Survey of retail alfalfa sprouts and mushrooms for the presence of Escherichia coil O157:H7, Salmonella,and Listeria with BAX,and evaluation of this polymerase chain reaction-based system with experimentally contaminated samples

BAX, a polymerase chain reaction (PCR)-based pathogen detection system, was used to survey retail sprouts and mushrooms for contamination with Escherichia coli O157:H7, Salmonella, Listeria spp., and Listeria monocytogenes. No Salmonella or E. coli O157:H7 was detected in the 202 mushroom and 206 alfalfa sprout samples screened. L. monocytogenes was detected in one sprout sample, and seven additional sprout samples tested positive for the genus Listeria. BAX also detected Listeria species in 17 of the mushroom samples. Only 6 of 850 PCR assays (0.7%) failed to amplify control DNA, and therefore reagent failures and the inhibition of PCR by plant compounds were rare. The sensitivity of the detection system was evaluated by assaying samples inoculated with 10 CFU of each of the pathogens. One hundred seventy-two alfalfa sprout samples were inoculated with E. coli O157:H7, and two sets of 130 samples were experimentally contaminated with Salmonella Enteritidis and L. monocytogenes. The frequency of detection depended on the protocols used for inoculation and culturing. Inoculation of samples with approximately 10 CFU from frozen stocks yielded detection rates of 87.5 and 94.5% for L. monocylogenes and Salmonella Enteritidis, respectively, in mushrooms. The corresponding rates for alfalfa sprouts were 94.5 and 76.3%. The E. coli O157:H7 detection rate was 100% for mushrooms but only 48.6% for sprouts when standard BAX culture protocols were used. The substitution of an overnight incubation in modified E. coli medium for the 3-h brain heart infusion incubation increased the rate of E. coli O157:H7 detection to 75% for experimentally contaminated sprouts. The detection rate was 100% when E. coli O157:H7 cells from a fresh overnight culture were used for the inoculation. Test sensitivity is therefore influenced by the type of produce involved and is probably related to the growth of pathogens in the resuscitation and enrichment media.     

OCCURRENCE OF ESCHERICHIA COLIO157:H7/O157, LISTERIA MONOCYTOGENES AND SALMONELLA SPP. IN BEEF SLAUGHTERHOUSE ENVIRONMENTS, EQUIPMENT AND WORKERS

Escherichia coli O157/O157:H7, Listeria monocytogenes and Salmonella spp. are major foodborne pathogens and the emergence of these pathogens has been reported in many countries. The aim of this study was to investigate contamination of the beef slaughterhouse environment, equipment and workers with E. coli O157/O157:H7, L. monocytogenes and Salmonella spp. For this study, 500 swab samples were taken from 19 different points in five privately owned slaughterhouses, their periphery, slaughterhouse equipment and slaughterhouse employees. The presence of E. coli O157:H7/O157, L. monocytogenes and Salmonella spp. was determined with the application of the immunomagnetic separation method. Our study showed that the swabs taken from the five slaughterhouses contained E. coli O157:H7 in the environment, equipment, abattoir workers and water with a frequency 0.31, 1, 1.42 and 0%, respectively; while E. coli O157 was evident in the environment, equipment, abattoir workers and water with a ratio of 15, 10, 10 and 0%, respectively; L. monocytogenes was detected in the environment, equipment, abattoir workers and water at a ratio of 4.37, 15, 5.71 and 0%, respectively; and Salmonella spp. occurrence in the environment, equipment, abattoir workers and water at a ratio of 3.43, 16, 11.42, and 0%, respectively. Implementing hazard analysis critical control point principles in work procedures would definitely reduce the gross contamination occurring in abattoirs.

PRACTICAL APPLICATIONS

This study has revealed the effect of personnel and equipment on the contamination routes of E. coli O157:H7, Listeria monocytogenes and Salmonella spp. in meat in slaughterhouses and showed that especially L. monocytogenes and Salmonella spp. may pose a higher risk than E. coli O157:H7 in slaughterhouses.     

