ROLE OF FISH IN TRANSMITTING SOME ZOONOTIC BACTERIA
CAUSING FOOD POISONING TO MAN
By
LOBNA, M.A. SALEM AND El-NEWISHY, A.A.
Department of Zoonoses, Faculty of Veterinary Medicine, Benha University
.
ABSTRACT
A total of seventy fish samples of Tilapia nilotica and cat fish (Clarias garipinus) (35 of each)
were collected from different fish markets at Qalyobia Governorate. In addition to hand swabs
of twenty fish handlers were examined bacteriologically to determine the role played by fish
in transmitting some zoonotic bacteria causing food poisoning. Clarias fish samples had
a significantly higher bacterial isolates (62.9%) than tilapia fish samples (45.7%). Among the
isolated bacteria, Staph-aureus was detectable at higher percentage (25.7%) followed by
E.coli (18.9%), then Salmonella spp. (7.1%) and the lowest isolates were Shigella spp.
(2.9%). The highest percentage of bacterial isolates was recovered from skin surface followed
by intestine, whereas muscles showed the lowest percentage in both types of examined fish.
Hand swabs of fish handlers demonstrated 20% and 10% positive results for Staph-aureus and
E.coli respectively. The current research indicated that fish may represent a serious threat
to public health as a result of transmission of some food poisoning pathogens. The public
health importance of the isolates and suggestive hygienic measures were discussed.
INTRODUCTION
Fish are one of the cheapest source of protein and considered as a good replacer of meat and
poultry in the human diet for its high nutritive value, palatability and good digestibility.
On the other hand, fish have a significant role in possible transfer of pathogens between
livestock and human, although some of them do not produce disease in fish (Edun et al.,
2007). Fish act as carrier of some zoonotic bacteria either on the skin and gills or in the
intestine. These include E.coli, Salmonella, Shigella, Proteus, staphylococcus and others
which are incriminated in food poisoning, skin disorders, allergic conditions as well as other
infections (Janssen, 1970). Fish can acquire pathogenic microorganisms from natural aquatic
environment contaminated with sewage or from dirty hands of fish handlers, or contaminated
utensils and equipments during harvesting, processing and preservation (National Academy
of Science, 1985).
Nowadays, water pollution with domestic waste water is most common in River Nile and its
tributaries, the greatest volume of wastes discharged in the water course is sewage, such
pollution reduces the water quality and had been reported as a precursor to fish infection with
some microorganisms that can infect both consumers and handlers (Omer et al., 2004).
Human infections caused by organisms transmitted from fish or the aquatic environment
depending on the season, the patient's contact with fish and related environment, dietary
habits and the immune system status of the exposed individual (Onyango et al., 2009).
Human infections by fish pathogens are usually through contact with abraded skin with
infected fish while handling or with water or other constituents of an aquatic environment
(Acha and Szyfres, 2003). Moreover, people use some ways for preparation of fish to be
eaten each as rapid frying, smoking and pickling and such methods have been proved to be
insufficient to kill all harmful microorganisms which may be present in raw fish prior to
preparation (Khalil et al., 1990 and Mansour et al., 1997). The consumption of
contaminated fish gives rise to intestinal disorders ranging from diarrhea and vomiting to
fever (Naglaa et al., 2002).
In Egypt, Salmonellae, E.coli and Staph. aureus are widely recognized as the principle causes
of food poisoning outbreaks occurring as a result of consumption of contaminated fish and
fish products (Eley, 1996 and Hassan & Fatin, 2003), so the present study was carried out to
detect the role of fish in transmitting some zoonotic bacteria causing food poisoning to
humans after handling or consumption of such fish in Qalyobia Governorate.
MATERIALS AND METHODS
1- Sampling:
1- a- Fish samples:
A total of seventy random fish samples of Tilapia nilotica and cat fish (Clarias garipinus) (35
of each) were collected from different fish markets at Qalyobia Governorate. The collected
fish samples were packed separately in sterile plastic bags and transported to the laboratory in
an ice box without delay to be examined.
