Evaluation of selective and non-selective enrichment PCR procedures for Salmonella detection

AIMS: To compare PCR combined with enrichment media with the standard microbiological techniques (SMT) and to determine the most sensitive method for the detection of Salmonella and the identification of Salm. typhimurium (ST), Salm. enteritidis (SE), Salm. gallinarum (SG) and Salm. pullorum (SP). METHODS AND RESULTS: We analysed 87 samples from poultry using PCR and SMT, PCR being performed from non-selective (NS) and Rappaport-Vassiliadis (RV) media. PCR-NS was less sensitive than PCR-RV and SMT for the detection and identification of Salmonella. PCR-RV detected more positive samples of Salmonella sp. than SMT but both these methods showed similar sensitivity regarding the identification of Salmonella serovars. CONCLUSIONS: PCR-RV was more sensitive and decreased the time necessary to detect and identify Salmonella. SIGNIFICANCE AND IMPACT OF THE STUDY: PCR-RV is a powerful tool for the rapid and accurate detection and identification of Salmonella and can be implemented in diagnostic and food analysis laboratories.     

Influence of octanoic acid addition to medium on some volatile compounds and PR-toxin biosynthesis by Penicillium roqueforti

AIMS: The present study describes the implementation of real-time PCR to tetrathionate broth enrichment step of Salmonella detection in poultry. METHODS AND RESULTS: Real-time PCR with Salmonella invA-specific primers and a standard bacteriological method was applied to detect Salmonella in tetrathionate enrichment cultures of 492 intestinal homogenates and 27 drag swabs from 47 poultry flocks. The number of positive individual samples by real-time PCR and culture method was 65 (12.5%) and 35 (6.8%), respectively. The number of Salmonella-positive flocks was 13 (27.7%) by both methods. PCR detection required 25 min for up to 32 samples. Melting curve analysis revealed the Tm for Salmonella-specific PCR product as 87 +/- 1 degrees C. CONCLUSIONS: Implementation of real-time PCR to tetrathionate broth enrichment step reduces the Salmonella detection time to 18 h and 25 min. Isolation of Salmonella should be carried out with PCR to determine the serovar. SIGNIFICANCE AND IMPACT OF THE STUDY: Real-time PCR is a powerful tool in rapid and accurate Salmonella monitoring in poultry companies, together with standard bacteriology.     

Isolation of Salmonella strains from reptile faeces and comparison of different culture media

AIMS: To provide information on epidemiology and isolation of Salmonella strains from reptiles. METHODS AND RESULTS: Ninety-one samples collected from reptiles of the zoo of Rome or belonging to private owners were analysed using a standard protocol for isolation of Salmonella from food. Salmonella strains were tested for susceptibility to 15 antimicrobics by a disc-agar diffusion method. Forty-six samples (50.5%) were positive for Salmonella. Of the 22 strains serotyped, 17 belonged to Salmonella enterica subsp. I, four to the subsp. IIIa and one strain resulted untypeable. Rappaport-Vassiliadis broth (RVB) allowed to recover more Salmonella strains when bacterial growth in buffered peptone water (BPW) was scarce, while selenite cystine broth (SCB) was more efficient, whereas growth in BPW was abundant. The maximum isolation score was obtained by plating onto xylose lysine desoxycholate agar (XLD). The strains exhibited resistance at high percentages to colistin sulphate (58.7%), sulphamethoxazole (55.5%), streptomycin (32.6%), tetracycline (19.6%), ampicillin (17.4%) and nalidixic acid (13.1%). CONCLUSIONS: A high prevalence of Salmonella in reptiles was observed. For isolation, the choice of the enrichment broth depending on the degree of growth in BPW followed by plating onto XLD may be suggested. SIGNIFICANCE AND IMPACT OF THE STUDY: This paper provides epidemiological data on the prevalence of Salmonella and laboratory protocols useful for isolation of Salmonella from faeces of reptiles.     

