Strains Research Articles

Expression of the Campylobacter jejuni FliD protein and its reaction to chicken sera.

Campylobacter is a leading causative pathogen of acute bacterial gastroenteritis among humans. Contaminated chicken products are regarded as major sources of human infection. The flagellar capping protein (FliD), which plays important roles in colonization and adhesion to the mucosal surface of chicken ceca, is conserved among Campylobacter jejuni strains. In this study, the recombinant C. jejuni FliD protein was expressed, purified and used as a coated protein to examine the prevalence of C. jejuni antibodies in chickens. The anti-FliD antibody was prevalent among chicken serum samples taken from different farms in the diverse regions of Jiangsu province by using enzyme-linked immunosorbent assay. The Campylobacter antibody was present in culture-negative chickens. No strong dose-response relationships were observed between serum FliD antibody levels and Campylobacter cultural status. These results provide a basis for further evaluating FliD as a vaccine candidate for broiler chickens or for examining host-C. jejuni interactions, with implications for improving food safety.

Formation of the Resistance of Campylobacter jejuni to Macrolide Antibiotics.

The tendency to the formation of macrolide resistance in campylobacteriosis pathogens is considered as a serious threat to public health due to ubiquity of campylobacter strains resistant to a wide range of antibiotics, primarily fluoroquinolones and tetracyclines. To assess the prevalence of resistant Campylobacter spp., we performed screening for macrolide sensitivity among 40 Campylobacter jejuni strains isolated from raw milk, poultry product, and washings from the equipment of the poultry processing plants. Phenotypic resistance to erythromycin, the most popular antibiotic for the treatment of campylobacteriosis, was revealed in 27.5% C. jejuni strains; 10% strains were resistant to azithromycin. The search and selection for gene markers of Campylobacter resistance to macrolides was performed. It was found that the resistance of C. jejuni to erythromycin is realized mainly via synthesis of proteins that protect ribosomes (the presence of coding sequences was detected in 45% of the studied strains) and the transmembrane pump mechanism (efflux pump CmeABC genes were found in 36% isolates); both mechanisms are transmissible. Chromosomal mutations in the 23S rRNA sequence detected in 18% strains seem to play a less significant role.

Genome-Scale Metabolic Model Driven Design of a Defined Medium for Campylobacter jejuni M1cam.

Campylobacter jejuni, the most frequent cause of food-borne bacterial gastroenteritis, is a fastidious organism when grown in the laboratory. Oxygen is required for growth, despite the presence of the metabolic mechanism for anaerobic respiration. Amino acid auxotrophies are variably reported and energy metabolism can occur through several electron donor/acceptor combinations. Overall, the picture is one of a flexible, but vulnerable metabolism. To understand Campylobacter metabolism, we have constructed a fully curated, metabolic model for the reference organism M1 (our variant is M1cam) and validated it through laboratory experiments. Our results show that M1cam is auxotrophic for methionine, niacinamide, and pantothenate. There are complete biosynthesis pathways for all amino acids except methionine and it can produce energy, but not biomass, in the absence of oxygen. M1cam will grow in DMEM/F-12 defined media but not in the previously published Campylobacter specific defined media tested. Using the model, we identified potential auxotrophies and substrates that may improve growth. With this information, we designed simple defined media containing inorganic salts, the auxotrophic substrates, L-methionine, niacinamide, and pantothenate, pyruvate and additional amino acids L-cysteine, L-serine, and L-glutamine for growth enhancement. Our defined media supports a 1.75-fold higher growth rate than Brucella broth after 48 h at 37°C and sustains the growth of other Campylobacter jejuni strains. This media can be used to design reproducible assays that can help in better understanding the adaptation, stress resistance, and the virulence mechanisms of this pathogen. We have shown that with a well-curated metabolic model it is possible to design a media to grow this fastidious organism. This has implications for the investigation of new Campylobacter species defined through metagenomics, such as C. infans.

Draft Genome Sequences of Campylobacter jejuni Strains Isolated from Poultry.

Four wild-type Campylobacter jejuni strains isolated from the cecal contents of broiler chickens were sequenced. The average genome size was 1,622,170 bp, with 1,667 to 1,761 coding sequences and 47 to 51 RNAs. Multiple genes encoding motility, intestinal colonization, toxin production, stress tolerance, and multidrug resistance were present in all the strains.

