Overview of the disease
Bacterial invasion of the lungs causes infections such as coughing, sputum, fever, etc., but may be asymptomatic, commonly associated with Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes and other infections.
Definition
Bacterial infection of the lungs refers to the direct invasion of the lungs by bacteria, including both the infection causing bacterial pneumonia [1]; also includes the infection of bacteria hosted in the lungs, coexisting with the human body without morbidity.
However, for patients who do not develop disease after infection, it is generally more difficult to diagnose, and the impact on the human body is relatively small. Therefore, this paper will focus on the conditions that lead to disease after infection.
Classification
According to the environment of infection can be divided into nosocomial infection, nosocomial infection.
Nosocomial infections
Also known as community-acquired infections, there are two types of infections. One is an inflammation of the lungs that is contracted outside the hospital and the other is an inflammation of the lungs where bacterial infection occurs during the incubation period but develops after admission to the hospital.
Common pathogenic bacteria include Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes, Escherichia coli and Haemophilus influenzae [2].
Nosocomial infection
It refers to a new lung infection that occurs in the hospital more than 48 hours after admission and requires two prerequisites to be met. One is that the patient is not on invasive mechanical ventilation during hospitalization, and the other is that the patient is not in the incubation period of pathogenic infection at the time of admission.
Common pathogenic bacteria that cause hospital-acquired infections include Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, and Staphylococcus aureus [3].
Etiology
Pathogenic causes
There are many types of causative organisms that cause bacterial infections in the lungs, commonly including Staphylococcus aureus, Streptococcus pneumoniae, Streptococcus pyogenes, Escherichia coli, Haemophilus influenzae, Pseudomonas aeruginosa, and Klebsiella pneumoniae.
Predisposing factors
Common predisposing factors include exposure to cold, overexertion, rain, intoxication, and upper respiratory tract infections.
High risk factors
Unhealthy lifestyle
Such as heavy smoking, frequent late nights, alcoholism, working environment exposed to a lot of dust or smoke, etc.
People with underlying diseases
Such as chronic obstructive pulmonary disease, heart failure, tumor, diabetes, uremia, neurological diseases, etc.
Immunocompromised
Such as long-term illness, major surgery, application of immunosuppressants and organ transplantation.
Pathogenesis
Under normal circumstances, bacteria do not exist in the human lungs, and the occurrence of bacterial infections in the lungs often depends on two factors: pathogens and host factors.
Lung infection is more likely to occur if the pathogen is abundant and virulent, and the host’s respiratory defense and systemic immune function are compromised.
Pathogens can be infected by airborne inhalation, flow through the lungs with the blood or lymphatic circulation, spread of neighboring infected sites, and misinhalation of upper respiratory colonizing bacteria. Among them, upper respiratory colonizing bacteria are microorganisms contained on the mucosal surface of the upper respiratory tract and its secretions in normal people.
After the pathogens arrive directly in the lower respiratory tract, they breed and multiply, causing alveolar capillary congestion, edema, intra-alveolar fibrin exudation and cellular infiltration [4], which in turn produces a number of symptoms.
Symptoms
The clinical symptoms of bacterial infection in the lungs vary greatly, most of them are fever, cough, sputum, etc., and those with occult infection may have no obvious discomfort.
Main symptoms
Fever
Fever is often preceded by chills and chills, followed by high fever, usually with an axillary temperature of more than 38.5℃, which can have a good effect after active anti-bacterial treatment.
A few people with poor physical condition, especially the elderly, may not have obvious fever.
Cough and sputum
Cough may be paroxysmal or persistent.
The sputum is often thick and sticky, and may be white, yellow, or even purulent or bloody sputum.
Chest pain
Chest pain may occur in some patients, usually caused by pulling the chest muscles due to severe coughing, or due to bacterial infection invading the pleura, causing pleurisy.
Dyspnea
Patients with large lesions may have dyspnea and shortness of breath, and can only breathe relatively smoothly when they open their mouths and sit upright, and may also have purple lips.
Other symptoms
Some patients may also experience systemic symptoms of toxicity, such as fatigue, profuse sweating, and generalized aches and pains.
Complications
Pseudothorax
Pathogenic bacteria invade the lungs and produce purulent secretions, forming a septic infection and leading to pyothorax.
Infectious shock
It is a more serious complication, mostly caused by bacteremia and sepsis.
