Microbiological contamination of sheep carcases in Finland by excision and swabbing sampling

The aims of this study were to provide data on the microbiological contamination of sheep carcases slaughtered in Finland, and to compare excision and swabbing methods for microbiological sampling of sheep carcases. The results were also compared to the requirements laid down in Regulation (EC) No 2073/2005. A number of 50 sheep carcases were sampled both by excision and by swabbing with gauze at four slaughterhouses. The samples were analysed for total viable counts (TVC's), Enterobacteriaceae, and Escherichia coli. The same carcases were also sampled for Salmonella spp. by swabbing. The mean levels of TVC's and Enterobacteriaceae, and the results for Salmonella spp. were in line with the requirements laid down in Regulation (EC) No 2073/2005. The mean levels of TVC's for samples by excision and by swabbing were 3.77 log CFU/cm² and 3.16 log CFU/cm², respectively. Enterobacteriaceae were recovered from 72% and 76% of the carcases, and E. coli from 48% and 61% by excision and swabbing, respectively. No carcases were found positive for Salmonella spp. The mean levels of TVC's, Enterobacteriaceae and E. coli were significantly higher for the samples by excision than for the samples by swabbing. When the relationship between the sampling methods were analysed, the results for excision samples and swabbing samples were related for the TVC's, and there was a significant correlation between the sampling methods for Enterobacteriaceae. The results suggest that swabbing by gauze can be used as an alternative sampling method to excision. In addition, a significant correlation was seen between the results for Enterobacteriaceae and E. coli for the samples collected by swabbing, suggesting that E. coli can be used as an indicator bacterium instead for Enterobaceteriaceae for sampling of sheep carcases by swabbing.     

Radiofrequency pasteurization of inoculated ground beef homogenate

Inactivation of nonpathogenic Escherichia coli in ground beef homogenate using radio-frequency (RF) heating both individually and in combination with antimicrobial treatments was investigated. Beef homogenate was prepared in phosphate buffer (pH 5.8). Inoculated beef homogenate was heated in an RF oven without antimicrobials to end-point temperatures of 50 °C resulting in 0.84 log reductions and 55 °C resulting in 0.94 log reductions. Adding antimicrobials-potassium, sodium, and ammonium bicarbonates (0.5 and 1.5%); citric acid (0.5%); potassium lactate (2.5%); and a blend of potassium bicarbonate (1.5%) and citric acid (0.5%) to the beef homogenates before RF heating did not inactivate E. coli. E. coli inactivation was also not affected in beef homogenates containing antimicrobials when heated to 50 °C in the RF oven. Heating to 55 °C did reduce E. coli more than 5 log (CFU/mL) reduction of E. coli in homogenates containing 2.5% potassium bicarbonate, 0.5% citric acid, and blends of citric acid and potassium bicarbonate at varying concentrations (0.5% citric acid + 0.5% Citric acid and 1.5% bicarbonate). This study offers scope and potential for the application of RF assisted pasteurization with antimicrobial systems as interventions to enhance the overall ground beef safety. The findings of this study should provide potential to explore industrial scale RF pasteurization of beef and other meat products while ensuring that the quality characteristics are maintained.     

Inactivation of Escherichia coli O157:H7 during cooking of non-intact beef treated with tenderization/marination and flavoring ingredients

