Viable but Nonculturable Escherichia coli O157:H7 and Salmonella enterica in Fresh Produce: Rapid Determination by Loop-Mediated Isothermal Amplification Coupled with a Propidium Monoazide Treatment

ABSTRACT Escherichia coli O157:H7 and Salmonella enterica are leading causes of foodborne outbreaks linked to fresh produce. Both species can enter the “viable but nonculturable” (VBNC) state that precludes detection using conventional culture-based or molecular methods. In this study, we assessed propidium monoazide-quantitative PCR (PMA-qPCR) assays and novel methods combining PMA and loop-mediated isothermal amplification (LAMP) for the detection and quantification of VBNC E. coli O157:H7 and S. enterica in fresh produce. The performance of PMA-LAMP assays targeting the wzy gene of E. coli O157:H7 and the agfA gene of S. enterica and the performance of PMA-qPCR assays were compared in pure culture and spiked tomato, lettuce, and spinach. No cross-reaction was observed in the specificity tests. The values representing the limit of detection (LOD) seen with PMA-LAMP were 9.0 CFU/reaction for E. coli O157:H7 and 4.6 CFU/reaction for S. enterica in pure culture and were 5.13 × 103 or 5.13 × 104 CFU/g for VBNC E. coli O157:H7 and 1.05 × 104 or 1.05 × 105 CFU/g for VBNC S. enterica in fresh produce, representing results comparable to those obtained by PMA-qPCR. Standard curves showed correlation coefficients ranging from 0.925 to 0.996, indicating a good quantitative capacity of PMA-LAMP for determining populations of both bacterial species in the VBNC state. The PMA-LAMP assay was completed with considerable economy of time (30 min versus 1 h) and achieved sensitivity and quantitative capacity comparable to those seen with a PMA-qPCR assay. PMA-LAMP is a rapid, sensitive, and robust method for the detection and quantification of VBNC E. coli O157:H7 and S. enterica in fresh produce. IMPORTANCE VBNC pathogenic bacteria pose a potential risk to the food industry because they do not multiply on routine microbiological media and thus can evade detection in conventional plating assays. Both E. coli O157:H7 and S. enterica have been reported to enter the VBNC state under a range of environmental stress conditions and to resuscitate under favorable conditions and are a potential cause of human infections. PMA-LAMP methods developed in this study provide a rapid, sensitive, and specific way to determine levels of VBNC E. coli O157:H7 and S. enterica in fresh produce, which potentially decreases the risks related to the consumption of fresh produce contaminated by enteric pathogens in this state. PMA-LAMP can be further applied in the field study to enhance our understanding of the fate of VBNC pathogens in the preharvest and postharvest stages of fresh produce.

Download Full-text

Induction of Viable but Nonculturable Escherichia coli O157:H7 in the Phyllosphere of Lettuce: a Food Safety Risk Factor

Applied and Environmental Microbiology ◽

10.1128/aem.05020-11 ◽

2011 ◽

Vol 77 (23) ◽

pp. 8295-8302 ◽

Cited By ~ 81

Author(s):

Laura-Dorina Dinu ◽

Susan Bach

Keyword(s):

