Publications by authors named "Weiping Chu"

18 Publications

  • Page 1 of 1

Eradication of Intracellular Salmonella Typhimurium by Polyplexes of Acid-Transforming Chitosan and Fragment DNA.

Macromol Biosci 2021 Apr 18:e2000408. Epub 2021 Apr 18.

132 Sprague Hall, Irvine, CA, 92697, USA.

Antibiotics are highly successful against microbial infections. However, current challenges include rising antibiotic resistance rates and limited efficacy against intracellular pathogens. A novel form of a nanomaterial-based antimicrobial agent is investigated for efficient treatment of an intracellular Salmonella enterica sv Typhimurium infection. A known antimicrobial polysaccharide, chitosan, is engineered to be readily soluble under neutral aqueous conditions for systemic administration. The modified biologic, named acid-transforming chitosan (ATC), transforms into an insoluble, antimicrobial compound in the mildly acidic intracellular compartment. In cell culture experiments, ATC is confirmed to have antimicrobial activity against intracellular S. Typhimurium in a concentration- and pH-dependent manner, without affecting the host cells, RAW264.7 macrophages. For improved cellular uptake and pharmacokinetic/pharmacodynamic properties, ATC is further complexed with fragment DNA (fDNA), to form nano-sized spherical polyplexes. The resulting ATC/fDNA polyplexes efficiently eradicated S. Typhimurium from RAW264.7 macrophages. ATC/fDNA polyplexes may bind with microbial wall and membrane components. Consistent with this expectation, transposon insertion sequencing of a complex random mutant S. Typhimurium library incubated with ATC does not reveal specific genomic target regions of the antimicrobial. This study demonstrates the utility of a molecularly engineered nanomaterial as an efficient and safe antimicrobial agent, particularly against an intracellular pathogen.
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http://dx.doi.org/10.1002/mabi.202000408DOI Listing
April 2021

Mechanisms of Attachment and Survival on In-Shell Black Peppercorns, Almonds, and Hazelnuts.

Front Microbiol 2020 23;11:582202. Epub 2020 Oct 23.

Department of Food Science and Nutrition, Illinois Institute of Technology, Bedford Park, IL, United States.

subspecies I (ssp 1) is the leading cause of hospitalizations and deaths due to known bacterial foodborne pathogens in the United States and is frequently implicated in foodborne disease outbreaks associated with spices and nuts. However, the underlying mechanisms of this association have not been fully elucidated. In this study, we evaluated the influence of storage temperature (4 or 25°C), relative humidity (20 or 60%), and food surface characteristics on the attachment and survival of five individual strains representing ssp 1 serovars Typhimurium, Montevideo, Braenderup, Mbandaka, and Enteritidis on raw in-shell black peppercorns, almonds, and hazelnuts. We observed a direct correlation between the food surface roughness and ssp 1 attachment, and detected significant inter-strain difference in survival on the shell surface under various storage conditions. A combination of low relative humidity (20%) and ambient storage temperature (25°C) resulted in the most significant reduction of on shell surfaces ( < 0.05). To identify genes potentially associated with attachment and survival on shell surfaces, we inoculated a library of 120,000 random transposon insertion mutants of an Enteritidis strain on almond shells, and screened for mutant survival after 1, 3, 7, and 14 days of storage at 20% relative humidity and 25°C. Mutants in 155 . Enteritidis genes which are involved in carbohydrate metabolic pathways, aerobic and anaerobic respiration, inner membrane transport, and glutamine synthesis displayed significant selection on almond shells ( < 0.05). Findings of this study suggest that various food attributes, environmental factors, and an unexpectedly complex metabolic and regulatory network in ssp 1 collectively contribute to the bacterial attachment and survival on low moisture shell surface, providing new data for the future development of knowledge-based intervention strategies.
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http://dx.doi.org/10.3389/fmicb.2020.582202DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7644838PMC
October 2020

Identification of Novel Genes Mediating Survival of on Low-Moisture Foods via Transposon Sequencing Analysis.

Front Microbiol 2020 15;11:726. Epub 2020 May 15.

Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, United States.

is the leading foodborne pathogen associated with outbreaks involving low-moisture foods (LMFs). However, the genes involved in s long-term survival on LMFs remain poorly characterized. In this study, in-shell pistachios were inoculated with Tnbased mutant libraries of . Enteritidis P125109, . Typhimurium 14028s, and . Newport C4.2 at approximate 10 CFU/g and stored at 25°C. Transposon sequencing analysis (Tn-seq) was then employed to determine the relative abundance of each Tn insertion site immediately after inoculation (T), after drying (T), and at 120 days (T). In . Enteritidis, . Typhimurium, and . Newport mutant libraries, the relative abundance of 51, 80, and 101 Tn insertion sites, respectively, was significantly lower at T compared to T, while in libraries of . Enteritidis and . Typhimurium the relative abundance of 42 and 68 Tn insertion sites, respectively, was significantly lower at T compared to T. Tn insertion sites with reduced relative abundance in this competition assay were localized in DNA repair, lipopolysaccharide biosynthesis and stringent response genes. Twelve genes among those under strong negative selection in the competition assay were selected for further study. Whole gene deletion mutants in ten of these genes, , , , , , , , , and , were impaired for individual survival on pistachios. The findings highlight the value of combined mutagenesis and sequencing to identify novel genes important for the survival of in low-moisture foods.
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http://dx.doi.org/10.3389/fmicb.2020.00726DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7242855PMC
May 2020

Neutral barcoding of genomes reveals the dynamics of Salmonella colonization in cattle and their peripheral lymph nodes.

Vet Microbiol 2018 Jul 16;220:97-106. Epub 2018 May 16.

Dept. of Microbiology and Molecular Genetics, UC Irvine, B240 Med Sci Bldg., Irvine, CA 92697, United States. Electronic address:

Feedlot cattle often contain Salmonella. The number of bacteria that initiate colonization of different cattle organs and the bacterial migration within these large animals are poorly understood. To investigate these questions, we constructed wild-type isogenic tagged strains (WITS) of Salmonella by inserting 21-base barcodes flanked by Illumina sequencing primers into a neutral genome location. We then delivered several different pools of uniquely barcoded clones orally and into multiple intradermal sites, in individual Holstein steers, and subsequently performed Salmonella-directed sequence tag-based analysis of microbial populations (STAMP). Using high-throughput sequencing of the barcodes of Salmonella grown from steer lymph nodes, organs and feces, we monitored how individual barcoded clones travel from different entry sites within animals. Data showed that gastrointestinal colonization was established by up to hundreds of Salmonella founder cells, whereas peripheral lymph nodes were usually colonized by very low numbers of founding bacteria, often originating from the nearest draining intradermal delivery site. Transmission of Salmonella from the gastrointestinal tract to the lymphatic system was frequently observed, whereas entry of intradermally delivered bacteria into the gut was rare. Bacteria undergo limited extraintestinal proliferation within or prior to arrival at peripheral lymph nodes. Overall, the application of the STAMP technique facilitated characterization of the migration routes and founder population size of Salmonella within feedlot cattle and their organs and lymph nodes in unprecedented detail.
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http://dx.doi.org/10.1016/j.vetmic.2018.05.007DOI Listing
July 2018

Genome-Wide Comparative Functional Analyses Reveal Adaptations of sv. Newport to a Plant Colonization Lifestyle.

Front Microbiol 2018 18;9:877. Epub 2018 May 18.

Soil and Water Sciences Department, University of Florida, Gainesville, FL, United States.

Outbreaks of salmonellosis linked to the consumption of vegetables have been disproportionately associated with strains of serovar Newport. We tested the hypothesis that strains of sv. Newport have evolved unique adaptations to persistence in plants that are not shared by strains of other serovars. We used a genome-wide mutant screen to compare growth in tomato fruit of a sv. Newport strain from an outbreak traced to tomatoes, and a sv. Typhimurium strain from animals. Most genes in the sv. Newport strain that were selected during persistence in tomatoes were shared with, and similarly selected in, the sv. Typhimurium strain. Many of their functions are linked to central metabolism, including amino acid biosynthetic pathways, iron acquisition, and maintenance of cell structure. One exception was a greater need for the core genes involved in purine metabolism in sv. Typhimurium than in sv. Newport. We discovered a gene, , that was unique to sv. Newport and contributed to the strain's fitness in tomatoes. The gene was present in about 25% of sv. Newport Group III genomes and generally absent from other genomes. Homologs of were detected in the genomes of , and , members of the Enterobacteriacea family that can colonize both plants and animals.
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http://dx.doi.org/10.3389/fmicb.2018.00877DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968271PMC
May 2018

Genes affecting progression of bacteriophage P22 infection in Salmonella identified by transposon and single gene deletion screens.

Mol Microbiol 2018 05 30;108(3):288-305. Epub 2018 Mar 30.

Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA.

