Models of the behavior of Escherichia coli O157:H7 in raw sterile ground beef stored at 5 to 46 degrees C

Escherichia coli O157:H7 can contaminate raw ground beef and cause serious human foodborne illness. Previous reports describe the behavior of E. coli O157:H7 in ground beef under different storage conditions; however, models are lacking for the pathogen's behavior in raw ground beef stored over a broad range of temperature. Using sterile irradiated raw ground beef, the behavioral kinetics of 10 individual E. coli O157:H7 strains and/or a 5- or 10-strain cocktail were measured at storage temperatures from 5° to 46 °C. Growth occurred from 6 to 45 °C. Although lag phase duration (LPD) decreased from 10.5 to 45 °C, no lag phase was observed at 6, 8, or 10 °C. The specific growth rate (SGR) increased from 6 to 42 °C then declined up to 45 °C. In contrast to these profiles, the maximum population density (MPD) declined with increasing temperature, from approximately 9.7 to 8.2 log cfu/g. Bias (B_f) and accuracy (A_f) factors for an E. coli O157:H7 broth-based aerobic growth model (10 to 42 °C) applied to the observations in ground beef were 1.05, 2.70, 1.00 and 1.29, 2.87, 1.03, for SGR, LPD and MPD, respectively. New secondary models increased the accuracy of predictions (5 to 45 °C), with B_f and A_f for SGR, LPD, and MPD of 1.00, 1.06, and 1.00 and 1.14, 1.33, and 1.02, respectively. These new models offer improved tools for designing and implementing food safety systems and assessing the impact of E. coli O157:H7 disease.     

Modeling the effect of inoculum size and acid adaptation on growth/no growth interface of Escherichia coli O157:H7

The objective of this study was to model with logistic regression the growth/no growth interface of different initial inoculation levels (10¹, 10³ and 10⁵ CFU/ml; study 1), or nonadapted vs acid-adapted (study 2) Escherichia coli O157:H7 as influenced by pH, NaCl concentration and incubation temperature. Study 1 was conducted with a mixture of four E. coli O157:H7 strains grown (35 °C, 24 h) in tryptic soy broth (TSB). Study 2 was conducted with the same mixture of four E. coli O157:H7 strains grown (35 °C, 24 h) in glucose-free TSB with 1% added glucose (final pH 4.83), or in diluted lactic acid meat decontamination runoff fluids (washings; final pH 4.92), or nonadapted cultures prepared in glucose-free TSB (final pH 6.45), or in water washings (final pH 6.87). Parameters included incubation temperature (10–35 °C), pH (3.52–7.32), and NaCl concentration (0–10% w/v). Growth responses were evaluated for 60 days turbidimetrically (610 nm) every 5 days in 160 (study 1) and 360 (study 2) combinations in quadruplicate samples, with a microplate reader. The lower the initial inoculum the higher were the minimum pH and a_w values permitting growth. Differences in the pH and a_w growth limits among inoculum concentrations increased at 15 and 10 °C. Acid-adapted cultures were able to grow at lower pH than nonadapted cultures, while at temperatures below 25 °C, growth initiation of nonadapted cultures stopped at higher a_w compared to acid-adapted cultures for the whole pH range of 3.52 to 7.32. A comparison with available data indicated that our model for acid-adapted E. coli O157:H7 in different environments may provide representative growth probabilities covering both nonadapted and stress-adapted contaminants.     

Comparison of enrichment procedures for isolation of Escherichia coli O157:H7 from ground beef and radish sprouts

Enrichment procedures using Tryptic soy broth (TSB), modified TSB (mTSB), modified E. coli broth with novobiocin (mEC+n), mTSB (without novobiocin) with vancomycin, cefixime and cefsulodin (mTSB-VCC), or TSB with cefixime, tellurite and vancomycin (TSB-CTV) were evaluated by determining the rate of successful isolation of fifteen Escherichia coli O157:H7 strains from inoculated broth containing ground beef or radish sprout extract. E. coli O157:H7 tended to be isolated more efficiently after enrichment with TSB, mTSB and mEC+n than with the other broths. In order to identify the most efficient enrichmemt condition using these broths, E. coli O157:H7 were inoculated into 25 g ground beef or radish sprouts, which were then homogenized in 225 ml broth and incubated static at 37°C or 42°C for 6 h or 18 h. Attempts were made to isolate the inoculated bacteria by plating method in combination with the immunomagnetic separation method. The most effective enrichment condition was incubation in mTSB or mEC+n at 42°C for 18 h for ground beef, and in mEC+n at 42°C for 18 h for radish sprouts.     

