Pneumonia caused by Streptococcus pneumoniae in children

　　1. Etiology

　　Streptococcus pneumoniae is a Gram-positive diplococcus, belonging to the genus Streptococcus. Asymptomatic carriers of the bacteria can play a more important role in spreading infection than pneumonia patients. This disease is generally sporadic, but it can also occur in collective nurseries and kindergartens. Changes in climate can reduce body resistance, leading to more cases, which are more common in winter and spring. This may be related to the prevalence of respiratory tract viral infections.

　　2. Pathogenesis

　　Streptococcus pneumoniae is a Gram-positive coccus, often arranged in pairs, occasionally in chains or as single cells. This bacterium does not produce endotoxins or exotoxins, and its pathogenicity depends on the invasive action of the capsule containing high molecular weight polysaccharides on tissues. Streptococcus pneumoniae is typed according to its capsular specific polysaccharide antigen, and there are 86 different serotypes. The common pathogenic serotypes of Streptococcus pneumoniae in China are 5, 6, 1, 19, 23, 14, 2, 3, 7, 8, and so on. Pneumonia caused by Streptococcus pneumoniae in children is often caused by serotypes 3, 6, 14, 19, and 23. Streptococcus pneumoniae is a normal flora of the nasopharynx, and it can only cause disease when the respiratory defense mechanism is damaged. When children have upper respiratory tract viral infections, fatigue, catching a cold, and other triggering factors that lead to a decrease in body immunity, the pathogen enters the body and multiplies in the alveoli, causing the disease. The primary lesion of Streptococcus pneumoniae pneumonia is often distributed in segments or subsegments, while secondary Streptococcus pneumoniae pneumonia often presents as bronchopneumonia.

　　Children not receiving appropriate treatment may develop empyema, lung abscess, myocarditis, pericarditis, and toxic hepatitis, among other complications. Severe cases may be accompanied by septic shock, and even cerebral herniation may occur due to cerebral edema. When there is a space-occupying lesion in a certain compartment of the normal cranial cavity, the pressure in that compartment is higher than that in adjacent compartments. Brain tissue moves from the high-pressure area to the low-pressure area, being squeezed into nearby physiological or non-physiological channels, causing some brain tissue, nerves, and blood vessels to be compressed. This leads to obstruction of cerebrospinal fluid circulation and the production of corresponding symptom complexes, known as a brain hernia.

　　1. Symptoms

　　A few patients may have prodromal symptoms, and the onset is often abrupt. The clinical manifestations of Streptococcus pneumoniae pneumonia in older children are similar to those in adults. They may initially have brief and mild symptoms of upper respiratory tract infection, followed by chills, sudden high fever, which can reach 40 to 41 degrees Celsius, flushed or cyanotic complexion. Chest pain, decreased appetite, fatigue, restlessness or drowsiness, dry cough, rapid breathing up to 40 to 60 times/min, expiratory grunting, flaring of the nostrils, indentation of the supraclavicular, intercostal, and inframammary areas, and so on. In the early stages, signs are often absent, and pulmonary consolidation signs may appear 2 to 3 days later. Chest pain during breathing, so children often lie on the affected side. Initially, coughing is usually not severe, without sputum, and later sputum may become rust-colored. Vomiting is common in the early stages, and a few children may have abdominal pain, which is sometimes misdiagnosed as appendicitis. Young children may have diarrhea. Mild cases are conscious, and a few children may experience headache, stiffness of the neck, and other meningeal irritation symptoms. In severe cases, seizures, delirium, and coma, as well as the manifestations of toxic encephalopathy, may occur, often mistaken for central nervous system diseases. Severe cases may be accompanied by septic shock, and even cerebral herniation may occur due to cerebral edema. Older children may have herpes simplex around the lips.

　　2. Chest Signs

　　In the early stages, there may only be mild dullness on percussion or decreased breath sounds. After pulmonary consolidation on the 2nd to 3rd day of the disease course, there are characteristic dullness on percussion, enhanced vibration, and tubular breathing sounds, and sometimes a crackling sound can be heard. Pulmonary signs change little throughout the disease course, but there is an increase in moist rales during the recovery period. In a few cases, there may be no abnormal chest signs throughout. Diagnosis relies on X-ray examination.

　　3. Natural Course

　　Most cases experience a sudden drop in body temperature from the 5th to 10th day of the disease course, which can decrease by 4 to 5 degrees Celsius within 24 hours. When the temperature drops to around 35 degrees Celsius, profuse sweating and collapse can be observed, resembling a shock-like state. Those treated with antibiotics early can usually reduce fever within 1 to 2 days, and pulmonary signs may disappear approximately one week later.

　　In some countries and regions, high-risk populations susceptible to Streptococcus pneumoniae infection (including children, especially children with sickle cell disease who are most susceptible) are recommended to use multivalent Streptococcus pneumoniae polysaccharide vaccine for prevention, which is considered effective. The research is still ongoing. Streptococcus pneumoniae infection, the lesion starts in the alveoli and rapidly spreads to the纤维素itis of the entire or multiple large lobes of the lung. It is more common in young and middle-aged adults, with clinical manifestations of sudden onset, chills, high fever, chest pain, cough, expectoration of rust-colored sputum, dyspnea, and signs of lung consolidation, as well as increased leukocytes.

