SEARCH · PubMed Health

Results for “Food samples”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources

PubMed2001

Salmonella, Shigella and growth potential of other food-borne pathogens in Ethiopian street vended foods.

OBJECTIVE: To evaluate the bacteriological safety of food items sold by street vendors with regard to Salmonella and Shigella and to assess the growth potential of some foodborne pathogens in some street foods. DESIGN: Collection of street-vended foods and laboratory based microbiological analysis. SETTING: Microbiology Laboratory, Department of Biology, Addis Ababa University, Addis Ababa, Ethiopia. RESULTS: Most of the street food samples had aerobic mesophilic counts >10(7) cfu/g. Nine "kitfo" and one "egg sandwich" samples yielded Salmonella. Shigella was isolated from three "macaroni" samples. The Salmonella isolates were sensitive to all ten drugs tested but the Shigella isolates had multiple resistance against five drugs. In a challenge study, Salmonella typhimurium, Shigella flexneri and Staphylococcus aureus grew in street-vended food samples to hazardous levels within eight to twelve hours. CONCLUSION: Street foods are heavily contaminated with micro-organisms and are potential sources of food borne infections. Health hazards from street foods may be significantly minimised by consumption within four hours of preparation.

Colony Count, Microbial↗

PubMed1994

[Content of trans-fatty acids in food].

The fatty acid composition of the fat in 197 food samples has been analyzed by gas liquid chromatography. The use of a 30 m capillary column coated with CPSil88 permitted the separation of the cis and trans isomers. The trans fatty acid content of milk and milk products ranged from 1.9 to 7.9%. Meat samples from ruminants contained 2.0-10.6% trans fatty acids. In pork fat the amounts were less than 0.5%. Sausages and other meat products contained high levels of pork fat. Therefore these samples contained less than 1% trans fatty acids, with the exception of some pure beef products. The amounts of trans fatty acids in foods which may contain hydrogenated oils ranged from 0 to 34.9%. In food samples with high levels of trans fatty acids lower contents of saturated fatty acids were analyzed.

Animals↗

PubMed1993

Examination of raw beef products for the presence of Vero cytotoxin producing Escherichia coli, particularly those of serogroup O157.

Fifty-four of 310 (17%) samples of raw beef products contained Vero cytotoxin (VT)-producing Escherichia coli (VTEC) detected by DNA probes for the VT genes. VTEC strains examined in detail from a selection of the positive samples belonged to several O serogroups, some of which have been associated with human diarrhoea or haemolytic uraemic syndrome. Some of the strains possessed properties that may contribute to virulence in man. None of the food samples contained VT-producing E. coli O157 when tested by a combination of VT probe tests and colony immunoblotting with commercially available anti-O157 serum. Quantification of the immunoblotting technique indicated that O157 VTEC could be recovered from artificially-inoculated meat samples at a level of less than one organism per gram. Five of the food samples carried E. coli O157 strains that did not produce VT and differed in other properties from O157 VTEC.

Animals↗

PubMed1997

Liquid chromatographic measurement of L-ascorbic acid and D-ascorbic acid in biological samples.

D- and L-Ascorbic acids have been separated using liquid chromatography (LC) on a polymer-coated silica-based NH2 column and the L-isomer has been quantified in human serum, rat serum, rat lung, rat lung perfusate, infant formula (SRM 1846) and mixed food sample (SRM 2383). The D-isomer was observed only in trace amounts in the mixed food sample. The results demonstrate that ascorbic acid was stable on the column and completely recovered from supplemented samples of human serum and that this method of analysis is accurate, precise and has broad application exhibiting no dependence on the nature of the matrices evaluated herein.

Animals↗

PubMed1978

Quantitative and qualitative evaluations of protein intake in a geriatric subpopulations from a southern Swedish community.

