Chicken Carcass Rinse Research Articles

Enrichment culture for the isolation of Campylobacter spp: Effects of incubation conditions and the inclusion of blood in selective broths

Isolation of Campylobacter spp. using enrichment culture is time consuming and complex. Reducing the time taken to confirm the presence or absence of Campylobacter spp. would have many advantages for diagnostic, commercial and research applications. Rapid techniques such as real-time PCR can detect campylobacters from complex samples but blood in enrichment culture can inhibit the PCR reaction, if applied directly to enriched samples. The aim of this study was to investigate the effect of blood in enrichment culture on the isolation of campylobacters from chicken caeca, carcass rinses and bootsock (gauze sock walked through a broiler chicken house) samples using Bolton broth. The effect of incubation temperature (37 °C or 41.5 °C for 48 h, or 37 °C for 4 h then transfer to 41.5 °C for 44 h) and method of generating atmosphere (incubation of container in jar gassed with microaerobic atmosphere or incubation of container with small headspace and tightly screwed lid in an aerobic atmosphere) with and without blood on isolation from chicken carcass rinses and chicken faeces was also investigated. The presence of blood in enrichment culture did not improve the isolation of campylobacters from chicken faeces or bootsock samples but significantly improved recovery from chicken carcass rinse samples. There was no significant effect of the method used to generate incubation atmosphere. Isolation rates did also not depend significantly on whether broths were incubated at 37 or 41.5 °C for 24 or 48 h. Overall, the presence of blood in such media is not essential, although isolation can vary depending on sample type and enrichment method used.

Quantification ofCampylobacterspp. in chicken carcass rinse by real-time PCR

In this study, a real-time quantitative polymerase chain reaction (PCR) method was examined for its ability to quantify Campylobacter spp. in chicken carcass rinses and compared with bacteriological culturing. The linearity of the real-time PCR quantification protocol was assessed on pure DNA. The amplification efficiency was 100% and the square regression coefficient (R(2)) was 0.998. Quantification was linear over at least 7 log units. Using a crude cell lysate gave the highest sensitivity and the detection limit of the method was 3.3 log CFU per carcass. The statistical correlation between the bacteriological enumeration and the real-time quantitative (Q)-PCR determined using chicken carcasses sampled at the end of the slaughter line was 0.733. The difference in detection levels was probably because of the detection of stressed, dead or viable but not culturable cells by Q-PCR. The real-time Q-PCR method described in this study is a powerful tool for determining the number of Campylobacter cells on carcasses. The real-time Q-PCR method is available to quantify the Campylobacter contamination at the slaughterhouse level and could be used to evaluate primary production.

Detection of Campylobacter jejuni and Campylobacter coli from Broiler Chicken–Related Samples Using BAX PCR and Conventional International Organization for Standardization Culture

In this study, the conventional International Organization for Standardization (ISO) culture method was compared with the DuPont Qualicon BAX system, a high-throughput, rapid molecular assay that can be used to detect several bacterial species, including Campylobacter jejuni and Campylobacter coli in diverse sample types. Standard enrichment culture is a time-consuming process, taking up to 6 days to obtain a confirmed result. Rapid molecular assays have been developed that provide results within 24 h. Naturally contaminated samples from the poultry production chain were examined for the presence of Campylobacter spp. Samples from broiler chicken ceca (n = 100), fresh chicken carcass rinses (n = 60), and bootsocks (gauze sock walked through a broiler chicken house; n = 50) were enriched according to the ISO 10272 method in Bolton broth specifically designed to detect Campylobacter spp. in complex sample types. Samples were enriched without blood for use with the BAX system using the Campylobacter BAX kits for the detection of C. jejuni and C. coli. Samples also were directly plated onto modified charcoal cefperazone deoxycholate agar, and results were compared with those from the enriched samples for the ability to detect Campylobacter spp. Campylobacter spp. were isolated from 49% of samples with conventional enrichment cultures, from 48% with direct culture, from 68% with the BAX system and enrichment cultures, and from 62% with the BAX system used directly with samples. Overall, the BAX system detected more positive samples than did the conventional culture method and is an effective methodology for the rapid and reliable detection of Campylobacter spp. from diverse sample types.

