MATERIALS AND METHODS

Location of study: The study was conducted in Tamale Metropolis. Tamale is the capital town of the Northern Region of Ghana. It is located within the Guinea Savannah belt. Tamale is the third most populous settlement in Ghana, in terms of population, with a population of 537.986 people. Tamale metropolis can be located on longitude 09°24'27" North and latitude 00°51'12" West. The Tamale Metropolis occupies approximately 750 km², which is 13% of the total area of the Northern Region.

Sample collection: The surfaces of 70 beef carcasses from seven different locations in Tamale Metropolis, where meat is popularly sold were swabbed using sterile cotton swabs. A surface area of about 10 cm² was swabbed for each sample and ten beef swab samples were collected from each location. The swabs were stored in an ice chest containing ice blocks and transported to the laboratory where analysis was carried out immediately upon arrival for the presence of Escherichia coli and Salmonella spp. Sampling was done from May 2014 to September 2014. General observation on the conditions under which meat is sold in the Tamale Metropolis was also made during data collection.

Bacteriological analysis: Analysis for Escherichia coli and Salmonella spp. were done using a modified method according to the Food and Drug Administration-Bacteriological Analytical Manual (FDA-BAM) (Wallace and Hammack, 2007; Feng and Weagant, 2009). Briefly a swab was pre-enriched in 10 mL buffered peptone water and incubated at 37°C for 24±2 h. For Escherichia coli, a loopful of the aliquots (ca. 10 μL) from the buffered peptone water was streaked onto Levine’s Eosin-Methylene Blue (LEMB) agar and incubated at 37°C for 24±2 h. Presumptive Escherichia coli colonies appear as dark centered and flat, with or without metallic sheen. One to three colonies showing such characteristic nature were picked from each plate and purified on nutrient agar. They were identified and/or confirmed using Gram staining, Escherichia coli latex agglutination test and biochemical tests. For Salmonella spp., 0.1 and 1 mL of pre-enriched aliquots (buffered peptone water) were transferred into 10 mL rappaport and vassiliadis broth and 10 mL selenite cystine broth, respectively for enrichment. Enrichment samples in rappaport and vassiliadis broth were incubated at 42°C for 24 h while, those of the selenite cystine broth were incubated at 37°C for 24 h. Enriched aliquots (ca. 10 μL) were then streaked onto xylose lysine deoxycholate and brilliant green bile agar and incubated at 37°C for 24-48 h. Presumptive Salmonella spp. were purified on MacConkey and nutrient agar and were identified and/or confirmed using Gram staining, Salmonella latex agglutination test and biochemical tests. All incubations were done under aerobic condition and all media used were purchased from Oxoid, UK.

RESULTS

The results for the prevalence of Escherichia coli and Salmonella spp. in beef samples examined in the Tamale Metropolis is presented in Table 1. The overall prevalence of Escherichia coli and Salmonella spp. was 56% (39/70) and 31% (22/70), respectively. The highest prevalence occurred in Location G 100% (10/10) for Escherichia coli and Location F 90% (9/10) for Salmonella spp. Higher percentage of beef samples obtained from Locations C (80%), D (60%) and F (60%) were contaminated by Escherichia coli. Fifty percent of beef samples obtained from Location G were contaminated by Salmonella spp. Escherichia coli was not isolated from Location A. The least occurrence of Salmonella spp. were Locations A, B and G which recorded 10% (1/10) for each of the locations.

DISCUSSION

The study provides useful information to consumers and all stake holders about the presence of Escherichia coli and Salmonella spp. in beef samples sold in the Tamale Metropolis and the risk of contracting Escherichia coli and Salmonella spp. infections from the consumption of beef in the Metropolis. Of the 70 beef samples tested, 39 (56%) were positive for Escherichia coli. The prevalence of Escherichia coli was highest in Location G 100% (10/10). The prevalence of Escherichia coli in the other locations were Location C 80% (8/10), Locations D and F 60% (6/10), Location B 50% (5/10) and Location E 40% (4/10). Escherichia coli was not isolated from Location A 0% (0/10). This result suggests that beef samples in the Tamale Metropolis are contaminated with Escherichia coli. Unhygienic conditions and practices such as butchers (meat sellers or processors) wearing dirty clothes and/or aprons, dirty surfaces of chopping tables, using the same knife in cutting beef carcasses without sterilization, mixing different meat types on the same chopping table, busily conversing while cutting and selling meat, houseflies hovering around meat and selling meat in untidy environments were observed.

