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PubMed2001

Comparison of TaqMan Salmonella amplification/detection kit with standard culture procedure for detection of Salmonella in meat samples.

We evaluated the TaqMan PCR Salmonella amplification/detection kit (PE Applied Biosystems) for rapid detection of Salmonella from a variety of meat samples. This system uses the 5' nuclease activity of Taq DNA polymerase, which digests an internal fluorogenic probe to monitor the amplification of the target gene. The detection sensitivity of the kit, using 2 kinds of DNA extraction protocols, was compared with that obtained with 4 protocols of official culture methods. A total of 98 meat samples (16 raw beef, 31 pork and 51 chicken) were tested. The results of the TaqMan PCR method and the combined results of the 4 cultural protocols showed excellent agreement. However, no single culture protocol showed optimal recovery of Salmonella comparable to the PCR method. These results suggest that the TaqMan PCR method is a reliable and rapid method useful for detecting Salmonella in meat products.

Food Microbiology↗
PubMed1999

Evaluation of a polymerase chain reaction-based test for detecting Salmonella spp. in food samples: Probelia Salmonella spp.

A commercially available polymerase chain reaction (PCR) kit was evaluated for the detection of Salmonella spp. in food samples. The test combines PCR amplification and sandwich hybridization of the amplified DNA in microtiter plates. The sensitivity and specificity was evaluated with 52 Salmonella strains and 51 non-Salmonella strains and showed that the test was entirely reliable. The threshold sensitivity was 10(2) CFU/ml. The limit of detection of dead cells that determines the minimum detection level of dead cells in food samples was superior to 10(6) CFU/25 g, a level rarely achieved in naturally contaminated samples. After an 18-h pre-enrichment step, the test could detect viable Salmonella in artificially contaminated food samples, even for the lower contamination level (3 CFU/25 g). There was complete agreement between the PCR test and the ISO 6579 bacteriological reference method with artificially contaminated samples. Regarding the accuracy of the results obtained from 253 naturally or noncontaminated foods and from 32 artificially contaminated foods, the agreement percentage was 99.6%. The fidelity of the technique was evaluated in a collaborative study with eight European laboratories and showed a correlation of 98.4%.

Colony Count, Microbial↗
PubMedDate not supplied

Detection of Salmonella in fresh cheese, poultry products, and dried egg products by the ISO 6579 Salmonella culture procedure and the AOAC official method: collaborative study.

Three food types were analyzed for the presence of Salmonella by the AOAC culture method and by the International Organization for Standardization (ISO 6579:2002) culture method. Paired test portions of each food type were simultaneously analyzed by both methods. A total of 21 laboratories representing federal government agencies and private industry, in the United States and Europe, participated in this interlaboratory study. Foods were artificially contaminated with Salmonella and competing microflora if naturally contaminated sources were not available. No statistical differences (p < 0.05) were observed between the AOAC and ISO culture methods for fresh cheese and dried egg products. A statistically significant difference was observed for one of the 2 lots of poultry from the first trial. The poultry meat used in this run was radiation sterilized, artificially contaminated with Salmonella and competitive flora, and then lyophilized. A second trial was conducted with 2 separate lots of raw ground chicken that were naturally contaminated. The results from the second trial showed no statistical difference between the 2 culture methods. A third trial involving 4 laboratories was conducted on 2 separate lots of naturally contaminated raw poultry. Again, no statistically significant differences occurred. It is recommended that ISO 6579:2002 culture method for Salmonella be adopted Official First Action for the analysis of fresh cheese, fresh chilled and frozen poultry, and dried egg products.

Cheese↗
PubMedDate not supplied

Evaluation of VIDAS Salmonella (SLM) immunoassay method with Rappaport-Vassiliadis (RV) medium for detection of Salmonella in foods: collaborative study.

A collaborative study was conducted to compare the VIDAS Salmonella (SLM) with Rappaport-Vassiliadis (RV) method for detection of Salmonella in foods to the current standard method presented in the U.S. Food and Drug Administration's Bacteriological Analytical Manual (BAM) and the culture method presented in AOAC's Official Methods of Analysis. The VIDAS SLM with RV method uses tetrathionate broth in combination with RV medium in place of selenite cystine broth for selective enrichment, thereby eliminating the hazardous waste issue for laboratories. Twenty five laboratories participated in the evaluation, each testing one or more of 8 test products: nonfat dry milk, dried egg, soy flour, lactic casein, milk chocolate, raw ground pork, raw ground turkey, and raw peeled shrimp. Results of the study showed no significant differences in the numbers of confirmed positive samples with the VIDAS SLM with RV procedure and the BAM/AOAC culture procedure. The VIDAS SLM with RV method was effective for rapid detection of Salmonella in foods. It is recommended that AOAC INTERNATIONAL modify the VIDAS Salmonella SLM procedure to include the RV method.