The daily intake of protein and the amino acid content of food samples collected in association with a dietary survey of male and female Swedish pensioners, were determined. Duplicate portions of 1-day, mixed food samples were collected. The samples were homogenized and the fat was extracted before lyophilization. Protein content was determined by a modified Kjeldahl method. Cysteine and methionine were determined by ion-exchange chromatography after performic acid oxidation follow by acid hydrolysis, whereas tryptophan was determined by a spectrofluorometric method. All other amino acids were analyzed by gas-liquid chromatography. Median protein intake was 0.69 g per person per kilograms of body weight per day for the male pensioners and 0.67 g per person per kilograms of body weight per day for the female pensioners and 0.67 g per person per kilograms of body weight per day for the female pensioners. The quality of protein consumed by the participants, determined by amino acid analysis, showed that lysine, threonine, and tryptophan were the limiting amino acids. The chemical score, when compared with the FAO reference protein, varied between 35 and 100 (mean = 77).

Aged↗

PubMed1984

Diet, nutrition intake, and metabolism in populations at high and low risk for colon cancer. Concordance of nutrient information obtained by different methods.

Data obtained from two vegetarian and two nonvegetarian populations by 24-h diet recall, 3-day weighed diet diary, analysis of 3-day composite food samples, and measurement of certain biochemical parameters were compared. Correlations for group means (both sexes combined) for values obtained by 24-h recall versus 3-day diet diary were protein, r = 0.96 and total calories r = 0.86. For 3-day diet diary with food analysis, protein r = 0.89, fat r = 0.90 and for reported protein intake with serum prealbumin r = 0.74, with urinary urea nitrogen r = 0.87. Correlations were low for comparisons of means of male groups for most parameters. Individual correlations for reported protein intake and biochemical parameters were lower for males than for females. This suggests that male subjects may require special attention to insure accuracy of reporting and specimen collection. These findings indicate comparability of data from 24-h recall and 3-day diary, and agreement of dietary records with certain biochemical parameters. Protein and fat intake as determined from chemical analysis of a composite food sample correlated well (r = 0.89; r = 0.90) with that calculated from food tables.

Adult↗

PubMed2006

Thermal degradation of the Fusarium mycotoxin deoxynivalenol.

Deoxynivalenol (DON) is a toxic secondary metabolite produced by molds of the Fusarium genus, which are able to infect cereal crops in the field. Concerning its rate of occurrence and mean concentration, DON is one of the most important mycotoxins in cereal commodities. Its toxic effects range from causing diarrhea, vomiting, and gastro-intestinal inflammation to noncompetitive inhibition of the biosynthesis of proteins in eukaryotic cells. To study the stability of DON under food-processing conditions such as cooking or baking, we performed model heating experiments and screened the residue for degradation products. Heating of DON and 3-acetyldeoxynivalenol (3-AcDON), especially under alkaline conditions, gave a mixture of compounds, which were isolated and structurally elucidated by NMR and MS experiments. Three of these compounds were already known (norDON A, norDON B, and norDON C), while four were new and named 9-hydroxymethyl DON lactone, norDON D, norDON E, and norDON F. The significance of the DON degradation products was checked by analyzing commercially available food samples. norDON A, B, and C were detected in 29-66% of the samples in mean concentrations ranging from 3 to 15 microg/kg. Furthermore, cell culture experiments using IHKE cells showed that the compounds that were detected in food samples are less cytotoxic in the formazan dye cytotoxicity assay compared to DON. Whereas DON revealed a median effective concentration (EC50) at 1.1 micromol/L, all other compounds did not show any significant effect up to 100 micromol/L. These findings indicate that the degradation of DON under thermal treatment might reduce the toxicity of DON contaminated food.

Cell Line, Transformed↗

PubMed2002

Improved detection of human enteric viruses in foods by RT-PCR.

