decreaseof humanlisteriosis casesin someEuropeancountries at the end of the
1990sis a consequenceof improved foodmanufacturinghygiene.
33.6 Futuretrends
Molecular typingmethodshaveproven theirusefulnessin the improvementof
foodindustry hygieneand the use of thesemethodswill also be importantin the
future.Newmolecular typing methodswillprobably be developedand the
currentculture-independenttechniques improved.Microarraytechnology and
sequence-based typingmethodologywill bringverysensitiveand unambiguous
typingdataintoreach. Theinterpretation of the data and practicaluse in
contaminationanalyseswill be challenging.
Molecular typingmethodshaveincreased our knowledge of the epidemio-
logyof individualmicroorganisms,but a more complete understandingof the
microbial ecology in the foodprocessingplantsshouldbe acquired.The survival
and multiplication of pathogensand spoilageorganisms in foodprocessing
environments are influencedby several different factors,e.g. other micro-
organisms.Interactionsbetween microorganismsand their influence on the
survivalof pathogensare still quiteunknown.The study of microbial ecology
will provideus withinformation that should give us again`a new set of tools'in
the eliminationand preventionof pathogensand spoilageorganismsin food
processing environments.
33.7 Sources of furtherinformationand advice
Numerous contaminationanalyses studies, whichwill providemoreinformation,
havebeenperformedsince 1995 on differentmicroorganismsin differentfood
industry areas.There are alsoseveral studies pointingout weaknesses and
strengths of molecular typingmethods.
33.8 References
AARNISALOK AUTIOT SJO»BERGA-MLUNDE¬N J KORKEALAHandSUIHKOM-L(2003),Typing ofListeriamonocytogenesisolatesoriginatingfromthe foodprocessingindustry withautomatedribotypingand pulsed-fieldgel electrophoresis',J FoodProt, 66 , 249±255. AASEB SUNDHEIMG LANGSRUDSandRÈRVIK L(2000),Occurrenceof and possible
mechanismfor resistance to a quaternary ammoniumcompoundin Listeria
monocytogenes',Int J FoodMicrobiol, 62 , 57±63.
ALLENJ RandFOSTER E M(1960),Spoilageof vacuum-packedslicedprocessedmeats duringrefrigeratedstorage',FoodRes, 25 , 19±25. AUTIOT HIELMS MIETTINEN M SJO»BERGA-MAARNISALOK BJO»RKROTHJ MATTILA-SANDHOLM TandKORKEALAH(1999),SourcesofListeriamonocytogenescontaminationin a
cold-smoked rainbow trout processing plant detected by pulsed-field gel
Contaminationroutes and analysis in foodprocessing environments 551