Document Type : Research article
Authors
1 Animal Health Research Institute, Assiut Laboratory.
2 Animal Health Research Institute, Assiut Laboratory
Abstract
Keywords
Survey on the incidence and toxigenicity of Yersinia enterocolitica in some meat products with confirmation using
PCR
Ghada M.Mohamed, Lubna M. Ebraheem and Manal H.Thabet
Animal Health Research Institute, Assiut Laboratory.
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ABSTRACT
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Received at: 25/3/2012
Accepted: 12/4/2012
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A total of 120 samples of meat products including luncheon, beef burger, sausage and basterma (30 of each) were collected from different supermarkets and shops in Assiut city to study the prevalence of Yersiniaspp.in these products and confirmation of the isolated Y.enterocolitica by PCR as well as the virulence of this organism.The obtained results showed that the incidence of Yersinaia spp. wase 6.6, 10, 20 and 3.3% in examined luncheon, beefburger, sausage and basterma samples respectively.The recorded data revealed that the incidence of Y.enterocolitica in the same products was 6.7, 6.7, 13.3 and 3.3% respectively. Concerning, Y.intermedia, it could be isolated from 3.3% of sausage samples only while Y.kristensenin was isolated from beef burger and sausage in percentage 3.3% for each. The biotyping results of Y.enterocolitica in this study shown that the two strain of Y. enterocolitica isolated from luncheon and the one strain which was isolated from basterma were of biotype 3 while one strain of Y.enterocolitica which isolated from beefburger was Biolype 2 and the other strain was of Biotype 3. Also the four strains isolated form sausage were found to be two strains belonged to biotype 2 and the other two strains belonged to biolype3. Confirmation of Y.enterocolitica was done by suing PCR while the virulence was carried out by using Auto-agglutiration test. The results revealed that 4 from 9 of the isolated Y.enterocolitica had the ability to cause turbidity or clumbing (virulent) in percentage of 44.4%. The other 5 strains 55.5% were avirulent. The public health importance of the organism was discussed and the suggestive measures for safe healthful products were outline.
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Key words: Meat products, yersinia entero colitica, PCR.
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دراسة مدي تواجد وسمية ميکروب اليرسينيا انتيروکوليتکا في بعض منتجات اللحوم مع التاکد منه بإجراءاختبار انزيم البلمرة المتسلسل
غادة محمد محمد , لبنى محمد ابراهيم , منال حسن ثابت
أجريت هذه الدراسة على 120 عينة من منتجات اللحوم (اللانشون ، البيف بيرجر، السجق، البسطرمة) 30 من کل نوع والتى جمعت من محلات البقالة والسوبر مارکت المختلفة في محافظة أسيوط لمعرفة مدى تواجد ميکروبات االيرسينيا وتصنيفها والتأکد من ميکروب االيرسينيا انتيروکولوتيکا باختبار انزيم البلمرة المتسلسل واختبار مدى سمية هذا الميکروب المعزول: حيث تم عزل ميکروبات االيرسينيا بنسبة 6.7 ، 10، 20، 3.3% من عينات اللانشون والبيف بيرجر والسجق والبسطرمة بالترتيب وقد أوضحت الدراسة أن نسبة عزل ميکروب االيرسينيا انتيروکوليتکا في نفس العينات کانت 6.7، 6.7، 13.3، 3.3% بالترتيب وقد تم عزل ميکروب اليرسينيا انترميديا بنسبة 3.3% من عينات السجق فقط بينما أمکن عزل ميکروب اليرسينيا کريستنسيناي من عينات البيف بيرجر والسجق بنسبة 3.3% لکل منهما وقد دلت الدراسة على أن عترتي اليرسينيا انتيروکولتيکا التي عزلتا من اللانشون والعترة التي عزلت من البسطرمة صنفوا على أنهم biotype 3أما بالنسبة للعترات التي عزلت من البيف بيرجر فقد وجد ان عترة واحدة صنفت على أنها biotype 2 والعترة الأخرى صنفت على أنها biotype 3 بينما العترات التي عزلت من السجق (4عترات) فقد وجد أن عترتين صنفتا على انهما biotype 2 وعترتين صنفا على أنهما biotype 3 هذا وقد تم إجراء أنزيم البلمرة المتسلسل للتأکيد من وجود ميکروب اليرسينيا انتيرکولتيکا وعند اختبار مدى سمية ميکروب اليرسينيا انيترکولتيکا ا باختبار Autoaglutination test اتضح أن 4 من 9 من الميکروبات المعزولة حققت قدرتها على إحداث تعکير وتجلط بنسبة 44.4% بينما باقى الميکروبات المعزولة (5ميکروبات) لم تحقق قدرتها على إحداث نتائج ايجابية بنسبة 55.5% هذا وقد تم مناقشة مدى خطورة هذا الميکروب على صحة المستهلک والطرق المقترحة للحد منه.