Detection of Escherichia coli O157 in bovine meat products in northern Italy

Tests for Escherichia coli and E. coli O157 were carried out on meat samples collected from randomly chosen stores throughout the city of Bologna and suburban areas. The samples consisted of 25 g of loose minced beef, sometimes already shaped into meatballs or hamburgers, some of which were mixed with vegetables. The meat was purchased from retail outlets, open market stalls, and supermarket chains during 25 sampling visits from October 2000 to December 2001. For E. coli detection, Tryptone soya broth (TSB) supplemented with novobiocin and C-EC agar were used. Immunomagnetic separation with SMAC-BCIG-CT agar and chromogenic E. coli O 157 agar, API 20E system and agglutination latex test were used to detect E. coli O157; Vero cell assay and polymerase chain reaction (PCR) were used to assess toxin production and the presence of virulence genes.

E. coli were detected in 45 (30.2%) of the 149 samples examined, mainly in the hamburger samples mixed with vegetables and in the loose minced beef. E. coli O157 was found in one sample of hamburger and two samples of hamburger mixed with vegetables (2%) collected from three different butcher's stores between July and October. All the strains of E. coli O157 and most cases of E. coli were found in meat from small retailers.

The three strains of E. coli O157 were positive for verocytotoxin production. PCR analysis revealed genes coding for vt2 and one strain possessed the gene for eae A. Chromogenic E. coli O157 agar was found to be more selective and differential, allowing easier identification of suspected colonies with mixed flora and producing less false-positive colonies.     

QUANTITATIVE DETECTION OF ESCHERICHIA COLI O157:H7 IN GROUND BEEF BY IMMUNOMAGNETIC SEPARATION AND POLYMERASE CHAIN REACTION

A quantitative assay for viable Escherichia coli O157:H7 in ground beef based on immunomagnetic separation (IMS) and the polymerase chain reaction (PCR) was developed. Bacterial cells inoculated into ground beef, were captured by immunomagnetic beads (IMB) after a 6 h non-selective enrichment. The percent capture of the target cells was consistent for the inoculation levels of 0.7 to 70 colony-forming-units (CFU)/g. Captured bacteria were lysed with PCR buffer containing 0.2 mg/mL proteinase K at 65°C for 30 min. DNA sequences of Shiga-like toxin 1 and 2 (Stx 1 and 2) were amplified independently. Log-linear relationships were observed between CFU of E. coli O157:H7 inoculated into ground beef and the integrated fluorescent image of the PCR products with Stx 1 and 2 primers after enrichment. The quantitative range was between 0.7 to 70 CFU/g.     

Enterotoxigenic Escherichia coli detected in foods by PCR and an enzyme-linked oligonucleotide probe

A polymerase chain reaction (PCR) and an enzyme-linked oligonucleotide probe hybridization assay were developed for the detection of enterotoxigenic Escherichia coli (ETEC) in ground beef, chicken, pork and raw milk. Two synthetic primers, one of which was biotinylated, were used in the PCR to amplify a fragment of the E. coli heat-labile enterotoxin (LT) gene. The identity of the amplified products was confirmed by liquid hybridization using a horseradish peroxidase-linked internal oligonucleotide probe in a 96-well microplate coated with streptavidin. The final quantitation of the PCR products was performed by a colorimetric reaction. Under established conditions (including l min at 60 °C for primer annealing and extension in PCR cycles), this method detected all 7 LT-producing E. coli pathogenic for humans, but did not detect all 7 LT-positive E. coli of animal origin, 3 E. coli strains that do not produce LT, and 9 other bacteria. Under less stringent PCR conditions (55 °C for annealing and extension), 2 strains of LT-producing E. coli of porcine origin were detected while the results of other bacterial strains remained unchanged. In pure cultures, the detection limit of the method was 1.4 colony forming units (CFU). Prior to PCR amplification, all food samples inoculated with an LT-producing ETEC, were subjected to enrichment in brain heart infusion broth for 8 h at 37 °C. From these cultures, 10 μ1 was heated at 95 °C for 10 min and directly used in the PCR. An initial inoculum of as few as 1.2 to 12 CFU of the LT-producing ETEC per 25 g (or ml) of food sample gave a positive reaction.     

