Staphylococcal Gastroenteritis 555
Table 23–6 D and z Values for the Thermal Destruction of S. aureus 196E in Various Heating
Menstra at 140
◦ F
Products
D(F)
Z
Reference
Chicken `
a la king
5.37
10.5
6
Custard
7.82
10.5
6
Green pea soup
6.7–6.9
8.1
107
Skim milk
3.1–3.4
9.2
107
0.5% NaCl
2.2–2.5
10.3
107
Beef bouillon
2.2–2.6
10.5
107
Skim milk alone
5.34
–
61
Raw skim milk + 10% sugar
4.11
–
61
Raw skim milk + 25% sugar
6.71
–
61
Raw skim milk + 45% sugar
15.08
–
61
Raw skim milk + 6% fat
4.27
–
61
Raw skim milk + 10% fat
4.20
–
61
Tris buffer, pH 7.2
2.0
–
53
Tris buffer, pH 7.2, 5.8% NaCl or 5% MSG
7.0
–
53
Tris buffer, pH 7.2 + 5.8% NaCl + 5% MSG
15.5
–
53
as low as 0.84 and produced SEA.
66 The production of the individual enterotoxins is more inherent to
the toxin than to the strain that produces them.
96 SEA but not SEB has been shown to be produced by
l-phase cells.
26 SEB, C, and D require a functional agr gene for maximal production. In pork, SEA
production occurred at a w of 0.86 but not at 0.83, and in beef at 0.88 but not at 0.86.
106 SEA can be
produced under conditions of a w that do not favor SEB.
110 SED has been produced at an a w of 0.86
in 6 days at 37
◦ C in BHI.
36 In general, SEB production is sensitive to a w , whereas SEC is sensitive
to both a w and temperature. Regarding NaCl and pH, enterotoxin production has been recorded at pH
4.0 in the absence of NaCl (see Table 23–2). The effect of NaCl on SEB synthesis by strain S-6 at pH
7.0 at 37
◦ C is presented in Figure 23–1.
With respect to growth temperature, SEB production in ham at 10
◦ C has been recorded,
40 as well
as small amounts of SEA, SEB, SEC, and SED in cooked ground beef, ham, and bologna at 10
◦ C.
Production has been observed at 46
◦ C, but the optimum temperature for SEB and SEC was 40
◦ C in
a protein hydrolysate medium
112 and for SEE, 40
◦ C at pH 6.0.
108 The growth of S. aureus on cooked
beef at 45.5
◦ C for 24 hours has been demonstrated, but at 46.6
◦ C, the initial inoculum decreased by 2
log cycles over the same period.
18 The optimum for SEB in a culture medium at pH 7.0 was 39.4
◦ C.
86
Thus, the optimum temperature for enterotoxin production is in the 40–45
◦ C range.
Staphylococcal enterotoxins have been reported to appear in cultures as early as 4–6 hours (Figure
23–2) and to increase proportionately through the stationary phase
67 and into the transitional phase
(Figure 23–3). Enterotoxin production has been shown to occur during all phases of growth,
27 although
earlier studies revealed that with strain S-6, 95% of SEB was released during the latter part of the
log phase of growth. Chloramphenicol inhibited the appearance of enterotoxin, suggesting that the
presence of toxin was dependent on de novo protein synthesis.
95 In ice cream pies, 3.9 ng/g of SEA
was produced in 18 hours at 25
◦ C and 4.8 ng/g in 14 hours at 30
◦ C.
48 In the same study, TNase
was detectable before SEA, with 72 ng/g being found after 12 hours at 37
◦ C. With a 3% pancreatic
digest of casein as substrate and incubation at 37
◦ C, SEC 1 and SEC 2 were produced during the
Table 23–6 D and z Values for the Thermal Destruction of S. aureus 196E in Various Heating
Menstra at 140
◦ F
Products
D(F)
Z
Reference
Chicken `
a la king
5.37
10.5
6
Custard
7.82
10.5
6
Green pea soup
6.7–6.9
8.1
107
Skim milk
3.1–3.4
9.2
107
0.5% NaCl
2.2–2.5
10.3
107
Beef bouillon
2.2–2.6
10.5
107
Skim milk alone
5.34
–
61
Raw skim milk + 10% sugar
4.11
–
61
Raw skim milk + 25% sugar
6.71
–
61
Raw skim milk + 45% sugar
15.08
–
61
Raw skim milk + 6% fat
4.27
–
61
Raw skim milk + 10% fat
4.20
–
61
Tris buffer, pH 7.2
2.0
–
53
Tris buffer, pH 7.2, 5.8% NaCl or 5% MSG
7.0
–
53
Tris buffer, pH 7.2 + 5.8% NaCl + 5% MSG
15.5
–
53
as low as 0.84 and produced SEA.
66 The production of the individual enterotoxins is more inherent to
the toxin than to the strain that produces them.
96 SEA but not SEB has been shown to be produced by
l-phase cells.
26 SEB, C, and D require a functional agr gene for maximal production. In pork, SEA
production occurred at a w of 0.86 but not at 0.83, and in beef at 0.88 but not at 0.86.
106 SEA can be
produced under conditions of a w that do not favor SEB.
110 SED has been produced at an a w of 0.86
in 6 days at 37
◦ C in BHI.
36 In general, SEB production is sensitive to a w , whereas SEC is sensitive
to both a w and temperature. Regarding NaCl and pH, enterotoxin production has been recorded at pH
4.0 in the absence of NaCl (see Table 23–2). The effect of NaCl on SEB synthesis by strain S-6 at pH
7.0 at 37
◦ C is presented in Figure 23–1.
With respect to growth temperature, SEB production in ham at 10
◦ C has been recorded,
40 as well
as small amounts of SEA, SEB, SEC, and SED in cooked ground beef, ham, and bologna at 10
◦ C.
Production has been observed at 46
◦ C, but the optimum temperature for SEB and SEC was 40
◦ C in
a protein hydrolysate medium
112 and for SEE, 40
◦ C at pH 6.0.
108 The growth of S. aureus on cooked
beef at 45.5
◦ C for 24 hours has been demonstrated, but at 46.6
◦ C, the initial inoculum decreased by 2
log cycles over the same period.
18 The optimum for SEB in a culture medium at pH 7.0 was 39.4
◦ C.
86
Thus, the optimum temperature for enterotoxin production is in the 40–45
◦ C range.
Staphylococcal enterotoxins have been reported to appear in cultures as early as 4–6 hours (Figure
23–2) and to increase proportionately through the stationary phase
67 and into the transitional phase
(Figure 23–3). Enterotoxin production has been shown to occur during all phases of growth,
27 although
earlier studies revealed that with strain S-6, 95% of SEB was released during the latter part of the
log phase of growth. Chloramphenicol inhibited the appearance of enterotoxin, suggesting that the
presence of toxin was dependent on de novo protein synthesis.
95 In ice cream pies, 3.9 ng/g of SEA
was produced in 18 hours at 25
◦ C and 4.8 ng/g in 14 hours at 30
◦ C.
48 In the same study, TNase
was detectable before SEA, with 72 ng/g being found after 12 hours at 37
◦ C. With a 3% pancreatic
digest of casein as substrate and incubation at 37
◦ C, SEC 1 and SEC 2 were produced during the