Bacteriophages rely on their hosts for replication, and many host genes critically determine either viral progeny production or host success via phage resistance. A random insertion transposon library of 240,000 mutants in Salmonella enterica serovar Typhimurium was used to monitor effects of individual bacterial gene disruptions on bacteriophage P22 lytic infection. These experiments revealed candidate host genes that alter the timing of phage P22 propagation. Using a False Discovery Rate of < 0.1, mutations in 235 host genes either blocked or delayed progression of P22 lytic infection, including many genes for which this role was previously unknown. Mutations in 77 genes reduced the survival time of host DNA after infection, including mutations in genes for enterobacterial common antigen (ECA) synthesis and osmoregulated periplasmic glucan (OPG). We also screened over 2000 Salmonella single gene deletion mutants to identify genes that impacted either plaque formation or culture growth rates. The gene encoding the periplasmic membrane protein YajC was newly found to be essential for P22 infection. Targeted mutagenesis of yajC shows that an essentially full-length protein is required for function, and potassium efflux measurements demonstrated that YajC is critical for phage DNA ejection across the cytoplasmic membrane.
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http://dx.doi.org/10.1111/mmi.13936DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5912970PMC
May 2018

Interactions of Salmonella enterica Serovar Typhimurium and Pectobacterium carotovorum within a Tomato Soft Rot.

Appl Environ Microbiol 2018 03 14;84(5). Epub 2018 Feb 14.

Soil and Water Science Department, Genetics Institute, University of Florida-IFAS, Gainesville, Florida, USA.

spp. are remarkably adaptable pathogens, and this adaptability allows these bacteria to thrive in a variety of environments and hosts. The mechanisms with which these pathogens establish within a niche amid the native microbiota remain poorly understood. Here, we aimed to uncover the mechanisms that enable serovar Typhimurium strain ATCC 14028 to benefit from the degradation of plant tissue by a soft rot plant pathogen, The hypothesis that in the soft rot, the liberation of starch (not utilized by ) makes this polymer available to spp., thus allowing it to colonize soft rots, was tested first and proven null. To identify the functions involved in soft rot colonization, we carried out transposon insertion sequencing coupled with the phenotypic characterization of the mutants. The data indicate that spp. experience a metabolic shift in response to the changes in the environment brought on by spp. and likely coordinated by the small regulatory RNA. While and appear to be of importance in the soft rot, the global two-component system encoded by (which controls and under laboratory conditions) does not appear to be necessary for the observed phenotype. Motility and the synthesis of nucleotides and amino acids play critical roles in the growth of spp. in the soft rot. Outbreaks of produce-associated illness continue to be a food safety concern. Earlier studies demonstrated that the presence of phytopathogens on produce was a significant risk factor associated with increased carriage on fruits and vegetables. Here, we genetically characterize some of the requirements for interactions between and phytobacteria that allow spp. to establish a niche within an alternate host (tomato). Pathways necessary for nucleotide synthesis, amino acid synthesis, and motility are identified as contributors to the persistence of spp. in soft rots.
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http://dx.doi.org/10.1128/AEM.01913-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5812938PMC
March 2018

Salmonella Persistence in Tomatoes Requires a Distinct Set of Metabolic Functions Identified by Transposon Insertion Sequencing.

Appl Environ Microbiol 2017 03 15;83(5). Epub 2017 Feb 15.

Soil and Water Science Department, Genetics Institute, University of Florida-IFAS, Gainesville, Florida, USA.

