Citrobacter pneumonia

　　1. Etiology

　　Citrobacter belongs to the genus Citrobacter of the family Enterobacteriaceae. It was first described by Werkman and Gillen in 1932. It includes three species, namely Citrobacter variabilis, Citrobacter freundii, and Citrobacter cinnamoni. In 1979, it was found that Citrobacter cinnamoni has a biological type, known as Citrobacter cinnamoni biological type-1. They are all related to human diseases, and the differences between them are shown in Table 2.

　　1. Morphology and staining:Citrobacter is a motile, non-spore-forming, Gram-negative aerobic or facultative anaerobic bacterium.

　　2, Culture and biochemical reactions:Citrobacter can grow on Simmons citrate broth. It can grow in culture media containing KCN (potassium cyanide). It produces acid in Jordoni tartarate broth. Flavobacterium citricum can produce hydrogen sulfide. Citrobacter can ferment glucose and mannitol, usually producing gas. In addition, it can also ferment sorbitol, arabinose, rhamnose, maltose, xylose, levulose, fibrous dextrin, and glycerol. It reduces nitrates. It does not ferment pentanol and inositol. The fermentation capacity of lactose, sucrose, and salicylic acid varies among strains. It cannot deaminate lysine and phenylalanine. It has no DNAase. It does not liquefy gelatin. Most strains can slowly produce urease. The indole reaction is negative. MR (methyl red) reaction is positive. V-P reaction is negative. The nitrogalactoside galactosidase (ONPG) test is a positive reaction.

　　3, Antigen and isolation:The characteristics of Citrobacter are similar to those of Salmonella, among which some bacteria have Vi antigen and are called Paratyphi Salmonella. The main members of this group of strains were once called Basel-Darling Paratyphi Salmonella. And as a species of the Escherichia coli genus (Flavobacterium). Through the study of the Basel-Darling Paratyphi population, 32 "O" groups and 75 "H" antigens were established. Later, Sedlak and Slajsova discovered 10 new "O" groups, some of which were originally classified as Escherichia. Currently, there are more than 40 "O" groups. The "O" antigen of this group of strains has cross-antigenicity with some "O" groups in the Salmonella genus and the Escherichia coli genus.

　　Second, pathogenesis

　　The pathogenicity of Citrobacter is not certain. Some believe that the pathogenicity of the bacterium is weak, while others believe that some strains have strong virulence. In animal experimental models, it was found that the virulence of the atypical Citrobacter that causes human meningitis is significantly greater than that of the strain that does not cause meningitis, and the strains that cause meningitis in humans have outer membrane proteins. At the same time, Citrobacter produces endotoxins. These are all related to the pathogenesis. In addition, the pathogenicity of Citrobacter is related to the host's condition, ciliary movement and clearance function, tracheal intubation, tracheotomy, fiberoptic bronchoscopy, airway suction, oxygen inhalation, mechanical ventilation, and nebulizer inhalation. These are all conducive to the colonization of Citrobacter in the upper respiratory tract, or direct inhalation into the lungs, or hematogenous dissemination to the lungs. It can cause primary Citrobacter pneumonia or secondary Citrobacter pneumonia. Pathological changes are mainly manifested as bronchopneumonia, and there may be destruction of the alveolar wall to form small abscesses and focal hemorrhage.

　　Severe Citrobacter pneumonia can cause the following complications due to bacteremia or sepsis: infectious shock, respiratory failure, acute myocarditis, endocarditis, toxic hepatitis, acute renal failure, lung abscess, empyema, systemic multiple abscesses, DIC, etc. At this time, there may be symptoms and signs of corresponding damaged organs. At the same time, the condition worsens, the mortality rate increases significantly, and the prognosis is poor.

　　1. Symptoms

　　Citrobacter pneumonia is mostly hospital-acquired pneumonia. It is reported that 75% of patients have a primary disease, especially common in hematological malignant tumors. Community-acquired (out-of-hospital) pneumonia is less common. For patients with primary Citrobacter pneumonia without primary pulmonary infection disease, the clinical manifestations are similar to those of general acute bacterial pneumonia, with main symptoms such as chills, fever, cough, expectoration of yellow sputum or white sticky sputum, chest pain, dyspnea, and some patients may have abdominal pain, diarrhea, and other gastrointestinal symptoms. Since Citrobacter pneumonia can be septicemia or septicemic pneumonia, at this time, systemic toxic symptoms are more obvious. However, for secondary Citrobacter pneumonia caused by chronic obstructive pulmonary disease and other primary diseases, the symptoms may not be typical, and the symptoms of pneumonia may be masked by the primary disease. Patients may present with high fever, increased expectoration of yellow sputum, respiratory failure, heart failure, or exacerbation of the primary disease. Some patients may have a severe condition and poor response, and may not show pneumonia symptoms until post-mortem examination.

