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Home , Food microbiology, Food technology

TRENDS IN

Hin-chung Wong

Department of Microbiology Soochow University

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1. HISTORY OF 2. CONVENTIONAL SYLLABUS OF FOOD MICROBIOLOGY. 3. FOOD MICROBIOLOGY IN THE CHANGING WORLD 3.1. International Trade 3.2. Consumers Trends and Communication 3.3. Development of New Technology 3.4. Development of New Ingredients 3.5. Protection food supply against Food Terrorism Event 3.6. Green movement 4. EMERGING OF NEW FOOD-BORNE PATHOGENIC 5. ANTIMICROBIAL RESISTANCE 6. TRENDS IN RESEARCH ABOUT FOOD MICROBIOLOGY 7. TRENDS IN FOOD MICROBIOLOGY EDUCATION 8. REFERENCES

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1. HISTORY OF FOOD MICROBIOLOGY

In the 1930s, microbiologists were mainly concerned with and spoilage. It means the study of natural flora of and the spoilage organisms, and killing of by various kinds of food preservations, e.g. , low temperature, low available , low pH, or inhibitory chemicals, etc.

In the U.S., Foodborne diseases were little heard in the 1940s. However, the only conventional food-poisoning bacteria mentioned in those days were botulinum and Staphylococcus aureus, and spp. was known quite clearly because of the works done to save the canning industry. Staphylococcal food poisoning was a frequent problem with cream-filled baked goods, cured ham, various salads, roast fowl, and occasionally, certain types of . Salmonellosis was believed to be transmitted by sick animals.

Other highlights in food microbiology are listed in (Table 1)(Foster, 1989). To name a few:

1959 were discovered in 1959, when thousands of turkey died in Great Britain after eating moldy peanut meal.

1960-1969 Type E botulism caused dealth in the early 1960s. Salmonella continued to be an important in food.

1970-1979 A new and unfamiliar agent, O27:H20, which caused outbreak of gastroenteritis in 1971. Disease outbreaks caused by Yersinia enterocolitica and jejuni were heard of near the end of the decade, but received little attention except from specialists in foodborne disease control.

1980-1989 C. jejuni emerged as the leading cause of gastroenteritis in U.S. Y. enterocolitica was also identified in several outbreaks of gastroenteritis, most of them from dairy products. E. coli O157:H7 first appeared in 1982 and ccaused serious outbreaks. Aeromonas hydrophila also was recognized in the early part of the decade as a possible cause of foodborne disease. Beside the conventional V. cholerae and V. parahaemolyticus, other species also attrached attention. L. monocytogenes also re-emerged as an important foodborne disease.

2. CONVENTIONAL SYLLABUS OF FOOD MICROBIOLOGY

Food microbiology is a course to study the relationship of habitat to occurrence of microorganisms of foods, the effect of environment on growth of various microorganisms in food, the microbiology of and food manufacture, the physical, chemical, and biological destruction of microorganisms in foods, the microbiological examination of foodstuffs, and and bacteriology (Anonymous, 1990).

The content of textbook "Microbiology of Foods" by Ayres et al. (Ayres et al., 1980) published in 1980 can be divided into the following parts:

Part I. General considerations: a general discussion on occurring in foods and the relationship of methods of and microorganisms.

Part II. including single cell and some oriental .

Part III. Specific Food Products, on the microbial flora and spoilage of various foods.

Part IV. Foodborne Illnesses

Other textbooks of food microbiology have similar contents. The emphasis of these authors on different parts can be estimated in term of ratio of pages covering each part to the whole volume (Table 2). A number of emerging foodborne and the recent development of new detection technologies are not included in these textbooks.

Table 2. Comparison of the contents of several textbooks of food microbiology

Number of Pages (/whole volume)

______Textbook Part I Part II Part III Part IV Introduction and Fermentation Various Foodborne Processing Food Diseases ______

Ayres et al. 146 (21%) 102 (15%) 281 (41%) 152 (22%) 1980 Jay, 1984 251 (54%) 32 (7%) 85 (18%) 93 (20%) Frazier and Westhoff, 311 (61%) 87 (17%) 157 (31%) 67 (13%) 1978 Banwart, 325 (66%) 36 (7%) 30 (6%) 102 (21%) 1981 ______

3. FOOD MICROBIOLOGY IN THE CHANGING WORLD

3.1. International Trade

International trade has been growing rapidly. Raw foods and also prepared foods are distributing internationally. Also food industries have been seeking international coorperation and have different plants all over the world and that would enhance the distribution of local foods, e.g. the sales of Chinese or Japanese foods have been rising rapidly in the U.S. Importance of the microbiology of these foods will be increasing. To avoid importing foreign foodborne pathogens or to avoid exporting foods containing pathogens, more intensive monitor of foodborne pathogens is required, e.g. the V. cholerae in exporting aquaculture to Japan, L. monocytogenes in exporting foods to U.S.A.

