Bacteriological quality and safety of raw milk in Malaysia

The microbiological safety of raw milk from 360 dairy farms in Peninsular Malaysia was determined. Milk samples were collected at 40 Milk Collection Centers (MCC) from four regions, namely, Southern (Johor/Melaka), Central (Selangor/Negeri Sembilan), Northern (Perak/Kedah) and Eastern (Kelantan/Terengganu) according to stratified random sampling design. Samples were analyzed for Total Plate Count (TPC), Staphylococcus aureus, coliform and Escherichia coli as well as the prevalence of selected pathogens such as Listeria monocytogenes, E. coli 015:H7 and Salmonella. The mean counts per ml for TPC, psychrotrophs and thermophiles were 12×10⁶, 7.5×10³ and 9.1×10³, respectively. A TPC less than 10⁶ cfu ml⁻¹ is used as a basic standard by MCC in the Price Incentive Programme. From the 930 milk samples tested, approximately 90% were contaminated by coliform bacteria and 65% were E. coli positive, with mean counts ranged from 10³ to 10⁴ cfu ml⁻¹. S. aureus was isolated from more than 60% of the samples and the mean count per ml was 12×10³. Meanwhile, E. coli 0157:H7 was also detected in 312 (33.5%) samples. However, Salmonella was only detected in 1.4% of the samples, with the Central region having the highest frequency of isolation. Thirteen Salmonella serotypes were identified, including S. muenchen, S. anatum and S. agona. A total of 47 strains of Listeria were isolated from 4.4% Listeria-positive samples including L. monocytogenes (1.9%), L. innocua (2.1%) and L. welshimeri (0.6%).     

In-milk inactivation of Escherichia coli O157:H7 by the environmental lytic bacteriophage ECPS-6

Shiga toxin-producing Escherichia coli is a common foodborne pathogen which transmission includes dairy products. In the search for novel biocontrol methods, bacteriophages have become important candidates for the eradication of foodborne pathogens. The aim of this study was to evaluate the bacteriophage-mediated reduction of E. coli O157:H7 in raw and filtered milk. Laboratory-scale tests showed that the bacteriophage ECPS-6 efficiently adsorbed to E. coli O157: H7 cells. Furthermore, ECPS-6 remained stable when heated at 70°C for 20 min and in a wide pH range from 3.0 to 11.0. The trials on contaminated milk were performed using filtered and unfiltered raw milk contaminated with 1 × 10⁵ CFU × ml⁻¹ of E. coli O157: H7. Bacteriophage was added at multiplicity of infection (MOI) 5 and 50. The ECPS-6 reached the highest lytic activity at MOI = 5 (25°C) which resulted in 4.74 Log₁₀ CFU × ml⁻¹ and 7.3 Log₁₀ CFU × ml⁻¹ reduction after 10 days for both tested strains, respectively. Under refrigerated conditions (4°C) the quantity of E. coli decreased to 1.5 Log₁₀ CFU × ml⁻¹ and 3.04 Log₁₀ CFU × ml⁻¹ for these strains, respectively. Usage of MOI = 50 for the treatment unfiltered milk led to the reduction of E. coli O157:H7 A-2 below the detection limit after 6 hr.     

Fate of Listeria on various food contact and noncontact surfaces when treated with bacteriophage

Study objective was to determine efficacy of a bacteriophage suspension against Listeria spp. when applied to three common types of materials used in food manufacturing facilities. Materials included two food contact materials (stainless steel and polyurethane thermoplastic belting) and one noncontact material (epoxy flooring). Coupons of each material were inoculated with a cocktail containing L. monocytogenes and L. innocua (4 to 5-log₁₀ CFU/cm²). Two phage concentrations and a control, 0, 2 × 10⁷ and 1 × 10⁸ PFU/cm² were evaluated. Treated samples were held at 4 or 20°C for 1 and 3 hr to determine the effect of temperature and treatment time. Reductions in Listeria populations ranged from 1.27 to 3.33 log₁₀ CFU/cm² on stainless steel, from 1.17 to 2.76 log₁₀ CFU/cm² on polyurethane thermoplastic belting, and from 1.19 to 1.76 log₁₀ CFU/cm² on epoxy resin flooring. Higher phage concentration (1 × 10⁸ PFU/cm²), longer treatment time (3 hr), and processing area temperature of 20°C showed a greater (p ≤ .05) reduction of Listeria on the stainless-steel and polyurethane thermoplastic belting coupons. Overall, Listeria reduction by phage treatment occurred on all three materials tested, under all conditions.     

