cereus,B. thuringiensis,B. anthracisandB. mycoides,sharea highdegree of
chromosomalsequence similarity,and all of them havebeenshown to be
potentiallytoxigenicand causefoodborne illnessoutbreaks and opportunistic
infections(Jacksonet al., 1995;Damgaardet al., 1996;Beattie and Williams,
1999;Hsiehet al., 1999;Hansen and Hendriksen, 2001).
Microbialnumbers in food-grade paperand boardhaveusually beenbelow
the limitset by the FDA. The spectrum of microorganismsisolated fromfood-
packagingboardsand blankshas alsobeenreportedto be relatively narrow
(Va»isa»nenet al., 1991; Kneifel and Kaser, 1994;Pirttija»rvi et al., 1996).
Pirttija»rviet al.(1996)studied liquidpackagingboardsand characterisedover
200 isolates.Contaminants foundwereaerobic spore-formingbacteria,of which
B. cereusgroupwas oftenpresent. Approximately50% of theB. cereusgroup
strains were positive in enterotoxin tests.Later it was concluded thatthe
numbers ofB. cereuswerelow in paperand boardand onlyone of ninestrains
(11%) isolatedwas producingenterotoxin (Suihkoet al., 2004).
The anaerobicClostridiumspeciesare a veryheterogenicand scarcelystudied
groupof potentialend-product contaminants. Mostclostridia producegasesas
fermentation productssuchas butyric, acetic, propionic and valeric acids,and as
a consequence can causeoffensiveodourproblemsin end-products. Thisspore-
forming anaerobic groupof bacteriahavealso severalpathogenicspecies. C.
sporogenes is quite common in papermaking systems. This spore-forming
bacteriumcan be foundin soil,water,broke,additives,recycledfibreand
recycled sludge (Robichaud,1991).AnotherClostridiumspecies,C. perfringens,
can causefoodpoisoning.C.perfringensis ubiquitousin nature. AnaerobicC.
perfringensproduces spores that are highlyresistantto environmentalstresses
suchas radiation, desiccationand heat (McClane,1997).It can be isolated, e.g.
fromsoil and dust or fromintestinal tracts of humans and domestic animals.C.
perfringenscauses two different types of humandiseasethat can be transmitted
by food,i.e.C. perfringenstypeA foodpoisoningand necrotic enteritis.C.
perfringenstypeA foodpoisoning is most commonin industrialisedsocieties.
The genetic diversity of anaerobic bacteria present in paper mill
environments has beenstudied recently(Suihkoet al., 2005).A totalof 177
anaerobicallygrownisolateswerescreenedfor aerotolerance,fromwhich 67
obligate anaerobeswerecharacterisedby automatedribotypingand one isolate
fromeachribogroup was furtheridentifiedby partial 16S rDNAsequencing.
The mesophilicisolatesindicated11 differenttaxa(species)withinthe genus
Clostridium and the thermophilic isolates four taxa within the genus
Thermoanaerobacterium(formerlyClostridium). The most frequentlyoccurring
clostridiawereclosest relatedtoC. magnum,C. peptidivorans,C. puniceumand
C. thiosulfatireducens. The phylogeneticpositionsof the mill isolates indicated
that most of them(69%) are potentialmembers of newspecies(partial16S
rDNA sequence similarity<99%)or evenof newgenera(similarity<95%).
Slime and claywereobservedto be goodreservoirs for these species in paper
mills,but theirspores tolerated the heat treatmentof the processand theywere
also present in end-products.
384 Handbookof hygiene controlin the foodindustry