Pertussis

　　Bordetella pertussis is the causative agent of whooping cough, a Gram-negative short coccobacillus. It generally requires a large amount (15% to 25%) of fresh blood in culture media to grow well. The blood-glycerol-potato (B-G) culture medium is most suitable for isolating this bacterium. Freshly isolated Bordetella pertussis is phase I bacteria. Phase I bacteria colonies are smooth, have a capsule, and are highly virulent, containing endotoxins and exotoxins. Continuous subculture of colonies becomes rough, and the virulence gradually weakens, and the antigenicity is also different. This non-pathogenic Bordetella pertussis is called phase II, III, and IV. Only phase I Bordetella pertussis can cause symptoms, and immunity can only be produced by vaccines made from phase I bacteria. This bacterium has a very weak survival ability outside the human body, surviving only for 2 hours at room temperature, being inactivated after 1 hour of direct sunlight exposure or 15 minutes of heating at 60°C, and can also be quickly destroyed by general chemical disinfectants. There are also Bordetella parapertussis and Bordetella bronchiseptica in the genus Bordetella. These two are morphologically similar to Bordetella pertussis. The former can cause respiratory symptoms similar to whooping cough, but there is no cross immunity with Bordetella pertussis. The latter is mainly a pathogen for animals. The fourth species in the genus Bordetella is Bordetella avium, a bacterium similar to Bordetella bronchiseptica, which is a pathogen for birds and has not caused human infection.

　　1. Respiratory system complications

　　Bronchopneumonia is a common complication in infants and young children, often occurring during the paroxysmal coughing phase. The pulmonary lesions caused by Bordetella pertussis are mainly interstitial pneumonia, but they are often caused by secondary bacterial infections. There may also be aspiration pneumonia during the paroxysmal coughing. At this time, the body temperature may rise, and the paroxysmal cough may become atypical, but respiratory distress, cyanosis, and wet lung sounds are more prominent. If the bronchus is blocked by mucus, it can cause emphysema; complete obstruction can lead to atelectasis; if alveoli rupture, it can cause pneumothorax, mediastinal emphysema, or subcutaneous emphysema; if the bronchial mucosa and pulmonary interstitium are damaged, bronchiectasis may occur in the future.

　　2. Neurological complications

　　It manifests as whooping cough encephalopathy. It is caused by brain tissue hypoxia, congestion, intracranial hemorrhage, damage to brain cells, and bacterial toxins, and is more common in infants. Symptoms include consciousness disorders, seizures, etc. The cerebrospinal fluid usually shows no changes.

　　3. Worsening of tuberculosis disease

　　It can worsen the original tuberculosis, even causing hematogenous dissemination, leading to miliary tuberculosis or tuberculous meningitis.

　　4. Others

　　The frenulum of the tongue rubs against the lower incisors, causing ulcers in the frenulum of the tongue. Due to the increased intra-abdominal pressure during severe coughing, umbilical hernia, inguinal hernia, rectal prolapse, and other conditions may occur.

　　The Bordetella pertussis invades the respiratory tract of susceptible individuals, and symptoms appear after about 1 to 3 weeks of incubation period (usually 7 to 10 days) after invasion. The course of the disease is divided into 3 stages, but there are no clear boundaries:

　　1. Catarrhal stage:It usually lasts for 1 to 2 weeks, starting with symptoms similar to a cold. After about 3 days, the symptoms improve, but the coughing becomes more severe and gradually turns into paroxysmal spasmodic cough.

　　2. Spasmodic cough period:Paroxysmal spasmodic cough is a characteristic of this period. When the spasmodic cough occurs, it starts with frequent short coughs, ten to dozens of times, and even dozens of times, and the patient is in the expiratory state. Following this, there is a deep and long inspiratory breath, but at this time, the larynx is still in a spastic state, and the airflow through the tense and narrow glottis produces a high-pitched吼 sound, like crowing or barking. This coughing process is repeated until the accumulated mucus in the respiratory tract is coughed out. Due to severe coughing, vomiting, incontinence of urine and feces, flushed face, cyanosis of the lips, opening the mouth and sticking out the tongue may occur. Severe coughing can lead to obstruction of the superior vena cava return, resulting in facial and eyelid edema, in severe cases, nasal mucosa and conjunctival hemorrhage, coughing up blood, and even intracranial hemorrhage. The onset of spasmodic cough has no prodromal symptoms, and any stimulus can trigger it. Without secondary infection, the general body temperature is normal, there are no positive signs in the lungs, or there may be non-fixed rales in children with whooping cough. Newborns and infants under 6 months of age usually do not have spasmodic cough and special吼 sounds, but rather paroxysmal apnea, cyanosis, easy convulsions, and asphyxia, leading to death. Most adult patients have typical symptoms, but some may only have a few weeks of dry cough, and most still work, acting as a source of infection. This should be paid attention to. The duration of the spasmodic cough period is related to the timing and effectiveness of treatment, the severity of the illness, ranging from a few days to 2 months, usually 2 to 6 weeks.

　　3. Recovery period:The convulsive cough subsides and stops, and the crowing-like inspiratory sound disappears. Without complications, it will heal in about 2 to 3 weeks.

　　1. Isolation of infectious sources

　　Strict implementation of respiratory isolation for patients with the disease is an important preventive measure. The isolation period starts from the onset of the disease and lasts for 7 weeks; or from the onset of convulsive cough, lasting for 4 weeks. Close contacts with susceptible children (especially in collective institutions) need to be quarantined for 3 weeks. Adult patients need to avoid contact with children. Only ventilation and air exchange are needed in the epidemic source.

