Thirty four different serotypes of Salmonella have been isolated from aquatic products. The number of serotypes from frozen froglegs were 22. Only four serotypes were isolated from frozen shrimps. S. weltevreden predominates in frozen shrimps and fish. S. roan and S. larochelle were isolated for the first time in India. Isolation of six rare serotypes of Salmonella has also been reported

Gopalakrishna Iyer, T.S.

Shrivastava, K.P.

Aquatic Commons

O e Pattern of Salmonella Serotypes in Fishery Products, 
Froglegs an Processing Envi ents* 
T. S. GOPALAKRISHNA IYER 
Central Institute of Fisheries Technology, Cochin-682 029 
and 
K. P. SHRIVASTAVA 
Export Inspection Agency-Delhi, New Delhi-110 006 
Thirty four different serotypes of Salmonella have been isolated from aquatic pro-
ducts. The number of serotypes from frozen froglegs were 22. Only four serotypes 
were isolated from frozen shrimps. S. weltevreden predominates in frozen shrimps 
and fish. S. roan and S. larochelle were isolated for the first time in India. Isolation 
of six rare serotypes of Salmonella has also been reported. 
Over 2000 Salmonella serotypes are known 
to-day and every year new serotypes are being 
added to the list. However, comparatively 
fewer number of serotypes only are encoun-
tered in any particular country. The National 
Salmonella and Escherichia Centre, Kasauli 
has reported the occurrence of 161 serotypes 
of Salmonella in India (Saxena, 1987 per-
sonal communication). The strains figured 
in this report were mostly isolated from 
human being, animals, water and sewage. 
Sharma et al. (1974), Rao & Nandy (1976), 
Andrews et al. (1977) and Rajagopalan (1978) 
have carried out brief studies on Salmonella 
serotypes in froglegs. But, no detailed 
study has so far been carried out anywhere 
on the pattern of occurrence of Salmonella 
serotypes in fishery products even though 
serological classification has been generally 
found to be useful in identifying the sources 
of contamination of processed products 
with Sabnonella. Detailed studies were, 
therefore, carried out on the incidence of 
Salmonella pattern in fresh and frozen fishery 
products, froglegs and processing environ-
ments. The results of the study are presen-
ted in this paper. 
Materials an.d Methods 
Samples of the different fishery products 
(except fresh fish samples and dried jawala 
* Formed part of the Ph.D. thesis of the first author 
approved by the University of Kerala. 
Vol. 26, 1989 
prawns) were collected from the processing 
factories situated at Cochin. The fresh fish 
samples and the dried jawala prawns were 
from the retail fish markets in Bombay. In 
addition, a few swab samples from fish 
contact surfaces, water and ice were also 
collected from the factories at Cochin. 
Details showing the number of samples from 
different sources are as follows: 
Source No. of 
samples 
Frozen shrimps (Headless sheH-on) 130 
Frozen shrimps (peeled & deveined) 150 
Frozen shrimps (peeled undeveined) 100 
Frozen shrimps (Cooked and peeled) l 00 
Frozen lobsters (Headless sheU-on) 13 
Frozen cuttle fish 50 
Frozen squids 30 
Frozen red snapper l 
Frozen cat fish 8 
Frozen seer fish 40 
Frozen froglegs 120 
Driedjawala prawns 150 
Utensils 25 
Floor 150 
Worker's palm 50 
Water 50 
~ 1W 
Raw shrimps 120 
Raw fish 10 
Raw lobsters . 2 
Raw froglegs 10 
132 
Fish meal 
Poultry feed containing fish meal 
Sea-beach sand 
80 
1 
20 
Fishery products and the sea beach sam-
ples were collected in sterile containers. 
The swabs from contact surfaces were separa-
tely collected in 100 ml of lactose broth. 
Water and ice were collected in sterile bottles. 
The samples were transported to the labora-
tory under aseptic conditions. During 
transportation, the samples were kept cooled 
using crushed ice kept out of contact with 
the samples. In the laboratory, the sam-
ples were analysed for the presence of Sal-
monella as per the method recommended 
by AOAC (1975). The number of Sal-
nwnella strains isolated from different sour-
