dairyplant. Additional contamination of milkby theB. cereusbiofilmwas
shownto occurin the filling machine.DifferentBacillusspp.,and amongthem
B. cereus, havebeenfoundon liquidpackagingboardsand blanksand these
could thus be an additional source of biofilms containing Bacillus spp.
(Svenssonet al., 2004).Furthermore, spores ofB. cereusare reported to possess
a pronounced abilityto adhere to the surface of stainlesssteel, which is
commonly usedin foodprocessing. BothB. cereusandB. subtilisbiofilms were
detected on stainlesssteeland Teflonsurfaces, and removalfromstainlesssteel
was moredifficult thanfromTeflonbecause of surfaceroughness (Wirtanenet
al., 1996).Te Giffel and co-workers(1997)showedthat spores ofB. cereus
adhered,germinated and multiplied on the stainlesssteelsurfaces of a tubeheat
exchanger.The cellsofB. cereuswereisolated fromthe individualtubesafter
cleaning. The attachment ofB. cereusin processlinesmayact as a continual
source of post-pasteurisation contamination (Elvers et al., 1999). Lindsay
(2001)found thatthe biofilmsof foodspoilageBacillusandPseudomonas
speciesattach themselvesto liquidfoodprocessingequipment surfacesand
cellsin biofilms,evenif treated withan in-useconcentrationof sanitisers,
manageto surviveand grow.This phenomenonis evenstrongerwhenmixed
biofilms are involved. The attachedB. cereuscellsmaysubsequentlyforma
biofilmon a stainlesssteel surfaceand present a majorproblemfor the food
industry (Penget al., 2002).
3.2.7 Clostridiumperfringensbiofilms
Clostridiumperfringens is a spore-forming, Gram-positive,anaerobic, non-
motilerod whichformslarge,regular, roundand slightly opaqueand shiny
colonies on the surfaceof agar(Brynestad & Granum,2002).Thereare five
typesofC. perfringens: A, B, C, D and E, whichproducedifferenttypes of
toxins(Labbe¬, 2003).C. perfringenscan growbetween10 ÎC and 52 ÎC, witha
maximum of 45 ÎC for most strains(Brynestad & Granum,2002).It is oftena
cause of human food poisoning due to its ability to grow over a wide
temperature range. Its spores can also survive several food processing
procedures. Sporesof some strains are resistantto temperaturesof 100 ÎC for
morethan1 h (Labbe¬, 2003).
Clostridiumperfringensfoodpoisoning fromnew foodsources,because the
bacteriumis so adaptable and prolific, has helpedto showhowour perceptions
and understandingof safe foodchangewith newknowledge (Foster, 1997).C.
perfringenscan be foundas part of the normalflora of the intestinal tractsof
bothanimals and humans, as well as in soil, clothingand skin.It has beenfound
in virtuallyall environments tested, including water,milkand dust (Brynestad &
Granum, 2002).In viewof its widespread presencein moist soil, its presencein
air and dust in kitchens, cateringand foodprocessing environmentsis not
surprising (Labbe¬, 2003).C. perfringensserotypescommonlyassociatedwith
humanillness havebeenfoundon recentlyslaughteredcarcasses. Otherfoods
contaminated with C. perfringens are poultry, fish, vegetables and dairy
Biofilmrisks 55