Escherichia Coli ◽

Food Safety ◽

Low Temperature ◽

Cell Density ◽

Prolonged Storage ◽

Potential Hazard ◽

Vbnc State ◽

Viable But Nonculturable ◽

Content Type ◽

E Coli

ABSTRACTEscherichia coliO157:H7 continues to be an important human pathogen and has been increasingly linked to food-borne illness associated with fresh produce, particularly leafy greens. The aim of this work was to investigate the fate ofE. coliO157:H7 on the phyllosphere of lettuce under low temperature and to evaluate the potential hazard of viable but nonculturable (VBNC) cells induced under such stressful conditions. First, we studied the survival of six bacterial strains following prolonged storage in water at low temperature (4°C) and selected two strains with different nonculturable responses for the construction ofE. coliO157:H7 Tn7gfptransformants in order to quantitatively assess the occurrence of human pathogens on the plant surface. Under a suboptimal growth temperature (16°C), bothE. coliO157:H7 strains maintained culturability on lettuce leaves, but under more stressful conditions (8°C), the bacterial populations evolved toward the VBNC state. The strain-dependent nonculturable response was more evident in the experiments with different inoculum doses (109and 106E. coliO157:H7 bacteria per g of leaf) when strain BRMSID 188 lost culturability after 15 days and strain ATCC 43895 lost culturability within 7 days, regardless of the inoculum dose. However, the number of cells entering the VBNC state in high-cell-density inoculum (approximately 55%) was lower than in low-cell-density inoculum (approximately 70%). We recorded the presence of verotoxin for 3 days in samples that contained a VBNC population of 4 to 5 log10cells but did not detect culturable cells. These findings indicate thatE. coliO157:H7 VBNC cells are induced on lettuce plants, and this may have implications regarding food safety.

Download Full-text

Viable-but-NonculturableListeria monocytogenesandSalmonella entericaSerovar Thompson Induced by Chlorine Stress Remain Infectious

mBio ◽

10.1128/mbio.00540-18 ◽

2018 ◽

Vol 9 (2) ◽

pp. e00540-18 ◽

Cited By ~ 31

Author(s):

Callum J. Highmore ◽

Jennifer C. Warner ◽

Steve D. Rothwell ◽

Sandra A. Wilks ◽

C. William Keevil

Keyword(s):

Listeria Monocytogenes ◽

Caenorhabditis Elegans ◽

Life Span ◽

Fresh Produce ◽

Environmental Stresses ◽

Vbnc State ◽

Viable But Nonculturable ◽

Content Type ◽

Food Borne Pathogens ◽

Food Borne

ABSTRACTThe microbiological safety of fresh produce is monitored almost exclusively by culture-based detection methods. However, bacterial food-borne pathogens are known to enter a viable-but-nonculturable (VBNC) state in response to environmental stresses such as chlorine, which is commonly used for fresh produce decontamination. Here, complete VBNC induction of green fluorescent protein-taggedListeria monocytogenesandSalmonella entericaserovar Thompson was achieved by exposure to 12 and 3 ppm chlorine, respectively. The pathogens were subjected to chlorine washing following incubation on spinach leaves. Culture data revealed that total viableL. monocytogenesandSalmonellaThompson populations became VBNC by 50 and 100 ppm chlorine, respectively, while enumeration by direct viable counting found that chlorine caused a <1-log reduction in viability. The pathogenicity of chlorine-induced VBNCL. monocytogenesandSalmonellaThompson was assessed by usingCaenorhabditis elegans. Ingestion of VBNC pathogens byC. elegansresulted in a significant life span reduction (P= 0.0064 andP< 0.0001), and no significant difference between the life span reductions caused by the VBNC and culturableL. monocytogenestreatments was observed.L. monocytogeneswas visualized beyond the nematode intestinal lumen, indicating resuscitation and cell invasion. These data emphasize the risk that VBNC food-borne pathogens could pose to public health should they continue to go undetected.IMPORTANCEMany bacteria are known to enter a viable-but-nonculturable (VBNC) state in response to environmental stresses. VBNC cells cannot be detected by standard laboratory culture techniques, presenting a problem for the food industry, which uses these techniques to detect pathogen contaminants. This study found that chlorine, a sanitizer commonly used for fresh produce, induces a VBNC state in the food-borne pathogensListeria monocytogenesandSalmonella enterica. It was also found that chlorine is ineffective at killing total populations of the pathogens. A life span reduction was observed inCaenorhabditis elegansthat ingested these VBNC pathogens, with VBNCL. monocytogenesas infectious as its culturable counterpart. These data show that VBNC food-borne pathogens can both be generated and avoid detection by industrial practices while potentially retaining the ability to cause disease.

