African Journal of Biomedical Research Ibadan Biomedical Communications Group ISSN: 1119-5096 Vol. 9, Num. 2, 2006, pp. 133-136

African Journal of Biomedical Research, Vol. 9, Vol. 2, May, 2006, pp. 133-136

Extent of Microbial Contamination of Sausages sold in two Nigerian cities

Oluwafemi F. and Simisaye, M.T.

Department of Microbiology ,University of Agriculture, P.M.B.2240,Abeokuta.

*Address for Correspondence (e-mail): foluwafemi2000@yahoo.co.uk 

Received: January, 2006
Accepted (Revised): April, 2006
Published May 2006

Code Number: md06023

ABSTRACT

Three shops were randomly selected in Abeokuta (South-West Nigeria) and Benin-City (South-South Nigeria) for the purchase of sausages which were then screened for microbial contamination. For the Abeokuta sausage samples the total aerobic counts ranged from 2.06-2.80 x 10⁶ cfu/g; Staphylococcus aureus count :1.1-  1.47 x 10⁶ cfu/g ; Enterobacteriaceae count: 1.57- 2.17 x 10⁶ cfu/g ; lactic acid bacteria count(LAB) count :1.70 – 2.33 x 10⁶ cfu/g. With respect to the sample from Benin-City, the total aerobic count ranged from 3.54 x 10⁶ cfu/g; S. aureus count: 1.8 x10⁵- 2 x 10⁷;  Enterobacteriaceae count: 5.09 x 10⁸ cfu/g; LAB count :1.3 -4.6 x 10⁸ cfu/g. Probable  organisms isolated from sausages sold in Abeokuta were  E. coli, Streptococcus sp., Clostridium sp., Klebsiella sp., Shigella sp., Pseudomonas sp., Lactobacillus sp., and S. aureus while those organisms isolated from sausages sold in Benin-City include Salmonella, Proteus, Shigella, S. aureus, Klebsiella and Lactobacillus sp. Most  of the sausages sampled were therefore considered to pose health risk to consumers, making it imperative to institute not only sanitary measures during processing, storage and marketing but also to ensure steady source of power supply.

Keywords: microbial contamination, sausages, Nigeria.

INTRODUCTION 

Food-borne illnesses in human beings due to bacterial pathogens and their toxins are well documented world-wide (Hazariwala et al, ( 2002); Lin et al ,(2002). Food-borne illness imposes a substantial economic and quality of life burden on society by way of acute morbidity and chronic sequela (Duff et al, 2003).Staphylococcal intoxication is a leading cause of food-borne intoxication and enterotoxigenic Staphylococcus strains have been isolated from foods implicated in illnesses (Adesiyun, 1995; Cencil et al, 2003). Salmonella spp has been reported by the United States Department of Agriculture Food Safety and Inspection Service (FSIS) as one of the most  common causes of food-borne illness associated with meat and poultry products .Yersinia enterocolitica is a salt-tolerant, pschrotrophic rod that is widely distributed in nature, in aquatic and animal reservoir for human pathogenic strains (Hillers et al, 2003). In 1998, there was an increased number of reported cases of illness due to Listeria monocytogenes which the Centers for Disease Control and Prevention as well as state and local health departments in the U.S. attributed to the consumption of cooked hot dogs and deli meats (FSIS, 1999). Shehu and Adesiyun (1990) reported 39.5% of milk to be positive for E. coli. Enterotoxigenic Escherichia coli has been involved in food-borne illness and recovered from various food types, processed or raw (Firstenberg and Sullivan, 1997).

Campylobacter jejuni and C. coli, often responsible for causing Campylobacter enteritis (campylobacteriosis) in humans ,the most common bacterial form of acute infective diarrhea, are the most commonly reported bacterial cause of food-borne infections in the United States (Skirrow and Blaser, 1995; Altekruse et al, 1999).A number of foods in Nigeria have been reported to have high incidence of bacteria (Adesiyun, 1995),however, there is little /scanty information  about the extent of microbial contamination of sausages sold in Nigerian supermarkets. The fact cannot be overemphasized that raw or pre-processed foods sold in supermarkets pose a direct health hazard to consumers if they contain an infective dose of pathogens or toxic levels of their toxins.

The purpose of this study was to evaluate the microbial contamination occurring on sausages at retail outlets in order to facilitate the assessment of microbiological risks associated with them. The microbial estimates determined were total viable counts, Staphylococcus aureus counts, Enterobacteriaceae, pychrophilles and lactic acid bacteria in respect to microbiological quality of the sausages.

MATERIALS AND METHODS 

Source and collection of samples: Three samples collected in Benin-City were from the University of Benin supermarket at Ugbowo, K-supermarket in Saponba and L-stores in Ring Road area. The Abeokuta samples (3) were from Ita –eko, Ibara and Onikolobo. The samples were put in sterile plastic containers and transferred to the laboratory ice-cooled within 2h of collection. The samples were collected from these sites randomly at the beginning, middle and at the end of each city

Bacteriology: Total and Differential Counts: One gram of each sausage sample was weighed into a mortar (that had been previously sterilized at 160°C for 1h) and ground with a sterile pestle until it became smooth and 9 ml of sterile distilled water was poured into the mortar. This was transferred to a test-tube followed by serial dilution up to 10^-7 dilution.