Development of a rapid FLISA detection of Salmonella spp. based on CdTe/ZnS quantum dots

Salmonella pathogen is old and difficult to control in food safety. The study was aimed to develop a sensitive and rapid CdTe/ZnS quantum dots (QDs) mediated fluorescence-linked immunosorbent assay (FLISA) of Salmonella spp. The optical properties and structure of the CdTe/ZnS QDs were characterized by UV–Vis absorption spectroscopy and transmission electron microscopy. The emission peak wavelength is 575 nm. The CdTe/ZnS QDs-labeled secondary antibody (goat anti-rabbit IgG) was formed by biotin-avidin system. The detection limits of S. Enteritidis and artificial simulated samples are 1.0 × 10³ CFU/ml and 1.78 × 10³ CFU/ml, respectively. The study of FLISA stability shows that the antibody with QDs had very good activity when it was stored in the dark at 4°C for at least 35 days. The FLISA provides a new and easy-operated method for the rapid detection of Salmonella spp. and has broad application in food safety.     

Microbiological quality of fresh fruit and vegetable products in Catalonia (Spain) using normalised plate‐counting methods and real time polymerase chain reaction (QPCR)

BACKGROUND: Commercially available fruits and raw and ready‐to‐eat vegetables (n = 445) were examined for aerobic, coliform, and yeast and mould counts using normalised methods. Listeria spp., Listeria monocytogenes and Salmonella spp. were detected by real time polymerase chain reaction (QPCR) after enrichment. RESULTS: Aerobic plate counts ranged from < 10 to > 10⁹ colony‐forming units (CFU) g^?1, with the lowest and highest counts recorded for fruits and sprouts respectively. The highest incidence level of coliforms was found in ready‐to‐eat vegetables, with up to 65.7% of samples containing from 5 to 9 log₁₀CFU g^?1. Yeasts and moulds showed their highest incidence level between 5 and 6 log₁₀ CFU g^?1, with an overall range from < 2 to 9 log₁₀ CFU g^?1. Salmonella spp., Listeria spp. and L. monocytogenes were detected in 0.67, 2.7 and 0.9% respectively of the total samples examined. CONCLUSION: The samples analysed can be gathered into two main groups, one showing low microbial counts (fruits) and a second group (raw whole leaves and roots and packed ready‐to‐eat vegetables) with higher microbial contamination. Although incidence levels of pathogenic bacteria reported here are in the lower range of those reported elsewhere, positive detections highlight the importance of good hygienic measures throughout the whole food chain. Copyright © 2007 Society of Chemical Industry     

Comparison of Decontamination Efficacy of Antimicrobial Treatments for Beef Trimmings against Escherichia coli O157:H7 and 6 Non-O157 Shiga Toxin-Producing E. coli Serogroups

