What is Escherichiosis?
Escherichiosis (coli infection) – acute infectious diseases with fecal-oral transmission mechanism; the predominant lesion of the gastrointestinal tract with the development of enteritis or enterocolitis is characteristic, in rare cases, generalized forms with extraintestinal manifestations.
Brief historical information
Bacteria got their name in honor of the German pediatrician T. Escherich, who first discovered Escherichia coli (1886). Escherichia coli is a permanent inhabitant of the human intestines. The ability of E. coli to cause gastrointestinal lesions was experimentally proved by G.N. Gabrichevsky (1894) and clinically confirmed A. Adam (1922). Serological analysis conducted in the 40s by F. Kauffmann proved the difference in the antigenic structure of pathogenic and non-pathogenic E. coli, which formed the basis of their modern microbiological classification.
Causes of Escherichiosis
The causative agents are diarrheagenic (as defined by WHO) E. coli serovars, represented by mobile gram-negative bacilli of the genus Escherichia of the Enterobacteriaceae family. Morphologically, serovars are indistinguishable from each other. They grow well on ordinary nutrient media. Stable in the environment, stored for months in soil, water, feces. They tolerate drying well, are able to reproduce in foods, especially in milk. They die quickly when boiled and disinfected. In E. coli, somatic (O-antigen), capsular (K-antigen) and flagellar (H-antigen) antigens are isolated. Currently, about 170 antigenic variants of E. coli are known; more than 80 of them cause coli infection. Diarrheagenic serovars of E. coli are divided into 5 groups:
- enteropathogenic (EPKP);
- enterotoxigenic (ETKP);
- enteroinvasive (EICP);
- enterohemorrhagic (EHEC);
- enteroadhesive (EAKP).
In the materials of the WHO (1989), serogroups 071, 092, 0166, 0169 are also indicated in the number of ETCHs.
- Enteropathogenic E. coli includes about 15 serogroups and 29 serovars.
- Enteroinvasive E. coli includes about 9 serogroups and 13 serovars. Of greatest importance are strains 0124 and 0151.
- Enterotoxigenic E. coli includes 17 serogroups and 16 serovars.
- Enterohemorrhagic E. coli include serogroups 0157, 026, 0111, 0145.
- Enteroadhesive E. coli is not completely differentiated. They differ in their ability to quickly attach to intestinal epithelium.
The reservoir and source of infection is a person, patient, or carrier. Patients present a great epidemic danger; among them, the most dangerous are patients with Escherichiosis caused by EPEC and EICP, and the least dangerous are patients with Escherichiosis due to EECP, EHEC and EECP. The period of contagiousness of the source depends on the properties of the pathogen. With escherichiosis caused by ETEC and EHEC, the patient is infected only in the first days of the disease, with diseases caused by EECP and EPTK, 1-2 weeks (sometimes up to 3 weeks). Carriers excrete the pathogen for a short time, and children – for a longer time.
The transmission mechanism is fecal-oral, transmission routes are food, water and household. According to WHO, infection with ETEC and EICP is more likely to occur through the food route, and EPEC through the household. Among food products, dairy products (often cottage cheese), prepared meat dishes, drinks (compote, kvass, etc.), salads from boiled vegetables predominate. In children’s groups, as well as in hospital conditions, the pathogen can spread through care items, toys, hands of mothers and staff. With enterohemorrhagic escherichiosis, people become infected when they eat insufficiently thermally processed meat, as well as raw milk. Outbreaks of diseases associated with the use of hamburgers are described. Waterway transmission of Escherichiosis is less common; dangerously intense pollution of open reservoirs as a result of the discharge of uncontaminated domestic and wastewater, especially from infectious diseases hospitals. The natural susceptibility to Escherichiosis is quite high, but it varies in different age groups of the population. The transferred disease leaves unstable group-specific immunity.
The main epidemiological signs
The disease is ubiquitous; The epidemiological features of Escherichiosis caused by different serovars can vary significantly. EPKP – pathogens of enterocolitis in children of the first year of life. The incidence is usually recorded in the form of outbreaks in DDU and hospitals. Pathogens are transmitted, as a rule, in a contact-everyday way – through the hands of adults (puerperas and staff) and various objects (spatulas, thermometers, etc.). Foodborne outbreaks of infection are also known, mainly when artificially feeding young children. EIKP – causative agents of dysentery-like diseases in children older than 1 year and adults. Patients usually excrete bacteria within 1 week; the pathogen is transmitted through water and food. The epidemic process of dysentery-like escherichiosis occurs, as a rule, in the form of group diseases and outbreaks with the use of contaminated water and food. Diseases are distinguished by summer-autumn seasonality; they are more often registered in developing countries. ETKP – causative agents of cholera-like diseases in children under the age of 2 years and adults. These pathogens are widespread in countries with a hot climate and poor sanitary conditions. More often sporadic, less often group diseases are recorded. In the Russian Federation, ETCHs are rarely isolated, more often when deciphering “imported” cases of diseases that make up the main group of the so-called “travelers diarrhea”. Bacteria are isolated from patients for 7-10 days. Infection occurs through water and food. Contact-household transmission is unlikely, since the dose of the pathogen is important for infection. The epidemiology of Escherichiosis caused by EHEC is not well understood. It is known that diseases prevail among children over a year of age and adults, and outbreaks in nursing homes are also reported.It has been established that the natural biotope EGKP 0157: H7 is the intestines of cattle. An important influence on the incidence of escherichiosis is exerted by the sanitary and hygienic conditions of people’s lives (home improvement, provision of benign drinking water and food products, etc.). A common symptom of all forms of Escherichiosis is the lack of a relationship between morbidity and population groups by profession or occupation.