Adding a selective enrichment step to the iQ-Check real-time PCR improves the detection of Salmonella in naturally contaminated retail turkey meat products

AIMS: The aim of this study was to compare the real-time iQ-Check Salmonella kit (Bio-Rad) with the immunocapture assay RapidCheck Salmonella method, and a conventional culture method (FSIS, USDA) in detecting Salmonella in naturally contaminated turkey meat products. This study was also designed to determine if a selective enrichment step might improve the real-time detection of Salmonella. METHODS AND RESULTS: Using the culture method, Salmonella was recovered from 49 out of 99 retail turkey meat samples collected. RapidCheck failed to detect 11 Salmonella samples that were positive by the culture method. The iQ-Check real-time PCR also failed to detect three samples that were positive by the culture method. However, when carried out after a selective enrichment step, the iQ-Check real-time PCR detected all 49 Salmonella samples recovered by the culture method. The iQ-Check real-time PCR detected the presence of Salmonella in some samples that were not recovered by the culture method. CONCLUSIONS: Adding a selective enrichment step to the iQ-Check real-time PCR improves the detection of Salmonella in naturally contaminated turkey meat samples. SIGNIFICANCE AND IMPACT OF THE STUDY: The iQ-Check Salmonella real-time PCR can be used as a rapid method to monitor Salmonella in turkey meat, together with conventional culture methodology.     

Isolation of Salmonella from environmental samples collected in the reptile department of Antwerp Zoo using different selective methods

AIMS: To evaluate the environmental spread of Salmonella strains in the reptile department of Antwerp Zoo and to compare different isolation methods for Salmonella. METHODS AND RESULTS: One hundred environmental samples were collected in the service sections and public spaces of the reptile department. After pre-enrichment in buffered peptone water (BPW), selective enrichment was performed in Rappaport Vassiliadis Single Component Enrichment Broth (RVS), Selenite Cystine Broth (SEL) and Mueller Kauffman Tetrathionate Broth (MKTTn). Subculturing on Modified Semisolid Rappaport-Vassiliadis (MSRV) Medium, and the combined use of immunomagnetic separation (IMS) and RVS was evaluated. The isolation media used were Hektoen Enteric Agar (HE), Phenol Red Brilliant Green Agar (BG) and Xylose Lysine Decarboxylase Agar (XLD). Salmonella strains were found in 47 samples (47.0%). Most isolations were made on HE after combined IMS/RVS enrichment. Sixty-six Salmonella strains were serotyped, 29 belonged to Salmonella enterica ssp. enterica (I), 3 to ssp. salamae (II), 29 to ssp. arizonae or diarizonae (IIIa/b), 4 to ssp. houtenae (IV) and 1 strain showed autoagglutination. In addition, a 10-year survey (1995-2004) of Salmonella serovars isolated from reptiles at Antwerp Zoo is presented. CONCLUSIONS: A high prevalence of Salmonella strains was noted in the service sections of the reptile department. Only a few isolations were made in the public spaces. Selective enrichment in RVS was the most efficient. In combination with IMS, this method gave an even higher isolation rate than the International Standard method (ISO 6579:2002). SIGNIFICANCE AND IMPACT OF THE STUDY: This study confirms the importance of reptiles as spreaders of Salmonella in their surroundings. The possible infectious risks for zoo personnel and visitors are evaluated. Improved laboratory protocols for the isolation of Salmonella from the environment are suggested.     

Rapid detection of Salmonella spp. in food by use of the ISO-GRID hydrophobic grid membrane filter.

A rapid hydrophobic grid-membrane filter (HGMF) method was developed and compared with the Health Protection Branch cultural method for the detection of Salmonella spp. in 798 spiked samples and 265 naturally contaminated samples of food. With the HGMF method, Salmonella spp. were isolated from 618 of the spiked samples and 190 of the naturally contaminated samples. The conventional method recovered Salmonella spp. from 622 spiked samples and 204 unspiked samples. The isolation rates from Salmonella-positive samples for the two methods were not significantly different (94.6% overall for the HGMF method and 96.7% for the conventional approach), but the HGMF results were available in only 2 to 3 days after sample receipt compared with 3 to 4 days by the conventional method.     

LENTICULE discs provide a homogenous format for external quality assessment samples: a comparison with freeze-dried samples for shellfish microbiology

AIMS: The aim was to compare the variability in Escherichia coli enumeration data and detection of Salmonella spp. between four samples of LENTICULE discs and freeze-dried samples for the Health Protection Agency's External Quality Assessment (EQA) scheme for shellfish microbiology. METHODS AND RESULTS: Four samples of known but undisclosed microbiological content were dispatched in both freeze-dried and LENTICULE disc formats to 57 participating laboratories in 20 countries. Participants examined samples using their routine methods for the most probable number (MPN) of E. coli per 100 g and the presence/absence of Salmonella spp. There was no significant difference between the Food and Environmental Proficiency Testing Unit and participating laboratories for E. coli and Salmonella spp. results. There were significantly less outlying results using the LENTICULE discs than freeze-dried sample format and equivalent or less variance for the former for E. coli MPN. There was no significant difference between LENTICULE discs and freeze-dried samples for the presence/absence of Salmonella spp. CONCLUSIONS: Overall the results indicated that there was equivalent or less variance in results for the LENTICULE discs than for freeze-dried samples, therefore LENTICULE discs are a homogenous and stable matrix for EQA samples. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides validation data for the replacement of freeze-dried samples by LENTICULE discs for the Health Protection Agency Shellfish EQA Scheme.     

