Transfer of Salmonella and Campylobacter from stainless steel to romaine lettuce

The degree of transfer of Campylobacter jejuni and Salmonella enterica serovar Typhimurium was evaluated from a stainless steel contact surface to a ready-to-eat food (lettuce). Stainless steel coupons (25 cm2) were inoculated with a 20-microl drop of either C. jejuni or Salmonella Typhimurium to provide an inoculum level of approximately 10(6) CFU/28 mm2. Wet and dry lettuce (Lactuca sativa var. longifolia) pieces (9 cm2) were placed onto the inoculated stainless steel surface for 10 s after the designated inoculum drying time (0 to 80 min for C. jejuni; 0 to 120 min for Salmonella Typhimurium), which was followed by the recovery and enumeration of transferred pathogens (lettuce) and residual surface pathogens (stainless steel coupons). For transfers of Salmonella Typhimurium to dry lettuce, there was an increase from 36 to 66% in the percent transfer of the initial inoculum load during the first 60 min of sampling and then a precipitous drop from 66 to 6% in percent transfer. The transfer of Salmonella Typhimurium to wet lettuce ranged from 23 to 31%, with no statistically significant difference between recoveries over the entire 120-min sampling period. For C. jejuni, the mean percent transfer ranged from 16 to 38% for dry lettuce and from 15 to 27% for wet lettuce during the 80-min sampling period. The results of this study indicate that relatively high numbers of bacteria may be transferred to a food even 1 to 2 h after surface contamination. These findings can be used to support future projects aimed at estimating the degree of risk associated with poor handling practices of ready-to-eat foods.     

Effectiveness of sanitation with quaternary ammonium compound or chlorine on stainless steel and other domestic food-preparation surfaces.

The relative ability of various materials used for domestic and/or food-service sinks and countertops to be sanitized was determined. Both smooth (unused) and abraded surfaces were tested by exposure to 200 mg of quaternary ammonium compound per liter or 200 mg of sodium hypochlorite per liter. Surface materials tested included mechanically polished (type 304, #4 finish) and electropolished stainless steel, polycarbonate, and mineral resin. Surfaces were prepared for testing by allowing attachment of a Staphylococcus aureus culture for 4 h to achieve an initial attached population of 10(4) to 10(5) CFU/cm2. The test procedure involved immersion of the surface in sanitizer solution followed by wiping with a sanitizer-saturated cloth. Residual staphylococci were detected by overlaying agar directly on the treated surface. Results indicated that the stainless steels and the smooth polycarbonate, which had 0.5 log CFU/cm2 or fewer of residual staphylococci, were more readily sanitized by quaternary ammonium compound than were either the mineral resin surfaces, which had nearly 2.0 log CFU/cm2 of residual staphylococci, or the abraded polycarbonate which had nearly 1.0 log CFU/cm2 of residual staphylococci. Chlorine was most effective on the mechanically polished stainless steel, the unabraded electropolished stainless steel, and the polycarbonate surfaces, reducing cell populations to less than 1.0 log CFU/cm2. Chlorine was less effective on abraded electropolished stainless steel and mineral resin surfaces, where populations remained greater than 1.0 log CFU/cm2. Sanitation with quaternary ammonium compound or chlorine reduced S. aureus populations more than 1,000-fold on all surfaces except unabraded mineral resin.     