　　2. Protect susceptible individuals

　　1. Active immunization currently uses the DPT (Diphtheria, Pertussis vaccine, Tetanus toxoid) trivalent vaccine, which is used for basic immunization in infants born from 3 to 6 months old, and is administered subcutaneously three times. During the epidemic period, infants who are 1 month old can receive vaccination. Emphasize the completion of the entire course of immunization, and then strengthen according to regulations. Pertussis vaccine can occasionally cause encephalopathy and other neurological reactions, so individuals with pre-existing brain diseases or convulsive diseases, or those who had convulsions after the first dose of pertussis vaccine, should not be vaccinated again. Pertussis vaccine is not administered during the epidemic season of Bacterial Encephalitis. The currently used whole-cell pertussis vaccine has played a certain role, but its effectiveness is still not ideal, and there have been reports of children and adults developing pertussis after immunization.

　　2. Cell-free pertussis vaccine: This is a pertussis vaccine made from certain components of Bordetella pertussis rather than the whole bacterium. It has a better protective effect than the whole-cell pertussis vaccine and avoids the side effects of the whole-cell vaccine. In 1981, Sato of Japan began to use a cell-free pertussis vaccine with pertussis toxin (PT) and filamentous hemagglutinin (FHA) as the main components and achieved success. Subsequently, various cell-free pertussis component vaccines were developed in countries such as the United States, Sweden, and others, which had the most effective results in the population. It has been confirmed that regardless of the type of cell-free pertussis component vaccine, the pertussis toxin (PT) antigen is an indispensable component. Further research has revealed that pertussis toxin monoclonal antibody (PT-McAb) has the characteristics of specifically neutralizing various biological activities of pertussis toxin in vitro and in vivo, and also has a protective effect against Bordetella pertussis infection.

　　3. Passive immunization: For infants or the weak, high-titer pertussis immune globulin can be administered after contact with the patient, but the effect of prevention and alleviation of symptoms is not significant, so it is rarely used.

　　3. Drug prevention

　　Infants who come into contact with patients should be given erythromycin at a dose of 50mg/kg per day, divided into 4 doses for oral administration, for 10 to 14 days, which has a good effect.

　　1. White blood cell count: During the first weekend of onset and the early stage of paroxysmal cough, the white blood cell count is often increased, generally between 20,000 to 30,000/mm3 or higher, with lymphocytes accounting for 60% to 80%. If there is secondary infection, the relative reduction of lymphocytes occurs.

　　2. Cell culture: At the onset, nasopharyngeal swabs are taken, and sputum samples are collected using the cough plate method during the paroxysmal cough period. B-G medium is used for bacterial culture, and the positive rate is relatively high in the early stage. The positive rate at the beginning of the catarrhal stage can reach 90%, while it is generally lower than 50% during the paroxysmal cough period. After 2-3 weeks of paroxysmal cough, the culture is almost all negative. Direct fluorescent antibody staining is a reliable method to detect the colonies of Bordetella pertussis on the culture medium.

　　3. Fluorescent antibody staining method is used to examine the nasopharyngeal swab smear, which has the advantage of rapid diagnosis, but this method has poor specificity and is only used as an auxiliary culture method.

　　4. Double serum agglutination test and complement fixation test are performed in serological examination. If the antibody titer increases, it can be diagnosed. Recently, enzyme-linked immunosorbent assay (ELISA) has been used to measure IgM, IgG, and IgA antibodies, which is helpful for early diagnosis. There are also cases where a single serum agglutination antibody with a titer of 1:320 during the convalescent period is used as a positive diagnostic value.

　　Increase intake of high-fiber vegetables and fruits, maintain a balanced diet, including proteins, sugars, fats, vitamins, trace elements, and dietary fibers, etc., mix meat and vegetables, diversify food varieties, and give full play to the complementary effects of nutrients between foods.

　　I. General Therapy

　　Maintain respiratory isolation, keep the air fresh, and avoid all factors that can induce convulsive cough. Good care should be taken to prevent complications. Pay attention to nutrition.

　　II. Antimicrobial Therapy

　　Applied in the catarrhal phase or early convulsive phase, it can reduce infectivity, alleviate symptoms, and shorten the course of the disease.

　　1. Erythromycin 40～50mg/kg per day, maximum dose 2g/day, taken orally in 3～4 doses, for 7～14 days. TMP 6mg/kg can also be added, taken orally in two doses, for a course of 7 days.

　　2. Ampicillin 100～150mg/kg per day, administered intramuscularly, for a course of 7～10 days. Some say that a large dose of 1～2g/time, twice a day by intramuscular injection, for 7 days may be effective.

　　3. Kanamycin, Compound SMZ, and isoniazid can also be used, with a course of 7～10 days.

　　III. Symptomatic Treatment

　　Expectorants and cough suppressants such as ammonium chloride. Salbutamol (Salbutamol, albuterol) 0.5mg/kg can alleviate cough symptoms. Chlorpromazine and others can reduce nocturnal coughing and promote sleep. In case of infant asphyxia, artificial respiration, oxygen therapy, and anticonvulsant expectoration should be administered as necessary. Procaine can be administered intravenously, 1～2 times a day, for 3～5 days to reduce asphyxia or convulsions, and at the same time, attention should be paid to heart rate and blood pressure. Dehydrating agents can be used in whooping cough encephalitis. Symptomatic treatment should be given in cases of low calcium, low blood sugar, and other conditions.

　　IV. Treatment of Complications

　　Treat according to the type of concurrent disease.

　　V. Corticosteroids

　　Only used for critically ill patients in the short term, such as infants or those with brain disease. Prednisolone 15～20mg/day, taken orally. Or hydrocortisone given intravenously. Pay attention to the side effects of hormones.