TABLE 2.
Recovery of V. parahaemolyticus VP47, VP87, and VP41 inoculated into APW containing seafood by the K6-specific immunomagnetic separation method with or without enrichment culture of the IMP
| Seafood sample and enrichment culture | Recoverya (no. of colonies) of inoculated test strain(s):
|
||||||
|---|---|---|---|---|---|---|---|
| VP47 | VP87 | VP41 | VP47 and VP87 | VP47 and VP41 | VP47, VP87, and VP41 | None | |
| Squid | |||||||
| Direct platingb | + (7.33) | − | − | + (6.67) | + (1.33) | + (2.67) | − |
| Enrichment culture in APWc | + (29.3) | + (26.3) | + (54.7) | + (45.3) | + (65.6) | + (38.3) | − |
| Fish (Nemipterus virgatus) | |||||||
| Direct plating | + (26.0) | − | − | + (38.0) | + (20.0) | + (14.0) | − |
| Enrichment culture in APW | + (31.7) | + (7.33) | + (12.3) | + (11.0) | + (6.67) | + (38.3) | − |
| Shrimp (Penaeus monodon) | |||||||
| Direct plating | + (282) | + (0.333) | + (4.00) | + (383) | + (522) | + (285) | − |
| Enrichment culture in APW | + (10.0) | + (7.67) | + (22.3) | + (86.0) | + (56.0) | + (10.3) | − |
| Enrichment culture in SPBd | + (119) | + (28.2) | + (52.1) | + (16.9) | + (14.7) | + (92.9) | − |
+, Test strain (green colony) was recovered on TCBS agar; −, test strain (green colony) was not recovered on TCBS agar. The numbers of green colonies recovered per TCBS agar plate (average of three plates) are shown in the parentheses. When mixed test strains were inoculated, all green colonies were found to be VP47 (as explained in the text).
Enrichment culture of IMP was not performed. A 1-ml portion of the supernatant of the APW-seafood mixture containing VP47 was treated with IMS, and one-tenth of the IMS suspension was directly streaked onto TCBS agar.
The IMP suspension was prepared as for the direct plating method. Four-tenths of the IMS suspension was incubated in 5 ml of APW at pH 8.6 overnight at 37°C. A 50-μl portion of the 105-fold dilution of the enrichment culture was inoculated onto TCBS agar so that VP47 could be recovered as isolated colonies.
The IMP suspension was prepared as described for the direct plating method. Four-tenths of the IMS suspension was incubated in 5 ml of salt polymyxin broth overnight at 37°C. A 50-μl portion of the 105-fold dilution of the enrichment culture was inoculated onto TCBS agar so that VP47 could be recovered as isolated colonies.