Effects of inoculation level, material hydration, and stainless steel surface roughness on the transfer of listeria monocytogenes from inoculated bologna to stainless steel and high-density polyethylene

The influence of inoculation level, material hydration, and stainless steel surface roughness on the transfer of Listeria monocytogenes from inoculated bologna to processing surfaces (stainless steel and polyethylene) was assessed. Slices of bologna (14 g) were inoculated with Listeria at different levels, from 10(5) to 10(9) CFU/cm2. Transfer experiments were done at a constant contact time (30 s) and pressure (45 kPa) with a universal testing machine. After transfer, cells that had been transferred to sterile stainless steel and polyethylene were removed and counted, and the efficiency of transfer (EOT) was calculated. As the inoculation level increased from 10(5) to 10(9) CFU/cm(2), the absolute level of transfer increased in a similar fashion. By calculating EOTs, the data were normalized, and the initial inoculation level had no effect on the transfer (P > 0.05). The influence of hydration level on stainless steel, high-density polyethylene, and material type was investigated, and the EOTs ranged from 0.1 to 1 under all the conditions tested. Our results show that transfers to wetted processing surfaces (mean EOT = 0.43) were no different from dried processing surfaces (mean EOT = 0.35) (P > 0.05). Material type was shown to be a significant factor, with greater numbers of Listeria transferring from bologna to stainless steel (mean EOT = 0.49) than from bologna to polyethylene (mean EOT = 0.28) (P < 0.01). Stainless steel with three different surface roughness (Ra) values of <0.8 microm (target Ra = 0.25, 0.50, and 0.75 Vmicrom) and two different finishes (mechanically polished versus mechanically polished and further electropolished) was used to evaluate its effect on the transfer. The surface roughness and finish on the stainless steel did not have any effect on the transfer of Listeria (P > 0.05). Our results showed that when evaluating the transfer of Listeria, the use of EOTs rather than the absolute transfer values is essential to allow comparisons of transfer conditions or comparisons between research groups.     

Behavior of Listeria monocytogenes in a Pseudomonas putida biofilm on a condensate-forming surface

Listeria monocytogenes has been isolated from condensate-forming surfaces in food processing plants. The objective of this research was to observe the behavior of L. monocytogenes on condensate-covered stainless steel with a Pseudomonas putida biofilm. L. monocytogenes-containing biofilms, either with or without added chicken protein, were incubated in a high humidity chamber at 12 degrees C to allow formation of condensate. Samples were analyzed for attached and unattached L. monocytogenes and total plate count periodically for 35 days. Samples were also taken for microscopic observation of Listeria and bacterial extracellular polymeric substances (EPS). L. monocytogenes attached in significantly greater numbers (> 3-log difference) to surfaces with preexisting P. putida biofilms than to Pseudomonas-free surfaces. L. monocytogenes survived in the presence or absence of P. putida with no added nutrients for 35 days, with numbers of survivors in the range of 3 to 4 log CFU/cm2 in the presence of P. putida and less than 2.9 log CFU/cm2 in pure culture. Attached and unattached L. monocytogenes were at similar levels throughout the incubation under all conditions studied. The addition of protein to the biofilms allowed growth of L. monocytogenes in pure culture during the first 7 days of incubation. Numbers of L. monocytogenes were not affected by the presence of P. putida when protein was present. Unattached L. monocytogenes were at levels of 3.6 to 6.7 log CFU/cm2 on the protein-containing surfaces. Microscopic observation of the condensate-covered biofilms indicated that L. monocytogenes formed microcolonies embedded within an EPS matrix over a 28-day period. This research demonstrates that L. monocytogenes can survive on condensate-forming stainless steel in low and high nutrient conditions, with or without the presence of Pseudomonas biofilm. The Listeria can detach and, therefore, have the potential to contaminate product.     

Persistence of caliciviruses on environmental surfaces and their transfer to food