ADDITION OF SULFAMETHOXAZOLE TO SELECTIVE MEDIA AIDS IN THE RECOVERY OF CAMPYLOBACTER SPP. FROM BROILER RINSES

ABSTRACT The association of Campylobacter spp. with raw poultry products has been well established. Campy‐Line agar (CLA) is a recently developed selective culture medium that allows very few non‐Campylobacter colonies to grow. The few contaminants able to grow on CLA from typical broiler chicken carcass rinses were identified and found to be sensitive to the antimicrobial agent sulfamethoxazole (SMX). The purpose of our experiment was to determine the influence of SMX on recovery of C. jejuni from broiler carcass rinse samples when added to Campy‐Cefex agar or CLA. Cefex and CLA were prepared with and without the addition of 25 mg SMX/L media. Broiler carcass rinse samples (post‐pick, n = 80 and post‐chill, n = 80) were obtained from eight different commercial processors across the United States and were surface plated on the selective agars. Both Cefex and CLA with and without SMX recovered similar populations of Campylobacter; however, significantly fewer contaminants were observed on the Cefex with added SMX and the CLA with or without SMX compared to normal Cefex. The more selective CLA with SMX had no contaminants present from this sample type, which simplified enumeration. Addition of SMX should be considered for increasing selectivity of Campylobacter‐specific media.PRACTICAL APPLICATIONSThe addition of sulfamethoxazole to Campylobacter‐selective agar can reduce the number of contaminants on the agar and facilitate enumeration of Campylobacter colonies.

DETECTION OF MULTIDRUG‐RESISTANT SALMONELLA TYPHIMURIUM DT104 IN POULTRY BY SELECTIVE ENRICHMENT AND CLOTH‐BASED HYBRIDIZATION ARRAY SYSTEM

ABSTRACT A rapid method was devised for the selective enrichment and detection of multi‐antibiotic‐resistant Salmonella enterica subsp. enterica serotype Typhimurium (S. Typhimurium) DT104 in poultry. The target organism was pre‐enriched in trypticase soy broth supplemented with chloramphenicol, followed by plating on modified semisolid Rappaport Vassiliadis medium and sampling a portion of the swarming growth. The presence of S. Typhimurium DT104 was determined by testing the growth using a cloth‐based hybridization array system (CHAS) targeting antibiotic resistance and other marker genes associated with this organism. In this CHAS, a multiplex polymerase chain reaction incorporating digoxigenin–dUTP was used to simultaneously amplify seven target gene sequences, with subsequent rapid detection of the amplicons by hybridization with an array of probes immobilized on polyester cloth and immunoenzymatic assay of the bound label. This procedure permitted the rapid determination of S. Typhimurium DT104 in chicken carcass rinse, powdered egg and feed samples inoculated with different levels of the target organism.PRACTICAL APPLICATIONSThe combined selective enrichment and CHAS procedure will enable the rapid screening of poultry and related products for the presence of multidrug resistant Salmonella Typhimurium DT104. The convenience of this approach lies in the fact that samples containing salmonellae requiring more comprehensive analysis can be rapidly identified on the basis of a simple preliminary enrichment procedure involving examination of MSRV plating media for characteristic swarming growth. The swarming growth is readily sampled and analyzed by the DT104 CHAS to determine the presence of key marker genes associated with the multidrug resistant pathogen, obviating the need for time‐ and labor‐consuming conventional purification and antimicrobial susceptibility testing procedures.

Statistical comparison of Campylobacter jejuni subtypes from human cases and environmental sources

To analyse Campylobacter jejuni typing data to define statistically which potential reservoirs and transmission sources contain isolates that are most similar to one another and to isolates from human infections. Serotyping and SmaI macrorestriction profiling data for C. jejuni isolates from human campylobacteriosis cases, chicken carcass rinses, duck, sheep, dairy and beef cattle faeces, river water, and sheep, beef and pork offal obtained from a defined rural area of New Zealand were compared using the Czekanowski proportional similarity index. Subtypes of isolates from ruminant animals, whether derived from their faeces or offals, were generally similar to one another. The spectrum of isolate subtypes from human cases was more similar to that from ruminant faeces than the other matrices considered. Isolate subtypes from chicken rinses, pork offal, water and duck faeces were not highly similar to those from other matrices. Results from a combination of phenotypic and genotypic approaches suggest that, for this rural population, exposures associated with a rural lifestyle may be significant sources of human campylobacteriosis. The Czekanowski index was applied to subtyping data and supported the greater importance of contact with livestock in campylobacteriosis cases associated with a rural setting, in comparison with urban studies that have identified poultry-related factors.