Evaluation of a polymerase chain reaction-based system for detection of Salmonella enteritidis, Escherichia coli O157:H7, Listeria spp., and Listeria monocytogenes on fresh fruits and vegetables

A polymerase chain reaction (PCR)-based detection system, BAX, was evaluated for its sensitivity in detecting Salmonella Enteritidis, Escherichia coli O157:H7, Listeria sp., and Listeria monocytogenes on fresh produce. Fifteen different types of produce (alfalfa sprouts, green peppers, parsley, white cabbage, radishes, onions, carrots, mushrooms, leaf lettuce, tomatoes, strawberries, cantaloupe, mango, apples, and oranges) were inoculated, in separate studies, with Salmonella Enteritidis, E. coli O157:H7, and L. monocytogenes down to the predicted level of 1 CFU per 25-g sample. Detection by BAX was compared to recovery of the inoculated bacteria by culture methods according to the Food and Drug Administration's (FDA) Bacteriological Analytical Manual (BAM). BAX was essentially as sensitive as the culture-based method in detecting Salmonella Enteritidis and L. monocytogenes and more sensitive than the culture-based method for the detection of E. coli O157:H7 on green pepper, carrot, radish, and sprout samples. Detection of the pathogenic bacteria in samples spiked with a predicted number of less than 10 CFU was possible for most produce samples, but both methods failed to detect L. monocytogenes on carrot samples and one of two mushroom and onion samples spiked with less than 100 CFU. Both BAX and the culture method were also unable to consistently recover low numbers of E. coli O157:H7 from alfalfa sprouts. The PCR method allowed detection of Salmonella Enteritidis, E. coli O157:H7, and L. monocytogenes at least 2 days earlier than the conventional culture methods.     

鲜切果蔬中4 种病原微生物多重PCR检测技术

研发可同时检测鲜切果蔬中的单核细胞性李斯特菌、鼠伤寒沙门菌、金黄色葡萄球菌和大肠杆菌O157:H7的多重聚合酶链式反应（polymerase chain reaction,PCR）检测方法。根据单核细胞性李斯特菌inlA基因、鼠伤寒沙门菌invA基因、大肠杆菌O157:H7 wzy基因、金黄色葡萄球菌nuc基因设计及筛选出4?对引物。对多重PCR体系及条件进行优化。该方法对单核细胞性李斯特菌、鼠伤寒沙门菌、金黄色葡萄球菌和大肠杆菌O157:H7的检出限分别为3.5×106、1.6×105、2.4×105、4.8×105?CFU/mL。将优化的多重PCR方法对不同接种量富集后验证,结果表明,经过9?h富集后,该方法检出限为1?CFU/mL。该方法在鲜切莴苣、鲜切黄瓜、鲜切木瓜、鲜切哈密瓜中应用同样可扩增出4?条目标菌。因此,利用所建立的多重PCR方法对鲜切果蔬中侵染的病原菌检出限可达到1?CFU/g。该方法相较于传统的培养检测方法具有节约大量的劳力、试剂、时间等优点,检测时间也由原来的5～7?d缩短至9～11?h,对于企业或分析检验中心大批量样品的监测具有指导意义。     

多重PCR检测冷却肉中的3种致病菌

分别针对沙门氏菌(Salmonella choleraesuissubs.choleraesuis,S)编码DNA结合蛋白的基因hns、大肠O157:H7(Escherichia coliO157:H7,E)编码外膜蛋白紧密素的基因eaeA和单核细胞增生李斯特氏菌(Listeria monocytogenes,L)溶血素O基因Hly设计3对引物,建立同步检测肉制品中3中致病菌的多重PCR方法。通过对多重PCR特异性和灵敏度进行分析,对多重PCR反应条件进行优化,结果表明,此方法简便、快速,可使混菌检测灵敏度达到103cfu/mL。     

Reduction of Listeria monocytogenes, Salmonella spp., and Escherichia coli O157:H7 During Processing of Country-cured Hams

ABSTRACT: The country-cured ham process, including curing, equalization, cold-smoked or nonsmoked, and aging up to 6 mo, was validated and showed its effectiveness in achieving a 6-log reduction of Listeria monocytogenes, Salmonella spp., and Escherichia coli O157:H7. The viable counts of L. monocytogenes populations decreased to below detection levels after 206 d, Salmonella populations required 122 d, and E. coli O157:H7 required 66 d. However, L. monocytogenes -inoculated hams were positive and Salmonella spp-inoculated and E. coli O157:H7-inoculated hams were negative following enrichment procedures at the end of the aging process. Therefore, the survival of L. monocytogenes on country-cured ham represents a risk.     