Evaluation of real-time PCR vs automated ELISA and a conventional culture method using a semi-solid medium for detection of Salmonella

AIMS: Evaluation of iQ-Check PCR Salmonella for Salmonella detection in artificially and naturally contaminated food and environmental field samples. METHODS AND RESULTS: Artificially contaminated samples (poultry meat and ground red meat) subjected to cold- and freeze-stress, and 120 naturally contaminated samples (swabs and meat) were tested for Salmonella using the diagnostic semi-solid Salmonella medium (DIASALM) method, the Vidas assay and the iQ-Check PCR assay after 24 h enrichment in buffered peptone water. CONCLUSIONS: Both the iQ-Check PCR and the Vidas assay provide a rapid and user friendly screening method for detection of Salmonella. False negative samples were obtained for the inoculated samples using both the iQ-Check PCR assay and the Vidas method when Salmonella cells were severely stressed. In total 45 of 120 naturally contaminated field samples showed Salmonella positive using the DIASALM method. The agreement percentage with the DIASALM method was respectively 92% for the iQ-Check PCR and 95% for the Vidas method. SIGNIFICANCE AND IMPACT OF THE STUDY: False-negative samples were obtained for the inoculated samples using both the iQ-Check PCR assay and the Vidas method when Salmonella cells were severely stressed, e.g. freezing at -18 degrees C for 7 days. Of the 120 naturally contaminated field samples 45 showed Salmonella positive using the DIASALM method. The agreement percentage with the DIASALM method was 92% for the iQ-Check PCR and 95% for the Vidas method respectively.     

A rapid monitoring assay for the detection of Salmonella spp. and Salmonella Senftenberg strain W775 in composts

AIMS: The composting process needs to be validated for its hygienic status in order to ensure that it is free of pathogens. Generally, this is evaluated through temperature monitoring, or additionally through active inoculation and monitoring of indicator organisms. We aimed to develop a monitoring method for the heat-resistant indicator organism Salmonella enterica ssp. enterica serovar Senftenberg strain W775 for detection in composting biowastes. METHODS AND RESULTS: The method development is comprised of: (i) optimization of molecular detection of bacteria belonging to the genus Salmonella; (ii) identification of a DNA marker for Salmonella strain W775; and (iii) development of a multiplex polymerase chain reaction (PCR)-based on both DNA markers. Subsequently, Salmonella strain W775 was inoculated and monitored during composting of biowastes in an industrial composting facility. CONCLUSIONS: A highly sensitive and specific detection of viable cells was obtained by enriching the compost sample prior to multiplex PCR analysis. Complete inactivation of Salmonella strain W775 was obtained within 4 days in an industrial composting facility at temperatures ranging between 41 and 57 degrees C. SIGNIFICANCE AND IMPACT OF THE STUDY: We describe a monitoring method for the simultaneous detection of naturally occurring Salmonella strains and artificially introduced Salmonella strain W775 in composting biowastes that can be applied in routine analysis.     

Public health investigations of Salmonella Enteritidis in catering raw shell eggs, 2002-2004

AIMS: In response to a dramatic change in the epidemiology of Salmonella Enteritidis in England and Wales thought to be associated with raw shell eggs, the Health Protection Agency initiated public health investigations to establish the incidence of Salmonella contamination and origin of eggs used by catering premises implicated in outbreaks of Salm. Enteritidis. METHODS AND RESULTS: Between October 2002 and November 2004, 16 971 eggs were sampled and Salmonella were recovered from 3.4%. Salmonella was isolated from 5.5% and 6.3% of Spanish and eggs of unknown origin, respectively, used in catering premises linked to outbreaks, a level significantly higher than that (1.1%) found in nonLion Quality UK eggs sampled. The small sample of UK Lion Quality eggs tested (reflecting their lack of use in premises visited) did not contain Salmonella. Several phage types of Salm. Enteritidis other than phage type 4 (PT 4) were identified with nonUK eggs. CONCLUSIONS: Eggs from Spain were implicated as a major source of infection. Eggs were contaminated more frequently with Salmonella when shells were dirty and/or cracked, and stored at above 8 degrees C. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of Spanish eggs by the catering sector has been identified as a consistent significant factor in many of the outbreaks caused by Salm. Enteritidis nonPT4 in England and Wales during 2002-2004. Advice to caterers and hospitals that raw shell eggs should not be used in food that will either not be cooked or only lightly cooked should be reinforced.     