The noroviruses (NoV) are a common cause of human gastroenteritis whose transmission by foodborne routes is well documented. Fecally contaminated surfaces are likely to contribute to this foodborne transmission and to the propagation of viral disease outbreaks. The purpose of this study was to (i) investigate the stability of NoV on various food preparation surfaces; and (ii) evaluate the degree of virus transfer from these surfaces to a model-ready-to-eat (RTE) food. For the virus persistence experiments, stainless steel, formica and ceramic coupons were artificially contaminated with Norwalk virus (NV), the prototype genogroup I NoV; NV RNA; or feline calicivirus (FCV) F9 (a NoV surrogate), stored at ambient temperature for up to 7 d, and periodically assayed for detection. In the transfer experiments, stainless steel coupons were inoculated with NV or FCV F9 and allowed to dry for 10, 30 and 60 min, after which lettuce leaves were exposed to the surface of the coupons at various contact pressures (10, 100, and 1000 g/9 cm2). Virus recovery was evaluated by RT-PCR (for NV and NV RNA) or by plaque assay (for FCV F9) using Crandell Reese Feline Kidney (CRFK) cells. NV and FCV were detected on all three surfaces for up to 7 d post-inoculation; for FCV, there was an approximate 6 to 7-log10 drop in virus titer over the 7 d evaluation period. By contrast, when stainless steel was inoculated with purified NV RNA, RT-PCR detection was not possible beyond 24 h. Transfer of both NV and FCV from stainless steel surfaces to lettuce occurred with relative ease. This study confirms lengthy NoV persistence on common food preparation surfaces and their ease of transfer, confirming a potential role for environmental contamination in the propagation of viral gastroenteritis.     

Salmonella enterica Enteritidis biofilm formation and viability on regular and triclosan-impregnated bench cover materials

Contamination of food contact surfaces by microbes such as Salmonella is directly associated with substantial industry costs and severe foodborne disease outbreaks. Several approaches have been developed to control microbial attachment; one approach is the development of food contact materials incorporating antimicrobial compounds. In the present study, Salmonella enterica Enteritidis adhesion and biofilm formation on regular and triclosan-impregnated kitchen bench stones (silestones) were assessed, as was cellular viability within biofilms. Enumeration of adhered cells on granite, marble, stainless steel, and silestones revealed that all materials were prone to bacterial colonization (4 to 5 log CFU/cm(2)), and no significant effect of triclosan was found. Conversely, results concerning biofilm formation highlighted a possible bacteriostatic activity of triclosan; smaller amounts of Salmonella Enteritidis biofilms were formed on impregnated silestones, and significantly lower numbers of viable cells (1 × 10(5) to 1 × 10(6) CFU/cm(2)) were found in these biofilms than in those on the other materials (1 × 10(7) CFU/cm(2)). All surfaces tested failed to promote food safety, and careful utilization with appropriate sanitation of these surfaces is critical in food processing environments. Nevertheless, because of its bacteriostatic activity, triclosan incorporated into silestones confers some advantage for controlling microbial contamination.     

Effectiveness of electrolyzed water as a sanitizer for treating different surfaces

The effectiveness of electrolyzed (EO) water at killing Enterobacter aerogenes and Staphylococcus aureus in pure culture was evaluated. One milliliter (approximately 10(9) CFU/ml) of each bacterium was subjected to 9 ml of EO water or control water (EO water containing 10% neutralizing buffer) at room temperature for 30 s. Inactivation (reduction of > 9 log10 CFU/ ml) of both pathogens occurred within 30 s after exposure to EO water containing approximately 25 or 50 mg of residual chlorine per liter. The effectiveness of EO water in reducing E. aerogenes and S. aureus on different surfaces (glass, stainless steel, glazed ceramic tile, unglazed ceramic tile, and vitreous china) was also evaluated. After immersion of the tested surfaces in EO water for 5 min without agitation, populations of E. aerogenes and S. aureus were reduced by 2.2 to 2.4 log10 CFU/ cm2 and by 1.7 to 1.9 log10 CFU/cm2, respectively, whereas washing with control water resulted in a reduction of only 0.1 to 0.3 log10 CFU/cm2. The washing of tested surfaces in EO water with agitation (50 rpm) reduced populations of viable cells on the tested surfaces to < 1 CFU/cm2. For the control water treatment with agitation, the surviving numbers of both strains on the tested surfaces were approximately 3 log10 CFU/cm2. No viable cells of either strain were observed in the EO water after treatment, regardless of agitation. However, large populations of both pathogens were recovered from control wash solution after treatment.     