In Taiwan, the introduction of fast-food chain service systems has gradually changed the attitude of the local consumers. Microbiological quality control of the central kitchens of those chain systems is becoming very important.

Foodborne may increase in the coming years as a consequence of increased globalization of our food supply (Onwulata et al., 2008).

3.2. Consumers Trends and Communication

Changes of consumer attitudes are significant (Table 3) since World War II. Women are no longer "traditional"-- a career wife, mother, and shopper. Consumers play less time to prepare food and shifted to emphasis on cost/benefit rather than price alone. Also play more attention on the /health and well-being perspective (Breidenstein, 1988). Since operation (restaurants) is becoming more and more important, microbiological quality assurance should be enforced to prevent outbreaks of food poisonings.

Residues, cholersterol, salt, , artificial coloring, additives, etc. (Table 4) are the hot topics of food risks to consumers and it is highly affected by the mass communication and education (Jolly et al., 1989). News emphasizes extraordinary events and skews risk perception (Lee, 1989). Perceptions of the public and expert of risks from eating food do not coincide. The experts rank microbial safety, over-nutrition and non-microbial safety (contaminants, natural , agricultural chemicals and food additives) on the top of the rank of hazards, while the public rank , new food chemicals, familiar hazards ( and cholesterol, microbial spoilage, junk foods) on the top of this list (Lee, 1989).

From the study of foodborne pathogens, we know that foodborne pathogens are widely distributing and it is not realistic to avoid absolutely the contamination of any of these pathogens. What we could do is to minimize the risk of each of these pathogens. So we have to determine the risk of pathogens in different foods under different conditions.

The consumption of fruits and vegetables in the U.S. is growing. Fifty years ago, the total annual per capita consumption of fresh, canned, frozen, and dried fruits and vegetables was about 335 lb (fresh-weight basis); in 1985, it was about 406 lb. Between 1970 and 1985, per capita consumption of fruits and vegetables increased by 23%, and fruit juice by 20%. The factors responsible for this growth include new, high-quality products, higher disposable personal income, the desire of health-conscious Americans to include fruits and vegetables in their , and improved distribution systems. The U.S. fruit and vegetable processing industry has changed in terms of product mix and total product use. Consumption of most canned fruit and vegetable products has declined, while consumption of frozen and dried products has increased. The growing availability and use of fresh fruits and vegetables year-round has affected the demand or many traditional processed fruit and vegetable products (Pearl, 1990).

The shift to "lite" is apparent. People are looking for lower-calorie, lower-fat, lower-salt alternatives in the marketplace. They are also looking for foods perceived to have a high degree of nutrition, such as high-fiber and high-calcium foods. Most importantly, people are changing their food selection patterns to achieve what they perceive to be a "healthier" diet. Grain-based products fit the "new" emerging dietary patterns. They are perceived to be relatively low in calorie, low in fat, high in fiber, and high in complex . Wheat flour consumption in the U.S., on a per capita base, decreased significantly from the early part of the century to the mid-1970s, but from that point on a significant rise is seen. Consumption of rice-based products has been increasing since about 1960 (Leveille, 1988).

Public health professionals say the need for light dairy products is clear. Light dairy product is a dairy product which offers a material difference in a nutrition property which is of significant interest to consumers. It is not restricted to "reduced-calorie" dairy products, it may mean "low sodium" products or other types. Between 1980 and 1989 the share of fluid milk consumption accounted for by lowfat and nonfat milk rose from approximately 40% to almost 60%. Nonfat were introduced in 1988, lowfat yogurts perhaps ten year before that. In 1989 the combination of lowfat and nonfat constituted 80% of the entire yogurt market segment. It may be soon outstripped by the nonfat ice cream segment. "Nonfat" cottage cheese is catching on in the western U.S. (Thompson, 1990).

Recently, consumers concern on the food allergens and other health issues (Table 5) (Swientek, 2008).

