Morganiipneumonia

　　1. Etiology

　　Morganella, belonging to the genus Morganella of the family Enterobacteriaceae, was discovered by Morgan in 1906. It was previously known as Morgan's proteus. It is widely distributed in nature and commonly found in the intestines of humans and animals. In recent years, with the development of biology, through the study of its DNA, it has been found that the guanine and cytosine content in the DNA molecule of Morganella proteus is significantly higher than that of other proteus. Therefore, it has now been separated out and named as the genus Morganella. It has now been found to include Morganella and Morganella biofilm. The distinction between the genus Morganella and the genus Proteus and the genus Pseudofluminicola.

　　1. Morphology and Staining

　　Morganella morganii is a non-spreading, unicellular organism. It is a Gram-negative bacillus with blunt ends. It often has variant forms, sometimes spherical, sometimes long and curved or long filaments (10-30 μm). It has no capsule or spore, has motility, and has peritrichous flagella and pili. Its hemagglutination and adsorption are not inhibited by mannose.

　　2. Culture and Biochemical Reactions

　　Morganella morganii is an anaerobic or facultative anaerobic bacterium. The optimal growth temperature is 34-37°C, and it can also grow within the range of 10-45°C, and can be killed in 1 hour in water at 55°C. The culture requirements are not high. It grows well on general culture media and can grow on potassium cyanide (potassium cyanide) medium. The growth in broth culture media is uniform and concentrated, with a film on the surface. The colonies on SS plates are circular, flat, semi-transparent, and easy to confuse with other enteric pathogens. The culture has a special odor, can hemolyze, and can produce indole. The methyl red reaction is positive, and the VP reaction is negative. It can rapidly hydrolyze urea without forming hydrogen sulfide, without liquefying gelatin. It lacks lysine decarboxylase and arginine dihydrolyase, but can produce ornithine decarboxylase and phenylalanine deaminase. It does not ferment lactose, sucrose, mannitol, glucoside, salicylate, helleborine alcohol, inositol, sorbitol, arabinose, raffinose, and rhamnose. When fermenting glucose, 80% of the strains produce gas.

　　3. Antigen and Typing

　　Morganella morganii has 34 'O' serogroups and 25 'H' antigens. It can be divided into 66 serotypes by serotyping the bacterial body antigens and then typing by flagellar antigens.

　　2. Pathogenesis

　　Morganella morganii is a conditional pathogen. It is not pathogenic in the human intestinal tract, but can cause pneumonia when it leaves the intestines and enters the lungs. Its pathogenesis is related to its endotoxin and bacterial virulence. Animal experiments show that injecting 0.5-1.0 ml of virulent strains into mice intraperitoneally can cause death in mice. It is believed that the polysaccharide component may be the main related component of its virulence. In addition, Morganella morganii can also secrete hemolysin, and the bacteria have many flagella, which may also play an important role in the respiratory tract. Morganella morganii pneumonia is often an acquired hospital infection and is more common in the elderly. Any condition that causes immune function damage to the body may become a predisposing factor for infection. Pre-existing serious underlying diseases such as cancer, diabetes, etc.; long-term use of corticosteroids, immunosuppressants, and chemotherapy and radiotherapy after tumor patients; certain traumatic examinations and treatments, such as catheterization, venipuncture, joint puncture, major surgery, especially respiratory department treatment measures such as tracheal intubation, tracheotomy, mechanical ventilation, and nebulization inhalation, etc. In addition, long-term use of broad-spectrum antibiotics can lead to dysbiosis of the normal flora, which is conducive to the colonization of Morganella morganii in the upper respiratory tract. When the body's resistance is reduced, it can enter the lower respiratory tract and cause disease, causing primary or secondary Morganella morganii pneumonia. The pathological changes of Morganella morganii pneumonia are lobular or segmental distribution, with destruction of alveolar tissue forming small abscesses. It can also present as bronchopneumonia.