ces were as follows: 
Frozen froglegs 165 
Frozen shrimps 38 
Frozen fish 30 
Frozen lobsters 12 
Raw froglegs 14 
Raw shrimps 7 
Raw fish 50 
Raw lobsters 9 
Fish meal 1 
Poultry feed containing :fish meal 7 
Driedjawala prawn 7 
Utensils 3 
Floor of processing hall 5 
Vlater 1 
Sea beach sand 9 
Total 358 
The isolated strains were serotyped at the 
National Salmonella and Escherichia Centre 
at Kasauli (India) following the methods of 
Edwards & Ewing (1972) and Cowan (1972). 
Results and Discussion 
The salmonella serotypes isolated from 
different fishery products and related sources 
are given in Table l. Thirty four different 
serotypes were isolated from these sources. 
The number of serotypes isolated from fro-
zen froglegs were higher (22) compared to 
the number of isolates from other sources. 
Only four serotypes ( S. weltevreden, S. 
bareilly, S. orion and S. virchow) were iso-
lated from frozen shrimps. Eleven different 
T. S. G. IYER AND K. P. SHRIVASTAVA 
serotypes were isolated from fresh fishes 
while six serotypes were isolated from frozen 
:fish. The serotypes isolated from miscel-
laneous sources were 8; these included iso-
lates from utensils, floor, water, sea-beach 
sand, raw froglegs, dried prawns, fish meal 
and poultry feed containing fish meal. 
Normally, the incidence of Salmonella 
in marine fish and shellfish is the result of 
contamination from the unhygienic surround-
ings in which they are handled and processed. 
In the case of froglegs, on the other hand, 
it is due to contamination from its own 
intestine which is known to inhabit Salmo-
nella (Iyer et al., 1975). Recent studies 
have indicated the presence of a wide variety 
of Salmonella serotypes in the intestine of 
frogs (Sharma & Garg, 1976; Rajagopalan, 
1978). Frogs are collected from paddy 
fields, canals, roadsides and similar habitats 
which are likely to get contaminated with 
sewage and faecal matter. Therefore, it is 
likely that the serotypes usually isolated 
from man and animals are isolated from frogs 
also. Saxena et al. (1983) have reported that, 
in India, S. typhimurium, S. bareilly and S. 
saintpaul are the most common serotypes 
isolated from human stool and that S. saint-
paul and S. typhimurium are the domina-
ting serotypes in animals and sewage respecti-
vely. Thus, the isolation of S. typhimurium, 
S. saintpaul and S. bareilly from frogs' intes-
tine (Sharma & Garg, 1976; Rajagopalan, 
1978) and from frozen froglegs in the pre-
sent study are quite expected. S. arizonae 
was one of the major serotypes isolated from 
frozen froglegs (Table 1). S. arizonae has 
also been isolated by Sharma et al. (1974), 
Rw & Nandy (1976), Andrews et al. (1977) 
and Rajagopalan (1978) from frozen fro-
glegs. S. arizonae is of reptile origin (Rowe, 
1973) and as frogs live in almost the same 
natural habitats as that of reptiles, the iso-
lation of this serotype from frozen froglegs 
is not unexpected. Plows et al. (1968) repor-
ted S. arizonae as the causative agent of 
gastroenteritis in Britain. 
S. weltevreden was the dominating sero-
type in frozen shrimps, fresh fish, frozen fish, 
fresh lobsters and frozen lobsters (Table 1 ). 
In the case of fish and shrimps contamina-
tion with salmonellae appears to be mostly 
FISHERY TECHNOLOGY 
ON THE PATTERN OF SALMONELLA SEROTYPES 133 
due to unhygienic handling practices. S. 
weltevreden was isolated from the fl.oor of 
the processing hall and from the utensils 
used in the processing factories (Table 1). 
Thus, it is likely that the fl.oor and the uten-
sils might have caused contamination of fish 
and shrimps with S. weltevreden. As rodents 
and wall lizards were seen in some of the 
processing units, it could be assumed that 
the utensils used in the processing units 
might have got contaminated from the drop-
pings of rodents and wall lizards. In India, S. 
weltevreden has often been isolated from the 
intestinal contents of wall lizards (Kaura & 
Singh, 1968; Gupta et al., 1980) and rodents 