Download Full-text

New Insights into the Formation of Viable but Nonculturable Escherichia coli O157:H7 Induced by High-Pressure CO 2

mBio ◽

10.1128/mbio.00961-16 ◽

2016 ◽

Vol 7 (4) ◽

Cited By ~ 32

Author(s):

Feng Zhao ◽

Yongtao Wang ◽

Haoran An ◽

Yanling Hao ◽

Xiaosong Hu ◽

...

Keyword(s):

Escherichia Coli ◽

High Pressure ◽

Cell Division ◽

State Formation ◽

Metabolic Activity ◽

Rna Seq ◽

Vbnc State ◽

Viable But Nonculturable ◽

E Coli ◽

State Entry

ABSTRACT The formation of viable but nonculturable (VBNC) Escherichia coli O157:H7 induced by high-pressure CO 2 (HPCD) was investigated using RNA sequencing (RNA-Seq) transcriptomics and isobaric tag for relative and absolute quantitation (iTRAQ) proteomic methods. The analyses revealed that 97 genes and 56 proteins were significantly changed upon VBNC state entry. Genes and proteins related to membrane transport, central metabolisms, DNA replication, and cell division were mainly downregulated in the VBNC cells. This caused low metabolic activity concurrently with a division arrest in cells, which may be related to VBNC state formation. Cell division repression and outer membrane overexpression were confirmed to be involved in VBNC state formation by homologous expression of z2046 coding for transcriptional repressor and ompF encoding outer membrane protein F. Upon VBNC state entry, pyruvate catabolism in the cells shifted from the tricarboxylic acid (TCA) cycle toward the fermentative route; this led to a low level of ATP. Combating the low energy supply, ATP production in the VBNC cells was compensated by the degradation of l -serine and l -threonine, the increased AMP generation, and the enhanced electron transfer. Furthermore, tolerance of the cells with respect to HPCD-induced acid, oxidation, and high CO 2 stresses was enhanced by promoting the production of ammonia and NADPH and by reducing CO 2 production during VBNC state formation. Most genes and proteins related to pathogenicity were downregulated in the VBNC cells. This would decrease the cell pathogenicity, which was confirmed by adhesion assays. In conclusion, the decreased metabolic activity, repressed cell division, and enhanced survival ability in E. coli O157:H7 might cause HPCD-induced VBNC state formation. IMPORTANCE Escherichia coli O157:H7 has been implicated in large foodborne outbreaks worldwide. It has been reported that the presence of as few as 10 cells in food could cause illness. However, the presence of only 0.73 to 1.5 culturable E. coli O157:H7 cells in salted salmon roe caused infection in Japan. Investigators found that E. coli O157:H7 in the viable but nonculturable (VBNC) state was the source of the outbreak. So far, formation mechanisms of VBNC state are not well known. In a previous study, we demonstrated that high-pressure CO 2 (HPCD) could induce the transition of E. coli O157:H7 into the VBNC state. In this study, we used RNA-Seq transcriptomic analysis combined with the iTRAQ proteomic method to investigate the formation of VBNC E. coli O157:H7 induced by HPCD treatment. Finally, we proposed a putative formation mechanism of the VBNC cells induced by HPCD, which may provide a theoretical foundation for controlling the VBNC state entry induced by HPCD treatment.

Download Full-text

Prevalence and Genomic Characterization of Escherichia coli O157:H7 in Cow-Calf Herds throughout California

Applied and Environmental Microbiology ◽

10.1128/aem.00734-17 ◽

2017 ◽

Vol 83 (16) ◽

Cited By ~ 6

Author(s):

Jay N. Worley ◽

Kristopher A. Flores ◽

Xun Yang ◽

Jennifer A. Chase ◽

Guojie Cao ◽

...

