Influence of modified atmosphere and vacuum packaging with and without nanosilver-coated films on different quality parameters of pork.

Pork is often marketed in packages with high oxygen atmosphere (MAP) or vacuum to improve shelf life and appearance. As silver ions have antibacterial effects, food contact films coated with silver might improve the shelf life of meat. In the present study, pork was wrapped in commercially available films, coated with nanosilver particles, and stored in the two packaging variants MAP and vacuum for 12 days. During storage, samples were analyzed on days 1 (before packaging), 4, 8 and 12 for microbiological contamination, meat quality (e.g., pH, color), and for the percentages of the myoglobin (Mb) redox forms. In addition, the effects of the film were examined after inoculation of the meat with high quantities of methicillin-resistant Staphylococcus aureus (MRSA) cells before vacuum storage for 8 days. MAP storage resulted in higher lightness (L*) values, lower liquid loss and higher Mb oxidation compared to vacuum. Microbiological spoilage was partly affected by the packaging variants with reducing effects of the MAP. The nanosilver-coating only affects the Mb redox form percentages of the pork cutlets and on day 4 the L* values, whereas microbiological parameters were not influenced. As the nanosilver coating had no influence on the total viable bacteria counts as well as Pseudomonas spp., Enterobacteriaceae and MRSA counts, an advantage of the nanosilver coating on the shelf life could be excluded.

Effects of parsley extract powder as an alternative for the direct addition of sodium nitrite in the production of mortadella-type sausages - Impact on microbiological, physicochemical and sensory aspects.

Increasing concern about chemical additives in processed meat has led to an increased market of uncured and alternatively cured meat products. However, the use of vegetable extracts or the exclusion of curing salt may increase the risk of greater bacterial growth and alteration of several physicochemical parameters. Therefore, in this study mortadella-type sausages, manufactured with 1.07 (V3), 2.14 (V4) and 4.29 (V5) g parsley extract powder/kg sausage meat were produced. These sausage variants were compared to an uncured (V2) and a traditionally nitrite-cured control (V1). A significantly lower Listeria monocytogenes growth was observed for V5 compared to all other variants during the storage time of 28days (P<0.05). Compared to V1, V5 presented a residual nitrite content reduced by 40% and similar a* values until day 21. Concerning texture parameters, L* and aw values, no differences between the variants were detected. Sensory analysis showed that overall acceptance of V4 and V5 was comparable with V1.

Lauric acid as feed additive - An approach to reducing Campylobacter spp. in broiler meat.

The increasing prevalence of Campylobacter spp. within broiler populations is a major problem for food safety and consumer protection worldwide. In vitro studies could already demonstrate that Campylobacter spp. are susceptible to lauric acid. The purpose of this study was to examine in vivo the influence of lauric acid as a feed additive on slaughter parameters, muscle fatty acid profile, meat quality traits and the reduction of Campylobacter coli in inoculated meat of Ross 308 (R308) and Hubbard JA 757 (HJA) broilers in three independent trials (n = 3). Although slaughter parameters did not show any significant differences, the fatty acid profile of both breeds revealed significantly higher lauric acid concentrations (P < 0.0001) in the Musculus pectoralis superficialis of treated broilers. Comparing both tested breeds, R308 test broilers had significantly higher lauric acid concentrations than HJA test broilers (P < 0.0001), indicating a higher conversion rate in those animals. The meat quality traits showed no differences in the R308 breed (P > 0.05), but HJA test broilers had higher values for drip loss, electrical conductivity, CIE color values L* and b*, and lower pH values. The inoculation trials of R308 showed that initial bacterial loads of 5.9 log10 cfu/g were reduced during six days of storage (4°C) to approximately 4.3 log10 cfu/g in the control groups compared to 3.5 log10 cfu/g in the treatment groups (P = 0.0295), which could be due to antimicrobial effects of lauric acid within the muscle. This study therefore suggests that lauric acid as a feed additive has the potential to improve food safety by reducing the numbers of Campylobacter coli in broiler meat. However, this effect seems to be dependent on the breed determining the feed intake capacity, the fat deposition and therefore the ability to incorporate lauric acid in the muscle.

Comparative analysis of the susceptibility to biocides and heavy metals of extended-spectrum ß-lactamase-producing Escherichia coli isolates of human and avian origin, Germany.