Comparison of selective enrichment media for the detection of Salmonella in poultry faeces

AIMS: The aim of this study was to compare the results of semisolid media and Rappaport-Vassiliadis (RV) medium for the detection of Salmonella in faecal samples from broiler and layer flocks. METHODS AND RESULTS: Three different selective enrichment media were used: (a) RV medium; (b) diagnostic semisolid Salmonella medium (DIASALM) and (c) modified semisolid RV (MSRV) medium. The performance of DIASALM and MSRV was significantly better compared with RV. CONCLUSION: The results of this study indicate that approximately 95% of the samples containing Salmonella would be detected by a combination of a semisolid medium (MSRV or DIASALM) and RV. SIGNIFICANCE AND IMPACT OF THE STUDY: The International Standard method ISO 6579, including RV and selenite cystine broth as selective enrichment media, is most frequently used for the isolation of Salmonella from poultry faeces. This study reveals that there are more suitable combinations of selective enrichment media.     

Metabiosis of proteolytic moulds and Salmonella in raw,ripe tomatoes

AIMS: The aim of this study was to determine the survival and growth characteristics of Salmonella enterica in sound and chill-injured tomatoes as influenced by co-infection with proteolytic moulds. METHODS AND RESULTS: Sound (not chill injured) raw, ripe tomatoes (Lycopersicon esculentum Mill. 'Roma') were inoculated with a five-serotype mixture of S. enterica and/or Alternata alternata (two strains), Cladosporium herbarum and C. cladosporioides. Simultaneous and delayed (3 days) inoculation of tomatoes with Salmonella and each mould was studied. Growth of moulds in sound tomatoes stored at 15 and 25 degrees C for up to 10 days was accompanied by increased pH of radial pericarp tissue (pulp), which enhanced the growth of Salmonella. Growth of moulds and Salmonella at 25 degrees C was enhanced in chill-injured tomatoes compared with sound tomatoes. CONCLUSIONS: Growth of proteolytic moulds in tomatoes stored at conditions simulating those commonly used in commercial postharvest storage and handling promotes the growth of Salmonella that may be an incidental contaminant. SIGNIFICANCE AND IMPACT OF THE STUDY: Discarding tomatoes that are infected by moulds is important in handling and minimal processing practices designed to minimize the risk of human salmonellosis.     

Application of BAX system, Tecra Unique Salmonella test, and a conventional culture method for the detection of Salmonella in ready-to-eat and raw foods

AIMS: To compare the BAX system, the Tecra Unique Salmonella test, and a conventional culture method for the detection of Salmonella in various foods. METHODS AND RESULTS: Ready-to-eat and raw foods were inoculated with Salmonella serotype Typhimurium, Salmonella serotype Enteritidis, Salmonella serotype Typhi, or Salmonella serotype Derby. Incubated pre-enrichment cultures were examined using the BAX system, the Tecra Unique Salmonella test, and a conventional culture method. Salmonella could be detected in all ready-to-eat food samples inoculated with S. Typhimurium, S. Enteritidis, or S. Derby, with any of the three test methods. However, false negatives were obtained with the Tecra test and the culture method when samples with higher background flora were inoculated with S. Typhi. Sensitivity test results suggested the two rapid tests performed as well as the culture method in the detection of 10(1) CFU of S. Typhimurium in 25-g cooked or raw food. CONCLUSIONS: The BAX system and the Tecra Unique Salmonella test demonstrated results comparable with those of the culture method in the detection of Salmonella serotypes used except S. Typhi. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first evaluation of the BAX system, the Tecra Unique Salmonella test, and a culture method in the detection of Salmonella in a variety of western and oriental foods.     