Tolerance of Salmonella Enteritidis and Staphylococcus aureus to surface cleaning and household bleach

Effective cleaning and sanitizing of food preparation sites is important because pathogens are readily spread to food contact surfaces after preparation of contaminated raw products. Tolerance of Salmonella Enteritidis and Staphylococcus aureus to surface cleaning by wiping with regular, microfiber, and antibacterial-treated cloths was investigated. Wiping with cleaning cloths resulted in a considerable reduction of microorganisms from surfaces, despite the greater difficulty in removing S. aureus than Salmonella Enteritidis. Depending on the cloth type, S. aureus were reduced on surfaces from initial numbers of approximately 10(5) CFU/100 cm2 to numbers from less than 4 CFU/100 cm2 (below the detection limit) to 100 CFU/100 cm2. Directly after the cloths were used to clean the contaminated surfaces, they contained high numbers of bacteria (10(4) to 10(5) CFU/100 cm2), except for the disposable antibacterial-treated cloths, in which no bacteria could be detected. The tolerance of these pathogens to sodium hypochlorite was studied in the suspension test and in cloths. S. aureus showed a better tolerance for sodium hypochlorite than Salmonella Enteritidis. Inactivation of microorganisms in cloths required a higher concentration of sodium hypochlorite than was needed in the suspension test. Repeated exposure to sodium hypochlorite, however, resulted in an increase in susceptibility to this compound. This study provides essential information about the transfer of bacteria when wiping surfaces and highlights the need for a hygiene procedure with cleaning cloths that sufficiently avoids cross-contamination in the household environment.     

Impact of cleaning and disinfection on the non-culturable and culturable bacterial loads of food-contact surfaces at a beef processing plant

We assessed the impact of industrial cleaning and disinfection (C&D) on colony-forming units (CFUs), viable (culturable and viable but non-culturable) cells and on total cells (viable and dead cells). Bacterial loads on polyvinyl chloride (PVC) and stainless steel surfaces in a cutting room at a beef processing plant were determined before and after C&D by real-time PCR to quantify cells from successive swabs from surfaces with or without an ethidium monoazide pre-treatment and by CFU counts on tryptone soy agar. Agar contact plates were also applied after C&D for comparison. Before C&D, total cells reached 5.4 and 4.7logcells/cm(2), viable cells 4.0 and 4.4logcells/cm(2) and CFUs 3.1 and 2.9logCFU/cm(2) on PVC and stainless steel surfaces, respectively. Although C&D left surfaces visually clean, it did not lead to a significant reduction in total cells. Significant reductions were only observed on PVC for CFUs: 0.8 log and on stainless steel surfaces for viable cells and CFUs: 0.8 and 1.5 log, respectively. Our results show that CFUs were both more easily detached and killed on stainless steel surfaces than on PVC surfaces. Other important results include the following observations: 1) a single swabbing detached only between 2 and 27% of the actual bacterial load; 2) after C&D, the difference between the actual culturable population and the one assessed by one agar contact plate was 1.9 and 2.7logCFU/cm(2) on PVC and stainless steel surfaces, respectively.     

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.     

保加利亚乳杆菌和嗜热链球菌生物膜形成研究

采用置片法和菌落计数法对嗜热链球菌(Streptococcus thermophilus)和保加利亚乳杆菌(Lactobacillus bulgaricus)在不同载体表面(椰果粒、不锈钢网布、塑料片、陶瓷片和玻璃片)上形成生物膜的能力进行研究。结果表明：椰果粒和不锈钢网布是适宜乳酸菌单菌生物膜形成的载体,培养7d椰果粒和不锈钢网布上的单菌生物膜初始菌密度可达107CFU/cm2,并且在后续培养中能稳定在3.2×106CFU/cm2左右;混菌生物膜菌密度连续7d稳定在1×107CFU/cm2左右。利用扫描电镜对S. thermophilus和L. bulgaricus形成的混菌生物膜进行观察,结果表明在椰果粒和不锈钢网布表面上S. thermophilus和L. bulgaricus形成典型的混菌生物膜结构。     