　　1. Pneumothorax

　　It refers to the entry of gas into the pleural cavity, causing a pneumothorax state, known as pneumothorax. It is usually divided into three categories: spontaneous pneumothorax, traumatic pneumothorax, and artificial pneumothorax. Spontaneous pneumothorax is caused by the rupture of lung tissue and visceral pleura due to lung diseases, or due to the rupture of small bubbles and bullae near the surface of the lung, with air in the lung and bronchus entering the pleura.

　　2. Hemorrhage

　　It mainly refers to the escape of red blood cells from blood vessels or the heart, known as hemorrhage. The escaped blood entering the body cavity and tissues is called internal hemorrhage, and the blood flowing out of the body is called external hemorrhage. Hemorrhage can be divided into two types according to the mechanism of blood escape:rupture hemorrhage and leakage hemorrhage.

　　1. Symptoms

　　Similar to general acute bacterial pneumonia, such as fever, chills, aversion to cold, cough, expectoration of sputum or white sputum, chest pain, etc. However, for secondary pneumonia caused by pre-existing lung diseases, the symptoms are atypical and may manifest as respiratory failure, heart failure, or exacerbation of symptoms of the primary disease, or high fever, increased sputum, and severe patients may appear symptoms of infectious shock, sepsis, and other complications.

　　2. Signs

　　There may be moist rales in both lungs. When the inflammatory infiltration appears in the segment or lobe of the lung, there is an increase in the vibration of the voice at the corresponding segment or lobe of the lung.

　　It is necessary to actively treat the primary disease, improve the body's resistance, and strictly implement aseptic techniques for various invasive examinations and treatments. It is necessary to actively treat and isolate patients to prevent cross-infection. Strengthening physical exercise, enhancing physical fitness, reducing risk factors such as smoking and alcoholism, and improving one's own immunity are effective ways to prevent. It is very important to actively prevent bacterial infections and increase resistance, and not to eat spicy and irritating foods.

　　First, routine examination

　　1. Blood routine

　　The peripheral blood leukocytes and neutrophils increase.

　　2. Gram staining of sputum smear

　　A large number of Gram-negative bacilli were found.

　　3. Blood gas analysis

　　In severe cases, PaO2 may decrease, and in some patients, especially those with chronic obstructive pulmonary disease, PaCO2 may increase, and there may be varying degrees of acid-base imbalance.

　　4. Blood biochemical examination

　　In sepsis, if there is liver or kidney damage, transaminases, BUN, and Cr can increase.

　　Second, pathogenetic examination

　　1. Blood culture

　　When Morganella pneumonia is accompanied by bacteremia or sepsis, blood culture shows the growth of Morganella, and the positivity rate of blood culture in blood源性Morganella pneumonia is generally high. However, in recent years, it has been found that Morganella can also change into L-type bacteria after the application of antibiotics, and routine blood culture may be negative, which should be noted.

　　2. Sputum culture

　　This method is simple, convenient, and easy for patients to accept, but it is prone to contamination by pharyngeal bacteria. It is generally believed that sputum coughed out from the deep lung of the patient should be collected, washed, homogenized, and quantitatively examined before culture, which can greatly improve accuracy.

　　3. Direct collection of lower respiratory tract secretions for culture

　　This method has certain trauma and requires certain conditions, but it is helpful for the diagnosis of Morganella morganii pneumonia, especially hospital-acquired pneumonia, because it avoids or reduces upper respiratory tract bacterial contamination, which is more accurate. Clinically, a method can be selected based on the advantages and disadvantages of different methods, hospital equipment, and the technical level of doctors.

　　(1) Transcervical membrane puncture: Insert a sterile thin plastic catheter to aspirate secretions from the lower respiratory tract. The advantage is that it reduces pharyngeal bacterial contamination, but it has certain trauma.

　　(2) Under X-ray chest fluoroscopy, lung tissue and secretions from the lesion site of pneumonia are aspirated and cultured through chest wall puncture, with a high positive rate and completely avoiding upper respiratory tract bacterial contamination, but it is more traumatic.