Animals↗
PubMed2005

[Role of Salmonella and Yersinia in the pathogenesis of spondyloarthropathies and rheumatoid arthritis. II. Antibodies to Salmonella and Yersinia in sera and synovial fluids].

IgA, IgG and IgM antibodies against Yersinia Yop proteins, Yersinia LPS and Salmonella LPS from different serogroups were determined by enzyme-linked immunosorbent assay (ELISA) in a 885 serum samples and 92 synovial fluids. The control group consisted of 200 healthy blood donors. Compared with control subjects, patients with arthritis showed significantly increased titres of antibodies against Yersinia Yop, Yersinia LPS and Salmonella LPS appropriately in 21.7%, 44.0% and 56.0% serum samples. The prevalence of positive antibody levels was highest in Yersinia serogroup O3 and Salmonella serogroup B and D antibodies. The IgA titres were found to be much higher in adults than in children and youngsters but IgM titres consequently decreased with age. Investigation of synovial fluids obtained from patients with arthritis showed that Yersinia and Salmonella antibodies in synovial fluid mirror those in serum by concentration, by specificity and by distribution in classes.

Antibodies, Bacterial↗
PubMedDate not supplied

A Salmonella-specific DNA probe and its use in southern hybridization for differentiation of Salmonella enteritidis.

Chromosomal DNA from phage type 13a and Phage type 8 of Salmonella enteritidis (SE) was cloned in Escherichia coli using the plasmid pUC8. A 2.1-kilobase-pair (kbp) DNA fragment specific for Salmonella spp. was identified by colony, dot, and Southern hybridization analyses. When labeled and used as a probe (C7), this recombinant clone hybridized with the DNA of 18 Salmonella species but did not hybridize with the DNA of seven other enteric and non-enteric bacterial species. In Southern blot hybridization, this probe hybridized specifically to a 6.0 kbp BglI-digested DNA fragment of 17 SE isolates from human as well as avian sources, thus differentiating this fragment from DNA of 17 other Salmonella species. The C7 probe also hybridized to a 5-kbp fragment of one SE DNA derived from human and two SE DNA from poultry sources. This may indicate variation among SE isolates.

Blotting, Southern↗
PubMed1993

The influence of culture conditions on the susceptibility of Salmonella typhimurium in the Salmonella mutagenicity test.

To determine the variability of tester strain susceptibility in the Salmonella mutagenicity assay and to optimize the culturing procedure we examined the influences of the overnight culture period (12-16 h), the use of an additional short-term culturing procedure (1-4 h) and the Salmonella density (cfu/plate) on the rate of revertants per plate. As tester strains we used Salmonella typhimurium TA97, TA98, TA100 and TA102. As shown previously for other microbial genotoxicity short-term tests (i.e. with Escherichia coli PQ37), we observed the highest susceptibility of the Salmonella strains, i.e. the highest amounts of revertants per plate, when using a 12 h overnight culture followed by a 2 h short-term culturing procedure. We calibrated the bacterial count to 100 x 10(6) cfu per assay by photometric measurement (600 nm). Initially, we used 0-1 nmole 2,4,7-trinitro-9-fluorenone with S. typhimurium TA97, 0-15 nmole daunomycin with strain TA98, 0-25 nmole sodium azide with strain TA100 and 0-15 nmole methylmethanesulfonate with strain TA102 as reference compounds in the standard plate incorporation test. Subsequently, to evaluate the results of the culturing procedure variations we examined 22 well-known mutagenic and direct-acting (-S9-mix) compounds out of different chemical classes using both the standard and a modified culturing procedure. The comparison of these results showed a 64% (for 4-nitroquinoline-N-oxide) to 421% (for sodium azide) increased amount of revertants for the modified test protocol.