Draft Genome Sequences of Multidrug-Resistant Campylobacter jejuni Strains Isolated from Chickens in Central China.

Campylobacter jejuni is a major foodborne pathogen that plays an important role in spreading drug resistance. We report the draft genome sequences of two multidrug-resistant C. jejuni isolates which contained similar mutations in the CmeR box. This will improve the understanding of C. jejuni antimicrobial resistance and genetic characteristics.

Campylobacter in Street Vended Poultry Meat Meals and its Public Health Hazard

In this study, a total of (250) samples were collected from different ready to eat poultry meat products, (50) samples from each of (Chicken Bannae, Chicken Shawarma, Chicken Phaheta, Chicken Shesh kabab, Chicken Zinger) from vending sites and restaurants of different localities of different level of hygienic measures in Cairo governorate to detect and identify the Campylobacter species bacteriologically by direct plating and selective enrichment methods and by PCR. As regards to the Bacteriological examination of (250) collected ready to eat poultry products meal, the obtained results revealed the isolation of Campylobacter spp. from (8) samples with a prevalence rate reached (3.2%) by studding the morphological identification on the selective culture media and microscopically identification as well as the biochemical reactions. On the other hand, the all isolated strains proved to be C. jejuni by molecular identification (PCR assay) using specific primers. For experimental challenge, the isolated strains of Campylobacter jejuni were cultured to investigate the role of cross - contamination in disseminating campylobacter from raw poultry within a food service operation specializing in poultry dishes. Samples were collected weekly from environmental surfaces and various kitchen surfaces used at different stages of the preparation process from a retail poultry food service operation. The obtained results revealed that with use of an inoculum of 107 cells, viable C. jejuni could not be recovered from the stainless steel surface after 1 hrs. of drying. Also, Campylobacter spp. were not detected in any of the 125 restaurant samples collected The results indicated that as few as 100 Campylobacter cells could be detected if sampling was done within 45 min of inoculation; however, despite the reported high prevalence of Campylobacter spp. in ready to eat poultry meal, this organism was not detected on surfaces within a kitchen of a restaurant specializing in Poultry dishes. This inability to detect Campylobacters may be related to routine cleaning of preparation surfaces, adequate preparation and storage of foodstuffs, good worker hygiene, and physical separation of raw foods from cooked foods, limiting cross-contamination. It is also likely that the lack of Campylobacters in samples from this high-volume retail food service operation may also be attributed to the sensitivity of Campylobacter spp. to drying conditions.

Fate of Salmonella ssp., Listeria monocytogenes, and Campylobacter ssp., During Fermentation and Drying of Duck Salami

ObjectivesCreating artisanal, dry salami products is an increasing trend for charcuterie companies in the United States. These raw, ready-to-eat products are required by USDA-FSIS to have a scientifically valid HACCP system addressing relevant biological hazards. To our knowledge, no literature exists for the validation (at least a 5 Log10 reduction of pathogens per FSIS) of salami products containing duck. Therefore, an experiment was designed to validate the safety of duck salami. The objectives of this study were to validate the safety of fermented and dried duck salami and to investigate if a duck salami manufacturing processes could achieve a 5 LOG10 (CFU/g) reduction of Salmonella ssp., Listeria monocytogenes, and Campylobacter ssp.Materials and MethodsDuck trim and pork belly (70% duck trim, 30% pork belly) were placed in a mixed culture bath approximating three liters. The culture bath was made by growing individually and then combining three strains each of Salmonella spp. and Listeria monocytogenes, two strains of Campylobacter jejuni, and one strain of Campylobacter coli. After inoculation, meat was air dried (30 min @ 23°C), tumbled with one liter of 2.5% BeefxideÒantimicrobial treatment (lactic and citric acid and hydrogen peroxide), and placed in a walk-in cooler (2–4°C) overnight. After inoculation and antimicrobial treatment (∼24 h), the meat was ground (6mm grinding plate) and seasoned with salt (2.5%), cure (NaNO3 & NaNO2), spices, and starter culture. The ground duck-pork mixture was stuffed into 55mm collagen casings, fermented for 48 h (23°C, 95% rH), and dried (12°C, 75% rH) to ∼45% weight loss (approx. 5 wk). Salamis were then vacuum packaged and stored at 23°C (approx. 4 wk). Three independent replications were conducted, and pathogen concentrations, pH, and water activity (aw) were analyzed at Days 0, 1, 2, 3, 5, 10, and weekly until Day 66 during each replication. Critical parameters for production included a final pH less than 5.3 and final aw less than 0.90.ResultsA 5 LOG10(CFU/g) reduction was achieved for all three pathogens. Salmonella achieved a 5.47 LOG10(CFU/g) (p < 0.0001) reduction by Day 38, Listeria monocytogenes achieved a 5.20 LOG10(CFU/g) (p < 0.0001) reduction by Day 59, and Campylobacter achieved a 6.85 LOG10(CFU/g) (p < 0.0001) reduction by Day 45. Final reductions of 7.03 (p < 0.0001), 5.90 (p < 0.0001), and 7.19 (p < 0.0001) LOG10(CFU/g) were achieved for Salmonella spp., Listeria monocytogenes, and Campylobacter spp., respectively. During the entire fermentation and drying process, populations of each species never increased by more than 1 LOG10 (CFU/cm2). A final pH of 5.11 and a final aw of 0.81 were also achieved.ConclusionThe results of this study indicate that the parameters used to ferment and dry this product are able to achieve a 5 LOG10 (CFU/g) reduction of each pathogen to validate the safe production of duck salami.

