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Reichelt B, Szott V, Stingl K, Roesler U, Friese A. Detection of Viable but Non-Culturable (VBNC)- Campylobacter in the Environment of Broiler Farms: Innovative Insights Delivered by Propidium Monoazide (PMA)-v-qPCR Analysis. Microorganisms 2023; 11:2492. [PMID: 37894150 PMCID: PMC10609165 DOI: 10.3390/microorganisms11102492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Revised: 09/30/2023] [Accepted: 10/03/2023] [Indexed: 10/29/2023] Open
Abstract
Campylobacteriosis cases in humans are of global concern, with high prevalence rates in the poultry reservoir considered the most important source of infection. Research findings show Campylobacters' ability to enter a viable but non-culturable (VBNC) state, remaining "viable" but unable to grow on culture media. We explored the persistence of VBNC states in specific environments, particularly at broiler farms, as this state may lead to an underestimation of the present Campylobacter prevalence. For VBNC detection, a propidium monoazide PMA-dye viability qPCR (v-qPCR) was used in combination with cultivation methods. We examined samples collected from broiler farm barns and their surroundings, as well as chicken manure from experimental pens. In addition, the tenacity of culturable and VBNC-Campylobacter was studied in vitro in soil and water. In a total of three visits, Campylobacter was not detected either culturally or by v-qPCR (no Campylobacter DNA) in the environment of the broiler farms. In four visits, however, VBNC-Campylobacter were detected both inside and outside the barns. The overall prevalence in environmental samples was 15.9% for VBNC-Campylobacter, 62.2% for Campylobacter DNA, and 1.2% for culturable C. jejuni. In the experimental pens, no cultivable C. jejuni was detected in chicken manure after 24 h. Strikingly, "VBNC-Campylobacter" persisted even after 72 h. "VBNC-Campylobacter" were confirmed in barn surroundings and naturally contaminated chicken manure. Laboratory studies revealed that VBNC-Campylobacter can remain intact in soil for up to 28 days and in water for at least 63 days, depending on environmental conditions.
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Affiliation(s)
- Benjamin Reichelt
- Institute for Animal Hygiene and Environmental Health, Freie Universität Berlin, 14163 Berlin, Germany; (B.R.)
| | - Vanessa Szott
- Institute of Food Safety and Food Hygiene, Freie Universität Berlin, 14163 Berlin, Germany;
| | - Kerstin Stingl
- Department of Biological Safety, German Federal Institute for Risk Assessment (BfR), 10589 Berlin, Germany
| | - Uwe Roesler
- Institute for Animal Hygiene and Environmental Health, Freie Universität Berlin, 14163 Berlin, Germany; (B.R.)
| | - Anika Friese
- Institute for Animal Hygiene and Environmental Health, Freie Universität Berlin, 14163 Berlin, Germany; (B.R.)
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Weber M, Göpfert B, von Wezyk S, Savin-Hoffmeyer M, Lipski A. Correlation between Bacterial Cell Density and Abundance of Antibiotic Resistance on Milking Machine Surfaces Assessed by Cultivation and Direct qPCR Methods. MICROBIAL ECOLOGY 2023; 86:1676-1685. [PMID: 37166501 PMCID: PMC10497690 DOI: 10.1007/s00248-023-02225-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 04/18/2023] [Indexed: 05/12/2023]
Abstract
The relative abundance of antibiotic-resistant bacteria and antibiotic-resistance genes was surveyed for different parts of a milking machine. A cultivation approach based on swab samples showed a highly diverse microbiota, harboring resistances against cloxacillin, ampicillin, penicillin, and tetracycline. This approach demonstrated a substantial cloxacillin resistance of numerous taxa within milking machine microbiota coming along with regular use of cloxacillin for dry-off therapy of dairy cows. For the less abundant tetracycline-resistant bacteria we found a positive correlation between microbial cell density and relative abundance of tetracycline-resistant microorganisms (R2 = 0.73). This indicated an accelerated dispersion of resistant cells for sampling locations with high cell density. However, the direct quantification of the tetM gene from the swap samples by qPCR showed the reverse relation to bacterial density if normalized against the abundance of 16S rRNA genes (R2 = 0.88). The abundance of 16S rRNA genes was analyzed by qPCR combined with a propidium monoazide treatment, which eliminates 16S rRNA gene signals in negative controls.
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Affiliation(s)
- Mareike Weber
- Institute of Nutrition and Food Sciences, Department of Food Microbiology and Hygiene, University of Bonn, Friedrich-Hirzebruch-Allee 7, 53115, Bonn, Germany
| | - Bettina Göpfert
- Institute of Nutrition and Food Sciences, Department of Food Microbiology and Hygiene, University of Bonn, Friedrich-Hirzebruch-Allee 7, 53115, Bonn, Germany
| | - Sina von Wezyk
- Institute of Nutrition and Food Sciences, Department of Food Microbiology and Hygiene, University of Bonn, Friedrich-Hirzebruch-Allee 7, 53115, Bonn, Germany
| | - Michael Savin-Hoffmeyer
- Institute for Hygiene and Public Health, University Hospital Bonn, Venusberg-Campus 1, 53127, Bonn, Germany
| | - André Lipski
- Institute of Nutrition and Food Sciences, Department of Food Microbiology and Hygiene, University of Bonn, Friedrich-Hirzebruch-Allee 7, 53115, Bonn, Germany.