纺织品中大肠杆菌O157:H7的检测方法

为建立一种灵敏、特异、快速、高效地鉴定纺织品基质中大肠杆菌O157:H7的方法,筛选出大肠杆菌O157:H7特有的rfbE基因保守序列,设计PCR特异性引物和荧光双标记探针,结合免疫磁珠技术,集成创新开发一种目标菌低浓度、不可培养情况下的样品中高效、快速富集分离大肠杆菌O157:H7的技术,建立了一种针对纺织品基质的免疫磁珠富集-实时荧光定量PCR方法,其检测下限可达8 CFU/mL。利用该方法对收集到的30份阳性样品进行鉴定,鉴定结果与传统方法结果100%吻合。结果表明,新建方法稳定性强,实现了纺织品中大肠杆菌O157:H7的快速灵敏鉴定。     

A note on Escherichia coli O157:H7 serotype in Turkish meat products

255 minced beef, 101 soudjouk and 50 uncooked hamburger samples were analyzed for the presence of Escherichia coli O157:H7 serotype. m-EC and LST broths were used as selective enrichment media and SMAC agar was used as a selective isolation medium. A total of 3 E. coli O157 were isolated by conventional culture techniques; one from each of minced beef, uncooked hamburger and soudjouk but none were identified as the H7 serotype. For determination of selective media-growing cohabitant bacteria, 2645 isolates were obtained from SMAC agar. Results showed that E. coli type 1, Hafnia alvei and Citrobacter freundii were dominant competitive flora. As selective enrichment broth-growing cohabitant microflora existed at higher levels, it was too difficult to isolate E. coli O157 from these mixed flora. Therefore, conventional methods are not suitable for these types of products, because of isolation difficulties and failure to confirm.     

Influence of temperature and surfactant on Escherichia coli inactivation in aqueous suspensions treated by moderate pulsed electric fields

This research employed a conductometric technique to estimate the inactivation kinetics of Escherichia coli cells in aqueous suspensions (1 wt.%) during simultaneous pulsed electric fields (PEF) and thermal treatments. The electric field strength was E = 5 kV/cm, the effective PEF treatment time t_PEF was within 0–0.2 s, the pulse duration t_i was 10^− 3 s, the medium temperature was 30–50 °C, and the time of thermal treatment t_T was within 0–7000 s. The damage of E. coli was accompanied by cell size decrease and release of intracellular components. The synergy between PEF and thermal treatments on E. coli inactivation was clearly present. The non-ionic surfactant Triton X-100 additionally improved its inactivation. The characteristic damage time followed the Arrhenius law within the temperature range 30–50 °C with activation energies W = 94 ± 2 kJ mol^− 1 and W = 103 ± 5 kJ mol^− 1 with and without the presence of surfactant, respectively. Relations between cell aggregation, cell ζ-potentials and presence of surfactant were analysed.     

Bifidobacteria as indicators of faecal contamination in meat and meat products: detection, determination of origin and comparison with Escherichia coli

Faecal contamination of meat and meat products and its origin, whether human or animal, was determined by using the presence of bifidobacteria as an indicator. Enrichment of samples in Beerens liquid selective medium was followed by spreading onto Columbia agar containing paromomycin. In comparison with the detection of Escherichia coli (E. coli) the following results were obtained from 50 samples: E. coli. +; Bifidobacterium. +: 38; E. coli −; Bifidobacterium −: 9; E. coli, +; Bifidobacterium. −: 2; E. coli, −; Bifidobacterium. +: 1. From 39 positives samples, 50 strains of bifidobacteria were isolated. Two were of human origin, 48 of animal origin.     

Occurrence of Escherichia coli O157:H7, Listeria monocytogenes, Salmonella and Campylobacter spp. on beef carcasses in Northern Ireland

A survey of beef carcasses was conducted in all 10 European community approved abattoirs in Northern Ireland to determine the incidence of Escherichia coli O157:H7. Analyses were based on excised samples of neck meat taken less than 48 h post-kill. Overall, 780 carcasses were sampled and all were negative for E. coli O157:H7. A sub-set of samples was analysed for the presence of Listeria monocytogenes (n=200), Salmonella (n=200) and Campylobacter spp.(n=100). L. monocytogenes was not detected but Listeria innocua was found on five carcasses and Listeria seeligeri on one. Three carcasses carried salmonellas; Salmonella Mbandaka was found on two and Salmonella Thompson on one. Campylobacter spp. were not detected on any carcasses. The results indicate that very few beef carcasses in Northern Ireland appear to carry any of the four pathogens sought, and this may help explain the low incidence of E. coli O157:H7 in the Northern Ireland human population, relative to the rest of the UK.     