Identification of Potent Vaccine Candidates Against Campylobacter jejuni Using Immunoinformatics Approach

Infection from Campylobacter jejuni causes intense enteritis with diarrhea, fever and abdominal pain. The peptide-based vaccine could be the best way to deal with the immune response especially when antibiotic resistance is increasing in bacteria. In this study, Vaxign Server was used to predict the vaccine targets by computing proteome of diarrheagenic Campylobacter jejuni strain NCTC 11168 using default parameters. NetMHC II 2.3 server and Vaxijen tool were used to screen epitopes from protein and to identify the most antigenic epitopes binding with MHC class II molecules, respectively. Three potent T cell epitopes YFYGLAGGG, PFIMFSMLM and YIILNNFKI were screened binding with HLA-DRB1*10:01, HLA-DRB1*01:03, HLA-DRB1*04:01 and HLA-DRB1*07:01 MHC class II alleles, respectively. PepstrMod and Swiss-Model server were used to build a 3D structure model of epitopes and alleles, respectively. Identified epitopes were further docked with HLA alleles using AutoDock Vina tool to confirm binding ability. The epitopes YFYGLAGGG and PFIMFSMLM had a binding affinity of − 6.3 kcal/mol and − 6.1 kcal/mol with HLA-DRB1*10:01 and HLA-DRB1*01:03 alleles, respectively. Epitope YIILNNFKI had binding energy − 6.1 kcal/mol with two alleles HLA-DRB1*04:01 and HLA-DRB1*07:01. The predicted epitope-allele docked complex structure was optimized using molecular dynamics simulation and stability of complex structure was evaluated. These predicted epitopes were found to cover a maximum number of populations coverage in India as well as worldwide. Therefore, these epitopes had the most potential to induce T cell-mediated immune response and potent vaccine candidates against Campylobacter jejuni after testing by experimental study.

Tolerance to stress conditions associated with food safety in Campylobacter jejuni strains isolated from retail raw chicken

Campylobacter jejuni is a microaerophilic foodborne pathogen that is sensitive to stress conditions. However, it is not yet understood how this stress-sensitive pathogen may cause a significant number of cases of human gastroenteritis worldwide. In this study, we examined stress tolerance in 70 C. jejuni strains isolated from retail chicken under several stress conditions related to food safety. Compared to oxygen-sensitive (OS) strains of C. jejuni, C. jejuni strains with increased aerotolerance, such as hyper-aerotolerant (HAT) and aerotolerant (AT) strains, were more tolerant to peracetic acid, refrigeration and freeze-thaw stresses. However, the levels of thermotolerance and hyper-osmotolerance were not associated with the aerotolerance level of C. jejuni. The HAT and AT strains of C. jejuni exhibited significantly increased activities of catalase and superoxide dismutase (SOD), compared to the OS strains. Consistently, the HAT and AT strains were highly tolerant to oxidants, such as hydrogen peroxide, cumene hydroperoxide and menadione, compared to the OS strains. The AT and HAT strains that were tolerant to stresses, particularly peracetic acid and refrigeration, predominantly belonged to multilocus sequence typing (MLST) clonal complex (CC)-21. This study shows that oxidative stress resistance plays a role in determining the differential level of aerotolerance in C. jejuni and that AT and HAT strains of C. jejuni are more tolerant to oxidants and low temperatures than OS strains.