A note on the incidences of Salmonella spp., Listeria spp. and Escherichia coli O157:H7 serotypes in Turkish sausage (Soudjouck)

The incidence of Salmonella spp., Listeria monocytogenes and Escherichia coli O157:H7 was determined in 100 Turkish sausage (soudjouck) samples collected from shops and markets in the Afyon province, Turkey. Salmonella spp. were detected in 7% of the samples. All of the isolates were S. enterica Paratyphi B. In addition, Listeria spp. were detected in 9% of the samples. Its distribution was 7% L. monocytogenes and 1% each of L. ivanovii and L. innocua. Serological study of the seven L. monocytogenes isolates showed that three of these were 1/2 ab, three were 5/6 ab and one was 1 ab. E. coli O157:H7 was not detected in any of the samples. The pH values of the samples ranged from 4.8 to 6.5. In conclusion, increasing number of listeriosis and salmonellosis cases in Turkey and the contamination levels found indicate that risk assessment and improved preventive measures are required for these sausages.     

Prevalence of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella in two geographically distant commercial beef processing plants in the United States

For two large beef processing plants, one located in the southern United States (plant A) and one located in the northern United States (plant B), prevalence of Escherichia coli O157:H7, Listeria spp., Listeria monocytogenes, and Salmonella was determined for hide, carcass, and facility environmental samples over the course of 5 months. The prevalence of E. coli O157:H7 (68.1 versus 55.9%) and Salmonella (91.8 versus 50.3%) was higher (P < 0.05), and the prevalence of Listeria spp. (37.7 versus 75.5%) and L. monocytogenes (0.8 versus 18.7%) was lower (P < 0.05) for the hides of cattle slaughtered at plant A versus plant B. Similarly, the prevalence of Salmonella (52.0 versus 25.3%) was higher (P < 0.05) and the prevalence of Listeria spp. (12.0 versus 40.0%) and L. monocytogenes (1.3 versus 14.7%) was lower (P < 0.05) for the fence panels of the holding pens of plant A versus plant B. The prevalence of E. coli O157:H7 (3.1 versus 10.9%), Listeria spp. (4.5 versus 14.6%), and L. monocytogenes (0.0 versus 1.1%) was lower (P < 0.05) for preevisceration carcasses sampled at plant A versus plant B. Salmonella (both plants), Listeria spp. (plant B), and L. monocytogenes (plant B) were detected on fabrication floor conveyor belts (product contact surfaces) late during the production day. For plant B, 21 of 148 (14.2%) late-operational fabrication floor conveyor belt samples were L. monocytogenes positive. For plant B, E. coli O157:H7 and L. monocytogenes were detected in preoperational fabrication floor conveyor belt samples. Overall results suggest that there are regional differences in the prevalence of pathogens on the hides of cattle presented for harvest at commercial beef processing plants. While hide data may reflect the regional prevalence, the carcass data is indicative of differences in harvest practices and procedures in these plants.     

主要食源性致病菌的PCR检测方法优化及在冷鲜猪肉病原污染调查中的应用

为优化针对主要食源性致病菌的PCR鉴定体系,以及了解猪肉制品中主要食源性致病菌的污染状况,对文献中报道的沙门氏菌属(鼠伤寒沙门氏菌及肠炎沙门氏菌)的5套PCR体系及大肠杆菌O157:H7的6套PCR体系进行比较分析,结果筛选出2套最优体系。基于这两套体系以及本实验室研究人员建立的单增李斯特菌的特异性检测方法,对从杭州市场上采集的50份常温鲜猪肉及150份冷鲜猪肉中单增李斯特菌、沙门氏菌及大肠杆菌O157:H7的污染状况进行调查。调查结果显示,200份样品中致病菌总检出率为21%。冷鲜猪肉中的致病菌检出率(24.7%)明显高于常温鲜猪肉(10%)。单增李斯特菌在常温鲜猪肉中的检出率为2%,而在冷鲜猪肉中检出率达14.7%;沙门氏菌在冷鲜猪肉中的检出率(11.3%)亦高于常温鲜猪肉(8.0%);大肠杆菌O157:H7均未检出。在检出的沙门氏菌中,有4株为鼠伤寒沙门氏菌,均来自冷鲜猪肉。本研究结果提示,市场上冷鲜猪肉存在微生物性安全隐患,这可能是由于其较为复杂的生产流通环节受到污染所致。     