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Santos LS, Rossi DA, Braz RF, Fonseca BB, Guidotti–Takeuchi M, Alves RN, Beletti ME, Almeida-Souza HO, Maia LP, Santos PDS, de Souza JB, de Melo RT. Roles of viable but non-culturable state in the survival of Campylobacter jejuni. Front Cell Infect Microbiol 2023; 13:1122450. [PMID: 37056707 PMCID: PMC10086134 DOI: 10.3389/fcimb.2023.1122450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Accepted: 03/09/2023] [Indexed: 03/30/2023] Open
Abstract
Despite being considered fragile and fastidious, Campylobacter jejuni is the most prevalent cause of foodborne bacterial gastroenteritis, and chicken meat is considered the main vehicle of transmission to humans. This agent can survive adverse conditions in the form of biofilms, but extreme stress (nutritional, oxidative and thermal) promotes the acquisition of a state called viable but not culturable (VBNC). The emergence of this pathogen worldwide and the recent international requirements in its control instigated us to qualitatively and quantitatively estimate the time required for the acquisition of the VBNC form in 27 strains of C. jejuni, characterize morphological aspects, determine its adaptive and invasive potential and perform comparative metabolomic evaluation. Extreme stress promoted the complete acquisition of the VBNC form in a mean time of 26 days. Starting from an average initial count of 7.8 log CFU/mL, the first four days determined the greatest average reduction of the culturable form of 3.2 log CFU/mL. The scanning and transmission image analyses showed a transition from the typical viable form (VT) to the VBNC form, with initial acquisition of the straight rod shape, followed by loss of the flagella and subdivision into two to 11 imperfect cocci arranged in a chain and rich in cellular content, until their individual release. RT-PCR identified the presence of ciaB and p19 transcripts in the 27 cultivable C. jejuni strains, a character maintained in the VBNC form only for p19 and in 59.3% (16/27) of the VBNC strains for the ciaB gene. The average inoculation of 1.8 log CFU/mL of C. jejuni VBNC into primary chicken embryo hepatocyte cells promoted the occurrence of apoptosis processes significantly after 24 hours of contact by one of the strains tested. In C. jejuni VBNC, we detected higher expression of metabolites linked to protective and adaptation mechanisms and of volatile organic precursor compounds indicative of metabolism interruption. The oscillations in the time of acquisition of the VBNC form together with the presence of transcripts for ciaB and p19, the identification of cell lysis and metabolites that ensure the maintenance of the pathogen alert to the fact that C. jejuni VBNC remains virulent and adapted to stress, which makes evident the potential danger of this latent form, which is not detectable by official methodologies.
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Affiliation(s)
- Leticia Silva Santos
- Laboratory of Molecular Epidemiology, Federal University of Uberlandia, Uberlandia, Brazil
| | - Daise Aparecida Rossi
- Laboratory of Molecular Epidemiology, Federal University of Uberlandia, Uberlandia, Brazil
| | | | | | | | | | | | | | - Larissa Prado Maia
- Biotechnology Institute, Federal University of Uberlandia, Uberlandia, Brazil
| | | | | | - Roberta Torres de Melo
- Laboratory of Molecular Epidemiology, Federal University of Uberlandia, Uberlandia, Brazil
- *Correspondence: Roberta Torres de Melo,
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Point-of-Care Lateral Flow Detection of Viable Escherichia coli O157:H7 Using an Improved Propidium Monoazide-Recombinase Polymerase Amplification Method. Foods 2022; 11:3207. [PMCID: PMC9602316 DOI: 10.3390/foods11203207] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The detection of both viable and viable but non-culturable (VBNC) Escherichia coli O157:H7 is a crucial part of food safety. Traditional culture-dependent methods are lengthy, expensive, laborious, and unable to detect VBNC. Hence, there is a need to develop a rapid, simple, and cost-effective detection method to differentiate between viable/dead E. coli O157:H7 and detect VBNC cells. In this work, recombinase polymerase amplification (RPA) was developed for the detection of viable E. coli O157:H7 through integration with propidium monoazide (PMAxx). Initially, two primer sets, targeting two different genes (rfbE and stx) were selected, and DNA amplification by RPA combined with PMAxx treatment and the lateral flow assay (LFA) was carried out. Subsequently, the rfbE gene target was found to be more effective in inhibiting the amplification from dead cells and detecting only viable E. coli O157:H7. The assay’s detection limit was found to be 102 CFU/mL for VBNC E. coli O157:H7 when applied to spiked commercial beverages including milk, apple juice, and drinking water. pH values from 3 to 11 showed no significant effect on the efficacy of the assay. The PMAxx-RPA-LFA was completed at 39 °C within 40 min. This study introduces a rapid, robust, reliable, and reproducible method for detecting viable bacterial counts. In conclusion, the optimised assay has the potential to be used by the food and beverage industry in quality assurance related to E. coli O157:H7.
