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Flint R, Laucirica DR, Chan HK, Chang BJ, Stick SM, Kicic A. Stability Considerations for Bacteriophages in Liquid Formulations Designed for Nebulization. Cells 2023; 12:2057. [PMID: 37626867 PMCID: PMC10453214 DOI: 10.3390/cells12162057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 08/10/2023] [Accepted: 08/10/2023] [Indexed: 08/27/2023] Open
Abstract
Pulmonary bacterial infections present a significant health risk to those with chronic respiratory diseases (CRDs) including cystic fibrosis (CF) and chronic-obstructive pulmonary disease (COPD). With the emergence of antimicrobial resistance (AMR), novel therapeutics are desperately needed to combat the emergence of resistant superbugs. Phage therapy is one possible alternative or adjunct to current antibiotics with activity against antimicrobial-resistant pathogens. How phages are administered will depend on the site of infection. For respiratory infections, a number of factors must be considered to deliver active phages to sites deep within the lung. The inhalation of phages via nebulization is a promising method of delivery to distal lung sites; however, it has been shown to result in a loss of phage viability. Although preliminary studies have assessed the use of nebulization for phage therapy both in vitro and in vivo, the factors that determine phage stability during nebulized delivery have yet to be characterized. This review summarizes current findings on the formulation and stability of liquid phage formulations designed for nebulization, providing insights to maximize phage stability and bactericidal activity via this delivery method.
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Affiliation(s)
- Rohan Flint
- School of Biomedical Sciences, The University of Western Australia, Perth, WA 6009, Australia;
- Wal-yan Respiratory Research Center, Telethon Kids Institute, The University of Western Australia, Perth, WA 6009, Australia; (D.R.L.); (S.M.S.)
| | - Daniel R. Laucirica
- Wal-yan Respiratory Research Center, Telethon Kids Institute, The University of Western Australia, Perth, WA 6009, Australia; (D.R.L.); (S.M.S.)
| | - Hak-Kim Chan
- Advanced Drug Delivery Group, School of Pharmacy, University of Sydney, Sydney, NSW 2050, Australia;
| | - Barbara J. Chang
- The Marshall Center for Infectious Diseases Research and Training, School of Biomedical Sciences, The University of Western Australia, Perth, WA 6009, Australia;
| | - Stephen M. Stick
- Wal-yan Respiratory Research Center, Telethon Kids Institute, The University of Western Australia, Perth, WA 6009, Australia; (D.R.L.); (S.M.S.)
- Department of Respiratory and Sleep Medicine, Perth Children’s Hospital, Perth, WA 6009, Australia
- Centre for Cell Therapy and Regenerative Medicine, School of Medicine and Pharmacology, Harry Perkins Institute of Medical Research, The University of Western Australia, Perth, WA 6009, Australia
| | - Anthony Kicic
- Wal-yan Respiratory Research Center, Telethon Kids Institute, The University of Western Australia, Perth, WA 6009, Australia; (D.R.L.); (S.M.S.)
