114 Modern Food Microbiology
In 1998–1999, 370 lots of oysters from coastal waters and 29 states in the United States were
examined at 275 establishments. Gulf Coast oysters contained the highest number of Vibrio vulnificus
and V. parahaemolyticus with numbers exceeding 10
5 MPN/g while V. vulnificus was <0.2 MPN/g
and none exceeded 100 MPN/g in oysters from the north Atlantic, Pacific, and Canadian coasts.
21
Thermostable direct hemolysin was detected in 9 of 3,429 (0.3%) V. parahaemolyticus cultures and in
4% of oyster lots. Among 345 samples of retail oysters from ca. 20 states and two Canadian provinces,
the highest number of V. vulnificus was 25 × 10
5 in oysters in Florida. The highest number of V.
vulnificus was found in oysters from the state of Mississippi, >8.8 × 10
5 MPN/g.
21 In an earlier study
of oysters from 39 sites in the state of Washington in 1997, 9 contained <3/g.
23 In the same study, 34
oysters from Galveston Bay, Texas contained a mean of log 10 2.36–2.73 cfu/g. The level of alarm for
V. parahaemolyticus in oysters in the United States is an MPN of 10
4 /g.
27 In a study of 671 samples
of molluscan shellfish harvested in 1999 and 2000 from 14 sites in waters off the American Gulf and
Atlantic coast states, 6.0% were positive for V. parahaemolyticus by gene probe and culture methods.
20
The numbers of positives correlated with water temperature, with numbers being higher in the warmer
waters. This organism was found in north Atlantic waters only during the summer but they were found
during all seasons in Gulf waters. Although they are generally associated with pork, 21 Erysipelothrix
spp. were isolated from seafoods in Australia.
30
In regard to noroviruses in oysters, 87 samples (of 435 oysters) tested in Switzerland that were
imported from three European countries between November 2001 and February 2002 showed that
11.5% were positive (all of which belonged to serogroup II—see Chapter 31) and 2.3% contained
enteroviruses (coxsackie and ECHO). No hepatitis A viruses were found.
7 In a study of 147 roes
from three fish species in Finland, Listeria spp. were found in 17% and L. monocytogenes in 4.7%,
with trout containing the highest percentage of the latter.
68 The mean APC was log 10 6.6 cfu/g, and
coliforms were log 10 3.2 cfu/g, placing these products in the “moderate” class based on APC, but in
the “unacceptable” class based on coliform numbers.
Employing a PCR-ELISA detection technique, a survey of C. botulinum spores was conducted
in northern France and this organism was found in 31 of 214 environmental samples. Most positive
samples contained <10 spores/25 g fish, and 16.6% of seawater fish and 4% of sediment samples were
positive with 70% being type B; 22.5% type A; and 9.6% type E.
28 No type F spores were found.
A study of 106 Gram-negative nonmotile rods isolated from ice-stored freshwater fish in Spain
found that 64 were Psychrobacter spp. followed by 24 Acinetobacter, 6 Moraxella, 5 Chryseobacterium, 2 Myroides, 1 each of Flavobacterium and Empedobacter; and 3 unknown.
39 Chryseobacteria,
empedobacteria, and myroides were previously classified in the genus Flavobacterium.
In a study of Listeria spp. in raw and processed crawfish in the United States in 2001, they were
found in 31 of 337 (9.2%), but only 4 were positive for L. monocytogenes.
91 When a total of 2,446
ready-to-eat seafood salads from two states in the United States were examined for L. monocytogenes
in 2000 and 2001, 4.7% were positive.
38 In the same survey, L. monocytogenes was found in 4.3% of
2,644 ready-to-eat smoked seafoods.
For the 9-year period 1990–1999, the FDA in the United States examined imported and domestic
fish and seafoods for salmonellae. Of the 11,312 imported samples, 7.2% were positive while only
1.3% of the 768 domestic samples were positive.
44 The most common serovar found in this survey
was S. Weltvreden.
From a study of 50 frozen fish samples in Spain for the prevalence of nontuberculous mycobacteria,
20% were found to contain these bacteria with M. fortuitum and M. nonchromogenicum being the
two most common species.
67 Of the approximate one-half of isolates that could be identified, they
consisted of six species. Little, if anything, is known about the significance of these organisms in
seafoods. It may be assumed that they play no role in seafood spoilage because of their slow growth.