This study examined the effect of tenderizing/marinating and flavoring ingredients on thermal inactivation of Escherichia coli O157:H7 in a lean ground beef model system, simulating non-intact products. Ground beef (3% fat) was inoculated with E. coli O157:H7 (5 strains; 6–7 log CFU/g), followed by mixing with nothing (control) or solutions of water, a mixture of flavoring agents (FA), 0.23% calcium chloride (CC) + FA, CC + FA + 0.3% acetic acid (AA), 0.5% sodium chloride (NaCl) + 0.25% sodium tripolyphosphate (STP), NaCl + STP + FA, NaCl + STP + 1.8% potassium lactate (PL), NaCl + STP + PL + FA, NaCl + STP + PL + AA, and NaCl + STP + PL + AA + FA. Samples (30 g) were extruded into tubes, stored (4 °C) overnight, and cooked to 60 °C (rare) or 65 °C (medium-rare) in a water bath. Cooking weight losses, and fat and moisture contents, water activity, pH, and total bacterial and E. coli O157:H7 populations were determined after inoculation, after storage, and after heating. Reductions of the pathogen at 60 °C in acid (AA)-treated samples were higher than reductions obtained in samples not treated with acid. Surviving pathogen counts at 65 °C in NaCl and STP-treated samples with no acid were higher (P < 0.05) than those of samples of all other tested treatments; however, the counts decreased to 0.7–1.6 log CFU/g when AA was added. Overall, the results of the study indicate that tenderizing/flavoring ingredient formulations combined with 0.3% AA (i.e., CC + FA + AA, NaCl + STP + PL + AA, and NaCl + STP + PL + AA + FA) enhanced destruction of E. coli O157:H7 during cooking of a non-intact beef product.     

Quality attributes and thermal inactivation of Shiga toxin-producing Escherichia coli in moisture enhanced,non-intact beef products are affected by pump rate,internal temperature,and resting time after cooking

Escherichia coli O157:H7 (ECOH) and non-O157-Shiga toxin-producing E. coli (STEC) may move from the surface of beef to the internal tissue during non-intact moisture enhancement processes. Little is known about the thermal inactivation of ECOH and non-O157-STEC in moisture-enhanced, non-intact beef. Our study evaluated the pump rate, internal temperature, resting time to inactivate ECOH and non-O157-STEC, and the resulting quality attributes of non-intact beef. Fresh 1 kg coarse-ground beef knuckles, inoculated with ECOH or a six-strain mixture of non-O157-STEC, were mixed with sodium chloride and sodium tripolyphosphate solutions to reach a 10 or 18% pump rate. The semi-frozen beef was cut, vacuum-packaged, frozen, and tempered before double pan-broiling to internal temperatures of 55, 60, 65, or 71.1 °C with 0.5 or 3.5 min rest. We analyzed pathogen survival on tryptic soy agar, MacConkey agar, and sorbitol MacConkey agar plus sodium pyruvate (0.1%). We also monitored color changes in the raw and cooked beef. We analyzed our data (two replicates of three samples each) using the Mixed Model Procedure of SAS including independent variables and interactions. ECOH and non-O157-STEC respond similarly (P = 0.518) to thermal treatments. Cooked internal temperatures of 65 and 71.1 °C achieved higher reductions in the pathogen (4.76–5.21 log CFU/g) compared to temperatures of 55 and 60 °C (2.43–3.53 log CFU/g) regardless of the pump rate and resting time (P = 0.001). A 3.5 min resting time (P = 0.007) or 18% pump rate (P = 0.008) achieved an additional 0.5 log CFU/g reduction among the various internal temperatures. The beef maintained a similar internal color regardless of the pump rate or cooked internal temperatures. These findings will be useful for the U.S. Department of Agriculture, Food Safety and Inspection Service to develop risk assessments for ECOH and non-O157-STEC on non-intact beef.     

Comparison of two plain soap types for removal of bacteria and viruses from hands with specific focus on food service environments

Handwashing (HW) is a long established and widely accepted method to prevent disease transmission. Ensuring effectiveness of current HW methods is essential for the optimization of HW and enhanced disease prevention. The objective of this research was to determine the difference in microbial reduction between plain foaming and liquid handsoap. The hands of 24 participants were inoculated by the palmar surface method with an average of 1.25 × 10⁸ CFU Escherichia coli C3000 or 1.36 × 10⁸ PFU MS2 bacteriophage. Participants washed their hands following a standard protocol with a standardized soap volume and a 10 s HW time. A glove juice method was used to recover microorganisms from hands. Remaining microorganisms were quantified by standard spread plate and plaque assays for E. coli and MS2, respectively. Hands inoculated with E. coli had an average log reduction of 2.76 ± 0.70 and 2.52 ± 0.58 log CFU for foaming and liquid handsoap, respectively. The mean log reduction for hands inoculated with MS2 was 2.10 ± 0.57 and 2.23 ± 0.51 log PFU for foaming and liquid handsoap, respectively. Data indicate no significant difference in overall microbial removal when comparing the efficacy of plain foaming and liquid handsoap. However, regardless of soap type, the type of microorganism impacted overall log reduction with a greater reduction for E. coli when compared to MS2 with a significant difference (p = 0.0008) in reduction for foaming handsoap. This study is the first comparison of the efficacy of plain liquid and foaming handsoap for microbial reduction on hands during HW.     