Detection of Salmonella by indicator agar media and PCR as affected by alfalfa seed homogenates and native bacteria

AIMS: To investigate and prevent the undesirable effect of native bacteria and alfalfa seed homogenates on detection of Salmonella in alfalfa seeds by indicator agar media and polymerase chain reaction (PCR). METHODS AND RESULTS: The relative sensitivity of five indicator agar media, including modified semisolid RV (MSRV), xylose-lysine-Tergitol 4 (XLT4), Hektoen enteric agar (HEA), brilliant green agar (BGA) and bismuth sulphite agar (BSA), for detection of Salmonella in the presence of a large number of native bacteria from alfalfa seeds was examined. The detection limit as measured by the ratio between the numbers of native bacteria and Salmonella was estimated to be 10(6) to 1 for MSRV and 10(3) to 1 for XLT4, HEA, BGA or BSA. Presence of alfalfa seed homogenates markedly reduced the sensitivity of Salmonella detection by PCR. The minimal number of Salmonella detectable by PCR was determined to be 1-10 and 100-1000 CFU in the absence and presence of seed homogenate, respectively. Application of anti-Salmonella immunomagnetic beads permitted detection of 2-5 CFU of heat-injured cells in 25 g of seeds within 24 h by PCR. CONCLUSIONS: The MSRV medium is more sensitive than other indicator agars for detecting a small number of motile Salmonella in samples containing a large number of native bacteria. Application of immunomagnetic beads eliminates the PCR-inhibitory activity of seed homogenates and improves the detection of Salmonella in inoculated seeds. SIGNIFICANCE AND IMPACT: The results generated from this study will aid the seed distributors, sprout growers and public health officials to identify and recall the Salmonella-contaminated seed lots to be used for sprout production.     

Influence of phage population on the phage-mediated bioluminescent adenylate kinase (AK) assay for detection of bacteria

AIMS: The effect of phage concentration on the activity of adenylate kinase (AK) released from the cells lysed during infection was investigated in order to optimize a bioluminescent phage-mediated method for bacterial enumeration. METHODS AND RESULTS: The number of bacteria lysed by phages specific to Salmonella enteritidis and E. coli was determined using a bioluminescent method for the detection of AK released. In order to optimize the assay, the effect of phage concentration and time of infection on the amount of AK released was investigated. The release of AK was greatest at a multiplicity of infection (moi) of 10-100. CONCLUSION: The amount of AK released from Salmonella enteritidis and E. coli G2-2 cells by specific phages, SJ2 and AT20, respectively, depended on the type of bacteria, the stage of growth, the nature of phage, moi and time. SIGNIFICANCE AND IMPACT OF THE STUDY: An assay is described which allows detection of E. coli and Salmonella Enteritidis within 2 h at levels of 103 cfu ml-1.     

Comparison of the VIDAS system, FTA filter-based PCR and culture on SM ID for detecting Salmonella in Dermanyssus gallinae

AIMS: To compare different analytical methods for detecting Salmonella in Dermanyssus gallinae. METHODS AND RESULTS: The detection limit of three Salmonella detection methods [Vitek immunodiagnostic assay (VIDAS) Salmonella immuno-concentration/immunoassay, FTA filter-based PCR, and Salmonella detection and identification medium (SM ID) preceded by a pre-enrichment step] was evaluated by crushing mites in serial dilutions of pure cultures of Salmonella enterica ssp. Enterica serotype Enteritidis. Each method was then compared for its ability to detect Salmonella in artificially contaminated mites. In 105 mites artificially engorged with Salm. Enteritidis-contaminated blood, Salmonella was isolated from 68 samples of the samples cultured on SM ID and tests were positive for Salmonella using FTA filter-based PCR and VIDAS in 77 and 65 samples, respectively. Using SM ID as our reference method, specificities and sensitivities were 97% and 94% and 73% and 98.5% for VIDAS and PCR, respectively. CONCLUSIONS: Each method allowed the detection of Salmonella in contaminated mites and is usable for screening mites. PCR is more sensitive but less specific than VIDAS for detecting Salmonella. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first time that the VIDAS has been used to detect pathogens in vectors. The development of analytical methods for Salmonella detection in mites is a necessary step in the study of the role of D. gallinae as a vector of salmonellae and to check the contamination of D. gallinae in poultry facilities.     