A real-time PCR for the detection of Salmonella Enteritidis in poultry meat and consumption eggs

A robust duplex 5′ nuclease (TaqMan) real-time PCR was developed and in-house validated for the specific detection of Salmonella enterica subspecies enterica serovar Enteritidis in whole chicken carcass rinses and consumption eggs. The assay uses specifically designed primers and a TaqMan probe to target the Prot6e gene located on the S. Enteritidis specific 60-kb virulence plasmid. As an internal amplification control to monitor Salmonella DNA in the sample, a second primer/TaqMan probe set detects simultaneously the Salmonella specific invA gene. The assay identified correctly 95% of the 79 Salmonella Enteritidis strains tested comprising 19 different phage types. None of the 119 non-Enteritidis strains comprising 54 serovars was positive for the Prot6e gene. The assay detection probability was for 10 2 or more genome equivalents 100% and for 10 equivalents 83%. A pre-PCR sample preparation protocol including a pre-enrichment step in buffered peptone water, followed by DNA extraction was applied on low levels of artificially contaminated whole chicken carcass rinses and eggs from hens as well as 25 potentially naturally contaminated chickens. The detection limit was less than three CFU per 50 ml carcass rinse or 10 ml egg. The sensitivity and specificity compared to the traditional culture-based detection method and serotyping were both 100%. Twenty-five potentially naturally contaminated chickens were compared by the real-time PCR and the traditional cultural isolation method resulting in four Salmonella positive samples of which two were positive for the Prot6e gene and serotyped as S. Enteritidis. We show also that Salmonella isolates which have a rough lipopolysaccharide structure could be assigned to the serovar Enteritidis by the real-time PCR. This methodology can contribute to meet the need of fast identification and detection methods for use in monitoring and control measures programmes.

BIPHASIC MICROTITER METHOD FOR CAMPYLOBACTER RECOVERY AND ENUMERATION

We developed a biphasic method for recovery and enumeration of campylobacters. The biphasic system was composed of 96-well microtiter plates containing Campy–Line agar prepared 2¥ for all ingredients except for 1¥ agar (0.1 mL per well). Samples were prepared in either twofold or fivefold dilution series across separate 96-well plates and directly transferred (0.1 mL) to the agar-containing microtiter plates to create the biphasic system. Biphasic plates were incubated for up to 48 h at 42C either aerobically or microaerobically in a gas mixture of 5% O2, 10% CO2 and 85% N2. Campylobacter was recovered in the aerobically incubated biphasic plates; however, significantly greater Campylobacter recovery was obtained in the biphasic plates incubated microaerobically (P 0.05). Significantly higher numbers of injured campylobacters from chicken carcass rinse samples were recovered by the biphasic method compared with conventional direct plating techniques (P 0.05).

SalmonellaEnteritidis in Broiler Chickens, United States, 2000–2005

US Department of Agriculture Food Safety and Inspection Service (FSIS) data on Salmonella enterica serotype Enteritidis in broiler chicken carcass rinses collected from 2000 through 2005 showed the annual number of isolates increased >4-fold and the proportion of establishments with Salmonella Enteritidis-positive rinses increased nearly 3-fold (test for trend, p<0.0001). The number of states with Salmonella Enteritidis in broiler rinses increased from 14 to 24. The predominant phage types (PT) were PT 13 and PT 8, 2 strains that a recent Foodborne Diseases Active Surveillance Network (FoodNet) case-control study associated with eating chicken. FSIS is directing more sampling resources toward plants with marginal Salmonella control to reduce prevalence in products including broilers. The policy targets establishments with common Salmonella serotypes of human illness, including Salmonella Enteritidis. Voluntary interventions should be implemented by industry.

