Background And Historical Significance

Although food microbiology is a relatively young scientific field, foodborne and waterborne pathogens have been recognized for almost 200 years. Vibrio chol-erae consists of several serogroups, with V. cholerae Ol being the etiologic agent of the disease cholera, which has been documented as far back as 1817, the time of the first known pandemic. In 1854, the organism was first described and the connection between cholera and drinking water was hypothesized. The hypothesis was later proven, when in 1883 Robert Koch sampled suspect pond water and isolated the bacillus (Murray et al., 1999). In 1992, the serogroup V. cholerae 0139 Bengal was identified during an epidemic in India. In addition to these serogroups, other non-01/0139 V. cholerae have been identified and are collectively referred to as nonagglutinating vibrios (NAGs) (Jay, 2000). It is estimated that toxigenic V. cholerae are responsible for 49 cases of foodborne disease in the United States annually, with a case fatality rate of 0.006 (Mead et al., 1999).

In 1880, Eberth discovered Salmonella Typhi, the etiologic agent involved in typhoid fever. In 1884, Gaffky isolated the organism that, in 1900, Lig-nieres named after Dr. Salmon, in light of his work involving the isolation of S. Cholerae-suis from swine suffering from hog cholera (ICMSF, 1996). The first scheme for Salmonella classification, based on antigenic variation, was proposed in 1926 and was expanded in 1941 into the Kauffmann-White scheme (Doyle et al., 1997). Between 1988 and 1992, Salmonella was implicated in 69% of documented bacterial foodborne disease outbreaks in the United States; 60% of those outbreaks involved S. Enteritidis (Centers for Disease Control and Prevention, 1996a). Salmonella is currently the second most common bacterium implicated in foodborne disease outbreaks in the United States, with nontyphoidal strains causing an estimated 1.3 million cases annually and having a case fatality rate of 0.0078 (Mead et al., 1999).

Originally known as Bacterium coli, Escherichia coli was isolated by Theodor Eseherieh over a century ago and by the mid-1940s was implicated as a cause of gastroenteritis and significant mortality among infants (ICMSF, 1996). The recognition of Shiga toxin-producing E. coli (STEC) as its own individual class of diarrheagenic E. coli resulted from two observations in 1982. The first was the observation of characteristic symptoms associated with patients from two outbreaks involving restaurants of a fast-food chain in two states, where the etiologic agent was a previously rarely isolated serotype, 0157:H7. The second observation involved sporadic cases of hemolytic uremic syndrome (HUS) in individuals that produced stools containing cytotoxin-forming E. coli (Blaser et al., 1995). Currently, diarrheagenic E. coli is estimated to be implicated in over 170,000 cases of foodborne disease annually in the United States; the case fatality rate for 0157:H7 and non-0157:H7 STEC is 0.0083 (Mead et al., 1999).

The name "staphylococcus" originated from the Greek root staphyle, referring to grapes, and in 1882 was used for taxonomic designation of pathogenic, cluster-forming cocci. The association between staphylococci and foodborne illness was suggested in 1884, while in 1914, Barber reported illness symptoms in individuals after the ingestion of milk containing Staphylococcus aureus. The role of toxins in staphylococcal food poisoning (intoxication) was demonstrated in 1930, when ingestion of S. aureus cell-free filtrates led to development of clinical symptoms (Jay, 2000; Lund et al., 2000). It is estimated that S. aureus is responsible for 185,000 cases of foodborne disease annually in the United States, with a case fatality rate of 0.0002 (Mead et al., 1999).

Although Bacillus cereus was first isolated and described in 1887, and despite the longstanding recognized relationship between aerobic, endospore-forming bacteria and foodborne illness, it was not until the early 1950s that it became established as an etiologic agent of foodborne disease (Doyle, 1989; ICMSF, 1996). Currently in the United States, B. cereus is estimated to cause approximately 27,000 cases of foodborne illness annually, although the number of deaths attributed to this agent is extremely low (Mead et al., 1999).

