Sepsis or multiple migratory abscesses

Introduction Septicemia or multiple migratory abscesses are the basis for the diagnosis of anaerobic pneumonia in the elderly. Anaerobic pulmonary infection is inflammation of the trachea, bronchi, lung parenchyma, and pleural cavity caused by anaerobic bacteria. Anaerobic bacteria have a wide variety of virulence and pathogenicity, which is one of the common pathogens causing lung infection. Older people are more susceptible to pneumonia due to aging and degeneration of the lungs and changes in local anatomy. The onset of pneumonia in the elderly is hidden, and it is not easy to be discovered. Moreover, due to the degenerative changes of the body organs and functions of the elderly, the prognosis is poor. It is necessary to take measures to prevent the occurrence of pneumonia.

Cause

(1) Causes of the disease

Anaerobic bacteria are a type of bacteria that can grow and reproduce under conditions of low oxygen or redox potential. According to the sensitivity to oxygen, generalized anaerobic bacteria can be divided into obligate anaerobic bacteria, micro-aerobic bacteria and oxygen-resistant bacteria. It is customary for anaerobic bacteria to be obligate anaerobic bacteria, that is, they must grow under conditions that greatly reduce the partial pressure of oxygen, and can be divided into facultative anaerobic bacteria, micro-aerobic bacteria and obligate anaerobic bacteria. The so-called anaerobic pneumonia in clinical practice mainly refers to pulmonary infection caused by obligate anaerobic bacteria. Obligate anaerobic bacteria can only survive or grow under the condition of no oxygen or lower than normal atmospheric oxygen partial pressure, and can be further divided into extreme anaerobic bacteria, moderate anaerobic bacteria and anoxic anaerobic bacteria.

1. Extreme Anaerobic Bacteria: These anaerobic bacteria are extremely sensitive to oxygen and die at 0.5% oxygen concentration or less than 10 minutes in air. Because it is extremely difficult to isolate in clinical laboratories, it is still unknown.

2. Moderate anaerobic bacteria: These anaerobic bacteria can grow in 2% to 8% oxygen concentration and can be separated by exposure to air for 60 to 90 minutes. Common anaerobic bacteria that cause lung infections, such as Bacteroides fragilis and Clostridium perfringens, are the most common types of anaerobic bacteria in clinical practice.

3. Anaerobic anaerobic bacteria: These anaerobic bacteria grow best under anaerobic conditions and under poor aerobic conditions. Clostridium difficile and Clostridium histolyticum belong to this category.

Common anaerobic bacteria in which lung infections are:

(1) Gram-negative anaerobic bacteria: a common bacterium for pulmonary anaerobic infection. Reported in the literature on aspiration pneumonia, necrotizing pneumonia, lung abscess and empyema, the isolation of Gram-negative anaerobic bacteria accounted for 53.67%, 56.45%, 50.87% and 39.29%, respectively, of which Bacteroides accounted for the first place, followed by It is a genus Fusobacterium.

1 Bacteroides: Gram-negative Bacillus-free. A few strains have capsules or flagella. Obligate anaerobic. It can utilize intermediate metabolites of sugars and proteins. The model strain is Bacteroides fragilis. The shape of the cells is short rod-shaped, uneven dyeing, and the middle staining is light or non-colored, so that the cells are vacuolated. Both ends are round and thick. Irregular in solid medium, the performance varies. When the culture conditions are slightly changed, such as insufficient anaerobic conditions, malnutrition or accumulation of acidic products, the cells are polymorphic. Bacteroides causing lung infection is most common in Bacteroides fragilis and Bacteroides producing melanin.

2 Clostridium: It may be Gram-negative Bacillus-free, obligate anaerobic, flagella-free, and can utilize sugar and peptone. The model strain is Fusobacterium nucleatum, which is inflated in the middle and has sharp ends. The gram-positive granules in the bacteria body vary in length and shape. The cells are double and the tip is on the tip. The genus Fusobacterium which causes pulmonary infection is more common with Fusobacterium nucleatum and Fusarium oxysporum.

(2) Gram-positive anaerobic bacteria: Gram-positive anaerobic bacteria is second only to Gram-negative anaerobic bacteria in lung infections. It is reported in the literature that the above lung infections account for about 1/4 to 1/3, among which Digestive Streptococcus and Digestococcus are common.

1 Digestive Streptococcus: Digestive Streptococcus is small, 0.5 ~ 0.6m in diameter, arranged in pairs or in chains, forming round, smooth, convex, gray-white, opaque, non-hemolyzed colonies with a needle tip diameter of 1mm. The most common Gram-positive anaerobic cocci for lung infection.

2 Digestive genus: The bacteria of the digestive bacterium are round, 0.3-1.3 m in diameter, arranged in double, short chain or pile. It grows slowly and grows for 2 to 4 days to form small colonies, which are common bacteria in lung anaerobic infection.