The patient manifests as a rapid onset with high fever, and a few patients may not have an elevated body temperature; there may be a drop in blood pressure, or even the blood pressure cannot be measured, and the pulse is weakened; in severe cases, coma may occur, suggesting that the condition is critical [5].
Bacteremia
Bacteria entering the bloodstream from the lungs can lead to bacteremia. In mild cases, it will not show symptoms or only cause a mild inflammatory reaction, but in severe cases, it may lead to high fever, and may even cause other organ infections or failures.
Others
If the bacterial infection in the lungs is more serious, it may also cause myocarditis and respiratory failure.
Consultation
Department of Medicine
Respiratory Medicine
It is recommended to consult the Department of Respiratory Medicine when you experience discomfort such as coughing, coughing up sputum, or fever.
Emergency Department
In case of hemoptysis, dyspnea, unconsciousness, high fever, etc., it is recommended to go to the Emergency Department immediately, or call 120 emergency.
Pediatrics
Children under 14 years of age, especially the younger ones, can go to the Department of Pediatrics first.
Preparation for medical treatment
Preparation for medical consultation: registration, preparation of documents, common problems
Tips for seeking medical treatment
For patients with suspected bacterial lung infections, a chest X-ray or chest CT is often needed, so avoid wearing clothing made of metal, and inform your doctor if you are pregnant or planning to become pregnant.
Preparation Checklist
Symptom checklist
Pay particular attention to the time of onset of symptoms, specific manifestations, etc.
Is there a cough, how long has it been coughing, what kind of cough?
Is there phlegm, what color is the phlegm and can it be coughed up?
Is there a fever, what is the temperature change like?
Is there any chest pain, chest tightness or other discomfort?
In what way did the above discomfort lessen or worsen?
List of medical history
Have you recently gotten wet or consumed a lot of alcohol?
Any chronic lung disease, diabetes, hypertension, etc.?
Any long-term use of glucocorticoids, immunosuppressants, etc.?
Checklist
Test results in the last six months, which can be brought to the doctor’s office
Laboratory tests: routine blood test, C-reactive protein, calcitonin, bacterial culture + drug sensitivity test, etc.
Imaging tests: chest X-ray, chest CT, etc.
Medication list
Medication used in the last 3 months, if available, bring the box or package to the doctor
Antibacterial drugs: e.g. amoxicillin, ceftazidime, etc.
Anti-fever medications: e.g., ibuprofen, acetaminophen, etc.
Cough suppressants: e.g., ambroxol hydrochloride oral solution, carbocysteine, etc.
If you have a box or package of medication, bring it with you to the doctor’s office.
Diagnosis
The diagnosis of bacterial infection in the lungs can be based on a combination of history, symptoms, signs, laboratory and imaging tests, and other relevant information.
Diagnosis is based on
Medical history
History of chronic respiratory disease.
Risk factors such as working environment like dust or fumes, smoking, upper respiratory tract infections.
Immunocompromised individuals.
Clinical manifestations
Symptoms
Cough, sputum, or aggravation of existing respiratory symptoms with purulent or bloody sputum, with or without chest pain.
Dyspnea and respiratory distress may be present if the lesion is extensive.
Most patients have fever.
Signs and symptoms
Early pulmonary signs are unremarkable.
In severe cases, there may be increased respiratory rate, flaring of the nose, and purplish color of the lips.
There are typical signs in solid lung lesions, such as turbidity on percussion, increased trembling and bronchial breath sounds, and wet rales may also be heard [6].
In cases of pleural effusion, there is turbidity on percussion on the affected side of the chest, decreased tremor, and decreased breath sounds.
Laboratory tests
Blood tests
Mainly routine blood tests, C-reactive protein, and calcitonin are used to assess the presence and severity of infection.
In bacterial infection, the total number of white blood cells and the percentage of neutrophils can generally be increased; the presence of a significant increase or significant decrease generally suggests a more severe infection.
C-reactive protein is often elevated in bacterial infections.
Calcitonin may be elevated and may decline rapidly when anti-infective therapy is effective.
Bacteriologic examination
Cultures of sputum, pleural effusion, blood and lung puncture material and drug sensitivity tests are feasible and are important in defining the infectious pathogens and treatment [7].
Lung function tests
It is important for detecting the degree of respiratory patency, the size of lung capacity, and understanding the functional changes of the lungs.