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Sharan M, Vijay D, Dhaka P, Bedi JS, Gill JPS. Biofilms as a microbial hazard in the food industry: A scoping review. J Appl Microbiol 2022; 133:2210-2234. [PMID: 35945912 DOI: 10.1111/jam.15766] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 08/06/2022] [Indexed: 11/29/2022]
Abstract
Biofilms pose a serious public health hazard with a significant economic impact on the food industry. The present scoping review is designed to analyze the literature published during 2001-2020 on biofilm formation of microbes, their detection methods, and association with antimicrobial resistance (if any). The peer-reviewed articles retrieved from 04 electronic databases were assessed using PRISMA-ScR guidelines. From the 978 preliminary search results, a total of 88 publications were included in the study. On analysis, the commonly isolated pathogens were Listeria monocytogenes, Staphylococcus aureus, Salmonella spp., Escherichia coli, Bacillus spp., Vibrio spp., Campylobacter jejuni and Clostridium perfringens. The biofilm-forming ability of microbes was found to be influenced by various factors such as attachment surfaces, temperature, presence of other species, nutrient availability etc. A total of 18 studies characterized the biofilm-forming genes, particularly for S. aureus, Salmonella spp., and E. coli. In most studies, polystyrene plate and/or stainless-steel coupons were used for biofilm formation, and the detection was carried out by crystal violet assays and/or by plate counting method. The strain-specific significant differences in biofilm formation were observed in many studies, and few studies carried out analysis of multi-species biofilms. The association between biofilm formation and antimicrobial resistance wasn't clearly defined. Further, viable but non-culturable (VBNC) form of the foodborne pathogens is posing an unseen (by conventional cultivation techniques) but potent threat food safety. The present review recommends the need for carrying out systematic surveys and risk analysis of biofilms in food chain to highlight the evidence-based public health concerns, especially in regions where microbiological food hazards are quite prevalent.
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Affiliation(s)
- Manjeet Sharan
- Centre for One Health, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana, India
| | - Deepthi Vijay
- Centre for One Health, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana, India.,Present Address: Department of Veterinary Public Health, College of Veterinary and Animal Sciences, Kerala, India
| | - Pankaj Dhaka
- Centre for One Health, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana, India
| | - Jasbir Singh Bedi
- Centre for One Health, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana, India
| | - Jatinder Paul Singh Gill
- Centre for One Health, College of Veterinary Science, Guru Angad Dev Veterinary and Animal Sciences University, Ludhiana, India
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Stingl K, Heise J, Thieck M, Wulsten IF, Pacholewicz E, Iwobi AN, Govindaswamy J, Zeller-Péronnet V, Scheuring S, Luu HQ, Fridriksdottir V, Gölz G, Priller F, Gruntar I, Jorgensen F, Koene M, Kovac J, Lick S, Répérant E, Rohlfing A, Zawilak-Pawlik A, Rossow M, Schlierf A, Frost K, Simon K, Uhlig S, Huber I. Challenging the "gold standard" of colony-forming units - Validation of a multiplex real-time PCR for quantification of viable Campylobacter spp. in meat rinses. Int J Food Microbiol 2021; 359:109417. [PMID: 34624596 DOI: 10.1016/j.ijfoodmicro.2021.109417] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 08/01/2021] [Accepted: 09/18/2021] [Indexed: 11/26/2022]
Abstract
Campylobacter jejuni is the leading bacterial food-borne pathogen in Europe. Despite the accepted limits of cultural detection of the fastidious bacterium, the "gold standard" in food microbiology is still the determination of colony-forming units (CFU). As an alternative, a live/dead differentiating qPCR has been established, using propidium monoazide (PMA) as DNA-intercalating crosslink agent for inactivating DNA from dead, membrane-compromised cells. The PMA treatment was combined with the addition of an internal sample process control (ISPC), i.e. a known number of dead C. sputorum cells to the samples. The ISPC enables i), monitoring the effective reduction of dead cell signal by the light-activated DNA-intercalating dye PMA, and ii), compensation for potential DNA losses during processing. Here, we optimized the method for routine application and performed a full validation of the method according to ISO 16140-2:2016(E) for the quantification of live thermophilic Campylobacter spp. in meat rinses against the classical enumeration method ISO 10272-2:2017. In order to render the method applicable and cost-effective for practical application, the ISPC was lyophilized to be distributable to routine laboratories. In addition, a triplex qPCR was established to simultaneously quantify thermophilic Campylobacter, the ISPC and an internal amplification control (IAC). Its performance was statistically similar to the two duplex qPCRs up to a contamination level of 4.7 log10Campylobacter per ml of meat rinse. The limit of quantification (LOQ) of the alternative method was around 20 genomic equivalents per PCR reaction, i.e. 2.3 log10 live Campylobacter per ml of sample. The alternative method passed a relative trueness study, confirming the robustness against different meat rinses, and displayed sufficient accuracy within the limits set in ISO 16140-2:2016(E). Finally, the method was validated in an interlaboratory ring trial, confirming that the alternative method was fit for purpose with a tendency of improved repeatability and reproducibility compared to the reference method for CFU determination. Campylobacter served as a model organism, challenging CFU as "gold standard" and could help in guidance to the general acceptance of live/dead differentiating qPCR methods for the detection of food-borne pathogens.