Use of Negative Air Ionization for Reducing Bacterial Pathogens and Spores on Stainless Steel Surfaces

The use of chemicals in food plant sanitation for removing and killing microorganisms could be reduced by the use of alternative nonchemical interventions. Supercharged negative air ionizers have shown potential to effectively reduce airborne and surface microorganisms. In our earlier studies, a small chamber, controlled at 85% relative humidity and supercharged with a −25 kV electrostatic space charge system (ESCS), was used to transfer a strong negative charge to bacteria on stainless steel surfaces. The ESCS treatment caused the levels of biofilm bacteria from chicken carcass rinses to be significantly decreased with 99.8% efficiency at a distance of 18 cm with ion densities of 106 negative ions/cm3 or more. In the present study, effects of the −25 kV charge of ESCS on specific pathogens important for food safety were studied. Treatment of Campylobacter jejuni, Escherichia coli, Salmonella enteritidis, Listeria monocytogenes, and Staphylococcus aureus achieved up to a 4 log reduction with 99.9% reduction efficiency in 3 h. Treatment of bacterial spores of Bacillus stearothermophilus achieved up to a 3 log reduction with a 99.8% reduction efficiency in 3 h. These significant reductions for 5 species of pathogenic bacteria and bacterial spores suggest that the ESCS is a promising alternative treatment for reduction of microbial load in a food-processing facility with the potential to reduce the amount of antimicrobials used.

Evaluation of a 24-Hour Bioluminescent Enzyme Immunoassay for the Rapid Detection of Salmonella in Chicken Carcass Rinses

A bioluminescent enzyme immunoassay (BEIA), using Salmonella-specific monoclonal antibody M183 for capture and biotinylated monoclonal antibody M183 for detection, was developed with InteLite AB streptavidin-biotinylated firefly luciferase complex as a reporter. Salmonella cultures were preenriched in buffered peptone water with shaking for 6 h at 37°C and then selectively enriched in Muller-Kauffmann tetrathionate (MKTT) broth and modified semisolid Rappaport-Vassiliadis (MSRV) medium for 16 h at 42°C. After enrichment, the total test time for the BEIA was 1.5 h. The analytical sensitivity of the BEIA ranged from 6.0 × 102 CFU/ml to 1.2 × 105 CFU/ml in MKTT and from 1.4 × 105 to 2.3 × 106 CFU/ml in MSRV using six Salmonella serovars prevalent in Canada. With enrichment cultures, the BEIA detected 1 CFU of Salmonella Typhimurium and Salmonella Enteritidis in 25 ml of chicken rinses. Representative strains of 10 Salmonella serovars were detected, and cross-reactivity was not observed with 25 non-Salmonella foodborne bacteria. The BEIA performance was assessed by testing 420 poultry samples, which were analyzed in parallel with the standard MSRV culture method. The BEIA detected 117 (27.88%) Salmonella-positive samples, whereas the standard MSRV culture method detected 124 (29.5%). The BEIA had a sensitivity of 64.5% and a specificity of 87.5% compared to the standard MSRV culture method. However, similar specificities and sensitivities were obtained when the standard MSRV culture method was compared to the BEIA (sensitivity = 68.4% and specificity = 85.5%). Neither method detected 100% of the Salmonella found in the samples tested, and statistical analyses indicated no significant difference between the two methods. In summary, the BEIA offers another alternative for the detection of Salmonella, with the additional advantage of providing a 24-h test for detecting Salmonella in chicken carcass rinses. The results obtained in this research indicate that tests are still needed for the isolation and detection of Salmonella that will establish the true prevalence of Salmonella in chicken samples.