Keyword(s):

Escherichia Coli ◽

Large Scale ◽

Fresh Produce ◽

Bacterial Pathogen ◽

Virulence Gene ◽

The United States ◽

Pathogenic Potential ◽

Content Type ◽

E Coli ◽

Cow Calf

ABSTRACT Escherichia coli serotype O157:H7 is a zoonotic food- and waterborne bacterial pathogen that causes a high hospitalization rate and can cause life-threatening complications. Increasingly, E. coli O157:H7 infections appear to originate from fresh produce. Ruminants, such as cattle, are a prominent reservoir of E. coli O157:H7 in the United States. California is one of the most agriculturally productive regions in the world for fresh produce, beef, and milk. The close proximity of fresh produce and cattle presents food safety challenges on a uniquely large scale. We performed a survey of E. coli O157:H7 on 20 farms in California to observe the regional diversity and prevalence of E. coli O157:H7. Isolates were obtained from enrichment cultures of cow feces. Some farms were sampled on two dates. Genomes from isolates were sequenced to determine their relatedness and pathogenic potential. E. coli O157:H7 was isolated from approximately half of the farms. The point prevalence of E. coli O157:H7 on farms was highly variable, ranging from zero to nearly 90%. Within farms, generally one or a few lineages were found, even when the rate of isolation was high. On farms with high isolation rates, a single clonal lineage accounted for most of the isolates. Farms that were visited months after the first visit might have had the same lineages of E. coli O157:H7. Strains of E. coli O157:H7 may be persistent for months on farms. IMPORTANCE This survey of 20 cow-calf operations from different regions of California provides an in depth look at resident Escherichia coli O157:H7 populations at the molecular level. E. coli O157:H7 is found to have a highly variable prevalence, and with whole-genome sequencing, high prevalences in herds were found to be due to a single lineage shed from multiple cows. Few repeat lineages were found between farms in this area; therefore, we predict that E. coli O157:H7 has significant diversity in this area beyond what is detected in this survey. All isolates from this study were found to have pathogenic potential based on the presence of key virulence gene sequences. This represents a novel insight into pathogen diversity within a single subtype and will inform future attempts to survey regional pathogen populations.

Download Full-text

Rapid and Specific Detection of Escherichia coli Serogroups O26, O45, O103, O111, O121, O145, and O157 in Ground Beef, Beef Trim, and Produce by Loop-Mediated Isothermal Amplification

Applied and Environmental Microbiology ◽

10.1128/aem.07975-11 ◽

2012 ◽

Vol 78 (8) ◽

pp. 2727-2736 ◽

Cited By ~ 52

Author(s):

Fei Wang ◽

Lin Jiang ◽

Qianru Yang ◽

Witoon Prinyawiwatkul ◽

Beilei Ge

Keyword(s):

Escherichia Coli ◽

Pure Culture ◽

False Negative ◽

Ground Beef ◽

The United States ◽

Food Samples ◽

Isothermal Amplification ◽

Specific Detection ◽

Content Type ◽

Loop Mediated Isothermal Amplification

ABSTRACTEscherichia coliO157 and six additional serogroups of Shiga toxin-producingE. coli(STEC) (O26, O45, O103, O111, O121, and O145) account for the majority of STEC infections in the United States. In this study, O serogroup-specific genes (wzxorwzy) were used to design loop-mediated isothermal amplification (LAMP) assays for the rapid and specific detection of these leading STEC serogroups. The assays were evaluated in pure culture and spiked food samples (ground beef, beef trim, lettuce, and spinach) and compared with real-time quantitative PCR (qPCR). No false-positive or false-negative results were observed among 120 bacterial strains used to evaluate assay specificity. The limits of detection of various STEC strains belonging to these target serogroups were approximately 1 to 20 CFU/reaction mixture in pure culture and 103to 104CFU/g in spiked food samples, which were comparable to those of qPCR. Standard curves generated suggested good linear relationships between STEC cell numbers and LAMP turbidity signals. In various beef and produce samples spiked with two low levels (1 to 2 and 10 to 20 CFU/25 g) of respective STEC strains, the LAMP assays consistently achieved accurate detection after 6 to 8 h of enrichment. In conclusion, these newly developed LAMP assays may facilitate rapid and reliable detection of the seven major STEC serogroups in ground beef, beef trim, and produce during routine sample testing.