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Affiliation(s)
- Kerstin Stingl
- German Federal Institute for Risk Assessment (BfR), Department of Biological Safety, National Reference Laboratory for Campylobacter, Berlin, Germany.
| | - Janine Heise
- German Federal Institute for Risk Assessment (BfR), Department of Biological Safety, National Reference Laboratory for Campylobacter, Berlin, Germany
| | - Maja Thieck
- German Federal Institute for Risk Assessment (BfR), Department of Biological Safety, National Reference Laboratory for Campylobacter, Berlin, Germany
| | - Imke F Wulsten
- German Federal Institute for Risk Assessment (BfR), Department of Biological Safety, National Reference Laboratory for Campylobacter, Berlin, Germany
| | - Ewa Pacholewicz
- German Federal Institute for Risk Assessment (BfR), Department of Biological Safety, National Reference Laboratory for Campylobacter, Berlin, Germany; Wageningen Bioveterinary Research, Lelystad, the Netherlands
| | - Azuka N Iwobi
- Bavarian Health and Food Safety Authority (LGL), Oberschleissheim, Germany
| | | | | | - Sandra Scheuring
- Bavarian Health and Food Safety Authority (LGL), Oberschleissheim, Germany
| | - Huong Quynh Luu
- National Institute of Veterinary Research (NIVR), Hanoi, Viet Nam
| | | | - Greta Gölz
- Freie Universitaet Berlin, Institute of Food Safety and Food Hygiene, Berlin, Germany
| | | | - Igor Gruntar
- University of Ljubljana, Institute of Microbiology and Parasitology, Ljubljana, Slovenia
| | - Frieda Jorgensen
- Public Health England, Food, Water and Environmental Laboratory - Porton, Salisbury, United Kingdom
| | - Miriam Koene
- Wageningen Bioveterinary Research, Lelystad, the Netherlands
| | - Jasna Kovac
- The Pennsylvania State University, Department of Food Science, State College, PA, United States
| | - Sonja Lick
- Max Rubner-Institute (MRI), Department of Safety and Quality of Meat, Kulmbach, Germany
| | | | - Annika Rohlfing
- Impetus GmbH & Co. Bioscience KG, Microbiology, Bremerhaven, Germany
| | - Anna Zawilak-Pawlik
- Hirszfeld Institute of Immunology and Experimental Therapy, PAS, Microbiology Department, Wroclaw, Poland
| | - Marko Rossow
- State Office for Consumer Protection Saxony-Anhalt, Department of Food Safety, Halle (Saale), Germany
| | | | | | | | | | - Ingrid Huber
- Bavarian Health and Food Safety Authority (LGL), Oberschleissheim, Germany
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Ogawa U, Koyama K, Koseki S. Rapid detection and enumeration of aerobic mesophiles in raw foods using dielectrophoresis. J Microbiol Methods 2021; 186:106251. [PMID: 34038753 DOI: 10.1016/j.mimet.2021.106251] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 05/21/2021] [Indexed: 11/24/2022]
Abstract
The concept of dielectrophoresis (DEP), which involves the movement of neutral particles by induced polarization in nonuniform electric fields, has been exploited in various biological applications. However, only a few studies have investigated the use of DEP for detecting and enumerating microorganisms in foodstuffs. Therefore, we aimed to evaluate the accuracy and efficiency of a DEP-based method for enumerating viable bacteria in three raw foods: freshly cut lettuce, chicken breast, and minced pork. The DEP separation of bacterial cells was conducted at 20 V of output voltage and 6000 to 9000 kHZ of frequency with sample conductivity of 30-70 μS/cm. The accuracy and validity of the DEP method for enumerating viable bacteria were compared with those of the conventional culture method; no significant variation was observed. We found a high correlation between the data obtained using DEP and the conventional aerobic plate count culture method, with a high coefficient of determination (R2 > 0.90) regardless of the food product; the difference in cell count data between both methods was within 1.0 log CFU/mL. Moreover, we evaluated the efficiency of the DEP method for enumerating bacterial cells in chicken breasts subjected to either freezing or heat treatment. After thermal treatment at 55 °C and 60 °C, the viable cell counts determined via the DEP method were found to be lower than those obtained using the conventional culture method, which implies that the DEP method may not be suitable for the direct detection of injured cells. In addition to its high accuracy and efficiency, the DEP method enables the determination of viable cell counts within 30 min, compared to 48 h required for the conventional culture method. In conclusion, the DEP method may be a potential alternative tool for rapid determination of viable bacteria in a variety of foodstuffs.