Introduction
Meat and meat products are subjected to contamination with several types of microorganisms from different sources during the period elapses from the time of slaughtering, preparation, processing and cooking. High incidence of bacteria food poisoning occurred in last years due to Salmonella and Yersinia enterocolitica infection (Greenwood and Hooper, 1990).
The genus Yersiniuis a member of the family Enteriobacteriaceae, contain 11 spp. including. Y.pestis, Y.pseudotuberculosis and Y.enerocolotica wich are pathogenic for humans and animals. Y. frederiksenii, Y.intermedia, Y.kristensenii, Y.aldova, Y. rohdei, Y. mollareti and Y. bercovier are widespread in nature but are not usually associated with diseases. Y. ruchei is a fish pathogen, which cause red mouth disease (Carnial and Mollaret, 1990).
Y.enterocolitica is a Gram-negative, facultatively anaerobic, rod, shaped bacterium. Optimal growth occurs at 30-37ºC but the bacterium is psychrotrophic and can grow in food at refrigeration temperature (4ºC) (Bercovier and Mollaret, 1984).
Yersinia species consists of pathogenic and nonpathogenic spp. The virulence of Y.enterocolitica is associated with biogroup, serogroup and geographic distribution. However, Y.enterocolotica strains have been distributed in 5 biogroup according to their biochemical properties. Strains of biogroups 2,3,4 and 5 (except 3A and 3B) are restricted to a small number of serogroups (0:1; 0:2, 0:3, 0:5, 27, 0:9) and are generally isolated from a specific host. Strains of serogroups 0:3; 0:9; and 0: 5.27 are the major causes of human infections in Europe, Japan, Southern Africa and Cardada (Carter, 1975).
Y.enterocolitica is a zoonotic microorganism capable of causing yersiniosis in humans through direct,or in direct contamination of food by faeces or urine. Meats can be contaminated by faecal materials during slaughtering and dressing (Stern, 1981; Tudor et al., 2010).
The disease yersiniosis, which is caused by this orgaism is typically detected after infection by examination of a patients stool. It occurs often in children 5-15 years of age or in older adults that may have weakened immune systems. The symptoms which take about 4-7 days to manifest and can last from 1-3 weeks, are nausea, diarrhea and abdominal pain mesenteric lymphadenitis, acutentritis, arthritis and skin rash called "erythema nodosum" (Robert, 2008).
Microbac laboratories had developed an assay to quickly test for and identify Y.enterocolitica in client samples by using PCR technology which is based on DNA detection as a molecular techniques (Robert, 2008 and Tudor et al., 2010).
Using PCR is not only the time and cost saving for detecting the pathogen but the specificity and sensitivity of the analysis which doesn't require long enrichments or confirmation step (Robert, 2008).
A simple system for determinating the virulence of Y.enteroclotica based on their observation that the virulent strain of Y.enterocolitica agglutinated when grown on tissue culture media while avirulent strains didn't exhibit the agglutination property (Laird and Cavanaugh, 1980). Plasmids containing virulence genes may be lost during culture and conformational procedures. Temperature above 30ºC, is known to cause a loss of virulence plasmids in pathogenic Y.enterocolitica but plasmid loss may also occur as a result of other less defined circumstances (Johnson, 1998).
Most clinical isolates of Y.enterocolitica produce a heat-stable enterotoxin. However, this enterotoxin probably doen't play an important role in Y.enterocolitica infection because most Y.entercolotica don't produce enterotoxin in vitro at temperature greater than 30ºC and because strains that doesn't produce enterotoxin in vitro caused diarrhea in experimentally infected mice (Scheimann, 1989).
