Escherichia Coli (E. Coli) Infection – Transmission, Symptoms And Diagnosis
Escherichia coli (abbreviated E. coli) is a bacterium that lives in the intestinal tract of man and animals. All individuals have it (starts to populate the intestinal lumen 40 hours after birth) and is part of the commensal flora (bacteria that live in the body of a healthy person but does not cause any disease). Newborn’s body comes in contact with the bacteria through water, foods or hospital staff.
Although most strains of E. coli are not dangerous, there are exceptions, such as serotype O 157: H7, which is incriminated in the occurrence of serious food poisoning, anemia or kidney failure, or strains that may be etiologic agents of diarrhea and bleeding, enterohaemorrhagic E. coli (EHEC). Some strains of E. coli are incriminated in the occurrence of urinary tract infections. The bacteria is a comensal while it does not posses virulence factors (genetic changes). It is believed that this bacterium is transmitted mainly fecal-oral due to poor hygiene.
E. coli is a Gram-negative bacteria , that can not hold a special purple dye inside the cell. This test is very important, because on this basis, bacteria are classified into two groups, depending on the cell wall. E. coli can live in aerobic environments (with oxigen) and anaerobic environments (without oxygen) therefore the bacillus is considered to be facultative anaerobic. Some strains of E. coli have increased mobilitity.
Contact with E. coli occurs early in life of the individual, since the first days of life. E. coli can be contracted from outside if you come in contact with biological products that contain faeces. For this reason, the presence of E. coli is an important factor in determining the fecal contamination of soil, water and food.
Food Contamination With E. coli
Food can be contaminated with E. coli during cooking and can cause serious infections in humans if these products are not cooked properly. For example, if you do not cook the meat to at least 70 degrees, bacteria will not be destroyed, and the risk of food poisoning exists. One of the most common forms of infection is consumption of insufficiently cooked meat. In addition, any food that comes in contact with the contaminated meat will be contaminated as well.
Foods that may be contaminated with E. coli
Raw milk or dairy products – can spread bacteria from the cow’s udder in the milk. To avoid consumption of potentially infected milk, pasteurized milk consumption is recommended. During the process of pasteurization the product is brought to high temperatures that can destroy potentially pathogenic flora. Pasteurization does not destroy all microorganisms, but only those that can cause diseases. Fruits and raw vegetables which are not washed properly, and are eaten directly after being purchased, may be contaminated with bacteria. Some fruits and vegetables can also be pasteurized, and if possible, experts recommend this option, including for natural juices. The list of foods that can be pasteurized include: nuts, honey, cheese, eggs, cream, soy sauce, wine, water, vinegar, juices, beer and canned products.
Water contamination with E. coli
Sometimes, in conditions of non-compliance to hygiene measures animal feces get into contact with natural waters like: lakes, rivers, water reservoirs. Sometimes even water pools can be infected by ingestion or aspiration the body comes in contact with potentially pathogenic strains. Major E. coli outbreaks are determined by contamination of larger water reservoirs, in the absence of effective systems of chlorination and disinfection
Direct transmission from person to person of E. coli
E. coli can spread from person to person, especially when basic standards of hygiene are not met, when hands are not washed after going to the toilet. E. coli can contaminate objects, and usually people are not carefu,l and do not wash their hands and thus can get in contact with the skin of another host, thus indirectly transmitting infection.
E.Coli Infection Symptoms
Symptoms of E. coli infection vary significantly depending on the location of infection, host age and immune status at the time (which allows bacteria to multiply in the body). In some cases individuals are only carriers of pathogenic strains and did not develop infection – remain asymptomatic, but can transmit E. Coli to other persons. Clinical stage begins 3-4 days after contracting E. coli. Most patients develop a gastrointestinal infection, because the fecal-oral trasmission is the most common. In this case the infection is manifested by:
- Severe stomach pain, abdominal cramps and spontaneous tenderness to palpation of the abdomen ;
- Diarrhea, watery at first, but may become bloody (depending on the pathogenic strain);
- Nausea and vomiting
Children frequently develop infections with E. coli serotype O157: H7 (E. coli enterohaemorrhagic) compared with adults. This strain is particularly dangerous because it has the ability to stimulate the formation of potentially lethal toxins. Serotype O157: H7 can cause life-threatening complications and can be fatal, especially in small children and elderly persons. The most dangerous complications beeing haemolytic uraemic syndrome and acute renal failure.