Sales of functional products are rising across all food and drink categories in the U.S. and Europe alike, and growth rates are appreciably faster than those shown in mainstream food and drinks markets. The U.S. functional food market was worth $18.9 billion in 2004, with annual sales growth averaging 7.2% over the 1999–2004 period. It is forecast to grow at a slightly slower but still significant 5.7% over 2004–09, far outstripping growth in the overall food and beverage market. Dairy products are the second most popular nutraceutical category in the U.S., with consumers spending $5.0 billion on functional dairy food in 2004. Most adults have been told from childhood that milk is an essential part of a . This makes it particularly worthwhile to launch functional milk variants targeted at improving bone health, as well as functional yogurt variants targeted at gut health (Vierhile, 2006)

Similar changes of consumers' attitude are also significant in Taiwan. People in Taiwan are consuming more and more the prepared refrigerated or frozen foods which are usually made of mixed meats, seafood, vegetables and other raw materials. So, there is a risk of mixing bacteria from different origin and spreading of certain pathogens.

3.3. Development of New Technology

The advancement of modern biotechnology has great impacts on the (Fig. 1) (Harlander, 1989).

Detection Technologies

The first priority of the food industry is ensuring a wholesome food supply that is free of pathogens and toxins. Quick detection methods have been developed for various toxins and pathogens based mainly on the immunoassays and molecular methods. Rapid and sensitive methods based on the development of DNA probes and poly-and monoclonal antibodies have begun to replace classical microbiological techniques for detection of potentially pathogenic microorganisms. Kits are currently available for detection of common foodborne pathogens and toxins. Polymerase chain reaction (PCR) will dramatically improve the sensitivity of DNA probe-based assay systems. are developed for preventing the potential threat of bioterrorism and emerging diseases (Fig. 2, 3) (Blyn, 2006).

Nanotechnology has been employed in the development of biohazard detection method, such as the “super cloth”. Super cloth is a high-surface area and high-absorbency non-woven fabric made from very fine fibers incorporated with bio-recognition agents such as DNA strands, RNA strands, or antibodies. The detection systems are based on biotin- binding. Polylactic acid and streptavidin are used as the fiber and protein, respectively. The bio-recognition agents provide high specificity for detecting target biohazards (Bugusu, 2008).

Production of Food Ingredients

Many potential food ingredients including , pigments, aromatic and compounds, etc. may be produced by natural or engineered microorganisms (Table 6, 7) (Anonymous, 1988b; Gatfield, 1988). Biotechnology has been applied to change the constituents of food crops. Low-linolenic soybeans were introduced in 2005. Also now available are a naturally stable sunflower and a low-linolenic canola oil. These crops produce oils that do not have to be partially hydrogenated, thereby reducing trans fatty acids. Adding hydrogen is necessary to keep certain oils stable, but the process results in trans . As research increasingly has raised health concerns about trans fats, the UDA now requires food manufacturers to list the amount of trans fats on their labels. To avoid such listing, some manufacturers have switched to oil from new low-linolenic soybean varieties, which enable them to continue using soybean oil while avoiding trans fats and high amounts of saturated fats that substitute oils contain (Magin, 2006).

Improvement of Traditional Fermentations

The most advanced dairy fermentations function at a level of sophistication considerably lower than that of pharmaceutical fermentations. Meat fermentations are another order of magnitude lower, and vegetable fermentations are yet another order of magnitude lower (Table 8, 9) (Anonymous, 1988b). Genetic engineering provides an alternative to classical mutation and selection for improving microbial starter cultures. To date, primary emphasis has been placed on construction of multifunctional food-grade cloning and expression vectors and development of high-efficiency gene-transfer systems. The ultimate goal is to construct strains with improved metabolic properties (Harlander, 1989).

Control of production

The potential for using microorganisms to detoxify shows promise. Exposure of deoxynivalenol (DON) to microbes contained in the contents of the large intestines of chickens resulted in complete transformation in vitro to de-epoxy-DON, which is 24 times less toxic than DON. Similar findings were demonstrated with the microflora of cow intestines.

Genetic modification of susceptible plants via a number of transgenic approaches holds great promise. One approach involves increasing production of compounds such as antifungal proteins or secondary metabolites that reduce by the microorganism. This may be accomplished by introducing a novel gene to express the target compound. Another option is to enhance expression of such a compound by the existing gene, capitalizing on the plant’s own defense mechanisms. Alternatively, methods to increase production of enzymes that degrade mycotoxins are also being pursued (Murphy et al., 2006).

Use of

Phages are found in enormous numbers in the environment and in our food. Millions of phages exist in our digestive systems, and we regularly consume millions more with food and water. While this alone provides overwhelming evidence of their safety.

