application of alternative food-preservation - Bentham Science

Food Microoganisms Application of Alternative Food-Preservation Technologies 19
Some pathogens are referred as primary pathogens; otherwise, there are some microorganisms labeled as
opportunistic pathogens, as they infect immuno-compromised individuals. Nevertheless, both the primary and
the opportunistic pathogens show some basic attributes, known as “attributes of pathogenicity” (Table 1) and a
common mechanism of pathogenesis (Table 2).
Randell and Whitehead [5] divided food-borne pathogens and parasites into three classes as a function of the
hazard associated with human health diffusion. The classification is the following:
1. Category 1 (severe hazards), including Cl. botulinum types A, B, E and F, Sh. dysenteriae, Salm.
enterica servovars Paratyphi A and B, E. coli EHEC, Hepatitis A and E viruses, Br. abortis, Br.
suis, V. cholerae O1, V. vulnificus, T. solium.
2. Category 2 (moderate hazards, potentially extensive spread), including L. monocytogenes,
Salmonella sp., Shigella spp., E. coli, Streptococcus pyogenes, Rotavirus, Norwalk virus group, E.
histolytica, Diphyllobothrium latum, Ascaris lumbricodes, C. parvum.
3. Category 3 (moderate hazards, limitate spread), including B. cereus, Camp. jejuni, Cl. perfringens,
Staph. aureus, V. cholerae non O1, V. parahaemolyticus, Y. enterocolitica, G. lamblia, T. sagitata.
Many foodborne pathogens are ubiquitous and generally recovered in soil, humans, animals and vegetables; they
are introduced into an equipment through the raw material or by humans, due to a not correct manipulation and
low level of hygiene standards.
A topic of great interest, reported by Bhunia [4], is the persistence of foodborne pathogens on the surfaces of
equipments; the data available for some pathogens are the following:
Camp. jejuni, up to 6 days;
E. coli, 1.5h-16 months;
Listeria spp., 24h-several months;
Salmonella Typhi, 6h-4 weeks;
Salmonella Typhimurium, 10 days-4.2 years;
Shigella spp., 2 days-5 months;
Staph. aureus, 7 days-7 months.
Foodborne Pathogens and Indicators
In some cases microbiological criteria (MC) for food safety propose the evaluation of indicator microorganisms,
rather than of the pathogen of concern; for example E. coli in drinking water is the sign of fecal contamination
and can indicate the possible presence of other pathogens [6].
An indicator microorganism should possess at least 7 characteristics:
Detectable easily and in a short time.
Distinguishable from the naturally occurring microflora.
Always associated with the pathogen under investigation.
Its cell number is correlated with the contamination due to pathogen.
Growth requirements equal (or similar) to those of the pathogen.
Growth kinetic similar to that of the pathogen.
Absent when the pathogen is absent.
The classical example of the indicator microorganisms is that of the fecal coliforms.