Severe cough in children

Introduction A severe cough in children is one of the symptoms of whooping cough. Pertussis (whooping cough) is a common acute respiratory infection in children. Bordetella pertussis is the causative agent of this disease. It is characterized by paroxysmal spasmodic cough, with a special inhalation snoring at the end of the cough. The course of the disease is long, up to several weeks or even 3 months, so it is called pertussis. Young children suffering from this disease are prone to complications such as asphyxia, pneumonia, encephalopathy, and high mortality. In recent years, the incidence of infants and adults has increased.

Cause

The pathogen is B. pertussis in the genus Bordetella, often referred to as B. pertussis. It is known that B. genus has four bacilli, in addition to B. pertussis, B. parapertussis, B. bronchiseptica and B. bunge (B. Avium). Bird-shaped Bacterella generally does not cause human disease, only causing bird infection. B. pertussis is about 1.0-1.5 m long and about 0.3-0.5 m wide. It has a capsule, can't move, is negative for Gram stain, aerobic, no spore, no flagella, and stained with toluidine blue for darkening at both ends. Bacterial culture requires a large amount (15% to 25%) of blood to reproduce well, so colonies are often isolated in Border-Gengous medium (ie, blood, glycerin, potato). B. pertussis grows slowly, and after 3 to 7 days in a humid environment of 35-37 ° C, a small, opaque colony grows. The first colony is swelled and smooth, and it is smooth (S) type, also known as Phase I bacteria. The morphology is consistent, with capsule and strong virulence and antigenicity, and the pathogenicity is strong. If the isolated colonies are cultured in a common medium, the colonies change from a smooth type to a rough (R) type, which is called an IV phase bacteria, has no capsule, loses virulence and antigenicity, and loses pathogenicity. Phase II and Phase III are intermediate transition types. Bordetella pertussis produces many toxic factors, and five toxins are known:

1 pertussis exotoxin (PT); a protein in the cell wall of B. pertussis, formerly known as leukocytosis or lymphocyte promoting factor (LPE), histamine sensitizing factor (HSF) Insulin activating protein (IAP). Pertussis exotoxin is composed of five non-covalent chain subunits (S1 to S5). The subunit (S2 to S5) is a non-toxic unit that binds to the host cell membrane and mediates toxic effects through the subunit S1 with enzyme activity. S1 can catalyze the separation of part of ADP-ribose from nicotinamide adenine dinucleotide (NAD) by adenosine diphosphate (ADP)-ribosyltransferase activity, and transfer to cell membrane to inhibit guanosine triphosphate (CTP) binding. That is, G protein synthesis leads to cell metaplasia. It also promotes lymphocyte elevation, activates islet cells, and enhances the immune response.

2 heat-resistant endotoxin (ET), can only be partially destroyed at 100 ° C for 60 min, can be inactivated at 180 ° C. This toxin can cause fever and cough in the body.

3 heat-resistant toxin (HLT) This toxin can destroy its toxic effects after heating at 55 ° C for 30 min. This toxin antibody has no protective effect on B. pertussis infection.

4 tracheal cytotoxin (TCT): can damage the host airway ciliated epithelial cells, causing denaturation and necrosis.

5 adenylyl cyclase toxin (ACT): an enzyme present on the surface of B. pertussis cells. This enzyme is activated by calmodulin after entering phagocytic cells, catalyzes the production of cAMP, interferes with phagocytosis, and inhibits neutrophils. Chemotaxis and phagocytic bactericidal ability to continue infection. ACT is also a hemolysin that acts as a hemolysis.

The important antigen of pertussis is the two hemagglutination active antigens of pertussis. One is filamentous hemagglutinin (FHA), which is also called fimbriae antigen because it comes from the surface of the bacteria. FHA plays a decisive role in the adhesion of B. pertussis to airway epithelial cells, which is the main cause of pathogenesis. The experiment found that FHA-immunized mice were able to fight a lethal attack against B. pertussis, so FHA is a protective antigen. Another agglutinogen (AGG) is a protein component of the outer membrane and fimbriae of B. pertussis, which mainly contains three serotype coagulation factors of 1, 2, and 3. AGG-1 is species specific; AGG-2, 3 is type specific.

Know the local prevalence by detecting the type of agglutinogen. The corresponding antibodies to these two hemagglutinin antigens are currently considered to be protective antibodies. Bordetella pertussis is classified into seven types of agglutinogens according to the heat-resistant agglutination antigenicity, and type 1 agglutination is possessed by all of the pertussis bacilli. Type 7 agglutination is common to the genus Boutis (including B. parapertussis and Bronchiseptica). Types 2 to 6 divide B. pertussis into different serotypes with different combinations. The serotype was determined mainly by studying the serotype of the strain at the time of epidemic and selecting the serotype strain to produce the bacterin. In addition, there is no cross-immunization between B. pertussis and B. pertussis, and it can also cause epidemics. B. pertussis has weak resistance to external physical and chemical factors. It is destroyed after 55 minutes at 55 ° C, and it can be killed by drying for several hours. Sensitive to general disinfectants and weak against UV light. However, it survived longer at 0 to 10 °C.

an examination

Related inspection

Lung and pleural auscultation

Clinical manifestation

According to the history of exposure and typical coughing period, if no typical cough can be combined with typical blood changes, a clinical diagnosis can be made. Pathogenic diagnosis relies on bacterial culture and specific serological tests. For patients with persistent cough of unknown age in all ages, especially those with cough symptoms, the possibility of this disease should be considered for further testing. The incubation period is 3 to 21 days, with an average of 7 to 10 days. The typical clinical course is divided into 3 phases.