Decades of extensive use in medical applications—with exposure to phages not limited to oral uptake, but rather systemic application being common—showed no adverse effects whatsoever. Specific safety-related research has also been performed. An oral toxicity study with rats receiving high doses of -phage Listex P100 did not reveal , and a study in humans, with E. coli-specific phages able to infect commensal E.coli strains as well as pathogenic strains, failed to show any adverse effects. Two simple safety rules should be kept in mind: temperate phages—easily discernible through genome analysis—should be avoided. Also, phages capable of generalized transduction should be avoided unless the production host is non-pathogenic.

The U.S. food industry is mostly concerned with the “big four” food pathogens: Listeria monocytogenes, Salmonella, Campylobacter, and pathogenic E. coli. Of these, only Listeria regularly colonizes production facilities and thus is able to contaminate food very late in the production process. Therefore, phage treatment at the stage where this contamination is likely to take place is the logical conclusion.

For many foods, this will be at some point prior to packaging, but cheese, for example, may be vulnerable to contamination throughout the ripening stage. A number of studies on successful phage treatment of various foodstuffs contaminated with Listeria have been published. The other three organisms do not regularly colonize facilities, and it is usually raw products that introduce contamination. As a matter of fact, these organisms colonize animals whose meat is used for human consumption. Therefore, one possible treatment is application of phages during livestock farming, in addition to—or as an alternative to—treating the meat after slaughter. Studies have been undertaken to treat chickens with phages against Salmonella and Campylobacter and to treat ruminants with phages targeted against pathogenic E. coli.

Treatment of facility surfaces is also a possibility. Food-contact surfaces, in particular, could be cleaned effectively using phages, even during production, without interrupting manufacturing processes. In the United States, several applications have been approved for use and approved as GRAS. These applications are against Listeria, methicillin-resistant Staphylococcus aureus (MRSA), Salmonella, E. coli, and Campylobacter (Hagens and Offerhaus, 2008).

Waste Management

Creative handling of food-processing waste streams could produce variable products, e.g. biofuel, specialty chemicals which could be used in the industrial sectors or as pharmaceutical products (Harlander, 1989).

Development of New Methods of Preservation and Processing

New technologies are being developed, that include controlled atmospheres in the packaging of meats produces or other foods, asceptic packaging, extrusion, ultrafiltration, etc. New technologies lead to the generation of novo food products, and also new microbiological problems.

3.4. Development of New Ingredients

A number of new ingredients are produced or introduced into the food systems, e.g. the non-caloric sweeteners, enzymes, colors, flavor compounds, low-calorie oils, antimicrobials, cyclodextrins, et. Microbiological quality, growth and survival of certain bacteria may be altered by some of these compounds in food systems.

Some examples are listed as follows:

Acesulfame-K is an artificial sweeteners manufactured by Hoechst Co., and it has been approved to use by a number of countries since 1983.

Sucralose is derived by the selective chlorination of sucrose at the 4,1', and 6' positions. It yields a white crystalline powder that has intense sweetness (400 to 800 times that of sucrose) and high solubility in water approximately 28% at 20C). It is extraordinarily stable and easy to incorporate into food and beverage products using traditional food processes. It is nontoxic, and that it is not carcinogenic, teratogenic, mutagenic, or caloric (Anonymous, 1988a).

Isomalt is an energy-reduced bulk sweetener, it is actually a sugar alcohol or polyol produced from sucrose. In small intestine, isomalt is only partially hydrolyzed and absorbed. Similar properties are observed in xylitol, another sugar alcohol (Pepper and Olinger, 1988). Therefore, it does not lead to any appreciable increase in blood sugar or insulin levels, which makes isomalt suitable for diabetics. Other sugar alcohols include , maltitol, maltotriitol and hydrogenated oligosaccharides (Anonymous, 1988a). Xylitol may also contribute to improved dental health by interfering with the formation of new cavities and the progression of existing caries. It is not fermented by oral bacteria and it has inhibitory effect on Streptococcus mutans (Pepper and Olinger, 1988). Major suppliers of alternative sweeteners are listed in Table 10.

Low-caloric Oils Low-caloric oils are being investigated by substitute for or reduce the caloric value of oil-like substances in food. Water-soluble compounds (such as polydextrose, tapioca dextrin, maltodextrins), modified (e.g. fatty acid esters, sucrose polyester), polycarboxylic acid esters, sterically hindered esters, medium-chain triglycerides and polyglycerins, or conversion of the ester linkages of triglycerides to ethers, etc. (LaBarge, 1988). Sucrose polyester may only cause mild side effects on gastrointestinal problems. Flatulence, soft stools, anal leakage, diarrhea, and increased urgency or frequency of bowel movements have been reported (Toma et al., 1988).

