Escherichiosis– a group of infectious diseases caused by opportunistic or pathogenic serotypes of Escherichia coli, occurring with intoxication, fever, a predominant lesion of the gastrointestinal tract, less often – urinary, biliary tract, other organs or with the development of sepsis, are observed more often in young children. Etiology and pathogenesis. Most infections are caused by Escherichia coli, less often by Escherichia fergusonii, Eschertchia hermanni and Escherichia vulneris. E. coli is a typical representative of the normal aerobic microflora of the large intestine. Pathogenic properties are controlled by plasmids and are associated with the ability of Escherichia coli to release toxins, their ability to adhere and invade the cells of the intestinal mucosa. There are no morphological differences between pathogenic and non-pathogenic Escherichia coli. Their differentiation is based on differences in the structure of surface Ag, among which are lipopolysaccharide (O), flagellar (H-) and capsular, polysaccharide Ag (K-Ag). Serovars responsible for the development of ascending urinary tract infection and extraintestinal lesions have K-Ag. According to the structure of O- and H-Ag, five main groups of diarrheagenic Escherichia are distinguished.
- The enteropathogenic group is represented by serovars 018, 026, 044, 055, 086, 011 lab, 0112, 0114, 0119, 0125ac, 0127, 0128ab, 0142, 0158, which do not produce enterotoxin and do not have invasive properties. The main causative agents of diarrhea in babies. The pathogenesis of lesions is due to bacterial adhesion to the intestinal epithelium and damage to microvilli, but not to invasion into cells. Almost all serotypes have a plasmid encoding the synthesis of the adhesive factor of enteropathogenic Escherichia coli; a small group of bacteria devoid of the adhesive factor is proposed to be separated into a separate subgroup. Bacteria express the eae gene, which causes the release of products that change the architectonics of the intestinal mucosa.
- The enteroinvasive group is represented by serovars 028ac, 029, 0112ac, 0115, 0124, 0135, 0136, 0143, 0144, 0152, 0164, 0167. They have invasive properties and cause the development of inflammatory changes in the colon mucosa. By morphological and cultural properties, they are similar to shigella and cause diarrhea resembling shigellosis. Like Shigella, enteroinvasive Escherichia coli are able to penetrate and multiply in intestinal epithelial cells, which is due to the presence of a plasmid encoding the synthesis of certain surface proteins similar (but not identical) to similar Shigella proteins (may give cross-reactions).
- The enterotoxigenic group is represented by serovars 06, 08, 011, 015,020,025,027,063, 078, 080.085, 0114, 0115, 0126.0128ac, 0139, 0148, 0153, 0159, 0166, 0153, 0159, 0166, 0167. Pathogenicity factors are villi or fimbrial factors that facilitate adhesion to the epithelium, promote colonization of the lower parts of the small intestine and determine the ability to form heat-labile and / or heat-stable enterotoxins (transmitted by bacteriophages). The low molecular weight thermostable toxin impairs the transport of Fe2+ and the exit of the liquid. The action of high-molecular heat-labile toxin is similar to that of Vibrio cholerae toxin.
- The enterohemorrhagic group is represented by serovars 026, 0111, 0157. They form cytotoxin (the formation encodes a gene carried by bacteriophage), Shiga-like toxin 1 (verotoxin 1), similar to Shigella dysentheriae toxin type 1, and Shiga-like cytotoxin 2 (verotoxin 2). Another pathogenicity factor is plasmids encoding the formation of fimbriae, which facilitate the adhesion of bacteria to the epithelium.
- Enteroadhesive Escherichia coli do not form cytotoxins, do not invade epithelial cells, and do not have the plasmid adhesion factor present in enteropathogenic Escherichia. Epidemiology
- The main mechanism of spread of diarrheagenic Escherichia is fecal-oral. Most often, a person becomes infected by eating contaminated food and water. In hospitals and closed collectives for all types, the contact route of transmission is more important. In states with a temperate climate, most infections, incl. caused by enterohemorrhagic Escherichia coli, observed in the warm season. In the tropics, where infections caused by enterotoxigenic and enteropathogenic Escherichia coli dominate, the peak incidence is observed during the rainy seasons. Since Escherichia live in the intestines of a large number of animals, it is not likely to establish a natural reservoir of pathogenic types. The fact of circulating enterohemorrhagic Escherichia coli 0157:H7 in cattle was established, which correlates with cases of hemorrhagic colitis,
- Urinary tract infections. Pathogens traditionally originate from the intestinal microflora. Bacteria penetrate into the urethra, then into the bladder, attach to the transitional epithelium and actively multiply. A certain role is played by anatomical and physiological anomalies that impede the normal evacuation of urine, for example, stenosis of the urethra or vesicoureteral reflux. Often the risk of developing lesions depends on age and gender: among newborns and babies of the first 3 months of life, they predominate in boys, in adolescence – in girls
- bacteremia. Previously, Escherichia coli was not often isolated from the blood of patients and such cases were considered as casuistry. However, they gradually replaced Gram-positive bacteria and today constitute the main cause of bacteremia in children and adults. In newborns, the source of infection traditionally remains unknown, but in 15-20% of escherichiosis are caused by manipulations on the urinary tract. Risk factors – premature birth, premature rupture of the membranes, diseases in pregnant women in the third trimester, birth trauma, hypoxia and low fetal weight. Later lesions are due to insufficient functioning of protective factors and a decrease in the content of lactoferrin and transferrin in serum (later binding iron, which promotes the reproduction of Escherichia coli). In adults, the primary sources of infection are the urinary tract (40-60%) and intestines (25-30%), in 25% of cases it is not possible to establish the source of infection. The risk of developing lesions increases in the presence of comorbidity, during invasive urological procedures or after surgical interventions.