Antimicrobial effect of cranberry juice and extracts

The antimicrobial effect of cranberry juice and of three cranberry extracts (water-soluble (E1) and apolar phenolic compounds (E2), and anthocyanins (E3)) was investigated against seven bacterial strains (Enterococcus faecium resistant to vancomycin (ERV), Escherichia coli O157:H7 EDL 933, Escherichia coli ATCC 25922, Listeria monocytogenes HPB 2812, Pseudomonas aeruginosa ATCC 15442, Salmonella Typhimurium SL1344, and Staphylococcus aureus ATCC 29213). Each cranberry sample was analyzed to determine the minimum inhibitory concentration (MIC) and the maximal tolerated concentration (MTC) at neutral pH. The results, reported in μg phenol/mL, indicated that all the bacterial strains, both Gram-positive and Gram-negative, were selectively inhibited by the cranberry phenolic compounds. The extract rich in water-soluble phenolic compounds caused the most important growth inhibitions. The bacteria ERV, and to a lesser degree, P. aeruginosa, S. aureus and E. coli ATCC 25922, were the most sensitive to the antimicrobial activity of extract E1. The growth of P. aeruginosa and E. coli ATCC was also affected by the presence of the anthocyanin-rich cranberry extract E3, although the observed antibacterial effect was not as important as with extract E1. In general, L. monocytogenes, E. coli O157:H7 and S. Typhimurium were the most resistant to the antibacterial activity of the cranberry extracts. Within 30 min of exposure with pure neutralized cranberry juice, L. monocytogenes and ERV were completely inactivated.     

Antimicrobial action and effects on beef quality attributes of a gaseous ozone treatment at refrigeration temperatures

The effects of gaseous ozone treatment at refrigeration temperatures, on microbial counts (total aerobic mesophilic heterotrophic microorganisms and inoculated Escherichia coli) in culture media and in beef samples were analyzed. The influence of ozone on beef quality properties such as surface color and rancidity was measured.The effect of gaseous ozone (154 × 10^?6 kg m^?3) in culture media inoculated with E. coli after 3- or 24-h treatment at 0° and 4 °C caused a total inactivation of this microorganism.For beef samples treated with the same gaseous ozone concentration, the highest microbial inhibition was observed at 0 °C and after 24-h exposure, producing a decrease of 0.7 and 2.0 log₁₀ cycles in E. coli and total aerobic mesophilic heterotrophic microorganism counts respectively; however, both the surface color and lipid oxidation of these beef samples were unacceptable. Shorter exposure times (3 h) to the tested ozone concentration at both temperatures (0–4 °C), reduced 0.5 log₁₀ cycles the counts of total aerobic mesophilic heterotrophic microorganisms and 0.6–1.0 log₁₀ cycles the counts of E. coli, without changing the color or producing rancidity in beef.     