Download Full-text

Rapid Detection of Viable Salmonellae in Produce by Coupling Propidium Monoazide with Loop-Mediated Isothermal Amplification

Applied and Environmental Microbiology ◽

10.1128/aem.00354-11 ◽

2011 ◽

Vol 77 (12) ◽

pp. 4008-4016 ◽

Cited By ~ 111

Author(s):

Siyi Chen ◽

Fei Wang ◽

John C. Beaulieu ◽

Rebecca E. Stein ◽

Beilei Ge

Keyword(s):

Pure Culture ◽

Rapid Detection ◽

Lamp Assay ◽

Isothermal Amplification ◽

Detection Methods ◽

Sample Treatment ◽

Propidium Monoazide ◽

Simple Method ◽

Content Type ◽

Loop Mediated Isothermal Amplification

ABSTRACTRecent outbreaks linked toSalmonella-contaminated produce heightened the need to develop simple, rapid, and accurate detection methods, particularly those capable of determining cell viability. In this study, we examined a novel strategy for the rapid detection and quantification of viable salmonellae in produce by coupling a simple propidium monoazide sample treatment with loop-mediated isothermal amplification (PMA-LAMP). We first designed and optimized a LAMP assay targetingSalmonella. Second, the performance of PMA-LAMP for detecting and quantifying viable salmonellae was determined. Finally, the assay was evaluated in experimentally contaminated produce items (cantaloupe, spinach, and tomato). Under the optimized condition, PMA-LAMP consistently gave negative results for heat-killedSalmonellacells with concentrations up to 108CFU/ml (or CFU/g in produce). The detection limits of PMA-LAMP were 3.4 to 34 viableSalmonellacells in pure culture and 6.1 × 103to 6.1 × 104CFU/g in spiked produce samples. In comparison, PMA-PCR was up to 100-fold less sensitive. The correlation between LAMP time threshold (TT) values and viableSalmonellacell numbers was high (R2= 0.949 to 0.993), with a quantification range (102to 105CFU/reaction in pure culture and 104to 107CFU/g in produce) comparable to that of PMA in combination with quantitative real-time PCR (PMA-qPCR). The complete PMA-LAMP assay took about 3 h to complete when testing produce samples. In conclusion, this rapid, accurate, and simple method to detect and quantify viableSalmonellacells in produce may present a useful tool for the produce industry to better control potential microbial hazards in produce.

Download Full-text

Importance of Pyruvate Sensing and Transport for the Resuscitation of Viable but NonculturableEscherichia coliK-12

Journal of Bacteriology ◽

10.1128/jb.00610-18 ◽

2018 ◽

Vol 201 (3) ◽

Cited By ~ 8

Author(s):

Cláudia Vilhena ◽

Eugen Kaganovitch ◽

Alexander Grünberger ◽

Magdalena Motz ◽

Ignasi Forné ◽

...

Keyword(s):