Detection of Salmonella from Chicken Rinses and Chicken Hot Dogs with the Automated BAX PCR System

The BAX system with automated PCR detection was compared with standard cultural procedures for the detection of naturally occurring and spiked Salmonella in 183 chicken carcass rinses and 90 chicken hot dogs. The automated assay procedure consists of overnight growth (16 to 18 h) of the sample in buffered peptone broth at 35°C, transfer of the sample to lysis tubes, incubation and lysis of the cells, transfer of the sample to PCR tubes, and placement of tubes into the cycler-detector, which runs automatically. The automated PCR detection assay takes about 4 h after 16 to 24 h of overnight preenrichment. The culture procedure consists of preerichment, enrichment, plating, and serological confirmation and takes about 72 h. Three trials involving 10 to 31 samples were carried out for each product. Some samples were spiked with Salmonella Typhimurium, Salmonella Heidelberg, Salmonella Montevideo, and Salmonella Enteritidis at 1 to 250 cells per ml of rinse or 1 to 250 cells per g of meat. For unspiked chicken rinses, Salmonella was detected in 2 of 61 samples with the automated system and in 1 of 61 samples with the culture method. Salmonella was recovered from 111 of 122 spiked samples with the automated PCR system and from 113 of 122 spiked samples with the culture method. For chicken hot dogs, Salmonella was detected in all 60 of the spiked samples with both the automated PCR and the culture procedures. For the 30 unspiked samples, Salmonella was recovered from 19 samples with the automated PCR system and from 10 samples with the culture method. The automated PCR system provided reliable Salmonella screening of chicken product samples within 24 h.

Toward an international standard for PCR-based detection of food-borne thermotolerant Campylobacters: assay development and analytical validation.

As part of a European research project (FOOD-PCR), we developed a standardized and robust PCR detection assay specific for the three most frequently reported food-borne pathogenic Campylobacter species, C. jejuni, C. coli, and C. lari. Fifteen published and unpublished PCR primers targeting the 16S rRNA gene were tested in all possible pairwise combinations, as well as two published primers targeting the 23S rRNA gene. A panel of 150 strains including target and nontarget strains was used in an in-house validation. Only one primer pair, OT1559 plus 18-1, was found to be selective. The inclusivity and exclusivity were 100 and 97%, respectively. In an attempt to find a thermostable DNA polymerase more resistant than Taq to PCR inhibitors present in chicken samples, three DNA polymerases were evaluated. The DNA polymerase Tth was not inhibited at a concentration of 2% (vol/vol) chicken carcass rinse, unlike both Taq DNA polymerase and DyNAzyme. Based on these results, Tth was selected as the most suitable enzyme for the assay. The standardized PCR test described shows potential for use in large-scale screening programs for food-borne Campylobacter species under the assay conditions specified.

EFFECTS OF CORROSIVE TREATMENT ON STAINLESS STEEL SURFACE FINISHES AND BACTERIAL ATTACHMENT

Corrosion, an important factor for the durability of a metal finish after exposure to water and chemicals, is a realconcern for many wet-process industries. The effects of rouging, corrosion, and biofouling are costly problems on the surfaceof stainless steel, the most common material in processing plants. We have developed a corrosive treatment that is indicativeof the wet-processing conditions commonly used in food processing, pharmaceutical, and bioprocess applications to test theeffects of surface corrosion on bacterial attachment. Samples of surface finishes (electropolished, steel-ball burnished,glass-beaded, acid-dipped, steel-shot burnished, and sandblasted) were compared with mill finish controls to determine thevariation in bacterial attachment on each finish. A duplicate set of samples was exposed to the corrosive treatment to simulateprocessing conditions. All samples were examined by visual inspection and electron probe microanalysis for surfacecharacteristics and elemental composition of the stainless steel finishes. Samples were exposed to natural bacterialpopulations from chicken carcass rinses to allow growth of bacteria and development of biofilms on the surfaces. The kineticsof bacterial growth during surface exposure was followed by UV-visible spectrophotometry, and counts of bacteria and earlybiofilm formation were determined from micrographs following scanning electron microscopy. Bacterial attachment on eachsurface finish was measured and compared with controls and the five other finishes. Exposure to the corrosive treatmentconditions resulted in changes in the numbers of bacteria that attached to each surface finish. After exposure to corrosivetreatment, significantly greater numbers of bacteria attached to steel-ball burnished and glass-beaded finishes. However,the control mill finish and electropolished samples had fewer bacteria attached after exposure. Electropolished samples weresignificantly most resistant, before and after exposure to corrosive treatment, than the seven other finishes tested.