In 1998–1999, 370 lots of oysters from coastal waters and 29 states in the United States were
examined at 275 establishments. Gulf Coast oysters contained the highest number of Vibrio vulnificus
and V. parahaemolyticus with numbers exceeding 10
5 MPN/g while V. vulnificus was <0.2 MPN/g
and none exceeded 100 MPN/g in oysters from the north Atlantic, Pacific, and Canadian coasts.
21
Thermostable direct hemolysin was detected in 9 of 3,429 (0.3%) V. parahaemolyticus cultures and in
4% of oyster lots. Among 345 samples of retail oysters from ca. 20 states and two Canadian provinces,
the highest number of V. vulnificus was 25 × 10
5 in oysters in Florida. The highest number of V.
vulnificus was found in oysters from the state of Mississippi, >8.8 × 10
5 MPN/g.
21 In an earlier study
of oysters from 39 sites in the state of Washington in 1997, 9 contained <3/g.
23 In the same study, 34
oysters from Galveston Bay, Texas contained a mean of log 10 2.36–2.73 cfu/g. The level of alarm for
V. parahaemolyticus in oysters in the United States is an MPN of 10
4 /g.
27 In a study of 671 samples
of molluscan shellfish harvested in 1999 and 2000 from 14 sites in waters off the American Gulf and
Atlantic coast states, 6.0% were positive for V. parahaemolyticus by gene probe and culture methods.
20
The numbers of positives correlated with water temperature, with numbers being higher in the warmer
waters. This organism was found in north Atlantic waters only during the summer but they were found
during all seasons in Gulf waters. Although they are generally associated with pork, 21 Erysipelothrix
spp. were isolated from seafoods in Australia.
30
In regard to noroviruses in oysters, 87 samples (of 435 oysters) tested in Switzerland that were
imported from three European countries between November 2001 and February 2002 showed that
11.5% were positive (all of which belonged to serogroup II—see Chapter 31) and 2.3% contained
enteroviruses (coxsackie and ECHO). No hepatitis A viruses were found.
7 In a study of 147 roes
from three fish species in Finland, Listeria spp. were found in 17% and L. monocytogenes in 4.7%,
with trout containing the highest percentage of the latter.
68 The mean APC was log 10 6.6 cfu/g, and
coliforms were log 10 3.2 cfu/g, placing these products in the “moderate” class based on APC, but in
the “unacceptable” class based on coliform numbers.
Employing a PCR-ELISA detection technique, a survey of C. botulinum spores was conducted
in northern France and this organism was found in 31 of 214 environmental samples. Most positive
samples contained <10 spores/25 g fish, and 16.6% of seawater fish and 4% of sediment samples were
positive with 70% being type B; 22.5% type A; and 9.6% type E.
28 No type F spores were found.
A study of 106 Gram-negative nonmotile rods isolated from ice-stored freshwater fish in Spain
found that 64 were Psychrobacter spp. followed by 24 Acinetobacter, 6 Moraxella, 5 Chryseobacterium, 2 Myroides, 1 each of Flavobacterium and Empedobacter; and 3 unknown.
39 Chryseobacteria,
empedobacteria, and myroides were previously classified in the genus Flavobacterium.
In a study of Listeria spp. in raw and processed crawfish in the United States in 2001, they were
found in 31 of 337 (9.2%), but only 4 were positive for L. monocytogenes.
91 When a total of 2,446
ready-to-eat seafood salads from two states in the United States were examined for L. monocytogenes
in 2000 and 2001, 4.7% were positive.
38 In the same survey, L. monocytogenes was found in 4.3% of
2,644 ready-to-eat smoked seafoods.
For the 9-year period 1990–1999, the FDA in the United States examined imported and domestic
fish and seafoods for salmonellae. Of the 11,312 imported samples, 7.2% were positive while only
1.3% of the 768 domestic samples were positive.
44 The most common serovar found in this survey
was S. Weltvreden.
From a study of 50 frozen fish samples in Spain for the prevalence of nontuberculous mycobacteria,
20% were found to contain these bacteria with M. fortuitum and M. nonchromogenicum being the
two most common species.
67 Of the approximate one-half of isolates that could be identified, they
consisted of six species. Little, if anything, is known about the significance of these organisms in
seafoods. It may be assumed that they play no role in seafood spoilage because of their slow growth.