The purpose of the present investigation was designed to evaluate the prevalence of Yersinia enterocolitica in some meat products (sausage, beefburger, basterma and luncheon), confirmation of the isolated strains by PCR and carrying out the virulence of Y.enterocolitica recovered from the examined samples.
Materials and Methods
Collection and preparation of samples:
A total of 120 randam samples of meat products including30 of each luncheon, beefburger, sausage and basterma were collected from different supermarkets and shops in Assiut Governorate. Each sample was put in a sterile plastic bag. The collected samples were transferred directly to the laboratory under aseptic conditions without any delay where they were prepared for examination. Each sample was aseptically and carefully freed from its casing and mixed thoroughly in sterile mortar.
Enrichment procedure:
Twenty five grams of each sample were weighted aseptically and 225ml of trypticase soy broth were added then the mixture was blended for 2 min. The samples were incubated at 4ºC for 14 days as cold enrichment as recommended by speck (1984).
Isolation procedure (Schiemann, 1979):
Loopfuls from the previously incubated enrichment broth were streaked onto Cefulodin Irgasan Novobiocin (CIN) agar and incubated at 22-23ºC for 24-48 h. The colonies which showed dark red centre bulls eye" with a translucent border were picked up and subcultured on nutrient agar slants and incubated at 37ºC for 24h for further confirmation and identification.
Identification of presumptive colonies:
Suspected colonies were confirmed by Gram's stain, kliger Iron Agar, Christensen's urea ager, Vogas-Proskauer,S fermentation test, Indole production test and Simmons citrate according to Speck, (1984).
Biochemical differentiation:
The following test were done:
Vogas-Proskauer, Sucrose, L.rhamnose, Dmelibiose, Indole, D.raffinose and Simmons citrate as described by Bercovier et al. (1980).
Biotyping of Yersinia enteroclitica:
Y.enterocolitica strains were biochemically differentiated into 5 categories according to Wauters, Biotype Scheme as cited in Speak (1984), which included lecithinase, Indole, xylose and trehalsoe test. It is most widely used and is helpful in tracing the source of epidemic strains.
Molecular analysis:
Total genomic DNA and PCR amplifications: (for the nine strains of confirmed isolates) were used as described by Wang et al. (1994) for Yersinia enteroclitica-specific identification, two primers pairs were used. The primer's sequence, the target, the PCR products size and the references, are listed in Table 1.
The oligonucletoide primers: were synthesized by Universal DNA Inc. (Tigard, OR, USA) and were unpurified grade.
PCR assy: PCR amplification were performed using Master Max. The reaction mixture contained a total volume of 25µL in 0.5mL tubes included: 12.5µL of Master Max., 2.0µL of primerYE-1, 2.0µL of primer YE-2,µL of free water and 6.5µL of Template DNA.
Cycling conditions:one cycle of 94ºC for 15s, then35cycles of 94ºC for 3s, 50ºC for 10s and 74ºC for 35s at the transition speed 5-9, and finaly, one cycle at 74 ºC for 2min and 45ºC for 2s, The PCR products (6-10µ/of each) were separated by electrophoresis in 2% agarose gels containing ethidium bromide (1µg m/-1) (Wang et al., 1994).
Detection of PCR products: The gel was stained with ethedium bromide and amplicans were visualized on UV Tran illuminator. The 1-KB was used as molecular size marker.
Table 1: Oligonucleotide sequences used for ideification of Yersinia enterocolitica by PCR:
|
Target gene |
Primer sequence (5' -3') |
Product size |
Reference |
|
Enterotoxin gene |
YE-F,CTG TCT TCA TTT GGA GCA TTC YE-R,GCA ACA TAC ATC GCA GCA ATC |
159bp |
Ibrahim et al. (1992) |
Detection of pathogenicity of Yersinia enteroclitica isolates recovered from the examined samples:
1- Biochemical tests:
Only 4 biochemical tests are necessary for identifying potentially pathogenic form of Y.enterocolitica which included Kligler Iron Agar, Urea hydrolysis, Sucrose fermentation and Salicin fermentation according to Schiemenn and Devenish, (1982).