Abstract: The decontamination efficacy of 6 chemical treatments for beef trimmings were evaluated against Escherichia coli O157:H7 and 6 non‐O157 Shiga toxin‐producing E. coli (nSTEC) serogroups. Rifampicin‐resistant 4‐strain mixtures of E. coli O157:H7 and nSTEC serogroups O26, O45, O103, O111, O121, and O145 were separately inoculated (3 to 4 log CFU/cm²) onto trimmings (10 × 5 × 1 cm; approximately 100 g) fabricated from beef chuck rolls, and were immersed for 30 s in solutions of acidified sodium chlorite (0.1%, pH 2.5), peroxyacetic acid (0.02%, pH 3.8), sodium metasilicate (4%, pH 12.5), Bromitize^® Plus (0.0225% active bromine, pH 6.6), or AFTEC 3000 (pH 1.2), or for 5 s in SYNTRx 3300 (pH 1.0). Each antimicrobial was tested independently together with an untreated control. Results showed that all tested decontamination treatments were similarly effective against the 6 nSTEC serogroups as they were against E. coli O157:H7. Irrespective of pathogen inoculum, treatment of beef trimmings with acidified sodium chlorite, peroxyacetic acid, or sodium metasilicate effectively (P < 0.05) reduced initial pathogen counts (3.4 to 3.9 log CFU/cm²) by 0.7 to 1.0, 0.6 to 1.0, and 1.3 to 1.5 log CFU/cm², respectively. Reductions of pathogen counts (3.1 to 3.2 log CFU/cm²) by Bromitize Plus, AFTEC 3000, and SYNTRx 3300 were 0.1 to 0.4 log CFU/cm², depending on treatment. Findings of this study should be useful to regulatory authorities and the meat industry as they consider nSTEC contamination in beef trimmings. Practical Applications: Findings of this study should be useful to: (i) meat processors as they design and conduct studies to validate the efficacy of antimicrobial treatments to control pathogen contamination on fresh beef products; and (ii) regulatory agencies as they consider approaches for better control of the studied pathogens.     

The probiotic,Leuconostoc mesenteroides,inhibits Listeria monocytogenes biofilm formation

Listeria monocytogenes biofilm formation renders these cells highly resistant to current sanitation methods, and probiotics may be a promising approach to the efficient inhibition of Listeria biofilms. In the present study, three Leuconostoc mesenteroides strains of lactic acid bacteria isolated from kimchi were shown to be effective probiotics for inhibiting Listeria biofilm formation. Biofilms of two L. monocytogenes serotypes, 1/2a (ATCC15313) and 4b (ATCC19115), in dual-species culture with each probiotic strain were decreased by more than 40-fold as compared with single-species Listeria biofilms; for instance, a reduction from 5.4 × 10⁶ colony forming units (CFU)/cm² L. monocytogenes ATCC19115 in single-species biofilms to 1.1 × 10⁵ CFU/cm² in dual-species biofilms. Most likely, one of the Leuconostoc strains, L. mesenteroides W51, led to the highest Listeria biofilm inhibition without affecting the growth of L. monocytogenes. The cell-free supernatant from the L. mesenteroides W51 culture containing large protein molecules (>30 kDa) also inhibited Listeria biofilms. These data indicate that Leuconostoc probiotics can be used to repress L. monocytogenes biofilm contamination on surfaces at food processing facilities.     

Attachment and Biofilm Formation by Selected Strains of Salmonella enterica and Entrohemorrhagic Escherichia coli of Fresh Produce Origin

This study compared the abilities of selected Salmonella enterica and enterohemorrhagic Escherichia coli (EHEC) strains of fresh produce origin to form biofilms on polystyrene surface and to attach to alfalfa and bean sprouts. Each of the 7 S. enterica and 4 EHEC inocula (2 mL; 10⁷ CFU/mL) was placed in 6 different broths in 24‐well polystyrene tissue culture plates at 28 °C for 1 to 7 d. Developed biofilms were quantified using the crystal violet binding assay. In a separate experiment, alfalfa and mung bean sprouts (5 g) were exposed to 25 mL inocula (10⁷ CFU/mL) of S. enterica or EHEC at 22 °C for 2 h with shaking at 40 rpm. Contaminated sprouts were thoroughly rinsed and homogenized in 0.1% peptone water, and bacteria attached to sprouts were enumerated. Biofilm mass accumulated on polystyrene surface increased with incubation time (P < 0.05). Among the microbiological media used, LB no salt (NaCl) broth better supported biofilm development (P < 0.05). Two EHEC strains formed more biofilms than the Salmonella and other two EHEC strains (P < 0.05). However, more Salmonella cells (5.66 log CFU/g) attached to sprouts than EHEC cells (3.46 log CFU/g). Both Salmonella and EHEC attached in higher numbers to mung bean, than alfalfa, sprouts (P < 0.05).     