Pre-cough period

Cough, sneezing, runny, tearing, low fever or moderate fever, similar to cold symptoms. After 3 to 4 days, the symptoms disappeared and the heat retreated, but the cough gradually increased, especially at night. This period is the most contagious, sustainable for 7 to 10 days, if timely treatment, can effectively control the development of this disease.

2. Coughing period

The catarrhal period failed to control, and the patient developed paroxysmal spastic cough, which was characterized by frequent uninterrupted short cough for more than 10 sounds, such as exhalation state, and finally deep exhalation. At this time, the negative pressure in the thoracic cavity was caused by coughing. In addition to inhalation, the vocal cords are still in a state of tension, and the airflow quickly passes through the narrow glottis to produce a murmur-like high-pitched inspiratory sound, followed by a series of coughs. Such recurrent episodes are exacerbated more than once, until a large amount of sticky sputum is coughed up and vomiting of stomach contents. There are incentives before the onset of cough, and there are often signs of discomfort such as itchy throat and chest tightness. The child feels that the cough is coming, showing fear, and the expression is painful when the cough occurs. When coughing, due to increased pressure in the thoracic cavity, the superior vena cava is blocked, the jugular vein is engorged, the eyelids and face are congested and edema, the lips are cyanotic, and the conjunctiva is congested. If the capillaries rupture, the subconjunctival hemorrhage and nosebleed can be caused.

Some patients have tongues extending outward from the teeth, rubbing against the incisors, and often have tongue-tie ulcers. Some patients suffer from cough and increased abdominal pressure, resulting in incontinence and snoring. In this period, if there is no complication, it usually lasts for 2 to 6 weeks, and it can last for 2 months or more. The symptoms of pertussis in infants and newborns are quite special. There is no typical cough. Due to the small glottis, apnea may occur due to occlusion of vocal cords and sticky secretions. Hair loss due to lack of oxygen, even convulsions, may also be due to suffocation. And die. Adults or older children, pertussis symptoms are mild, and atypical, mainly for dry cough, no paroxysmal cough, white blood cells and lymphocytes are not obvious increase, mostly misdiagnosed as bronchitis or upper respiratory tract infection.

3. Recovery period

The number of paroxysmal coughs gradually decreased to disappear, and it recovered for 2 to 3 weeks. If there is complicated pneumonia, the atelectasis often does not heal, and it can last for several weeks. Bronchopneumonia is a common complication and occurs mostly during the coughing period. Can also be complicated by pertussis encephalopathy, patients with disturbance of consciousness, convulsions, but no change in cerebrospinal fluid.

Diagnose based on

According to the local prevalence, there is no history of contact with pertussis patients. If the child has had fever, but the symptoms of cough after heat withdrawal are aggravated, especially in the evening, the cough is severe, and there is no obvious lung positive signs, it should be used as a suspected diagnosis. If there is obvious cough, the peripheral blood counts of white blood cells and lymphocytes are significantly increased, according to these characteristics can make a clinical diagnosis of whooping cough. In addition, bacterial culture positive or serological immunology, positive PCR test can confirm pertussis.

Differential diagnosis

Differential diagnosis of severe cough in children:

(a) acute bronchitis and pneumonia

Bronchitis caused by influenza B bacteria, adenovirus, respiratory syncytial virus, parainfluenza virus, etc., cough is more severe, often cough. However, severe cough appears within a few days of onset. There is no echo of chicken sputum after coughing, and it is not necessarily aggravated at night. In the acute phase, symptoms of systemic infection such as cough and qi are severe, and the lungs often have a fixed dry and wet sound. The white blood cell count is normal or high. After appropriate treatment, the symptoms are alleviated or disappeared in the short term.

(B) bronchial lymph node tuberculosis

A swollen lymph node that compresses the bronchi or erodes the bronchial wall can cause a coughing cough, but there is no echo of the chicken. Diagnosis can be made according to symptoms of tuberculosis poisoning, tuberculin test, and X-ray changes in the lungs.

(three) tracheobronchial foreign body

Sudden onset of paroxysmal cough, a history of foreign body inhalation, white blood cells do not increase, X-ray visible segmental atelectasis, bronchoscopy can be found in foreign bodies.

(4) Pertussis syndrome

Among the people who are generally immunized against whooping cough, there are still cases of "pertussis" that can be sporadic. Adenoviruses, other respiratory viruses, Mycoplasma pneumoniae, and B. pertussis are often isolated without B. pertussis. Its clinical symptoms, lung X-ray findings and bloody findings, similar to typical whooping cough, need to be identified by pathogens. It is estimated that approximately 20% of cases are caused by the above mentioned pathogens. Chlamydia infection can have a pertussis-like cough, but no chicken-like echo. The symptoms caused by B. pertussis are mild and the course of disease is short.

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