Epidemiological characteristics and antibiotic resistance of Campylobacter spp. among diarrhea outpatients in Shanghai, 2013-2016

Objective: To understand the epidemiological characteristics and antibiotic resistance profiles of Campylobacter spp. in Shanghai from 2013 to 2016. Methods: Stool samples collected from diarrhea outpatients were cultured for Campylobacter spp., using the membrane filter method in 23 hospitals under the sentinel programs, from 2013 to 2016. All the strains were identified by biochemical tests and PCR. Broth microdilution method was used to investigate the antibiotic resistance of 179 Campylobacter spp. strains that including azithromycin, ciprofloxacin, erythromycin, gentamicin, tetracycline, nalidixic acid, telycin, klinthromycin and flurbenicol. Results: A total of 179 Campylobacter spp. strains were isolated from 10 444 stool samples (1.7%). Campylobacter jejuni and Campylobacter coli appeared as the predominant ones (94.4% and 5.6%). The incidence rate was higher in children than that in adults, with peaks of infections mainly from April to June and October to December. Campylobacter jejuni strains seemed highly resistant to ciprofloxacin (96.4%), tetracycline (83.4%) and nalidixic acid (81.7%). The resistant rates appeared higher on Campylobacter coli strains that isolated from patients. Some strains were resistant to multi-drugs. Conclusions: Campylobacter spp. seemed one of the important pathogens that isolated from outpatients with diarrhea, in Shanghai. Both age and season related characteristics of Campylobacter spp. were seen. Campylobacter spp. isolated from patients was highly resistant to ciprofloxacin, tetracycline and nalidixic acid.

Domestication of Campylobacter jejuni NCTC 11168.

Reference and type strains of well-known bacteria have been a cornerstone of microbiology research for decades. The sharing of well-characterized isolates among laboratories has run in parallel with research efforts and enhanced the reproducibility of experiments, leading to a wealth of knowledge about trait variation in different species and the underlying genetics. Campylobacter jejuni strain NCTC 11168, deposited at the National Collection of Type Cultures in 1977, has been adopted widely as a reference strain by researchers worldwide and was the first Campylobacter for which the complete genome was published (in 2000). In this study, we collected 23 C . jejuni NCTC 11168 reference isolates from laboratories across the UK and compared variation in simple laboratory phenotypes with genetic variation in sequenced genomes. Putatively identical isolates, identified previously to have aberrant phenotypes, varied by up to 281 SNPs (in 15 genes) compared to the most recent reference strain. Isolates also display considerable phenotype variation in motility, morphology, growth at 37 °C, invasion of chicken and human cell lines, and susceptibility to ampicillin. This study provides evidence of ongoing evolutionary change among C. jejuni isolates as they are cultured in different laboratories and highlights the need for careful consideration of genetic variation within laboratory reference strains. This article contains data hosted by Microreact.

Whole-genome comparative analysis of Campylobacter jejuni strains isolated from patients with diarrhea in northeastern Poland

BackgroundCampylobacter jejuni is the leading cause of bacterial gastroenteritis (campylobacteriosis) in humans worldwide, and the most frequent pathogen associated with Guillain-Barré syndrome (GBS) and Miller-Fisher syndrome (MFS). The study was designed in order to assess similarities between genomes of Campylobacter jejuni strains, isolated from children suffering from acute diarrhea in northeastern Poland, in comparison to C.jejuni genomes stored in public databases. The analysis involved phylogeny, resistome and virulome. In addition, the Campylobacter PubMLST database was used to estimate the prevalence of the analyzed C. jejuni sequence type (STs) in other countries.ResultsCampylobacter jejuni ST50, ST257 and ST51 represented 5.3%, 4.5% and 2.2% of the PubMLST records, respectively. Overall, strains representing the STs showed common resistance to tetracyclines (51.3%) and fluoroquinolones (31.8%), mediated through the tetO gene (98.2%) and point mutation (T86I) in the gyrA gene (100%). However, the latter was present in all our isolates. The major differences in virulence patterns concerned serotypes, lipooligosaccharide (LOS) classes and certain clinically relevant genes.ConclusionsCampylobacter jejuni ST50, ST51 and ST257 are among the top ten of STs isolated in Europe. WGS revealed diversity of serotypes and LOS classes in ST50 strains, that deserves further clinical and epidemiological investigations as it might be related to a risk of post-infectious neurological sequels such as Guillain-Barré syndrome. Additionally, the results implicate lower pathogenic potential and distinct transmission chains or reservoirs for C. jejuni ST51 isolates responsible for campylobacteriosis in northeastern Poland.

