Abstract:
Inspection of food for the presence of Salmonella is a major concern in food
industry. Many rapid, reliable and sensitive novel methods have been developed to
detect Salmonella from food samples. However a method to detect live bacterial
cells separately from dead cells yet to be developed. Although fluorescent in situ
hybridization (FISH) has been identified as promising method in this regards, the
viable count could be overestimated by FISH technique due to dead cells with some
amount of non degraded rRNA. Some times it could be underestimated because
of inactive but viable cells which not produce detectable amount of rRNA. The
possibility of using antibiotic treatment step in FISH technique to overcome this
problem was studied. Chicken samples inoculated by differently prepared mixtures
of live and heat killed Salmonella enterica cultures were used to isolate bacterial cells
with and without antibiotic treatment (Nalidixic acid 10μg/ml and Ciprofloxacin 1μg/
ml for 2h at 370
C). FISH was performed with Salmonella specific 23S rRNA probe
Sal3, 5’-AATCACTTCACCTACGTG-3’ labeled with fluorescein isothiocyanate
(FITC) at 5’ end. Cells observed with high intensity under fluorescent microscope
were identified as live cells. Results of statistical analysis for antibiotic treated and
untreated samples indicated that the introduction of antibiotic treatment step in FISH
technique permitted a successful application to over come the problem associated
with viable Salmonella enterica detection and quantification.