Bacteriological quality of individually quick-frozen (IQF) raw and cooked ready-to-eat shrimp produced from farm raised black tiger shrimp (Penaeus monodon)

One thousand, two hundred and sixty four samples of individually quick-frozen (IQF) peeled and deveined raw and 914 samples of cooked ready to eat shrimp samples produced from farm raised black tiger (Penaeus monodon) obtained from a seafood unit working under HACCP concept were analysed for total aerobic plate count (APC), coliform count,Escherichia coli, coagulase positive Staphylococci andSalmonella. The overall bacteriological quality of the product was found to be good. Of the frozen raw shrimp, 96% of samples showed APC below 10⁵while 99% of the frozen cooked ready-to-eat samples showed APC less than 10⁴. The APC ranged from 1.0×10²to 4.2×10⁶cfu/gm in frozen raw shrimp and from 1.0×10²to 6.4×1⁴cfu/gm in the frozen cooked shrimp. Prevalences of coliforms in raw shrimp and cooked shrimp samples were 14.4% and 2.9% respectively. The coliform count in raw products ranged from 1.0×10¹to 2.5×10³cfu/gm and in the cooked products, from 1.0×10¹to 1.8×10²cfu/gm. Although all the cooked shrimp samples were free of coagulase positive staphylococci,E. coliandSalmonella, 1.0, 2.0 and 0.1% of the frozen raw shrimp samples tested positive for coagulase positive Staphylococci,E. coliandSalmonellarespectively. TheSalmonellastrain was identified asSalmonella typhimurium. The results of the present study highlight the importance of implementation of HACCP system in the seafood industry to ensure consistent quality of frozen seafood.     

Antibacterial activity of the essential oil of Picea excelsa on Listeria,Staphylococcus aureus and coliform bacteria

Antibacterial activity of essential oil of Picea excelsa was tested with the dilution method against one strain of Listeria ivanovii, six of L. monocytogenes, three of Staphylococcus aureus, three of Escherichia coli, one of Klebsiella oxytoca, one of K. pneumoniae subsp. pneumoniae and one of Enterobacter cloacae. For Gram-positive bacteria in stationary phase, 0·07% of essential oil inhibited about 10⁵colony forming unit per ml; a dose of 0·2–0·3% was bactericidal for 10⁵–10⁷cells contained in 1 ml of liquid culture at 37°C. The coliforms, at a concentration of 10⁵CFU per ml, are resistant whatever the physiological age, since they grow with 8% of essential oil. A simplified technique gives good results for the determination of bactericidal activity against Listeria, only indication against S. aureus.     

Feasibility of colloidal silver SERS for rapid bacterial screening

This study reports the feasibility of citrate-reduced colloidal silver surface-enhanced Raman scattering (SERS) for differentiating three important food borne pathogens, E. coli, Listeria, and Salmonella. FT-Raman and SERS spectra of both silver colloids and colloid-K₃PO₄ mixtures were collected and analyzed to evaluate the reproducibility and stability of silver colloids fabricated in a batch-production process. The results suggest that the reproducibility of the colloids over the batch process is high and that their binding effectiveness remains consistent over a 60-day storage period. Two specific SERS bands at 712 and 390 cm⁻¹ were identified and used to develop simple 2-band ratios for differentiating E. coli-, Listeria-, and Salmonella-colloid mixtures with a 100% success. These results indicate that colloidal silver SERS technique may be a practical alternative method suitable for routine and rapid screening of E. coli, Listeria, and Salmonella bacteria.     

Detection of Salmonella enteritidis and Salmonella typhimurium in foods using a rapid,multiplex real-time recombinase polymerase amplification assay

Salmonella has been recognized as a major foodborne pathogen for humans and animals. In this study, a multiplex real-time recombinase polymerase amplification (RPA) was developed for simultaneous detection of Salmonella enterica serovars, Salmonella enteritidis and Salmonella typhimurium, from chicken, eggs, lettuce, and papaya. The reaction was performed for 20 min at 35°C, and the detection limit of the assay was 10² CFU/ml for pure culture. In food application, the limit of detection (LOD) of S. enteritidis and S. typhimurium using multiplex real-time RPA without enrichment procedure was 10² CFU/25 g, respectively. After enrichment, the LOD of S. enteritidis and S. typhimurium was 10 CFU/25 g. Moreover, the result for Salmonella spp. was not significantly different from those obtained using a culture-based method. Additionally, the assay has a lower cross-reactivity with other pathogenic microorganisms and a good stability performance. Thus, the developed multiplex RPA assay could be used as a rapid tool for the detection of S. enteritidis and S. typhimurium in food.     