Pathogen reductions associated with traditional processing of landjäger

To determine if traditional processing would reduce Escherichia coli O157:H7 (EC), Listeria monocytogenes (LM), and Salmonella spp. (S) in landjäger, beef and pork trim (95% lean) and pork fat was experimentally-inoculated to obtain a pathogen population of ca. 8 log₁₀ CFU/g. The trim was spray-treated with 4.5% lactic acid (30 min, 25 °C), ground, mixed with seasonings, and a starter culture added. Sausages were stuffed, pressed, fermented (to pH 4.8), cold smoked, and dried to a water activity of 0.88. Sausages were vacuum packaged, stored (20 days, ca. 23 °C), and evaluated for microbial populations, pH, and water activity. Lactic acid treatment of beef trim reduced EC, S, and LM 0.23, 0.42, and 0.22 log₁₀ CFU/g, respectively. Subsequent fermentation and drying reduced EC, LM, and S 3.94, 4.11, and 4.29 log₁₀ CFU/g respectively. Average log reductions of 7.83, 6.19, and 7.21 log₁₀ CFU/g were observed for EC, LM and S, respectively, for the duration of the study. This study demonstrates that traditional processing of landjäger may result in a ca. 5 log reduction of foodborne pathogens.     

Modeling the inactivation of Escherichia coli O157:H7 and Uropathogenic E. coli in ground beef by high pressure processing and citral

Escherichia coli O157:H7 are a well-known intestinal foodborne pathogen which were responsible for numerous foodborne illness outbreaks. Uropathogenic E. coli (UPEC) are common contaminants in meat and poultry, and may cause urinary tract infections after colonizing the gastrointestinal tract followed by accidental transfer of contaminated feces from the anus to the urethra. High pressure processing (HPP) has been demonstrated an effective means in reducing pathogenic E. coli levels in meat and poultry. Citral, an antimicrobial, also demonstrated some inactivation effect on pathogenic E. coli in ground beef (ca. 0.5–1.0 log CFU/g reduction at 1% w/w without HPP). With HPP alone, to achieve 5 log CFU/g reduction required a 500 MPa level and 15 min (for both O157:H7 and UPEC). However, 1% of citral addition may lower the pressure requirement to 380 MPa and 15 min which could reduce the food quality damage. To effectively inactivate E. coli O157:H7 and UPEC in meat, high pressure processing (HPP) in combination with the antimicrobial citral was studied. Ground beef inoculated with E. coli O157:H7 or UPEC were treated at different HPP conditions (250–350 MPa; 10–20 min), and citral (0.75–1.25%, w/w) following a central composite experimental design. Quadratic linear regression equations were developed to describe and predict the reductions of E. coli O157:H7 (R² = 0.93, p < 0.001) and UPEC (R² = 0.92, p < 0.001). Dimensionless nonlinear models consisting of three impact factors were also developed and compared with the linear models. These models were experimentally validated. Citral enhanced the inactivation of pathogenic E. coli, increasing the effectiveness of the HPP process. The models may assist the food industry and regulatory agencies in risk assessment of E. coli O157:H7 and UPEC on ground meats.     

Microbial efficacy and impact on the population of Escherichia coli of a routine sanitation process for the fabrication facility of a beef packing plant

The aim of this study was to assess the microbiological effect of a sanitation process used at a beef fabrication facility. On each of three fabrication days and the following mornings, samples were collected from meat contacting surface (CS) and non-contacting surface of two conveyor belts and from surfaces of cuttings tables before cleaning and before work, respectively, for recovery of total aerobes, coliforms and Escherichia coli. Selected presumptive E. coli isolates from belt 2 were purified and the confirmed isolates were genotyped using multiple-locus variable-number tandem-repeat analysis (MLVA). The numbers of aerobes before cleaning were mostly 6 log cfu/1000 cm² and were not significantly (p > 0.05) different from those before work. The log total numbers of coliforms and E. coli before cleaning and before work were largely similar. However, the numbers of samples from which no coliforms or E. coli were recovered were fewer before cleaning than before work. Of the presumptive E. coli isolates from CS and NCS before cleaning and before work, 88 (95%) and 1 (5%), and 134 (84%) and 78 (65%), respectively, were confirmed. MLVA of 89 (CS) and 212 (NCS) E. coli isolates revealed 18 and 16 distinct genotypes, respectively. Of the E. coli from CS, 98% were found at one sampling time. Of the E. coli from NCS, however, >90% were found more than once, and both before cleaning and before work. The findings show that the sanitation process did not have significant impact on the numbers of aerobes or coliforms, but was effective for removing E. coli from CS and to a lesser degree from NCS of conveyor belt.     