Enzymes: Heat-stable from Thermomonospora fusca may be used in the production of protein hydrolysates from either plant, fish, or animal proteins, or for the cleaning of protein-solid ultrafiltration or reverse osmosis membranes (Gusek and Kinsella, 1988). Novel can be used in cheese production and other dairy products modifying flavor of the products.

Cyclodextrins are cyclic molecules that have been derived enzymatically from starch and have the ability to encapsulate other molecules within their ringed structures. Cyclodextrins or modified ones could be used in controlling flavor release, masking odors and tastes, stabilizing emulsions, increasing foaming power, controlling or masking color, debittering of grapefruit juice, etc. (Anonymous, 1988c)

Antimicrobial Substances: Antimicrobial substances such as hydrogen peroxide, diacetyl, , and reuterin are produced from . Bacteriocins have been recognized and have been the subject of much recent investigations. Hydrogen peroxide is approved for use in applications such as bleaching and modification of food starch but not as an antimicrobial agent in foods. Diacetyl and lactic and acetic acids are listed as GRAS. , after 25 years of safe use in many European countries, was affirmed by FDA (1988) as GRAS for use as an antimicrobial agent to inhibit the outgrowth of C. botulinum spores and action was based on the accumulated body of scientific data indicating that nisin is nontoxic, nonallergenic, and a safe effective antimicrobial (Daeschel, 1989).

3.5. Protection food supply against Food Terrorism Event

Food may be a source of risk to human by accidental () and an intentional (food defense) contamination. Accidental food contaminations are typically associated with innate pathogenic microorganisms and their natural proliferation pathways. Intentional contamination, on the other hand, is associated with a select group of unfamiliar agents that typically have high mortality rates. While both have the potential to inflict harm and cause significant economic losses. A terrorist attack against the food supply chain would target access points that would render the greatest impact—the goal being to cause high morbidity and mortality, widespread economic disruption, and fear. Microorganisms concerned in accidental and intentional contamination events are listed in Table 11 (Takhistov and Bryant, 2006).

3.6. Green movement

Both manufacturers and consumers are embracing the green movement. The percentage of consumers who purchased products made with recycled packaging and/or manufactured in an energy-efficient, environmentally friendly way jumped from 12% in August 2006 to 36% in December 2007 in Mintel, a company. Mintel noted that while some of the food products labeled as eco-friendly were organic and natural, others focused on different environmental issues such as Green Energy Credits logos on packaging or support for health associations. European consumers, too, are purchasing more products positioned as eco-friendly, including those that feature reduced packaging, are made with biodegradable packaging, and are labeled certified organic and/or fair trade. About 27% of European consumers bought these products in 2006, and in Europe, more than 60% of new product launches in 2007 were of these environmentally friendly products (Nachay, 2008).

4. EMERGING OF NEW FOOD-BORNE PATHOGENIC BACTERIA

Foodborne illness is not a simple problem in need of a solution; it is a complex combination of factors that must be managed on a continual basis. A number of factors will drive the emergence of new food safety concerns, including changes in the characteristics of the consuming public, changes in the foods we manufacture and sell, changes in the hazards themselves, and changes in the ability of public health officials to identify illnesses as foodborne and to trace the illnesses to their food source (Arthur, 2002).

In addition to the well-known food poisoning microorganisms (Enteropathogenic E. coli, Campylobacter, Yersinia, , Staphylococcus aureus, Salmonella, Shigella, cereus, etc), the importance of some new microoganisms are recognized or being evaluated.

Aeromonas species

During the past several years there has been increasing speculation regarding the possible role of A. hydrophila, A. sorbria and A. caviae as a cause of human gastroenteritis. There is sufficient evidence to indicate that A. hydrophila can produce fatal septicemia in individuals debilitated by some other disease or condition.

Edwardsiella tarda

It is known as pathogen of catfish or other fishes especially in the warm water. It is also caused in the cultured crimson sea breams in Japan. It has also been implicated in gastroenteritis in humans, wound infections and meningitis. The incidence of E. tarda in catfish is somewhat uncertain. It is reported the organism present on 79% of the domestic fish and 30% of the imported fish examined.

