Twenty-five grams of each collected meat sample were blended with 225 mL of buffered peptone water (Merck, Germany). At that time, solutions were homogenized using Stomacher (Interscience, Saint-Nom, France). Then, 5 mL of the achieved solution was transferred into 50 mL Trypticase Soy Broth (TSB; Merck, Germany) supplemented with 10% NaCl and 1% sodium pyruvate, and incubated for 18 h at 35 °C. Then, a loopful of the culture was transferred into Baird-Parker agar supplemented with egg yolk tellurite emulsion (Merck, Germany) and incubated at 37 °C for about 24 h.5 (link),7 (link) Black shiny colonies surrounded by 2 to 5-mm clear zones were further identified on the basis of Gram staining, hemolytic activity on sheep blood agar (Merck, Germany), catalase activity, coagulated test (rabbit plasma), oxidase test, glucose O/F test, resistance to bacitracin (0.04 U), mannitol fermentation on Mannitol salt agar (Merck, Germany), urease activity, nitrate reduction, phosphatase, deoxyribonuclease (DNase; Merck, Germany) test, Voges–Proskauer (Merck, Germany) test, and carbohydrate (xylose, sucrose, trehalose and maltose, fructose, lactose, mannose) fermentation tests.8 ,13 (link)
Voges proskauer
Manufactured by Merck Group
Sourced in Germany
The Voges–Proskauer test is a biochemical test used to identify the presence of acetoin, a byproduct of glucose fermentation. It is commonly used in the identification of certain bacteria, such as members of the Enterobacteriaceae family.
Automatically generated - may contain errors
Lab products found in correlation
Egg yolk tellurite emulsion, by Merck Group (2 mentions)
Baird parker agar, by Merck Group (2 mentions)
Mannitol salt agar, by Merck Group (2 mentions)
Buffered peptone water (bpw), by Merck Group (2 mentions)
Sheep blood agar, by Merck Group (2 mentions)
Trypticase soy broth tsb, by Merck Group (2 mentions)
Brain heart infusion broth, by Thermo Fisher Scientific (1 mentions)
Mannitol salt agar, by Thermo Fisher Scientific (1 mentions)
Methyl red, by Merck Group (1 mentions)
Cetrimide agar, by Thermo Fisher Scientific (1 mentions)
Macconkey agar, by Merck Group (1 mentions)
Sulfide indole motility, by Merck Group (1 mentions)
Lysine iron agar, by Merck Group (1 mentions)
Xylose lysine deoxycholate agar xld, by Merck Group (1 mentions)
4 protocols using voges proskauer
1
Isolation and Identification of Staphylococcus aureus
2
Isolation and Identification of Gram-negative Bacteria from Milk
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For isolation of the Gram-negative bacterial strains, milk samples (0.01 mL) were spread aseptically on different selective and differential media i.e., Eosine Methylene blue agar (LAB, Heywood, UK) for Escherichia, MacConkey agar (LAB, Lancashire, UK) for coliform and Proteus spp, and Cetrimide agar (Oxoid, Basingstoke, UK) for Pseudomonas spp. They were further identified through biochemical tests including indole production (Oxoid, Basingstoke, UK), glucose metabolism with the methyl red (Merck, Darmstadt, Germany), acetone production using Voges proskauer (Merck, Darmstadt Germany), the simmon citrate utilization (BBL, Sparks, MD, USA), triple sugar iron (LAB, Heywood, UK), catalase, oxidase, urease and motility tests. Moreover, coagulase test, catalase test, indole production, methyl red test, Voges-proskauer reaction, urease production, citrate utilization were also utilized to identify Staphylococcus. In addition, for isolating of Staphylococcus, the loop full (0.01 mL) of the milk sample was spread on mannitol salt agar (MSA) (Oxoid, Basingstoke, UK) and incubated aerobically at 37°C for 24 h. The isolated bacteria were preserved in Brain Heart Infusion broth (Oxoid, Basingstoke, UK) with the addition of 30% glycerol at -70°C for further experiments.
3
Isolation and Identification of Staphylococcus
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As many as 20 g of each collected ready-to-eat food sample was blended with 225 mL of buffered peptone water (Merck, Germany). Next, the solutions were homogenized using a stomacher (Interscience, Saint-Nom, France). Consequently, 5 mL of the produced solution was transferred to 50 mL of Trypticase Soy Broth (TSB, Merck, Germany) supplemented with 10% NaCl and 1% sodium pyruvate, which was then incubated for 18 h at 35 °C. Next, a loopful culture was transferred to the Baird-Parker agar supplemented with an egg yolk tellurite emulsion (Merck, Germany) and incubated at 37 °C for about 24 h. Black shiny colonies surrounded with 2- to 5-mm clear zones were identified based on gram staining, hemolytic activity on the sheep blood agar (Merck, Germany), catalase test, coagulase test (rabbit plasma), oxidase test, OF glucose test, bacitracin sensitivity test (0.04 U), mannitol fermentation on the Mannitol salt agar (Merck, Germany), urease activity, nitrate reduction, phosphatase, deoxyribonuclease (DNase, Merck, Germany) test, Voges-Proskauer (VP) (Merck, Germany) test, and carbohydrate (xylose, sucrose, trehalose and maltose, fructose, lactose, and mannose) fermentation test [13 (link)].
4
Identification of Foodborne Pathogens
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In each plate, after pouring milk or cheese homogenisation, culture was performed on MacConkey agar, blood agar and chocolate agar and incubated for 24 h at 37°C. After 24 h, the colonies suspected of being S. aureus, S. typhi and L. monocytogenes were examined. Initially, single colonies were expanded, gram stained and catalase tested. Then, all slides were studied under a light microscope. In the final stage, tubular coagulase and DNase tests was performed for S. aureus isolates. Motility tests were performed at 37°C and room temperature for isolates suspected of being L. monocytogenes. For S. typhi, after culture on Mac Conkey agar (Merck) and xylose lysine deoxycholate agar (XLD) (Merck) the specific tests of Enterobacteriaceae family, including catalase test, oxidase test, methyl red (MR) (Merck), Voges–Proskauer (VP) (Merck),citrate utilisation (Merck), sulfide indole motility (SIM) (Merck), Kligler Iron Agar (KIA) (Sigma‐Aldrich) and Lysine iron agar (LIA) (Merck) were performed, the suspected isolates were subsequently evaluated with specific anti‐sera (Bharafshan, Iran).
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