title: Strategies for recovering of planktonic and sessile cells of Escherichia coli O157:H7 from freshwater environment.
abstract: The experiments were performed with Escherichia coli O157:H7 EDL 933 in freshwater microcosms at 12 °C. At 35, 45, and 70 days, samples were taken and filtered through 0.45 μm membrane filters. The following alternatives were tested to evaluate the recovery percentage of injured cells: (1) selective media CHROMagar(™)O157 and chromID(™)O157:H7 agar, at 37 °C for 24 h; (2) tryptic soy agar supplemented with yeast extract (TSAE), incubated at 25 °C for 2 or 4 h, then transferred to CHROMagar(™)O157 or chromID(™)O157:H7 agar at 37 °C (TSAE2h-CHROM, TSAE4h-CHROM and TSAE2h-ID, TSAE4h-ID); (3) thin agar layer (TAL) method, TSAE was overlaid on CHROMagar(™)O157 or chromID(™)O157:H7 agar (TALCHROM and TALID, respectively) and incubated at 37 °C for 24 h; and (4) TALCHROM at 25 °C for 4 h, then continued up to complete 24 h at 37 °C (TALCHROM4h). Furthermore, the recovery of E. coli O157:H7 cells adhering to glass coverslips were evaluated to mimic biofilm conditions. The recovery percentages obtained from each alternative were calculated relative to TSAE counts. After 70 days, TSAE4h-CHROM and TALCHROM4h showed the highest recovery percentage (>90 %) from water microcosms. Despite the improved recovery of cell adhering to glass surfaces, the percentages obtained with TSAE4h-CHROM were low. Further studies for the recovery of biofilm-forming E. coli O157:H7 are required. Pre-incubation on TSAE at 25 °C for 4 h, combined with CHROMagar(™)O157, or by thin agar layer method (TALCHROM) enhanced significantly the recovery of viable cells of E. coli O157:H7 after prolonged stay in water microcosms.
authors.affiliation: Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, San Juan 670, 8000, Bahía Blanca, Argentina.
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Marucci
authors.affiliation: Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, San Juan 670, 8000, Bahía Blanca, Argentina. mcubitto@criba.edu.ar.|Centro de Recursos Naturales Renovables de la Zona Semiárida (CERZOS, UNS-CONICET), Bahía Blanca, Argentina. mcubitto@criba.edu.ar.
authors.forename: María A
authors.initials: MA
authors.lastname: Cubitto
mesh_terms: D000362:Agar; D018441:Biofilms / Q000254:growth & development; D003470:Culture Media; D004784:Environmental Monitoring / Q000379:methods*; D019453:Escherichia coli O157 / Q000302:isolation & purification*; D005618:Fresh Water / Q000382:microbiology*; D060587:Groundwater / Q000382:microbiology*; D059013:Microbial Consortia; D010933:Plankton / Q000302:isolation & purification*
chemical_list: D003470:Culture Media; D000362:Agar
keywords: Culturability; Escherichia coli O157:H7; Freshwater; Injured; Recovery; Stressed