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Affiliation(s)
- Umi Ogawa
- Graduate School of Agricultural Science, Hokkaido University, Kita-9, Nishi-9, Kita-ku, Sapporo 060-8589, Japan
| | - Kento Koyama
- Graduate School of Agricultural Science, Hokkaido University, Kita-9, Nishi-9, Kita-ku, Sapporo 060-8589, Japan
| | - Shigenobu Koseki
- Graduate School of Agricultural Science, Hokkaido University, Kita-9, Nishi-9, Kita-ku, Sapporo 060-8589, Japan.
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Elmi A, Nasher F, Dorrell N, Wren B, Gundogdu O. Revisiting Campylobacter jejuni Virulence and Fitness Factors: Role in Sensing, Adapting, and Competing. Front Cell Infect Microbiol 2021; 10:607704. [PMID: 33614526 PMCID: PMC7887314 DOI: 10.3389/fcimb.2020.607704] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 12/11/2020] [Indexed: 12/18/2022] Open
Abstract
Campylobacter jejuni is the leading cause of bacterial foodborne gastroenteritis world wide and represents a major public health concern. Over the past two decades, significant progress in functional genomics, proteomics, enzymatic-based virulence profiling (EBVP), and the cellular biology of C. jejuni have improved our basic understanding of this important pathogen. We review key advances in our understanding of the multitude of emerging virulence factors that influence the outcome of C. jejuni–mediated infections. We highlight, the spatial and temporal dynamics of factors that promote C. jejuni to sense, adapt and survive in multiple hosts. Finally, we propose cohesive research directions to obtain a comprehensive understanding of C. jejuni virulence mechanisms.
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Affiliation(s)
- Abdi Elmi
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Fauzy Nasher
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Nick Dorrell
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Brendan Wren
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Ozan Gundogdu
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
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Gao R, Liao X, Zhao X, Liu D, Ding T. The diagnostic tools for viable but nonculturable pathogens in the food industry: Current status and future prospects. Compr Rev Food Sci Food Saf 2021; 20:2146-2175. [PMID: 33484068 DOI: 10.1111/1541-4337.12695] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 12/21/2020] [Accepted: 12/28/2020] [Indexed: 12/21/2022]
Abstract
Viable but nonculturable (VBNC) microorganisms have been recognized as pathogenic contaminants in foods and environments. The failure of VBNC cells to form the visible colonies hinders the ability to use conventional media for their detection. Efficient and rapid detection of pathogens in the VBNC state is a prerequisite to ensure the food safety and public health. Despite their nonculturability, VBNC cells have distinct characteristics, such as morphology, metabolism, chemical composition, and gene and protein expression, that have been used as the basis for the development of abundant diagnostic tools. This review covers the current status and advances in various approaches for examining microorganisms in the VBNC state, including but not limited to the methodological aspects, advantages, and drawbacks of each technique. Existing methods, such as direct viable count, SYTO/PI dual staining, and propidium monoazide quantitative polymerase chain reaction (PCR), as well as some techniques with potential to be applied in the future, such as digital PCR, enhanced-surface Raman spectroscopy, and impedance-based techniques, are summarized in depth. Finally, future prospects for the one-step detection of VBNC bacteria are proposed and discussed. We believe that this review can provide more optional methods for researchers and promote the development of rapid, accurate detecting methods, and for inspectors, the diagnostic tools can provide data to undertake risk analysis of VBNC cells.
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Affiliation(s)
- Rui Gao
- Key Laboratory for Agro-Products Postharvest Handling of Ministry of Agriculture, Zhejiang Key Laboratory for Agro-Food Processing, Department of Food Science and Nutrition, Zhejiang University, Hangzhou, Zhejiang, China
| | - Xinyu Liao
- Key Laboratory for Agro-Products Postharvest Handling of Ministry of Agriculture, Zhejiang Key Laboratory for Agro-Food Processing, Department of Food Science and Nutrition, Zhejiang University, Hangzhou, Zhejiang, China
| | - Xihong Zhao
- Research Center for Environmental Ecology and Engineering, Key Laboratory for Green Chemical Process of Ministry of Education, Hubei Key Laboratory of Novel Reactor and Green Chemical Technology, School of Environmental Ecology and Biological Engineering, Wuhan Institute of Technology, Wuhan, China
| | - Donghong Liu
- Key Laboratory for Agro-Products Postharvest Handling of Ministry of Agriculture, Zhejiang Key Laboratory for Agro-Food Processing, Department of Food Science and Nutrition, Zhejiang University, Hangzhou, Zhejiang, China
| | - Tian Ding
- Key Laboratory for Agro-Products Postharvest Handling of Ministry of Agriculture, Zhejiang Key Laboratory for Agro-Food Processing, Department of Food Science and Nutrition, Zhejiang University, Hangzhou, Zhejiang, China
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Han L, Wang K, Ma L, Delaquis P, Bach S, Feng J, Lu X. 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. Appl Environ Microbiol 2020; 86:e02566-19. [PMID: 32005729 PMCID: PMC7082562 DOI: 10.1128/aem.02566-19] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 01/21/2020] [Indexed: 11/20/2022] Open
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.
