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Isolation and Identification of Pathogenic Escherichia Coli, Klebsiella Spp. and Staphylococcus Spp. in Raw Milk Samples Collected from Different Areas of Dhaka City, Bangladesh

Md. Aftab Uddin
Department of Microbiology, Stamford University Bangladesh

Hasan Md. Motazzim-ul-Haque
Department of Microbiology, Stamford University Bangladesh

Rashed Noor ‡
Department of Microbiology, Stamford University Bangladesh

Abstract/ Executive Summary:

The present study was undertaken with the aim of investigating the bacteriological quality of locally available raw milk. A total number of 22 raw milk samples were collected from Dhaka city and its surrounding areas during the period from October 2009 to November 2009. The analysis comprised enumeration of total viable bacterial count (TVBC), total coliform count (TCC) and total staphylococcal count (TSC) for the determination of sanitary quality. The highest TVBC, TCC and TSC were 2.36 x109 cfu/ml, 2.0 x 108 cfu/ml & 4.7 x 107 cfu/ml, respectively. In order to observe the antibiotic-resistance pattern, the antibiogram assay was carried out. All Escherichia coli isolated from raw milk exhibited 100% resistance against Rifampin (R) and Tetracycline (TE) and 50% resistance against Nalidixic Acid (NA) but were 100% sensitive against Imipenem (IPM). Klebsiella spp. exhibited 100% sensitivity against Imipenem (IPM). Staphylococcus spp. isolated from raw milk exhibited 100% resistance against Rifampin (R) and Nalidixic Acid (NA), but were 100% sensitive to Gentamicin (CN) and Imipenem (IPM). This survey indicates that most of the raw milk samples were not satisfactory in course of public health standard as some pathogenic bacteria were detected from these samples. Frequent use of antibiotics should be prohibited since antibiotic resistant strains are continuously increasing.

Keywords: Escherichia Coli; Milk

Location: Dhaka city and its surrounding areas

Start Date: 00-10-2009

End Date: 00-11-2009

Program Area: Quality and Nutrition

Commodity: Milk

Objectives:

This study investigates the microbiological quality and safety of locally produced raw milk.

Methodology:

Sample Collection: Twenty two raw milk samples were collected for microbial analysis from Dhaka city and its surrounding areas. The sampling period was from October 2009 to November 2009. Milk samples were collected in sterile container (bottles). About 100 ml of fresh raw milk were collected in a sample container using a sample collector ice box at 4°C and were transported to the laboratory without delay. Isolation of microorganisms from raw milk samples. Serial dilutions of samples were made up to 10-7 in sterile normal saline. Enumeration of Microorganism: The bacterial count was performed by standard method (13). The microbiological condition of safety and hygiene were then assayed using the methods recommended by International Commission on Microbiological Specifications for Foods (ICMSF). Total Viable Bacterial Count. The total viable bacterial count was carried out by the spread plate technique. The sample (0.1ml) of each dilution was taken onto each sterile Petridish and evenly spread on the solid nutrient medium and incubated at 37°C for 24 hours. The plates were screened for the presence of discrete colonies after incubation period and the actual numbers of bacteria were estimated as colony forming unit in per ml (cfu/ml). Then the results per dilution were recorded. Quantitative analysis for the presence or absence of specific microorganisms was done by plating on selective media. Total coliform count (TCC) and total staphylococcal count (TSC) were done in the same way using MacConkey agar medium and Mannitol Salt Agar medium, respectively. All the viable counts were the average of at least three independent experiments. Bacterial isolates were then identified according to the Bergey’s manual of determinative bacteriology (14), and manual for the identification of medical bacteria (15). Antibiogram: Kirby-Bauer method (16) was used to examine bacterial susceptibility to antimicrobial agents. Shortly, after 16-18 h of incubation muller hinton agar plates (containing pure culture and antibiotic discs) were examined and the diameters of the zones of complete inhibition were measured in millimeter scale. The zone diameter for individual antimicrobial agents was then translated into susceptible, intermediate and resistant categories according to the interpretation table of the Becton Dickinson Microbiology Company, USA.

Source of Information: Stamford Journal of Microbiology, Vol.1(1), July 2011, p.19-23

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

From the present study, it can be concluded that the microbiological quality of most of the raw milk samples collected from different areas of Dhaka city were not satisfactory as some pathogenic bacteria such as E. coli, Klebsiella spp. and Staphylococcus spp were detected from the samples. The presence of S. aureus and Klebsiella spp. will render milk unfit for human consumption, since sufficient number of these organisms will cause infection and intoxication. Multiplication and production of S. aureus would however, depend upon environmental factor like time, temperature, relative humidity and duration of storage and food factors, potential water activity (aw), moisture contents, nutrients present, additives used and associated microflora like S. aureus and coliforms and fecal coliforms (23). Raw milk should be pasteurized, so that milk remains free from pathogenic microbes. Proper refrigeration temperature should be maintained. Frequent use of antibiotics should be stopped as antibiotic resistant strains are continuously increasing.

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