CHAPTER ONE

INTRODUCTION

1.1     Background of Study

Food safety and quality is a global topic of public concern. Salmonella is a Gram negative bacteria, rod shaped, aerobic or facultative anaerobic, belonging to the Family Enterobacteriaceae and it is a major pathogenic bacterium,'inhabiting the intestinal tract of humans and animals (Holt et al.,1994). Salmonella spp are important causes of bacterial contamination of the environment and the food chain (Ponce et al., 2008), and are the leading causes of acute gastroenteritis in several countries.In developing countries, contaminated vegetables, water and human-to-human transmission are believed to contribute to comparatively larger proportion of human cases than those in industrialized countries (Acha and Szyfres, 2003; Soltan et al., 2009). Salmonellosis due to Salmonella spp is the most common food-borne disease in both developing and developed countries, although incidence rates vary according to human and animals (Gerosa and Skoet, 2013).

According to the Centers for Disease Control and Prevention (CDC, 2011); the genus Salmonella contains two species, Salmonella enterica and Salmonella bongori. S. enterica consists of six subspecies (Popoff and Le Minor, 2001) namely; S. enterica subsp enterica, S. enterica subsp salamae, S. enterica subsp arizonae, S. enterica subsp diarizonae, S. enterica subsp houtenae, S. enterica subsp indica. A relatively small number of these serotypes have been documented to be host specific, characteristically producing systemic disease in a restricted number of animal species. These serotypes include: S. Gallinarium and S. Pullorumin chickens; S. Dublinin cattle; S. Cholera-suisprimarily in pigs (Zhang-Barber et al., 1999).

Milk is often described as fresh, clean and normal mammary secretion obtained by milking of one or more dairy animals that are properly fed and kept or also defined as the fluid secreted by mammals for the nourishment of their young (Rani and Mahesh, 2012). In dairy animals, cow milk is the most consumed milk world-wide and in 2011, Food and Agricultural Organisation (FAO) estimated 85% of all milk world-wide was produced from cows (Gerosa and Skoet, 2013). The cow milk is a good source of animal proteins, fats, vitamins and minerals to the human body (Rani and Mahesh, 2012). Nutritionally less useful substances like enzymes are also present in normal cow milk, and some of these enzymes are used as indices in screening or quality control tests for fresh milk (Anonymous,2012). The principal components of milk are water, fats, proteins and lactose. High water activity, moderate pH (6.4-6.6) and ample nutrients make milk an excellent culture medium for microbial growth at suitable temperature (Adams and Moss, 2008).

Pathogenic bacteria in raw milk have been a major public health concern. The main sources of contamination are the dairy cattle; food handlers and dairy equipment (Muehlhoff etal., 2013). Consumption of raw milk is considered to be the main cause of several outbreaks ofSalmonella spp.,Listeria monocytogenes and Escherichia coli O157:H7 (Grant et al., 1995). Raw milk products have posed the greatest human health problems in various countries (Lejeune andRajala-Schultz, 2009). However, raw cow milk forms the basis for most commonly sold local milk products in Nigeria which include locally fermented skimmed milk known as “Nono”, locally fermented full creamed milk “Kindirmo”, local milk butter “main Shanu”or „„ghee‟‟, and cheese “Wara”(Waters-Bayer, 1994).

Nono is the Fulani word for fermented cow‟s milk sold predominantly by Fulani women. It is mostly available in the northern part of Nigeria (Yahuza, 2001). Nono is rich in protein, notably essential amino acids; phosphorous and vitamins (Nebedun and Obiakor, 2007). Lactic acid bacteria are mostly associated with the production of fermented milk products and play a key role in producing nice flavour, aroma and good physical appearance in fermented milk products (Widyastuti et al., 2014). Although, lactic acid is the principal product of the fermentation lesser amount of flavouring substance diacetyl is also produced (Reyee et al., 2003; Tannock, 2004).

1.2     Statement of Problem

Salmonellae are zoonotic enterobacteria that are responsible for outbreaks of both human and animal diseases called salmonellosis and have important health significance worldwide, with several transmission routes of which majority of human infections are being derived from the consumption of contaminated foods (Yuk and Schneider, 2006) such as insufficiently cooked meat or improperly pasteurized milk and milk products (Jackson et al., 2007). Salmonellosis is of significant public health concern, because humans and animals can become infected from consumption of food/feed and drinking water contaminated with Salmonella spp. from faeces of infected animals and raw milk products which have not been adequately pasteurized (Jackson et al., 2007).