Human enteric viruses (including hepatitis A virus (HAV) and Norwalk-like viruses (NLVs)) are now recognized as common causes of foodborne disease. While methods to detect these agents in clinical specimens have improved significantly over the last 10 years, applications to food samples have progressed more slowly. In an effort to improve the sensitivity and speed of virus detection from non-shellfish food commodities by reverse transcription-polymerase chain reaction (RT-PCR), we (i) evaluated multiple RNA extraction methods; (ii) compared alternative NLV primer sets; and (iii) developed a one-step RT-PCR method. Hamburger and lettuce samples, processed for virus concentration using a previously reported filtration-extraction-precipitation procedure, were inoculated with HAV or NV. Several RNA extraction methods (guanidinium isothiocyanate, microspin column, QIAshredder Homogenizer, and TRIzol) and primer pairs were compared for overall RNA yield (microg/ml), purity (A(260)/A(280)), and RT-PCR limits of detection. The use of TRIzol with the QIAshredder Homogenizer (TRIzol/Shred) yielded the best RT-PCR detection limits (<1 RT-PCR amplifiable units/reaction for NV), and the NVp110/NVp36 primer set was the most efficient for detecting NV from seeded food samples. A one-step RT-PCR protocol using the TRIzol/Shred extraction method and the NVp110/NVp36 or HAV3/HAV5 primer sets demonstrated improved sensitivity (>10-fold) over the routinely used two-step method. HAV RNA was detected by RT-PCR at initial inoculum levels corresponding to <10 and <100 PFU per 300 microl sample concentrate (corresponding to 6 g food sample) for hamburger and lettuce, respectively. NV RNA was detected by RT-PCR at initial inoculum levels <5 and <50 RT-PCR amplifiable units per 300 microl concentrate (corresponding to 6 g food sample) for hamburger and lettuce, respectively. Residual RT-PCR inhibitors were effectively removed as evidenced by the ability to detect viral RNA in food concentrates without prior dilution. The methods reported here show promise for rapid, sensitive detection of human enteric viruses in foods.

DNA Primers↗

PubMed2005

A high density microelectrode array biosensor for detection of E. coli O157:H7.

A high density microelectrode array biosensor was developed for the detection of Escherichia coli O157:H7. The biosensor was fabricated from (100) silicon with a 2 microm layer of thermal oxide as an insulating layer, an active area of 9.6 mm2 and consists of an interdigitated gold electrode array. The sensor surface was functionalised for bacterial detection using heterobifunctional crosslinkers and immobilised polyclonal antibodies to create a biological sensing surface. Bacteria suspended in solution became attached to the immobilised antibodies when the biosensor was tested in liquid samples. The change in impedance caused by the bacteria was measured over a frequency range of 100 Hz-10 M Hz. The biosensor was evaluated for E. coli O157:H7 detection in pure culture and inoculated food samples. The biosensor was able to discriminate between cellular concentrations of 10(4)-10(7)CFU/mL and has applications in detecting pathogens in food samples.

Antibodies↗

PubMed2004

Functional and safety aspects of Enterococci isolated from different Spanish foods.

The incidence and diversity of enterococci in retail food samples of meat, dairy and vegetable origin was investigated. Enterococci were present, at concentrations of 10(1) to 10(4) CFU/g. Fifty selected isolates from food samples grouped in two separate clusters by RAPD analysis. Cluster G1 (72% of the isolates) contained the E. faecium CECT 410T type strain, and also showed a high degree of genetic diversity. Cluster G2 (28% of the isolates) contained the E. faecalis CECT 481T type strain and was genetically more homogeneous. Virulence traits (haemolysin, gelatinase or DNAse activities, or the presence of structural genes cylL, ace, asal and esp) were not detected. All isolates were sensitive to the antibiotics ampicillin, penicillin, gentamicin, streptomycin and chloramphenicol. A high pecentage of isolates were resistant to erythromycin and rifampicin. Many isolates showed intermediate sensitivity to several antibiotics (tetracycline, ciprofloxacin, levofloxacin, or quinupristin/dalfopristin). Vancomycin and teicoplanin resistance was detected in one strain, but vanA, vanB, vanC1, vanC2 or vanC3 genes were not detected. Many of the isolates showed functional properties of food or health relevance. Production of antimicrobial substances was detected in 17 of the isolates, and 14 of them carried structural genes for enterocins A, B and/or P.

Cluster Analysis↗

PubMed1985

Probability of recovering pathogenic Escherichia coli from foods.

The probability of recovering pathogenic Escherichia coli from food by the Bacteriological Analytical Manual method was determined by the effects of several factors: the number of strains per food, the ability of pathogenic strains to survive enrichment, and the frequency of plasmid loss during enrichment. Biochemical patterns indicated the presence of about six E. coli strains per food sample. About half of the strains isolated from humans did not survive enrichment. Among those which grew, plasmid loss, as determined by gel electrophoresis and DNA colony hybridization, ranged from 20 to 95%. The combined effects of failure to survive enrichment and plasmid loss decreased the relative numbers of these strains and reduced the chance of detecting pathogens. To counteract this tendency and obtain a 90 to 95% probability off recovering a given pathogenic strain, 40 to 50 colonies per food sample should be picked during the routine testing of foods.