Colony Count, Microbial↗
PubMed1999

Prophylactic administration of immune lymphokine derived from T cells of Salmonella enteritidis-immune pigs. Protection against Salmonella choleraesuis organ invasion and cecal colonization in weaned pigs.

Experiments involving 132 weaned piglets were conducted to evaluate the efficacy of a Salmonella enteritidis-immune lymphokine (PILK) derived from the T cells of Salmonella enteritidis (SE)-immunized pigs to protect weaned piglets from Salmonella choleraesuis (SC) infection. Fourteen-to-seventeen day-old piglets were weaned and randomly placed into 1 of 5 groups: (1) noninfected controls, (2) PILK 3X noninfected, (3) SC infected controls, (4) PILK 1X SC infected, and (5) PILK 3X SC infected. PILK was given orally either one time (PILK 1X) or three times (PILK 3X) over 14 days. One hour after the first PILK administration on day 0, piglets were orally challenged with 10(7) cfu of SC. Weights were recorded on day 0, day 7, and day 14. On day 14, pigs in groups 3, 4, and 5 were sacrificed and organs and lymph tissue were cultured for the presence of SC. Three replicates of this experiment were pooled and anlayzed. A significant reduction in the number of pigs positive for SC in the liver, lung, and spleen was found in group 5 (PILK 3X) when compared to group 3 (inf. cont. p < 0.001[). The number of SC positive cecal contents was dramatically reduced in group 5 group when compared to group 3, with the PILK 3X group showing 13% positive pigs versus 55.2% in the infected controls (p < 0.05). Weight gain over the 14 day study in the infected PILK 3X group (group 5) was found to be comparable to the gain observed in the group 1 (noninfected controls). The pigs receiving PILK 3X (group 2) with no SC challenge gained significantly more weight than all other groups, including the noninfected controls (group 1 p < 0.05[). The results of these experiments indicate that PILK protects against SC infection in weaned pigs while enhancing performance in the presence of an SC infection.

Animals↗
PubMed1989

Bacteriophage P22 as a vehicle for transducing cosmid gene banks between smooth strains of Salmonella typhimurium: use in identifying a role for aroD in attenuating virulent Salmonella strains.

A cosmid gene bank of the virulent Salmonella typhimurium C5 was constructed in Escherichia coli K12. The bank was repackaged into bacteriophage heads and transduced into the semi-rough S. typhimurium strain AS68 which expresses the LamB lambda receptor protein. Approximately 6000 ampicillin-resistant transductants were pooled and used as host for the propagation of bacteriophage P22. The P22 lysate was able to transduce cosmid recombinants to smooth strains of S. typhimurium and individual transductants were selected which complemented various S. typhimurium auxotrophic mutations. A stable mutation was introduced into the aroD gene of S. typhimurium C5. The resulting aroD- mutant, named CU038, was highly attenuated compared with the wild-type parent strain and BALB/c mice immunised orally with CU038 were well protected against challenge with the virulent C5 parental strain. Using the cosmid bank repackaged into bacteriophage P22 heads it was possible to isolate cosmid recombinants that could complement the aroD mutation of CU038 either by in vitro selection using minimal medium or in vivo selection for restoration of virulence in BALB/c mice. Repackaged P22 cosmid banks could provide a simple system for selecting in vivo for Salmonella virulence determinants. A Salmonella typhi strain harbouring mutations in aroA and aroD was constructed for potential use as a live oral typhoid vaccine in humans.

Animals↗
PubMed1994

Salmonella typhimurium and Salmonella enteritidis: changing epidemiology from 1973 until 1992.

A retrospective analysis, covering a period of 20 years, of 2049 primo-isolates of Salmonella typhimurium and 343 primo-isolates of Salmonella enteritidis was performed at our laboratory. In 1991, S. enteritidis (43.8%) outnumbered S. typhimurium (32.1%) as the most frequently isolated Salmonella. The age group distribution of S. enteritidis yielded peaks in the under-five and above-60 year age groups, whereas S. typhimurium only peaked in the under-five age group. S. enteritidis appeared to be twice as invasive as S. typhimurium. Both serotypes were more invasive in middle and older age groups than in under-fives.

Adolescent↗
PubMed2006

Antibiotic resistance, integrons and Salmonella genomic island 1 among non-typhoidal Salmonella serovars in The Netherlands.