1-b- Human samples:
Hand swabs were taken from twenty fish handlers working at the same markets from which
fish samples were collected.
2- Preparation of samples:
2-a- Fish samples:
Surface swabs, pieces of muscles and intestinal contents were aseptically taken from each fish
and were separately inoculated into separate sterile tubes containing nutrient broth, lauryl
sulphate tryptose broth and selinite cystine broth as enrichment broth media, then incubated at
37°C for 18-24hrs.
2-b- Human samples:
From each fish handler, hand swabs were taken by rubbing swabs in the inter-digital spaces,
nails, palms and on the back of the hands and were separately inoculated into separate sterile
tubes containing the previously mentioned broth.
3- Bacteriological examination of samples:
3-a- Detection of staphylococcus:
For isolation of staphylococcus, plates of Baird Parker medium were streaked from previously
inoculated nutrient broth with fish or human samples and incubated at 37°C for 24-48hrs.
Suspected colonies were picked up and purified for further identification according to
(Macfaddin, 1980 and Holt et al., 1994).
3-b- Detection of salmonellae and shigella:
It was done using the method recommended by A.P.H.A (1992) as: loopfuls from selenite
cystine broth cultures were streaked onto MacConkey and salmonella shigella agar plates and
incubated at 37°C for 24hrs. Suspected colonies were picked up and purified for further
identification according to (Kaufmann, 1996; Andrews & Hammack, 1998 and Popoof &
LeMinor, 2003).
3-C- Detection of E.coli: (according to A.P.H.A, 1992)
Loopfuls from each positive lauryl sulphate tryptose broth cultures were separately
transferred into E.coli broth tubes and incubated at 45°C for 48hrs. From each positive E.coli
broth tubes, loopfuls were streaked onto Levine Eosin methylene blue (EMB) agar plates and
incubated at 37°C for 24hrs. The typical colonies were picked up and purified for further
identification according to (Macfaddin, 1980 and Holt et al., 1994).
RESULTS
Table (1): Number and percentage of isolated microorganisms from examined fish.
Examined fish
Tilapia nilotica (35)
Isolates
Clarias garipinus (35)
Total (70)
No
%
No
%
No
%
Salmonella spp.
2
5.7
3
8.6
5
7.1
Shigella spp.
1
2.9
1
2.9
2
2.9
E.coli
5
14.3
8
22.9
13
18.9
Staphylococcus
8
22.9
10
28.6
18
25.7
Total
16
45.7
22
62.9
38
54.3
Table (2): Types of isolated microorganisms from examined fish.
Number
Tilapia nilotica
Clarias garipinus
Salmonella typhimurium
1
2
Salmonella enteritidis
1
1
Shigella dysentery
1
1
O55 : K59 (B5)
2
3
O111 : K58 (B9)
1
2
O86 : K61 (B7)
1
2
O128 : K67 (B12)
1
1
Staph. aureus
8
10
Types of isolates
E.coli
Table (3): Frequency distribution of isolated microorganisms in different parts of examined fish.
Tilapia nilotica
Examined fish
Clarias garipinus
parts
Total
isolates
surface
muscle
intestine
Total
isolates
surface
muscle
intestine
Isolates
No
No
%
No
%
No
%
No
No
%
No
%
No
%
Salmonella spp.
2
2
100
0
0
0
0
3
2
66.7
0
0
1
33.3
Shigella spp.