Human enteric pathogens, such as spp. and verotoxigenic , are increasingly recognized as causes of gastroenteritis outbreaks associated with the consumption of fruits and vegetables. Persistence in plants represents an important part of the life cycle of these pathogens. The identification of the full complement of genes involved in the colonization of the model plant (tomato) was carried out using transposon insertion sequencing analysis. With this approach, 230,000 transposon insertions were screened in tomato pericarps to identify loci with reduction in fitness, followed by validation of the screen results using competition assays of the isogenic mutants against the wild type. A comparison with studies in animals revealed a distinct plant-associated set of genes, which only partially overlaps with the genes required to elicit disease in animals. biosynthesis of amino acids was critical to persistence within tomatoes, while amino acid scavenging was prevalent in animal infections. Fitness reduction of the amino acid synthesis mutants was generally more severe in the tomato mutant, which hyperaccumulates certain amino acids, suggesting that these nutrients remain unavailable to spp. within plants. lipopolysaccharide (LPS) was required for persistence in both animals and plants, exemplifying some shared pathogenesis-related mechanisms in animal and plant hosts. Similarly to phytopathogens, spp. required biosynthesis of amino acids, LPS, and nucleotides to colonize tomatoes. Overall, however, it appears that while shares some strategies with phytopathogens and taps into its animal virulence-related functions, colonization of tomatoes represents a distinct strategy, highlighting this pathogen's flexible metabolism. Outbreaks of gastroenteritis caused by human pathogens have been increasingly associated with foods of plant origin, with tomatoes being one of the common culprits. Recent studies also suggest that these human pathogens can use plants as alternate hosts as a part of their life cycle. While dual (animal/plant) lifestyles of other members of the family are well known, the strategies with which colonizes plants are only partially understood. Therefore, we undertook a high-throughput characterization of the functions required for persistence within tomatoes. The results of this study were compared with what is known about genes required for virulence in animals and interactions of plant pathogens with their hosts to determine whether repurposes its virulence repertoire inside plants or whether it behaves more as a phytopathogen during plant colonization. Even though utilized some of its virulence-related genes in tomatoes, plant colonization required a distinct set of functions.
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http://dx.doi.org/10.1128/AEM.03028-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5311394PMC
March 2017

Defined single-gene and multi-gene deletion mutant collections in Salmonella enterica sv Typhimurium.

PLoS One 2014 9;9(7):e99820. Epub 2014 Jul 9.

Department of Microbiology and Molecular Genetics, University of California Irvine, Irvine, California, United States of America.

We constructed two collections of targeted single gene deletion (SGD) mutants and two collections of targeted multi-gene deletion (MGD) mutants in Salmonella enterica sv Typhimurium 14028s. The SGD mutant collections contain (1), 3517 mutants in which a single gene is replaced by a cassette containing a kanamycin resistance (KanR) gene oriented in the sense direction (SGD-K), and (2), 3376 mutants with a chloramphenicol resistance gene (CamR) oriented in the antisense direction (SGD-C). A combined total of 3773 individual genes were deleted across these SGD collections. The MGD collections contain mutants bearing deletions of contiguous regions of three or more genes and include (3), 198 mutants spanning 2543 genes replaced by a KanR cassette (MGD-K), and (4), 251 mutants spanning 2799 genes replaced by a CamR cassette (MGD-C). Overall, 3476 genes were deleted in at least one MGD collection. The collections with different antibiotic markers permit construction of all viable combinations of mutants in the same background. Together, the libraries allow hierarchical screening of MGDs for different phenotypic followed by screening of SGDs within the target MGD regions. The mutants of these collections are stored at BEI Resources (www.beiresources.org) and publicly available.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0099820PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4089911PMC
January 2016

Evaluation of four cell lines for assay of infectious adenoviruses in water samples.

J Water Health 2009 Dec;7(4):650-6

Civil and Environmental Engineering, University of California, 1367 SEII, Irvine, CA 92697, USA.

Human viral contamination in drinking and recreational waters poses health risks. The application of PCR-based molecular technology has advanced our knowledge of the occurrence and prevalence of human viruses in water; however, it has provided no information on viral viability and infectivity. Four human cell lines were compared for their sensitivity to different serotypes of human adenoviruses using the TCID50 test. The sensitivity of each cell line varied with different serotypes of adenovirus. Human embryonic kidney cell line 293A and human lung carcinoma cell line A549 were the most sensitive, especially to enteric adenovirus 40 and 41. Plaque assay of primary sewage samples showed 293A can detect viral plaques in 7 of 13 primary sewage samples tested. Adenoviruses were also isolated using 293A from environmental water concentrates. Cloning and sequencing of environmental adenoviral isolates indentified them to be aligned with adenoviruses serotype 40 and serotype 5. The result of this study suggests that plaque assay with 293A cell line is suitable for detection of adenovirus in the aquatic environment. Combining this cell culture with molecular methods for viral assay in the aquatic environment will provide critical information for risk assessment.
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http://dx.doi.org/10.2166/wh.2009.088DOI Listing
December 2009

Seasonal detection of human viruses and coliphage in Newport Bay, California.

Appl Environ Microbiol 2007 Oct 24;73(20):6468-74. Epub 2007 Aug 24.

Civil and Environmental Engineering, 1367 SE II, University of California, Irvine, CA 92697, USA.