　　1, Peripheral blood picture

　　Blood leukocyte count and neutrophil count are significantly elevated, reaching (15-40)×10^9/L, occasionally reaching (50-70)×10^9/L, mainly neutrophils, with nuclear left shift, and toxic granules may be visible. However, a few children may have leukopenia, indicating severe illness.

　　2, Pathogen examination

　　Culturing airway secretions, blood, and pleural effusion can obtain Streptococcus pneumoniae. Direct smear staining and microscopic examination of sputum, if Gram-positive, paired球菌 are found, it has diagnostic significance. Sputum and blood cultures with growth of Streptococcus pneumoniae can confirm the diagnosis, but the positive rate is not high.

　　3, Serological examination

　　10% to 30% of children with Streptococcus pneumoniae pneumonia have bacteremia, but due to the early use of antibiotics, the positive rate of blood culture in China is very low. At present, the etiological diagnosis of Streptococcus pneumoniae pneumonia is mostly through serological methods, such as measuring the antigen of Streptococcus pneumoniae in the serum, urine, or saliva of children, but some authors believe that this method cannot distinguish between Streptococcus pneumoniae infection and colonization. Recently, there have been reports on the diagnosis through the measurement of serum Streptococcus pneumoniae hemolysin (Pneumolysin) antibody, or circulating immune complexes containing antibodies against Streptococcus pneumoniae, but its sensitivity is still insufficient in infants. Blood and urine samples can be collected for the detection of Streptococcus pneumoniae capsular antigen using CIE, LA, and other methods, and Streptococcus pneumoniae antibodies can be measured using radioimmunoassay, killing power test, and EIJSA methods for auxiliary diagnosis. C-reactive protein is often positive.

　　4, Other

　　In addition, urine examination may show trace protein, and most children with nasopharyngeal secretions can be cultured with Streptococcus pneumoniae, but its pathogenic significance cannot be confirmed. Performing blood culture or pleural effusion culture before the administration of antibiotics has certain diagnostic significance. X-ray changes are not necessarily parallel to the clinical course; the consolidation lesions appear earlier than the pulmonary signs, but they have not completely resolved several weeks after clinical remission. Consolidation lesions are not common in young children. There may be pleural reaction with effusion. Early X-ray examination may show deepening of pulmonary vessels or a thin shadow confined to a segment, followed by large areas of uniform and dense shadows, occupying the entire lobe or a segment of the lung, which gradually fade after treatment. Pulmonary bullae may be visible. A few cases may have pleural effusion. Most children will have the X-ray shadow disappear 3 to 4 weeks after the onset.

　　The diet of children mainly includes easily digestible foods, and foods high in polysaccharides, high protein, spicy, cold, and greasy should be avoided. Eat nutritious foods and maintain a reasonable diet structure.

　　1. Treatment

　　General therapy can refer to the treatment of bronchopneumonia. Antibiotic treatment: Patients sensitive to penicillin are preferred to take penicillin G or amoxicillin (ampicillin); patients with low-level resistance to penicillin can still be preferred to take penicillin G, but the dose should be increased, and first-generation or second-generation cephalosporins can also be selected, as well as alternative ceftriaxone or cefotaxime or vancomycin. For patients with high-level resistance to penicillin or with risk factors, vancomycin or ceftriaxone or cefotaxime is preferred. The usual dose of penicillin is 50,000 to 100,000 U/(kg·d), or 6,000,000 to 10,000,000 U or more per day, given in 4 divided doses by intramuscular or intravenous injection. Children allergic to penicillin can be given erythromycin intravenously at a dose of 100 mg/(kg·d), and can be changed to oral administration after improvement. Treatment should last for 1 to 2 weeks, or 3 to 5 days after complete remission of fever. If there is no improvement in the condition after 2 to 3 days of penicillin treatment, consideration should be given to rare penicillin-resistant strains and other antibacterial drugs should be used. Other drugs can be changed according to the sensitivity test results of Streptococcus pneumoniae isolated from throat swabs. For cases showing infectious shock or intracranial hypertension, such as brain edema or brain hernia, rescue measures should be taken according to the treatment for infectious shock or intracranial hypertension. For patients seeking medical attention late, it is necessary to pay attention to common complications such as empyema, lung abscess, pericarditis, myocarditis, and toxic hepatitis, and appropriate treatment should be given in a timely manner. Empyema requires aspiration of pus.

　　2. Prognosis

　　Streptococcus pneumoniae does not produce true exotoxins, and the capsular polysaccharide antigen does not cause tissue necrosis, so it is usually not left with lung damage after the treatment of lobar pneumonia. However, scars left in the lung from multilobar pneumonia may occasionally cause chronic restrictive pulmonary disease.