Strategies for recovering of planktonic and sessile cells of Escherichia coli O157:H7

CUBITTO MARÍA AMELIA; MARUCCI PATRICIA LILIANA

ENVIRONMENTAL MONITORING AND ASSESSMENT

SPRINGER

Lugar: Berlin; Año: 2016 p. 432 - 441

0167-6369

The experiments were performed withEscherichia coli O157:H7 EDL 933 in freshwater microcosmsat 12 °C. At 35, 45, and 70 days, samples weretaken and filtered through 0.45 μm membrane filters.The following alternatives were tested to evaluate therecovery percentage of injured cells: (1) selective mediaCHROMagar?O157 and chromID?O157:H7 agar, at37 °C for 24 h; (2) tryptic soy agar supplemented withyeast extract (TSAE), incubated at 25 °C for 2 or 4 h,then t ransferred to CHROMagar?O157 orchromID?O157:H7 agar at 37 °C (TSAE2h-CHROM,TSAE4h-CHROM and TSAE2h-ID, TSAE4h-ID); (3)thin agar layer (TAL) method, TSAE was overlaid onCHROMagar?O157 or chromID?O157:H7 agar(TALCHROM and TALID, respectively) and incubatedat 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. coliO157:H7 cells adhering to glass coverslips were evaluatedto mimic biofilm conditions. The recovery percentagesobtained from each alternative were calculatedrelative to TSAE counts. After 70 days, TSAE4h-CHROM and TALCHROM4h showed the highest recoverypercentage (>90 %) from water microcosms.Despite the improved recovery of cell adhering to glasssurfaces, the percentages obtained with TSAE4h-CHROM were low. Further studies for the recovery ofbiofilm-forming E. coli O157:H7 are required. Preincubationon TSAE at 25 °C for 4 h, combined withCHROMagar?O157, or by thin agar layer method(TALCHROM) enhanced significantly the recovery ofviable cells of E. coli O157:H7 after prolonged stay inwater microcosms