Abstract
In this study, the effects of environmental factors (different media, temperature, pH, salt and sugar concentrations) on the planktonic growth, biofilm formation and formed biofilm of Escherichia coli KGPMF 16 and Escherichia coli KGPMF 17 were investigated. Tested bacteria were isolated from traditionally made cheese produced in Southeastern Serbia (Sokobanja region). The influence on planktonic growth, biofilm formation and formed biofilm was determined using spectrophotometric method. The limiting factors for the planktonic growth and biofilm formation were temperature of 4 °C and all tested concentrations of salt. The growth of tested bacteria was higher in media enriched with lactose than in media containing glucose. TSB was more congenial media to the planktonic growth of bacteria than MHB broth. None of the tested bacteria demonstrated the ability to form biofilm at 4 °C and 44 °C. Only E. coli KGPMF 17 showed ability to form biofilm in TSB at 37 °C. Different concentrations of salt, glucose and lactose exhibited inhibitory effect on biofilm formation, but all tested concentrations of lactose showed stimulating effect on formed biofilm of E. coli KGPMF 17. These results contribute to better understanding of the effects of environmental factors on the development of E. coli in cheese.
Highlights
Escherichia coli is one of the members of the microbiota of the intestinal flora
In Tryptic soy broth (TSB) at 37 °C, the growth of E. coli KGPMF 16 was reduced in all pH, except in pH 8.5, where growth was higher compared to the growth control
The growth of E. coli KGPMF 17 and E. coli ATCC 25922 was reduced in pH 5.5 and 6.5, while in other tested pH growth was similar as growth control
Summary
Escherichia coli is one of the members of the microbiota of the intestinal flora. With other bacteria, they contribute 0.1% to the total flora (ECKBURG et al, 2005). ISHII and SADOWSKY (2008) confirmed that resistant E. coli may survive very long outside the host Environmental factors, such as concentration of nutrients, osmotic pressure, temperature, etc., affect bacteria in their environment (BRENHORVD et al, 1992; BOUCHER et al, 1994). Bacteria are more frequently found in biofilms than in planktonic (free-living) forms (HALL-STOODLEY et al, 2004; HARRISON et al, 2007) These biofilms are generally described as microbial cells attached to a surface and encased in an extracellular polysaccharide matrix (COSTERTON et al, 1995). Several factors such as pH, temperature, concentration of O2 and glucose can affect biofilm formation (COSTA et al, 2014). According NESSE et al (2014) potentially human-pathogenic E. coli from the ovine reservoir can form biofilm on various surfaces and at several temperatures relevant for food
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