Table 1:	Prevalence of Escherichia coli and Salmonella spp. in beef samples in tamale metropolis

It was noticed that locations with high prevalence of Escherichia coli and Salmonella spp. compromised with most of the afore-mentioned unhygienic and conditions and practices. It is widely recognized that the presence of Escherichia coli in any food or water sample is an indication that, that food or water sample has been contaminated by faeces (WHO, 2005; Feng and Weagant, 2009; Nataro and Kaper, 1998; Burgess et al., 2005). The absence of Escherichia coli in Location A could be due to the relatively better hygienic conditions under which butchers in that location sold their meat. Some of the butchers in Location A had their tables covered with nets, wear neater clothings/aprons and sold meat under a much tidy environment. Even though no Escherichia coli was isolated in this location, it is possible this pathogen can be isolated at a different time if their hygienic standard falls or is lowered. The presence of Escherichia coli in the beef samples examined is worrying because certain strains of Escherichia coli such as strain Escherichia coli O157: H7 can cause food poisoning. Besides that, Escherichia coli can cause urinary infection, fever, vomiting, diarrhea, severe abdominal pain, hemorrhagic colitis, haemolytic-uremic syndrome and even death (Teophilo et al., 2002; Smith et al., 2003).

With regards to Salmonella spp., averagely 31% (22/70) of the beef samples were positive. The highest was found in Location F 90% (9/10). The prevalence of Salmonella spp. in other locations were Location D 50% (5/10), Location E 30% (3/10) and Location C 20% (2/10). Location A, B and G recorded a prevalence of 10% (1/10). Similarly to the results obtained for Escherichia coli in this study, beef samples in Tamale metropolis are contaminated by Salmonella spp.. The occurrence of Salmonella spp. in the various locations suggest the conditions under which beef is handled in the Tamale metropolis. Locations with high prevalence of Salmonella spp. have lower hygienic standards compared to locations with low prevalence. The isolation of Salmonella spp. in the beef samples examined is also of public health concern. This is due to the fact that Salmonella spp. cause Salmonellosis. Typical symptoms of illness associated with Salmonellosis include nausea, vomiting and diarrhea; additional complications associated with infection include septicemia, or reactive arthritis (Adams and Moss, 2008; Feng and Weagant, 2009). The pathogen Salmonella is also known to be a causative agent of gastroenteritis (Mead et al., 1999). Among all foodborne pathogens, Salmonella spp. is recognized to play a significant role in foodborne illnesses, hospitalizations and death of humans (Scallan et al., 2011).

In general, the beef samples were contaminated more by Escherichia coli (56%) than Salmonella spp. (31%). With the exception of Location A and Location F where beef samples had higher prevalence in Salmonella spp. than Escherichia coli, the rests of the Locations were dominated by Escherichia coli. In addition all the locations had beef samples being contaminated by both Escherichia coli and Salmonella spp. save Location A. Zhao et al. (2001) studied the prevalence of Escherichia coli in a variety of meat samples. They reported a prevalence of 39, 19 and 16% for chicken, beef and pork samples, respectively. In this study, a higher prevalence of 56% was observed in the beef sample. Li et al. (2004) reported the prevalence of Escherichia coli in Bison carcasses post-evisceration, post-washing and chilling to be 73.28, 56.89 and 11.3%, respectively. For Salmonella spp. it was 2.59% post-evisceration, 3.45% post-washing and 2.93% chilling (Li et al., 2004). Prevalence of Escherichia coli post-washing is similar to findings of this study. The prevalence of Salmonella spp. was higher in this present work than that of Li et al. (2004).

CONCLUSION

Beef samples in the Tamale metropolis were found to be contaminated by Escherichia coli and Salmonella spp. More beef samples were contaminated by Escherichia coli than Salmonella spp. The occurrence of both Escherichia coli and Salmonella spp. differ in different locations, which is mainly due to the level of hygienic standards observed by the meat processors/sellers. Meat consumers and the public are exposed to food poisoning by consuming beef that is cooked improperly. Therefore, it is recommended that meat consumers in Tamale should cook (70°C for 15 min) their meat well before consuming it. Further research should investigate the antibiotic resistance and pathogenicity of Escherichia coli and Salmonella spp. in beef.