Biofilm formation by Salmonella spp. and Listeria monocytogenes on plastic surface

AIMS: To investigate the biofilm formation by 122 Salmonella spp. and 48 Listeria monocytogenes strains on a plastic surface. METHODS: Quantification of biofilm formation was performed in brain heart infusion (BHI), trypcase soya broth (TSB), meat broth (MB) and 1/20 diluted trypcase soya broth (1/20-TSB) in plastic microtitre plates. RESULTS: All tested Salmonella spp. and L. monocytogenes strains produced biofilm in a suitable medium. However, the quantities of biofilm produced by Salmonella spp. were greater than those produced by tested L. monocytogenes strains. The nutrient content of the medium significantly influenced the quantity of produced biofilm. Diluted TSB was the most effective in promoting biofilm production by Salmonella spp., followed by TSB, while the least quantity of biofilm was formed in BHI and MB. L. monocytogenes produced the highest quantities of biofilm in BHI, followed by TSA, then MB, and the least quantities of biofilm were produced in 1/20-TSB. CONCLUSIONS: Salmonella spp. produces more biofilm in nutrient-poor medium, while L. monocytogenes produce more biofilm in nutrient-rich medium.     

Serotyping and RAPD profiles of Salmonella enterica isolates from Mauritius

AIMS: The genus Salmonella is a common agent of gastroenteritis in Mauritius, generating more cases of the disease during summer than during winter. The aims of this study were to assess the genetic diversity of isolates of Salmonella enterica by RAPD fingerprinting, and to establish the relationship between human and chicken isolates. METHODS: Twenty-six isolates were obtained from hospital laboratories and commercial poultry producers locally. RESULTS: The RAPD profiles, biochemical and serological analyses showed that two of the chicken isolates were mistakenly identified as Salmonella. The genetic diversity of the remaining 24 isolates (five chicken and 19 human), confirmed as Salmonella, was analysed using four arbitrary primers, OPA-10, OPR-03, OPI-06 and OPJ-09, chosen from an initial set of 10 decamers. Seventy RAPD markers were generated in four individual DNA profiles. SIGNIFICANCE AND IMPACT OF THE STUDY: Cluster analysis (UPGMA) performed using the NTSYS-pc V 1.8 computer software, confirmed that some strains of Salmonella isolated from chicken were genetically similar to those isolated from humans. Furthermore, a 1 kbp band amplified using primer OPA-10 was specific for the Salmonella genus as it was not amplified in any of the control bacteria.     

Tracing of Salmonella spp. in two pork slaughter and cutting plants using serotyping and macrorestriction genotyping

AIMS: The origin of Salmonella contamination of pork products is not well established. In order to further this knowledge, the transmission of Salmonella spp. from live pigs to pork cuts was investigated in two pork slaughter and cutting plants. METHODS AND RESULTS: Salmonella spp. were isolated from both pork (pigs, carcasses, cuts) and the environment before and during slaughterhouse activities. Eight serotypes were identified. XbaI and SpeI macrorestriction distinguished 20 genotypes of Salmonella Typhimurium and 16 genotypes of Salmonella Derby. A major cluster of Salmonella Typhimurium genotypes was common to both plants and all pig-related genotypes, while a predominant pig-related Salmonella Derby genotype was common to both plants. CONCLUSION: None of the Salmonella strains persisted for long periods in the pork-processing environments. SIGNIFICANCE AND IMPACT OF THE STUDY: This work shows that contaminated live pigs, because of bacterial spread due to the process and ineffective cleaning procedures, are involved in Salmonella contamination.     

Prevention of Salmonella cross-contamination in an oilmeal manufacturing plant

AIMS: The mechanisms of Salmonella contamination in an oilmeal plant were investigated and the basic data were collected in order to achieve control of Salmonella in oilmeal. METHODS AND RESULTS: Salmonella was detected in all contamination vectors and environmental factors investigated, namely: operators, processing floor, dust in the air and rodents. In particular, high concentrations of Salmonella were detected on the processing floor of the manufacturing area, which has high oil content. Steam was the most effective disinfection method used for the processing floor, as the effects of heat sterilization and disinfection may work in tandem. In addition, restricting the movement of operators of the production chain remarkably reduced Salmonella contamination, even in areas of otherwise high contamination. CONCLUSIONS: Within the oilmeal plant, high Salmonella contamination rates for the processing floor represent the greatest risk of contamination of oilmeal via operators, dust in the air and rodents. Therefore, control of the processing floor is the most important means for reducing the oilmeal contamination rate. SIGNIFICANCE AND IMPACT OF THE STUDY: Specific Salmonella control methods for oilmeal plants have been established.