Inactivation of biofilm cells of foodborne pathogens by steam pasteurization

The objective of this study was to evaluate the effect of steam pasteurization on the inactivation of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes biofilms on stainless steel and polyvinyl chloride (PVC). Biofilms were formed on a stainless steel and PVC coupon by using a mixture of three strains each of three foodborne pathogens. Six-day-old biofilms on stainless steel and PVC coupons were treated with steam at 75 and 85 °C for 5, 10, 20, 30, 40, and 50 s. Biofilm cells of E. coli O157:H7, S. Typhimurium, and L. monocytogenes on stainless steel were reduced by more than 6 log CFU/coupon after exposure to steam at 75 °C for 30, 40, and 30 s, respectively, and at 85 °C for 30, 20, and 20 s, respectively. Steam treatment resulted in less reduction in the levels of biofilm cells on PVC coupons. Biofilm cells of E. coli O157:H7, S. Typhimurium, and L. monocytogenes were reduced by 1.78, 2.04, and 1.29 log CFU/coupon, respectively, after 50 s of exposure to steam at 75 °C. Exposure to steam at 85° for 50 s reduced biofilm cells of E. coli O157:H7, S. Typhimurium, and L. monocytogenes by 2.53, 3.01, and 1.70 log CFU/coupon, respectively. The results of this study suggest that steam pasteurization has potential as a biofilm control method by the food industry.     

Use of Fluorogenic Assays for the Enumeration of Escherichia coli from Selected Seafoods

Escherichia coli was enumerated and immediately confirmed by incorporating 4-methylumbelliferone glucuronide (MUG) into Lactose Broth (LB), Violet Red Bile Agar (VRB) and M-Endo Broth (M-Endo) in selected seafoods. E. coli in the seafood samples ranged from 1.0 × 10¹– 1.0 × 10³ Most Probable Number (MPN)/g, 1.0 × 10¹– 3.5 × 10² cfu/g and 0.9 × 10¹– 2.8 × 10² cfu/g in LB-MUG, VRB-MUG, and M-Endo-MUG, respectively. Although not statistically significant (α= 0.05), LB-MUG resulted in higher counts in fresh finfish, frozen fish and breaded seafoods. Specificity for E. coli in LB-MUG, VRB-MUG and M-Endo MUG was 96.5%, 92.0%, and 90.0%, respectively. All three fluorogenic assays enabled a rapid and sensitive enumeration of E. coli from seafood products.     

Comparative study on decontamination of mixed feeds by radicidation and by pelletisation

Feed components contaminated with Salmonella act as vehicles in the transmission of these bacteria to animals and hence to meat and poultry. Sanitary improvements in processing, bagging and storage do not always effectively reduce Salmonella contamination rates and therefore ingredients or mixed feed should be decontaminated at the end of processing. Enumeration of Enterobacteriaceae was used to assay the decontamination effect of pelletisation of mixed feed. A working temperature over 80° usually reduced the bacterial count by a factor of 10⁵; lower temperatures currently used, reduced it by a factor of 10³ only. In similar dose-range-finding tests on decontamination with ⁶⁰Co gamma rays, about 0.5 Mrad were required for reductions in the counts of the most resistant Enterobacteriaceae by a factor of 10⁵. Survival curves being usually non-linear, ‘gross effective dose’ had to be used as a parameter. Neither loss of nutritive value nor the occurrence of orally toxic factors was observed when rats were fed for 2 years on a ration containing 35% fishmeal irradiated at 0.8 Mrad. A combination of improved sanitation, pelletising at the highest possible temperature and, if still required, terminal low-dose irradiation of the hermetically bagged material seems, therefore, a promising approach to the manufacture of Salmonella-free feeds.     

