OCCURRENCE OF SOME MICROORGANISMS IN RELATION TO PUBLIC HEALTH IN KAREISH CHEESE

Assiut Vet. Med. J. Vol. 52 No. 111 October 2006

Dept. of Food Control, Fac. Vet. Med., Zagazig Univ., Egypt.

OCCURRENCE OF SOME MICROORGANISMS IN RELATION TO PUBLIC HEALTH IN KAREISH CHEESE

(With 4 Tables)

By A.A. BAHOUT and A.H. MOUSTAFA* * Dept. of Bacteriology, Animal Health Research Institute, Mansoura Lab.

(Received at 23/9/2006)

تواجد بعض الميکروبات ذات الصلة بالصحة العامة في الجبن القريش

على أحمد على بحوت،عادل حسانين محمود مصطفى

جمعت من الأسواق المحلية بمحافظة

أجريت الدراسة على خمسين عينة من الجبن القريش الدقهلية (مصر) خلال ربيع ۲۰۰۵ وذلک لتحديد مدى تلوثها بالميکروبات ذات الصلة بالصحة العامة بالاضافة إلى تعيين النسبة المئوية للحموضة والرطوبة وملح الطعام. وقد أظهرت النتائج أن متوسط النسبة المئوية للحموضة والرطوبة وملح الطعام في العينات کانت ۱٫۵% ، ۹۱٫۲% ، 4 ,5% على التوالي، بينما بلغ متوسط ميکروبات الايشريشيا کولای والمکور العنقودي الذهبي والباسيلس سيرس والکلوسترديم بيرفرنجينز والمکورات

لکل جرام

۱۰X۵,۷، ۱۰۶۱,۹،۱۰x۱,۸ ،۱۰x۳

,

*۱۰

۶,۸

السبحية المعوية من الجبن على التوالي. ولقد تم عزل ميکروب اليارسينيا انتيروکوليتکا من العينات بنسبه

، بينما لم يتم عزل ميکروبات السالمونيلا. کما أثبتت التحليلات الإحصائية أن هناک

%4 علاقة ارتباط بين النسبة المئوية للحموضة والرطوبة وملح الطعام وإعداد الميکروبات المختلفة في عينات الجبن. هذا وقد تمت مناقشة النتائج من الناحية الصحية والاقتصادية واقتراح ما يجب اتباعه من إجراءات من الناحية الصحية لضمان جودة المنتج والحفاظ على صحة المستهلک.

SUMMARY

Fifty random samples of Kareish cheese were collected from local markets in Dakahlia Province, Egypt during spring of 2005 to be examined chemically and bacteriologically. The mean acidity %, moisture % and sodium chloride % of examined kareish cheese samples were 1.5, 61.2 and 5.4 respectively. While, the mean counts/g of examined samples for Escherichia coli, Staphylococcus aureus, Bacillus cereus, Clostridium perfringens and Enterococci were 3.8x10', 3.4x104,

Assiut Vet. Med. J. Vol. 52 No. 111 October 2006

1.8x104, 1.9x10% and 5.7x10 respectively. Yersinia enterocolitica was isolated from 4% of examined kareish cheese samples, while Salmoneliae failed to be detected. Significant correlation was found between acidity %, moisture % sodium chloride % and different bacterial counts in kareish cheese. The public health importance of the isolated organisms as well as sanitary measures for improving the quality of kareish cheese were discussed.

Key words: Kareish cheese, milk products, pathogens, acidity, NaCl.

INTRODUCTION

Kareish cheese is a kind of soft cheese which is manufactured from raw buffaloe or cow's milk in farmer's houses. It is considered the main protein supplement to farmers and most people in Egypt. The main sources of pathogenic bacteria in cheese are contaminated raw milk, food handlers, dust, utensils and insects (Robinson, 1990).

The growth of pathogenic bacteria in dairy products is influenced by thermal teratment during processing and by conditions within the product such as pH, water activity, presence of inhibitory substances or competitive microorganisms (Ray, 1996).

Milk and its products like cheese are involved in food poisoning outbreaks. The bacteria which commonly cause food poisoning due consumption of dairy products in Canada, Britain and many other countries are Salmonellae, Staphylococcus aureus, Bacillus cereus, Clostridium perfringens (Todd, 1985 and Trickett, 1986).