1
1
100
0
0
0
0
1
1
100
0
0
0
0
E.coli
5
1
20
0
0
4
80
8
1
12.5
2
25
5
62.5
Staph. aureus
8
5
62.5
3
37.5
0
0
10
8
80
2
20
0
0
Total
16
9
56.3
3
18.8
4
25
22
12
54.5
4
18.2
6
27.3
Table (4): Results of bacteriological examination of hand swabs of fish handlers
Staph. aureus
Isolates
E.coli
Fish
No
%
No
%
4
20
2
10
handlers
20
The two strains were
O55 : K59 (B5)
O128 : K67 (B12)
DISCUSSION
It is evident from (Table 1) that total percentages of the isolated bacteria were 45.7 and 62.9
in tilapia fish and claries fish respectively. The higher bacterial isolation detected in claries
fish than in tilapia fish may be due to feeding habits of claries fish as they are carnivorous fish
and tend to eat more animal material than plant food (Abdel-Malak,1972 and Radwan,
1992). The presence of bacterial organisms in fish was attributed to contamination of such
fish with polluted water, contact with dirty boats, cooking in fishing containers straight on the
deck or direct contact with human carriers (Novotny et al., 2004). Moreover, the total
percentages of isolation of different microorganisms from the examined fish were 7.1, 2.9,
18.9 and 25.7 for Salmonella spp., Shigella spp., E.coli and staphylococcus respectively.
These organisms were frequently reported to be isolated by (Mekheal, 2003; Yagoub and
Ahmed 2004 and Herrer et al., 2006). It is worth mentioning that isolation of these bacterial
species is an indication of fecal and environmental pollution. In most instances,
contamination results from the poor quality of water sources and sewage pollution.
Furthermore, fish may get infected through improper and unhygienic handling, as fish take
large number of bacteria into their gut from water, sediment and food which may become
constituents of bacterial flora of digestive tract causing serious disease problems (Al-Harbi &
Uddin 2005).
The most important fish-borne pathogens detected in this study was Staph. aureus which was
detectable at a higher rate in both claries fish(28.6%) and in tilapia fish (22.9%). Similar
results were obtained by Metawea & Abdel-Ghaffar 2007 (23.3%) but lower results were
recorded by Simon & SanJeev 2007(17%) and Boari et al., 2008(10%). The higher
percentage of isolated Staph. aureus may be due to higher prevalence of Staph. aureus in
human being either on their skin or in their nose that create a great chance for contamination
of fish upon improper handling through persons who are not observing the basic rules of
personal hygiene. This substantiates the conclusion of Papadopoulou et al. (2007).
Staphylococcal food poisoning is caused by ingestion of food containing enterotoxins
secreted by Staph. aureus and characterized by nausea, voimition, abdominal pain and
prostration often with diarrhea but without fever, food poisoning usually develops
approximately 1-6hrs after ingestion of contaminated food (Eley, 1996).
It is clear from (Table 1) that Escherichia coli (E.coli) could be isolated at 18.9% from totally
examined fish (14.3% from tilapia and 22.9% from clarias). These findings are nearly similar
to those obtained by Onyango et al., 2009 (25.4%) and Yagoub, 2009 (23.2%) but they are
slightly lower than those recorded by Hefnawy, 1989(30%) and Maysa & Abd-Elall, 2009
(30%). The presence of E.coli is a reliable indication of fecal contamination of water either
from human and/or animal origin, faulty method of production and handling (WHO, 1998).
Moreover, the increased prevalence of E.coli may be attributed to the municipal sewage
disposal in the water course and persistence of bad habits (urination and defecation in surface
water) as well as the misuse of organic fertilizers (El-Dahshan, 2004) and transportation of
fish in dirty fishing boats or packing of fish in dirty baskets could also enhance postharvesting contamination (Onyango et al., 2009). The identified serotypes of E.coli in
examined fish samples were shown in (Table 2), the most predominant serotypes were O55:
K59 (5 strains), O111: K58 (3 strains), O86: K61 (3 strains) and O128: K67 (2 strains), such
serotypes have a great pathogenicity in the intestinal tract and cause gastroenteritis and
implicated in food poisoning outbreaks (Bryan, 1980 and WHO, 1991).