(Kaura & Singh, 1968). Moreover, S. welte-
vreden has frequently been isolated from 
natural water sources (Basu et al., 1975) 
also. It is, therefore, evident that S. welte-
vreden is usually present in the environment 
where fish, shrimps and lobsters are handled. 
Basu et al. (1975) have reported that, in India, 
infections due to S. weltevreden have increas-
ed both in man and animals after 1970. 
The isolation of S. larochelle (6, 7 eh: 1,2) 
and S. roan 38, lv : enx (Table 1) have 
not been reported previously from any source 
in India. Later, 8 more isolations of S. 
larochelle were made in India and all these 
were from human sources: five from stool 
and three from urine (Saxena et al., 1983). 
The role of S. larochelle in human salmonello-
sis is thus evident. The isolation of S. cubana, 
S. waycross, S. stanley, S. paratyphi B and 
S. heidelberg is reported for first time in 
frozen froglegs. S. heidelberg has rarely 
been isolated in India and only two isolations 
have been made previously - both from 
human sources (Saxena et al., 1983). In 
India, till 1962, S. cubana had been isolated 
from-human ·-sources orily. Later, a few 
isolations of this serotype were made from 
animals also, but still isolations from human 
sources predominate (Saxena et al., 1984). 
S. waycross, isolated from frozen froglegs, 
is also a rare serotype and only one strain 
has, so far, been isolated in this country 
(Saxena et al., 1980). This serotype has 
not been isolated from human sources. 
Saxena et al. (1983) have reported the iso-
lation of this serotype from the intestines of 
frogs and therefore, contamination of fro-
glegs from this source is quite possible. In 
India, S. saintpaul and S. bareilly have been 
isolated from many sources like human, 
Vol. 26, 1989 
cattle, pig, poultry, frog's intestine, laboratory 
animals, water and sewage (Saxena et al., 
1983). The wide distribution of these sero-
types explains their presence in many of the 
products tested in the present study. Amongst 
the various serotypes isolated in India, S. 
bareilly and S. saintpaul occupy the 3rd and 
4th position in the order of predominance 
(Saxena et al., 1984). S. bareilly has been 
isolated from the fl.oor of the processing haH 
(Table l). Ghosh et al. (1960) have reported 
an outbreak of food poisoning in Calcutta 
(India) due to S. newport. S. newport, S. 
chingola, S. anatum and S. bredeney have 
been isolated from frozen froglegs only 
(Table 1 ). In India, all these serotypes have 
been isolated from natural waters and sewage 
(Saxena et al., 1983). Two strains of S. 
poona have been isolated in the present study, 
one each from frozen fish and raw shrimps. 
In India, S. poona has been isolated from 
human sources only (Saxena et al., 1988). Co-
ntamination of seafoods with S. poona from 
human sources is, therefore, suspected. S. 
· typhimurium was isolated from one sample 
of water used for shrimp processing. In 
India, though S. typhimurium has frequently 
been isolated from natural water~ and sewage 
(Saxena et al., 1983), there is no previous 
record of isolation of this serotype from the 
water used by the seafood industry. As 
bird's droppings were seen inside the over-
head watertank, contamination from this 
water source is quite likely. 
In the present study, S. alachua, S. muen-
chen and S. eastbourne were isolated from 
raw fish. As per the report of the Centres 
for Disease Control (1981) of the U.S., S. 
alachua is to be classified as an uncommon 
and rare serotype. In India, this serotype 
was first isolated at Bombay by Das and 
Jayaraman (1955) from fowls. Dewan et 
al. (1976) have reported the isolation of S. 
alachua from sewage and water sources in 
India. Till recently, this serotype was 
thought to be mainly confined to animal 
sources. But, Chaudhuri et al., (1978) 
reported the isolation of S. alachua from 
human sources and pointed out its associa-
tion with clinical morbidity and mortality. 
According to the latest compilation on the 