The manufacture, handling and distribution of Kareish cheese by farmers render it of public health hazards. The present study was conducted to throw light on the occurrence of some microorganisms in relation to public health importance in Kareish cheese marketed in Dakahlia Province.

MATERIALS and METHODS

Fifty random samples of Kareish cheese (each about 50 grams) were collected from local markets in Dakahlia Province, during spring of 2005.

The collected samples were transferred directly to the laboratory in ice box to be examined chemically and bacteriologically. A- Chemical examination:

The content of water, sodium chloride and titratable acidity of kareish cheese samples were determined according to the methods

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recommended by Association of Official Analytical Chemists "A.O.A.C." (1984). B- Bacteriological examination:

Each sample was thoroughly mashd in a sterile mortar. Eleven grams of prepared cheese sample were aseptically homogenized with 99 ml of sterile 2% sodium citrate solution at 40C°, serial dilutions of the homogenates were prepared.

Counts of Escherichia coli, Staphylococcus aureus, Bacillus cereus, Clostridium perfringens and Enterococci/g were determined according to A.P.H.A. (1985).

Suspected colonies were isolated and subjected to confirmatory tests according to Krieg and Holt (1984) and Roberts et al. (1995).

Isolation of salmonella spp. was carried out according to Cowan and Steel (1993). e Isolation of Yersinia enterocolitica was done according to the technique adopted by Walker and Gilmour (1986) and the isolates were identified according to the methods recommended by Krieg and Holt (1984). The obtained results were statistically analyzed according to Snedecor and Cochran (1989).

RESULTS

Table 1: Titratable acidity %, moisture % and sodium chloride % in

examined Kareish cheese samples (n =50).

Min.

0.9

Chemical examination

Titratable acidity% Moisture % Sodium chloride %

Max.

2.4 65.0 9.1

Mean

1.5 61.2 5.4

= S.E.M.

0.06 1.3 0.4

55.0

2.5

Table 2: Bacterial counts/g in examined Kareish cheese samples (n=50).

+ ve samples

Count /g. Bacterial counts

No.

Min.

Max. Mean S.E.M. Escherichia coli

25 50.0 70 7.6x104 | 4.8x10 1.2x103 Staphylococcus aureus

28.0 1.1x102 6.5x105 3.4x104 0.9x104 Bacillus cereus

42.0 4.0x103 2.1x105 1.8x104 0.4x104 Clostridium perfringens

20.0 86 3.1x102 1:9x102 0.2x102 Enterococci

100.0

9.2x10 3.5x1075.7x106 1.6x10 Yersinia enterocolitica

4.0 Salmonella spp.

0.0

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Table 3: Frequency distibution of examined Kareish cheese samples

based on their bacterial counts/g.

Bacterial counts

10-108

10-102 2 (8)

E. coli Staph.aureus B. cereus Cl. perfringens Enterococci

Number (%) of samples with count in range 102-103 | 102-104 104-109 105-106 106-107 5 (20) | 11(44) 7(28) 3(21.43) 3(21.43) 5(31.71) 3(21.43)

9(42.9) 8(38.1)

4(19) 7(70)

9(18) 9(18) 7(14) 20(40)

3 (30)

5(10)

Table 4: Correlation between acidity %, sodium chloride % moisture %

and different bacterial counts in examined Kareish cheese samples.

Escherichia Staphylococcus Bacillus cereus Clostridium coli aureus Count Count perfringens Count

Count

Enterococci

Count

Bacterial

counts Chemical analysis Acidity% Na C1 % Moisture%

r=-0.689* r=-0.749** r=0.673**

r= -0.744** r=-0.831** r= 0.743**

r=-0.735** r=-0.825** r= 0.743**

r=-0.878** r= -0.940** r= 0.886**

r=-0.605** r=-0.693** R= 0.591*

* Significant (P<0.05) ** Highly Significant (P<0.01)

DISCUSSION

Average values of titratable acidity %, moisture % and sodium chloride % of examined kareish cheese samples were 1.5, 61.2 and 5.4%, respectively (Table 1).

