Escherichia coli (E. coli) Research Paper

Introduction

The Escherichia coli are bacteria that are commonly found in the human and animal digestive tract (Standridge, 2008). Most of them live in a symbiotic relationship with the humans or animals and are part of the essential microflora within the system. They are among the most studies microorganisms on earth, their discovery dating back in the 1980s (Law, 2000). This paper discusses the history of E. coli with particular consideration being accorded to E. coli O157: H7, a pathogenic strain of the E. coli bacteria. The epidemiology of the bacteria is also discussed as well as its disease causation in humans, prevention, and control.

History of E. coli

The Escherichia coli is a group of Gram-negative bacteria that are facultative anaerobes that were first isolated and described by Theodor, a German bacteriologist, Escherich in 1985 (Law, 2000). Initially, the E. coli were referred to as Bacterium coli but their name changed to E. coli in honor of the discoverer, Dr. Escherich. It was Dr. Escherich who also associated some infant diarrhea as well as child gastroenteritis to the colonization of the digestive system by E. coli (Law, 2000).  Most of the strains of E. coli are harmless and form part of the normal microflora in the digestive systems of humans and animals. With time, however, some E. coli strains turned out to be disease causing microorganisms whose pathogenicity was acquired through virulence factors (Taylor et al., 2013). Virulence factors enhancing disease causation in humans were attributed to plasmids, transposons, pathogenicity islands and bacteriophages. Later on, E. coli were classified into various strains by their mechanisms of pathogenicity, virulence factors or clinical symptoms. Such classifications were recognized as serogroups (Wileman et al., 2011). Ever since E. coli have become some of the most studied bacterial microorganisms with more than 700 serogroups being isolated. Various serotypes of E. coli have been distinguished through the identification of the O and H antigens present in the bacteria as well as the presence or absence of flagella (Law, 2000).

Epidemiology of E. coli: A Short Case in the U.S.

  1. coli O157: H7 is one of the commonest pathogenic E. coli bacteria that have bed characterized, with its first discovery being dated back in 1982 (Wileman et al., 2011). Its discovery was linked to an outbreak of hemorrhagic colitis as well as the Hemolytic Uremic Syndrome in the United States. E. coli O157: H7 became widely recognized as a serious cause of disease later in 1993 during an incidence when a multistate outbreak occurred being associated with undercooked ground beef patties that were sold from a certain fast food restaurant chain. Most clinical laboratories engaged in the examination of stool specimens of victims, looking for E. coli O157 (Standridge, 2008). The infection with E. cli O157 became nationally notifiable in 1994 while reporting among 48 states became mandatory in 2000. E. coli has become a popular cause of childhood acute renal failure with approximately 73,480 cases being reported annual in the U.S accompanied by a hospitalization rate of about 2,168 people out of which 61 die every year (Taylor et al., 2013).

In most cases, the transmission of E. coli O157: H7 is linked to foods of the bovine origin, especially considering the fact that most of the first cases of infections related to enterohemorrhagic E. coli (EHEC) were related to consumption of beef products (Wileman et al., 2011). Other food sources have also been cited as important in the transmission chain, some of which include apple juices and cider, milk, cheese, yogurt, lettuce, tomatoes, soybeans, fruits and vegetables among other food products. Apparently, any food crop that is grown in proximity to herds of cattle acts as a possible contaminant and can transmit the pathogen to humans (Espina, Somolinos, Pagán, & García-Gonzalo, 2010). Transmission may also be through consumption of contaminated water in lakes, ponds, and other reservoirs, eliciting gross outbreaks of E. coli O157: H7 related diseases. Transmission of such diseases may also occur through the fecal-oral route from person to person, especially amongst children in day care facilities (Taylor et al., 2013).