The objective of this study was to investigate the antimicrobial resistance patterns, integron characteristics and gene cassettes as well as the presence of Salmonella genomic island 1 (SGI1) in non-typhoidal Salmonella (NTS) isolates from human and animal origin. Epidemiologically unrelated Dutch NTS strains (n=237) originating from food-producing animals and human cases of salmonellosis were tested for their susceptibility to 15 antimicrobial agents. Resistance to 14 of these antimicrobials, including the third-generation cephalosporins, was detected. Resistance to sulphonamides, ampicillin, tetracycline, streptomycin, trimethoprim and nalidixic acid was common (>/=10% of the strains were resistant). Resistance against three or more antimicrobials was observed in 57 isolates. The same 237 strains were studied for the prevalence of class 1 integrons, their gene cassettes and the presence of SGI1. Thirty-six isolates (15.2%) carried class 1 integrons. These integrons had ten distinct profiles based on the size of the integron and restriction fragment length polymorphism analysis. Integrons were detected for the first time in serovars Indiana and Senftenberg. Multidrug resistance was strongly associated with the presence of class 1 integrons in which the aadA2, aadA1, bla(PSE-1), dfrA1, dfrA5, dfrA14 or sat genes were present, as determined by nucleotide sequence determination. The presence of gene cassettes or combinations of gene cassettes not previously found in integrons in Salmonella was observed. SGI1 or its variants (SGI-B, -C and -F) were present in 16 isolates belonging to either serovar Typhimurium, Derby or Albany. Regardless of whether the isolate was of human or animal origin, the same resistance phenotype, integron profile and SGI1 structure could be observed.

Animals↗
PubMed2004

Salmonella enteritidis clearance and immune responses in chickens following Salmonella vaccination and challenge.

Our previous work showed that the cell-mediated immunity (CMI) was enhanced by live Salmonella vaccine (LV). The objective of this study was to evaluate the impact of live and killed Salmonella vaccines on Salmonella enteritidis (SE) clearance and to determine if the clearance was mediated by cell-mediated and/or humoral immunity. Chickens were first immunized at 2 weeks of age followed by a booster dose at 4 weeks, challenged with live SE 2 weeks later (6-week-old) and tested for CMI, antibody response and SE clearance 1-week post SE-challenge (7-week-old). Spleen cell proliferation induced by SE-flagella and Concanavalin A (Con A) were significantly higher and SE shedding was significantly lower in the LV group. The splenic CD3 population was significantly lower and B cells were higher in the control group compared to all the SE-challenged groups (with and without vaccination). Serum antibody to SE-flagella and envelope were significantly higher in the KV group compared to all the other groups. These results suggest that LV protects against SE infection, probably by enhancing the CMI.

Animals↗
PubMed1977

Survival of Salmonella eastbourne and Salmonella typhimurium in milk chocolate prepared with artificially contaminated milk powder.

Milk chocolate mass containing salmonellas was prepared by mixing artificially contaminated milk powder with the other ingredients at a temperature of about 40 degrees C. From this mass bars were made. Two series were prepared, with S. eastbourne and S. typhimurium respectively. The number of surviving salmonellas was counted after various periods of storage, up to 19 months. S. eastbourne was reduced in numbers during 19 months from an initial count of ca. 3 x 10(4) to ca. 3 x 10(2) per 100 g of chocolate. S. typhimurium died off more rapidly, and was not detectable in about 55 g after 15 months, in spite of an initial count of ca. 10(5) per 100 g.In these experiments the salmonellas in the milk powder had had to survive the spraying procedure and the adverse conditions in the dried powder. This may be the reason why S. eastbourne showed a distinctly better survival on storage than the same serotype showed in previous experiments in which the organism was added as a broth culture to the chocolate mix. With S. typhimurium, however, such a difference was hardly detectable.Possible explanations of these results are discussed.

Animals↗
PubMed1981

Seagulls (Larus spp.) as vectors of salmonellae: an investigation into the range of serotypes and numbers of salmonellae in gull faeces.

Of 1241 samples of seagulls faeces examined, 12.9% were found to contain salmonellae. The number of positive samples was significantly higher (17-21%) near sewage outfalls. Twenty-seven serotypes were isolated, including a new serotype named Salmonella grampian. The range and frequency of serotypes carried by gulls was similar to those in the human population, suggesting sewage as a possible source of gull infection. The number of salmonellae found in positive samples was low (0.18-191 g-1 faeces). This was similar to the numbers found in sewage, 10-80 1-1, suggesting gulls may only carry infected material without infecting themselves. Antibiotic resistance in the isolates was low, only 21 showing resistance to the antibiotics tested, although most of these were determined by resistance transfer plasmids.