Salmonella have been associated with documented food-borne illness episodes in the past 20 to 30 years and their numbers appear to be increasing (Fratamico et al., 2005). Generally, the morbidity and mortality of attendant cases of food borne diseases are on the increase (Mead et al., 1999).

Salmonellosis is a bacterial disease with a rising prevalence in the cattle industry. It is most common in dairy calves one to ten weeks of age, but can also be seen in adult dairy cows and beef cattle (Randall, 2001).

Salmonellosis has a serious economic impact on the cattle industry causing livestock mortality, abortions, reduced milk production, and reduced consumer confidence (Jackson et al., 2007). These result in extra labour and increased veterinary expenses (Santos et al., 2003; Nielsen et al., 2004). Determination of food-borne disease estimates require continued and improved active surveillance (Mead et al., 1999), because despite many advances in food technology, it is still difficult to ensure food safety from stable to table (Duffy and Schaffner, 2002) with animals serving as reservoirs of many food borne bacterial pathogens (Cooke, 1990).

Acquired antibiotic resistance is a growing worldwide problem due to abusive use of antibiotics in humans, animals and agriculture.

Food contamination with antibiotic resistant bacteria can be a major threat to public health, as the antibiotic resistant determinant can be transferred to other bacteria of human significance. This is in view of the fact that the prevalence of antibiotic resistance among food borne pathogens has increased during past decades (Holt et al., 1994; Van et al., 2007).

In Nigeria, studies have been reported from Plateau State on raw milk and locally-fermented milk with a prevalence of 0.8% and 6.4% of Salmonellaspp respectively (Karshima et al. 2013) and Olatunji et al. (2012), also reported a prevalence of 17.06 % Salmonellaspp in raw milk sold in Gwagwalada, F.C.T., Abuja.

The global problem of antimicrobial resistance is particularly pressing in developing countries with reservoirs of resistance present in healthy human and animal populations and also the increasing resistance to flouroquinolones bySalmonella spp as reported in Lagos, (Akinyemi et al. 2007), which is of public health concern.

1.3     Aim and Objectives

The aim of this study was to analyse the advance effect of fermented milk sale by Fulani women isolate and identify Salmonella species from raw milk and locally- fermented milk “Nono” in Zaria, Nigeria. The specific objectives of the study are to:

1.       Determine the total aerobic plate count in raw and fermented milk samples from Zaria

2.       Isolate and characterize Salmonella spp from raw milk and locally-fermented milk “Nono” in Zaria, Nigeria.

3.       Determine the occurrence of Salmonella sppin raw milk and locally-fermented milk “Nono” in Zaria, Nigeria.

4.       Determine the antimicrobial resistance patterns of Salmonella isolates from raw milk and nono in Zaria, Nigeria to commonly used antibiotics.

1.4     Research Questions

i.        What is the estimated bacterial load of raw and fermented milk samples in Zaria?

ii.       Is Salmonella spp present in raw milk and locally fermented milk “Nono” in Zaria?

iii.      Are Salmonella isolates resistant to commonly used antibiotics?

iv.      What are the antimicrobial resistance patterns of Salmonella isolates from raw milk and nono in Zaria, Nigeria?

1.5     Significance of Study

Salmonella species are excreted through animal’s faeces into the environment and can contaminate milk during milking. Also, the hands of the milkers who are suffering from salmonellosis could also be a source of contamination to the milk due to unhygienic practices. Therefore, milk and milk products derived from animals can be important vehicles of human salmonellosis (Wong et al., 2009; D'Aoust, 1998). Studies in Plateau State on contamination of raw milk and locally-fermented milk have reported prevalence of 0.8% and 6.4% of Salmonella spp respectively (Karshima et al. 2013) with Olatunji et al. (2012), also reporting a prevalence of 17.06 % Salmonella spp in raw milk in Gwagwalada, the Federal Capital Territory-Abuja. However, there is paucity of information on Salmonella spp. and their antibiogram associatedwith milk sold in Zaria.

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