574 Modern Food Microbiology
on the basis of their proteolytic activity. Types A and G are proteolytic, as are some types B and F
strains. Type E is nonproteolytic, as are some B and F strains (see Table 24–3). The proteolytic activity
of type G is slower than that for type A, and its toxin requires trypsin potentiation. All strains that
produce the Type G toxin are placed in the species C. argentinense.
116 It has been recovered from soils
in Argentina, Switzerland, and the United States.
All toxin-producing strains have been placed into one of four groups—I, II, III, or IV. Group I
contains the proteolytics, group II the nonproteolytics, and group IV serological type G. Group III
consists of types C and D. Interestingly, two botulinal toxins have been detected in species other than
C. botulinum. Type F is produced by Clostridium baratii,
45 and a neurotoxin that is antigenically
similar but not identical to type E is elaborated by Clostridium butyricum.
80 In the case of the latter,
the toxin gene was transferred from toxigenic C. butyricum to nontoxigenic C. botulinum type-E-like
recipients by transduction of a defective bacteriophage that is made infective by a helper strain.
129 The
type E toxin gene is chromosomal in both species. It can only be presumed that C. baratii acquired
the toxin by a similar mechanism. The baratii toxin has a molecular weight of ∼140 kDa.
36 Strains of
C. butyricum that produce Type E toxin have been found to do so at a pH of 4.8 over a period of 43
and 44 days.
9 The lowest growth temperature was found to be 12
◦ C, and at this temperature, Type E
toxin was detectable after 15 days while at 25
◦ C, toxin was detectable in 5 days in mascarpone cheese
and pesto sauce.
9
Distribution of C. botulinum
This organism is indigenous to soils and waters. In the United States, type A occurs more frequently
in soils in the western states, and type B is found more frequently in the eastern states and in Europe.
Soils and manure from various countries have been reported to contain 18% type A and 7% type B
spores. Cultivated soil samples examined showed 7% to contain type A and 6% type B endospores.
Type E spores tend to be confined more to waters, especially marine waters. In a study of mud samples
from the harbor of Copenhagen, Pederson
93 found 84% to contain type E spores, whereas 26% of soil
samples taken from a city park contained the organism. From a study of 684 environmental samples
from Denmark, the Faroe Islands, Iceland, Greenland, and Bangladesh, 90% of aquatic samples from
Denmark and 86% of marine samples from Greenland contained type E.
52 This strain was not found
in Danish soils and woodlands, whereas type B was. Based on these results, Huss
52 suggested that
type E is a truly aquatic organism that proliferates in dead aquatic animals and sediments and is
disseminated by water currents and migrating fish. Type E spores have been known for some time to
exist in waters off the shores of northern Japan. Prior to 1960, the existence of the organisms in the
Great Lakes and the Gulf Coast waters was not known, but their presence in these waters as well as
in the Gulf of Maine and the gulfs of Venezuela and Darien is well established. Ten percent of soil
samples tested in Russia were found positive for C. botulinum, with type E strains being predominant.
In a study of 333 samples from a Finnish trout farm, type E was found in 95% of those from 21 farms,
in 68% of sediment samples, 15% of fish intestinal samples, and 5% of fish skin samples.
48 No types
A, B, or F were found. According to these investigators, the Baltic Sea has the highest level of Type
E contamination in the world.
As to the overall incidence of C. botulinum in soils, it has been suggested that the numbers per gram
are probably less than 1. The nonproteolytic types are associated more with waters than soils, and it
may be noted from Table 24–3 that the discovery of these types occurred between 1960 and 1969. The
late recognition is probably a consequence of the low heat resistance of the nonproteolytics, which
would be destroyed if specimens were given their usual heat treatment for spore recovery.
on the basis of their proteolytic activity. Types A and G are proteolytic, as are some types B and F
strains. Type E is nonproteolytic, as are some B and F strains (see Table 24–3). The proteolytic activity
of type G is slower than that for type A, and its toxin requires trypsin potentiation. All strains that
produce the Type G toxin are placed in the species C. argentinense.
116 It has been recovered from soils
in Argentina, Switzerland, and the United States.
All toxin-producing strains have been placed into one of four groups—I, II, III, or IV. Group I
contains the proteolytics, group II the nonproteolytics, and group IV serological type G. Group III
consists of types C and D. Interestingly, two botulinal toxins have been detected in species other than
C. botulinum. Type F is produced by Clostridium baratii,
45 and a neurotoxin that is antigenically
similar but not identical to type E is elaborated by Clostridium butyricum.
80 In the case of the latter,
the toxin gene was transferred from toxigenic C. butyricum to nontoxigenic C. botulinum type-E-like
recipients by transduction of a defective bacteriophage that is made infective by a helper strain.
129 The
type E toxin gene is chromosomal in both species. It can only be presumed that C. baratii acquired
the toxin by a similar mechanism. The baratii toxin has a molecular weight of ∼140 kDa.
36 Strains of
C. butyricum that produce Type E toxin have been found to do so at a pH of 4.8 over a period of 43
and 44 days.
9 The lowest growth temperature was found to be 12
◦ C, and at this temperature, Type E
toxin was detectable after 15 days while at 25
◦ C, toxin was detectable in 5 days in mascarpone cheese
and pesto sauce.
9
Distribution of C. botulinum
This organism is indigenous to soils and waters. In the United States, type A occurs more frequently
in soils in the western states, and type B is found more frequently in the eastern states and in Europe.
Soils and manure from various countries have been reported to contain 18% type A and 7% type B
spores. Cultivated soil samples examined showed 7% to contain type A and 6% type B endospores.
Type E spores tend to be confined more to waters, especially marine waters. In a study of mud samples
from the harbor of Copenhagen, Pederson
93 found 84% to contain type E spores, whereas 26% of soil
samples taken from a city park contained the organism. From a study of 684 environmental samples
from Denmark, the Faroe Islands, Iceland, Greenland, and Bangladesh, 90% of aquatic samples from
Denmark and 86% of marine samples from Greenland contained type E.
52 This strain was not found
in Danish soils and woodlands, whereas type B was. Based on these results, Huss
52 suggested that
type E is a truly aquatic organism that proliferates in dead aquatic animals and sediments and is
disseminated by water currents and migrating fish. Type E spores have been known for some time to
exist in waters off the shores of northern Japan. Prior to 1960, the existence of the organisms in the
Great Lakes and the Gulf Coast waters was not known, but their presence in these waters as well as
in the Gulf of Maine and the gulfs of Venezuela and Darien is well established. Ten percent of soil
samples tested in Russia were found positive for C. botulinum, with type E strains being predominant.
In a study of 333 samples from a Finnish trout farm, type E was found in 95% of those from 21 farms,
in 68% of sediment samples, 15% of fish intestinal samples, and 5% of fish skin samples.
48 No types
A, B, or F were found. According to these investigators, the Baltic Sea has the highest level of Type
E contamination in the world.
As to the overall incidence of C. botulinum in soils, it has been suggested that the numbers per gram
are probably less than 1. The nonproteolytic types are associated more with waters than soils, and it
may be noted from Table 24–3 that the discovery of these types occurred between 1960 and 1969. The
late recognition is probably a consequence of the low heat resistance of the nonproteolytics, which
would be destroyed if specimens were given their usual heat treatment for spore recovery.