2- Autoagglutionation test:
As recommended by A.O.A.C.,(1984) the culture of each isolate of Y.enteroclitica, previously grown on Trypticase Soy Agar at 22ºC for 48h, was inoculated into each of two tubes containing 4 ml of UR-VR broth. One tubes was incubated at 22ºC and the other tube was incubated at 35ºC for 24h. Either turbidity in tubes incubated at 22ºC or clumbing of bacteria along the walls of the tubes or on their bottom with clear supernatant fluid in tubes incubated at 35ºC were considered positive for auloagglutination test.
Results
Table 2: Incidence and distribution of Yersinia species isolated from the esamined meat products
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Types of samples |
No. of exam. |
Yersinia spp. |
Y.enterocolitica |
Y.entermeida |
Y.kristensenti |
||||
|
+ve |
% |
+ve |
% |
+ve |
% |
+ve |
% |
||
|
Luncheon |
30 |
2 |
6.7 |
2 |
6.7 |
0 |
0.0 |
0 |
0.0 |
|
Beefburger |
30 |
3 |
10 |
2 |
6.7 |
0 |
0.0 |
1 |
3.3 |
|
Sausage |
30 |
6 |
20 |
4 |
13.3 |
1 |
3.3 |
1 |
3.3 |
|
Basterma |
30 |
1 |
3.3 |
1 |
3.3 |
0 |
0.0 |
0 |
0.0 |
|
Total |
120 |
12 |
10 |
9 |
7.5 |
1 |
0.8 |
2 |
1.7 |
Table 3: Biotyping of the isolated Y.erterocolitica from the examined meat products
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Types of samples |
No. of +ve |
Biotype 2 |
Biotype 3 |
||
|
No. |
% |
No. |
% |
||
|
Luncheon |
2 |
0 |
0.0 |
2 |
22.2 |
|
Beef burger |
2 |
1 |
11.1 |
1 |
11.1 |
|
Sausage |
4 |
2 |
22.2 |
2 |
22.2 |
|
Basterma |
1 |
0 |
0.0 |
1 |
11.1 |
|
Total |
9 |
3 |
33.3 |
6 |
66.6 |
Identification by PCR:
|
Lane1-9: +ve for Yersinia entrocolitica.
M: Molecular size Marker(1-KB). |
|
600 500 400 300 200
100 |
Fig. 1: Results of PCR for detection of Y.enterocolitica in the examined meat products.
Table 4: Pathogenicity of Y.enteroclitica strains isolated from the examined meat products.
|
Types of exam samples |
No. of exam. |
Reactions |
|||||||
|
+++ve |
++ve |
+ve |
-ve |
||||||
|
No. |
% |
No. |
% |
No. |
% |
No. |
% |
||
|
Luncheon |
2 |
- |
- |
1 |
11.1 |
- |
- |
1 |
11.1 |
|
Beefburger |
2 |
- |
- |
1 |
11.1 |
- |
- |
1 |
11.1 |
|
Sausage |
4 |
1 |
11.1 |
- |
- |
1 |
11.1 |
2 |
22.2 |
|
Basterma |
1 |
- |
- |
- |
- |
- |
- |
1 |
11.1 |
|
Total |
9 |
1 |
11.1 |
2 |
22.2 |
1 |
11.1 |
5 |
55.5 |
+ + + ve = High degree of pathogenicity
+ + ve = Moderate degree of pathogenicity
+ ve = Weak degree of pathogenicity
-ve = Non pathogenic
Table 5: Incidence distribution of pathogenic and non pathogenic Y.enteroclitica isolated form the examined meat products
|
Types of samples |
No. of +ve |
pathogenic |
Non pathogenic |
||
|
No. |
% |
No. |
% |
||
|
Luncheon |
2 |
1 |
11.1 |
1 |
11.1 |
|
Beef burger |
2 |
1 |
11.1 |
1 |
11.1 |
|
Sausage |
4 |
2 |
22.2 |
2 |
22.2 |
|
Basterma |
1 |
- |
- |
1 |
11.1 |
|
Total |
9 |
4 |
44.4 |
5 |
55.5 |
Discussion
Y.enterocolitica is found world wide. The organisms has been recovered from a wide variety of animals, foods and water. The recorded data all over the world suggest that outbreaks of foodborne yersiniosis are rare (Gracey et al., 1999).