聚合酶链式反应-变性高效液相色谱法检测5种食源性致病菌

目的建立聚合酶链式反应与变性高效液相色谱(polymerase chain reaction-denaturing high-performanceliquid chromatography,PCR-DHPLC)相结合的方法,快速检测5种食源性致病菌(沙门菌、副溶血性弧菌、福氏志贺菌、大肠埃希菌O157∶H7和单核细胞增生李斯特菌)。方法针对16S rRNA基因保守区设计引物,PCR扩增产物用变性高效液相色谱仪检测,并进行敏感性、特异性、检出率等指标测定。结果柱温61.4℃时,5种致病菌PCR产物分别呈现特异DHPLC色谱图,保留时间均为7min左右。对沙门菌、副溶血性弧菌和单核细胞增生李斯特菌检出限均为5～10CFU/ml,福氏志贺菌和大肠埃希菌O157∶H7均为1～5CFU/ml。对83株目的分离株的检出符合率为100%,38株非目的分离株检测均为阴性;对人工污染食品中的5种致病菌均可正确检出。结论该PCR-DHPLC方法具有较高的敏感性和特异性,可用于食品中5种食源性致病菌的高通量快速检测。     

多重PCR法检测鲜切哈密瓜中3种食源性致病菌

建立可同时检测鲜切哈密瓜中的单增李斯特菌、鼠伤寒沙门氏菌和大肠杆菌O157:H7的多重聚合酶链式反应(polymerase chain reaction,PCR)检测方法。根据单增李斯特菌inl A基因、鼠伤寒沙门氏菌inv A基因、大肠杆菌O157:H7的wzy基因设计3对特异性引物。对多重PCR反应体系中的引物浓度、退火温度、Mg2+浓度、d NTP浓度进行了优化,并确定适宜的多重PCR反应体系及反应条件。结果表明:25μL反应体系,10×PCR buffer为2.5μL,Mg Cl2(25 mmol/L)为3.5μL,d NTPs(2.5 mmol/L)为2μL,inl A基因上下游引物(5μmol/L)为1μL,inv A基因上下游引物(5μmol/L)为1μL,wzy基因上下游引物(5μmol/L)为2μL,单增李斯特菌DNA模板为1μL,鼠伤寒沙门氏菌DNA模板为1μL,大肠杆菌O157:H7 DNA模板为1μL,ex Taq DNA聚合酶(5 U/L)为0.3μL,加dd H2O补足25μL。反应条件为95℃预变性3 min;94℃变性30 s,53.9℃退火30 s,72℃延伸30 s,32个循环;72℃延伸10 min。鲜切哈密瓜中人工接种的目标菌的灵敏度为单增李斯特菌2.7×104 CFU/g,大肠杆菌O157:H7 3.3×104 CFU/g以及鼠伤寒沙门氏菌3.8×104 CFU/g。该技术可为快速检测鲜切哈密瓜中病原菌污染度及其控制提供参考依据。     

Optimization of rapid detection of Escherichia coli O157:H7 and Listeria monocytogenes by PCR and application to field test

For rapid detection of Escherichia coli O157:H7 and Listeria monocytogenes, simple methods for sample preparation and PCR were established and applied to a field test. To improve specificity, primer sets LP43-LP44 and C(+)-D(-) were selected for E. coli O157:H7 and L. monocytogenes, respectively. Through centrifugation and partial heat treatment after enrichment, E. coli O157:H7 and L. monocytogenes were detected at 1 initial CFU without genomic DNA extraction in the culture and with artificially inoculated food samples including milk, chicken, ham, and pork. Based on the optimized PCR method, a feasibility test was carried out using randomly collected field samples. To remove false positives and false negatives, a PCR method using several primer sets, including the optimized primer set, and a standard culture method were used. With the PCR detection and standard culture methods, two pork samples were positive for L. monocytogenes after enrichment, indications that the PCR assay could be effectively used for rapid, sensitive, and species-specific detection of foodborne pathogens.     

