TABLE 1.

Listeriophage susceptibility and glutamate-dependent acid resistance phenotypes of serotype group 4b(d,e) isolatesa

Strain (isolation date)Pulse typePhage susceptibility (PFU/ml)Glutamate-dependent acid resistance (% survival)
ATCC 13932ND3.1 × 107 ± 0.8 × 1077.6 ± 0.91
ATCC 19115ND4.4 × 107 ± 0.8 × 1074.4 ± 0.84
FL9 (6 March 2003)P16R7.75 ± 2.6
FL24 (12 June 2003)P145.2 × 107 ± 0.6 × 1070.145 ± 0.02
FL25 (18 June 2003)P15R2.5 ± 0.26
FL26 (18 June 2003)P15R2.7 ± 0.33
FL27 (18 June 2003)P15R2.45 ± 1.2
FL59 (14 October 2003)P17R0.33 ± 0.11
  • a ND, not determined. Tests to determine the susceptibility to the listeriophage cocktail and acid shock assays were performed three to five times, and the results are expressed as means ± standard deviations. R, resistant to the listeriophage cocktail (101 to 0 PFU/ml). For the glutamate-dependent acid resistance system the percent survival was determined after acid shock in EG medium containing 1.5 mM glutamate (pH 2.5) for 1 h.