Validation of a manufacturing process for fermented, semidry Turkish soudjouk to control Escherichia coli O157:H7

Two soudjouk batters were prepared from ground beef (20% fat) and nonmeat ingredients and inoculated with a five-strain mixture of Escherichia coli O157:H7 to yield an initial inoculum of 7.65 log10 CFU/g. One batter contained a commercial-starter culture mixture (approximately 8.0 log10 CFU/g) and dextrose (1.5%), while the other batter relied upon a natural fermentation with no added carbohydrate. Following mixing, sausage batters were held at 4 degrees C for 24 h prior to stuffing into natural beef round casings. Stuffed soudjouk sticks were fermented and dried at 24 degrees C with 90 to 95% relative humidity (RH) for 3 days and then at 22 degrees C with 80 to 85% RH until achieving a product moisture level of approximately 40%. After fermentation and drying with an airflow of 1 to 1.5 m/s, the sticks were either not cooked or cooked to an instantaneous internal temperature of 54.4 degrees C (130 degrees F) and held for 0, 30, or 60 min. The sticks were then vacuum packaged and stored at either 4 or 21 degrees C. For each of three trials, three sticks for each treatment/batter were analyzed for numbers of E. coli O157:H7 after inoculation, after fermentation, after cooking, and after storage for 7, 14, 21, and 28 days. Reductions in numbers of E. coli O157:H7 after fermentation and drying for sticks fermented by the starter culture (pH 4.6) and for sticks naturally fermented (pH 5.5) were 1.96 and 0.28 log10 CFU/g, respectively. However, cooking soudjouk sticks produced with a starter culture and holding at 54.4 degrees C for 0, 30, or 60 min reduced pathogen numbers from an initial level after fermentation and drying of 5.69 log10 CFU/g to below a detectable level by either direct plating (<1.0 log10 CFU/g) or by enrichment. In contrast, cooking soudjouk sticks produced without an added starter culture decreased pathogen numbers from an initial level after fermentation and drying of 7.37 to 5.65 log10 CFU/g (54.4 degrees C, no hold), 5.04 log10 CFU/g (54.4 degrees C, 30 min hold), and 4.67 log10 CFU/g (54.4 degrees C, 60 min hold). In general, numbers of E. coli O157:H7 within both groups of soudjouk sticks decreased faster during storage at 21 degrees C compared to 4 degrees C. After 28 days of storage, total reductions in pathogen numbers in soudjouk sticks produced using a starter culture but that were not subsequently cooked were 7.65 and 3.93 log10 CFU/g at 21 and 4 degrees C, respectively. For naturally fermented soudjouk, total reductions varied from 4.47 to 0.45 log10 CFU/g, depending on the cooking time and storage temperature. These data provide guidelines for manufacturers of dry sausage of ethnic origin, including soudjouk, to assess the safety of their processes for control of E. coli O157:H7.     

Survival of Escherichia coli O157:H7 in dry fermented sausages containing micro-encapsulated probiotic lactic acid bacteria

Escherichia coli O157:H7 is capable of surviving the rigorous processing steps during the manufacture of dry fermented sausages. The effect of adding two probiotic organisms, Lactobacillus reuteri and Bifidobacterium longum as co-cultures with the meat starter cultures Pediococcus pentosaceus and Staphylococcus carnosus on the viability of E. coli O157:H7 in dry fermented sausages was studied. A 5 strain cocktail of E. coli O157:H7 was added at 7.4 log cfu/g to the sausage batter and challenged with either or both Lb. reuteri or B. longum before or after they were micro-encapsulated. Sausages were fermented at < or = 26 degrees C and 88% relative humidity (RH) followed by drying at 75% RH and 13 degrees C for 25 d. The pH, water activity (aw), protein, moisture, and numbers of all inoculated organisms were monitored during processing. The pH and aw decreased from 5.7 and 0.98 to 4.9 and 0.88 at the end of fermentation and drying, respectively. These processes reduced E. coli O157:H7 by 1.0 and 0.7 log cfu/g at the end of fermentation and drying, respectively. Unencapsulated Lb. reuteri with or without B. longum reduced E. coli O157:H7 by 3.0 log cfu/g and B. longum caused a 1.9 log cfu/g reduction. While micro-encapsulation increased survival of Lb. reuteri and B. longum, it reduced their inhibitory action against E. coli O157:H7.     