1- Prevalence of Yersinia spp. in examined some meat products:
The finding outlined in Table 2 indicated that Yersinia spp. were isolated from 2, 3, 6 and 1 out of 30 examined samples from each of luncheon, beefburger, sausage and basterma with an incidence 6.7, 10, 20 and 3.3% respectively. Abdel-Malek (2001) could isolate Yersinia spp. from luncheon, beefburger and sausage samples in percentage 8.6, 2.9 and 14.3% respectively which disagree with the obtained results. The total incidence of Yersinia spp. recovered from all, the examined samples in this study was 10% which is disagree to that recorded by Dalmas and Vidon(1985) (33.3%), Tassinari et al. (1994) (40%)and Escudero et al. (1996) (75%).
The variation of incidence between the investigators may be due to the differences in the geographical distribution of Yersinia spp. and methods of isolation. The true incidence of yersiniosis is uncertain for various reasons: few outbreaks of foodborne illness are investigated, yersiniosis has recently known to be food or water borne and a long incubation period may be required using cold enrichment to recover certain strains from food (IC MSF, 1996).
The biochemical reaction of isolated strains of Yersinia spp. were differentiated into: Y.enterocolotica, Y. Intermedia and Y.kristensenii as shown in Table 2
I - Y.enterocolotica
The present results recorded in Table 2 revealed that Y.entocolotica was recovered from 2,2,4 and 1 out of the 30 examined samples from each of luncheon, beefburger, sausage and basterma in percentage 6.7, 6.7, 13.3 and 3.3% respectively with a total incidence of 7.5%. The obtained results of Y.enterocolotica of luncheon was nearly similar to that recorded by Abou El-Ela (1994) and Ahmed and Mohamed (1998) who recorded 6.6% and 7.5% respectively while it was higher than that recorded by Abdel-Malek (2001) (2.9%) and lower than El-Gohary et al. (1993) (10%).On the contrary Abd El-All (1993) Abd Eaziz et al. (1996) and Ahmed (1996) failed to detect Y.enterocolotica in luncheon.
The incidence of Y.enterocolitica in beefburger samples in the present study was higher than that obtained by Abd El-Monem; Saad (1988) (2%), Nortji et al. (1998) (3.9); Abdel-Malek (2001) (2.9%), but it was lower than Abd El-All (1993) (8%); El-Taher (1998) (20%). The lower incidence of Y.enterocolotica in both luncheon and beefburger may be attributed to the addition of spices and nitrite which have a bacterostatic affect (Libby, 1975), in addition to, the curing processing of the products which play a greet effect of the survival and multiplication of the existing microorganisms (Fehlhaber 1981).
Evaluation of sausage samples for the existence of Y.enterocolitica in this study are nearly similar to those reported by El-Gohary et al. (1993) (14%); Abdel-Malek (2001) (14.3). A higher incidence was recorded by Abd El-All (1993) (20%), Khalafalla (1995) (15%); Garcia Lopez et al. (1998) (19.9%) whereas lower findings were detected by Nortji et al. (1998) (2%), Vural et al. (1996) (0.8%); El Taher (1998) (10%).
The presence of Y.enterocolotica in high incidence in the examined sausage samples may be attributed to the bad hygienic conditions during manufacturing of the product as well as contamination of raw materials, contact surfaces and casing (Abd El -Malek, 2001).
The prevalence of Y.enterocolitica in the examined basterma samples was nearly agreement to that recovered by Abou El-Ela (1994). However, some investigators (Abd El-Aziz et al., 1996; Ahmed 1996) failed to detect Y.enterocolitica in the examined luncheon, beefburger, sausage and basterma collected from different shops in Cairo and Giza.
The failure to detect Y.enterocolotica in some food products may be due to the acidic condition of such products or presence of other microbial growth which lowered the pH because the pathogen is sensitive to acidic condition (Feeley and Schiemenn, 1984).
II- Y.intermedia:
From the data shown in Table 2, Y.intermedia was isolated from 1 out of 30 examined sausage samples in percentage of 3.3% with a total incidence 0.8%, wherease the pathogen could not be detected in luncheon beefburger and basterma samples. Many investigators such as Inoue and Kurose (1975), Leistner et al. (1975); Karib et al. (1994) recorded the occurrence of Y.intermedia in the examined beefburger, furthermore, El-Gohary et al. (1993) succeeded to isolated Y.intermedia from 4% of the examined luncheon and sausage samples.On the other hand AbdEl-Malek (2001) failed to detect Y.intermedia in the examined luncheon, beefburger and sausage samples.