Response Regulator ◽

Bacterial Species ◽

Microfluidic System ◽

Vbnc State ◽

Viable But Nonculturable ◽

Content Type ◽

E Coli ◽

High Affinity ◽

Vbnc Bacteria ◽

K 12

ABSTRACTEscherichia coliand many other bacterial species can enter into a viable but nonculturable (VBNC) state, which is a survival strategy adopted by cells exposed to adverse environmental conditions. Pyruvate is known to be one factor that promotes resuscitation of VBNC cells. Here we studied the role of a pyruvate-sensing network, composed of the histidine kinase-response regulator systems BtsS/BtsR and YpdA/YpdB and the target genebtsT, encoding the high-affinity pyruvate/H+symporter BtsT, in the resuscitation of VBNCE. coliK-12 cells after exposure to cold for 120 days. Analysis of the proteome of VBNC cells revealed upregulation, relative to exponentially growing cells, of BtsT and other proteins involved in pyruvate metabolism. Provision of pyruvate stimulated protein and DNA biosynthesis, and thus resuscitation, in wild-type but notbtsSR ypdABmutant VBNC cells. This result was corroborated by time-dependent tracking of the resuscitation of individual VBNCE. colicells observed in a microfluidic system. Finally, transport assays revealed that14C-labeled pyruvate was rapidly taken up into VBNC cells by BtsT. These results provide the first evidence that pyruvate is taken up as a carbon source for the resuscitation of VBNCE. colicells.IMPORTANCEViable but nonculturable (VBNC) bacteria do not form colonies in standard medium but otherwise retain their metabolic activity and can express toxic proteins. Many bacterial genera, includingEscherichia,Vibrio, andListeria, have been shown to enter the VBNC state upon exposure to adverse conditions, such as low temperature, radiation, and starvation. Ultimately, these organisms pose a public health risk with potential implications for the pharmaceutical and food industries, as dormant organisms are especially difficult to selectively eliminate and VBNC bacteria can be resuscitated if placed in an environment with appropriate nutrition and temperature. Here we used a microfluidic system to monitor the resuscitation of single VBNC cells over time. We provide new molecular insights into the initiation of resuscitation by demonstrating that VBNCE. colicells rapidly take up pyruvate with an inducible high-affinity transporter, whose expression is triggered by the BtsSR-YpdAB sensing network.

Download Full-text

Functional Analysis ofycfRandycfQin Escherichia coli O157:H7 Linked to Outbreaks of Illness Associated with Fresh Produce

Applied and Environmental Microbiology ◽

10.1128/aem.02420-10 ◽

2011 ◽

Vol 77 (12) ◽

pp. 3952-3959 ◽

Cited By ~ 20

Author(s):

Kaiping Deng ◽

Siyun Wang ◽

Xiaoqian Rui ◽

Wei Zhang ◽

Mary Lou Tortorello

Keyword(s):

Escherichia Coli ◽

Fresh Produce ◽

The United States ◽

Sublethal Concentration ◽

Wild Type ◽

Chloramphenicol Resistance ◽

Content Type ◽

E Coli ◽

K 12 ◽

Postharvest Processing

ABSTRACTFresh produce has been associated with multiple outbreaks of illness caused byEscherichia coliO157:H7. The mechanism ofE. coliO157:H7 survival through postharvest processing of fresh produce needs to be understood to help develop more effective interventions. In our recent transcriptomic study of strain Sakai, an isolate from the 1996 sprout outbreak in Japan, and strain TW14359, an isolate from the 2006 spinach outbreak in the United States, we showed thatycfRwas the most significantly upregulated gene in response to chlorine-based oxidative stress. YcfR is known to be a multiple stress resistance protein and a biofilm regulator inE. coliK-12 strains; however, its role in the pathogenicE. coliO157:H7 has not been clearly defined. In this study,ycfRwas replaced with a chloramphenicol resistance cassette oriented in two different directions to construct polar and nonpolarycfR::catmutants of Sakai and TW14359. Chlorine resistance and survival on spinach leaf surfaces were assessed in the wild-type strains and theycfRmutants. Both polar and nonpolarycfRmutants of Sakai showed significantly less chlorine resistance than their parent strain. In contrast, deletion ofycfRin TW14359 did not change chlorine resistance, indicating thatycfRin these two outbreak-relatedE. coliO157:H7 strains may function differently. In addition, after a 24-h incubation on spinach leaves in a sublethal concentration of chlorine, the Sakai nonpolarycfRmutant exhibited lower survival compared to the wild type. The results suggest a role forycfRin survival of Sakai during chlorine exposure. We also found that the upstreamycfQ, which is annotated as a DNA-binding regulator, acted as a repressor ofycfR. These findings suggest that gene regulation may be a mechanism by whichE. coliO157:H7 strain Sakai could survive in the postharvest processing environment.