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Affiliation(s)
- Lu Han
- Food, Nutrition and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Kaidi Wang
- Food, Nutrition and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Lina Ma
- Food, Nutrition and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Pascal Delaquis
- Agriculture and Agri-Food Canada, Summerland Research and Development Centre, Summerland, British Columbia, Canada
| | - Susan Bach
- Agriculture and Agri-Food Canada, Summerland Research and Development Centre, Summerland, British Columbia, Canada
| | - Jinsong Feng
- Food, Nutrition and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, British Columbia, Canada
- Department of Microbiology and Immunology, The University of British Columbia, Vancouver, British Columbia, Canada
- Michael Smith Laboratories, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Xiaonan Lu
- Food, Nutrition and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, British Columbia, Canada
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11
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Lv R, Wang K, Feng J, Heeney DD, Liu D, Lu X. Detection and Quantification of Viable but Non-culturable Campylobacter jejuni. Front Microbiol 2020; 10:2920. [PMID: 31998253 PMCID: PMC6965164 DOI: 10.3389/fmicb.2019.02920] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 12/04/2019] [Indexed: 12/14/2022] Open
Abstract
Campylobacter can enter a viable but non-culturable (VBNC) state to evade various stresses, and this state is undetectable using traditional microbiological culturing techniques. These VBNC bacterial cells retain metabolism and demonstrate pathogenic potential due to their ability to resuscitate under favorable conditions. Rapid and accurate determination of VBNC Campylobacter is critical to further understand the induction and resuscitation of the dormancy state of this microbe in the agri-food system. Here, we integrated propidium monoazide (PMA) with real-time polymerase chain reaction (qPCR) targeting the rpoB gene to detect and quantify Campylobacter jejuni in the VBNC state. First, we optimized the concentration of PMA (20 μM) that could significantly inhibit the amplification of dead cells by qPCR with no significant interference on the amplification of viable cell DNA. PMA-qPCR was highly specific to C. jejuni with a limit of detection (LOD) of 2.43 log CFU/ml in pure bacterial culture. A standard curve for C. jejuni cell concentrations was established with the correlation coefficient of 0.9999 at the linear range of 3.43 to 8.43 log CFU/ml. Induction of C. jejuni into the VBNC state by osmotic stress (i.e., 7% NaCl) was rapid (<48 h) and effective (>10% population). The LOD of PMA-qPCR for VBNC C. jejuni exogenously applied to chicken breasts was 3.12 log CFU/g. In conclusion, PMA-qPCR is a rapid, specific, and sensitive method for the detection and quantification of VBNC C. jejuni in poultry products. This technique can give insight into the prevalence of VBNC Campylobacter in the environment and agri-food production system.
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Affiliation(s)
- Ruiling Lv
- Food, Nutrition, and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, BC, Canada.,College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, China
| | - Kaidi Wang
- Food, Nutrition, and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, BC, Canada
| | - Jinsong Feng
- Food, Nutrition, and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, BC, Canada
| | - Dustin D Heeney
- Food, Nutrition, and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, BC, Canada
| | - Donghong Liu
- College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou, China
| | - Xiaonan Lu
- Food, Nutrition, and Health Program, Faculty of Land and Food Systems, The University of British Columbia, Vancouver, BC, Canada
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12
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Maal-Bared R, Dixon B, Axelsson-Olsson D. Fate of internalized Campylobacter jejuni and Mycobacterium avium from encysted and excysted Acanthamoeba polyphaga. Exp Parasitol 2019; 199:104-110. [PMID: 30902623 DOI: 10.1016/j.exppara.2019.03.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 03/16/2019] [Accepted: 03/18/2019] [Indexed: 10/27/2022]
Abstract
Association of the water- and foodborne pathogen Campylobacter jejuni with free-living Acanthamoeba spp. trophozoites enhances C. jejuni survival and resistance to biocides and starvation. When facing less than optimal environmental conditions, however, the Acanthamoeba spp. host can temporarily transform from trophozoite to cyst and back to trophozoite, calling the survival of the internalized symbiont and resulting public health risk into question. Studies investigating internalized C. jejuni survival after A. castellanii trophozoite transformation have neither been able to detect its presence inside the Acanthamoeba cyst after encystation nor to confirm its presence upon excystation of trophozoites through culture-based techniques. The purpose of this study was to detect C. jejuni and Mycobacterium avium recovered from A. polyphaga trophozoites after co-culture and induction of trophozoite encystation using three different encystation methods (Neff's medium, McMillen's medium and refrigeration), as well as after cyst excystation. Internalized M. avium was used as a positive control, since studies have consistently detected the organism after co-culture and after host excystation. Concentrations of C. jejuni in A. polyphaga trophozoites were 4.5 × 105 CFU/ml, but it was not detected by PCR or culture post-encystation. This supports the hypothesis that C. jejuni may be digested during encystation of the amoebae. M. avium was recovered at a mean concentration of 1.9 × 104 from co-cultured trophozoites and 4.4 × 101 CFU/ml after excystation. The results also suggest that M. avium recovery post-excystation was statistically significantly different based on which encystation method was used, ranging from 1.3 × 101 for Neff's medium to 5.4 × 101 CFU/ml for refrigeration. No M. avium was recovered from A. polyphaga cysts when trophozoites were encysted by McMillen's medium. Since C. jejuni internalized in cysts would be more likely to survive harsh environmental conditions and disinfection, a better understanding of potential symbioses between free-living amoebae and campylobacters in drinking water distribution systems and food processing environments is needed to protect public health. Future co-culture experiments examining survival of internalized C. jejuni should carefully consider the encystation media used, and include molecular detection tools to falsify the hypothesis that C. jejuni may be present in a viable but not culturable state.
