Article Figures & Data
Figures
- FIG. 1.
Cluster analysis of L. monocytogenes isolates along with phenotypic characteristics. PFGE was performed after genomic DNA was digested with ApaI (A) or AscI (B) using the CDC PulseNet standardized procedure (11). Digestion patterns for both restriction enzymes were used to determine PFGE types (PFGE types P1 to P31 in panel A). PCR-based serotype groups are indicated by brown [serotype group 1/2a(3a)], violet [serotype group 4b(d,e)], and blue [serotype group 1/2b(3b)]. The box between the two panels indicates antibiotic resistance (T, tetracycline; C, carbenicillin; S, sulfomethoxazole) and an inability to induce glutamate-dependent acid resistance under aerobic conditions (X). Susceptibility to the listeriophage cocktail was expressed as the number of PFU generated per ml by individual isolates and is indicated as follows: yellow, 0 to 101 PFU/ml; blue, 102 to 104 PFU/ml; green, 105 to 106 PFU/ml; and red, >107 PFU/ml.
Tables
- TABLE 1.
Listeriophage susceptibility and glutamate-dependent acid resistance phenotypes of serotype group 4b(d,e) isolatesa
Strain (isolation date) Pulse type Phage susceptibility (PFU/ml) Glutamate-dependent acid resistance (% survival) ATCC 13932 ND 3.1 × 107 ± 0.8 × 107 7.6 ± 0.91 ATCC 19115 ND 4.4 × 107 ± 0.8 × 107 4.4 ± 0.84 FL9 (6 March 2003) P16 R 7.75 ± 2.6 FL24 (12 June 2003) P14 5.2 × 107 ± 0.6 × 107 0.145 ± 0.02 FL25 (18 June 2003) P15 R 2.5 ± 0.26 FL26 (18 June 2003) P15 R 2.7 ± 0.33 FL27 (18 June 2003) P15 R 2.45 ± 1.2 FL59 (14 October 2003) P17 R 0.33 ± 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.
- TABLE 2.
Differentiation of food-borne isolates belonging to pulse type P13 based on antibiotic and listeriophage susceptibility phenotypesa
Strain Date of isolation Antibiotic resistance Phage susceptibility FL4 13 February 2003 2.9 × 108 ± 2.8 × 108 FL5 21 February 2003 3.1 × 108 ± 2.5 × 108 FL67 6 November 2003 1.3 × 107 ± 1.0 × 107 FL68 6 November 2003 1.7 × 106 ± 0.3 × 106 FL69 6 November 2003 3.6 × 106 ± 1.0 × 106 FL84 11 December 2003 Sulfomethoxazole 2.4 × 106 ± 0.6 × 106 ↵a Tests to determine susceptibility to the listeriophage cocktail were performed three to five times, and the results are expressed as means ± standard deviations.
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Files in this Data Supplement:
- Supplemental file 1
-
Supplemental material (Additional information on food sample collection).
Excel document, 23K.
- Supplemental file 1
-
Supplemental material (Additional information on food sample collection).
