Detection of Pathogenic Serogroups and Virulence Genes in Listeria monocytogenes Strains Isolated from Beef and Beef Products Retailed in Gauteng Province, South Africa, Using Phenotypic and Polymerase Chain Reaction (PCR)-Based Methods
Table 1
Prevalence of L. monocytogenes, L. innocua, and L. welshimeri in beef and beef products, and univariate analysis of associated factors.
Variable
Level
No. of samples tested
No. (%) of samples positive for:
L. monocytogenes1
L. innocua2
L. welshineri3
Region
Pretoria North
80
10 (12.5)
10 (12.5)
2 (2.5)
Pretoria East
90
10 (11.1)
15 (16.7)
0 (0.0)
Pretoria West
76
9 (11.8)
12 (15.8)
2 (2.6)
Pretoria South
79
1 (1.3)
18 (22.8)
3 (3.8)
Pretoria Central
75
7 (9.3)
10 (13.3)
3 (4.0)
value
0.036
0.434
0.461
Type of outlet4
Supermarket chain
115
12 (10.4)
15 (13.0)
1 (0.9)
Large
108
7 (6.5)
8 (7.4)
4 (3.7)
Medium
107
7 (6.5)
18 (16.8)
3 (2.8)
Small
70
11 (15.7)
13 (18.6)
2 (2.9)
value
0.133
0.726
0.598
Type of product
Beef burger
40
0 (0.0)
5 (12.5)
0 (0.0)
Biltong
55
2 (3.6)
7 (12.7)
1 (1.8)
Minced beef
110
16 (14.5)
21 (19.1)
2 (1.8)
Brisket
120
12 (10.0)
22 (18.3)
7 (5.8)
Cold beef (deli)
75
7 (9.3)
10 (13.3)
0 (0.0)
value
0.032
0.674
0.112
Storage temperature
Non-chilled5
55
3 (5.5)
6 (10.9)
1 (1.8)
Chilled
220
29 (13.2)
51 (23.2)
8 (3.6)
Frozen
125
5 (4.0)
8 (6.4)
1 (0.8)
value
0.011
<0.001
0.252
Status of the product
RTE6
130
9 (6.9)
15 (11.5)
1 (0.8)
Raw
270
28 (10.4)
50 (18.5)
9 (3.3)
value
0.265
0.076
0.177
1The overall prevalence of L. monocytogenes was 9.3% (37/400); the 2overall prevalence of L. innocua was 16.3% (65/400), and the 3overall prevalence of L. welshimeri was 2.5% (10/400); 4Supermarket chain: Over one outlet, Large: 6 or more Cashiers, Medium: 3–5 cashiers, and Small: 1-2 cashiers, 5At room temperature, 6RTE: Ready-to-eat; deli beef: (“Polony” and Vienna).
