Evaluation of enrichment media for improved PCR-based detection of V. cholerae and V. vulnificus from estuarine water and plankton

Aims: Pathogenic Vibrio spp., including V. cholerae and V. vulnificus, are commonly found along the estuaries of the south-east United States; however, it is often difficult to recover these species directly from environmental samples. Pre-enrichment assays are commonly used to improve the detection of pathogenic vibrios from environmental sources. Here, we evaluated a novel enrichment procedure using freshly collected and autoclaved natural estuarine water amended with 1% peptone (designated as estuarine peptone water, EPW) and compared it to traditional alkaline peptone water (APW) for detection by PCR of V. cholerae and V. vulnificus. Methods and Results: Of the 50 samples collected in total, V. cholerae DNA was detected in APW 10% of the time and in EPW 40% of the time. Likewise, the cholera toxin gene (ctxA) was detected in 4 vs 18% of the samples using APW and EPW, respectively. Conversely, APW showed improved recovery for V. vulnificus relative to EPW with respective detection frequencies of 46 and 20%. Results showed similar patterns across different sample types (water and plankton). Conclusions: While enrichment in traditional APW was adequate for the recovery of Vibrio vulnificius, use of sterile estuarine water amended with peptone significantly improved the detection of V. cholerae and the virulence gene ctxA from estuarine sources.