3 Typhoid Antigen

How to Diagnose Prevent and Treat Typhoid Antigen?

Meaning of Typhoid: Salmonella typhi is the causative agent of typhoid and is a serotype of Salmonella enterica. The route of transmission is the fecal-oral route, which is highly contagious. The main symptoms of human infection are high fever, which can reach 39 to 40 ° C. Other symptoms include abdominal pain, severe diarrhea, headache and rose spots on the body, etc. It is often called “typhoid fever”. Intestinal bleeding or perforation is its most serious concurrent.


English name:    Typhoid

Latin scientific name:    Salmonella typhi

Nickname:    Enteric Salmonella

Boundary:    Bacterial kingdom

Door:    Proteobacteria

Tsuna:    γ-proteobacteria

Head:    Enterobacteriales

Branch:    Enterobacteriaceae

Genus:    Salmonella

Species:    Typhoid


Table of Content

    1. Biological traits

    ▪ Basic form

    ▪ Cultivation and biochemical characteristics

    2. Epidemiology

    3. Detection methods

    4. Popular features

    5. Pathological changes

    ▪ Clinical manifestations

    ▪ Complications

    6. Prevention and Treatment

    ▪ Treatment

    ▪ prevention

    7. Related knowledge

    8. Antigen


What are the Biological Traits of Typhoid?

Typhoid Salmonella, Negative Gram stain: It is short thick rod-shaped, covered with flagella around the body and active in motion . It grows well in bile-containing medium, because lipids and tryptophan in bile can be used as nutritional components of typhoid bacteria.

Typhoid (O) antigen, flagella (H) antigen and surface (Vi) antigen can cause the body to produce corresponding antibodies.

O and H antigens have strong antigenicity, so they can be used in serum agglutination test (Widal reaction) to determine the titers of O and H antibodies in serum to aid clinical diagnosis.

It can release strong endotoxin when the bacterium is lysed, which is the main factor causing the pathogen of typhoid.

Using the invA gene and flagellin gene of Salmonella to amplify by PCR to perform molecular hybridization, 3 to 300 viable cells can be detected, achieving sensitive and specific effects.

It has strong resistance in natural environment, low temperature resistance. It can survive in water for 2 to 3 weeks. It can be maintained in feces for 1 to 2 months, in frozen environment can be maintained for several months. But the resistance to heat and dryness is weak, 60 ℃.

It can be killed in 15 minutes or after boiling, and it is sensitive to general chemical disinfectants. It will die quickly when the residual chlorine in disinfecting drinking water is 0.2 – 0.4mg / L.


Basic form

Size (0.6 – 1.0μm) x (2 – 3μm), no spores, generally with flagella, no capsules, most of which have pili, Gram-negative bacilli.


Cultivation and biochemical characteristics

Facultative anaerobic bacteria form medium-sized, translucent S-type colonies on ordinary agar plates. Colorless colonies were formed on enterobacteria selective media .

Does not ferment lactose and sucrose, does not produce indole, does not decompose urea, VP test is negative, and most produce hydrogen sulfide. Fermenting glucose, maltose and mannitol.

Except for typhoid bacteria, which produce no acid, no other Salmonella produces acid and gas.



In 1907, the case of typhoid fever caused by chef Mary Malone was a famous case in medical history. One problem Wright failed to anticipate was “typhoid Mary”. Mary, a woman who is a chef, caused typhoid fever everywhere she went. Although she was not sick, she transmitted the germs she carried to those who ate her food. When eventually proven to be a person who transmitted the germ, she was detained and quarantined for life.

When the Crimean War broke out in the 1850s, soldiers who died from typhoid were 10 times more likely to die from war injuries.

By 1898, although the disease was still incurable at that time, Wright developed a typhoid vaccine.

During the Boer War that erupted the following year, soldiers still died of typhoid fever 5 times more than those who died of war injuries. However, during World War I, the vaccine was adopted. Millions of soldiers died from the harsh conditions in the trenches, but only 100 died from typhoid fever.

Common sources of typhoid fever are water that is contaminated with germs, or food that has been contacted by typhoid patients or carriers. Today, typhoid fever can be cured with antibiotics.


What is the Diagnosis of Typhoid?

Bacterial culture and serological responses are traditional methods for the diagnosis of typhoid bacteria, but they are low-sensitivity and time-consuming.