Efficiency of sanitizing agents for destroying Listeria monocytogenes on contaminated surfaces

In an effort to control the potential hazard of dairy product contamination by contact with processing surfaces, the efficiency of four commercial sanitizing agents was evaluated using the AOAC use-dilution method for their bactericidal activity at 4 and 20 degrees C against Listeria monocytogenes strain Scott-A attached on four types of surfaces (stainless steel, glass, polypropylene, and rubber). Our results indicate that all sanitizers tested were more efficient against L. monocytogenes attached to nonporous surfaces than to porous surfaces. After 10 min of contact time, the limit concentration of disinfectants was at least 5 to 10 times higher for sanitizing rubber than stainless steel or glass surfaces. Concentrations of each sanitizer needed to be higher at sanitation at 4 degrees C than at 20 degrees C to destroy L. monocytogenes attached to stainless steel, glass and rubber when surface contamination was achieved at 4 or 20 degrees C.     

Transfer of Listeria monocytogenes between abiotic surfaces under different weights

Cross contamination of Listeria monocytogenes from two different surfaces (plastic wrappers and stainless steel coupons) was simulated using a series of different weights. Enumeration of transfer was based on surface bacterial counts of biofilm stained surfaces. Direct contact between 2 surfaces has a constant rate of transfer that is independent of the pressure applied. This is the first report on the study of cross contamination between surfaces using pressure to illustrate transfer of bacteria in a food processing line.     

Prevalence and Concentration of Arcobacter spp. on Australian Beef Carcasses

The International Commission on Microbiological Specifications for Foods (ICMSF) classified Arcobacter spp. as emerging pathogens in 2002. Arcobacter spp. have been isolated from numerous food products at retail and from animal carcasses and feces at slaughter. A survey was conducted to determine both the prevalence and concentration of Arcobacter spp. on prechill beef carcasses. Surface swab samples were collected from 130 beef carcasses at the end of processing, prior to chilling. The concentration of Arcobacter spp. was determined by a most-probable-number per square centimeter (3 by 3) method with a limit of detection of 0.12 CFU/cm(2). Of the 100 carcasses examined from export abattoirs, 20 (20.0%) were contaminated with Arcobacter spp., and 5 of these had quantifiable levels of contamination ranging from 0.12 to 0.31 CFU/cm(2). Of the 30 carcasses examined at a pet food abattoir, 25 (83.3%) were contaminated with Arcobacter spp., and 10 of these had quantifiable levels of contamination ranging from 0.12 to 0.95 CFU/cm(2). Three species of Arcobacter, A. butzleri, A. cryaerophilus, and A. skirowii, were identified by PCR. Each of the species was present in an approximately equal ratio from export abattoirs. This study demonstrates that slaughter practices at export abattoirs are sufficient to maintain both low prevalence and low levels of contamination of beef carcasses with Arcobacter spp.     

Recovery of Escherichia coli Biotype I and Enterococcus spp. during refrigerated storage of beef carcasses inoculated with a fecal slurry.

