Comparison of Five Selective Enrichment Broths and Two Selective Agars For Recovery of Vibrio vulnificus From Oysters

The Bacteriological Analytical Manual (6th edition) specifies use of glucose-salt-teepol (GST) broth for detection of Vibrio vulnificus and other halophilic vibrios in seafood. Since teepol is no longer commercially available, this study compared five enrichment broths for their ability to recover V. vulnificus . Ten samples of seeded oysters were analyzed using a three-tube MPN and enriched in each of five broths in duplicate. Broth cultures were then streaked onto cellobiose-polymyxin B-colistin (CPC) agar and sodium dodecyl sulfate-polymyxin B-sucrose (SDS) agar plates. Average (± standard error) recovery (log MPN/g) from each broth was as follows: Alkaline-peptone-water (APW), 4.16 ± 0.20; Marine (MRN) broth, 3.63 ± 0.16; Horie's broth, 2.88 ± 0.17; Monsur's broth, 2.43 ± 0.16; and GST broth, 1.28 ± 0.28. APW and MRN broths yielded significantly (P<0.05) higher recovery than other broths by the Kruskal-Wallis nonparametric rank test. Vibrio vulnificus was isolated with higher frequency from CPC (81%) as compared with SDS (61%) agar plates. Background growth was minimal on CPC agar, facilitating selection of V. vulnificus colonies. Based on these results, APW enrichment broth and CPC isolation agar were more efficient for recovery of V. vulnificus from oysters than other broth and agar combinations.