In 1894, Yersin isolated the etiologic agent of plague, and in 1944, Van Loghem defined the genus Yersinia, proposing the inclusion of Pasteurella pes-tis and P. pseudotuberculosis; Pasteurella X, or Bacterium enterocoliticum, was included in the genus Yersinia in 1964 (Murray et al., 1999). Only since 1976 has the transmission of Y. enterocolitica to humans through food been recognized in the United States, despite the fact that it was first isolated and identified as a human pathogen in the 1930s and as a cause of gastroenteritis in 1965 (Mossel et al., 1995). It is estimated that currently in the United States, Y. enterocolitica is involved in nearly 87,000 cases of foodborne disease annually, with an estimated case fatality rate of 0.0005 (Mead et al., 1999).

Clostridium perfringens has been associated with gastroenteritis since 1895, although it was first recognized as an important cause of foodborne disease in the 1940s (Jay, 2000). It is responsible for causing two different types of human disease: C. perfringens type A food poisoning and necrotic enteritis, the latter being the least prevalent of the two (Doyle et al., 1997; Lund et al., 2000).

Currently in the United States, C. perfringens is estimated to cause approximately 250,000 cases of foodborne illness annually, with a case fatality rate of 0.0005 (Mead et al., 1999).

The bacterium Clostridium botulinum was first isolated from food and implicated as the etiologic agent in a foodborne outbreak in 1897, although a botulism-type illness had been associated with the consumption of sausage in the early 1800s. Infant botulism was recognized in 1976 and has since become the most common form of the disease in the United States (Lund et al., 2000). Currently in the United States, it is estimated that C. botulinum is responsible for 58 foodborne disease cases annually with a case fatality rate of 0.0769 (Meadet al., 1999).

The genus Shigella has been identified as a cause of bacillary dysentery since 1898 when it was first described by Shiga during an epidemic in Japan (Murray et al., 1999). In 1900, Flexner surmised the presence of a toxin, associated with Shigella infection, which was later confirmed in 1903 by Conradi (Blaser et al., 1995). Foodborne Shigella infections are more common than waterborne infections, and it is estimated that currently in the United States, Shigella spp. are involved in nearly 90,000 cases of foodborne disease annually, with a case fatality rate of 0.0016 (ICMSF, 1996; Mead et al., 1999).

Campylobacter (formerly known as Vibrio fetus) was first isolated in culture in 1909, and in 1957 King first described the group as "related vibrios," so named because of their morphology and their association with acute enteritis in humans (Blaser et al., 1995; Doyle, 1989). Species of Campylobacter have been recognized as agents of foodborne gastroenteritis, known as campylobacteriosis or Campylobacter enteritis, since the late 1970s, and in the past 10 years Campylobacter jejuni has become well established as the most common cause of bacterial foodborne illness in the United States, resulting in 2.0 to 2.5 million cases annually and having a case fatality rate of 0.001 (Altekruse et al., 1999; Meadet al., 1999).

Listeria monocytogenes was first described during the 1910s and 1920s, and in 1924 the first reported human case involved a soldier inflicted with meningitis during World War I (Ryser and Marth, 1999). Foodborne transmission was not recognized until 1981, when the first confirmed foodborne outbreak occurred in Nova Scotia, Canada (Doyle et al., 1997). Because of its high case mortality rate, listeriosis has emerged as a major foodborne disease concern to the food industry as well as health and regulatory agencies. Current estimates suggest that L. monocytogenes is responsible for approximately 2500 cases of foodborne disease in the United States annually, with an estimated case fatality rate in excess of 0.2 (Mead et al., 1999).

Vibrio parahaemolyticus was first implicated in 1950 as the etiologic agent in an outbreak of gastroenteritis in Japan and subsequently identified in the United States in Maryland in 1971 (Janda et al., 1988). It has become one of the more common causes of Vibrio-induced diarrhea in the United States, and between 1973 and 1987 more than 20 outbreaks were reported (Doyle et al., 1997). Between 1981 and 1993, V. parahaemolyticus was responsible for 88 hospitalizations and 8 deaths in the state of Florida (Hlady and Klontz, 1996).

Another Vibrio species, V. vulnificus, also referred to as Beneckia vulnifica or the "lactose-positive Vibrio," was first studied in detail by researchers in 1976 (Janda et al., 1988). It was identified as a new species and named V. vulnificus, meaning wound inflicting, and in 1982 a second biotype (biotype 2) was discovered (Doyle et al., 1997). Currently, it is estimated to cause 47 cases of foodborne disease annually in the United States, with a case fatality rate of 0.39 (Mead et al., 1999).

0 0

Post a comment