　　2. Signs

　　Citrobacter pneumonia may have increased respiratory sounds, unilateral or bilateral lower lobe moist rales. When lobar or segmental consolidation occurs, there may be increased palpation, dullness, and bronchial breath sounds or moist rales in the corresponding lobe or segment. If there is pleural effusion, there may be decreased palpation and respiratory sounds on the effused side. In addition, some patients may have tachypnea, cyanosis, hypotension, jaundice, and other symptoms.

　　The treatment of Citrobacter pneumonia is relatively difficult, therefore, prevention is very important. It is necessary to enhance the body's resistance, prevent the occurrence of Citrobacter pneumonia. It is necessary to actively treat the primary disease; correctly master the indications for the use of antibiotics and corticosteroids; keep the air in the ward fresh and clean, especially for intensive care units, neonatal rooms, elderly wards, and other susceptible patients' rooms. For patients receiving chemotherapy and radiotherapy for tumors, kidney transplant recipients, and others, it is necessary to use ultraviolet radiation and floor wet wipes for disinfection regularly; strict aseptic procedures should be followed for all diagnostic and therapeutic procedures, especially for respiratory treatment equipment; timely treatment of patients and strengthening of nursing care should be carried out to prevent cross-infection.

　　First, routine examination

　　1. Blood routine examination:The peripheral blood white blood cells and neutrophils may increase, but in severe cases, they may decrease.

　　2. Routine sputum smear Gram staining:A large number of Gram-negative bacilli can be found.

　　3. Arterial blood gas analysis:In severe cases, PaO2 may decrease, and some patients may have elevated PaCO2, and may have varying degrees of acid-base imbalance.

　　4. Blood biochemical examination:Some patients may have elevated blood urea nitrogen, creatinine, alanine aminotransferase, bilirubin, and other indicators.

　　Second, pathogenic examination

　　1. Blood culture:In the case of bacteremia, Citrobacter pneumonia often has positive blood culture. Generally, the positive rate of blood culture in blood源性Citrobacter pneumonia is high, and sometimes the blood culture is negative while the bone marrow culture is positive.

　　2. Sputum culture:This method is simple, convenient, and easy for patients to accept. However, it is prone to contamination by upper respiratory tract pathogens, which may affect the accuracy of the results. Therefore, it is required to select sputum coughed out from the deep lung of patients after cleaning the mouth with 3% hydrogen peroxide, and then to cultivate the sputum after cleaning and homogenizing the quantitative examination, which can greatly improve the positive rate and the accuracy of diagnosis.

　　3. Direct collection of lower respiratory tract secretion culture:Avoids upper respiratory tract bacterial contamination, is relatively accurate, but has some traumatic nature. Clinically, various methods can be selected according to their advantages and disadvantages, hospital conditions, and the technical level of doctors to improve the diagnostic rate of pathogens, especially for hospital-acquired Citrobacter pneumonia, it should strive to use the following methods to send lower respiratory tract secretions for culture.

　　(1) Aspirate lower respiratory tract secretions by inserting a thin plastic catheter through the cricothyroid membrane puncture, the advantages are that it does not pass through the mouth, nose, or pharynx, reducing contamination, but there is some trauma, and accidental puncture may cause subcutaneous emphysema, hemorrhage, etc.

　　(2) Under X-ray chest fluoroscopy localization, aspirate lung tissue and secretions from the lesion site through chest wall puncture, the advantages are that it completely avoids the contamination of upper respiratory tract secretions, but the disadvantages are that the trauma is large, and complications such as pneumothorax and hemorrhage can reach 20%, but the bacterial detection rate reaches 84%.

　　(3) Obtain lower respiratory tract secretions through fiberoptic bronchoscopy: A. Directly aspirate secretions for culture through fiberoptic bronchoscopy; B. Perform bronchoalveolar lavage fluid quantitative culture through fiberoptic bronchoscopy, with sensitivity and specificity of 90% and 97%, respectively, and for those who have received antibiotic treatment, the sensitivity and specificity are 78% and 96%, respectively; C. Perform bronchoalveolar lavage culture through fiberoptic bronchoscope导管; D. The fiberoptic bronchoscope has a double-lumen catheter specimen brush sampling culture, which can prevent contamination of the specimen; E. Under X-ray chest fluoroscopy localization, perform lung biopsy through fiberoptic bronchoscopy, which can be used for diagnosis and differential diagnosis, but it is traumatic.