Anti-Bacterial Agents↗

PubMed2001

[Development of chromogenic agar medium for isolation of enterohaemorrhagic Escherichia coli O26].

Agar media for isolation of enterohaemorrhagic Escherichia coli (EHEC) have been developed primarily for E. coli O157, because this bacterium has most frequently caused EHEC infection. However, there have been few studies for isolation of other serotypes of EHEC, and media appropriate for isolation of such organisms, especially from food samples, are not yet available. Among such serotypes, E. coli O26 has often been isolated from clinical specimens from patients and animals, but not from food samples in outbreaks, because of lack of an appropriate method for isolation. In this study, we tried to develop a new chromogenic agar medium for selective isolation of E. coli O26 using the characteristics of E. coli O26. Fifteen strains of E. coli O26, 11 strains of E. coli O157 and 36 strains of other sero-types E. coli were tested for fermentation of rhamnose, cellobiose, dulcitol, salicin, raffinose, sorbitol, sucrose, lactose, mannitol, arabinose, maltose, xylose and glucose. Rhamnose was fermented by all E. coli strains except for E. coli O26. The other substrates were not effective for differentiating E. coli O26 from the other strains of E. coli. Thus the medium containing rhamnose and 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside, which is a substrate of beta-galactosidase specific to coliforms, produced a color of E. coli O26 colonies different from colors of the other bacteria. Furthermore, cefixime and sodium tellulite were added to the composition of the medium for gaining higher selectivity.

Agar↗

PubMed1991

Bacteriological safety of cook-chill food at the Royal Free Hospital, with particular reference to Listeria.

Cook-chill food prepared by the Catering Department of the Royal Free Hospital was examined over an 8-month period commencing October 1989. Total aerobic viable counts (TAVCs) were performed on 200 food specimens which were also examined for Listeria using selective enrichment culture. Ten of 200 food samples tested had TAVCs greater than 10(5) colony forming units (cfu) g-1, and nine of these were from non-vegetarian (meat) dishes. Although most of the food prepared by cook-chill had microbial loads within the limits recommended by current Department of Health guidelines (i.e. less than 10(5) cfu g-1), our findings for the non-vegetarian dishes suggest that extra caution is required when preparing such food. Listeria were not isolated from any food sample. In a survey of listeria faecal carriage, Listeria monocytogenes was isolated from only two of 100 faeces specimens obtained from patients.

Colony Count, Microbial↗

PubMed1999

Evaluation of TaqMan PCR assay for detecting Salmonella in raw meat and shrimp.

We evaluated the TaqMan Salmonella amplification/detection kit from PE Applied Biosystems, which uses a polymerase chain reaction (PCR) assay for rapid detection of Salmonella in food 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 system's sensitivity and specificity were evaluated using 42 serotypes of 68 Salmonella strains isolated from fecal samples from patients in Tokyo, Japan, and 39 non-Salmonella strains in 22 genera. There were no false-negative or false-positive results. This PCR assay can detect 3 CFU per PCR tube of Salmonella in pure culture (120 CFU/ml of TSB culture). PCR signals were attenuated with artificially contaminated shrimp, but a similar detection limit was obtained. TaqMan's performance was tested with 100 meat and chicken samples purchased from stores in Tokyo. Overall, two of the DNA extraction protocols (the Chelex and EnviroAmp methods) worked equally well, with some exceptions. Of the 100 samples analyzed, 10 were positive for Salmonella with both conventional culture methods and the kit and 89 were negative with both. One sample was negative by the culture method but positive by the kit assay. These results indicate that TaqMan is a reliable and rapid method for Salmonella analysis in the food industry. With this system, food samples can be analyzed for Salmonella in less than 20 h.

Animals↗

PubMed1996

A study of nosocomial diarrhea in Calcutta.

