28 years; 50 were between 15 and 24 years old only 14 of the US population is in this
age group. Another outbreak of E.coli O157:H7 occurred in December 2006 with 71 persons falling ill by consuming contaminated lettuce at taco Bell restaurant in USA.
Among the 71 persons with illness, 53 75 were hospitalized and 8 11 developed a type of kidney failure called hemolytic-uremic syndrome HUS. Another recent
outbreak in 2007 reported 10 ill persons due to consuming contaminated pizza. The age of ill persons ranged from 1 to 65 years with a median age of 9; 53 of ill persons were
female. At least 8 people had been hospitalized, and 4 had developed a type of kidney failure known as hemolytic-uremic syndrome, or HUS. No deaths had been reported.
2.3 Sources of Salmonella and Coliform bacteria contaminations
The primary source of Salmonella is the intestinal tract of humans and animals such as farm animals, birds, reptiles and sometimes insects Jay et al., 2005.
Transmission of the organism, which is excreted in faeces, may occur via insects that contaminate food or water, or by the unsanitary handling of foods by food
handlers Jay et al., 2005. The ingestion of Salmonella contaminated foods result in salmonellosis or Salmonella poisoning, which consists of a variety of disease
syndromes: bacteremia, focal infections, enteric fever and enterocolitis, the most common of all illnesses Darwin and Miller, 1999.
Figure 3. Fecal – oral routes of transmission of food-borne intestinal pathogens. The direction is from bottom to top.
Source: Jay, 2000
MOUTH
Toddler objects Foods utensils
Edible foods
Fingers Animals and insects
Water
Feces
29 Recontamination of otherwise sound products through contaminated surfaces has
been observed in many cases and is a major issue. For example, unclean, insufficiently or inadequately cleaned pieces of equipment have been identified as the sources of the
pathogens are numerous. An interesting aspect is the impact of the micro-flora residing on food contact surfaces of processing equipment used in slaughterhouses, for which the
transfer of pathogens such as S. aureus, L. monocytogenes or Salmonella during slaughtering has been demonstrated Adams and Mead, 1983; Rorvik et al.,
1995;Giovannacci et al., 2001. An important element in the investigation of recontamination is the identification of transfer mechanisms. The impact of direct
airborne recontamination of products is frequently over-emphasized. It is probably limited to few product categories such as beverages, refrigerated dairy and culinary
products where multiplication can occur or to products with very low viable counts, such as dry infant formulae. Air filtration is usually performed in plants manufacturing
products for which a high probability of airborne recontamination has been identified. Airborne microorganisms are usually associated with dust particles or water droplets
aerosols and transmission is occurring due to airflow. Distribution of pathogens through aerosols is probably more important than through dust. A more systematic
approach to investigating transmission via air that is suitable for modeling has been started Aantrekker, 2002; Aantrekker et al., 2003a,b.
Containers, pumps or tanks used for holding or transporting unprocessed raw materials, such as raw meat and poultry or unpasteurized liquid egg, occasionally have
subsequently been used for processed products without any cleaning Morgan et al., 1993; Evans et al., 1996; Hennessy et al., 1996; Llewellyn et al., 1998. This certainly
represents a major deviation from good hygienic practices. Recontamination has also occurred as the consequence of ineffective or inadequate cleaning and disinfection. The
poor hygienic design of equipment is then often the cause of these problems. Attention must be paid to a correct design of equipment and helpful recommendations in this
respect as well as guidelines for the validation of equipment cleanability have been published EHEDG, 1997.
Publications describe the impact of, for example, aerosols from drains on the dissemination of L.monocytogenes in fish processing facilities Rorvik et al., 1997,
from drip trays, cooling units Goff and Slade, 1990; Anonymous, 1999 or through
30 hosing under high pressure. The probability of contamination has been modeled by
different authors and either linear or quadratic relationships between the number of microorganisms in the product and the air have been proposed Radmore et al., 1988.