- Meningitis. Escherichia coli is a common causative agent of meningitis in newborns (1:1,000, more often in boys). In adults, meningitis is observed infrequently (traditionally after trauma or craniotomy). In most cases, meningitis
- complications of bacteremia and develop in 10-40% of newborns with a similar pathology. The main risk group is newborns with reduced body weight (less than 2,500 g).
- Intestinal infections (coli infection)
- Enteropathogenic Escherichia cause the development of an inflammatory process mainly in the small intestine with the development of symptoms of acute intestinal infection in babies of the first year of life, incl. in newborns. Escherichia are responsible for the development of outbreaks of diarrheal diseases in obstetric institutions. Lesions are characterized by severe pain in the abdomen, vomiting, watery stools without admixture of blood. Among other dysentery, these diseases are the most severe and can last 2 weeks or more.
- Enteroinvasive Escherichia coli. Lesions (mainly distal colitis) are characterized by severe abdominal pain, profuse watery diarrhea mixed with blood. The invasiveness of microorganisms is indicated by the large number of polymorphocellular neurophils in the feces.
- Enterotoxigenic Escherichia coli cause the development of cholera-like forms of intestinal infections in adults and children.
- Enterohemorrhagic Escherichia causes bloody diarrhea (hemorrhagic colitis) with no white blood cells in the stool and signs of fever, hemolytic uremic syndrome, and thrombocytopenic purpura
- Enteroadhesive Escherichia. According to the
According to single descriptions, the clinic of lesions is similar to the symptom complex of relatively moderate shigellosis
- For all clinical variants of coli infection, an intoxication syndrome is observed, corresponding to similar manifestations in bacterial intestinal infections, its severity determines the severity of the patient’s condition.
- Urinary tract infections are a polymorphic group of lesions including asymptomatic bacteriuria, cystitis, and acute pyelonephritis. Clinically manifested by dysuria, frequent urge to urinate, pain in the lateral and lower abdomen, fever, rarely nausea and vomiting. Uropathogenic Escherichia cause more than 30% of nosocomial lesions, traditionally derived from the intestinal microflora.
- Clinically, bacteremia caused by Escherichia coli does not have specific pathognomonic features. In newborns, thermoregulation disorders, anorexia, respiratory distress syndrome, apnea, vomiting, diarrhea, jaundice, enlarged liver and spleen are most often noted. In adults – fever, confusion, convulsions, arterial hypotension, oligo- and anuria, respiratory distress syndrome.
- Meningitis. Clinical manifestations: fever, drowsiness, vomiting, diarrhea, respiratory distress syndrome, jaundice and meningeal symptoms. Mortality reaches 12% in newborns born after physiological childbirth, and 35% in newborns at risk. 20-50% of survivors have residual neurological deficits.
- Respiratory tract infections (pneumonia, pleurisy, lung abscess). Pathogens can be both pathogenic and non-pathogenic strains of Escherichia coli. Almost always they are opportunistic in nature and develop only in patients with immunodeficiency states.
- Newborns (primarily premature) and babies in the first months of life are likely to develop colibacillary sepsis with symptoms of infectious-toxic shock or multiple foci of inflammation in various organs (pneumonia, meningitis, urinary tract infection, endocarditis, arthritis, osteomyelitis, etc.). ). The prognosis of the disease, even with modern methods of treatment, is serious (mortality – 50-85%).
- Isolation of the pathogen and its toxins
- Material for the study – feces, vomit, gastric lavage, with extraintestinal localization – blood, CSF, urine, sputum. The bacteriological test is based on the determination of antigenic properties
- Identification of diarrheal types. In enterotoxic Escherichia coli, toxins are detected – thermostable on suckling mice; thermolabile on Y1 cell cultures of the adrenal glands. Enteroinvasive Escherichia is determined by the development of conjunctivitis in guinea pigs when bacteria are introduced into the conjunctival sac (Söreny test) or by the likelihood of invading HeLa and HEp-2 cells. Enterohemorrhagic Escherichia coli are identified by culture on media with sorbitol.
- Enterotoxin of enterotoxigenic Escherichia is found in the reactions of coagglutination and precipitation in agar
- Enterohemorrhagic Escherichia coli toxin is detected by ELISA
- Serological methods are traditionally not carried out due to the large number of cross-reactions with antigens of various Escherichia coli serotypes.
- Diet. Adequate increase in fluid intake.
- Etiotropic therapy – ampicillin, carbenicillin, II and III generation cephalosporins, co-trimoxazole, or a combination of one of the products with aminoglycosides
- For meningitis, ampicillin and aminoglycosides
- In renal failure, aminoglycosides are replaced by third-generation cephalosporins (for example, cefotaxime or ceftriaxone)
- In disseminated forms, antibacterial agents are administered parenterally
- The use of antibiotics does not reduce the incidence of hemolytic uremic syndrome in escherichiosis caused by Escherichia coli 0157:H7.
- Pathogenetic therapy: rehydration for dehydration, glucocorticoids and adrenomimetic agents for infectious-toxic shock, blood transfusion for anemia and thrombocytopenia, etc.
Complications. A specific complication of escherichiosis caused by enterohemorrhagic Escherichia coli is hemolytic-uremic syndrome (Gasser’s syndrome), recorded in 5-10% of patients. Symptoms: microangiopathic hemolytic anemia, thrombocytopenia and UN. The syndrome manifests itself most often by the end of the first week from the onset of the first symptoms of bowel dysfunction. In adult patients, the development of thrombotic thrombocytopenic purpura is likely.
- Patients with coli infection are subject to immediate and mandatory isolation (disseminated forms of escherichiosis pose a lesser epidemic danger)
- Sanitary control of medical personnel of children’s and intensive care units, as well as obstetric institutions
- After isolation of the sick person in the department, final disinfection is carried out.