Development of a controlling method for Escherichia coli O157:H7 and Salmonella spp. in fresh market beef by using polylysine and modified atmosphere packaging

Escherichia coli O157:H7 and Salmonella spp. often contaminate fresh beef. In Japan, an E coli outbreak caused by raw beef made 181 people ill and 5 individuals dead in 2011. Responding to this outbreak, an effective sterilization method for fresh beef is expected to be developed. In this study, ε-polylysine combined with CO₂-packaging method was examined for controlling these pathogens in fresh beef. At an incubation temperature of 4 °C, approximately 4.3 log and 2.4 log reduction in bacterial numbers were observed after 7-day incubation for E. coli O157:H7 and Salmonella, respectively, in ε-polylysine-added beef. When effectiveness of CO₂-packaging combined with ε-polylysine was investigated, CO₂ did not have additional inhibiting effect on bacterial growth compared to only-ε-polylysine-treated samples when incubated at 4 °C. However, effectiveness of CO₂ was observed when incubated at 10 °C where approximately 2.9 log and 4.4 log reduction in E. coli cell numbers were observed in only-ε-polylysine-treated samples and polylysine- and CO₂-treated group, respectively, and approximately 1.7 log and 3.5 log reduction in Salmonella cell numbers were observed in only-ε-polylysine-treated samples and polylysine and CO₂-treated group, respectively. This study confirmed that ε-polylysine or ε-polylysine combined with CO₂ packaging are effective in preventing foodborne diseases caused by raw beef.     

A risk-based approach for evaluation of hygiene performance at pig slaughter

In Denmark, the pig slaughterhouses have a daily input of pigs infected and/or contaminated with Salmonella, and the slaughter hygiene has major influence on the level of Salmonella contamination on the meat leaving the slaughterhouse. However, the relationship between the effect of improved hygiene performance and the consequential reduction of human health risk has not been estimated so far. In this study, swab samples from 2702 pig carcasses were collected, originally for other purposes, from five large Danish slaughterhouses in a period from 2005 to 2007, covering all seasons of the year. The samples were analysed quantitatively for E. coli and semi-quantitatively for Salmonella. A positive association between the number of E. coli on carcasses and the prevalence of Salmonella positive carcasses was shown. For carcasses positive for Salmonella, a positive association was also shown between the number of E. coli and the number of Salmonella on the carcass. As no biological association has been reported between faecal shedding of E. coli and presence of Salmonella, the relationship was considered to be associated with the level of faecal contamination. The positive association between E. coli and Salmonella was used as basis for developing a quantitative risk assessment model for Salmonella, using the level E. coli as model input. The model output associated the hygiene performance with a relative risk estimate of human salmonellosis. The overall objective was to develop a decision support tool that can be used to support risk-based hygiene interventions in pig slaughterhouses.     

Prevalence of virulence genes in Escherichia coli isolated from food in Casablanca (Morocco)

This study was undertaken to determine the frequency of potentially pathogenic Escherichia coli (E. coli) strains among E. coli isolated from Casablanca, Morocco. The E. coli strains were isolated from ground beef (n = 140), turkey (n = 200), sausage (n = 120), seafood (n = 60), domestic water (n = 35) and well water (n = 50). The prevalence of E. coli was 48%, 45%, 35.5%, 30%, 8.3%, 0%, for well water, ground beef, turkey, sausage, sea food and domestic water, respectively. Two hundreds E. coli isolates were tested for the presence of 17 virulence genes associated with strains causing intestinal and extra-intestinal infections. The virulence genes included stx1, stx2, lt, st, hlyA, aggA, saa, astA, iucD, cnf1, eaeA, bfpA, ial, ipaH, afa, pap and sfa. PCR showed that 37% (74) of E. coli isolates carried one or more of these virulence genes. No virulence genes were found in E. coli strains isolated from sea food samples. In contrast, 10% of the ground beef samples, 18% of the turkey samples, 17.5% of sausage samples and 6% of well water contained specific factors for intestinal E. coli pathogens.     