In this study, Salmonellae were isolated from tilapia & clarias fish at percentages of 5.7 and
8.6 respectively (Table 1), the results showed that the most predominant serotypes were S.
typhimurium and S. enteritidis (Table 2). Almost similar results were obtained by Mekhael
2003 (4%) and Metawea & Abd El-Ghaffar, 2007 (6.6%). On the other hand, other workers
failed to detect this pathogen as (Shaaban et al., 2001, Boari et al., 2008 and Abou-Elez,
2010). Isolation of Salmonella confirms the fecal contamination of water where the fish are
harvested, a finding which that has a public health concern (Morales et al., 2004). The risk of
acquiring Salmonella infection is greater where hygienic standards are low and where people
consume raw sea food harvested from water contaminated with sewage or feces (Rayan et
al., 1989). In Egypt, Salmonellae are widely recognized as one of the principle causes of food
poisoning outbreaks as a result of consumption of contaminated fish and fish products with
clinical symptoms in man in the form of enteritis and systemic disease (Hassan & Faten,
2003). Shigella dysentery was the lowest isolated organisms from examined fish (2.9%).
These results agree with Ibrahim et al., 2009(1.3%) and Yagoub, 2009(2.2%).The lower
isolation rate might be due to persistence of Shigella in water is lower than other bacteria and
it varies according to the geographic areas. This concept agrees with Tanios (1998).
However, food including sea food has been the cause of outbreaks of Shigellosis as a result of
contamination of raw or previously cooked food during preparation by infected or
asymptomatic carrier with poor personal hygiene (Novotny et al., 2004).
The distribution of isolated bacteria (Table 3) showed that the highest number of bacterial
isolates were recovered from skin surface, followed by intestine, whereas muscles showed
lower number of isolates at percentages of 56.3, 25 and 18.8 for tilapia fish and 54.5, 27.3 and
18.2 for clarias fish respectively. This may be attributed to exposure of the surface to different
sources of contamination. As regards to flesh of healthy fish, it is considered bacteriologically
sterile (National Academy of Science, 1985), but the presence of bacterial isolates on the
skin, muscles and intestine may reflect the effects of environmental contamination as water
condition (Cesar et al., 1999), Moreover, the isolates from skin could be mainly accounted to
the slime layer of skin and partially as a result of active bacterial multiplication and
adaptation. Such bacteria may spread from gills to the vascular system and invade the fish
flesh which are not in contact with the external aquatic environment (Shewan, 1971). This
author also assumed that the bacterial count/gram in fish muscles ranges from zero to one
thousand depending on the condition of the environment in which the fish live, degree of
exhaustion, stress during catching and the health status of the fish. In addition to enteric
bacteria, they do not seem to represent the normal flora of fish, but fish become contaminated
with them when exposed to polluted water or contamination by workers as these organisms
can be found in soil, water, sewage and intestinal tract of man and animals and these species
have been implicated in acute and chronic diarrheal diseases (Twedt and Boutin, 1979).
Shifting to the results of bacteriological examination of fish handlers as shown in (Table 4)
, it was found that out of twenty hand swabs, 4 (20%) gave positive results for Staph. aureus,
whereas 2 (10%) gave positive results for E.coli sero types as O55: K59 and O128: K67 (one
strain each). These results are supported by (Mohamed, 2001, Aycicek et al., 2004, ShoJaei
et al., 2006, Maysa & Abd-Ellal, 2009 and Abo-Elez, 2010) who isolated the same
organisms from fish handlers at different percentages. It was previously emphasized by
ShoJaei et al. (2006) that a significant number of food handlers might be nasal carriers of
Staph. aureus and consequently contaminate their hands. Moreover, high proportion
(30-35%) of healthy humans have Staphylococci in the nasopharynx and on the skin (Pedro
and Boris, 1994). Besides, about 20% of normal individuals harbor the organism in their
intestinal tract (Stewart, 1973). It was clarified by Le-Loir et al (2003) that Staph. aureus is
a main cause of gastroenteritis resulting from the consumption of contaminated food and
information of outbreaks indicates that Staph. aureus was isolated from the implicated food,
nose and hands of food handlers (Docarmo et al., 2004). So, it could be easily concluded that
the fish handlers are still a potential hazard for Staphylococcal food contamination.
