Unraveling the Mystery of E.coli: A Fascinating Introduction

  Infectious Disease

E. coli  Are well known as the most common highly infectious facultative bacterial species in the large bowel flora and are responsible for serious complications even death. E. Coli  a gram negative bacillus, non-spore-forming, flagellated, and facultatively anaerobic bacteria with hundreds of sub types or strains. Certain strains cause diarrhea, and all can cause infection when they invade sterile sites (eg, the urinary tract). However I am only going to describe a a small portion of strains today. The sub types known as E. coli : enterotoxigenic, enteropathogenic, enteroadherent, enteroinvasive and enterohemorrhagic. E. coli bacteria are perhaps the most common bacterial diarrheal pathogen of all, however these bacteria have unique genes and each posses a distinct epidemiological pattern of disease.

Enterotoxigenic  E. coli (ETEC)

ETEC bacteria has genes that produce enterotoxins  residing on the transferable plasmids  they also produce structural pili which are important in helping them colonize mucosal surfaces of the small bowel. ETEC strains can also be differentiated by their serotypes which are distributed world wide. ETEC also have common biotype patterns. Using a series of biochemical tests such as the nucleic acid amplification test and others you can try and predict ETEC, however the best identification must come from the enterotoxins which are produced. ETEC causes acute diarrhea in children less than 2 years and have been associated with nursery outbreaks. It is also associated with 40-70 percent of travelers diarrhea. ETEC is distinguished by the identification of LT and ST genes.Antibiotics are not indicated for enterohemorrhagic E. coli infections.

Enteropathogenic  E. coli (EPEC)

EPEC can be easily identified under the microscope by the O and H antigens this serotype exhibits. EPEC has a gene that allows it to adhere to and on the brush boarder of the small intestine mucosal cells. EPEC produce severe disease in young children, but outbreaks have practically disappeared in the developed world.

Enteroadherent E. coli (EAEC)

EAEC have aggregative adherence properties. They are similar to EPEC but demonstrate the type of adhesion associated with diarrheal disease.Epidemiologically

they hey are similar to EPEC serotypes.

Enterroinvasive E. coli (EIEC)

EIEC bacteria contain large plasmids with genes that control the synthesis of invasion proteins. They also have a small array of O antigens. They are closely related to shigella bacteria and share the properties of not fermenting lactose. This bacteria is associated with outbreaks secondary to contaminated food items such as cheese and seem to be generally infrequent.

Enterohemorrhagic E. coli (EHEC)

EHEC can produce large amount of the shinga-like toxins and there are over 100 serotypes of this bacterias. The genes for the production of these toxins are located on the bacteriophages that have infected the bacterial cells. EHEC transmission is almost exclusively through processed food such as ingestion of under cooked hamburgers from a fast food restaurant. Cattle harbor the organism asymptotically in their intestinal tract and during the processing of meat fecal contamination occurs. If the meats not cooked properly the bacteria transmission will occur. Due to the different shigna toxins it produces it may manifest as bloody diarrhea.Patients suffering with serotype E. coli O157:H7 that are less than 12 years old should be hospitalized to reduce risk of community spreading and for close monitoring. About 5 to 10% of cases (mostly children < 5 years and adults > 60 years) are complicated by hemolytic-ure syndrome,which typically develops in the 2nd week of illness. Death may occur, especially in older people, with or without this complication.EHEC O157:H7 is a major food borne pathogen causing severe disease in humans worldwide. Healthy cattle are a reservoir of E. coli O157:H7, and bovine food products and fresh produce contaminated with bovine waste are the most common sources for disease outbreaks in the United States.

Symptoms of E. Coli are

          

• Severe bloody diarrhea

• Non-bloody diarrhea

• Little to no fever

• Fatigue

• Nausea

• stomach cramps

• Hemolytic uremic syndrome (HUS), a serious complication that can lead to kidney failure and death

The Infectious disease society of America recommends the use of Rifaximin, azithromycin, and ciprofloxacin, powerful antibiotics when treating E. Coli infections. Treatment is dependent on the strain, as well as the illness and extreme care must be taken to avoid the misuse of antibiotics. Antibiotics are not recommended as first-line treatment for diarrheal illness caused by E. coli  for most patients. Due to the harmful side effects and association with antibiotic resistance. If E. coli is suspected samples of blood, stool, or other clinical material must be sent for culture. If an EHEC strain is suspected, the laboratory must be notified because special culture media are required to find EHEC.