The results agreed to some extent with those reported by Ahmed et al. (1987), Moustafa (1988) and Abd-El-Haleem (1990). E. coli could be detected in 50 % of examined kareish cheese samples with a mean value of 4.8x10'+1.2x10 /g (70-7.6) x104). Most of the samples (72 %) lay within the range of 10 to 10 (Table 2 and 3). Higher results were reported by Al-Ashmawy et al. (1994) and Ebrahim (1998).

The presence of E-coli in food is considered as on indicator of faecal cotamination. Moreover, particular strains are known to induce severe diarrhea in both infants and young children as well as cases of food poisoning and gastroenteritis among adult consumers (Eley, 1996).

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Staphylococcus aureus was detected in 28% of Kareish cheese samples, with mean count of 3.4x104 +0.9x104 CFU/g (1.1x102 6.5x10%). The highest frequency percentages (31.71 %) lay within the range of 109 and 10 (Tables, 2 and 3).

Nearly similar counts were reported by Al-Ashmawy et al. (1994), while higher counts were reported by Kaldes (1997) and Halawa and Moawad (1999).

Staph. aureus is one of the most important aetioloigical agent of bovine and ovine mastitis and a high percentage of food handlers working in dairy industries are nasal carriers of Staph. aureus (Garcia et al., 1986).

Staph. aureus has a potential importance to the public health because of its ability to produce enterotoxins, resulting in staphylococcal food poisoning (Hill, 1983).

Bacillus cereus could be detected in 42% of examined Kareish cheese samples, with a count ranged from 4.0x10 to 2.1x10° /g and an average count of 1.8x10*+ 0.4x104. Most of samples (81.0%) lay within the range of 109 and 10 (Tables, 2 and 3).

These results agreed with those of Khalil (1997) and Halawa and Moawad (1999). Bacillus cereus was recognized as a food poisoning pathogen and could produce diarrhoeal toxin (Eley, 1996). The results presented in Table (2) showed that 20% of examined Kareish cheese samples were contaminated with Clostridium perfringens. The maximum count /g was 3.1x10%, the minimum count was 86, with a mean value of 1.9x102 +0.2x102. The highest frequency distribution (70%) lays within the range of 102 and 10° (Table 3).

Nearly similar results were reported by Amer et al. (1996). Clostridium perfringens was responsible for food poisoning among consumers duo to consumption of cartain dairy products (Eley, 1996).

The presence of Cl. Perfringens in dairy products was indicative of faecal or soil contamination and it was associated with spoilage problems, late blowing, in cheese (Robinson, 1990).

Enterococci could be isolated from all examined Kareish cheese samples with a mean count of 5.7x10 +1.6x10 (9.2x103 -3.5x10]. Most of the samples (54%) lay within the range of 109 and 10' (Tables, 2 and 3). Nearly similar results were recorded by Moustafa (1988) and El-Kholy et al. (1995), while higher results were reported by Kaldes (1997) and Halawa and Moawad (1999).

The presence of enterococci in milk and its products was indicative of faecal contamination and also was associated with some

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cases of food poisoning outbreaks (ICMSF, 1978 and Sedova et al., 1981).

Yersinia enterocolitica could be isolated from two samples of the examined Kareish cheese samples, while Salmonella failed to be detected (Table, 2).

Y. enterocolitica was recovered from Kareish cheese by Ebrahim (1998) and Halawa and Moawad (1999). While, El-Leboudy (1989) failed to detect the organism in Kareish cheese.

Y. enterocolitica has been implicated in cases of food poisoning involving milk and its products (Eley, 1996).

As presented in Table 4, there was a strong poistive correlation between the bacterial counts and moisture content of Kareish cheese, while negative correlation was found between the bacterial counts and acidity and sodium chloride percentages of Kareish cheese. Higher acidity, lower moisture content and higher salt content of food are important factors for cotrolling the growth of contaminating microorganisms and preserving the food. On the other hand, these factors may affect the texture and flavour of cheese (Nunez et al., 1985 and Forsythe and Hayes, 1998). The results of this investigation indicated that the Kareish cheese collected from local markets in Dakahlia Province was of poor sanitary quality and could pose a considerable risk to human health.

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