Regarding to the presence of E.coli in hand swab samples; it emphasized significant fecal
contamination and indicates that food handlers were not taking enough care in hand hygiene
(Landeiro et al., 2007). From the aforementioned results, it is evident that most of bacteria
isolated from fish in this study are derived from natural aquatic environment contaminated
with sewage or from dirty hands of fish handlers, so the fish handlers and water may act as
dangerous sources of these pathogens to fish and consequently act as a vehicle of human
infection constituting therefore a potential public health problem.
It can be concluded that fish may occasionally represent a serious threat to public health as a
result of carrying several bacterial zoonoses, either in the skin, muscle or intestine. Therefore,
strict hygienic measures should be carried out during the different steps from fishing to
marketing, fish handling should be minimized and education programmes should be imposed
for fisher men, fish handlers as well as consumers and households during preparation of fish
for consumption, prevention of environmental pollution in the River Nile and its tributaries
and periodical examination of water sources as well as fish handlers in markets to ensure fish
safety.
REFERENCES
Abed-Malak, S.A.(1972):Food and feeding habits of some Egyptian fishes in lake quaron.
Bull.Inst.Ocean. and Fish. A.R.E.2, p.223-228.
Abou-Elez, R.M. (2010): Role of A therina species in transmitting some bacterial diseases to human.
M.V.SC. thesis, Fac. of Vet. Med. Zagazig University.
Acha, P.N. and Szyfres, B. (2003): Zoonoses and Communicable Diseases Common to Man and
Animals. Vol I. Bacteriosis and mycoses. 3rd ed. Pan American Health organization,
Regional office of the WHO, Washington, USA. P: 384.
Al-Harbi, A.H. and Uddin, M.N. (2005): Microbiological quality changes in the intensive of hybrid
tilapia in fresh and frozen storage condition. Letters in Applied Microbiol. 40:486-490.
Andrews, W. H. and Hammack, T. S.(1998):˝Salmonella˝. Bacteriological analytical manual, 8th Ed.
Revision A, Chapter 6. Hall. Pulp. Comp. Limited, London, U.K.
A.P.H.A (American Public Health Association,(1992): Compendium of methods for microbiological
examination of foods. 3rd Ed., American Public Health Association, Washington, D.C
Aycicek, H.; Aydogan, H.; Ayten, K.; Mehmet, B. and Ahmed, C.B. (2004): Assessment of the
bacterial contamination hands of hospital food handlers. Food control, 15:253-259.
Boari, C.A.; Pereira, G. I.; Valeriano, C.; Silva, B.C.; Morais, V.M., Piccoli, R.H. (2008):
Bacterial ecology of tilapia fish fillets and some factors that can influence their microbial
quality. Cienc. Tecnol. Aliment. Campinas 28(4):863-867.
Brayan, F. (1980): Epidemiology of food borne disease transmitted by fish. Shell fish and marine
crustaceans in United states. J. food Prot., 43:869-876.
Cesar, J.G., Teresa, M.L.; Maria, L.G., Miguel, P. and Andres, O. (1999): Bacterial microflora of
wild brown trout (Salmotroutba) wild pike (Esox lucins) and aqua cultures ranbow trout
concryhnchus myksis. J. Food prot., 62(11): 1270-1277.
Docarmo, L. S.; Cummings, C.; Linardi, V.R.; Dias, R.S.; Desouza, J.M. and Desena, M.J.
(2004): A case study of a massive staphylococcal food poisoning incidence. Food borne
pathogens and Disease, 1(4): 41-246.
Edun, O.M., Akinrotimi, O.; Opara, J.Y.; Owhonda; K.N.; Onunkwo, D.N. and Anyanwu, P.E.
(2007): Public health and economic implications of the microbial flora of cultivable fresh
water fishes. J. fisheries Int. 2(4): 274-276.
EL-Dahashan, A. R. (2004): Hygienic studies on El-Zomor canal in Giza city and its public and
animal health importance. M.V.Sc. Thesis (Animal Hygiene) Fac. of Vet. Med. Cairo
University.
Eley, A.R. (1996): Microbial Food Poisoning. 2nd Ed., Chapman and Hall, London.
Hassan, M.A. and Fatin, S. H. (2003): Hazard analysis associated with consumption of frozen fish
and fish products. 2nd ICOFHH; 21-23 October, Assuit.
