Detection and differentiation of live and heat-treated Salmonella enterica serovars inoculated onto chicken breast using Fourier transform infrared (FT-IR) spectroscopy

Abstract

Aims: To evaluate Fourier transform infrared (FT-IR) techniques for detecting, quantifying, and differentiating viable and heat-treated cells of Salmonella enterica serovars from chicken breast.

Methods and results: Salmonella enterica serovars were captured from inoculated chicken breast by filtration and immunomagnetic separation (IMS) prior to spectral collection using an FT-IR spectrometer and IR microscopy. The detection limits, based on amide II peak area (1589 to 1493 cm(-1) ), for the Filtration-FT-IR and IMS-FT-IR methods were 10(6) and 10(4) CFU g(-1) , respectively. The bacteria were detectable after 6 h of culture enrichment during a sensitivity experiment with lower initial inoculum of 10(1) CFU g(-1) . Canonical variate analysis differentiated experimental from control spectra at a level of 10(3) CFU g(-1) . Partial least squares models were established for the quantification of Salm. enterica from chicken breast using Filtration-FT-IR (R(2) ≥ 0·95, RMSEC ≤ 0·62) and IMS-FT-IR (R(2) ≥ 0·80, RMSEC ≤ 1·61) methods. Filtration-FT-IR was also used to detect and quantify live Salm. enterica in the presence of heat-treated cells with R(2) = 0·996, and this approach was comparable to the results of a commercial stain (BacLight™; R(2) = 0·998). Discriminant and canonical variate analyses of the spectra differentiated live and dead cells of different serovars of Salm. enterica.

Conclusions: FT-IR analysis coupled with separation methods is useful for the rapid detection and differentiation of Salm. enterica separated from chicken.

Significance and impact of the study: FT-IR-based methods are faster than traditional microbiological methods and can be used for the detection of live and dead bacteria from complex foods.