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Affiliation(s)
- Rasha Maal-Bared
- Centre for Research on Environmental Microbiology, University of Ottawa, Faculty of Medicine, 451 Smyth Road, Ottawa, ON, K1H 8M5, Canada.
| | - Brent Dixon
- Bureau of Microbial Hazards, Food Directorate, Health Canada, Ottawa, ON, K1A 0K9, Canada.
| | - Diana Axelsson-Olsson
- Centre for Ecology and Evolution in Microbial Model Systems, Linnaeus University, Kalmar, Sweden.
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13
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Pacholewicz E, Buhler C, Wulsten IF, Kraushaar B, Luu HQ, Iwobi AN, Huber I, Stingl K. Internal sample process control improves cultivation-independent quantification of thermotolerant Campylobacter. Food Microbiol 2018; 78:53-61. [PMID: 30497608 DOI: 10.1016/j.fm.2018.09.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 08/30/2018] [Accepted: 09/26/2018] [Indexed: 11/26/2022]
Abstract
Quantification of Campylobacter is challenging and one major reason is the fact that bacteria lose cultivability due to cold or oxygen stress during storage at retail. Alternative live/dead discriminatory qPCR currently lacks standardization and might overestimate live cells in the presence of dead cells. In this study an internal sample process control (ISPC) was developed. The ISPC consists of a specified number of peroxide-killed C. sputorum cells to be added to each sample in order to monitor (i) the level of reduction of the signal from dead cells and (ii) DNA losses during sample processing. A species-specific fragment of the 16S rRNA gene of C. sputorum was selected as real-time PCR target, based on its similar size and gene copy number compared to the C. jejuni/coli/lari target and confirmed in an exclusivity study. Extension of the amplification oligonucleotides for the target of thermotolerant Campylobacter improved real-time PCR efficiency, rendering the method suitable for quantification according to international standards. Concordant PCR signal variation of both C. jejuni and C. sputorum targets in co-inoculated chicken rinses verified the suitability of the ISPC. This provides a crucial step towards implementation of cultivation-independent quantification for improved food safety of fastidious bacteria.
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Affiliation(s)
- Ewa Pacholewicz
- German Federal Institute for Risk Assessment (BfR), Department of Biological Safety, National Reference Laboratory for Campylobacter, Berlin, Germany
| | - Christiane Buhler
- German Federal Institute for Risk Assessment (BfR), Department of Biological Safety, National Reference Laboratory for Campylobacter, Berlin, Germany
| | - Imke F Wulsten
- German Federal Institute for Risk Assessment (BfR), Department of Biological Safety, National Reference Laboratory for Campylobacter, Berlin, Germany
| | - Britta Kraushaar
- German Federal Institute for Risk Assessment (BfR), Department of Biological Safety, National Reference Laboratory for Campylobacter, Berlin, Germany
| | - Huong Quynh Luu
- National Institute of Veterinary Research (NIVR), Hanoi, Viet Nam
| | - Azuka N Iwobi
- Bavarian Health and Food Safety Authority (LGL), Oberschleissheim, Germany
| | - Ingrid Huber
- Bavarian Health and Food Safety Authority (LGL), Oberschleissheim, Germany
| | - Kerstin Stingl
- German Federal Institute for Risk Assessment (BfR), Department of Biological Safety, National Reference Laboratory for Campylobacter, Berlin, Germany.