Download Full-text

Microbial growth and attachment of Salmonella and enterohemorrhagic and enteroaggregative Escherichia coli strains on cress microgreens grown in peat soil system

British Food Journal ◽

10.1108/bfj-03-2021-0269 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Sahin Namli ◽

Hilal Samut ◽

Yesim Soyer

Keyword(s):

Escherichia Coli ◽

Irrigation Water ◽

Biofilm Formation ◽

Peat Soil ◽

Fresh Produce ◽

Bacterial Load ◽

Soil System ◽

Content Type ◽

E Coli ◽

Significant Difference

PurposeThis study aimed to investigate how enteric pathogens and their biofilm populations on fresh produce survive according to time that contamination has occurred on leaves and contamination route: seed irrigation water.Design/methodology/approachCress was contaminated in two different ways: contamination of seeds and irrigation water with 8-log MPN/mL bacterial load, Salmonella Newport, Escherichia coli O157:H7, O104:H4 or O78:H2. While contaminated seeds were cultivated for seed contamination, contaminated irrigation was applied at the end of each week to separate groups of samples obtained from cultivated surface-sterile seeds to understand how long these pathogens could survive until harvest.FindingsThe results indicated these pathogens survived until harvest, and formed biofilms on cress leaves grown using both contaminated seeds and irrigation water. No significant difference was observed among populations of Salmonella and E. coli groups in terms of survival (∼4.5–6.0 log MPN/g) and biofilm formation (∼4.4–5.7 log MPN/g) for contamination by seed. Also, SEM images revealed biofilm-like structures, the proofs of the attachment of these pathogens on leaf surfaces.Originality/valueFrom our knowledge this is the first study focusing on the survival and biofilm formation of one Salmonella serotype (Newport) and three E. coli serotypes (O157:H7, O104:H4, and O78:H2), representing enterohemorrhagic and enteroaggregative E. coli pathogenic subgroups, under the same irrigation and growth schemes. Furthermore, this study mimics the contamination of seeds and irrigation water with sewage or wastewater and may shed light on contamination of fresh produce grown using poor wastewater treatment.

Download Full-text

Novel Microarray Design for Molecular Serotyping of Shiga Toxin-Producing Escherichia coli Strains Isolated from Fresh Produce

Applied and Environmental Microbiology ◽

10.1128/aem.01049-14 ◽

2014 ◽

Vol 80 (15) ◽

pp. 4677-4682 ◽

Cited By ~ 22

Author(s):

David W. Lacher ◽

Jayanthi Gangiredla ◽

Scott A. Jackson ◽

Christopher A. Elkins ◽

Peter C. H. Feng

Keyword(s):

Escherichia Coli ◽

Shiga Toxin ◽

Fresh Produce ◽

Content Type ◽

E Coli ◽

Efficacy Analysis ◽

Molecular Serotyping ◽

Large Numbers ◽

Complex Procedure ◽

Content Identification

ABSTRACTSerotypingEscherichia coliis a cumbersome and complex procedure due to the existence of large numbers of O- and H-antigen types. It can also be unreliable, as many Shiga toxin-producingE. coli(STEC) strains isolated from fresh produce cannot be typed by serology or have only partial serotypes. The FDAE. coliidentification (FDA-ECID) microarray, designed for characterizing pathogenicE. coli, contains a molecular serotyping component, which was evaluated here for its efficacy. Analysis of a panel of 75 referenceE. colistrains showed that the array correctly identified the O and H types in 97% and 98% of the strains, respectively. Comparative analysis of 73 produce STEC strains showed that serology and the array identified 37% and 50% of the O types, respectively, and that the array was able to identify 16 strains that could not be O serotyped. Furthermore, the array identified the H types of 97% of the produce STEC strains compared to 65% by serology, including six strains that were mistyped by serology. These results show that the array is an effective alternative to serology in serotyping environmentalE. coliisolates.

Download Full-text