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Detection of Pathogenic Bacteria from Raw, Pasteurized and Uht Milk Available in the Local Market of Gazipur District

Nazia Afrin
Department of Botany, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh

S.M. Rokon-Ud-Doula
Department of Botany, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh

Rasheda Yasmin Shilpi
Department of Botany, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh

Abstract/ Executive Summary:

The present study was undertaken with the aim of investigating the bacteriological quality of locally available raw, pasteurized and UHT milk in Gazipur District. A total 5 raw, pasteurized and UHT milk samples were collected during November to December 2016. All the pasteurized and UHT milk samples showed the total aerobic heterotrophic bacterial (TAHB) level above the standard acceptable range (i.e. > 10⁴ cfu/ml for pasteurized milk and > 0 for UHT milk). Both Gram positive and Gram negative pathogenic bacteria viz. Staphylococcus aureus, S. epidermidis, Bacillus sp., Pseudomonas sp. and Enterobacter sp. were isolated from studied samples. API 20 E was used for confirmation of Pseudomonas sp. This study indicates that most of the pasteurized and UHT milk samples were not satisfactory in terms of public health standard. Therefore, care must be taken to avoid possible health risk in every step involving collection, transportation, storage and post pasteurization handing of raw milk.

Keywords: Bacteria, Raw milk, Pasteurized milk, UHT milk, Market, Bacillus, Pseudomonas

Location: local market of Gazipur City

Start Date:

End Date:

Program Area: Food Safety and Security

Commodity: Milk

Objectives:

To assess the microbiological quality and safety of locally produced raw milk, pasteurized milk and UHT milk available in local market.

Methodology:

Sample collection: Five raw and pasteurized milk samples were collected from different local market of Gazipur City and its surrounding area. Raw milk was collected in sterile bottle and immediately transported to the laboratory. The samples were preserved at 4ºC for detailed study. Isolation of bacteria: Bacterial enumeration and isolation was carried out by spread plate method in Nutrient Agar media (NA) (Eklund & Lankford, 1967) at adjusted pH 6. The microbiological condition of safety and hygiene were then assayed using the methods recommended by International Commission on Microbiological Specifications for Foods (ICMSF, 2005). Bacterial isolates were purified by repeated streaking as well as stored in NA slants at 4°C for further analysis. Microbial load determination: Microbial load was determined from the total number of discrete colonies counted after incubation. Isolated colonies were counted in colony formation unit as Number of cfu/volume plated dilution factor. Identification of the isolates: The selected bacterial colonies were observed to study various characters viz. color, form, elevation, margin, surface, optical characters etc. according to Eklund & Lankford (1967). Bacterial colonies were cultured on different selective and differential media such as: MSA, SSA, EMB, MacConkey, Bouillon agar, King’s B, XLD, Simon Citrate etc. Different biochemical tests (Casein test, Fermentation test, Indole test, Starch hydrolysis test, Catalase test) were also performed. Results of the morphological, cultural and biochemical tests of selected isolates were analyzed following Bergey's Manual of Systematic Bacteriology (Sneath et al., 1986) and Bergey’s Manual of Determinative Bacteriology (Buchanan et al., 1974). Coagulase test, endospore staining and API 20 E (Holmes et al., 1978) were used as a confirmation test of bacterial genus or species of Staphylococcus aureus, Bacillus sp. and Pseudomonas sp.

Source of Information: Jahangirnagar University J. Biol. Sci. 7(2): 13-19, 2018 (December)

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

So, from the present study, it can be concluded that the microbiological quality of most of the raw, pasteurized and UHT milk samples collected from different areas of Gazipur District were not satisfactory as some pathogenic bacteria such as Bacillus sp., Enterobacter sp., Pseudomonas sp., S. aureus and S. epidermidis were detected from the samples. The presence of S. aureus and Bacillus sp. will render milk unfit for human consumption, since sufficient number of these organisms may pose the risk of infection and intoxication. So, microbiological surveillance study could play an important role in the dairy industry to protect the public health and can reduce economic losses by the early detection of inadequate processing, packaging and or refrigeration.

Knowledge Management: Journal