Decontamination of incoming beef trimmings with hot lactic acid solution to improve microbial safety of resulting dry fermented sausages – A pilot study

In the study, beef trimmings intended for sausage production were subjected to different decontamination treatments based on lactic acid-hot water combination, with aim to eliminate or reduce foodborne pathogens Escherichia coli O157, Salmonella Typhimurium and Listeria monocytogenes in resultant dry, fermented sausages. In finished sausages, produced from untreated trimmings, “natural” reductions of inoculated E. coli O157 and Salmonella Typhimurium were on average 1.9 logs, L. monocytogenes count remained unchanged, and no detectable concentrations of biogenic amines were found. The same type of sausages were also produced by using beef trimmings which was pathogen-inoculated and then decontaminated by: hot, 4% lactic acid in water solution (90 °C for 10 s; treatment HLA1); or hot, 4% lactic acid in water solution (85 °C for 20 s; treatment HLA2), or hot, 4% lactic acid in water solution (80 °C for 30 s; treatment HLA3). The use of HLA-decontaminated beef trimmings resulted in total E. coli O157 reductions of at least 3.9 logs and in total Salmonella Typhimurium reductions of at least 3.6 logs, whilst biogenic amines were not detected in finished sausages. The overall sensorial acceptability of finished sausages produced with HLA-decontaminated beef trimmings was somewhat diminished. Further work is required to optimise the HLA-based incoming beef treatments.     

Effect of hydrogen peroxide vapor treatment for inactivating Salmonella Typhimurium,Escherichia coli O157:H7 and Listeria monocytogenes on organic fresh lettuce

In this study, the efficacy of hydrogen peroxide vapor (HPV) for reducing Salmonella Typhimurium, Escherichia coli O157:H7 and Listeria monocytogenes on lettuce was investigated as well as its effect on lettuce quality. Lettuce was inoculated with a cocktail containing three strains of each pathogen then treated with vaporized hydrogen peroxide for 0, 2, 4, 6, 8 and 10 min. The concentrations of hydrogen peroxide used were 0, 1, 3, 5 and 10%. With increasing treatment time and hydrogen peroxide concentration, HPV treatment showed significant (P < 0.05) reduction compared to the control (0%, treated with vaporized distilled water). In particular, vaporized 10% hydrogen peroxide treatment for 10 min was the most effective combination for reducing the three pathogens on lettuce. The reduction levels of S. Typhimurium, E. coli O157:H7 and L. monocytogenes on lettuce were 3.12, 3.15 and 2.95 log₁₀ CFU/g, respectively. Furthermore, there were no significant (P > 0.05) quality changes (color and texture) of lettuce among all tested samples, and hydrogen peroxide residues were not detected after 36 h storage time in any of the treated samples. These results suggest that HPV treatment could be an alternative method for reducing S. Typhimurium, E. coli O157:H7 and L. monocytogenes on fresh produce.     

Effects of spray volume, type of surface tissue and inoculum level on the survival of Escherichia coli on beef sprayed with 5% lactic acid

Membrane, fat and cut muscle surfaces of beef were inoculated with Escherichia coli at numbers about 4, 1 or −1 log cfu/cm². The inoculated meat was sprayed with water or 5% lactic acid at volumes of 0.5, 0.1 or 0.02 ml/cm². Spraying with water reduced the numbers of E. coli on membrane surfaces by up to 1 log unit, but had little effect on the numbers of E. coli on fat or cut muscle surfaces. Spraying with 5% lactic acid reduced the highest numbers of E. coli on membrane surfaces by up to 4 log units; but those numbers on fat or cut muscle surfaces were reduced by ≤1.5 log unit, and the reductions declined with decreasing volumes of 5% lactic acid. With inocula of 1 log cfu/cm², spraying lactic acid in any volume reduced the numbers of E. coli on membrane or fat surfaces by about 1 log unit, and the numbers on cut muscle surfaces by between 0.8 and 0.2 log unit. E. coli were detected in enrichment cultures of samples from all surfaces inoculated with E. coli at −1 log cfu/cm² and sprayed with 5% lactic acid at 0.5 ml/cm². The findings indicate that spraying relatively heavily contaminated cuts or trimmings with 5% lactic acid at ≥0.1 ml/cm² can be expected to reduce numbers of E. coli and, presumably, associated pathogens by between 0.5 and 1 log unit. However, such a treatment is likely to be at best marginally effective for reduce the numbers of these organisms on lightly contaminated product.     