Enteric

Human enteric viruses appear to be the major cause of shellfish-associated viral disease. Presently, there are more than 100 known enteric viruses which are excreted in human feces and ultimately find their way into domestic sewage (Table 12) (Gerba, 1988). A few have been shown epidemiologically to be transmitted by shellfish: , non-A, non-B hepatitis, Norwalk, Snow Mountain agent, astroviruses, caliciviruses and small round viruses. Lack of methods for detection and the difficulty of recognizing viral disease outbreaks have the difficulty of recognizing viral disease outbreaks have probably precluded the list from being longer. Some epidemiological studies have suggested that shellfish may play a significant role in the transmission of hepatitis A virus (Gerba, 1988). In laboratory studies, enteric viruses have been reported to survive from 2 to 130 days in seawater, and they generally survive longer in such environments than do coliform bacteria.

Plesiomonas shigelloides

P. shigelloides (formerly Aeromonas shigelloides) has been implicated in human gastroenteritis for 40 years. Symptoms of the infection include diarrhea, abdominal pain, nausea, chills, fever, headache, and vomiting, etc. (Hackney and Dicharry, 1988). It is widespread in nature, being mostly associated with fresh surface water, but may also be found in seawater. It is more often isolated during the warmer months. Some strains can grow at refrigerating temperature (Hackney and Dicharry, 1988; Ward, 1989).

Vibrio species

A number of Vibrio species cause gastroenteritis, wound infection, ear infection, or septicemia in human beings (Table 13) (Hackney and Dicharry, 1988). These pathogenic Vibrio species include V. cholerae O1, O139 and non-O1, V. parahaemolyticus, V. vulnificus, V. mimicus, V. hollisae, V. furnissii, V. fluvialis, etc. Fewer than 5% of the non-O1 strains from human sources in the U.S. produce cholera . Associated symptoms of gastroenteritis have included diarrhea, abdominal cramps, fever, nausea, vomiting. Almost all of the cases of non-O1 V. cholerae infections in the U.S. have been associated with eating raw oysters; but egg and asparagus salad and potatoes have also been vehicles for the bacteria.

Since 1992, a new pandemic strain of V. cholerae O139 occurred and rapidly spread over many countries (Faruque et al., 2003; Wong et al., 2002). Also, the occurrence of O3:K6 strains of V. parahaemolyticus widely spread all over the world and are recognized as the first pandemic strain of this species (Chiou et al., 2000; Wong et al., 2000).

Enterobacter sakazakii

Infection by E. sakazakii is an extremely rare event. Six of the 58 reported cases of E. sakazakii infection worldwide involved individuals more than four years of age, and the median age was 74. The vast majority (83%) of cases have been reported in infants less than one year of age, where the fatality rate ranged from 30% to 80% despite antibiotic treatment. Infants born at less than 36 weeks gestational age were at risk until six weeks post-term. Illness symptoms normally appear a few days after birth, and the health of the infant rapidly deteriorates. Infection may result in meningitis (58%), necrotizing enterocolitis (29%), or sepsis (17%). In one outbreak in which 11 infants were positive for E. sakazakii, one developed meningitis and four others had clinical signs of severe sepsis, although the microorganism could not be isolated from the blood. Bacteremia is often, but not necessarily, confirmed. The severe consequences of infection in some cases may be linked to the production of enterotoxin by E. sakazakii. More than 20% of the 18 tested strains produced enterotoxin. When infection does not result in death, the affected infant may have permanent neurological or developmental deficiencies. In one case, mortality was averted by months of antibiotic treatment, but the patient was mentally retarded and paralyzed by age two. Infants may be colonized with E. sakazakii without developing symptoms (Gurtler et al., 2005).

5. ANTIMICROBIAL RESISTANCE

Use of antimicrobials, more specifically antibiotics, can create selective pressure that leads to emergence of antimicrobial-resistant microorganisms. Bacterial strategies for resisting antimicrobials include impaired uptake, modification or overproduction of the target site, bypass of sensitive steps, absence of enzymes or metabolic pathways, efflux, enzymatic degradation, receptor alteration, and change in membrane permeability.

Bacteria may also experience stress adaptation (resistance stemming from exposure to subinhibitory levels of stress that trigger stress-response protein transcription and translation), co-selection (resistance to antimicrobials having unrelated targets, stemming from separate genes transferred together), cross-resistance (resistance to antimicrobials having the same molecular targets), and crossprotection (in which adaptation to one stress is associated with increased resistance to another, unrelated stress).

Antibiotic resistance among foodborne pathogens may create an increased burden on human health in different ways. For example, resistant pathogens contaminating food animals have the potential to reach humans; human use of antibiotics may increase the risk of acquiring an infection with an antimicrobial-resistant pathogen; human infection with a resistant microbe may limit illness treatment options (in the uncommon instances of in which antibiotic use is warranted); and antibiotic-resistant foodborne pathogens may develop increased virulence.