- Department of Respiratory and Sleep Medicine, Perth Children’s Hospital, Perth, WA 6009, Australia
- Centre for Cell Therapy and Regenerative Medicine, School of Medicine and Pharmacology, Harry Perkins Institute of Medical Research, The University of Western Australia, Perth, WA 6009, Australia
- School of Population Health, Curtin University, Perth, WA 6102, Australia
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2
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Sala-Comorera L, Reynolds LJ, Martin NA, O'Sullivan JJ, Meijer WG, Fletcher NF. Decay of infectious SARS-CoV-2 and surrogates in aquatic environments. WATER RESEARCH 2021; 201:117090. [PMID: 34111729 PMCID: PMC8005746 DOI: 10.1016/j.watres.2021.117090] [Citation(s) in RCA: 51] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Revised: 03/23/2021] [Accepted: 03/24/2021] [Indexed: 05/03/2023]
Abstract
The introduction of SARS-CoV-2 containing human stool and sewage into water bodies may raise public health concerns. However, assessment of public health risks by faecally contaminated water is limited by a lack of knowledge regarding the persistence of infectious SARS-CoV-2 in water. In the present study the decay rates of viable infectious SARS-CoV-2 and SARS-CoV-2 RNA were determined in river and seawater at 4 and 20°C. These decay rates were compared to S. typhimurium bacteriophage MS2 and pepper mild mottle virus (PMMoV). Persistence of viable SARS-CoV-2 was temperature dependent, remaining infectious for significantly longer periods of time in both freshwater and seawater at 4°C than at 20°C. T90 for infectious SARS-CoV-2 in river water was 2.3 days and 3.8 days at 20°C and 4°C, respectively. The T90 values were 1.1 days and 2.2 days in seawater at 20°C and 4°C, respectively. In contrast to the rapid inactivation of infectious SARS-CoV-2 in river and sea water, viral RNA was relatively stable. The RNA decay rates were increased in non-sterilised river and seawater, presumably due to the presence of microbiota. The decay rates of infectious MS2, MS2 RNA and PMMoV RNA differed significantly from the decay rate of SARS-CoV-2 RNA, suggesting that their use as surrogate markers for the persistence of SARS-CoV-2 in the environment is limited.
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Affiliation(s)
- Laura Sala-Comorera
- UCD School of Biomolecular and Biomedical Science, UCD Earth Institute and UCD Conway Institute, University College Dublin, Dublin 4, Ireland
| | - Liam J Reynolds
- UCD School of Biomolecular and Biomedical Science, UCD Earth Institute and UCD Conway Institute, University College Dublin, Dublin 4, Ireland
| | - Niamh A Martin
- UCD School of Biomolecular and Biomedical Science, UCD Earth Institute and UCD Conway Institute, University College Dublin, Dublin 4, Ireland
| | - John J O'Sullivan
- UCD School of Civil Engineering, UCD Dooge Centre for Water Resources Research and UCD Earth Institute, University College Dublin, Dublin 4, Ireland
| | - Wim G Meijer
- UCD School of Biomolecular and Biomedical Science, UCD Earth Institute and UCD Conway Institute, University College Dublin, Dublin 4, Ireland.
| | - Nicola F Fletcher
- UCD School of Veterinary Medicine and UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland
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3
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Chang RYK, Morales S, Okamoto Y, Chan HK. Topical application of bacteriophages for treatment of wound infections. Transl Res 2020; 220:153-166. [PMID: 32268129 PMCID: PMC7293950 DOI: 10.1016/j.trsl.2020.03.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 03/08/2020] [Accepted: 03/12/2020] [Indexed: 12/24/2022]
Abstract
Wound infections associated with multidrug-resistant (MDR) bacteria are one of the important threats to public health. Bacteriophage (phage) therapy is a promising alternative or supplementary therapeutic approach to conventional antibiotics for combating MDR bacterial infections. In recent years, significant effort has been put into the development of phage formulations and delivery methods for topical applications, along with preclinical and clinical uses of phages for the treatment of acute and chronic wound infections. This paper reviews the application of phages for wound infections, with focus on the current status of phage formulations (including liquid, semi-solid and liposome-encapsulated formulations, phage-immobilized wound dressings), safety and efficacy assessment in clinical settings and major challenges to overcome.
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Affiliation(s)
- Rachel Yoon Kyung Chang
- Advanced Drug Delivery Group, The University of Sydney, Faculty of Medicine and Health, School of Pharmacy, Sydney, New South Wales, Australia
| | | | - Yuko Okamoto
- Faculty of Pharmaceutical Sciences, Sojo University, Kumamoto, Japan
| | - Hak-Kim Chan
- Advanced Drug Delivery Group, The University of Sydney, Faculty of Medicine and Health, School of Pharmacy, Sydney, New South Wales, Australia.