Effects of mild and pasteurizing heat treatments on survival of generic and verotoxigenic Escherichia coli from beef enrichment cultures

At many North American beef packing plants, hot water washes and pasteurizing treatments are used to clean and decontaminate carcasses. The aim of this study was to determine whether reduction in numbers of total Escherichia coli found on beef could be regarded as indicative of the reduction in numbers of verotoxigenic E. coli (VTEC) resulting from the same heat treatment. Swab samples were collected from hide-on beef carcasses and were enriched for E. coli in E. coli broth supplemented with novobiocin. Suspensions containing cells in the stationary phase were mixed with equal volumes of meat juice medium and the mixtures were not heated or were heated at temperatures between 55 and 70 °C. All preparations were treated with deoxycholate and propidium monoazide (PMA), then DNA was extracted. Real-time PCR was performed using primers targeting the uidA gene for total E. coli, the stx₁ and stx₂ genes for VTEC, and the eae gene for O157. For samples that were not subjected to heat treatment, cycle threshold (Ct) values were from 13.53 to 17.93 for uidA, 17.94 to 26.77 for stx₁, 21.57 to 29.36 for stx₂, and 23.53 to 28.31 for eae. Ct values for all genes were higher for heat treated than for not treated portions of samples. Differences between Ct values for not treated and heat treated portions of each sample were 5.06–7.57 for uidA, 4.35 to 7.03 for stx₁, 4.49 to 7.12 for stx₂ and 4.75 to 6.77 for eae. Differences between the increases of Ct values for pairs of genes in the sample were 0.32–0.83 for uidA and stx₁, 0.19–0.57 for uidA and stx₂ and 0.31–0.80 for uidA and eae. The maximum change in the ratio of Ct values for uidA and stx₁, stx₂ or eae as a result of heating corresponded to a change of 0.3 log units, which is less than the 0.5 log units generally considered to be microbiologically significant. Therefore, the findings indicate that reductions as a result of mild or pasteurizing heat treatments of total E. coli populations derived from beef can be regarded as indicative of the reductions in sub-populations of O157-VTEC and total VTEC resulting from the treatments.     

Microbial load reduction of sweet basil using acidic electrolyzed water and lactic acid in combination with mild heat

Sweet basil has been used worldwide as an ingredient for several cuisines. However, it can be contaminated with pathogens; especially Escherichia coli and Salmonella spp. are mainly introduced by poor hygiene during harvesting, cleaning, packaging and distribution. This study aimed to study the efficacy of lactic acid (LA) and acidic electrolyzed water (AEW) against mesophilic bacteria on sweet basil. In addition, a combination treatment was also investigated, using mild heat with the selected sanitizer to disinfect sweet basil inoculated with S. Typhimurium and E. coli. The 2% LA treatment showed high efficiency in microbial decontamination, and mesophilic bacteria were reduced by about 3 log CFU/g. Additionally, the decontamination efficacy of LA increased when combined with mild heat. The use of 2% LA at 50 °C showed the highest microbial reduction in sweet basil, in which mesophilic bacteria, S. Typhimurium, and E. coli were reduced by 4.62, 3.80 and 3.61 log CFU/g, respectively. These findings indicate that LA can be more effective than AEW in disinfection and provides greater efficiency when combined with mild 50 °C heat.     

