TITLE:
Detection of Pathogenic Bacteria Staphylococcus aureus and Salmonella sp. from Raw Milk Samples of Different Cities of Pakistan
AUTHORS:
Syeda Asma Bano, Munazza Hayat, Tayyaba Samreen, Mohammad Asif, Ume Habiba, Bushra Uzair
KEYWORDS:
Raw Milk, Staphylococcus aureus, Salmonella sp., Mannitol Salt Agar, Xylose Lysine Deoxycholate
JOURNAL NAME:
Natural Science,
Vol.12 No.5,
May
22,
2020
ABSTRACT: Food-borne
diseases are the main public health problem throughout the world. Milk is important
component of human diet including fats, proteins, vitamins and minerals. It is
a best source of calcium and phosphorus. Different types of pathogenic bacteria
like S. aureus and Salmonella enter in milk and then multiply,
after multiplication they become active in causing diseases. These bacteria
create serious problems for human health. This study aimed to isolate and
identify pathogenic bacteria Staphylococcus
aureus and Salmonella from raw
milk samples of different cities of Pakistan. Primary screening of raw milk
samples was done on the basis of morphological, cultural and biochemical
techniques. The final identification was made using 16SrRNA sequence analysis.
A total of 200 raw milk samples were collected from different cities of
Pakistan. Selective medium xylose lysine deoxycholate agar (XLD) and Mannitol salt agar were used for the
identification of Salmonella sp. and S. aureus. Staphylococcus
aureus produced yellow colonies with yellow zones on Mannitol salt agar. Staphylococcus
aureus exhibited gram-positive character with purple coloration and
it was detected as cocci-shaped. Biochemically 91 (45%) samples enhibited Catalase,
Coagulase, DNase, Urease, Citrate, fermentation tests positive and indole,
oxidase and H2S tests negative with nonmotile character, indicating
the presence of Staphylococcus aureus. Salmonella sp. was detected as gram negative rods with pink
coloration on gram staining. Biochemically 87 (43%) samples revealed catalase,
citrate, H2S and fermentation tests positive while oxidase, DNase,
Indole and urease tests negative, indicating the presence of Salmonella sp. in these samples. Of the
200 samples tested, 43% were positive for Salmonella, while 45% samples
were contaminated with S. aureus. The 16SrRNA sequence analysis
confirmed the results of biochemical and cultural characterization by depicting
99% identity of samples with S. aureus and
98% identity with Salmonella spp. The
occurrence of high percentage of these pathogenic bacteria in raw milk may be
linked to its contamination at the time of collection, processing, strorage and distribution. This quantitative data could be
utilized to better establish the appropriate levels of protection for
raw milk, dairy products and processing technologies.