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4
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Benediktsdóttir E, Gunnarsdóttir MJ, Ómarsdóttir BD, Sigurjónsson VÍ, Gardarsson SM. Virus inactivation in groundwater in a postglacial lava field in arctic climate. Lett Appl Microbiol 2020; 70:282-289. [PMID: 31894582 DOI: 10.1111/lam.13271] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 12/20/2019] [Accepted: 12/20/2019] [Indexed: 01/17/2023]
Abstract
Outbreaks of viral gastroenteritis are often connected to contaminated drinking water. The assessment of the water quality relies on the cultivation of indicator bacteria, and little is known of the fate of viruses in groundwater, especially in arctic regions. In Iceland, the groundwater temperature is between 3 and 6°C. The aim of this study was to determine virus inactivation at low temperature in a groundwater microcosm and in a borehole in a postglacial lava field. Two phage species that are commonly used as surrogates for norovirus were used, MS2 and PhiX174. Dialysis bags were used for the samples, and a device was constructed to hold many samples at a time and protect the samples in the borehole. No significant decrease of infective PhiX174 phages in the borehole or of the MS2 phages in the microcosm was observed. A slightly significant decrease of PhiX174 in the microcosm was noticed, with one log reduction time of 476 days. On the other hand, a significant reduction in MS2 was found in the field test, where the time needed for 90% reduction was 12·5 days. The results showed that an infective virus can exist in groundwater for months or years in arctic regions and a great difference may exist between results from microcosm and field tests. SIGNIFICANCE AND IMPACT OF THE STUDY: This study reveals that arctic regions are highly sensitive to virus contamination as an infective virus may exist in groundwater for years at low temperature. The results also show that the virus inactivation observed in field tests may differ considerably from the inactivation observed in laboratory microcosms. The results emphasize the importance of large protection zones around drinking water intakes as well as good wastewater treatment so that the likelihood of faecal contamination of groundwater is reduced.
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Affiliation(s)
- E Benediktsdóttir
- Institute of Life and Environmental Sciences, University of Iceland, Reykjavík, Iceland
| | - M J Gunnarsdóttir
- Engineering Research Institute, University of Iceland, Reykjavík, Iceland
| | - B D Ómarsdóttir
- Institute of Life and Environmental Sciences, University of Iceland, Reykjavík, Iceland
| | - V Í Sigurjónsson
- Engineering Research Institute, University of Iceland, Reykjavík, Iceland
| | - S M Gardarsson
- Engineering Research Institute, University of Iceland, Reykjavík, Iceland
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5
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Schwarz KR, Sidhu JPS, Toze S, Li Y, Lee E, Gruchlik Y, Pritchard DL. Decay rates of Escherichia coli, Enterococcus spp., F-specific bacteriophage MS2, somatic coliphage and human adenovirus in facultative pond sludge. WATER RESEARCH 2019; 154:62-71. [PMID: 30771708 DOI: 10.1016/j.watres.2019.01.027] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 01/21/2019] [Accepted: 01/22/2019] [Indexed: 06/09/2023]
Abstract
The purpose of this study was to evaluate the efficacy of a waste stabilization pond (WSP) system to reduce pathogen contaminants in sludge. This included examining the factors that influence the fate and concentration of human pathogens and their indicators in two sludge layers. The decay rates of five study microorganisms were determined under in-situ conditions at a WSP. The background levels of fecal origin microorganisms were consistently detected (ranging: Escherichia coli 104 to 106, enterococci 101 to 103, F-specific bacteriophage (MS2) 101 to 103 and somatic coliphage 101 to 104 colony-forming units (CFU) mL-1, as well as 101 to 102 human adenovirus gene copies mL-1) in the primary facultative pond. Among microorganisms tested, the bacteria generally decayed faster than adenovirus and bacteriophage, particularly in the upper sludge layer. Due to the observed regrowth of E. coli, it may have a limited value as an indicator for pathogen removal in the wastewater stabilization ponds. The abundance of E. coli numbers within the pond biome followed changes in pond temperature over time. The results of the study suggest that viruses could survive for a long time, particularly in deeper layers (>1 metre) in the sludge, during winter months (T90 = 156 d). The presence of human pathogens in WSP sludge, in particular viruses, may be a barrier to its beneficial reuse in agriculture. The results indicate that additional treatment of sludge may be required to mitigate potential public health risks from reuse of sludge for agricultural purposes.
