title: Specific detection of viable Listeria monocytogenes in Spanish wastewater treatment plants by Fluorescent In Situ Hybridization and PCR.
abstract: Listeria monocytogenes detection in wastewater can be difficult because of the large amount of background microbiota and the presence of viable but non-culturable forms in this environment. The aim of this study was to evaluate a Fluorescent In Situ Hybridization (FISH) assay combined with Direct Viable Count (DVC) method for detecting viable L. monocytogenes in wastewater samples, as an alternative to conventional culture methods. 16S rRNA sequence data were used to design a specific oligonucleotide probe. In order to assess the suitability of the method, the assays were performed on naturally (n=87) and artificially (n=14) contaminated samples and results were compared to those obtained with the isolation of cells on selective media and with a PCR method. The detection limit of FISH and PCR assays was 10(4) cells/mL without enrichment and 10 cells/mL after enrichment. A total of 47 samples, including 3 samples from effluent sites, yielded FISH positive results for L. monocytogenes. Using DVC-FISH technique, the presence of viable L. monocytogenes cells was detected in 23 out of these 47 FISH positive wastewater samples. PCR and culture methods yielded 27 and 23 positive results, respectively. According to these results, FISH technique has the potential to be used as a sensitive method for the detection and enumeration of L. monocytogenes in environmental wastewater samples.
authors.affiliation: Departamento de Biotecnología, Universidad Politécnica de Valencia, Camino de Vera 14, 46022 Valencia, Spain.
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Moreno
authors.forename: Lorena
authors.initials: L
authors.lastname: Ballesteros
authors.forename: Jorge
authors.initials: J
authors.lastname: García-Hernández
authors.forename: Paula
authors.initials: P
authors.lastname: Santiago
authors.forename: Ana
authors.initials: A
authors.lastname: González
authors.forename: M Antonia
authors.initials: MA
authors.lastname: Ferrús
mesh_terms: D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods*; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D007220:Industrial Waste / Q000032:analysis; D008089:Listeria monocytogenes / Q000235:genetics / Q000302:isolation & purification*; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D007220:Industrial Waste; D012336:RNA, Ribosomal, 16S