A Double Antibody Sandwich Enzyme-Linked Immunosorbent Assay for the Detection of Salmonella Using Biotinylated Monoclonal Antibodies

A double antibody sandwich enzyme-linked immunosorbent assay (ELISA) was developed using monoclonal antibodies (MAbs) as a rapid, economical alternative to culture isolation procedures for detection of Salmonella. Four MAbs previously shown to react with Salmonella strains representing 18 different serogroups were evaluated as capture antibodies and, after biotinylation, as detection antibodies. One MAb (M183) was selected for use in the ELISA to capture and detect Salmonella antigens. The detection limit of the ELISA was evaluated using Salmonella enterica subspecies enterica serovar Typhimurium and various selective and nonselective Salmonella enrichment media. The highest detection limit (ca. 104 CFU/ml) was achieved using an enrichment broth containing brain heart infusion, yeast extract, sodium hydrogen selenite, and sodium cholate (BYSC) after preenrichment in buffered peptone water. The ELISA detected all Salmonella serovars tested, which included representative serovars of serogroups B, C, D, and E and gave negative results for all non-Salmonella species tested. Samples (106) from various sources, including fecal samples from humans and pigeons, chicken carcass rinses, chicken parts, feed, and the environment, were used to evaluate the performance of the ELISA. The ELISA had a specificity and sensitivity of 100 and 91%, respectively, and a kappa value of 0.93 relative to the culture methods. Such an ELISA has the potential to be used in the implementation of the pathogen reduction and hazard analysis critical control point systems as well as in clinical laboratories.

PARAMETERS OF TREATED STAINLESS STEEL SURFACES IMPORTANT FOR RESISTANCE TO BACTERIAL CONTAMINATION

Use of materials that are resistant to bacterial contamination could enhance food safety during processing.Common finishing treatments of stainless steel surfaces used for components of poultry processing equipment were tested forresistance to bacterial attachment. Surface characteristics were evaluated to determine factors important for resistance.Disks of stainless steel were steelball burnished, glassbeaded, electropolished, aciddipped, sandblasted, or left untreated.After treatment, the disks were incubated with bacteria from chicken carcass rinses. Bacterial growth during surface exposurewas monitored by spectrophotometry, and bacterial counts were measured by scanning electron microscopy (SEM). Themorphology of the surfaces was analyzed by atomic force microscopy (AFM), using disks from each of the treatments in theSEM studies. Changes in root mean square (RMS) roughness, center line average, bearing ratio/area, and other measurementscorresponded to changes in bacterial contamination. Electropolished stainless steel showed fewer bacteria and biofilmformations than the other surfaces. The elemental composition of the surface was not changed by electropolishing. This articleis the first to show that AFM is a rapid method for predicting the potential resistance of a surface to bacterial contamination.These results will aid manufacturers and processors in comparing and selecting finishes that are costeffective and resistantto contamination.

Evaluation of a Selective Broth for Detection of Staphylococcus aureus Using Impedance Microbiology

Experiments were conducted to evaluate a selective nutrient broth containing acriflavine and nalidixic acid for detection of Staphylococcus aureus using an impedance microbiological method. Nine species of bacteria, other than S. aureus, were evaluated using the selective broth to determine if these species could be inhibited. A total of 10 ppm of nalidixic acid inhibited the gram-negative species tested, with the exception of Pseudomonas aeruginosa. Similarly, 10 ppm of acriflavine suppressed the Staphylococcus spp. examined; however, S. aureus retained the ability to proliferate. Nutrient broth solution containing 10 ppm of nalidixic acid and 10 ppm of acriflavine (S. aureus impedance broth [SIB]) inhibited multiplication of most of the bacterial species tested and allowed S. aureus to be detected in an average of 16.4 h. Fresh chicken carcass rinses and cooked chicken rinses were inoculated with Escherichia coli and S. aureus and assayed using SIB in conjunction with impedance. Results demonstrated that S. aureus could be detected in less than 11.5 h, although the presence of E. coli decreased detection times. Additionally, impedance assays were conducted using five different poultry products to evaluate the sensitivity of the broth for detecting S. aureus. S. aureus could be detected on poultry products when present at low levels (101 CFU/ml) in less than 24 h. These studies demonstrated that SIB may be used in conjunction with impedance for rapid detection of S. aureus. However, without further modification, this method should not be used for enumeration of S. aureus from samples containing mixed microflora.