In some situations E. coli may end up contaminating the peritoneal cavity due to a perforated ulcer, perforated appendix, or even a failed suregery leading to bacterial peritonitis, which can be fatal without prompt treatment.
The clinical picture of patients with symptomatic infection with E. coli is not specific to this bacteria, there are many conditions that can cause the same spectrum of symptoms. Diagnosis of infection with E. coli can be relatively difficult to establish even to suspect, because bacterial infections that cause diarrhea are accompanied by high fever. In afebrile patients or very low fever, the doctor may overlook the possibility that the symptoms could be of infectious nature.
Symptoms induced by infection with common strains of E. coli occurred in a patient with competent immune system, which may limit the growth of E. Coli, will imporve and even disappear in a week without complication. In such cases, patients recover without receiving special treatment, some even without seeing the doctor for this problem. But if the bacteria is more aggressive, complications can occur, mainly due to fluid and electrolyte imbalances (presence of diarrhea) and acute renal failure. It begins at 2-14 days after infection. If complications arise, the patient’s general condition will worsen and the clinical picture may include:
- Cool, pale skin
- Temporo-spatial confusion
E.coli Infection Diagnosis
Investigation of patients who present to the infirmary complaining of explosive diarrhea with with onset of a few days and impaired general condition, is started with general history and physical examination. Patient history is the baseline of expert advice. Your doctor will find more information about symptoms, risk factors, lifestyle, compliance with basic hygiene measures, personal history and your close relatives (especially family members).
The main questions that the physician may address the patient:
- When the diarrhea started, how long it took and how frequent is it?
- Is there blood, mucus or pus in the stool or is it just watery?
- Have you noticed chills or fever?
- Abdominal cramps, nausea, vomiting?
- Did the general condition change? Did you encounter unusual fatigue, irritability?
- Have you felt dizzy?
The doctor may suspect an infection caused by E. coli if the following risk factors exist:
- The patient came from a care institution, elderly center, day care
- Consumption of inadequately cooked foods, restaurant meals (especially exotic restaurants)
- Semi-raw meat consumption, unpasteurized milk, unpasteurized juices
- Contact with other patients who have recently had diarrhea
- Recent trips in areas with poor hygiene, non-potable water
- Recent administration of antibiotics.
History is followed by general physical examination during which the doctor will:
- Take the patient’s temperature
- Measure blood pressure and pulse
- Inspect skin, skin analysis by creating a consistent skin fold
- Abdomen palpation
- Perform a digital rectal exam to determine precisely whether or not traces of blood exist in the stool.
If an infectious diarrhea is suspected, samples of diarrheal stools, will be analyzed microbiologically. Special stain are made, and the sample will be placed in different culture mediums to determines the type of bacteria that is responsible for the symptoms. Because it is possible that the bacteria to be removed only during the onset of symptoms, the best option is that the samples are collected quickly. For this reason it is recommended that patients present to the doctor as soon as possible, especially if diarrhea contains traces of blood.
There are other more laborious and expensive methods to diagnose an infection with E. coli (immunoassay methods, immunofluorescent), but in general microbiological analysis provides the correct diagnosis. After the diagnosis of infection with E. coli has been established, some patients will be monitored more closely. These are groups at risk, very young or very elderly patients (extreme ages), those with compromised immune status, and all patients who are infected with highly virulent strains, known for their ability to cause complications. Monitoring involves periodic collection of urine samples, blood salmples and other tests which show the overall health status.