Simultaneous Detection of Salmonella,Listeria monocytogenes,and Staphylococcus aureus by Multiplex Real-Time PCR Assays Using High-Resolution Melting

A method combining multiplex real-time polymerase chain reaction (PCR) with high-resolution melting (HRM) analysis for rapid and specific simultaneous detection of Salmonella, Listeria monocytogenes, and Staphylococcus aureus was developed. The method included a melting-curve analysis of products and was evaluated by specificity, sensitivity and reproducibility analyses. Sensitivity and reproducibility analyses was both conducted by genomic DNA extracted from serial dilutions for each target pathogen. Assays with artificially inoculated and naturally contaminated samples after enrichment were also conducted. In the specificity test, there was no nonspecific amplification of the 44 nontarget pathogens, whereas the actual T _m values were 79.38?±?0.14, 82.54?±?0.15, and 77.36?±?0.14 °C for Salmonella, L. monocytogenes, and S. aureus, respectively. The sensitivity of the method was 3.5?×?10² CFU ml^?1 for Salmonella and L. monocytogenes and 3.5?×?10³ CFU ml^?1 for S. aureus. The coefficients of variation of T _m values ranged 0.51–1.03 % for Salmonella, 1.63–2.11 % for L. monocytogenes, and 0.75–2.17 % for S. aureus in intraassay, and ranged 0.81–2.43 % for Salmonella, 1.97–2.35 % for L. monocytogenes, and 0.93–3.93 % for S. aureus in interassay. The detection limit in artificially inoculated samples (n?=?50) was 5 CFU (25 g)^?1 food for the three tested pathogens. In the naturally contaminated samples (n?=?120),Salmonella DNA was detected by HRM, sequencing, and conventional culture-based methods at a positive rate of 25.00, 25.00, and 24.17 %, respectively; the corresponding rates for L. monocytogenes were 14.17, 14.17, and 14.17 %, respectively, while those for S. aureus were 16.7, 16.7, and 16.7 %, respectively.     

Fate of Escherichia coli O157: H7 in Chinese-Style Sausage During the Drying Step of the Manufacturing Process as Affected by the Drying Condition and Curing Agent

In this study, Chinese-style sausage was subjected to three different air-blast drying conditions commonly employed during the manufacturing process. The fate of Escherichia coli O157: H7 during the drying period was determined and compared. The effect of curing agents on the survival of E coli O157: H7 was also identified. Results showed that populations of E coli O157: H7 decreased ca 1.51 Log CFU g^-1 in sausage containing curing agents after a 6-h drying period at 50°C. However, the number of viable cells of E coli O157: H7 increased slightly in sausage without curing agents. When subjected to air-blast drying at 55°C for 6 h or at 55°C for 2·5 h and then 60°C for 3·5 h, a reduction in the number of viable cells of E coli O157: H7 was observed in sausage with or without curing agents. The reduction was more significant in sausage containing curing agents than in those without curing agents. No viable E coli O157: H7 was detected after 6 h of drying in samples containing curing agents, while the control samples still contained a viable E coli O157: H7 population of ca 2·65–4·36 Log CFU g^-1. After drying the sausage at 55°C for 4 h, inactivation of E coli O157: H7 increased in the presence of 30·00 g kg^-1 sodium chloride or 1·50 g kg^-1 sodium sorbate. On the other hand, the presence of 0·07–0·15 g kg^-1 sodium nitrite did not increase the inactivation of E coli O157: H7 compared to that in the control. © 1997 SCI.     

Quantification of Plesiomonas shigelloides in Pure Culture and Clams by Competitive PCR

A quantitative assay for Plesiomonas shigelloides in pure culture and clams based on the competitive polymerase chain reaction was developed. This is the first report for quantitative detection of P. shigelloides by competitive PCR. Forward (PS-F), reverse (PS23RV3), and hybrid primers were designed, and the specificity of the forward and reverse primer for P. shigelloides was proven. An internal standard DNA sequence was synthesized by PCR, with the hybrid primer as the forward primers and PS23RV3 as the reverse primer. A single concentration (0.588 pg/PCR) of internal standard (IS) was used for competitive PCR. The lowest level of detection of P. shigelloides was 80 CFU per PCR in pure culture, 240 CFU/g of clam tissue without enrichment, and 40 CFU/g of clam tissue after 7 hrs. nonselective enrichment at 37°C. There was a linear relationship between the log of the ratio of the relative fluorescent intensities of amplified target DNA bands to the internal standard DNA bands (IS) and the log of the CFU within a certain range in pure cultures and in clam tissue either with or without enrichment. The linear range with cells from a pure culture was the DNA derived from 8.0 × 10¹ to 8.0 × 10⁴ CFU per PCR while with clam tissue, the linear range was the DNA derived from 2.4 × 10² to 2.4 × 10⁵ CFU/g of tissue (1.2 × 10¹ to 1.2 × 10⁴ CFU per PCR) without enrichment, and 4.0 × 10¹ to 1.2 × 10⁴ CFU/g of clam tissue with enrichment, respectively.     