(3) Gram-negative anaerobic cocci: Veerococcus eutropha in Gram-negative anaerobic cocci, which is also the pathogen of lung anaerobic infection, accounting for 3.7% of lung anaerobic infection. The bacterial cell is small, 0.3 to 0.6 m in diameter, and sometimes short-chain, and is Gram-positive at the initial stage of culture, and becomes Gram-negative overnight.

(4) Gram-positive anaerobic bacteria: Gram-positive anaerobic bacteria account for about one-fifth of anaerobic bacteria in the lung, of which the genus Eubacterium, Propionibacterium and Clostridium are the most common.

1 genus Bacillus: The genus Eubacterium is Gram-positive without Bacillus, and the morphology is regular, and the size of the cell is (0.6-1) m×(24) m. Often arranged in single, double, short chain, Gram-positive colonies small round and flat, translucent, gray, not hemolyzed. The model strain is a sticky bacterium. It accounts for about a quarter of the infection of Gram-positive bacilli in the lungs.

2 Propionibacterium: Gram-positive, non-spore polymorphic bacillus. Straight or slightly curved, rod-shaped, the size is (0.5 ~ 0.8) m × (1 ~ 5) m, uneven dyeing. The arrangement is X, Y, V and grid. No capsule, no flagella. Colonies are small, round, gray or other colors, opaque. The model strain is Propionibacterium fuliginea. It is also a common bacterial infection in the lungs.

3 Clostridium: The middle part of the cell is swollen and the model is Clostridium butyricum. The shape of the cells is straight or slightly curved, and the length or width is constant. The ends are pointed or round, and the arrangement is single, double, short chain or diverse.

Old age is an important factor in the onset of the disease, often with a history of poor oral hygiene, periodontitis, craniocerebral injury, cerebrovascular disease, epilepsy, alcohol abuse, general anesthesia. In addition, bronchoconstriction, bronchial neoplasms, obstructive pneumonia, bronchiectasis, pulmonary embolism and other basic diseases are also prone to anaerobic infection.

(two) pathogenesis

The entry of anaerobic bacteria into the lungs does not necessarily lead to infectious lesions. Lung anaerobic infection is also the result of the mutual comparison between microbes and the body. The body's defense ability is the main factor determining whether infection can occur, and the pathogenic process of anaerobic bacteria plays an important role in causing infection.

1. The body's defense ability is reduced

(1) Decreased systemic immune function: In some terminal stages of chronic diseases, such as diabetes, cirrhosis, and kidney disease, in addition to causing common bacterial infections, it is easy to cause anaerobic infection. Tumor patients receiving radiotherapy and chemotherapy, organ transplantation and connective tissue disease patients with anti-metabolite drugs, blood disease patients receiving steroid therapy, chronic alcoholism can cause severe immune function decline, easily lead to anaerobic infection.

(2) Local defense ability disorders: including barrier function of local mucosa, reduction of redox potential of local tissues and impaired vitality of phagocytic cells and sterilization system. Local mucosal barrier function is more common in lung diseases such as bronchiectasis, bronchial lung cancer, and chronic obstructive pulmonary disease. The damage is not only beneficial to anaerobic invasive, but also beneficial to bacterial reproduction and spread. The decrease in tissue redox potential is often caused by vascular disease, shock, edema, trauma, surgery, cancer, and aerobic growth of local tissues. Under normal circumstances, although anaerobic bacteria can enter the lower respiratory tract, due to normal blood supply to the respiratory mucosa, maintaining a redox potential of 150 mV is not conducive to its growth. However, when the redox potential is lowered below 150 mV due to the above reasons, the anaerobic bacteria can enter the tissue growth and reproduction. The phagocytic and bactericidal system activity is often reduced in the presence of hypoxia, ischemia, acidosis and bacterial metabolites, and is also conducive to the growth and reproduction of anaerobic bacteria.

2. The pathogenic role of bacteria

(1) Adhesion and adhesion: the first step in the anaerobic infection process. Anaerobic bacteria of different genus are attached to the surface of target cells by different mechanisms due to their special structures. For example, Bacteroides fragilis mainly uses pili and spores attached to mucosal epithelial cells, and the phytohemagglutinin-mediated mechanism is attached to galactose-containing target cell receptors by arginine, and is used by Propionibacterium Protease hydrolyzes immunoglobulins and complement, reducing the blockage of bacterial surface receptors by immunoglobulins and complement components.

(2) Invasive tissue: If the mucosal epithelial structure is intact, most anaerobic bacteria cannot directly invade the tissue except for necrosis, but in the case of impaired mucosal integrity, the anaerobic bacteria attached to the target cells rely on themselves. The produced protease and phospholipase C dissolve the mucosal epithelial cells into the tissue.