Pathogenesis during Escherichiosis
The mechanisms of the development of diseases depend on the affiliation of diarrheagenic Escherichia to specific groups. EPPs primarily cause disease in young children with damage to the predominantly small intestine. The pathogenesis of lesions is due to the adhesion of bacteria to the intestinal epithelium and damage to microvilli, but not invasion of the cells. The pathogenicity factors of ETEC are drank, or fimbrial, factors that facilitate adhesion to the epithelium and promote colonization of the lower parts of the small intestine, as well as determining the ability to toxin formation. Heat-labile, thermostable enterotoxin or both of these toxins are isolated. The effect of a high molecular weight labile toxin is similar to that of a cholera vibrio toxin [activation of the adenylate cyclase system with the formation of cyclic adenosine 3 ‘, 5’-monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP)]. These pathogens often become the etiological factor of secretory diarrhea in adults and children. EICPs, like shigella, penetrate and multiply in intestinal epithelial cells. Like shigella, they are motionless and often unable to ferment lactose (DNA homology analysis shows that EICPs are shigella, but because of the medical significance of the latter they were left in the genus Escherichia). Damage to the epithelium increases the absorption of bacterial endotoxin into the blood. The leading role in the pathogenesis of Escherichiosis due to EHECs is played by shigapodobny toxins of two types. Under their action, local necrotic lesions and hemorrhages develop. Penetrating into the blood, they enhance the toxic effect of the LPS complex, which can lead to the development of hemolytic-uremic syndrome and multiple organ failure (DIC, ITS, vascular endothelial damage in the glomeruli of the kidneys and acute renal failure).
Symptoms of Escherichiosis
The clinical classification of Escherichiosis divides them into the following groups:
- By etiological signs: o enteropathogenic; o enterotoxigenic; o enteroinvasive; o enterohemorrhagic.
- According to the form of the disease: o gastroenteric; o enterocolitic; o gastroenterocolitic; o generalized (coli sepsis, meningitis, pyelonephritis, cholecystitis).
- By severity of the course: o lungs; o moderate; o heavy.
EPI class I cause the disease mainly in young children. The incubation period lasts several days. The main clinical manifestations are diarrhea, vomiting, severe intoxication syndrome and rapid dehydration. Perhaps the development of a septic process. EPI class II affect adults; in these cases, the clinical picture of the disease often resembles salmonellosis. EICPs cause dysentery-like Escherichiosis, clinically similar to shigellosis. The incubation period lasts 1-3 days, the disease begins acutely with moderate manifestations of intoxication syndrome – headache, weakness, fever from subfebrile to high, chills. Cramping abdominal pains soon join, diarrhea occurs, pathological impurities are possible in feces – mucus and even blood streaks. In some patients, tenesmus and false desires are possible. On palpation of the abdomen, pain along the colon and often in the umbilical region is determined. The disease proceeds in a mild, erased, sometimes moderate form for several days. The clinical picture of diseases caused by ETEC is similar to salmonellosis, IPT, and mild cholera. The incubation period is 1-2 days. Against the background of moderate signs of intoxication and most often normal body temperature, cramping pains occur in the epigastric and umbilical regions, which can sometimes be absent. Nausea builds up, repeated vomiting and profuse loose stools of an enteric nature appear. These phenomena lead to the development of moderate dehydration, sometimes oliguria. The disease is often referred to as “travelers’ diarrhea” that occurs in people visiting tropical countries. In the conditions of the tropics in the clinical manifestations of the disease, the development of fever, chills, myalgia and arthralgia, severe dehydration is possible. EHECs affect mainly children. The disease is manifested by moderate intoxication with subfebrile body temperature, nausea and vomiting, diarrhea of a watery nature. In more severe cases, in the dynamics of the disease on the 3-4th day of the disease, intense cramping abdominal pain develops, stool becomes more frequent, an admixture of blood appears in the feces, sometimes in significant amounts. The stool acquires a fecal-free bloody or blood-purulent character (clinical manifestations of catarrhal-hemorrhagic or fibrinous-ulcerative colitis). The clinical picture of the disease in most cases stops on its own within 1 week. However, in some patients with severe course (mainly in children under 5 years of age) after the end of diarrhea on the 7-10th day of the disease, hemolytic-uremic syndrome may develop. In this condition, a combination of acute renal failure with hemolytic anemia and thrombocytopenia is characteristic. Often cerebral disorders join: muscle cramps of the extremities, muscle rigidity, hemiparesis, stupor and coma. In such cases, mortality can reach 5%.