pattern of the occurrence of Salmonella in 
India, S. muenchen has not been isolated 
from human sources in this country whereas 
134 T. S. G. IYER AND K. P. SHRIVASTAVA 
Table Salmonella serotypes isolated from different fishery products and related sources 
Number of strains isolated 
Sero type Frozen Raw Frozen Raw Frozen Raw Frozen Other 
froglegs fish fish shrimps shrimps lobsters lobsters sources 
S. tyhimurium 26 (15.7) 3 (10) 1 (14.2) 1 (11) 1 (8.3) 2a(4.2) 
S.arizonae 20(12.l) 2(2.6) 
S. roan* 18(11.0) 6b (12.7) 
S. saintpaul 12 (7.2) 1 (14.2) 2c (4.2) 
S. bareilly 11 (6.6) 2 (4) 3 (10) 2 (5.2) 16d (34.5) 
S.newport 11 (6.6) 
S.anatum 10 (6.1) 
S.bredeney 6 (3.6) 
S. matopeni** 6 (3.6) 
S. chester 5 (3.1) 
S.nchanga** 5 (3.1) l (8.3) 
S. chingola** 5 (3.1) 
S. hvittingfoss 5 (3.1) 
S. heidelberg** 5 (3.1) l (14.2) 
S. waycross** 4 (2.4) 
S. stanley 3 (1.8) 3 (6) 
S.richmond 3 (1.8) le (2.1) 
S.salford 3 (1.8) 
S. virchow 2 (1.2) 6 (12) 2(29) 1 (2.6) 
S. larochelle* 2 (1.2) 3 (6) 
Rough strain 2 (1.2) 
S. cubana 1 (0.6) 
S. senftenberg 3 (25) 
S. orion** 1 (3.4) 1 (2.6) 
S. weltevreden 16 (32) 20 (66.6) l (14.2) 34 (89.6) 6 (89) 7 (58.4) 6f (12.7) 
S.poona 1 (3.4) l (14.2) 
S. paratyphi B 7g (14.8) 
S. ohio 2 (4) 
S.muenchen 4 (8) 
S. alachva 4 (8) 
S. eastbourne** 2 (4) 
S. oranienberg 7 (14) 
S. subgenus III l (2) 
S. enteritidis 7h (14.8) 
* Isolated for the first time in India; ** Rarely isolated serotype in India. 
Figures in parenthesis indicate the percentage occurrence of the corresponding serotype amongst 
the total number of Salmonella strains isolated from the respective source. 
2a - one strain from water and one 
strain from floor 
6b - all the strains are from raw frnglegs 
2c - both the strains are from raw froglegs 
16d - six strains from poultry feed, three 
strains from fl.oor and seven strains 
from sea-beach sand 
le - from raw froglegs 
6f- one strain from floor, three strains 
from nutensils, and two strains from 
sea-beach sand 
7g_ five strains from raw FL, one strains 
from fish meal and one strain from 
poultry feed 
7h_ an strains are from driedjawala prawns 
FISHERY TECHNOLOGY 
ON THE PATTERN OF SALMONELLA SEROTYPES 135 
31 strains have been isolated from animals 
(Saxena et al., 1980). In the U.S., on the 
other hand, S. muenchen, in 1978, occupied 
14th position in the list of the 20 most fre-
quently reported Salmonella serotypes from 
human sources (Centres for Disease Control, 
1981). Morris et al. (1970) reported S. 
muenchen as one of the serotypes commonly 
isolated from fish meal during 1962-64. In 
Iraq, Nassir Al Hindawi et al. (1979) have 
reported the presence of S. muenchen in 2 
out of the 30 fish powder samples analysed 
by them. In the U.S., S. muenchen is sel-
dom reported to be present in estuary waters 
and shell fish (Metcalf et al., 1973). In 
Australia, S. muenchen was one amongst 
the more frequently isolated strains from the 
cases of human salmonellosis during 1967-71 
(Suttoon, 1973). An epidemic among infants 
caused by S. muenchen has been reported 
by Silverstolpe et al. (1961). Thus the 
pathogenic role of S. muenchen is quite 
evident. 
S. eastbourne is a rarely isolated serotype 
in India, as only 5 strains of this serotype 
have so far been isolated in the country 
within a period of 24 years (Iyer, 1985). 
4 strains have been isolated from sewage 
in Nagpur and one was isolated from frozen 
shrimps in Madras. There is no previous 
record of isolation of this serotype from 
fin fish. In the U.S. also, this serotype has 
been classified as an uncommon and rare 
serotype (Centres for Disease Control, 1981). 
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FISHERY TECHNOLOGY 


On the pattern of Salmonella serotypes in fishery products, froglegs and processing environments

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On the pattern of Salmonella serotypes in fishery products, froglegs and processing environments

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