Microbiological Quality of Milk Powder Packed in Sudan and Their Antibiotic Susceptibility

Milk powder and cream powder are milk products which can be obtained by the partial removal water from milk or cream. One reason for drying milk is to preserve it. Milk powder has a longer shelf life than liquid milk and does not need to be refrigerated, due to its low moisture content. Another reason is to reduce its bulk for economy ease of transportation. Powdered milk and dairy products include such items as dry whole milk, non-fat (skimmed) dry milk, dry butter milk, dry whey products and dry dairy blends. Milk is a part of daily diet for adults (especially expectant and breast-feeding mothers) and growing children [1]. Milk is highly valued because it provides important source of many of the nutrients required for the proper development and maintenance of the human body [2]. Milk is highly nutritious and serves as an excellent growth medium for a wide range of microorganisms contaminating it. The microbial quality of milk and other dairy products influenced of the initial flora of raw milk, the processing addition, and post-thermal treatment concentration.


Introduction
Milk powder and cream powder are milk products which can be obtained by the partial removal water from milk or cream. One reason for drying milk is to preserve it. Milk powder has a longer shelf life than liquid milk and does not need to be refrigerated, due to its low moisture content. Another reason is to reduce its bulk for economy ease of transportation. Powdered milk and dairy products include such items as dry whole milk, non-fat (skimmed) dry milk, dry butter milk, dry whey products and dry dairy blends. Milk is a part of daily diet for adults (especially expectant and breast-feeding mothers) and growing children [1]. Milk is highly valued because it provides important source of many of the nutrients required for the proper development and maintenance of the human body [2]. Milk is highly nutritious and serves as an excellent growth medium for a wide range of microorganisms contaminating it. The microbial quality of milk and other dairy products influenced of the initial flora of raw milk, the processing addition, and post-thermal treatment concentration.
Microorganisms that can cause spoilage of dairy products include Gram-negative psychographs, coliforms, Lactic acid bacteria, yeasts, and moulds. Furthermore, various bacteria of public health concern such as Salmonella spp., Listeria Monocytogenes, Compylobacterjejuni, Yersinia enterocolitica, Pathogenic strains of Escherichia coli and enterotoxigenic strains of Staphylococcus aureus many also be found in Milk [2,3]. milk have been a major concern since the early days of the dairy industry, as many diseases are transmissiblevia milk products traditionally raw or unpasteurized milk has been giving more attention as a major for transmission of pathogens [1]. According to the standards [4][5][6][7]. Whole milk powder should contain more than 10 cfu/gm of coliforms and yeasts and moulds, <1cfu/gm of E. coli and 50,000 cfu/gm (maximum) of total bacterial count, and both salmonella and Staphylococcus aureus should be absent in 25gm of the product. The consumption of whole milk powder increased in the last few years due to shortage of fresh milk. This situation encouraged some investors import powdered milk in large size bags (25 kg) and repack into small size bags to be distributed in the retail markets. Most plants repack the milk in aluminum bags, while some milk powders are packed metal containers. The study was aimed at evaluating the microbiological quality of milk packed in Sudan and to assess the antibiotic susceptibility pattern of bacteria isolates.

Experimental Procedures Preparation of Milk Samples
A tenfold serial dilution up to 10-6 for each sample were prepared in 0.1% peptone water was obtained [8].

I Numeration of Total Viable Bacteria
Total plate count was used for enumeration of total viable bacteria. For the determination of TVC, 1 ml of each dilution was transferred using sterile pipette and spreader on plate count Agar sample. The Petri dish was then kept in a cubature at 37˚C for 24-48 hours. Following incubation, plates exhibiting 30-300 colonies were counted. The average number of colonies in a particular dilution was multiplied by the dilution factor to obtain the TVC. The TVC was expressed as several organisms of colony forming units per ml (CFU/ml) of samples according to [9].

I Numeration of Total Coliform Bacteria
It was performed by most probable number (NPN) Technique

I Numeration of Staphylococcus Aureus
Enriched samples were streaked on baited parked Agar (BPA) and the plate was incubated at 37˚C for 24-48hours [10].

Numeration Of Salmonella Spp:
The medium used for salmonella spp. Was Sabouraud Dextrose Agar (SDA). 1ml of each dilution milk sample was transferred using sterile pipette into two tubes of (1) Selenite Cysteine broth inoculated for 24hr at 35˚C.

Yeast and Moulds Counting Method:
The Medium for yeasts and moulds was Sabouraud Dextrose Agar (SDA). 1mlof each dilution milk samples were transferred using sterile pipette on (SDA), using a sterile petri dish for each sample. The dishes were than kept in an incubator at 27˚C for 3-5days [12]. All plates in all experiments mentioned above were in duplicate.

Characterization and Identification of Isolates:
Characterization and identification of the isolated bacteria were carried out based on either colonial, morphological or biochemical characteristics with reference to bergeys Manual of Systematic bacteriology [13].  [15,16]. Total coliforms, E.
coli, S. auers, Salmonella spp. and yeasts and molds were not found in all milk powders which have been tested (Table 1), thus, they were considered microbiologically safe. Milk powder is generally considered a product of good microbiological quality [17] it made from good quality milk and containing low microbial count and the moisture content is kept low [18].  and Staphylococcus aureus (7.7%). ( Table 2). Isolation of bacillus spp.is attributed to the presence of them in the environment. In addition, they are spore-forming bacteria, which made them to survive high temperatures of processing. Also, they are able to inhabit soils and vegetation and have been repeatedly isolated in several countries from wide variety of foods [19,20]. Most strains of bacillus are pathogenic for man, affect them incidentally. A notable exception is Bacillus anthracis, which caused anthrax in human and domestic animals and Bacillus thuringiensis, which caused disease in insects [21].

Conclusions and Recommendation
This study has revealed the presences of pathogenic/toxigenic bacteria in milk powder packed in Sudan, Also the study has explained that development of multiple antibiotics resistance is the major public health threat to consumers, especially in children.
And they administered on them during illness. Infections many be prolonged a may even lead to increase in mortality therefore, we recommended the following: a. Improvement of personal hygiene of sellers. b.
To use small package of milk powder to reduce the duration of exposure and hence decrease chance of contamination.