Hefnawy, Y., Refai, R.S. and Sabah Moustafa (1989): Prevalence of some potential pathogens in
Nile fishes in Upper Egypt. Research Institute of Animal Health, 21(42): 101-108.
Herrera, F.C.; Santos, J.A.; Otero, A. and Garcia, Lopez ML (2006): Occurrence of food borne
pathogenic bacteria in retails prepackage portions of marine fish in spain. J. Appl.
Microbiol. 100(3):527-536.
Holt, J.H.; Krieg, N.R.; Snaeth, P.H. (1994): Bergey's Manual of Determinative Bacteriology, 9th
Ed. Williams and Wilkins, Baltimore.
Ibrahim, M.A.; Abdel-Ghany, A.E.; Emeash, H.H.; Nahed, H.Ghoneim and Gihan .K. AbedLatef.(2009):Epidemiological studies on the role of fish in transmitting some zoonotic
diseases to man.Vet.Med.J.57,No.2 p:169-185.
Janssen, W.A. (1970): Fish as potential vectors of human bacterial diseases. In A symposium on
Diseases of Fish and Shell fish. Edited by S.F. snieszko, AFS special publication No.
5, Washington, D.C. 284-290.
Kauffman, F. (1996): The Bacteriology of Enterobacteriacea Mansards, Copenhagen, Denmark.
Khalil, A. M.; Ahmed, SH. M. and Ahmed, L.S. (1990): Some microbiological studies on two
species of Nile fishes. Assiut Vet. Med. J. 23(46): 88-96.
Landeiro, M.P.A. Celina; Rogeria, C.C. Almeida; Ana, T.M.; Nascimento, Jeane.S.;
TomomasaYano and Paulo, F. Almeida (2007): Hazards and critical control points in Brazilian
seafood dish preparation. Food control, 18: 513-520.
Le Loir, Y.; Baron, F. and Gautier, M. (2003): Staphylococcus aureus and food poisoning. Genetics
and Molecular Research, 2(1): 63-76.
Macfaddin, C. (1980): Biochemical tests for identification of medical bacteria. 2 nd Ed. Williams and
Wilkins Naltmore, London.
Mansour, N.K.; Yassien, N.A.; Ibrahim, H.M. and Elmossalami, M.K. (1997): Microbial hazard
of salted om El-Kholoul (wedge shell-donax trunculus). Vet. Med. J. Giza. 45(1): 53-60.
Maysa, A.I. Awadallah and Abd Elall, A.M.M. (2009): Bacterial pollution Indicators in aquatic
environment and fish in Abu-Elakhdar sea with special reference to E.coli and its protein
profile. J. Egypt. Vet. Med. Assoc., 69(3): 157-174.
Mekhael, S.S.T. (2003): Entero pathogens in fish and its products. Ph. D. Vet. Med. Thesis. Alex.
Univ.
Metawae, Y.F. and Abd El-Ghaffar, T.A. (2007): Bacteriological studies on surface water and
tilapia fish at Minufiya Governorate. 5th Int. Sci. Conf. Mansoura 10-11 April-P: 73-95.
Mohamed, A.A.; Zaki, M.S.A.; Mowafy, L.I.M. and Abd El-Maksoud, S.A. (2001): Occurrence of
some micro organisms in water and shellfish in relation to their public health importance.
Zag. Vet. J., 29(2): 54-64.
Morales G , Blanco L, Arias ML, Chaves C. (2004): Bacteriological evaluation of fresh tilapia
(Oreochromis niloticus) coming from the northern region of Costa Rica. Arch Latinoam
Nutr. 54(4):433-7.
Naglaa, S.H.; Saleh, S.K. and Eman, M.S.Z. (2002): Hygienic quality of shrimp in Giza fish
markets. J. Egypt. Vet. Med. Assoc. 62(66): 113-120.
National Academy of Science(1985): An evaluation of the role of microbiological criteria for food
and food ingredients. National Academy press, Washington, D.C.
