title: Integrated analysis of established and novel microbial and chemical methods for microbial source tracking.
abstract: Several microbes and chemicals have been considered as potential tracers to identify fecal sources in the environment. However, to date, no one approach has been shown to accurately identify the origins of fecal pollution in aquatic environments. In this multilaboratory study, different microbial and chemical indicators were analyzed in order to distinguish human fecal sources from nonhuman fecal sources using wastewaters and slurries from diverse geographical areas within Europe. Twenty-six parameters, which were later combined to form derived variables for statistical analyses, were obtained by performing methods that were achievable in all the participant laboratories: enumeration of fecal coliform bacteria, enterococci, clostridia, somatic coliphages, F-specific RNA phages, bacteriophages infecting Bacteroides fragilis RYC2056 and Bacteroides thetaiotaomicron GA17, and total and sorbitol-fermenting bifidobacteria; genotyping of F-specific RNA phages; biochemical phenotyping of fecal coliform bacteria and enterococci using miniaturized tests; specific detection of Bifidobacterium adolescentis and Bifidobacterium dentium; and measurement of four fecal sterols. A number of potentially useful source indicators were detected (bacteriophages infecting B. thetaiotaomicron, certain genotypes of F-specific bacteriophages, sorbitol-fermenting bifidobacteria, 24-ethylcoprostanol, and epycoprostanol), although no one source identifier alone provided 100% correct classification of the fecal source. Subsequently, 38 variables (both single and derived) were defined from the measured microbial and chemical parameters in order to find the best subset of variables to develop predictive models using the lowest possible number of measured parameters. To this end, several statistical or machine learning methods were evaluated and provided two successful predictive models based on just two variables, giving 100% correct classification: the ratio of the densities of somatic coliphages and phages infecting Bacteroides thetaiotaomicron to the density of somatic coliphages and the ratio of the densities of fecal coliform bacteria and phages infecting Bacteroides thetaiotaomicron to the density of fecal coliform bacteria. Other models with high rates of correct classification were developed, but in these cases, higher numbers of variables were required.
authors.affiliation: Department of Microbiology, University of Barcelona, Avda. Diagonal 645, Barcelona, Spain. ablanch@ub.edu
authors.forename: Anicet R
authors.initials: AR
authors.lastname: Blanch
authors.forename: Lluís
authors.initials: L
authors.lastname: Belanche-Muñoz
authors.forename: Xavier
authors.initials: X
authors.lastname: Bonjoch
authors.forename: James
authors.initials: J
authors.lastname: Ebdon
authors.forename: Christophe
authors.initials: C
authors.lastname: Gantzer
authors.forename: Francisco
authors.initials: F
authors.lastname: Lucena
authors.forename: Jakob
authors.initials: J
authors.lastname: Ottoson
authors.forename: Christos
authors.initials: C
authors.lastname: Kourtis
authors.forename: Aina
authors.initials: A
authors.lastname: Iversen
authors.forename: Inger
authors.initials: I
authors.lastname: Kühn
authors.forename: Laura
authors.initials: L
authors.lastname: Mocé
authors.forename: Maite
authors.initials: M
authors.lastname: Muniesa
authors.forename: Janine
authors.initials: J
authors.lastname: Schwartzbrod
authors.forename: Sylvain
authors.initials: S
authors.lastname: Skraber
authors.forename: Georgios T
authors.initials: GT
authors.lastname: Papageorgiou
authors.forename: Huw
authors.initials: H
authors.lastname: Taylor
authors.forename: Jessica
authors.initials: J
authors.lastname: Wallis
authors.forename: Joan
authors.initials: J
authors.lastname: Jofre
mesh_terms: D000818:Animals; D001185:Artificial Intelligence; D001435:Bacteriophages / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D004755:Enterobacteriaceae / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D016983:Enterococcus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D005060:Europe; D005243:Feces / Q000737:chemistry / Q000382:microbiology* / Q000821:virology; D006801:Humans; D008828:Microbiological Techniques; D010641:Phenotype; D013261:Sterols / Q000032:analysis; D014871:Water Microbiology
chemical_list: D013261:Sterols