Imaging
Chest X-ray
In the early stage of pneumonia, the lesion is dominated by congestion and exudation, and X-rays are less sensitive to the response of such lesions, so there is a possibility of missed diagnosis in the early stage.
In the middle stage of pneumonia, the X-ray mainly shows a dense image with uniform density, in which the bronchial tubes can be seen to be inflated and translucent.
Chest CT
CT is more sensitive to lung lesions than X-ray, and can more accurately reflect lung inflammation, exudation, fibrosis and other conditions.
CT examination of lung infection often shows scattered, flaky images of increased density [8].
Differential diagnosis
Upper respiratory tract infections
All can present with symptoms such as cough, sputum and fever.
However, upper respiratory tract infections without lung parenchymal infiltration can be differentiated by chest X-ray.
Lung cancer
Lung cancer has no symptoms of acute infection, sometimes there is blood in sputum, and the white blood cell count is not high.
Lung cancer may be accompanied by obstructive pneumonia, and the shadow of tumor becomes obvious after the inflammation subsides by antibacterial drug treatment, or the lymph nodes of hilar lungs can be seen to be enlarged, and sometimes pulmonary atelectasis occurs.
CT, MRI, bronchoscopy and sputum exfoliative cell examination can help to differentiate.
Pulmonary thromboembolism
Most of the time, there are risk factors for venous thrombosis, such as thrombophlebitis, cardiopulmonary disease, trauma, surgery and tumor history, hemoptysis, syncope may occur, and it is more obvious in dyspnea.
X-ray chest radiographs show regional reduction of pulmonary vascular texture, and sometimes wedge-shaped shadows with tips pointing toward the hilum are seen.
Arterial blood gas analysis commonly shows hypoxemia and hypocapnia.
Tests such as D-dimer, CT pulmonary arteriography, radionuclide lung ventilation/perfusion scanning, and MRI may help in differentiation.
Non-infectious lung disease
Non-infectious lung diseases such as interstitial pneumonia, pulmonary edema, pulmonary atelectasis and pulmonary vasculitis also need to be excluded.
Treatment
Aims of treatment: to control infection, reduce symptoms and avoid disease progression.
Treatment principle: anti-infective treatment is the key link in the treatment of lung infection, including empirical treatment and selection of sensitive antimicrobial drugs. Antimicrobial drug therapy should be carried out as early as possible, and the first dose of antimicrobial drug should be given as soon as lung infection is suspected [9].
General treatment
Lifestyle interventions
Smoking cessation.
Rest and exercise when physically possible.
Diet
Ensure the intake of calories and nutrients such as protein and vitamins, and focus on light and easy-to-digest food.
Parenteral nutrition can be used if necessary.
Oxygenation
For patients with chronic underlying diseases, such as chronic obstructive pulmonary disease, interstitial lung disease, etc., or when the blood oxygen saturation level is lower than 93%, oxygen can be administered by nasal catheter, or by face mask.
When nasal catheter oxygen is administered, the inhaled oxygen concentration is usually 28% to 30%.
Nursing care for expectoration
The patient’s family members or accompanying staff should provide necessary sputum elimination care for the patient, such as patting the chest and back, positional drainage, and so on.
Respiratory isolation
For some patients with respiratory infectious pathogens, respiratory isolation should be carried out, such as wearing masks and separate wards.
Medication
Antibacterial drugs
Medication selection
The more commonly used drugs for young adults and patients with bacterial lung infections without underlying disease are penicillins (e.g., amoxicillin, piperacillin) and first-generation cephalosporins (e.g., cefradine, cefadroxil) [9].
Respiratory fluoroquinolones (e.g., moxifloxacin, gemifloxacin, and levofloxacin) may be used for drug-resistant Streptococcus pneumoniae.
Respiratory fluoroquinolones, second- and third-generation cephalosporins (e.g., ceftazidime, ceftriaxone, etc.), or ertapenem are commonly used in the elderly, and in patients with underlying diseases requiring hospitalization.
For specific bacterial infections, such as tuberculosis, treatment with drugs such as isoniazid, rifampicin, and ethambutol needs to be standardized.
Sputum culture and drug susceptibility testing should also be performed before administering the medication, and when the results are available, the decision to adjust antibiotics can be made at your discretion.
