an investigation of domestic laundry in europe - habits ... - SIFO

80An investigation into the domestic laundry habits in EuropeBacillus cereus colonies are pink and surrounded by a zone of precipitation.Suspected colonies are plated on MYP/PREP and again incubated for one dayat 30°C. The result is considered positive if the colonies are pink and surroundedby a zone of precipitation. It is also possible to see Enterococcus faecalison these plates. These colonies are yellow, glossy and sized 0.5mm.Enumeration of the Total Plate Count1 ml of the serial dilution is transferred to a plate and mixed with ca 15mlPCA (Plate-Count-Agar, Merck, 5463). The plates are incubated for threedays at 30°C. Every visible colony on this plate is counted.Enumeration of yeast and fungi0.1ml of the serial dilution is spread on an OGGA-plate (BiotradingK1042090) and incubated for 5-7 days at 25°C. During this period the platesare checked on the third day and the yeasts are counted. This is done in orderto see the yeasts before they are overgrown by fungi.4.3.8 CalculationThe number of micro-organisms is calculated according to normal microbiologicalrules.NNΣan 1n 2d∑ a=( n + 0, n ) d112= number of colonies= sum of the number of counted colonies= number of plates in first dilution= number of plates in second dilution (less diluted)= dilution rate corresponding first dilutionPlates with one or two colonies are considered negative, as these findingsmight be due to cross-contamination during the test. A negative result is writtenas