Untersuchungen zum mikrobiellen und viralen Kontaminationsstatus von Garnelen aus Aquakultur

In der vorliegenden Untersuchung wurden 111 Proben roher, aus Drittl?ndern importierter Garnelen aus Aquakultur auf bakterielle Erreger und auf humanpathogene Viren untersucht. Die Garnelen stammten bis auf acht lateinamerikanische Proben aus Südostasien. Am h?ufigsten waren Proben aus Bangladesh vertreten (n=40). Das Untersuchungsspektrum umfasste die Ermittlung des aeroben mesophilen Gesamtkeimgehalts, die quantitative Untersuchung auf Escherichia coli und Staphylococcus aureus und den qualitativen Nachweis von Salmonella spp., Vibrio spp. und Listeria monocytogenes. Der Nachweis des humanpathogenen Rotavirus, des Norovirus und des Hepatitis A-Virus erfolgten jeweils mittels einer nested RT-PCR. Bei den untersuchten Proben wurden Gesamtkeimgehalte von 4,8×10² bis 1,3×10⁹ KbE/g ermittelt. Davon hatten vierzehn Proben (12,6%) einen aeroben mesophilen Gesamtkeimgehalt >10⁷ KbE/g. In einer Probe konnte Escherichia coli mit einer Keimzahl von 1,9×10³ KbE/g isoliert werden. In 16 Proben wurde Staphylococcus aureus nachgewiesen. Aus keiner der Garnelenproben lie? sich Listeria monocytogenes isolieren. Salmonella spp. war in acht der untersuchten Proben nachweisbar. Das am h?ufigsten isolierte Serovar war Salmonella Weltevreden.     

Inhibitory effects of UV treatment and a combination of UV and dry heat against pathogens on stainless steel and polypropylene surfaces

Abstract: Pathogens that contaminate the surfaces of food utensils may contribute to the occurrence of foodborne disease outbreaks. We investigated the efficacy of UV treatment combined with dry heat (50 °C) for inhibiting 5 foodborne pathogens (Escherichia coli O157:H7, Salmonella Typhimurium, Pseudomonas aeruginosa, Listeria monocytogenes, and Staphylococcus aureus) on stainless steel and polypropylene surfaces in this study. We inoculated substrates with each of the 5 foodborne pathogens cultured on agar surface and then UV treatment alone or a combination of both UV and dry heat (50 °C) was applied for 30 min, 1 h, 2 h, and 3 h. The initial populations of the 5 pathogens before treatment were 8.02 to 9.18 and 8.73 to 9.16 log₁₀ CFU/coupon on the surfaces of stainless steel and polypropylene coupons, respectively. UV treatments for 3 h significantly inhibited S. Typhimurium, L. monocytogenes, and S. aureus on the stainless steel by 3.06, 2.18, and 2.70 log₁₀ CFU/coupon, and S. aureus on the polypropylene by 3.11 log₁₀ CFU/coupon, respectively. The inhibitory effects of the combined UV and dry heat treatment (50 °C) increased as treatment time increased, yielding significant reductions in all samples treated for 3 h, with the exception of S. aureus on polypropylene. The reduction level of E. coli O157:H7 treated for 3 h on the surface of stainless steel and polypropylene treated was approximately 6.00 log₁₀ CFU/coupon. These results indicate that combined UV and dry heat (50 °C) treatments may be effective for controlling microbial contamination on utensils and cooking equipment surfaces as well as in other related environments.