General patterns of background microbiota and selected bacterial pathogens during production of fermented sausages in Serbia

The presence of Salmonella spp. or Escherichia coli O157 and background microbiota, pH and a_w were determined in raw fermented sausages produced from pork or beef and without lactic acid bacteria starters. The investigation was conducted at five meat processing plants, and the sampling was done at five steps of the production process at each plant. In meat trimmings, total viable count (TVC) ranged around 6 log CFU/g and around 5–6 log CFU/g in the pork and the beef sausages, respectively. Enterobacteriaceae count (EBC) ranged in the vicinity of 3–4 log CFU/g, whilst E. coli count (ECC) ranges were comparably lower (by 1–2 logs). During chopping of both the pork and the beef trimmings, the levels of TVC, EBC and ECC increased by 1–1.5 logs. After the additives and the spices were added, background microbiota tended to slightly decrease, generally more noticeably in pork sausages and with ECC. During the fermentation-drying stage, in both pork and beef sausages, initial TVC levels (6–7 log CFU/g) increased by the mid-process (by approximately 1.5–2 logs) and remained at those levels in finished products. During the same period, lactic acid bacteria (LAB) increased from initial levels of 5.5–6 log CFU/g to around 7–8 log CFU/g in pork and around 8–9 log CFU/g in beef sausages, and became the predominant microbial group. Salmonella spp. was found in the first three stages of the production process (trimmings, trimmings chopping, mixing with additives/spices), in two of three meat processing plants, but not at later stages of the production process. E. coli O157 was found only in one sample of chopped trimmings in one meat processing plant. The background microbiota patterns and levels were, generally, similar to those commonly reported for raw fermented sausages in other published studies. The initial presence of foodborne pathogens in raw fermented sausage production may be considered as a potential meat safety risk, because in the case of high initial pathogen counts, their total elimination cannot be assumed.     

Development of a real-time PCR procedure for quantification of viable Escherichia coli in populations of E. coli exposed to lactic acid,and the acid tolerance of verotoxigenic E. coli (VTEC) from cattle hides

The aims of this study were to develop a real-time PCR procedure for determining the effects on Escherichia coli of treatment for decontaminating beef carcasses with lactic acid solution, and determining if there were differences in the acid tolerance of E. coli generally and verotoxigenic E. coli (VTEC). Suspensions of E. coli were incubated with 4% lactic acid at pH 3.6. The numbers of surviving E. coli at different incubation times were determined from plate counts and from quantification by real-time PCR of the uidA gene in DNA preparations. The numbers of viable E. coli progressively declined, by about 4 log units during incubation for 6 h. The mean cycle threshold (Ct) values for uidA in DNA from samples collected at different times and treated or not treated with propidium monoazide (PMA) before DNA extraction were similar. Treatment with 1% sodium deoxycholate (SD) before PMA treatment resulted in an increase of >6 Ct when the reduction in viable cell number was around 1 log. When E. coli incubated with 4% lactic acid solutions of pH 2.4, 2.8, 3.2 or 3.6 were resuscitated in half strength brain heart infusion (BHI) for 2 h before treatments with SD and PMA, the slope of the plot relating Ct values to the numbers of viable E. coli was 1.85 Ct log cfu⁻¹ with the correlation coefficient (R²) being 0.80. The findings indicate that while the membranes of E. coli inactivated by 4% lactic acid were largely impermeable to PMA, the membranes of both dead and injured cells were rendered permeable to PMA by treatment with 1% SD. Resuscitation in BHI restored the membrane barrier properties of the injured cells. Treatment with lactic acid resulted in increases in Ct values of 4.1, 3.7, 2.5 and 1.5 for the uidA, stx₁, stx₂ and eae genes, respectively; and the increases in Ct values for the latter two genes were significantly different (p < 0.05) from that for the uidA gene. This indicates that VTEC carrying stx₂ and/or eae were more acid resistant than other E. coli. Thus, caution should be exercised when using generic E. coli as an indicator for VTEC for assessment of the antimicrobial efficacy of organic acid decontaminating treatments at abattoirs.