用寡核苷酸微阵列芯片方法检测常见的食源性致病微生物

研制了1种高通量检测食品中常见致病微生物的寡核苷酸微阵列芯片。该芯片在种的水平可鉴别金黄色葡萄球菌、阪崎肠杆菌、肠出血性大肠埃希氏菌O157:H7、霍乱弧茵、空肠弯曲杆菌、大肠弯曲杆菌、单核细胞增生李斯特菌、乙型洛血型链球菌和副溶血性弧菌;在属的水平可鉴别弯曲肠杆菌属、沙门氏菌属和李斯特氏菌属。研究中利用16S rDNA和沙门氏菌、O157:H7和副溶血性弧菌的特异基因序列设计引物和探针。用参比菌株和实验室自分离的菌株检测该芯片的特异性,结果表明该芯片的特异性良好,在所检测的菌株之间无交叉反应,与同属的其他菌株之间也不存在交叉反应。在鲜活海产品的24 h增菌液中添加参比菌株,当样品增菌液中的目的菌的量达到10~6～10~7 CFU/mL时,芯片可以准确检测出目的菌。     

多重PCR同时检测食品中4 种细菌与常见霉菌

建立一种同时检测食品中金黄色葡萄球菌、单核细胞增生李斯特氏菌、沙门氏菌、大肠杆菌O157:H7以及霉菌的多重聚合酶链式反应（polymerase chain reaction,PCR）检测方法。根据金黄色葡萄球菌的耐热核酸酶基因（nuc）、沙门氏菌的侵袭正调节蛋白基因（hilA）、大肠杆菌O157:H7鞭毛基因（flic）、单核细胞增生李斯特氏菌的毒力调控蛋白基因（prfA）及霉菌18S?rRNA基因V5区分别设计5?对特异性引物,并对PCR扩增反应体系和扩增条件进行优化,确定获得特异性良好的PCR扩增产物。而后在37?℃对人工污染致病菌的香肠、面包和豆腐进行增菌培养,5?种致病微生物在20?h内的检出限均可达到100?CFU/25?g。本实验建立的多重PCR检测方法适用于食品中4?种细菌与常见霉菌的同时检测,相较于传统检测方法,具有快速、简便、特异性高的优点。     

原料乳中多种致病菌的快速过滤富集及多重PCR检测

针对目前原料乳中致病菌的检测方法繁琐费时耗力的缺点,建立一种能同时检测原料乳中多种致病菌的快速检测方法,采用多重PCR快速灵敏检测技术与一种不需要预增菌就可以直接从原料乳中快速过滤富集菌体的技术相结合来同时检测原料乳中主要致病菌——沙门氏菌、大肠杆菌O157:H7、金黄色葡萄球菌、单增李斯特氏菌和蜡样芽孢杆菌。整个过程只需7～8h即可完成,且检测灵敏度可达102cfu/mL。这种方法是对传统检测方法的有效改进,并且达到了原料乳检测快速、准确、灵敏的要求。     

Application of a multiplex PCR for the simultaneous detection of Escherichia coli O157:H7, Salmonella and Shigella in raw and ready-to-eat meat products

Escherichia coli O157:H7, Salmonella and Shigella might contaminate similar types of meat products and cause deadly diseases in humans. Traditional microbiological analyses to detect these pathogens are labor-intensive and time-consuming. The objective of this study was to apply a multiplex PCR for simultaneous detection of the pathogenic bacteria in certain raw and ready-to-eat meat matrices. The tested samples had aerobic plate counts ranging from non-detectable, in chicken nuggets and salami, to 8.36log(10)CFU/g in ground pork. The pH of homogenates spanned from 6.86, in ground beef, to 7.17 in salami. Following a 24-h enrichment, the multiplex PCR assay could concurrently detect the three pathogens at 0.2log(10)CFU/g in ground beef, roast beef, beef frankfurters, chicken nuggets, salami and turkey ham, and 1.2log(10)CFU/g in ground pork. This multiplex PCR offers an efficient microbiological tool for presumptive detection of E. coli O157:H7, Salmonella and Shigella in meat.     