Novotny, L.; Dvorska, L.; Lorencova, A.; Beran, V. and Pavlik, I. (2004): Fish: a potential source
of bacterial pathogens for human beings. Vet. Med. Czech, 49,(9): 343-359.
Omer, A. A. M.; Ibrahim, M. S.; El-Haddad, A. A. and Ali, M. H. M. (2004): Environmental
consequences of the improper land application of sewage waste water disposal in Sohag,
Egypt. Soil and ground water pollution. The Sci. Conf. for Develop. and Environ. in the
Arab World, March, 23- 25, Assiut, Egypt.
Onyango, M.D.; Wandili, S.; Kakai, R. and Waindi, E.N. (2009): Isolation of salmonella and
Shigella from fish harvested from the winam Gulf of Lake Victoria, Kenya. J. Infect
Developing countries, 3(2): 99-104.
Papadopoulou, C.; Economou, E.; Zakas, G.; Salamoura, C.; Dontorou, C. and Apostolou, J.
(2007): Micrological and pathogenic contaminants of sea food in Greece. J. Food. Quality,
30: 28-42.
Pedro, N. A. and Boris, S. (1994): Staphylococcal food poisoning In Zoonoses and communicable
Diseases common to Man and Animals, 158-162, Pan American Health organization,
washington, D.C.
Popoof, M.Y. and LeMinor, L. (2003): Antigenic formula of salmonella serovars. W.H.O,
collaborating center for reference and research on salmonella. Pausteur Institue, Paris,
France.
Radwan, I.A. (1992): Studies on bacterial pathogens affecting fishes in Fayoum Governorate.
M.V.Sc. thesis, Fac. of vet. Med. Beni-Suef.
Rayan, C.A.; Hangrett-Bean, N.T. and Blake, P.A. (1989): Salmonella typhi infections in the
United States 1975-1984. Increasing role of foreign travel. Rev. Inf. Dis., 11, 1-8.
Shaaban, A.I.; Tanios, A.I. and Amany El-Bialy, I. (2001): Bacteriological examination of tilapia
fish and water from Aswan, Cairo and Lake Manzalah. J. Egypt. Vet. Med. Assoc. 61, (4):
241-249.
Shewan, J.M. (1971): Bacteriological standards for fish and fishery products. Chem. Ind, Feb. 7:193199.
ShoJaei, H.; Jafar, S. and Masoud, A. (2006): Efficacy of simple hand washing in reduction of
microbial hand contamination of Iranian food handlers. Food Research International,
39:525-529.
Simon, S.S. SanJeev, S. (2007): Prevalence of entero toxigenic staphylococcus aureus in fishery
products and fish processing factory workers. Food control, 18(12), 1565-1568.
Stewart, F.S. (1973): Bigger bacteriology and immunology for students of medicine. 9th Ed. The
English Language Book society (ELBS) and Bailliere, Tindall and Cassell.
Tanios, A.I. (1998): Bacteriological hazards of recycled waste water. Seuz Canal. Vet. Med. J, 1(2):
267-273.
Twedt, R.M. and Boutin, B.K. (1979): Potential public health significance of non Escherichia
Coliforms in foods. J. food Protection. 42(2): 101.
W.H.O. (1991): World Health organization surveillance program for control of food borne infections
and intoxication in Europe 1991: out breaks of E.coli in USA, News Letter.
W.H.O (1998): Surveillance program for control of food borne infection and intoxication. FAO/WHO
Cooperating Center for Research and Training in Food Hygiene and Zoonoses of Fedral
Institute for Health. No. 56 June, 1998.
Yagoub, S.O. (2009): Isolation of enterobacteriaceae and pseudomonas spp. from raw fish sold in fish
market in Khartoum state. J. of Bacteriology Research Vol 1(7) P: 85-88.
Yagoub, S.O. and Ahmed, T.M. (2004): Pathogenic microorganisms in fresh water samples
collected from Khartoum central market. Sudan. J. Vet. Sci Anim. Husbandry. 43(1-2):
32-37.