Growth in the presence of specific antibiotics induces biofilm formation by a Campylobacter jejuni strain sensitive to them but not in resistant strains.

Campylobacter jejuni (C. jejuni) are among the most frequently identified bacteria associated with human gastroenteritis worldwide. Exposure to antibiotics may induce or inhibit biofilm formation in some bacterial species. Little work has been reported on the influence of antibiotics on biofilm formation by C. jejuni. This study investigated the effect of six different classes of antibiotics with different modes of action (ampicillin, ciprofloxacin, erythromycin, nalidixic acid, rifampicin and tetracycline) on biofilm formation in vitro by seven C. jejuni from poultry with different antibiotic resistance profiles. The results indicated that in the presence of most of the tested antibiotics, biofilm formation by C. jejuni strains, which are resistant to them, was reduced but biofilm formation in sensitive strains was increased. The ability of certain antibiotics to induce biofilm formation by a tested C. jejuni strain is of concern, with respect to the effective control of disease caused by this pathogen; however, further work is required to confirm how widespread this feature is.

The risk of aerotolerant Campylobacter jejuni strains in poultry meat distribution and storage

Poultry meat is a major vector for Campylobacter jejuni foodborne illness. Since C. jejuni is microaerophillic, the cell counts gradually decreased during distribution and display under aerobic condition. However, if the pathogen can resist to aerobic condition, it may cause serious problem in food safety. This study determined the aerotolerance of C. jejuni isolated from poultry and the risk of the aerotolerant C. jejuni strains. Fourteen C. jejuni strains isolated from poultry were subjected to aerobic condition in a shaking incubator at 500 rpm and 37 °C. The cell counts of C. jejuni strains were enumerated on modified CCDA-Preston at 0, 24, 72 and 120 h, and the strains, having reduction less than 2 Log CFU/mL for 120 h were determined as aerotolerant C. jejuni strain. Non-aerotolerant and aerotolerant C. jejuni strains were then incubated at 4 °C under aerobic condition to compare the growth between aerotolerant and non-aerotolerant strains. In addition, transcriptomes for virulence and stress response genes (cadF, cdtB, ciaB, clpP and htrB) were compared between non-aerotolerant and aerotolerant C. jejuni strains. Among 14 C. jejuni strains, seven strains (50%) showed less than 2-Log CFU/mL reduction at 37 °C after 24 h, and five strains of them still showed less than 2-Log CFU/mL reduction after 48 h. Especially, C. jejuni SMFM2015-Du7 and C. jejuni SMFM2014-Du16 were still survived after 120 h under aerobic condition, which were then determined as aerotolerant C. jejuni. However, at 4 °C under aerobic condition, there were no significant differences in the reduction of C. jejuni cell counts and virulence gene expressions between non-aerotolerant (C. jejuni SMFM2014-Du8) and aerotolerant strains (C. jejuni SMFM2015-Du7 and C. jejuni SMFM2014-Du16) except for stress response gene (htrB). These results indicate that there are aerotolerant C. jejuni strains, but their risk is similar to non-aerotolerant C. jejuni strains at 4 °C under aerobic condition, which is distribution and storage condition for poultry meat. Therefore, additional food safety management for the aerotolerant C. jejuni is not necessary.