The extent to which antibiotic use in food animals produces clinically important antibiotic resistant infections in humans is unknown (Fig. 4). There is evidence that points to but does not prove that antibiotic use in food animals poses a human health threat. There are very few data regarding food animal-to-human transfer of antimicrobial resistance to indicate more frequent or severe infections or increased morbidity and mortality.

Food product modifications, such as changes in formulation or processing conditions, may lead to sublethal stressing of microbes. Surviving microorganisms may have increased resistance or virulence. Some antimicrobial treatments may lead to dominance of acid-resistant pathogens. For example, spraying meat carcasses with organic acids may select for survival of acid-tolerant E. coli O157:H7 (Doyle, 2006).

6. TRENDS IN RESEARCH ABOUT FOOD MICROBIOLOGY

We will increase our reliance on food processors and we now know it is impossible to eliminate all risks. Thus the best we can do is to minimize the risk. According to the USDA, investigations are mostly concerning harmful bacteria including Salmonella, Shigella, Campylobacter, E. coli, Yersinia enterocolitica, and Listeria monocytogenes. Quicker and less expensive methods of detecting harmful microorganisms and chemical residues are being studied. Studies focus on the most pathogenic strains of microorganisms; and development of ways to prevent mycotoxin formation in growing plants (Carter, 1999; Hackney and Dicharry, 1988).

Papers in food microbiology conducted in departments of or other institutions published during the period 1988-1989 on the Journal of Applied Bacteriology and also during the 1988-1990 on the Applied and Environmental Microbiology were briefly analyzed. It indicated the research activities about food microbiology at that time. These two journals are well respected journals concerning food microbiology. A number of papers about the contamination, survival of food pathogens or spoilage microorganisms are also published in other journals such as Journal of Food Protection, , International Journal of Food Microbiology, etc.

Methodology in and detection, genetics & molecular studies, occurrence & spoilage, and toxin studies are the most popular fields of research in food microbiology. Some papers about the toxin and molecular studies also appear on other journals.

Papers on the incidence of poilage or pathogens in food were analyzed. This kind of study most concern about different pathogenic bacteria in various kinds of foods usually of high risk, e.g. Vibrio in seafood, Aeromonas in water or aquaculture, Listeria in dairy products, Campylobacter in meat, etc. Papers on the growth and survival of microorganisms included the survival of microorganisms in various kinds of food and also the effects of bacteriostatic or bacteriocidic chemicals (e.g. nisin, disinfectants, acid), or processes (heat, controlled air..). Physiological and biochemical behaviour were also concerned by some papers, e.g. the production of enzymes (proteolytic enzymes, endonuclease, pectinase, lipase, etc.) during the growth of certain spoilage or pathogenic microorganisms.

Most of the studies on the phage, plasmid, and other molecular aspects of food-related microorganisms concerned about lactic acid bacteria, namely, Streptococcus (), , , etc. Methods involving various techniques were developed, e.g. immunoelectrical method in the detection of S. aureus (the -immuno detection signal was amplified by electrical method). Various formats were employed in the immunological methods, e.g. latex agglutination, reverse phase latex agglutination, enzyme immunosorbent assay (ELISA), filter-method, immunomagnetic separation, etc. Monoclonal antibodies were used in some studies. Protease was also detected by ELISA. Molecular methods were developed in the 90’s.

Overall speaking, the Listeria, Staphylococcus, Vibrio, Clostridium, E. coli were the most intensively studied bacteria in addition to mycotoxin producing fungi in the 90’s.

Similar research subjects and microorganisms are also frequently investigated in recent year (2008) (Table 14, 15). Table 14. Subjects of papers published in 2008 in Journal of Applied Microbiology and International Journal of Food Microbiology

Topics JAM # IJFM # Total % Incidence, prevalence, 24 43 67 13 spoilage Growth, survival, 42 42 84 17 Processing Fermentation 24 45 69 14 Enzyme 3 7 10 2 Bacterial Spore 3 2 5 1 Antimicrobials 21 24 45 9 Genetics & molecular 22 21 43 8 Isolation and detection 26 30 56 11 Culture 10 10 Immunology 4 3 Molecular 12 17 Pathogens 29 11 40 8 Bacterial toxin 8 7 15 3 Health food 13 14 27 5 12 7 19 4 Mycotoxin 2 26 28 6