To determine total viable counts, 1 ml of each of 10^-5 and 10^-7 dilutions were plated on nutrient agar plates in triplicates. The plates were incubated at 37^o C for 24hours.The same procedure was repeated for Staphylococcus aureus count, enterobacteriaceae count, lactic acid bacterial count on mannitol salt agar,  MacConkey agar and De Man Rogosa Sharpe (MRS) agar respectively. Pschrophyllic count done for all samples in Benin-City. They  were incubated on nutrient agar plates at 4°C for 48 h. For MRS agar, the plates were incubated at 37°C for 48-72 hours. Anaerobic count was done by incubating plates in an anaerobic jar for 24 h.  

Identification of Isolates: The isolates obtained on plate counts were identified based on established conventional cultural, morphological and biochemical characterizations (Encinas et al., 1996)

Statistical Analysis: All data were analyzed using the general linear model procedures of SAS and Analysis of Variance (ANOVA).

RESULTS

Mean total viable count, Staphylococcus aureus counts, enterobacteriaceae count, psychrophillic count, LAB counts are shown in Table 1 for sausages from Abeokuta and Table 2 for microbial counts of sausages from Benin-City. The three centers sampled in Abeokuta had total viable counts that were between 2.06-2.87x 10 ⁶cfu/g (Table 1).This is an acceptable range for total viable count of organisms by the Public Health Laboratory Service (PHLS, 1996) but this was not the case for one location sampled in Benin-City. The sample from Ring Road area had total viable count of 4.8 x 10 ⁸cfu/g (Table 2) which was above the PHLS approved (10⁶-10 ⁷cfu/g).

Table1: Microbial  counts of sausage samples(cfu/g) from three locations in Abeokuta

Table  2. Microbial counts of sausage samples (cfu/g) from three stores in Benin-City.

The enterobacteriaceae counts for all samples obtained from Abeokuta and Benin-City were above the limit specified by the British Standard Institute (BSI,  1991,1993) except samples collected from Saponba area of Benin-City and it was observed also that this was the sample with the highest LAB count.Coliform counts from Abeokuta were in the range of 1.57 x 10⁶-2.17 x 10⁶ while those from Benin-City  were between  5.0 x 10⁴ -9.6 x 10⁸  Although the specific coliform organisms were not cultured in this work, it is not unlikely with the high counts that there will be some toxigenic strains of E. coli, Salmonella spp., Campylobacter and Klebsiella spp. The S. aureus count in all samples were within 10⁵-10⁶ cfu/g (Tables 1  and 2) except samples from one location (Ring Road area) that had 2.2 x 10⁷ cfu/g which was significantly different from all samples and the approved value by PHLS and BSI.

Lactic acid bacteria(LAB) counts were highest in two samples-one from Benin and the other from Abeokuta (Tables 1 &2).These values  were    significantly(P< 0.005) higher than all other samples. Organisms isolated also indicated the presence of Lactobacillus species.

Probable isolates of microorganisms from sausages in Abeokuta were E. coli , Staphylococcus aureus, Streptococcus sp., Clostridium sp., Klebsiella sp., Shigella sp., Pseudomonas sp, Lactobacillus sp. In Benin-City, Salmonella sp., Proteus sp., Shigella sp., Staphylococcus aureus, Klebsiella sp. ,Lactobacillus sp. were isolated. All these microorganisms have been implicated in food-borne illnesses (Firstenberg and Sullivan, 1997; Hazariwala, 2002).

DISCUSSION 

The mortality associated with these pathogens is not well documented in Nigeria however, the economic impact  of these illnesses is important (absenteeism, medical care, investigations, withdrawal of the contaminated products, loss of confidence in products).The high total viable counts from area such as the Ring Road area could be attributed to improper cleaning and sanitizing of equipment and poor employee hygiene within the store and more importantly due to erratic power supply in this area.

The enterobacteriaceae counts for all samples obtained from Abeokuta and Benin-City were above the limit specified by the British Standard Institute (BSI, 1993) except samples collected from Saponba area of Benin-City and it was observed also that this was the sample with the highest LAB count. The BSI specified that enterobbacteriaceae count greater than 10⁴cfu/g is considered unsatisfactory. Adesiyun (1994) demonstrated gross contamination with. S. aureus and E. coli of preprocessed bovine milk in Trinidad. Shehu and Adesiyun (1990) reported E.coli in fermented Nigerian milk. Although the specific coliform organisms were not cultured in this work,it is not unlikely with the high counts that there will be some toxigenic strains of E .coli, Salmonella spp., Campylobacter and Klebsiella spp. Food-borne salmonellosis  has been associated with consumption of various foods especially meat and poultry products (Adesiyun, 1993).The high enterobacteriaceae counts is an indication of potential microbial contamination during processing, distribution and storage. Their presence in large numbers  in food indicates inadequate processing/or recontamination due to cross contamination by raw materials ,dirty equipment or poor hygienic handling (Ikeme, 1990). Enterobacteriaceae occur as normal flora of the intestinal tract. They are widely distributed in nature and this account for their presence in sausage. However, E. coli and Enterobacter spp have the potential to  cause diarrhea (Volk, 1982).According to Zhao et al.,(2003).The process of freezing reduces the numbers of some coliforms such as Campylobacter jejuni.

.According to Kuku (1985),the presence of S.aureus could be as a result of it being a common organism on the skin, hands and boil and hence their presence in sausage may be as a result of contamination due to handling, processing, transportation and storage. Its presence in high numbers is a good indication of poor hygiene and temperature control. The presence of Staphylococci in high numbers in cured meat may indicate the presence of enterotoxin –producing strains of S  .aureus (AS/NZS, 1999), thus the data generated are of great importance to inform public health authorities, to detect food-borne diseases outbreaks early and to implement and evaluate food safety programmes.

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