Quantitative microbiological slaughter process analysis in a large-scale Swiss poultry abattoir

We performed a quantitative microbiological slaughter process analysis in a large-scale Swiss poultry abattoir. At each of six selected process steps (after plucking, cloaca excision, evisceration, washing, water spray chiller and dry air chiller), 103 carcasses from 50 flocks were sampled and quantitatively tested for indicator bacteria (total viable counts, Escherichia coli/Enterobacteriaceae counts) as well as for Campylobacter spp. and extended spectrum betalactamase (ESBL)-producing Enterobacteriaceae. Samples consisted of a pooled back, breast and leg skin sample as well as swab samples from the thoracic and abdominal cavities. On skin samples, the presence of Escherichia coli and Enterobacteriaceae as indicators of fecal contamination increased between plucking and evisceration (on average by 1.2 log CFU/g), while washing after evisceration successfully decreased the microbial load (on average by 0.8 log CFU/g). Subsequent chilling slightly reduced microbial counts on the carcasses skin and markedly reduced the counts in the abdominal cavity. ESBL-producing Escherichia coli was present above the limit of detection (LOD) with a prevalence of 6.1 %, the majority of which belonged to phylogenetic group A. The blaCTX-M-1 gene was found in all ESBL-producing strains. The prevalence of Campylobacter above the LOD was 16.7 %, and none of the final, chilled carcasses had counts that exceeded 1000 CFU/g. Multilocus sequence typing of 120 Campylobacter jejuni strains yielded 15 different sequence types (ST) among which ST 21 was predominant with 31.7 % and four newly defined ST.

The effect of epinephrine and norepinephrine on the growth and pathogenicity of Campylobacter jejuni

Campylobacter spp. is a leading cause of foodborne illness globally. The pathogen colonises the gastrointestinal tract of the host, where small concentrations of neuroendocrine hormones are also secreted. Epinephrine and norepinephrine are neuroendocrine hormones involved in the stress response that have been shown to promote the expression of virulence factors in pathogens including E. coli, Salmonella spp., and Campylobacter spp. In our study Campylobacter jejuni strains from human infection and broiler farms that were supplemented with epinephrine and norepinephrine showed increased growth characterised by shorter lag phases and higher maximum OD595, and enhanced pathogenicity characterised by increased motility, attachment to and invasion of Caco-2 cells. The data obtained suggests that host stress may promote C. jejuni proliferation and pathogenicity.

Efficacy of pulsed electric fields and antimicrobial compounds used alone and in combination for the inactivation of Campylobacter jejuni in liquids and raw chicken

This work evaluated the bactericidal effects of a number of essential oils (EOs), organic acids and pulsed electric fields (PEF) against a range of Campylobacter jejuni strains. C. jejuni (1146DF) was found to be the most PEF resistant strain, and was chosen to evaluate the combination of PEF and oregano EO (the most effective compound). Simultaneous PEF/oregano treatments in liquid showed no significant increase in levels of inactivation when compared to reductions achieved for individual PEF treatments (p > 0.05). However, in a sequential combination approach, PEF treatment followed by re-suspension in oregano produced significant increases in inactivation levels at all field strengths tested (p < 0.05). ¼ MIC of oregano was determined as the minimum concentration required to obtain maximum microbial inactivation using sequential combinations. PEF was then applied to raw chicken using different field strengths 0.25–1 kV/cm, followed by re-suspension in ¼ MIC of oregano. Application of 1 kV/cm in chicken followed by resuspension achieved a reduction close to 1.5 Log10 CFU/g, and also showed synergistic behaviour. The results obtained in this work would open the possibility of using this combination for chicken decontamination, because the inactivation achieved was in the same range as those obtained using conventional thermal treatments.

Fate of Salmonella ssp., Listeria monocytogenes, and Campylobacter ssp., During Fermentation and Drying of Duck Salami