Surface finishes on stainless steel reduce bacterial attachment and early biofilm formation: scanning electron and atomic force microscopy study

Three common finishing treatments of stainless steel that are used for equipment during poultry processing were tested for resistance to bacterial contamination. Methods were developed to measure attached bacteria and to identify factors that make surface finishes susceptible or resistant to bacterial attachment and biofilm formation. Samples of the treated surfaces (sand-blasted, sanded, and electropolished) were exposed to natural bacterial populations from chicken carcass rinses to allow growth of bacteria and development of biofilms on the surfaces. The kinetics of bacterial growth during surface exposure was followed by UV-visible spectrophotometry, and counts of bacteria and early biofilm formation were measured following scanning electron microscopy (SEM). The surface morphology of the samples was analyzed by atomic force microscopy (AFM) with samples from each of the batches of treatments used in the SEM studies. Relative differences in the surface morphology, including fractal dimensions, Z ranges, roughness, and other measurements corresponded by treatment with the differences in reduction of bacterial counts shown by SEM. The surface types varied in affinity for bacteria, and both physical and electrochemical treatments improved resistance of stainless steel to bacterial attachment. Electropolished stainless steel was the least rough surface and showed significantly fewer bacterial cells and beginning biofilm formations than the other treated surfaces. Food safety could be improved if bacterial populations could be reduced during processing by increasing the use of materials that are resistant to bacterial contamination. These findings will aid equipment manufacturers and processors in selecting materials and finishes that are most resistant to bacteria and biofilm formation.

A rapid DNA isolation procedure for the identification of Campylobacter jejuni by the polymerase chain reaction.

We have developed an efficient process for rapidly isolating campylobacter DNA using mechanical disruption combined with the guanidine-based reagent DNAzol. Template DNA was isolated by this method from cultures of Campylobacter jejuni resistant to lysis by boiling or enzymes and identified following polymerase chain reaction (PCR) amplification using primers specific for the hippuricase gene. Direct detection of campylobacters in poultry-processing samples by PCR is demonstrated in chicken carcass rinses spiked with lysis-resistant C. jejuni. Our results indicate that this method of DNA isolation may be ideal for direct PCR detection of pathogenic bacteria in complex samples of widely varied origin, especially when the target organisms are difficult to lyse by other means.

Specificity of a Conductance Assay for Enumeration of Escherichia coli from Broiler Carcass Rinse Samples Containing Genetically Similar Species

Experiments were conducted to evaluate the specificity of a rapid method for enumeration of Escherichia coli from fresh broiler chicken carcasses. In three separate trials, E. coli, Citrobacter freundii, Salmonella Enteritidis, and Shigella sonnei were serially diluted and then inoculated into identical broiler chicken carcass rinses. Inoculated rinses were mixed with double-strength Coliform Medium supplemented with 2% dextrose. This mixture was placed in a Bactometer module in duplicate, and conductance was measured at 44°C. Results indicated that C. freundii did not grow to an appreciable degree in the selective medium at 44°C. Salmonella Enteritidis grew similarly to E. coli; however, an initial level of 106Salmonella in the food product would be required for Salmonella to interfere with enumeration of E. coli using this method. S. sonnei grew at a more rapid rate than E. coli; however, there was an interaction between the regression lines formed when serial dilutions (log10 CFU/ml) were compared to E. coli detection times for these two species of bacteria. Therefore, high levels of S. sonnei in a food sample may interfere with the enumeration of E. coli. In general, Salmonella and Shigella are not found at high enough levels on poultry products to interfere with enumeration of E. coli using this method and, if found at high levels, would be detected and rejected using this procedure. Hence, the presence of organisms that are genetically and phylogenetically similar to E. coli would not preclude enumeration of E. coli using conductance under these conditions.