Disease in Humans

Large regions of North America, Europe, and Japan have experienced a great challenge in tackling infections caused by E. coli, especially those caused by pathogenic strains such as O157: H7. Despite the fact that the diseases caused in humans by such strains of E. coli are less in number compared to diseases caused by other enteric pathogens such as the Salmonella and Campylobacter spp., more hospitalizations are reported with cases of E. coli O157: H7 infections. Moreover, more fatalities are associated with pathogenic E. coli infections as compared to the fatalities caused by other enteric bacterial infections (Taylor et al., 2013). Human infections with E. coli present in the form of asymptomatic cases to more serious cases that may lead to detrimental effects. In most cases, the pathogenic E. coli infections begin with loose diarrhea without blood and sometimes resolve without medical attention while others end up in serious complications (Wileman et al., 2011). In the serious complications of the diseases, the patient ends up with bloody diarrhea or hemorrhagic colitis, incidences that may result in about one to three days following infection. In more serious cases, about five to ten percent of the reported cases progress to life-threatening sequelae, Hemolytic Uremic Syndrome or in some cases suffer from thrombocytopenic purpura (TPP) (Espina et al., 2010). In fact, the commonest case of HUS in the United States is E. coli O157: H7 while both children and people with advanced ages stand a higher risk of suffering from severe symptoms such as HUS.

Prevention and Control

If the disease conditions caused by infections with pathogenic E. coli do not develop complications, they may resolve on their own within a period of about ten days (Wileman et al., 2011). Antibiotics that were initially used are currently contraindicated due to the potential of increasing resistance, aggravated kidney complications, and an alteration of the course of the disease (Law, 2000). The patients that eventually develop HUS are advised to undergo a kidney dialysis or consider a blood transfusion. Effective treatment of such diseases can be achieved through a timely diagnosis of the infection, especially when a bloody diarrhea is noticed which most of the time precedes HUS. 

In preventing the incidence of E. coli infections such as those caused by E. coli O157: H7, it is advisable to maintain good hygiene and sanitation within the social surroundings. Washing of fruits and vegetables before consumption also prevents the incidence while properly cooking meat is advisable, if possible cooking it at temperatures above 70oC.Proper and hygienic slaughtering procedures should be practiced to prevent fecal contamination (Wileman et al., 2011). Since the bacteria living in host cattle does not cause infections to the cattle, it is not advisable to vaccinate the cattle. After all, the cattle will never elicit any immune response if no disease is caused by the bacteria. Again, all patients with bloody diarrhea need to be tested for Enterohemorrhagic E. coli for early diagnosis and treatment of human diseases (Espina et al., 2010). 

Conclusion

E coli are among the most widely studied bacteria in the world. They were discovered by Theodor Escherich in 1985, and while some are harmless, others have the potential to cause life-threatening disease conditions. Such diseases include bloody diarrhea, HUS, and TPP, which can be prevented through practicing high levels of hygiene and sanitation as well as proper cooking of meat and beef products.

 

References

Espina, L., Somolinos, M., Pagán, R., & García-Gonzalo, D. (2010). Effect of citral on the thermal inactivation of Escherichia coli O157: H7 in citrate phosphate buffer and apple juice. Journal of Food Protection, 73(12), 2189-96.

Law, D. (2000). The history and evolution of Escherichia coli O157 and other shiga Toxin-producing E. coli. World Journal of Microbiology and Biotechnology, 16(8-9), 701-709.

Standridge, J. (2008). E. coli as a public health indicator of drinking water quality. American Water Works Association. Journal, 100(2), 65-75, 10.

Taylor, E. V., Nguyen, T. A., Machesky, K. D., Koch, E., Sotir, M. J., Bohm, S. R., & Williams, I. (2013). Multistate outbreak of Escherichia coli O145 infections associated with romaine lettuce consumption, 2010. Journal of Food Protection, 76(6), 939-44.

Wileman, B. W., Thomson, D. U., Olson, K. C., Jaeger, J. R., Pacheco, L. A., Bolte, J., & Straub, D. (2011). Escherichia coli O157: H7 shedding in vaccinated beef calves born to cows vaccinated prepartum with Escherichia coli O157: H7 SRP vaccine. Journal of Food Protection, 74(10), 1599-604.

 

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