　　4. Other body fluid cultures:Such as pleural effusion, cerebrospinal fluid, urine, etc. for culture.

　　Through the above methods of examination, positive results of Citrobacter can be obtained, and for the guidance of treatment, it should be simultaneously added with drug sensitivity test. In addition, some secondary Citrobacter pneumonia, in addition to cultivating Citrobacter, there are other Gram-negative or Gram-positive bacteria growing.

　　5. X-ray manifestations:The chest X-ray of Citrobacter pneumonia mainly shows bronchopneumonia, which can be focal infiltration shadow or diffuse bilateral lower lung infiltration shadow, small lung abscess, pleural effusion and empyema are less common.

　　First, dietary therapy for Citrobacter pneumonia

　　1. Stir-fried carp with celery:Raw materials:鲤鱼250 grams, fresh celery 50 grams, starch, ginger slices, garlic slices, soy sauce, sugar, vinegar, monosodium glutamate, rice wine, pickled chili peppers, and cooking oil as needed. Preparation: Cut the carp into shreds, cut the celery into segments, and mix soy sauce, sugar, vinegar, monosodium glutamate, rice wine, salt, and starch with stock to make a sauce. Heat the wok over high heat, add oil and heat to 5成热, add the fish shreds and stir-fry until they separate, drain off the excess oil, and add ginger slices and pickled chili peppers. Stir-fry the celery segments until fragrant, then pour in the sauce, add bright oil, and turn off the heat. Benefits: Carp has the effects of clearing heat and detoxifying, diuretic and reducing swelling, and cough-suppressing and Qi-promoting; celery has the effects of calming the liver and clearing heat, dispelling wind and moistening, and nourishing the spirit and promoting Qi. Eating carp and celery together is suitable for the auxiliary treatment of acute and chronic pneumonia.

　　2. Rabbit meat and mushroom shreds:Ingredients: 100 grams of cooked rabbit meat, 50 grams of mushrooms, 25 grams of scallion, chili oil, soy sauce, vinegar, sugar, sesame oil, sesame paste, Sichuan pepper powder, and monosodium glutamate. Preparation: slice the cooked rabbit meat and scallion, and cook the mushrooms. Place the scallion and mushrooms at the bottom, cover with rabbit slices, and serve in a dish. Dilute the sesame paste with soy sauce in stages, mix the sesame oil evenly to make a sauce, and pour it over the rabbit slices. Effect: rabbit meat has the effect of clearing heat and detoxifying, invigorating the spleen and benefiting the Qi, removing dampness and cooling the blood, and promoting bowel movements; mushrooms have the effect of detoxifying and moistening the dryness, invigorating the spleen and benefiting the Qi, and stopping diarrhea. Eating rabbit meat and mushrooms together is suitable for treating acute pneumonia.

　　3. Quail and lily soup:Ingredients: 1 quail, 25 grams of lily, ginger, scallion, monosodium glutamate, and fine salt. Preparation: kill the quail, remove the feathers, feet, and internal organs, wash it, put it in boiling water for a brief scald, remove it and cut it into pieces; separate the lily petals, wash them, and set aside. Wash the ginger and scallion, crush the ginger, and cut the scallion into sections. Place the pot on a high heat, add some water, add the quail, bring to a boil, add lily petals, ginger pieces, and scallion sections, then turn to low heat and simmer until the quail is cooked. Add salt and monosodium glutamate, simmer for several minutes, and serve in a soup bowl. Effect: quail meat has the effect of benefiting the five internal organs, invigorating the liver and lungs, clearing heat and promoting diuresis, and stopping diarrhea; lily has the effect of moistening the lungs and stopping cough, nourishing the Yin and clearing heat, calming the mind. Eating both together is suitable for acute and chronic pneumonia.

　　4. Lean meat and cabbage soup:Ingredients: lean meat and cabbage heart each 100 grams, a little ginger, garlic, salt, monosodium glutamate, and chicken oil. Preparation: slice the lean meat, wash and slice the cabbage, put it in boiling water, remove it when it is just cooked, rinse it clean in cold water, drain the water and set aside; place the pot on a high heat, add chicken oil and heat to five degrees, add garlic and stir-fry until golden, then add the lean meat and stir-fry together, add fine salt, cook in the soup, then add the cabbage heart and bring to a boil, add monosodium glutamate and it is ready to eat. Effect: lean meat has the effect of invigorating the middle-jiao and benefiting the Qi, moistening the intestines and promoting bowel movements; cabbage is sweet and has the effect of clearing heat and detoxifying, resolving phlegm and stopping cough, relieving restlessness and promoting bowel movements. Eating lean meat and cabbage together is suitable for acute and chronic pneumonia.

　　Two, what foods are good for the body in Citrobacter pneumonia?

　　Foods should be high in nutrition, light, and easy to digest.