In most cases, Escherichiosis proceeds practically without complications. However, in diseases caused by EHEC, the development of severe renal complications, hemorrhagic purpura, cerebral disorders is possible. In the countries of the tropical zone, in patients with polyparasitosis and protein starvation, Escherichiosis often acquire a severe course with the development of ITS, dehydration of III-IV degrees, and acute renal failure.
Diagnosis of Escherichiosis
Escherichiosis differentiate from foodborne toxicoinfections, salmonellosis, shigellosis, cholera, campylobacteriosis and viral gastroenteritis. Due to the pronounced clinical similarity of Escherichiosis caused by various categories of diarrheagenic E. coli with one or another of the listed diseases, the results of laboratory studies are crucial.
The basis is the allocation of pathogens (crops of feces and vomit, and in generalized forms – blood, cerebrospinal fluid, urine, bile). Serological methods are rarely used in practice, since they do not give reliable diagnostic results due to the similarity of pathogen antigens with other Escherichia. In the laboratory diagnosis of Escherichiosis caused by EHEC, it is promising to put into practice methods for determining bacterial toxins in the feces of patients. In severe cases, signs of hemolytic anemia, an increase in the content of urea and creatinine are detected in the blood. Proteinuria, hematuria, leukocyturia are noted.
Hospitalization of patients is carried out according to clinical and epidemiological indications. The principles of pathogenetic treatment are determined by the types of pathogens and are similar to those for salmonellosis, shigellosis, and cholera. Prescribe a sparing diet (table No. 4, after the termination of diarrhea – table No. 13). With severe intoxication and dehydration, polyionic crystalloid solutions are prescribed orally or intravenously, and in the absence of dehydration, colloidal solutions (reopoliglyukin, hemodes, etc.) are prescribed. It is recommended to add nitrofurans (furazolidone 0.1 g 4 times a day), and in severe cases caused by EICP, fluoroquinolones (ciprofloxacin 0.5 g 2 times a day, pefloxacin 400 mg 2 times a day) 5-7 days course. In cases of Escherichiosis caused by EPEC in children, the appointment of cotrimoxazole and antibiotics is recommended. For the treatment of generalized forms (sepsis, meningitis, pyelonephritis, cholecystitis), cephalosporins of II and III generations are used. With a prolonged course of diseases, eubiotics and enzymes are indicated. Currently, antitoxic therapy (serum, extracorporeal sorption of antibodies) is being introduced to treat Escherichiosis caused by EHEC.
Prevention of Escherichiosis
Preventive and anti-epidemic measures for Escherichiosis should be based on materials of constant monitoring of the manifestations of the epidemic process and data from microbiological studies. Caution is especially important in case of group diseases of diarrhea in hospital conditions organized by groups of children and adults, where it is necessary to carry out laboratory diagnostics and establish the species of Escherichia.
Prevention of escherichiosis is based on strict observance of sanitary and hygienic requirements at public catering and water supply facilities. Given the leading role of the food-borne transmission of infection, measures aimed at interrupting it are of extreme importance. Particular attention should be paid to the prevention of infections and strict adherence to the sanitary and anti-epidemic regime in DDU, maternity hospitals and hospital facilities. It is necessary to use individual sterile diapers, treat hands with disinfectant solutions after working with each child, disinfect dishes, pasteurize or boil milk, milk mixtures and food additives. Preventively examined for escherichiosis of pregnant women before childbirth and women in childbirth. Hygienic skills should be instilled in mothers and staff caring for babies, as well as older children, including in institutions of public education and training.
Patients with Escherichiosis are hospitalized for clinical and epidemiological reasons. They are discharged from the hospital after clinical recovery and negative results of a 3-fold bacteriological study of feces, carried out 2 days after the end of etiotropic treatment with an interval of 1-2 days, after which adults are allowed to work in the specialty, and children are sent to child care facilities without additional inspection or quarantine. Other contingents are prescribed no earlier than 3 days after normalization of stool, body temperature and obtaining a negative result of bacteriological examination of feces. Children who communicate with a patient with Escherichiosis at the place of residence are admitted to child care facilities after separation from the patient and three times negative results of bacteriological examination. When diseases occur in children’s and obstetric institutions, the intake of incoming children and women in labor is stopped. Personnel, mothers and children who interacted with patients, as well as children discharged home shortly before the onset of the disease, are subjected to 3-fold bacteriological examination. Individuals with a positive test result are isolated. Among food workers and enterprises equivalent to them, they take the same measures as for shigellosis. Young children and adults belonging to maternity groups (persons involved in the preparation, distribution and storage of food products, carers at the childcare center, medical workers, etc.) are subject to follow-up for 1 month after clinical recovery with bacteriological examination at the end of the term.