Animals↗
PubMed1989

Numerical index of the discriminatory ability of biotyping for strains of Salmonella typhimurium and Salmonella paratyphi B.

An index of discrimination was used to assess the discriminatory power of biotyping for salmonellas of selected serotypes. Three collections of phage-typed strains of Salmonella typhimurium and Salmonella paratyphi B, previously tested for biotype, were examined. The results established that the discrimination index was high when full biotyping alone was used for differentiation of strains from international series. When biotyping was combined with phage typing, the discrimination achieved was greater than for either method used alone. These findings confirm that biotyping affords excellent discrimination of strains of S. typhimurium and S. paratyphi B and indicate that the results obtained from biotyping can be interpreted with confidence.

Animals↗
PubMed2001

Automated ribotyping and random amplified polymorphic DNA analysis for molecular typing of Salmonella enteritidis and Salmonella typhimurium strains isolated in Italy.

AIMS: The ability of automated ribotyping and random amplified polymorphic DNA (RAPD) analysis to differentiate Salmonella enteritidis and Salmonella typhimurium isolates in relation to their origin was evaluated. METHODS AND RESULTS: The restriction enzymes EcoRI, PvuII and PstI, and the random primers OPB17 and P1254, were tested for ribotyping and RAPD analysis, respectively. Seventeen subtypes were identified among the isolates of the two pathogenic Salmonella serovars using the RiboPrinter, and 25 subtypes using RAPD. CONCLUSIONS: The greatest degree of genetic diversity was observed among Salm. typhimurium isolates using both automated ribotyping (Simpson's index of discrimination 0878) and RAPD (Simpson's index of discrimination 0886). SIGNIFICANCE AND IMPACT OF THE STUDY: According to the results of this research, automated ribotyping and RAPD are two useful genotyping techniques for identifying unique and common subtypes associated with a specific source and location, and provide powerful tools for epidemiological investigations.

Animals↗
PubMedDate not supplied

Emergence of Salmonella epidemics: the problems related to Salmonella enterica serotype Enteritidis and multiple antibiotic resistance in other major serotypes.

Two major changes in the epidemiology of salmonellosis occurred in the second half of the 20th century: the emergence of food-borne human infections caused by S. Enteritidis and by multiple-antibiotic resistant strains of Salmonella. This review updates information on the S. Enteritidis pandemic and focuses on the emergence of Salmonella, carrying the SGI1 antibiotic resistance gene cluster, resistant to extended-spectrum cephalosporins, or resistant to fluoroquinolones. The factors responsible for the emergence of these Salmonella strains could be either of human origin or related to bacterial genome evolution. However, our increasing understanding of the molecular fluidity of the genome shows that any attempt to counteract bacteria results in further bacterial evolution or adaptation of other bacteria to take place in the new free ecological niche. In these conditions, we can ask who is faster: humans who want to eliminate bacterial pathogens or bacteria that continuously evolve to gain new niches.

Animals↗
PubMed2002

Salmonella enterica serovar Pullorum requires the Salmonella pathogenicity island 2 type III secretion system for virulence and carriage in the chicken.

Functional mutations were made in the type III secretion systems encoded by Salmonella pathogenicity island 1 (SPI 1) and Salmonella pathogenicity island 2 (SPI 2) of Salmonella enterica serovar Pullorum, the cause of pullorum disease in poultry. Their role in cell invasion in vitro, and in virulence in vivo was determined. The SPI 1 mutant showed decreased invasiveness for chicken cells but was capable of causing disease in orally infected 1-day-old chicks, although it showed some reduction in virulence. The SPI 2 mutant showed no reduction in invasiveness, but was fully attenuated for virulence in 1-day-old chicks, and was not detected following oral infection in 1-week-old chickens. Following intravenous infection, the SPI 2 mutant was also attenuated and cleared more rapidly than the parent strain. This indicates that S. Pullorum requires SPI 2 for virulence and persistence but SPI 1 appears to contribute to, but is not essential for, the virulence of S. Pullorum.

Animals↗