Dripping and splashing is of course also an important mode of spreading microorganisms and the mathematical distribution of microorganisms from falling drops
has recently been modeled Pielaat, 2000. Transfer of pathogens by food handlers, in particular from hands, is of particular
importance in the home and in food service establishments Chen et al., 2001; Montville et al
., 2001; Bloomfield, 2003. Many publications identified poor personnel hygiene. Deficient or absence of hand washing has in particular been identified as the causative
mode of transmission of the pathogens. Hands are considered very important in the transfer of organisms with low infectious doses such as Salmonella and Shigella, viruses
and pathogenic Escherichia coli Snyder, 1998. Quantifying the cross-contamination risk associated with various steps in the food preparation process can provide a scientific
basis for risk management efforts in both home and food service kitchens. However, if the product and the storage conditions support growth of micro-organisms, then this
mode of transmission and recontamination may become important for other pathogens as well.
During handling and preparation, bacteria are transferred from contaminated hands of food handlers to food and subsequently to food contact surfaces Montville et
al 2002. Poor hygiene particularly deficient or absence of hand-washing has been
identified as the causative mode of transmission Reij et al. 2003. Proper hand washing and disinfection has been recognized as one of the most effective measures to control the
spread of pathogens, especially when considered along with the restriction of ill workers Adler 1999, Montville et al. 2001.
Pests such as insects, birds and rodents have been recognized as important carriers of pathogens and other microorganisms Olsen and Hammack, 2000; Urban and
Broce, 2000. In one interesting case a Salmonella outbreak has been traced back to amphibians, which had accidentally entered the production facility Parish, 1998. While
massive direct recontamination can be excluded, sporadic cases may be attributed to these vectors. More important, however, is the transport and ingress of pathogens into
food processing environments and their possible establishment in suitable niches. Pest
31 management is therefore an essential preventive measure and guidelines have been
published Marriott, 1997. Food preparation surfaces in turn become contaminated by already contaminated
raw materials, contaminated hands of personnel preparing the food, rodents or insects acting as vectors Chen et al 2001. Pether and Gilbert 1971 and Scott and Bloomfield
1990 reported that various bacteria, including Escherichia coli, Staphylococcus aureus, and Salmonella spp., survive on hands, cloths, and utensils for hours or days after initial
contact with the microorganisms, this in turn most probably contaminate the food preparation surfaces.
Water is also a vehicle for transmission of many agents of diseases and continues to cause significant outbreaks of diseases in developed and developing countries
worldwide Kirby et al 2003. In Canada, an outbreak of E.coli was reported Kondro 2000 due to consumption of contaminated water. It is therefore important that potable
water is used throughout the production process, for cleaning equipment, or washing food, and preparing food.
Several studies previously carried out indicate that dish cloths or tea towels are vectors of unwanted microbial contaminations. Most of the organisms isolated were of
food-borne concern including Salmonella. Enriquez et al. 1997 isolated and identified 23 different bacterial species from 140 sponges, and 13 bacterial species from 56
dishcloths from US homes. The most common bacteria were Enterobacteriacae and Pseudomonas
spp. Salmonella species were identified in 15 of sponges and 14 of dish-cloths.
Salmonellae occur on foods: fruits and vegetables, poultry carcasses, in poultry
processing plants, and in poultry products van Nierop et al., 2005. Poultry products are regarded as the primary vehicles of
Salmonella transmission
Geornaras and von Holy, 2000. The birds that are brought to processing factories are a major source of Salmonella and Campylobacter as they occur on the feathers, skin
and in the alimentary tract of the birds. The birds may have acquired Salmonellae from contaminated feed, from environmental sources such as wild animals, rodents, birds etc.
or through transmission from parent to progeny in hatcheries Bremner and Johnston, 1996. Contaminated water sources by feaces of animals and humans carrying the
bacteria are also a common method of transmitting the pathogen.
32 Thus by far it can be seen that there are many ways to present to all how, where,
who, and why the microorganisms occur.
2.4 Ready-to-eat foods and outlets