Three beef front quarters/carcasses were inoculated with a slurry of cattle manure. During storage at 4 degrees C, two sponge samples from each of three sites (i.e., 100 cm2 from each of two fat surfaces and 100 cm2 from a lean surface) were taken from each of the three carcasses on days 0, 1, 3, 7, and 10 after inoculation. The initial numbers of Escherichia coli averaged 2.0 log10 CFU/cm2 (1.21 to 2.47 log10 CFU/cm2) using the Petrifilm method and 2.09 log10 most probable number (MPN)/cm2 (0.88 to 2.96 log10 MPN/cm2) using the MPN method. The initial numbers of enterococci averaged 3.34 log10 CFU/cm2 (3.07 to 3.79 log10 CFU/cm2) using kanamycin esculin azide agar. In general, an appreciable reduction in the numbers of E. coli occurred during the first 24 h of storage; for the Petrifilm method an average reduction of 1.37 log10 CFU/cm2 (0.69 to 1.71 log10 CFU/cm2) was observed, and for the MPN method an average reduction of 1.52 log10 MPN/cm2 (0.47 to 2.08 log10 MPN/cm2) was observed. E. coli were not detected (<-0.12 log10 CFU/cm2) using Petrifilm on day 7 of the storage period on two (initial counts of 1.21 and 2.29 log10 CFU/cm2) of the three carcasses. However, viable E. coli cells were recovered from these two carcasses after a 24-h enrichment at 37 degrees C in EC broth. Viable E. coli cells were detected at levels of -0.10 log10 CFU/cm2 on the third carcass (initial count of 2.47 log10 CFU/cm2) after 7 days at 4 degrees C. No significant difference in recovery of viable cells was observed between the MPN and Petrifilm methods on days 0, 1, and 3 (P > 0.05). However, viable E. coli cells were recovered from all three carcasses by the MPN method on day 7 at an average of -0.29 log10 MPN/ cm2 (-0.6 to -0.1 log10 MPN/cm2). On day 10, viable cells were recovered by the MPN method from two of the three carcasses at -0.63 and -0.48 log10 MPN/cm2 but were not recovered from the remaining carcass (<-0.8 log10 MPN/cm2). Similar to E. coli, the greatest reduction (average of 1.26 log10 CFU/cm2, range = 1.06 to 1.45 log10 CFU/cm2) in the numbers of enterococci occurred during the first 24 h of storage. Because of higher initial numbers and a slightly slower rate of decrease, the numbers of Enterococcus spp. were significantly higher (P < 0.017) than the numbers of E. coli Biotype I after 3, 7, and 10 days of storage. These results suggest that enterococci may be useful as an indicator of fecal contamination of beef carcasses.     

Transfer of Salmonella Enteritidis to four types of surfaces after cleaning procedures and cross-contamination to tomatoes

The objectives of the present study were to evaluate the spread of Salmonella Enteritidis to different cutting boards (wood, triclosan-treated plastic, glass, and stainless steel) from contaminated poultry skin (5 log CFU/g) and then to tomatoes and to analyze the effect of different protocols used to clean these surfaces to control contamination. The following procedures were simulated: (1) no cleaning after handling contaminated poultry skin; (2) rinsing in running water; (3) cleaning with dish soap and mechanical scrubbing; and (4) cleaning with dish soap and mechanical scrubbing, followed by disinfection with hypochlorite. The pathogen was recovered from all surfaces following procedure 1, with counts ranging from 1.90 to 2.80 log, as well as from the tomatoes handled on it. Reduced numbers of S. Enteritidis were recovered using the other procedures, both from the surfaces and from the tomatoes. Counts were undetectable after procedure 4. From all surfaces evaluated, wood was the most difficult to clean, and stainless steel was the easiest. The use of hypochlorite as a disinfecting agent helped to reduce cross-contamination.     

Quantification of Campylobacter on the surface and in the muscle of chicken legs at retail

The objective of this study was to determine the prevalence and numbers of Campylobacter on the skin and in the muscle of chicken legs at retail to examine the external and internal contamination for an exposure assessment. Furthermore, the study assessed seasonal influence on Campylobacter contamination in chicken legs. Of the 140 examined skin samples, 66% were positive, and the internal contamination of 115 sampled chicken legs was 27%. The enumeration of Campylobacter on the surface of positive chicken legs revealed a median of 2.4 log CFU/g of skin, and the quantification of Campylobacter in the muscle gave results mainly under the detection limit of the most-probable-number method (<0.3 MPN Campylobacter per g). The external contamination was significantly higher than the internal. In both skin and muscle samples, Campylobacter jejuni had a much higher incidence than Campylobacter coli. However, with regard to the specification of Campylobacter on the surface of chicken legs, C. coli was isolated at higher colony counts than C. jejuni. During the 1-year study, two peaks of Campylobacter contamination occurred, one in the early springtime (February and March, 100 and 90%, respectively) and the second during the warmer months in the summer (July and August, both 90%). Furthermore, a positive correlation between prevalence and numbers of Campylobacter on chicken legs was observed.     