BACKGROUND: Nosocomial infection is a major problem in hospitalized patients, particularly those who are debilitated. These infections may manifest as diarrhea. The spectrum of infections agents causing nosocomial diarrhea in our country is not known. METHODS: Thirty-two patients, admitted to the hospital with various complaints, who developed diarrhea during their hospital stay, were studied to identify the causative agents of diarrhea. Hospital food samples were also processed for pathogens. RESULTS: The bacteria isolated from patients included established enteropathogens like Salmonella, enteropathogenic Escherichia coli, Campylobacter species and organisms with low pathogenicity like Serratia marsescens, Pseudomonas aeruginosa and Morganella morganii. The bacterial pathogens isolated were resistant to most antibiotics, suggesting their nosocomial character. Hospital food samples contained Salmonella typhimurium, Campylobacter jejuni (biotype 1) and enteropathogenic Escherichia coli, suggesting that food might have been the vehicle for these infections. CONCLUSION: Nosocomial infection was found to be an important cause of diarrhea (34%), EPEC and Salmonell being the predominant pathogens. Water, egg and milk were the source of infection in these cases. Special measures to obtain uneffected items will prevent occurrence of nosocomial diarrhea in our hospitals.

Adult↗

PubMed2006

Occurrence of proteolytic activity and N-acyl-homoserine lactone signals in the spoilage of aerobically chill-stored proteinaceous raw foods.

Proteolytic pseudomonads dominate the spoilage flora of aerobically chill-stored proteinaceous raw foods. Proteolysis during spoilage of these food systems affects both food quality and the dynamics of the bacterial community because it increases the availability of nutrients to the community as a whole. Quorum sensing, or cell-cell signaling, is associated closely with ecological interactions among bacteria in mixed communities. The potential role of quorum sensing in proteolytic food spoilage was examined, based on the evaluation of N-acyl-homoserine lactone (AHL) signal molecules. The occurrence of proteolytic activity and AHL signals was studied during spoilage of aerobically chill-stored ground beef, fish, chicken, and raw milk. Pseudomonads dominated the psychrotrophic flora, followed distantly by members of the Enterobacteriaceae. The growth of pseudomonads was correlated with the occurrence of proteolytic activity in all food systems. AHL concentration began increasing significantly only after the onset of proteolytic activity. Widely divergent AHL profiles were revealed by thin-layer chromatography analysis of the different food samples, and these profiles were likely determined by the undefined bacterial flora in these systems and by the characterized pseudomonads and Enterobacteriaceae. Although Hafnia alvei was a major component of the Enterobacteriaceae flora in all foods tested and a strong AHL producer, the signal molecules produced by H. alvei strain EB1 did not influence protease production by Pseudomonas fluorescens strain 395 in vitro. These results do not indicate any clear correlation between the overall detectable AHL signal molecules accumulated in the food samples and proteolytic activity.

4-Butyrolactone↗

PubMed1991

Application of polymyxin-coated polyester cloth to the semi-quantitation of Salmonella in processed foods.

A rapid and economical semi-quantitative test for Salmonella cells in foods is proposed. Food samples containing different levels of Salmonella cells were homogenized and serially diluted in enrichment broths and then incubated for about 20 h at 37 degrees C. The presence of Salmonella cells in each dilution was assayed by capturing deoxycholate-extracted Salmonella lipopolysaccharides on a sheet of polymyxin-coated polyester cloth, followed by colorimetric detection with an anti-Salmonella antibody-enzyme conjugate. The minimum dilutions which resulted in no detectable growth were correlated with the extent of Salmonella contamination in the food samples.

Colorimetry↗

PubMed1996

Multiplex PCR assay for the routine detection of Listeria in food.

The development and validation of a multiplex PCR assay for the detection of Listeria that can be employed in routine investigation of food samples are described. The assay, which employs a short culture enrichment step followed by isolation of bacterial cells and detection by multiplex PCR reaction, is highly sensitive and specific for the detection of Listeria monocytogenes and all other Listeria species. Over 350 food samples were tested in parallel by standard cultural procedures and the PCR assay, with no false-positive or false-negative results obtained with the PCR assay. Compared to the standard cultural methods the PCR assay is highly sensitive, cost effective and extremely rapid with results obtained within 48 h from sample receipt.

Food Microbiology↗