Recent studies have shown that the fecal indicator bacteria (FIB) currently used to indicate water quality in the coastal environment may be inadequate to reflect human viral contamination. Coliphage was suggested as a better indicator of human viral pollution and was proposed by the U.S. EPA as an alternative indicator for fecal pollution in groundwater. In this study, we investigated the occurrence and distribution of FIB, F+ coliphage, and PCR-detectable human adenovirus and enterovirus for an entire year at 15 locations around the Newport Bay watershed, an important southern California estuary for water recreation and an ecological reserve. Peak concentrations and prevalences of FIB and F+ coliphage were associated with winter storms (wet weather). Human adenoviruses and enteroviruses, however, were detected by PCR in approximately 5% of samples collected in the summer (dry weather) but only once in wet weather. These results demonstrated that FIB and coliphage have similar seasonal and freshwater-to-saltwater distribution patterns, while the detection of human viruses depends on a distribution pattern that is the opposite of that of FIB and coliphage. This research suggested that coliphage and FIB share similar environmental sources, while sources of human viruses in Newport Bay are perhaps different.
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http://dx.doi.org/10.1128/AEM.01370-07DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2075071PMC
October 2007

Microbial source tracking in a small southern California urban watershed indicates wild animals and growth as the source of fecal bacteria.

Appl Microbiol Biotechnol 2007 Sep 23;76(4):927-34. Epub 2007 Jun 23.

Civil and Environmental Engineering, University of California, Irvine, CA 92697, USA.

Three independent microbial source tracking (MST) methods were applied to a small urban subwatershed in Orange County, California. Fifty-seven water samples collected over summer 2002 were analyzed for human adenovirus and enterovirus. Enterococci and E. coli were isolated for antibiotic resistance analysis (ARA) and for PCR identification of human- and animal-specific toxin genes, respectively. All water samples were PCR negative for human enteroviruses and E. coli human-specific toxin gene. E. coli toxin markers revealed the presence of toxin genes specific to bird, rabbit, and cow. Enterococci ARA results supported this conclusion and indicated that fecal bacteria from bird and wild animal feces as well as soil were the predominant source found in the watershed. An E. coli, isolated from the watershed and inoculated back into the heat-sterilized storm drain water, increased 4 log units within 6 days. Collectively, these results suggest that bird and wild animal feces, soil amendments, and/or fecal coliform growth in the storm drain are the major contributors to the fecal bacterial pollution in downstream areas. However, human adenoviruses were detected on two occasions. Fecal bacterial concentrations were not elevated on these two occasions, suggesting that the elevated levels of fecal indicator bacteria in this small watershed could be unrelated to the source of human adenovirus.
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http://dx.doi.org/10.1007/s00253-007-1047-0DOI Listing
September 2007

Isolation and genetic analysis of haloalkaliphilic bacteriophages in a North American Soda Lake.

Microb Ecol 2006 May 6;51(4):543-54. Epub 2006 May 6.

Department of Environmental Health, Science, & Policy, University of California, Irvine, CA 92697-7070, USA.

Mono Lake is a meromictic, hypersaline, soda lake that harbors a diverse and abundant microbial community. A previous report documented the high viral abundance in Mono Lake, and pulsed-field gel electrophoresis analysis of viral DNA from lake water samples showed a diverse population based on a broad range of viral genome sizes. To better understand the ecology of bacteriophages and their hosts in this unique environment, water samples were collected between February 2001 and July 2004 for isolation of bacteriophages by using four indigenous bacterial hosts. Plaque assay results showed a differential seasonal expression of cultured bacteriophages. To reveal the diversity of uncultured bacteriophages, viral DNA from lake water samples was used to construct clone libraries. Sequence analysis of viral clones revealed homology to viral as well as bacterial proteins. Furthermore, dot blot DNA hybridization analyses showed that the uncultured viruses are more prevalent during most seasons, whereas the viral isolates (Aphi and phi2) were less prevalent, confirming the belief that uncultured viruses represent the dominant members of the community, whereas cultured isolates represent the minority species.
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http://dx.doi.org/10.1007/s00248-006-9069-1DOI Listing
May 2006

Real-time quantitative PCR for enteric adenovirus serotype 40 in environmental waters.

Can J Microbiol 2005 May;51(5):393-8

Department of Environmental Health, Science, and Policy, University of California, Irvine 92697, USA.