　　(3) Sputum from the lower respiratory tract is collected through fiberoptic bronchoscopy: This method is relatively safe and can collect specimens from the lesion site under direct vision, but requires certain equipment.

　　4. Other body fluid cultures

　　Midstream urine bacterial culture, bone marrow bacterial culture, pleural fluid, urine, bone marrow or wound secretion culture.

　　In addition to routine treatment, attention should also be paid to the following aspects in diet for patients with Morganella morganii pneumonia: diet should be light, eat more vegetables and fruits, rationally match the diet, and ensure adequate nutrition. In addition, spicy and刺激性 food should be avoided.

　　I. Treatment

　　The treatment principles are the same as those for other Gram-negative bacillary pneumonia, select sensitive antibiotics, maintain an unobstructed airway, correct respiratory failure, protect the heart, kidney, liver, and brain function, actively treat primary underlying diseases and complications, and strengthen supportive treatment.

　　1. Antibiotic treatment

　　Antibiotic therapy is the key to the treatment of Morganella morganii pneumonia. However, in the past 10 years, the number of drug-resistant strains of Morganella morganii has been increasing. It has been found that this bacterium has resistance to commonly used drugs such as gentamicin, tobramycin, cefoxitin (thienamycin), carbenicillin, ticarcillin, polymyxin, and chloramphenicol. Morganella morganii can produce inducible β-lactamase, which is mediated by a group of AmP genes on the chromosome, thus leading to a high and widespread resistance rate. Third-generation cephalosporins and quinolone antibiotics have strong antibacterial activity against this bacterium. Commonly used drugs include: aztreonam (1.0-2.0g/time), intravenous injection, 2-3 times/day; cefminox sodium (2.0-6.0g/day), divided into 2-3 doses for intravenous infusion; cefoperazone (ceftizixime) (4.0-10.0g/day), divided into 2-4 doses for intravenous infusion; cefonicid (1.0-2.0g/day), divided into 1-2 doses, intravenous injection; ceftriaxone (1.0-2.0g/time), intravenous injection, 1-2 times/day; cefotaxime (1.0-2.0g/time), intravenous injection, 2-3 times/day. Ciprofloxacin 200-400mg/time, intravenous infusion, 2 times/day; cefoperazone sodium (cefoperazonesodium) (2.0-6.0g/day), divided into 2 doses for intravenous injection.

　　In recent years, the use of broad-spectrum penicillin plus beta-lactamase inhibitors to treat drug-resistant Morganella morganii has become widespread. Commonly used ones include: Compound ticarcillin 9.6g/d, administered intravenously in three divided doses; or imipenem (imipenem) 2.0-3.0g/d, administered intravenously in three divided doses. To improve the effectiveness of antibiotic treatment, attention should be paid to the following points when selecting antibiotics in clinical practice: ① Ask about the patient's history of antibiotic use and whether there is resistance. ② Select sensitive antibiotics based on drug sensitivity, empirical treatment should use third-generation cephalosporins or quinolone antibiotics, and amikacin can be combined when necessary. ③ The course of treatment should be long, and the dose should be sufficient, especially for hospital-acquired infections, usually 3-4 weeks. ④ Regularly check for sputum bacteria and drug sensitivity to adjust antibiotics.

　　2. Keep the respiratory tract unobstructed

　　Correct hypoxia, protect the heart, liver, kidney, and lung function by using bronchodilator drugs, expectorants, encourage patients to cough, expectorate, breathe oxygen, correct oxygen deficiency, and prevent damage to the heart, liver, and kidney function.

　　3. Strengthen the treatment of the primary disease and complications and nutritional support treatment

　　Active treatment of the primary disease, complications, and strengthening nutritional support treatment, appropriate use of fresh plasma, human serum albumin, human immune globulin, granulocyte transfusion, and adequate supply of calories needed by the patient.

　　II. Prognosis

　　The prognosis of the disease is related to age, existing underlying diseases, neutropenia, bacteremia, and other factors.