(3) Growth and reproduction: After the bacteria enter the tissue, whether the local infection can be formed depends on local metabolism, bacterial nutrition and the ability of the bacteria to resist the host's defense. If the tissue is degraded by ischemia and hypoxia, the degradation of carbohydrates and the activation of proteases and the release of amino acids, on the one hand, reduce the local pH and redox potential of the tissue, on the other hand, provide abundant nutrients for the anaerobic bacteria and promote their localization. Growing and breeding. In addition, bacteria entering the tissue can also produce a number of substances that resist the host's defense mechanisms. For example, Bacteroides fragilis protects itself from phagocytosis by phagocytic cells, and can also produce soluble substances such as succinic acid and other short-chain fatty acids to inhibit chemotaxis, phagocytosis and killing of polymorphonuclear leukocytes and macrophages. Many anaerobic bacteria also produce substances that inhibit and destroy humoral immunity in the host. For example, Bacteroides fragilis lipopolysaccharide can attenuate the conditioning effect of complement, and the proteolytic enzyme produced by Bacteroides melilatum degrades complement and immunoglobulin.

(4) Tissue damage: Anaerobic bacteria produce toxins, enzymes and soluble substances during the infection process. In addition to functioning at various stages, they can directly damage the structure of tissues and cells. For example, the toxin produced by Clostridium perfringens can dissolve red blood cells and tissue cells, causing hemolysis and tissue necrosis. Heparinase produced by Bacteroides decomposes heparin, promotes blood coagulation, and may cause thrombophlebitis. Production of collagenase, destruction of connective tissue, Bacteroides production of hyaluronidase, neuraminidase, DNase, etc. are related to the spread of disease and infection.

Pathological changes: the most common site of inhalation infection is the posterior segment of the right upper lobe, followed by the dorsal segment of the lower lobe. Often single-shot. The posterior segment of the left upper lobe is less involved and may be related to the anatomy and position of the bronchi. Hematogenous dissemination caused by multiple, no distribution, more common in the lungs of the two lower limbs. In the early stage, there are multiple small lesions, and then gradually merge. Direct diffusion is often the first to involve the lung or pleura closest to the primary lesion, such as the subarachnoid abscess first caused by empyema.

The histological changes of anaerobic pulmonary infection are similar to those of other bacteria. In the initial stage, if caused by inhalation, early bronchiole obstruction, alveolar edema and inflammatory cell infiltration, bronchial pneumonia, and blood-borne dissemination, bacterial embolism embolization of pulmonary arterioles, resulting in perivascular infiltration and knot Small infarcts in the nodular lung tissue, followed by a large number of inflammatory cell infiltration, the thrombus causes local tissue ischemia, promotes anaerobic infection, aggravates tissue necrosis, and develops necrotizing pneumonia and lung abscess. Necrotic pneumonia, mainly manifested as large leaf consolidation and tissue necrosis, which can form multiple small cavities less than 2cm, necrotic areas with neutrophil infiltration. When a large piece of necrotic tissue falls off, it becomes a lung gangrene. If the liquefied pus accumulates in the abscess, causing an increase in pressure, and finally rupture into the bronchi, coughing up a large amount of purulent sputum. If air enters the abscess, a fluid level appears in the abscess. Lung abscesses have large cavities, often single, and if they expand to surrounding tissues, they form several abscesses. If close to the pleura, localized fibrinous pleurisy can occur, causing pleural adhesions. A tension abscess located at the edge of the lung, if broken into the pleural cavity, can form a pus. If the bronchial drainage is not smooth, the necrotic tissue remains in the abscess, and the inflammation persists, then it becomes a chronic lung abscess.

an examination

Related inspection

Pus and wound infection specimens bacteriological examination blood routine

The clinical manifestations vary widely, and a few are acute courses, most of which are insidious onset.

Typical performance

1 aspiration pneumonia: have a history of primary disease and aspiration, rapid onset, sudden chills and high fever, body temperature of 39 ° C or more, with cough, cough mucus or mucus purulent, cough sputum is anaerobic infection Characteristics, but the literature reported that the disease cough skunk only accounted for 37.8%. Therefore, the pus is not odorous and the possibility of anaerobic infection cannot be ruled out. Inflammation involving the pleura can cause chest pain, and progressive dyspnea occurs as the lesion expands. Severe symptoms of poisoning may be associated with nausea, vomiting, bloating, and diarrhea. Signs: Less lesions, no abnormal signs. The lesions are large in scope and may have cyanosis, nasal winging and difficulty breathing. The auscultation of the lungs is voiced or real, the auscultation of the breath sounds is reduced, and sometimes the sound can be heard.