Incidence of Salmonella, Campylobacter jejuni, Campylobacter coli, and Listeria monocytogenes in poultry carcasses and different types of poultry products for sale on the Belgian retail market.

From January 1997 to May 1998, 772 samples of poultry carcasses and poultry products for sale on the retail market in Belgium were analyzed for the presence of Salmonella spp., Salmonella Enteritidis, Campylobacter jejuni, C. coli, and Listeria monocytogenes per 100 cm2 or 25 g. Poultry samples were contaminated with Salmonella (36.5%), C. jejuni and C. coli (28.5%), and L. monocytogenes (38.2%). In about 12.3% of the poultry samples, the L. monocytogenes contamination level exceeded 1 CFU per g or cm2. Significant differences in pathogen contamination rates of poultry products were noticed between the poultry products originating from Belgian, French, and U.K. abattoirs. Poultry products derived from broiler chickens running free in pine woods until slaughtering age (12 to 13 weeks) had a significantly (P < 0.05) lower contamination rate of Salmonella than poultry products from enclosed broilers slaughtered at the age of 6 to 8 weeks. A significantly (P < 0.05) lower pathogen contamination rate was noted for Salmonella, C. jejuni, and C. coli for poultry cuts without skin compared to poultry cuts with skin on. An increase in pathogen contamination rate was noticed during cutting and further processing. To diminish C. jejuni, C. coli, Salmonella, and L. monocytogenes contamination rates, hygienic rules of slaughter and meat processing must be rigorously observed. At the moment, zero tolerance for these pathogens is not feasible, and there is a need to establish criteria allowing these pathogens to be present at reasonable levels in the examined poultry samples.     

Recovery and transfer of Salmonella typhimurium from four different domestic food contact surfaces

Domestic food contact surfaces can play an important role in the transmission of foodborne disease, yet debate continues as to which surface materials pose the greatest risk to consumer health in terms of cross-contamination during food preparation. Salmonella Typhimurium was inoculated onto stainless steel, Formica, polypropylene, or wooden surfaces (25 cm2) in the presence or absence of protein (tryptic soy broth supplemented with 5% horse serum) and held at room temperature. The pathogen was recovered from the test surfaces immediately after inoculation (T=0) and every hour for up to 6 h, by a conventional microbiological sampling technique and by direct transfer onto a model ready-to-eat food (cucumber slices). On all surfaces, pathogen numbers declined during the 6-h holding period, with the most rapid reductions occurring within the first hour. The presence of protein significantly increased (P < 0.05) the number of bacteria recovered from all surface types. However, regardless of application medium or holding time, the number of bacteria recovered from Formica (in all cases) and stainless steel (in most cases) was significantly higher than were the numbers on polypropylene or wood. Similarly, regardless of application medium or holding time, significantly higher bacterial numbers were transferred to the model food from Formica or stainless steel than from polypropylene or wooden surfaces. These differences were greater when the bacteria were applied in a protein-rich medium and the test surfaces held for 1 h or more. The results of this study emphasize that differences, both in recoverability and in the number of bacteria transferred to the model food rather than simply reflecting differences in pathogen survival, may also reflect differences in the ability of the test bacteria to remobilize from the different surface types. However, the results also demonstrate a fundamental problem when choosing food contact surfaces, i.e., that those characteristics that make a surface "easy to clean" may also render it more likely to release contaminating pathogens during common food preparation practices.