each swab was then soaked in 10 ml of 0.1% (v/v) sterile peptone water and
vortexed for 1 min. For identification of E. coli, 1 ml of the respective
suspension was transferred to 3 M Petrifilm E. coli plates (3 M
Thailand Ltd., Bangkok, Thailand) and incubated at 35 C for 48 h
(Aarestrup et al., 2002), whilst for enterococci identification the
same amount of suspension was transferred to Slanetz Bartley agar
(Merck) and incubated at 37 C for 48 h.