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Affiliation(s)
- K R Schwarz
- Molecular and Life Sciences, Curtin University, GPO Box U1987 Perth, Western Australia, 6845, Australia; CSIRO Oceans and Atmosphere, 41 Boggo Road, EcoSciences Precinct, Dutton Park, Queensland, 4102, Australia.
| | - J P S Sidhu
- CSIRO Oceans and Atmosphere, 41 Boggo Road, EcoSciences Precinct, Dutton Park, Queensland, 4102, Australia.
| | - S Toze
- CSIRO Land and Water, 41 Boggo Road, EcoSciences Precinct, Dutton Park, Queensland, 4102, Australia.
| | - Y Li
- CSIRO Agriculture and Food, Queensland Biosciences Precinct, 306 Carmody Road, St Lucia, QLD, 4067, Australia.
| | - E Lee
- Water Corporation, 629 Newcastle St, Leederville, WA, 6007, Australia.
| | - Y Gruchlik
- Molecular and Life Sciences, Curtin University, GPO Box U1987 Perth, Western Australia, 6845, Australia.
| | - D L Pritchard
- Molecular and Life Sciences, Curtin University, GPO Box U1987 Perth, Western Australia, 6845, Australia.
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Vinner GK, Vladisavljević GT, Clokie MRJ, Malik DJ. Microencapsulation of Clostridium difficile specific bacteriophages using microfluidic glass capillary devices for colon delivery using pH triggered release. PLoS One 2017; 12:e0186239. [PMID: 29023522 PMCID: PMC5638336 DOI: 10.1371/journal.pone.0186239] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Accepted: 09/27/2017] [Indexed: 12/14/2022] Open
Abstract
The prevalence of pathogenic bacteria acquiring multidrug antibiotic resistance is a global health threat to mankind. This has motivated a renewed interest in developing alternatives to conventional antibiotics including bacteriophages (viruses) as therapeutic agents. The bacterium Clostridium difficile causes colon infection and is particularly difficult to treat with existing antibiotics; phage therapy may offer a viable alternative. The punitive environment within the gastrointestinal tract can inactivate orally delivered phages. C. difficile specific bacteriophage, myovirus CDKM9 was encapsulated in a pH responsive polymer (Eudragit® S100 with and without alginate) using a flow focussing glass microcapillary device. Highly monodispersed core-shell microparticles containing phages trapped within the particle core were produced by in situ polymer curing using 4-aminobenzoic acid dissolved in the oil phase. The size of the generated microparticles could be precisely controlled in the range 80 μm to 160 μm through design of the microfluidic device geometry and by varying flow rates of the dispersed and continuous phase. In contrast to free 'naked' phages, those encapsulated within the microparticles could withstand a 3 h exposure to simulated gastric fluid at pH 2 and then underwent a subsequent pH triggered burst release at pH 7. The significance of our research is in demonstrating that C. difficile specific phage can be formulated and encapsulated in highly uniform pH responsive microparticles using a microfluidic system. The microparticles were shown to afford significant protection to the encapsulated phage upon prolonged exposure to an acid solution mimicking the human stomach environment. Phage encapsulation and subsequent release kinetics revealed that the microparticles prepared using Eudragit® S100 formulations possess pH responsive characteristics with phage release triggered in an intestinal pH range suitable for therapeutic purposes. The results reported here provide proof-of-concept data supporting the suitability of our approach for colon targeted delivery of phages for therapeutic purposes.