ObjectivesCreating artisanal, dry salami products is an increasing trend for charcuterie companies in the United States. These raw, ready-to-eat products are required by USDA-FSIS to have a scientifically valid HACCP system addressing relevant biological hazards. To our knowledge, no literature exists for the validation (at least a 5 Log10 reduction of pathogens per FSIS) of salami products containing duck. Therefore, an experiment was designed to validate the safety of duck salami. The objectives of this study were to validate the safety of fermented and dried duck salami and to investigate if a duck salami manufacturing processes could achieve a 5 LOG10 (CFU/g) reduction of Salmonella ssp., Listeria monocytogenes, and Campylobacter ssp.Materials and MethodsDuck trim and pork belly (70% duck trim, 30% pork belly) were placed in a mixed culture bath approximating three liters. The culture bath was made by growing individually and then combining three strains each of Salmonella spp. and Listeria monocytogenes, two strains of Campylobacter jejuni, and one strain of Campylobacter coli. After inoculation, meat was air dried (30 min @ 23°C), tumbled with one liter of 2.5% BeefxideÒantimicrobial treatment (lactic and citric acid and hydrogen peroxide), and placed in a walk-in cooler (2–4°C) overnight. After inoculation and antimicrobial treatment (∼24 h), the meat was ground (6mm grinding plate) and seasoned with salt (2.5%), cure (NaNO3 & NaNO2), spices, and starter culture. The ground duck-pork mixture was stuffed into 55mm collagen casings, fermented for 48 h (23°C, 95% rH), and dried (12°C, 75% rH) to ∼45% weight loss (approx. 5 wk). Salamis were then vacuum packaged and stored at 23°C (approx. 4 wk). Three independent replications were conducted, and pathogen concentrations, pH, and water activity (aw) were analyzed at Days 0, 1, 2, 3, 5, 10, and weekly until Day 66 during each replication. Critical parameters for production included a final pH less than 5.3 and final aw less than 0.90.ResultsA 5 LOG10(CFU/g) reduction was achieved for all three pathogens. Salmonella achieved a 5.47 LOG10(CFU/g) (p < 0.0001) reduction by Day 38, Listeria monocytogenes achieved a 5.20 LOG10(CFU/g) (p < 0.0001) reduction by Day 59, and Campylobacter achieved a 6.85 LOG10(CFU/g) (p < 0.0001) reduction by Day 45. Final reductions of 7.03 (p < 0.0001), 5.90 (p < 0.0001), and 7.19 (p < 0.0001) LOG10(CFU/g) were achieved for Salmonella spp., Listeria monocytogenes, and Campylobacter spp., respectively. During the entire fermentation and drying process, populations of each species never increased by more than 1 LOG10 (CFU/cm2). A final pH of 5.11 and a final aw of 0.81 were also achieved.ConclusionThe results of this study indicate that the parameters used to ferment and dry this product are able to achieve a 5 LOG10 (CFU/g) reduction of each pathogen to validate the safe production of duck salami.

Synthesis of the Campylobacter jejuni 81-176 Strain Capsular Polysaccharide Repeating Unit Reveals the Absolute Configuration of its O-Methyl Phosphoramidate Motif.

The O-methyl phosphoramidate (MeOPN) motif is a non-stoichiometric modification of capsular polysaccharides (CPS) in ≈70 % of all Campylobacter jejuni strains. Infections by C. jejuni lead to food-borne illnesses and the CPS they produce are key virulence factors. The MeOPN phosphorus atom in these CPS is stereogenic and is found as a single stereoisomer. However, to date, the absolute stereochemistry at this atom has been undefined. We report the synthesis of the three repeating units found in C. jejuni 81-176 CPS; one of these possesses a MeOPN group. In the course of these studies we established that the stereochemistry of the phosphorus atom in this MeOPN group is R. These studies represent the first unequivocal proof of stereochemistry of this group in any C. jejuni CPS. The compounds produced are anticipated to be useful tools in investigations targeting the function and biosynthesis of this structurally-interesting modification, which so far has only been identified in campylobacter.

Synthesis of the Campylobacter jejuni 81‐176 Strain Capsular Polysaccharide Repeating Unit Reveals the Absolute Configuration of its O‐Methyl Phosphoramidate Motif

AbstractThe O‐methyl phosphoramidate (MeOPN) motif is a non‐stoichiometric modification of capsular polysaccharides (CPS) in ≈70 % of all Campylobacter jejuni strains. Infections by C. jejuni lead to food‐borne illnesses and the CPS they produce are key virulence factors. The MeOPN phosphorus atom in these CPS is stereogenic and is found as a single stereoisomer. However, to date, the absolute stereochemistry at this atom has been undefined. We report the synthesis of the three repeating units found in C. jejuni 81‐176 CPS; one of these possesses a MeOPN group. In the course of these studies we established that the stereochemistry of the phosphorus atom in this MeOPN group is R. These studies represent the first unequivocal proof of stereochemistry of this group in any C. jejuni CPS. The compounds produced are anticipated to be useful tools in investigations targeting the function and biosynthesis of this structurally‐interesting modification, which so far has only been identified in campylobacter.