by Laura Cuppini
In the typical form, hemolytic-uremic syndrome is a complication of an intestinal infection caused by particular strains of E. coli, which produce a potent toxin
Hemolytic-uremic syndrome (HUS), a disease of small MM which for years he has been in a vegetative state due to a piece of cheese made with raw milk, is a rare disease which however represents the most important cause of acute renal failure in childhood, particularly in the first years of life. In its typical form (70-80% of cases) it is caused by an intestinal infection caused by particular strains of Escherichia coli (E. coli), producers of a powerful toxin, called shiga-toxin (or verocytotoxin), which enters the blood circulation and mainly affects the kidney. The bacterial strain is called shiga toxin-producing E. coli (or Stec). The atypical forms of Seu are generally attributable to genetic factors and therefore can affect people of the same family. Finally, there are rare cases in which HUS develops following a systemic infection with Streptococcus pneumoniae (pneumococcus).
Symptoms of HUS
In Italy, on average, 40-50 cases of HUS are recorded in children under the age of 15 every year; the age group most affected is between 0 and 4 years. The main symptoms of HUS are hemolytic anemia (fragmented red blood cells and reduced hemoglobin), thrombocytopenia (reduced number of platelets) and acute renal failure of varying degrees. 25-30% of patients also risk neurological complications. HUS can be fatal in 3-5% of cases, and a similar percentage of patients develop chronic renal failure, requiring lifelong dialysis.
The risks of raw milk
THE. coli is a very widespread and not always “bad” bacterium. In fact, it lives as a commensal in many organisms, including the human body, contributing to the performance of various functions. Unfortunately, there are also very dangerous strains of E. coli, such as Stec. The latter are normally present in the intestine of ruminants, in particular cattle, which however are asymptomatic carriers. Their feces can, therefore, contaminate meat and milk during slaughter and milking. If the meat is contaminated and is eaten undercooked, the germ can be transmitted to humans. In the case of milk, only raw (unpasteurized) milk can be a vehicle for infection. Person-to-person transmission is possible via the fecal-oral route. Furthermore, it can occur through direct contact with animals or with water and plants contaminated by faeces (for example through fertilizers produced with the latter). The incubation period of Stec infection (time between ingestion of the bacterium and the onset of symptoms) is between 1 and 5 days. Stec infection is not very rare, but only in 10% of cases does it evolve into hemolytic-uremic syndrome (HUS).
Hygiene rules
The advice to prevent Seu is to avoid the consumption of undercooked meat, especially minced meat (burgers, tartare) or carpaccio, and raw unpasteurized milk and derivatives. Furthermore, contamination of ready-to-eat foods (such as salads) with raw meat must be avoided, for example by using the same knife or cutting board. As with other intestinal infections, people with diarrhea, especially children, should be isolated from the community until they recover. In the event of an intestinal Stec infection, the patient’s family members must observe strict hygiene rules: normal environmental cleaning and personal hygiene operations (in particular hand washing) are sufficient to avoid the spread of the infection. It is also a good idea to wash your hands thoroughly after visiting a farm or petting animals.
How to reach the diagnosis
Generally, the first symptoms of the disease are diarrhea, sometimes with the presence of blood, vomiting and intense abdominal pain, which are followed by hemolytic anemia, thrombocytopenia and renal failure (with oliguria, i.e. poor urine production, or anuria, i.e. absent production of urine): the latter involves in most cases the use of dialysis, temporary or – in the worst cases – permanent. The diagnosis of Seu is based on clinical symptoms, blood tests and kidney function tests. In more serious cases, neurological manifestations may appear such as drowsiness, confusion, dulling of the senses, strabismus and convulsions, coma. Fever is almost never present or in any case does not normally exceed 38°. When cases of Seu occur in schools, especially nursery schools and nurseries, particular attention must be paid to prevent the infection from being transmitted to other children. Person-to-person contagion is frequent and strict measures must be observed: personal hygiene, frequent hand washing, changing clothes that have come into contact with faeces, disinfection of surfaces. In the case of Seu due to Stec infection, it is very important that the sick child’s family members undergo a stool test to look for bacteria, especially if they have suffered from even mild gastrointestinal symptoms (diarrhoea, abdominal pain, vomiting).
Damage to kidneys and brain
But how does the infection happen? Stec bacteria, once they enter the body, colonize the intestinal mucosa and release shiga toxin. This binds to specific receptors (Gb3) present on the intestinal villi, inducing their destruction, which in turn favors the entry of the toxin into the circulation. At that point the toxin reaches its target tissue, namely the endothelia of the intestine and kidneys. The endothelium is the tissue that lines the inside of blood vessels. Since the kidney and brain are organs rich in endothelium, they risk very serious damage during the acute phase of the infection. The severity of intestinal symptoms depends on the level of diffusion of the toxin and is very variable: from diarrhea to hemorrhagic colitis, characterized by severe abdominal pain and abundant blood loss in the feces.
Contact specialized centres
The course of HUS can be very rapid and therefore it is important to immediately contact specialized centers capable of providing adequate therapy. During the phase of renal failure it is essential to be admitted to a nephrology center which can guarantee dialysis and possibly plasmapheresis (separation of the liquid component from the corpuscular component of the blood). It should be underlined that antibiotic therapy is not necessary (as in the vast majority of infectious diarrheas) and can actually favor the release of the toxin into the intestine by the Stec bacteria. However, it is advisable to monitor the blood parameters and renal function of patients with suspected Stec intestinal infection, as they are at risk of developing hemolytic-uremic syndrome.
March 17, 2024
© ALL RIGHTS RESERVED