2 necrotizing pneumonia: This disease is characterized by the formation of many abscesses and necrosis with a diameter of less than 2cm. In severe cases, the rapid spread of the lung parenchyma produces large pieces of necrosis and shedding, and even forms a lung abscess. About 75% of patients have a history of aspiration, the patient is more severe, the body temperature is as high as 40 ° C, cough is severe, cough is more, 61% of patients cough skunk. When the lung abscesses, a large amount of pus sputum is coughed up to hundreds of milliliters per day. The patient has shortness of breath and cyanosis. Most of the lung examinations were voiced, the breath sounds were weakened, and the mortality rate was high. Chronic lung abscess patients have chronic cough, cough and sputum, repeated hemoptysis, often anemia, weight loss and other chronic consumption. At the time of physical examination, the affected side chest was slightly collapsed, the percussion was voiced, and the breath sound was reduced. Hematogenous disseminated lung abscesses have symptoms of systemic sepsis caused by chills and high fever caused by the primary lesion. Pulmonary symptoms, such as coughing and coughing, occur after several days to two weeks. Usually, there are not many sputum, and there is very little hemoptysis. Most of the signs are negative.

3 empyema: slow onset, often only 1 week to weeks after the onset of symptoms. The heat is high, up to 40 ° C, and the heat period is longer. Half of the cases showed a significant decrease in body weight. If the lung abscess secondary, cough is obvious, cough a lot of purulent sputum. If the abscess is directly spread, the dry cough and chest pain are obvious. The secretion of empyema is purulent, foul-smelling, sticky, forming many small abscesses, difficult to suck out.

2. Atypical performance

The onset is concealed, the symptoms are atypical, and there are often no symptoms of fever, cough, cough, or chest pain. The more common symptoms are: increased respiratory rate, shortness of breath, and general discomfort, body weight loss, loss of appetite, burnout, acute confusion, and mental dysfunction. There may also be a sudden deterioration of the underlying disease, or a slow recovery of the disease, for example: heart failure recurs or worsens during treatment. A small number of patients with gastrointestinal symptoms are more prominent, often manifested as nausea, vomiting, abdominal pain, diarrhea, anorexia, indigestion, etc., accompanied by respiratory symptoms. Signs: There are few typical physical signs, half of the patients can't hear the sound in the lungs, and 1/4 of the patients have no abnormal auscultation in the lungs. Even if you hear the sound, it is easy to be confused with chronic inflammation and heart failure.

The lung infection caused by anaerobic bacteria in the elderly has the following characteristics: 1 mostly have primary diseases and predisposing factors; 2 the course can be acute or chronic; 3 sputum and pleural effusion have bad odor; 4 infected lesions With necrotic tendency; 5 insidious disease, atypical symptoms; 6 specimens showed a large number of bacteria in the direct smear and normal bacterial culture was negative; 7 more complications, high mortality.

The diagnosis of anaerobic infections is mainly based on bacteriological examination. In the absence of anaerobic culture and other examination conditions or examinations, pulmonary infections occur in the following situations or are accompanied by anaerobic infections or anaerobic infections.

1 has a history of aspiration.

2 long-term application of aerobic bacteria antibiotics (such as aminoguanidine), but the effect is not significant.

3 Infections based on tissue necrosis such as lung cancer, bronchiectasis, mild pulmonary infarction, and open chest trauma.

4 with or secondary to oral, abdominal and gynecological infections.

5 septicemia or multiple migratory abscesses.

6 lung abscess cavity or chest cavity can be seen in the liquid and gas plane.

7 sputum or pus has a rotten stench or black color, showing red fluorescence under ultraviolet light.

The following points may be bacterial clues to anaerobic infections:

1 routine culture of negative sterile pus and puncture, smear Gram staining a large number of bacteria with consistent morphology; 2 culture gas production and stinky stench.

3 Anaerobic colony growth in sodium thioglycolate or agar deep.

4 can grow in medium containing 100 g/ml kanamycin or neomycin.

5 Young colonies producing Bacteroides melanosus can be red-fluorescent by ultraviolet light irradiation. The clinical manifestations of anaerobic pulmonary infections are not characterized by differentiation.

Differential diagnosis

Pulmonary edema and pathological state of increased lung water content caused by fluid exchange dysfunction between blood vessels and tissues in the lung, regardless of the cause of pulmonary edema, the respiratory pathophysiology is substantially the same, that is, the liquid is stored in the lung and Gas exchange disorders, lung compliance decreased, ventilation / blood flow imbalance, leading to hypoxemia. The clinical manifestations were sudden onset, difficulty in breathing, hair set, frequent cough, a lot of foamy sputum, diffuse wet warm sounds in both lungs, and X-ray showed a butterfly-shaped blushing shadow on both lungs. Pulmonary edema can seriously affect respiratory function, which is a common respiratory emergency. The target of treatment is aimed at pathophysiology and basic diseases. Early diagnosis and treatment play a decisive role in the prognosis and outcome of pulmonary edema.

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