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Many gram-negative bacilli developed antibiotic resistance genes helping it in the fight, and E. coli is no exception. Recently in 2024 a hospital in china has reported a strain of E. coli  ST410 B5/H24RxC. This strain is highly infectious and grows at a faster rate thus causing more harm to organisms. All Diarrheal diseases can be prevented to a large extent by improving water purity , sanitation, washing hands , washing fruits or vegetables, and cooking meat properly which will prevent the transmission of infectious agents.

New research from The University of Texas at Austin discovered E. coli display multigenerational memory in swarming motility. When E. coli encounter different stimuli throughout the body they are able to reactivate specific neurons to produce memories that they can then pass from generation to generation.

The study found that E. coli use iron levels as a way to store this information about different behaviors that can then be activated due to certain stimuli. The fact that bacteria's exhibit behavioral and phenotypic choice due to the environment is fascinating! I mean a bacteria can display memory that's pretty cool! I found this article in a study posted by The National Academy of Sciences that states :

cellular iron levels influence the rate of antibiotic resistance , host–pathogen interactions , composition of the gut microbiome , and various other stresses in both clinical and natural settings . Frequent switching between different iron memory states would therefore be a bet-hedging strategy for maximizing survival in varied environments. Iron memory is therefore expected to be widespread in nature and to impact other physiologies. Two such other physiologies—biofilm formation and antibiotic survival—were also examined in this study. Swarming and biofilm formation are two opposite lifestyles. While low iron is a signal for swarming, high iron, a signal for biofilm formation , was positively correlated with biofilm development . Low iron was also positively correlated with increased survival to antibiotics , likely because less cellular damage is expected when iron levels are low. Antibiotics trigger production of ROS , and high iron levels would increase ROS, increasing lethality . A multigenerational iron memory would improve the survival chances of at least some individuals within the population under antibiotic stress.

I MEAN WOW! A better understanding of how bacteria develop resistance to antibiotics might help scientist get an advantage? I have so many questions.....I probably shouldn't be this excited about studying bacteria's but what can I say I am kind of Nerding out here.

Written by

Holly White

Try guessing the answer then click on the drop down to see if you got it correct!

1) Ingested E. coli O157:H7 produces high levels of toxins in the large intestine. These toxins are closely related to those produced by which of the following organisms?

A. Entamoeba histolytica

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B.Clostridium difficile

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C.Giardia lamblia

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D.Shigella dysenteriae

 If you Answered : D : Shigella dysenteriae. you are correct 

 After ingestion, E coli O157:H7 and similar STEC (Shiga toxin–producing E. coli) serotypes produce high levels of various toxins in the large intestine; these toxins are closely related to the potent cytotoxins produced by Shigella dysenteriae type 1. A rapid stool assay for Shiga toxin or, when available, a test for the gene that encodes the toxin may help identify EHEC. 

2) What percentage of patients with an EHEC infection develop hemolytic-uremic syndrome?

A.< 1>

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B. About 5 %

 IF you choose B you’re CORRECT !!  

Answer: B: About 5% of cases (mostly children < 5 yr and adults > 60 yr) are complicated by hemolytic-uremic syndrome, which typically develops in the 2nd wk of illness. 

C.About 10%

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D.About 15%

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3)Among the steps that can be taken to prevent transmission of E. coli O157:H7 and STEC, which of the following is often overlooked?

A. Correct disposal of the stool of infected people

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B. Careful hand washing with soap

Answer: B. Careful hand washing with soap for the appropriate length of time. This step is often abbreviated by people of all ages, including health care professionals. Alcohol hand wipes Choices A, C, and D are other important preventive actions. 

C. Thorough cooking of beef

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D. Isolation of infected children in public settings

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