Rapid propidium monoazide cPCR assay for exclusive quantification of viable Salmonella spp. cells

Area of Science:

• Microbiology
• Molecular Biology
• Food Safety

Background:

• Standard culture methods often fail to detect viable but nonculturable (VBNC) bacteria.
• Accurate enumeration of viable bacteria is crucial for food safety and risk assessment.
• Distinguishing between viable and non-viable bacterial cells is essential for accurate microbial analysis.

Purpose of the Study:

• To evaluate the efficacy of propidium monoazide (PMA) pretreatment combined with competitive polymerase chain reaction (cPCR) for enumerating viable Salmonella spp.
• To assess the ability of the PMA-cPCR method to detect viable but nonculturable (VBNC) Salmonella.
• To compare the results of PMA-cPCR with standard culture methods (SCM).

Main Methods:

• Pretreatment of bacterial samples with propidium monoazide (PMA).
• Detection of Salmonella spp. DNA using competitive polymerase chain reaction (cPCR).
• Comparison of PMA-cPCR results with standard culture methods (SCM).

Main Results:

• PMA treatment effectively prevented the detection of DNA from non-viable Salmonella cells by cPCR.
• The PMA-cPCR method successfully detected viable but nonculturable (VBNC) Salmonella spp. within 5 hours.
• SCM yielded approximately 1-2 log(10)cfu ml(-1) fewer viable cells compared to PMA-cPCR, indicating SCM's inability to detect VBNC cells.

Conclusions:

• The PMA-cPCR method accurately enumerates viable Salmonella spp., including those in the VBNC state.
• This method provides a reliable way to assess the infectious potential of VBNC bacteria.
• PMA-cPCR offers trustworthy data for evaluating control strategies and conducting risk assessments in food safety.