The immunological detection methods and polymerase chain reaction technologies that have appeared in recent years have high specificity and sensitivity, and are simple and fast to operate .


Popular characteristics

Patients and carriers are the source of typhoid fever. The germs are excreted with feces and urine, and are contaminated by contaminating drinking water and food. Flies play an intermediary role in the spread of the disease.

From the incubation period, the patient can excrete bacteria through the stool. Some even excrete bacteria for more than 3 months.

Typhoid fever can be caused by water and food contamination. The disease is distributed throughout China and is distributed throughout the year. It is most common in summer and autumn. The incidence is typified by children and young adults.

 The disease is transmitted mainly via the fecal-oral route. The main cause of the outbreak is pollution of water sources. Food contamination can also cause the epidemic. Sporadic cases are mainly spread by daily contact.

People are generally susceptible to typhoid fever, and lasting immunity can be obtained after the illness. This disease has occurred all over the world, and it is more common in tropical and subtropical areas.


Pathological changes


Clinical Manifestation

The incubation period is 7 to 23 days, with an average of 10 to 14 days. Its length is related to the amount of infected bacteria. The clinical manifestations of typical typhoid fever are divided into the following four stages .

1. Initial stage: the first week of disease course. Most of them have a slow onset of fever, fever, and a step-like rise in body temperature, ranging from 39 to 40 ° C on the 5th to 7th day, with chills before fever, few chills, and not much sweating. Often accompanied by general discomfort, fatigue, lack of appetite, abdominal discomfort, etc., the condition gradually worsens .

2. Extreme stage: 2 to 3 weeks. Symptoms and signs specific to typhoid fever appear.

i. Persistent high fever, the heat type is mainly stagnant fever, and a few are relaxation or irregular fever, which lasts for 10 to 14 days.

ii.Digestive symptoms: obvious lack of appetite, thick tongue coating, abdominal discomfort, bloating, constipation or Diarrhea, mild tenderness in the lower abdomen.

iii. Symptoms of the cardiovascular system: relatively slow and heavy pulse

iv. Symptoms of the nervous system: indifferent expression, slow response, hearing loss, severe patients may have delirium, coma or meningeal irritation (deficiency) Meningitis)

v. Hepatosplenomegaly: most patients have splenomegaly, tenderness and tenderness. Part of the liver is large, and liver function may be abnormal or jaundice when it is complicated by toxic hepatitis.  

vi. Rose rash: pale red maculopapular rash with visible pressure on the chest and abdomen skin on the 6th day of the disease. Less than 10 of them appeared in batches and subsided in 2 to 4 days.

3. Remission period: During the 3rd to 4th weeks of the disease, body temperature gradually decreases, symptoms gradually decrease, appetite improves, abdominal distension disappears, and liver and spleen retract. Complications such as intestinal perforation and intestinal bleeding may occur in this period .

4. Recovery period: In the fifth week of the disease, the body temperature is normal, the symptoms disappear, and the appetite recovers. Generally, the patient fully recovers in about one month, but those who are fragile or have chronic disease often prolong the disease.


What are the Complications with Typhoid?

1. Intestinal hemorrhage: The most common serious complication, which is more common 2 to 3 weeks after the onset, the incidence rate is 2% to 15%, often caused by improper diet and diarrhea .

2. Intestinal perforation: The incidence is 2% – 4%, which is the most serious complication. It usually occurs 2 to 3 weeks after the onset, and often occurs in the terminal ileum. Before the perforation, abdominal pain or diarrhea and intestinal bleeding often appear.

Sudden severe pain in the right lower abdomen during perforation, accompanied by nausea, vomiting, cold sweats, shortness of breath, rapid pulse, questioning and decreased blood pressure.

Then there is obvious abdominal distension, abdominal tenderness, rebound tenderness and abdominal muscle tension.

3. Toxic hepatitis: the incidence is 20% to 60%, and it is usually 1 to 2 weeks after the onset of disease .

4. Toxic myocarditis: It is common in patients with severe toxemia 2 to 3 weeks after the onset of disease.


Prevention and Treatment

What is Typhoid Treatment?

    1.   General treatment: isolation and rest, nursing and diet.

    2.   Symptomatic treatment: physical cooling in those with high fever. Sedatives in irritable patient. enemas in constipation, laxatives are prohibited.