SENSITIVE AND RAPID DETECTION OF ESCHERICHIA COLI O157:H7 IN GROUND BEEF BY NESTED PCR INCORPORATING IMMUNOMAGNETIC SEPARATION

A protocol for detection of low numbers of E. coli O157:H7 in ground beef by nested PCR incorporating immunomagnetic separation (IMS) was developed. The protocol enabled detection of 24 colony-forming-units (CFU) in 10 g of seeded ground beef without enrichment cultivation. Differential centrifugation was used for maximally recovering the target CFU. Partial digestion of the resulting cell pellet with proteinase K at 37°C was used for the removal of beef tissue, which was required for the proper function of IMS. Within the range of 24 to 2400 CFU/10 g, a log linear relationship between the numbers of inoculated CFU and the integrated intensity of the nested PCR products was obtained with both shiga-like toxin (SLT) 1 and 2 primer pairs.     

Indigenous legume fermentation: Effect on some antinutrients and in-vitro digestibility of starch and protein

Indigenous fermentation of coarsely ground dehulled black-gram dhal slurry at 25, 30, and 35°C for 12 and 18 h reduced the levels of phytic acid and polyphenols significantly (P < 0·05). The unfermented legume batter had high amounts of phytic acid (1000 mg/100 g) and polyphenols (998 mg/100 g), and these were reduced to almost half in the product fermented at 35°C for 18 h. In-vitro digestibility of starch and protein improved significantly (P < 0·05) with increase in the temperature and period of fermentation. A significant (P < 0·01) and negative correlation found between the in-vitro digestibility and the anti-nutrient further strengthens these findings.     

Microbiological quality of 18 degrees C ready-to-eat food products sold in Taiwan

A total of 164 samples of 18 °C ready-to-eat (RTE) food products, purchased in 1999–2000 from convenience stores and supermarkets in central Taiwan, were examined to determine the microbiological quality of these products. The 18 °C RTE food products, manufactured by 16 factories, were divided into groups based on the type of food and their major ingredients. Aerobic plate count, coliforms, Escherichia coli, Bacillus cereus, Staphylococcus aureus and psychrotrophic Pseudomonas spp. were evaluated. The incidence of E. coli and coliforms in these 18 °C RTE food products was 7.9% and 75.0%, respectively, while 49.8% and 17.9% of the samples were found to contain B. cereus and S. aureus, respectively. Among the samples tested, 1.3% of the food products contained more than 10⁵ CFU g⁻¹ of B. cereus and 0.7% contained more than 10⁵ CFU g⁻¹ of S. aureus. The pH values of the samples were all below 7.0, except for cold noodles, which had pH values ranging from 5.18 to 8.20. Among the five types of 18 °C food products tested, the highest incidence of E. coli (16%) and Pseudomonas spp. (64.0%) were detected in hand-rolled sushi in a cone shape. On the other hand, the highest incidence rate of coliforms, B. cereus, and S. aureus were found in sandwiches (88%), cold noodles (66.7%) and rice balls rolled in seaweed (25.0%), respectively. Food products made of ham contained the highest incidence of coliforms (88.0%) and E. coli (16.0%), while food products containing meat and ham as the major ingredients had the highest incidence rates of B. cereus (62.5%) and S. aureus (26.1%), respectively. For coliforms, E. coli, B. cereus and S. aureus, the percentage of 18 °C RTE food products exceeding the microbiological standards for RTE food accepted by Republic of China was 75.0%, 7.9%, 49.8% and 17.9%, respectively.     

Modeling transfer of Escherichia coli O157:H7 and Staphylococcus aureus during slicing of a cooked meat product

Cross contamination is one of the most important contributing factors in foodborne illnesses originating in household environments. The objective of this research was to determine the transfer coefficients between a contaminated domestic slicing machine and a cooked meat product, during slicing. The microorganisms tested were Staphylococcus aureus (Gram positive) and Escherichia coli O157:H7 (Gram negative). The results showed that both microorganisms were able to transfer to all slices examined (20 successively sliced) and at different inoculum levels on the blade (10⁸, 10⁶ and 10⁴ cfu/blade). The results also showed that the number of log cfu transferred per slice, during slicing, decreased logarithmically for both microorganisms at inoculum levels of 8 and 6 log cfu/blade. The type of microorganism significantly influenced transfer coefficients (p < 0.05) and there was an interaction between inoculum level and transfer coefficient for S. aureus (p < 0.05), but not E. coli O157:H7. Finally, to describe bacterial transfer during slicing, two models (log-linear and Weibull) were fitted to concentration on slice data for both microorganisms (at 6 and 8 log cfu/blade), obtaining a good fit to data (R²  0.73).     