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14
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Gölz G, Kittler S, Malakauskas M, Alter T. Survival of Campylobacter in the Food Chain and the Environment. CURRENT CLINICAL MICROBIOLOGY REPORTS 2018. [DOI: 10.1007/s40588-018-0092-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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15
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Hsieh YH, Simpson S, Kerdahi K, Sulaiman IM. A Comparative Evaluation Study of Growth Conditions for Culturing the Isolates of Campylobacter spp. Curr Microbiol 2017; 75:71-78. [PMID: 28887647 DOI: 10.1007/s00284-017-1351-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 08/28/2017] [Indexed: 10/18/2022]
Abstract
Campylobacter is one of the leading causes of foodborne travelers' diarrhea worldwide. Although a large number cases of campylobacteriosis go undiagnosed or unreported, it is considered as the second most common foodborne illness in the USA affecting over 1.3 million individuals every year. Of various Campylobacter species, C. jejuni, C. coli, and C. lari have been accounted for causing more than 99% of human infections. Thus, there is a need to have efficient isolation method to protect public health on food safety and monitoring the burden of campylobacteriosis. Nevertheless, it is a challenging task as the exposure of environmental stress during isolation process makes Campylobacter species less culturable. Sixteen Campylobacter spp. were used to evaluate the current protocols used in Campylobacter isolation. For optimal recovery, a range of growth media (Bolton, Columbia, Muller Hinton, CVA Campy and mCCDA), incubation temperatures, and additional supplements (including antibiotics) were tested. Blood agars without antibiotics were sufficient for the initial recovery. Afterward, the isolates could grow on agars without any supplements, and in some cases growth was observed in the presence of antibiotics. Incubation at 37 °C was found to be the optimal temperature for the recovery and the growth of most species. Additionally, a food adulteration study was also carried out by artificially contaminating three food matrices that included egg, milk, and infant cereal, with two isolates of C. jejuni and C. coli. Results of this study should provide the insight for culturing and isolation of Campylobacter from food and other sources.
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Affiliation(s)
- Ying-Hsin Hsieh
- Microbiological Sciences Branch, Southeast Food and Feed Laboratory, U.S. Food and Drug Administration, 60 Eighth Street NE, Atlanta, GA, 30309, USA
| | - Steven Simpson
- Microbiological Sciences Branch, Southeast Food and Feed Laboratory, U.S. Food and Drug Administration, 60 Eighth Street NE, Atlanta, GA, 30309, USA
| | - Khalil Kerdahi
- Microbiological Sciences Branch, Southeast Food and Feed Laboratory, U.S. Food and Drug Administration, 60 Eighth Street NE, Atlanta, GA, 30309, USA
| | - Irshad M Sulaiman
- Microbiological Sciences Branch, Southeast Food and Feed Laboratory, U.S. Food and Drug Administration, 60 Eighth Street NE, Atlanta, GA, 30309, USA.
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16
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Campylobacter jejuni Isolation/Enumeration from Environmental Samples. Methods Mol Biol 2016; 1512:1-8. [PMID: 27885593 DOI: 10.1007/978-1-4939-6536-6_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/09/2023]
Abstract
Currently, there is no universally accepted standard media or method for the recovery of Campylobacter species. This is likely due to the ubiquity of the organism in nature, the complex sample matrices from which the organism is often recovered, as well as the fragile/viable-but nonculturable state the organism assumes in response to stress. The use of a sterile filter placed upon a nonselective Brucella Agar Blood Plate (BAB), followed by incubation at 37 °C in a hydrogen-containing atmosphere (Campycheck), is one method to recover stressed and emerging Campylobacter spp. from complex environmental matrices; however, this technique does not currently allow for the enumeration of the recovered organisms. Enumeration is performed using serial dilutions of sample homogenate plated onto modified Campy-Cefex media followed by incubation at either 37 °C or 42 °C in a microaerobic atmosphere.
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17
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Ayrapetyan M, Oliver JD. The viable but non-culturable state and its relevance in food safety. Curr Opin Food Sci 2016. [DOI: 10.1016/j.cofs.2016.04.010] [Citation(s) in RCA: 85] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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18
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Viable but Nonculturable and Persister Cells Coexist Stochastically and Are Induced by Human Serum. Infect Immun 2015; 83:4194-203. [PMID: 26283335 DOI: 10.1128/iai.00404-15] [Citation(s) in RCA: 79] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 08/05/2015] [Indexed: 01/09/2023] Open
Abstract
Dormancy holds a vital role in the ecological dynamics of microorganisms. Specifically, entry into dormancy allows cells to withstand times of stress while maintaining the potential for reentry into an active existence. The viable but nonculturable (VBNC) state and antibiotic persistence are two well-recognized conditions of dormancy demonstrated to contribute to bacterial stress tolerance and, as a consequence, yield populations that are tolerant to high-dose antibiotics. Aside from this commonality, more evidence is being presented that indicates the relatedness of these two states. Here, we demonstrate that VBNC cells are present during persister isolation experiments, further indicating that these cells coexist and are induced by the same conditions. Interestingly, we reveal that VBNC cells can exist stochastically in unstressed growing cultures, a finding that is characteristic of persisters. Furthermore, human serum induces the formation of both VBNC cells and persisters, a finding not previously described for either dormancy state. Lastly, we describe the role of toxin-antitoxin systems (TAS) in the induction of the VBNC state and report that these TAS, which are classically implicated in persister cell formation, are also induced during incubation in human serum. This study provides evidence for the recently proposed "dormancy continuum hypothesis" and substantiates the physical and molecular relatedness of VBNC and persister cells in a standardized model organism. Notably, these results provide new evidence for the clinical significance of VBNC and persister cells.
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