    3.   Pathogen treatment: Appropriate antibiotics should be selected according to specific conditions


What is the procedure of Prevention for Typhoid?

1. Manage the source of infection: timely detection, early diagnosis, isolation and treatment of patients and carriers, the isolation period should be from the date of onset to the complete disappearance of clinical symptoms, the body temperature returned to normal 15 days, or continuous stool culture 2 times after stopping the drug ( 1 time a week) before being discharged. Carriers should be treated thoroughly. Consecutive stool tests of 4 negatives can resume food and child related work.

2. Cut off the transmission route: do a good job of “three-pipe extermination” (pipe water, pipe diet, faeces, and flies), wash your hands before and after meals, and avoid eating raw water and dirty food.

3. Protect susceptible people: Susceptible people in endemic areas can be vaccinated against typhoid.


What is Paratyphoid?

Paratyphoid fever is an acute infectious disease caused by Bacillus paratyphoid. The clinical manifestations of paratyphoid fever are similar to those of typhoid fever, but they are generally milder, have a shorter course of illness, and have a lower mortality rate. Paratyphoid fever can be manifested as acute gastroenteritis or sepsis.



There are three types of pathogens of paratyphoid, including A. paratyphoid, E. paratyphoid, and P. paratyphoid. Various types of paratyphoid have “O” and “H” antigens. Under natural conditions, paratyphoid usually only infects humans and occasionally infects animals.



Sources of infection are patients and carriers. The transmission method is roughly the same as that of typhoid, but it is more common to be transmitted by food, because the typhoid bacteria can exist in food for a long time.

The incidence of paratyphoid in China is lower than typhoid fever. Paratyphoid A is common in adults, and children are susceptible to paratyphoid B, but it may vary by region and age.


Pathogenesis and pathological changes

The pathogenesis and pathological changes of paratyphoid fever A and B are roughly the same as those of typhoid fever. Paratyphoid fever C has mild intestinal lesions and no ulcers can form on the intestinal wall, but local organs often have localized suppurative lesions, which can be seen in joints and cartilage , Pleura, pericardium, etc.


What is Clinical Manifestation of Typhoid?

The incubation period of paratyphoid is shorter than that of typhoid fever, usually 8 to 10 days, and sometimes as short as 3 to 6 days. The symptoms of paratyphoid A and B are similar to those of typhoid, but the symptoms of paratyphoid C are special.

(1) The onset of paratyphoid fever A and B slowly, but sudden onset is rare, especially paratyphoid fever B.

At the beginning, there may be acute gastrointestinal inflammation symptoms such as abdominal pain, vomiting, diarrhea, etc.

After about 2 to 3 days, the symptoms ease, and then the temperature rises and typhoid symptoms appear. Fever often reaches a peak within 3 to 4 days, fluctuating greatly and rarely stays.

The heat course is shorter than typhoid fever, and the symptoms of toxic blood are mild, but the intestinal symptoms are more significant.

The rash appears earlier and is large in number and large in diameter. Recurrence and re-ignition are common, but intestinal bleeding and bowel perforation are rare.

(2) The clinical symptoms of paratyphoid fever are complicated, and there are three common types:

1. The symptoms of typhoid fever are similar to those of paratyphoid fever A and B, but abnormal liver function is more likely to occur.

2. The type of gastroenteritis is mainly gastrointestinal inflammation, manifested by fever, nausea, vomiting, abdominal pain, diarrhea, and short duration.

3. Sepsis is common in frail children and patients with chronic wasting disease. Acute onset, chills, high fever and hot irregularities, ranging from 1 to 3 weeks. There are often rashes, hepatosplenomegaly and jaundice.

More than half of the patients may have localized abscesses such as pleurisy, empyema, joints and bones, meningitis, pericarditis, endocarditis, pyelitis and other migraine purulent complications. These complications are extremely stubborn and have a long treatment period. difficult.

The diagnosis, treatment and prevention of paratyphoid fever A, B and C are about the same as typhoid fever. For patients with concurrent purulent lesions, once the abscess is formed, surgical treatment is feasible and the use of antibacterial drugs is strengthened.


How many Antigens are there in Typhoid?

There are three types of antigens in typhoid, called O antigen, Vi antigen and H antigen.

  1. O antigen: body antigen D grou
  2. Vi antigen: capsule antige
  3. H antigen: flagella antigen.


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