Course of treatment
Anti-infective treatment can generally be discontinued after the fever has subsided for 2 to 3 days and the main respiratory symptoms have improved significantly, but the course of treatment should depend on the severity of the disease, the speed of remission, complications, and different pathogens, and it is not necessary to take the degree of absorption of lung shadows as an indication for discontinuing antimicrobial drugs.
Usually, the course of treatment is 5-7 days for patients with mild and moderate conditions, and the course of anti-infective treatment can be appropriately prolonged for patients with severe conditions and those with extrapulmonary complications.
Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella spp. or anaerobes are prone to cause necrosis of lung tissues, and the course of antimicrobials can be extended to 14-21 days.
Phlegm remedies
For cough with mucous phlegm, drugs such as Ambroxol Hydrochloride and Carbocisteine can be used to dissolve phlegm.
When there is a lot of phlegm, it is usually not necessary to stop the cough, otherwise it is not conducive to coughing out the phlegm.
Other treatments
For those with respiratory distress, tracheal intubation and mechanical ventilation are performed when necessary.
For those with high fever, when the body temperature exceeds 38.5℃, active physical cooling can be done, such as warm water wiping the armpits, thigh roots, neck and other parts. Combination of antipyretic drugs, such as ibuprofen tablets and acetaminophen tablets, can be used if necessary.
Prognosis
Cure
Untreated
Only some people with mild infections and good health may heal on their own without treatment. Most people with lung infections may experience a variety of serious complications and even death if left untreated.
After treatment
Most bacterial infections of the lungs can be cured. Some patients have poor treatment and poor prognosis due to drug resistance and untimely treatment.
Most patients with Streptococcus pneumoniae can be cured if they are given effective antibiotic treatment.
The morbidity and mortality rate of Staphylococcus aureus pneumonia is 15% to 20%, and the prognosis of young children and elderly patients is poor. The morbidity and mortality rate of toxic shock is about 10% [9].
The morbidity and mortality rate of Klebsiella pneumonia remains as high as 54%. Immunocompromised, bacteremic, leukopenic and elderly patients have a worse prognosis, and prevention and early diagnosis and treatment can help to reduce the morbidity and mortality rates [9].
Prognostic factors
The prognosis of pulmonary infections is influenced by a number of factors, and the following factors often lead to a poor prognosis [10].
Development of multi-drug resistance by the causative organism.
Strong pathogenicity of the infecting strain.
Poor basal status of the patient.
Extensive lung infection lesions.
Diagnosis and treatment are not timely.
Complications such as infectious shock and bacteremia occur.
Smoking, advanced age, immunosuppression, etc.
Hazards
People with lung infections may experience high fever, cough, sputum and other discomforts, which can often interfere with work and life.
Severe lung infections may lead to infectious shock, respiratory failure, systemic multi-organ failure, and even death.
Most bacterial lung infections do not leave any damage in the lungs after healing, and the structure and function can return to normal, but Staphylococcus aureus, Pseudomonas aeruginosa, and Klebsiella pneumoniae may lead to necrosis and degeneration of lung tissues, leaving behind cavities or fibrosis in the lungs.
Daily
Daily management
Life management
Smoking cessation.
Some bacterial infections are contagious, patients should wear a good mask and avoid crowded places.
Regular work and rest, avoid staying up late, exertion, and exercise appropriately.
Develop good sputum expectoration habit, can be assisted by prone position to expel sputum, or family members to assist back patting.
Dietary management
Eat a light diet with balanced nutrition, and eat more vegetables and fruits with high vitamin content.
Disease monitoring
Monitor body temperature and seek medical advice when fever develops.
Observe the change of symptoms, if there is any discomfort such as dyspnea, panic, depression, loss of appetite, etc., consult a doctor immediately for follow-up.
Observe sputum changes, if pus sputum appears, you should seek medical attention.
Follow-up review
If there is any discomfort during the medication or if the symptoms do not improve or even worsen after 1 week of medication, it is necessary to consult a doctor for follow-up examination.
It is recommended to repeat the examination after 1 week of stopping the medication.
Items to be reviewed include routine blood test, chest X-ray, chest CT, and so on.
Prevention
Strengthen physical exercise to enhance physical fitness.
Reduce risk factors such as smoking and alcohol abuse.
Influenza vaccination is recommended for those older than 65 years of age.
Pneumonia vaccination is available for those who are older than 65 years or less than 65 years but have cardiovascular disease, pulmonary disease, diabetes mellitus, alcoholism, cirrhosis and immunosuppression [10].