A total of 174 extended-spectrum ß-lactamase (ESBL)-producing Escherichia coli isolates collected from humans (n=140) and healthy broiler chickens (n = 34) was included in the study. The MIC values of alkyl diaminoethyl glycin hydrochloride, benzethonium chloride, benzalkonium chloride, chlorhexidine, acriflavine, copper sulfate, silver nitrate and zinc chloride were determined by the broth microdilution method. Significant differences in MIC distributions were found between human and avian isolates and between CTX-M-, SHV- and TEM-type ESBL E. coli for chlorhexidine, silver nitrate, zinc chloride and copper sulfate by statistical analysis. Isolates with reduced susceptibility were investigated for the presence and localization of tolerance-mediating genes by PCR analysis and Southern blotting. The genes emrE, mdfA, sugE(c), cueO, copA, zntA and zitB were commonly present in isolates with elevated MICs, while the genes qacE∆1, qacF, qacH, sugE(p), cusC and pcoA, were less prevalent. In several isolates, a plasmid localization of the genes qacE∆1, qacF, qacH and sugE(p) on large plasmids >20 kb was detected.

Pedobacter lusitanus sp. nov., isolated from sludge of a deactivated uranium mine.

Strain NL19T is a Gram-stain-negative, aerobic bacterium that was isolated from sludge of a deactivated uranium mine in Portugal. 16S rRNA gene sequence analysis revealed that strain NL19T is a member of the genus Pedobacter and closely related to the strains Pedobacter himalayensis MTCC 6384T, Pedobacter cryoconitis DSM 14825T, Pedobacter westerhofensis DSM 19036T and Pedobacterhartonius DSM 19033T. It had a DNA G+C content of 40.8 mol%, which agreed with the genus description. The main fatty acids included C16 : 1ω7c, C14 : 1ω5c, C4 : 0, iso-C17 : 0, iso-C17 : 0 3-OH, C16 : 0, anteiso-C15 : 0 and iso-C15 : 0 3-OH. The main lipids present were phospholipids (60 %) and sphingolipids (35 %). The most abundant phospholipids included phosphatidylethanolamine, phosphatidylinositol and phosphatidylcholine. Menaquinone-7 (MK-7) was the only isoprenoid quinone detected. DNA-DNA hybridization similarities between strain NL19T and Pedobacter himalayensis MTCC 6384T, Pedobacter cryoconitis DSM 14825T, Pedobacter westerhofensis DSM 19036T and Pedobacter hartonius DSM 19033T were 15.3 , 16.2 , 11.5 and 16.0 %, respectively. Strain NL19T can also be distinguished from these four species based on gyrB and intergenic transcribed spacers (ITS) sequences and by some phenotypic traits such as NaCl tolerance, pH, growth temperature and carbon source utilization. Strain NL19Trepresents a novel species of the genus Pedobacter, for which the name Pedobacter lusitanus sp. nov. is proposed. The type strain is NL19T (=LMG 29220T=CECT 9028T). An amended description of Pedobacter himalayensis is also included.

Diversity of Clostridium perfringens toxin-genotypes from dairy farms.

BACKGROUND: Clostridium (C.) perfringens is the causative agent of several diseases in animals and humans, including histotoxic and enteric infections. To gain more insight into the occurrence of its different toxin-genotypes in dairy herds, including those toxin genes previously associated with diseases in cattle or humans, 662 isolates cultivated from feces, rumen content and feed collected from 139 dairy farms were characterized by PCR (detecting cpa, cpb, iap, etx, cpe, and both allelic variants of cpb2). RESULTS: Isolates from feces were assigned to type A (cpa positive, n = 442) and D (cpa and etx positive, n = 2). Those from rumen content (n = 207) and feed (n = 13) were all assigned to type A. The consensus and atypical variants of the cpb2 gene were detected in 64 (14.5 %) and 138 (31.22 %) of all isolates from feces, and 30 (14.5 %) and 54 (26.1 %) of all isolates from rumen content, respectively. CONCLUSION: Both allelic variants of cpb2 occurred frequently in animals without signs of acute enteric disease, whereby the atypical variant dominated. Five (0.8 %) of all type A isolates were positive for the cpe gene. Therefore, the present study indicates that dairy cows are no primary source for potentially human pathogenic enterotoxin gene positive strains.

Detection of Clostridium botulinum neurotoxin genes (A-F) in dairy farms from Northern Germany using PCR: A case-control study.

Classical botulism in cattle mainly occurs after ingestion of feed contaminated with preformed toxin. In 2001 a form of botulism ("visceral botulism") was postulated to occur after ingestion of Clostridium (C.) botulinum cells or spores, followed by colonization of the intestine, and local production of botulinum neurotoxin (BoNT) causing chronic generalized disease. To verify the potential role of C. botulinum in the described syndrome, a case-control study was conducted, including 139 farms. Fecal samples, rumen content, water and silage samples were collected on each farm. Real time BoNT gene PCR assays were conducted after enrichment in RCM (Reinforced Clostridial Medium) at 37 °C and conventional PCRs after enrichment in MCM (Modified Cooked Meat Medium) at 30 °C. Furthermore, a direct detection of BoNT genes without prior enrichment was attempted. BoNT A, B, C, D, E and F genes were detected in animal samples from 25 (17.99%), 3 (2.16%), 0 (0.0%), 2 (1.44%), 1 (0.72%), and 3 (2.16%) farms, respectively. Eleven feed samples were positive for BoNT A gene. By enrichment a significant increase in sensitivity was achieved. Therefore, this should be an essential part of any protocol. No significant differences regarding BoNT gene occurrence could be observed between Case and Control farms or chronically diseased and clinically healthy animals within the particular category. Thus, the postulated form of chronic botulism in cows could not be confirmed. This study supports the general opinion that C. botulinum can occasionally be found in the rumen and intestine of cows without causing disease.