Rapid and simultaneous quantitation of Escherichia coli 0157:H7, Salmonella, and Shigella in ground beef by multiplex real-time PCR and immunomagnetic separation

The objective of this study was to establish a multiplex real-time PCR for the simultaneous quantitation of Escherichia coli O157:H7, Salmonella, and Shigella. Genomic DNA for the real-time PCR was extracted by the boiling method. Three sets of primers and corresponding TaqMan probes were designed to target these three pathogenic bacteria. Multiplex real-time PCR was performed with TaqMan Universal PCR Master Mix in an ABI Prism 7700 Sequence Detection System. Final standard curves were calculated for each pathogen by plotting the threshold cycle value against the bacterial number (log CFU per milliliter) via linear regression. With optimized conditions, the quantitative detection range of the real-time multiplex PCR for pure cultures was 10(2) to 10(9) CFU/ml for E. coli O157:H7, 10(3) to 10(9) CFU/ml for Salmonella, and 10(1) to 10(8) CFU/ml for Shigella. When the established multiplex real-time PCR system was applied to artificially contaminated ground beef, the detection limit was 10(5) CFU/g for E. coli O157:H7, 10(3) CFU/g for Salmonella, and 10(4) CFU/g for Shigella. Immunomagnetic separation (IMS) was further used to separate E. coli O157:H7 and Salmonella from the beef samples. With the additional use of IMS, the detection limit was 10(3) CFU/g for both pathogens. Results from this study showed that TaqMan real-time PCR, combined with IMS, is potentially an effective method for the rapid and reliable quantitation of E. coli 0157:H7, Salmonella, and Shigella in food.     

Validation of Dry Cured Ham Process for Control of Pathogens

ABSTRACT: The dry curing process for hams to control Salmonella spp., Escherichia coli O157:H7, Listeria monocytogenes , and Staphylococcus aureus was evaluated. Fresh hams, surface inoculated with each microorganism, were processed by a commercial style process. There was no significant (p < 0.05) difference in reduction of microbial populations between ham sampling locations (cushion, butt, hock). Interaction of salt concentration (8%), pH (5.5), ham storage temperature (20 °C), and ham aw (0.92) limited staphylococcal proliferation. Mean log reduction of Salmonella spp., E. coli O157:H7 and L. monocytogenes populations on inoculated hams after 69 d of curing were 5.5, 5.5, and 4.0 CFU/cm², respectively and after 120 d were 5.7, 5.5, and 4.8 CFU/cm², respectively. Keywords: dry cured ham, Salmonella, Esherichia coli O157:H7, Listeria monocytogenes, Staphylococcus aureus     

Growth of Escherichia coli O157:H7, Salmonella typhimurium DT104, and Listeria monocytogenes in dark cutting beef at 10 or 22 degrees C.

An experiment was conducted to determine the effects of the dark, firm, and dry (DFD) condition of beef on growth of the foodborne pathogens Escherichia coli O157:H7, Salmonella Typhimurium DT104, and Listeria monocytogenes Scott A in ground beef. Longissimus muscles from a DFD carcass (pH = 6.45) and normal carcass (N; pH = 5.64) were ground and samples obtained (100 and 0% DFD, respectively). Equal amounts of the 0 and 100% DFD ground samples were mixed to obtain 50% DFD samples. Inoculated 0, 50, and 100% DFD samples were packaged into oxygen-permeable overwrap and stored at 10 degrees C for E. coli O157:H7, Salmonella Typhimurium DT104, and L. monocytogenes Scott A or at 22 degrees C for E. coli O157:H7. Growth characteristics of E. coli O157:H7, Salmonella Typhimurium DT104, and L. monocytogenes Scott A did not differ (P > 0.05) between 0 and 100% DFD. Results indicated that the DFD beef used in this study was no more susceptible to growth of E. coli O157:H7, Salmonella Typhimurium, or L. monocytogenes Scott A than N beef.     

Simultaneous detection of Escherichia coli O157:H7, Listeria monocytogenes and Salmonella strains by real-time PCR

A protocol enabling simultaneous detection of Escherichia coli O157:H7, Listeria monocytogenes and Salmonella strains was devised and evaluated using artificially contaminated fresh produce. Association of Official Analytical Chemists (AOAC)-approved polymerase chain reaction (PCR) detection methods for three human pathogens were modified to enable simultaneous and real-time detection with high throughput capability. The method includes a melting-curve analysis of PCR products, which serves as confirmatory test. The modified protocol successfully detected all three pathogens when fresh produce was washed with artificially contaminated water containing E. coli O157:H7 and S. typhimurium down to the predicted level of 1 to 10 cells/ml and L. monocytogenes at 1000 cells/ml. The ability to monitor several pathogens simultaneously will save time and increase our ability to assure food safety.