Table 15. Microorganisms studied in papers published in 2008 in Journal of Applied Microbiology and International Journal of Food Microbiology

Microorganisms JAM # IJFM # Total % bacteria 0 13 13 3 Aeromonas 2 1 3 1 Alicybacillus 0 1 1 0 Aureobasidium 1 0 1 0 Bacillus 10 8 18 4 Brucella 1 0 1 0 Burkholderia cepacia 3 0 3 1 Campylobacter 6 12 18 4 Clostridium 2 9 11 2 Edwardsiella 1 0 1 0 E. coli 29 18 47 10 sakazakii 5 3 8 2 Enterococcus 3 7 10 2 Klebsiella 0 1 1 0 Helicobacter 2 1 3 1 Lactic acid bacteria 52 63 115 25 Listeria 11 36 47 10 Salmonella 9 17 26 6 Staphylococcus 4 13 17 4 Vibrio 10 9 19 4 Yersinia 0 4 4 1 12 36 38 8 20 26 46 10 Viruses 5 12 17 4

Food Industry Research Interests

Industry research needs are varied. Specifically, the research needs are: • Structure-function/nutrition of health-promoting wholesome foods with multi health benefits and new processing technologies to protect and concentrate nutrients such as phytonutrients and folic acid and flavor/aroma phenols. • Enhance quality and new uses (product innovations). Develop and implement methods to improve processing and end-product quality and develop rapid measurements for functionality and nutrient prediction. • Develop healthy and flavorful, value-added products (e.g., bran, oil, protein) to maximize health benefits through processing and address health/obesity. • Develop new delivery techniques for nutrients (e.g., delivery of ) and develop new processing technologies for nutrient identification, characterization, stabilization, and delivery. • Develop knowledge and understanding of bio-—nutrient/food interaction. • Improve quality. Conduct enhanced value-added research for food and feed, improving quality of harvested and processed produce, quality of produce in controlled atmosphere, and reducing quality loss in storage. Develop postharvest practices for optimizing quality through improved monitoring. • New technologies for processing streams. Develop processes to recover more feed and fiber from waste by the removal of harmful substances such as allergens, gossypol, or acrylamide, and through process enhancement and recovery of food-based byproducts. • . Provide more quality food through new technologies and enhanced nutrient retention. Also, nanotechnology has the potential to generate new products for the food industries with numerous benefits in smart packaging, nanosensors for food safety, food nutrient delivery systems, nanoemulsions, etc. (Onwulata et al., 2008).

7. TRENDS IN FOOD MICROBIOLOGY EDUCATION

Food microbiology was an important course in Bacteriology or Microbiology departments several decades ago in the western world. Nowadays, nearly all the food microbiology course is conducted in food science or related departments. Considering the facts or trends discussed above, the syllabus of food microbiology for undergraduate or graduate levels should cover the following contents:

Part I General Considerations

1. A brief introduction to the world of microbiology. 2. Microorganisms occurring in foods, especially in some new food systems. 3. Relationship of conventional and new methods of food processing and microorganisms, including the introduction of new chemicals. 4. An introduction to biotechnology and the advance of conventional or new identification methods. Numerical or computer-assisted classification should also be introduced. 5. Microbiologic quality assurance of food processing plants or restaurant should be discussed.

Part II Food Fermentations

1. Application of biotechnology in culture and process improvements. 2. Fermentation and microbiology of fermented foods of Oriental or African countries should be discussed in addition to traditional food fermentation. 3. Production of enzymes or other food ingredients by microorganisms should be discussed. 4. Waste treatment of food processing plants by microorganisms should also be discussed. 5. Include the application of different microorganisms in health food.

Part III Microbiology of Specific Food Products

1. Discuss on the microflora of raw food materials and traditional foods. 2. Also discuss on the microflora and spoilage of new food systems, e.g. light dairy products, low-calorie foods, vacuum packed foods, foods packed in controlled atmosphere, etc.

Part IV Foodborne Illnesses

1. Should discuss on the occurrence and incidence, growth and survival at different environments or in foods, toxin production and briefly on the pathogenicity of well-known and emerging pathogensk, and also the effect of environmental stresses. 2. Since the identification of pathogenic or toxigenic strains employs sophisticated techniques, brief discussions on the immunology and molecular biology should be included. 3. Should play more attention on some local foodborne pathogens e.g. the Vibrio, Aeromonas, enteroviruses and mycotoxin producing fungi are important in tropical or subtropical coastal countries. 4. Should also discusson the emerging foodborne pathogens, and global climate changes on the foodborne pathogens.

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