Identification of Trueperella pyogenes isolated from bovine mastitis by Fourier transform infrared spectroscopy.

The present study was designed to investigate the potential of Fourier transform infrared (FT-IR) spectroscopy to identify Trueperella (T.) pyogenes isolated from bovine clinical mastitis. FT-IR spectroscopy was applied to 57 isolates obtained from 55 cows in a period from 2009 to 2012. Prior to FT-IR spectroscopy these isolates were identified by phenotypic and genotypic properties, also including the determination of seven potential virulence factor encoding genes. The FT-IR analysis revealed a reliable identification of all 57 isolates as T. pyogenes and a clear separation of this species from the other species of genus Trueperella and from species of genus Arcanobacterium and Actinomyces. The results showed that all 57 isolates were assigned to the correct species indicating that FT-IR spectroscopy could also be efficiently used for identification of this bacterial pathogen.

Development of loop-mediated isothermal amplification (LAMP) assay for rapid and sensitive identification of ostrich meat.

Animal species identification is one of the primary duties of official food control. Since ostrich meat is difficult to be differentiated macroscopically from beef, therefore new analytical methods are needed. To enforce labeling regulations for the authentication of ostrich meat, it might be of importance to develop and evaluate a rapid and reliable assay. In the present study, a loop-mediated isothermal amplification (LAMP) assay based on the cytochrome b gene of the mitochondrial DNA of the species Struthio camelus was developed. The LAMP assay was used in combination with a real-time fluorometer. The developed system allowed the detection of 0.01% ostrich meat products. In parallel, a direct swab method without nucleic acid extraction using the HYPLEX LPTV buffer was also evaluated. This rapid processing method allowed detection of ostrich meat without major incubation steps. In summary, the LAMP assay had excellent sensitivity and specificity for detecting ostrich meat and could provide a sampling-to-result identification-time of 15 to 20 minutes.

Establishment of serological herd profiles for zoonoses and production diseases in pigs by "meat juice multi-serology".

The most important pork-borne zoonotic diseases in humans such as Salmonelloses and Yersinioses cause only latent infections in pigs. Thus, the infection of pigs does not result in apparent or palpable alterations in the pig carcasses. This is the major reason, why the traditional meat inspection with adspection, palpation and incision is not able to control the food safety risks of today. The objective of this paper is to evaluate a set of serological tests, which provides a classification of pig herds into "zoonoses risk categories" as demanded by EU law and into "herd health risk categories" by using meat juice as diagnostic specimen for ELISA tests. Serological data that were obtained by testing meat juice samples from various pig herds were analyzed as proof of the "meat juice multi-serology" concept. For that, at least 60 meat juice samples from 49 pig herds each were taken between September 2010 and March 2011 and tested for antibodies against zoonotic pathogens (Salmonella spp., Trichinella spp., Yersinia enterocolitica and Toxoplasma gondii) and against pathogens causing production diseases (Mycoplasma hyopneumoniae, influenza A virus subtype H1N1, influenza A virus subtype H3N2 and PRRSV). Apparent and true animal prevalence, herd prevalence values and intra-herd seroprevalence values as well as the predictive values for the herd and the animal prevalence values were calculated for each pathogen and each of the 49 randomly selected herds. The herd seroprevalence values (one seropositive sample per herd determined a "positive herd") for Y. enterocolitica, Salmonella spp., T. gondii, M. hyopneumoniae and PRRSV were higher than 80%, respectively, for the influenza A viruses between 60% and 14% and for Trichinella spp. 0%. Although all herds were located in the same area in the Northwest of Germany within a radius of 250 km, the intra-herd seroprevalence values for all tested pathogens, except for Trichinella spp., varied remarkably from herd to herd. In the case of Y. enterocolitica and T. gondii the intra-herd seroprevalence values varied even from zero to 100%. This shows that a serological risk categorization of pig herds regarding zoonoses and production diseases is meaningful if used for risk-based decisions in the framework of the new meat inspection concept and as part of the herd health management system. Thus, the development of a cost-efficient, time- and labour-saving test system for simultaneously detecting various antibodies should be the next step for an extensive implementation of the meat juice multi-serology concept.