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Affiliation(s)
- Gurinder K. Vinner
- Chemical Engineering Department, Loughborough University, Loughborough, United Kingdom
| | | | - Martha R. J. Clokie
- Department of Infection, Immunity and Inflammation, University of Leicester, Leicester, United Kingdom
| | - Danish J. Malik
- Chemical Engineering Department, Loughborough University, Loughborough, United Kingdom
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7
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Bertrand I, Schijven JF, Sánchez G, Wyn-Jones P, Ottoson J, Morin T, Muscillo M, Verani M, Nasser A, de Roda Husman AM, Myrmel M, Sellwood J, Cook N, Gantzer C. The impact of temperature on the inactivation of enteric viruses in food and water: a review. J Appl Microbiol 2012; 112:1059-74. [PMID: 22380614 DOI: 10.1111/j.1365-2672.2012.05267.x] [Citation(s) in RCA: 162] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Temperature is considered as the major factor determining virus inactivation in the environment. Food industries, therefore, widely apply temperature as virus inactivating parameter. This review encompasses an overview of viral inactivation and virus genome degradation data from published literature as well as a statistical analysis and the development of empirical formulae to predict virus inactivation. A total of 658 data (time to obtain a first log(10) reduction) were collected from 76 published studies with 563 data on virus infectivity and 95 data on genome degradation. Linear model fitting was applied to analyse the effects of temperature, virus species, detection method (cell culture or molecular methods), matrix (simple or complex) and temperature category (<50 and ≥50°C). As expected, virus inactivation was found to be faster at temperatures ≥50°C than at temperatures <50°C, but there was also a significant temperature-matrix effect. Virus inactivation appeared to occur faster in complex than in simple matrices. In general, bacteriophages PRD1 and PhiX174 appeared to be highly persistent whatever the matrix or the temperature, which makes them useful indicators for virus inactivation studies. The virus genome was shown to be more resistant than infectious virus. Simple empirical formulas were developed that can be used to predict virus inactivation and genome degradation for untested temperatures, time points or even virus strains.
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Affiliation(s)
- I Bertrand
- Laboratoire de Chimie Physique et Microbiologie pour l'Environnement (LCPME), Université de Lorraine, CNRS, Nancy, France
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8
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Jończyk E, Kłak M, Międzybrodzki R, Górski A. The influence of external factors on bacteriophages--review. Folia Microbiol (Praha) 2011; 56:191-200. [PMID: 21625877 PMCID: PMC3131515 DOI: 10.1007/s12223-011-0039-8] [Citation(s) in RCA: 370] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Accepted: 02/08/2011] [Indexed: 11/23/2022]
Abstract
The ability of bacteriophages to survive under unfavorable conditions is highly diversified. We summarize the influence of different external physical and chemical factors, such as temperature, acidity, and ions, on phage persistence. The relationships between a phage’s morphology and its survival abilities suggested by some authors are also discussed. A better understanding of the complex problem of phage sensitivity to external factors may be useful not only for those interested in pharmaceutical and agricultural applications of bacteriophages, but also for others working with phages.
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Affiliation(s)
- E Jończyk
- Bacteriophage Laboratory, L. Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, Rudolfa Weigla 12, 53-114, Wroclaw, Poland
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Song I, Choi CY, O'Shaughnessy S, Gerba CP. Effects of temperature and moisture on coliphage PRD-1 survival in soil. J Food Prot 2005; 68:2118-22. [PMID: 16245716 DOI: 10.4315/0362-028x-68.10.2118] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The goal of this study was to quantitatively assess the effects of temperature and soil moisture on the survival of coliphage PRD-1 in soil. PRD-1 was added to sandy loam soil at five different soil moisture levels. The soil seeded with PRD-1 was packed into sterile polyethylene jars and exposed to eight different temperatures in an oven. Samples were collected over 14 to 25 days depending on the temperature. The inactivation rate of PRD-1 increased linearly with increased temperature. The inactivation rate gradually decreased when the soil moisture level decreased from 20.9 to 8.9%. However, the inactivation rate increased when the soil moisture content reached 5.1%, suggesting the existence of an optimal soil moisture condition for PRD-1 survival. It is also possible that there is a threshold soil moisture level below which the inactivation of PRD-1 suddenly increases. Marked reductions in recoveries were observed as the soil moisture approached or fell below 5.0% as a result of evaporation. The increased inactivation of PRD-1 due to strong association with soil particles may have caused rapid reductions in recoveries. The evaporation process appeared to affect PRD-1 survival substantially at higher temperatures whereas little effect was observed at lower temperatures. A model developed from this study predicted PRD-1 survival in subsurface soil in field conditions with an average error of 11.0%.