A survey of the incidence of E. coli O157 in the UK dairy industry

A survey of the incidence of Escherichia coli O157 in bovine faeces, pasteurised and unpasteurised dairy products, farm swabs and dairy factory environmental samples was undertaken. A single enrichment broth was employed, together with three detection methods, comprising a plating medium, a commercially available ELISA technique (Petrifilm) and an ELISA test under development (Organon-Teknika). For all detection methods, the efficiency of recovery, determined using artificially contaminated samples, was poor and this was attributed to the growth of competitors in the enrichment broth. Both the plating and the Organon-Teknika methods yielded a higher proportion of false positives than the Petrifilm method; however, the former two methods also detected a wider range of verotoxigenic E. coli than the Petrifilm method. Verotoxigenic E. coli were not detected in any of 1146 samples examined. The poor performance of the methodolgy may explain why the environmental incidence appears to be low although the incidence of infection by E. coli O157 is increasing.     

The persistence of infectious adenovirus (type 35) in mussels (Mytilus edulis) and oysters (Ostrea edulis)

Microbiological analyses of fruits and vegetables produced by farms in Minnesota and Wisconsin were conducted to determine the prevalence of Escherichia coli in pre-harvest fruits and vegetables. During the 2003 and 2004 harvest seasons, 14 organic (certified by accredited organic agencies), 30 semi-organic (used organic practices but not certified) and 19 conventional farms were sampled to analyze 2029 pre-harvest produce samples (473 organic, 911 semi-organic, 645 conventional). Before each harvest season, a farmer survey was conducted to collect relevant information on farm management practices that might affect the risk of E. coli contamination in fresh produce. The use of animal wastes for fertilization of produce plants increased the risk of E. coli contamination in organic (OR = 13.2, 95% CI = 2.2–61.2, P-value < 0.0001) and semi-organic (OR = 12.9, 95% CI = 2.9–56.3, P-value < 0.0001) produce significantly. Improper ageing of untreated animal manure significantly increased this risk in organic produce (OR = 4.2 95% CI = 1.7–12.3, P-value = 0.005) grown using such manure as a fertilizer. Organic growers who used cattle manure for fertilization of their crops showed significantly greater risk of contamination with the E. coli (OR = 7.4, 95% CI = 1.6–36.8, P-value = 0.003), compared to those who used other types of manure-based fertilizer. In Minnesota, organic and semi-organic produce collected from the southeastern (SE) part of the state were at a significantly greater risk of E. coli contamination (OR = 3.45, 95% CI = 1.8–35.2, P = 0.008), compared to those collected from farms located in the southern (S) regions of the state. In Wisconsin, organic and semi-organic produce collected from the southern (S) cluster of farms were at approximately 3-times greater risk of E. coli contamination (OR = 2.67, 95% CI = 1.3–9.4, P = 0.004), compared to those grown in the northern (N) cluster of farms.     

Comparison of surface sampling methods and cleanability assessment of stainless steel surfaces subjected or not to shot peening

The cleanability of AISI 304 stainless steel surfaces, indicated by the removal of Escherichia coli cells or Aspergillus niger spores was assessed by controlled inoculation and washing treatment of samples in standardised conditions. Two systems of recapture (Rodac plate technique and swabbing technique) were compared. Four industrial finishes, subjected or not to shot peening, contaminated at low concentration (1–10 cfu/cm²), and then washed with distilled water or alkaline detergent, were examined. The Rodac plate technique detected most of microorganisms inoculated (80% for E. coli cells and 67% for A. niger spores), whereas the swabbing technique recovered only 1% of the E. coli cells and 26% of the A. niger spores. Using the Rodac plate technique E. coli cells proved to be easily detachable from samples either with distilled water (98%) or alkaline detergent (>99%). For the surfaces contaminated with A. niger spores, the cleanability increased from 34% with distilled water to 77% with alkaline detergent. In these working conditions type of finish (shot treated or not) had no significant effect on cleanability of stainless steel.