Growth and adherence on stainless steel by Enterococcus faecium cells

Area of Science:

• Food Microbiology
• Dairy Science
• Bacterial Adhesion

Background:

• Enterococcus faecium is a bacterium found in raw milk.
• Contamination in dairy products is a significant concern for food safety.

Purpose of the Study:

• To investigate the growth characteristics of Enterococcus faecium at various temperatures.
• To determine the adherence capability of Enterococcus faecium to stainless steel surfaces.

Main Methods:

• Enterococcus faecium growth was assessed in reconstituted skim milk (RSM) and MRS broth at temperatures ranging from 6.5°C to 45°C.
• Bacterial enumeration was performed using spread-plating on MRS agar.
• Adherence to stainless steel chips was quantified using epifluorescence microscopy after acridine orange staining.

Main Results:

• Enterococcus faecium exhibited growth between 6.5°C and 42°C in MRS broth and 9°C to 40°C in reconstituted skim milk.
• The bacterium demonstrated rapid adherence to stainless steel surfaces, with initial attachment observed as early as 2 hours post-inoculation.
• Higher initial bacterial concentrations (10^6 CFU/ml) led to faster initial adherence compared to lower concentrations (10^3 CFU/ml).

Conclusions:

• Enterococcus faecium can grow at refrigeration temperatures, posing a risk in dairy products.
• The bacterium readily adheres to stainless steel, indicating potential for biofilm formation in processing equipment.
• Effective control strategies, including low-temperature storage and robust sanitation, are crucial for managing Enterococcus faecium in the dairy industry.