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Affiliation(s)
- Inhong Song
- Department of Agricultural and Biosystems Engineering, University of Arizona, Tucson, Arizona 85721, USA
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Stine SW, Song I, Choi CY, Gerba CP. Effect of relative humidity on preharvest survival of bacterial and viral pathogens on the surface of cantaloupe, lettuce, and bell peppers. J Food Prot 2005; 68:1352-8. [PMID: 16013370 DOI: 10.4315/0362-028x-68.7.1352] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The purpose of this study was to compare the effects of humidity on the preharvest survival of microbial pathogens on cantaloupe, lettuce, and bell peppers. An additional goal was to evaluate Clostridium perfringens as an indicator of fecal contamination on produce. The microorganisms used in this study included Escherichia coli, E. coli O157:H7, Shigella sonnei, Salmonella enterica subsp. enterica, Clostridium perfringens, hepatitis A virus (HAV), feline calicivirus (FCV), and coliphage PRD1. The study took place in a controlled environment chamber that allowed for the control of temperature (18 to 26 degrees C) and relative humidity. Survival rates under high (mean, 85.7 to 90.3%) and low (mean, 45.1 to 48.4%) relative humidity were compared. The surfaces of the edible portion of each plant were inoculated with the study microorganisms. Samples were collected throughout 2 weeks. More microorganisms survived significantly longer (P < 0.05) on cantaloupe than on lettuce and bell peppers. The type of produce on which each organism experienced the highest inactivation rate tended to change with relative humidity. The survival of microorganisms on produce surfaces was not uniformly affected by relative humidity. Of the studied microorganisms, HAV, PRD1, and C. perfringens were found to have the lowest inactivation rates, whereas FCV and E. coli ATCC 25922 tended to become inactivated most rapidly. C. perfringens generally survived longer than all other bacteria and FCV in all experiments. This trend suggests that C. perfringens may be an acceptable indicator of bacterial contamination and survival in various environments and on different types of crops.
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Affiliation(s)
- Scott W Stine
- Department of Soil, Water, and Environmental Science, University of Arizona, Tucson, Arizona 85721, USA
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Stine SW, Song I, Choi CY, Gerba CP. Application of microbial risk assessment to the development of standards for enteric pathogens in water used to irrigate fresh produce. J Food Prot 2005; 68:913-8. [PMID: 15895721 DOI: 10.4315/0362-028x-68.5.913] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Microbial contamination of the surfaces of cantaloupe, iceberg lettuce, and bell peppers via contact with irrigation water was investigated to aid in the development of irrigation water quality standards for enteric bacteria and viruses. Furrow and subsurface drip irrigation methods were evaluated with the use of nonpathogenic surrogates, coliphage PRD1, and Escherichia coli ATCC 25922. The concentrations of hepatitis A virus (HAV) and Salmonella in irrigation water necessary to achieve a 1:10,000 annual risk of infection, the acceptable level of risk used for drinking water by the U.S. Environmental Protection Agency, were calculated with a quantitative microbial risk assessment approach. These calculations were based on the transfer of the selected nonpathogenic surrogates to fresh produce via irrigation water, as well as previously determined preharvest inactivation rates of pathogenic microorganisms on the surfaces of fresh produce. The risk of infection was found to be variable depending on type of crop, irrigation method, and days between last irrigation event and harvest. The worst-case scenario, in which produce is harvested and consumed the day after the last irrigation event and maximum exposure is assumed, indicated that concentrations of 2.5 CFU/100 ml of Salmonella and 2.5 x 10(-5) most probable number per 100 ml of HAV in irrigation water would result in an annual risk of 1:10,000 when the crop was consumed. If 14 days elapsed before harvest, allowing for die-off of the pathogens, the concentrations were increased to 5.7 x 10(3) Salmonella per 100 ml and 9.9 x 10(-3) HAV per 100 ml.
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Affiliation(s)
- Scott W Stine
- Department of Soil, Water, and Environmental Science, University of Arizona, Tucson, Arizona 85721, USA
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