III-Y.kristensenii:
Y.kristensenii is isolated from one sample out of 30 examined samples from both beefburger and sausage with an incidence of 3.3 and 3.3% respectively and a total incidence of 1.7%.The organism was not detected in the examined luncheon and basterma samples while AbdEl-Malek (2001) succeeded to isolate Y.kristensenii from luncheon in percentage 5.7% .Many researchers as Inoue and Kurose (1975), Leistner et al. (1975) and Karib et al. (1994) reported the prevalence of Y.kristensenil in the examined raw beef.
Morever, The variation between the present findings and those obtained by other investigators may be attributed to several factors including enrichment broth and plating media used as previously reported by Schiemann and Wauters (1992).
2- Biotyping and virulence of Y.enterocolitica:
A- Biotyping of Y. enterocolitica:
From the data outlined in Table 3, it was found that all Y.enteroclitica isolated from luncheon (2 strains) belonged to biotype3, while the 2 strains which were recovered from beefburger: one of them belonged to biotype2 and the other was belonged to biotype 3. Morevere the 4 strains of Y.enterocolotica which obtained from sausage were belonged to biotype 2 (2strains) and biotype 3 (2strains). On the other hand, the only strain of Y.enterocolotica which was recovered from basterma belonged to biotype 3. Iit was apparent that Y.enterocotica biotype 3 was the most frequent biotype which represent 66.6% of all the tested Y.enterocolotica isolates.
In Egypt, Fady (1993) recorded that Y.enterocolitica biotype 2 was isolated from fresh sausage samples. Also Abou El-Ela (1994) identified Y.enterocolitica biotype 4 recovered from luncheon.
The strains which identified biochemically as Yersinia enterocolotica were subjected to PCR test .The result indicated that all strains were positive for Yersinia enterocolitica.
B- Virulence ofY. enterocolotica recovered from examined samples:
The results presented in Table 4 revealed that one out of two Y.enterocoltica strains isolated from the examined luncheon samples was regarded as of moderate degree of pathogenicity depending on their reactions on autoagglutination test and the other strain was negative for autoagglutination test (non-pathogenic). Whereas one strain of Y.enterocototica out of 2 two strains recovered from beefburger was pathogenic with moderate degree, while the second strain was negative for autoaglutination (non pathogenic). Concerning the virulence of Y.enterocolitica strains detected in sausage samples, it was found that one out of four isolated strains was of high degree of pathogenicity, one was weak degree of pathogenicity and the other two strains were non pathogenic. On the other hand the only one strain of Y.enterocolitica recovered from basterma samples was non pathogenic.
Regarding the total incidence of the pathogenicity of Y.enterocolitica strains isolated from all the examined samples, it was cleared in Table 4 that, 1 (11.1%), 2 (22.2%), 1 (11.1%) and 5 (55.5%) were tabulated as high degree (+ + +ve), moderate degree (+ +ve), weak degree (+ ve) of pathogenicity and non pathogenic (-ve) respectively.
The summarized data in Table 5 emphasized that 4(44.4%) out of 9 Y.enterocolitica strains recovered from the examined samples were pathogenic, whereas 5 (55.5%) were found to be non pathogenic.
In fact, it was reviewed that only Y.enterocditica was considered as pathogenic for humans, while the other species, such as Y.intermedica and Y.kristensenii appeared to be primarily environmental strains that do not cause human illness (Feeley and Schiemann, 1984).
The recovery of pathogenic Y.enterocolotica is contingent upon a number or factors including the amount and level of back ground flora coming from enrichment and plating, the level of pathogenic Y.enteroclotica and the numbers of non pathogenic Y.enterocolotica present in the sample (Johnson, 1998).
The autoagglutination test is suitable for routine use and has been described as the most useful test for identifying pathogenic strains of Y.enterocolotica as mentioned by Varnam and Evans (1991).
In conclusion the information given by the achieved results revealed that some meat products were contaminated by Yersinia spp. and this may reflect the lack of hygienic supervision. Therefore these products play a significant role in the epidemiology of yersiniosis. So strict hygienic measures during manufacturing transportation and storage, properly heated for cooked food and avoid cross contamination with animal and human feces should be recommended to avoid contamination with Yersinia spp.
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