Analysis of triclosan-selected Salmonella enterica mutants of eight serovars revealed increased aminoglycoside susceptibility and reduced growth rates.

The biocide triclosan (TRC) is used in a wide range of household, personal care, veterinary, industrial and medical products to control microbial growth. This extended use raises concerns about a possible association between the application of triclosan and the development of antibiotic resistance. In the present study we determined triclosan mutant prevention concentrations (MPC) for Salmonella enterica isolates of eight serovars and investigated selected mutants for their mechanisms mediating decreased susceptibility to triclosan. MPCTRC values were 8-64-fold higher than MIC values and ranged between 1-16 µg/ml. The frequencies at which mutants were selected varied between 1.3 x 10(-10)-9.9 x 10(-11). Even if MIC values of mutants decreased by 3-7 dilution steps in the presence of the efflux pump inhibitor Phe-Arg-ß-naphtylamide, only minor changes were observed in the expression of genes encoding efflux components or regulators, indicating that neither the major multidrug efflux pump AcrAB-TolC nor AcrEF are up-regulated in triclosan-selected mutants. Nucleotide sequence comparisons confirmed the absence of alterations in the regulatory regions acrRA, soxRS, marORAB, acrSE and ramRA of selected mutants. Single bp and deduced Gly93→Val amino acid exchanges were present in fabI, the target gene of triclosan, starting from a concentration of 1 µg/ml TRC used for MPC determinations. The fabI genes were up to 12.4-fold up-regulated. Complementation experiments confirmed the contribution of Gly93→Val exchanges and fabI overexpression to decreased triclosan susceptibility. MIC values of mutants compared to parent strains were even equal or resulted in a more susceptible phenotype (1-2 dilution steps) for the aminoglycoside antibiotics kanamycin and gentamicin as well as for the biocide chlorhexidine. Growth rates of selected mutants were significantly lower and hence, might partly explain the rare occurrence of Salmonella field isolates exhibiting decreased susceptibility to triclosan.

Biodiversity of Enterococcus faecalis based on genomic typing.

Enterococcus faecalis is a common inhabitant of the gastrointestinal tracts of different animals and is also found in other environments, such as plants, soil, food and water. The diverse nature of E. faecalis, which includes pathogenic, commensal and probiotic strains, calls for the development of tools for accurate discrimination and characterization at the strain level. Here we studied the genetic relationships among 106 E. faecalis strains isolated from diverse origins and possessing different degrees of virulence. Strain typing was conducted using a set of selected simple-sequence repeat (SSR) loci combined with multilocus sequence typing (MLST) analysis, which discriminated among the strains and separated them into three main clusters. While pathogenic and commensal isolates were dispersed along the dendrogram, probiotic and cheese-originated strains were highly associated with one specific cluster (cluster 1). The strain panel was further characterized by testing the occurrence of two virulence determinants (esp gene and ß-hemolysis). The two determinants showed low abundance among probiotic and cheese-originated strains within cluster 1 when compared to non-cluster 1 cheese-originated strains, indicating a possible association of cluster 1 with non-virulent strains. Our results further emphasize the importance and challenge of precise characterization of E. faecalis strains from various sources.

Genotypic and phenotypic characterization of Staphylococcus aureus isolates from wild boars.

Eight Staphylococcus aureus isolates collected from 117 wild boars were characterized and compared to livestock isolates. They belonged to sequence types ST133, ST425, and the new type ST1643. The spa types were t1181, t6782, and the new types t6384, t6385, and t6386. Antimicrobial susceptibility testing and microarray-based genotyping confirmed the absence of important virulence/resistance genes.

A comparison of the carcase characteristics of pigs immunized with a 'gonadotrophin-releasing factor (GnRF)' vaccine against boar taint with physically castrated pigs.

Evaluating the effect of using a GnRF vaccine against boar taint on the carcase characteristics of boars, vaccinated pigs were compared with physically castrated. In total, 554 male pigs were randomly assigned to treatment groups. T01 comprised physically castrated pigs in the first week of life, T02 comprised pigs vaccinated twice before slaughtering. There was neither significant difference between the groups in terms of average liveweight nor in the hot carcase weight. The mean dressing percentage was 1.5% higher for T01 than for T02 (P<0.0001). The lean meat percentage was significantly higher in T02 (P<0.0001). Backfat and backmuscle thickness were significantly higher in T01 (P<0.0001 and P=0.0099, respectively). Within the EUROP grading vaccinated pigs were in favour (P=0.0034). There were no significant differences using the AutoFOM system: weights of the boned ham, boned shoulder and loin (P=0.5102, P=0.8881 and P=0.1919, respectively). The weight of the belly was significantly higher (P=0.0042) in T01 while the lean meat percentage of belly was significantly higher (P<0.0001) in T02.