Evaluation of buoyant density centrifugation as a sample preparation method for NASBA-ELGA detection of Campylobacter jejuni in foods

Buoyant densities of four Campylobacter jejuni strains were in the range of 1.084-1.087 g ml(-1). Milk (3% fat) and chicken skin homogenates had buoya nt densities beneath 1.033 g ml(-1). Discontinuous buoyant density centrifu gation (BDC) in 40% Standard Isotonic BactXTractor(TM) medium respectively succeeded in recovering C. jejuni (5 x 10(3)-5 x 10(4) cfu ml(-1)) from spi ked milk (3% fat) and chicken skin. NASBA-ELGA detection of C. jejuni (5 x 10(2)-5 x 10(3) cfu ml(-1)) in 12 different food samples using four differe nt sample preparation methods was performed RNA extraction by heating (filt er and non-filter stomacher bag), RNA extraction by BDC (non-filter stomach er bag), RNA extraction by GuSCN-Triton-X- 100 lysis and silica-purificatio n (non-filter stomacher bag). BDC succeeded in overcoming inhibition of the amplification reaction except for one of the soft cheese samples. it was n oticed that fbr chicken skin, chicken meat, pork, chicken sausage, turkey m eat, milk (3% fat) and skimmed milk a simple heat treatment at 96 degrees C without any additional precautions to prevent inhibition accomplished NASB A-ELGA detection of the pathogen. The use of a filter stomacher bag improve d the quality of the NASBA-ELGA detection signal for beef but did not preve nt inhibition of the amplification reaction in the cases of ground beef pre pared minced meat, soft cheese and hard cheese. The silica purification of RNA (which was used as a control treatment) accomplished NASBA-ELGA defecti on of C. jejuni for all of the latter food homogenates (C) 1999 Academic Pr ess.