Adenoviruses 40 and 41 have been recognized as important etiological agents of gastroenteritis in children. A real-time PCR method (TaqMan assay) was developed for rapid quantification of adenovirus 40 (Ad40) by amplifying an 88 bp sequence from the hexon gene. To establish a quantification standard curve, a 1090 bp hexon region of Ad40 was amplified and cloned into the pGEM-T Vector. A direct correlation was observed between the fluorescence threshold cycle number (Ct) and the starting quantity of Ad40 hexon gene. The quantification was linear over 6-log units and the amplification efficiency averaged greater than 95%. Seeding studies using various environmental matrices (including sterile water, creek water, brackish estuarine water, ocean water, and secondary sewage effluent) suggest that this method is applicable to environmental samples. However, real-time PCR was sensitive to inhibitors present in the environmental samples. Lower efficiency of PCR amplification was found in secondary sewage effluent and creek waters. Application of the method to fecal contaminated waters successfully quantified the presence of Ad40. The sensitivity of the real-time PCR is comparable to the traditional nested PCR assay for environmental samples. In addition, the real-time PCR assay offers the advantage of speed and insensitivity to contamination during PCR set up. The real-time PCR assay developed in this study is suitable for quantitative determination of Ad40 in environmental samples and represents a considerable advancement in pathogen quantification in aquatic environments.
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http://dx.doi.org/10.1139/w05-016DOI Listing
May 2005

Use of viral pathogens and indicators to differentiate between human and non-human fecal contamination in a microbial source tracking comparison study.

J Water Health 2003 Dec;1(4):195-207

UNC-Chapel Hill Institute of Marine Sciences, Morehead City, NC 28557, USA.

Assays for the detection and typing of adenoviruses, enteroviruses and F+ specific coliphages were performed on samples created as part of a national microbial source tracking methods comparison study. The samples were created blind to the researchers, and were inoculated with a variety of types of fecal contamination source (human, sewage, dog, seagull and cow) and mixtures of sources. Viral tracer and pathogen assays demonstrated a general ability to discriminate human from non-human fecal contamination. For example, samples inoculated with sewage were correctly identified as containing human fecal contamination because they contained human adenovirus or human enterovirus. In samples containing fecal material from individual humans, human pathogen analysis yielded negative results probably because the stool samples were taken from healthy individuals. False positive rates for the virus-based methods (0-8%) were among the lowest observed during the methods comparison study. It is suggested that virus-based source tracking methods are useful for identification of sewage contamination, and that these methods may also be useful as an indication of the public health risk associated with viral pathogens. Overall, virus-based source tracking methods are an important approach to include in the microbial source tracking 'toolbox'.
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December 2003

Prevalence of cholera toxin genes (ctxA and zot) among non-O1/O139 Vibrio cholerae strains from Newport Bay, California.

Appl Environ Microbiol 2003 Dec;69(12):7541-4

Environmental Health, Science and Policy, University of California, Irvine, California 92697, USA.

The examination of 137 non-O1/O139 Vibrio cholerae isolates from Newport Bay, California, indicated the presence of diverse genotypes and a temporal succession. Unexpectedly, the cholera toxin gene (ctxA) was found in 17% of the strains, of which one-third were also positive for the zot gene. This suggests that ctxA is prevalent in the region of nonepidemicity and is likely to have an environmental origin.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC309920PMC
http://dx.doi.org/10.1128/aem.69.12.7541-7544.2003DOI Listing
December 2003

Application of enterococci antibiotic resistance patterns for contamination source identification at Huntington Beach, California.

Mar Pollut Bull 2003 Jun;46(6):748-55

Department of Environmental Analysis and Design, University of California, 1367 SE II, Irvine, CA 92697, USA.

Huntington Beach, California, one of the most popular surfing spots in the world, is plagued by sporadic, elevated levels of fecal bacteria. To assist with pollution source identification, we analyzed antibiotic resistance patterns (ARPs) of enterococci from four known sources (bird feces, urban runoff, coastal marsh sediment and sewage effluent from local sanitation district) and one unknown source (seawater) using seven antibiotics at four concentrations each. Of 2491 enterococci tested, all were resistant to at least one antibiotic at some level. Discriminant analysis indicated that the average correct classification rates for bird feces and urban runoff sources were above 80%. Sewage effluent contained mixed fecal sources. Sixty-four percent of the sewage isolates classified with the sewage category, while the other 35% of isolates were assigned evenly across the other three categories. When enterococci isolated from the seawater were classified using the known ARP database, it was evident that bird feces were the source of surf zone contamination on some days while the coastal salt marsh and sewage plume may have impacted the surf zone water quality to various degrees during other times.
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http://dx.doi.org/10.1016/S0025-326X(03)00046-8DOI Listing
June 2003