　　1. Fluids, especially fruit juice.

　　2. Fresh fruits and vegetables.

　　3. Foods rich in vitamin A, such as oily fish and eggs.

　　Three, what foods should be avoided for Citrobacter pneumonia?

　　1. Avoid spicy and greasy foods:Do not eat large fish, meat, and overly greasy products. Patients with pneumonia should not add spices such as chili, pepper, mustard, and Sichuan pepper to their diet. Quit smoking and drinking.

　　2. Unsuitable for eating sweet and warm fruits:Such as peaches, apricots, plums, oranges, etc.

　　3. Avoid cold and cool foods:All kinds of ice drinks; fruits with cold and cool properties: including watermelons, pears, bananas, kiwis, etc.

　　4. Avoid eating sour foods:Such as vinegar, sauerkraut, pickled vegetables, and hawthorn, prune, sour tangerine, etc.; astringent foods: such as white sesame seeds, lotus root nodes, and unripe persimmons, hawthorn, etc.

　　(The above information is for reference only, please consult a doctor for details.)

　　1. Treatment

　　The principle of treatment is to select sensitive antibiotics to kill pathogens, enhance the drainage of bronchial secretions, improve lung gas exchange, strengthen the treatment of the primary disease and nutritional support, and prevent and treat complications.

　　1. Antibiotic treatment:Early selection of sensitive antibiotics is the key to treatment. Antibiotics that were effective against Citrobacter in the past, such as gentamicin, kanamycin, chloramphenicol, ampicillin (ampicillin), carbenicillin (carbenicillin), cefotetan, pipemidic acid, and sulfonamide drugs, have now been found to have drug resistance.

　　In recent years, the number of drug-resistant bacteria has increased year by year, and they are multidrug-resistant. Especially, the phenomenon of drug resistance in hospital-acquired infections is more common. Citrobacter can produce inducible β-lactamase, which is mediated by a group of Amp genes on the chromosome, and can transfer the drug resistance phenomenon (R+ factor) in 50% of Citrobacter, thus resulting in a wide range of drug resistance rates. Not only are they resistant to the first-generation cephalosporins, but also to the third-generation cephalosporins. The resistance rates to ceftriaxone (ceftriaxone), cefoperazone, and cefotaxime (cefotetan carboxime) are 36%, 41%, and 37% respectively. However, it is now believed that third-generation cephalosporins and quinolone antibacterial drugs still have strong antibacterial activity against Citrobacter. Clinical studies have found that different species and strains of Citrobacter have significant differences in sensitivity to antibiotics. Therefore, the use of antibiotics should be based on drug sensitivity, and third-generation cephalosporins or quinolone antibacterial drugs should be selected. Before drug sensitivity testing, empirical treatment can be used with amikacin (gentamicin) combined with a third-generation cephalosporin or quinolone antibacterial drug. The antibiotics that can be used include: ceftriaxone (ceftriaxone) 1.0-2.0g/time intravenous injection, 1-2 times/d, cefoperazone (cefoperazone) 2.0-4.0g/time intravenous injection, 2-3 times/d, cefotaxime (cefotetan carboxime) 1.0-2.0g/time intravenous injection, 2-3 times/d, ciprofloxacin 200-400mg/time intravenous injection, 2 times/d, aztreonam 1.0-2.0g/time intravenous injection, 3 times/d, amikacin (gentamicin) 15mg/(kg·d), divided into 2-3 times intravenous injection, cefotetan 2.0-4.0g/d, divided into 2 times intravenous injection, cefprozil (cefprozil) 2.0-4.0g/d, divided into 2 times intravenous injection, cefotetan (cefotetan) 300-600mg/d, divided into 3 times oral administration, cefmenoxime 2.0-4.0g/d, divided into 2 times intravenous injection.

　　A broad-spectrum penicillin combined with a potent β-lactamase inhibitor can be used to treat carbapenem-resistant strains of Citrobacter. Commonly used preparations include amoxicillin/clavulanate potassium (Augmentin) 375mg orally, 3 times daily, or 1.0g intravenously, 3 times daily, ticarcillin/clavulanate potassium (Timentin) 9.6g daily, administered in 3 divided intravenous doses, sulbactam (Unasyn) 4.5 to 9.0g/d, administered in 2 divided intravenous doses, and piperacillin/triazolone (8:1) and cefoperazone/sulbactam (1:1) can also be used for treatment. The newly developed cephalosporin FK037 has a MIC90 of 6.25μg/ml against Flavobacterium citrigena, showing strong antibacterial activity against Citrobacter strains resistant to third-generation cephalosporins. Imipenem (Imipenem, combined imipenem) can also be used for the treatment of Citrobacter strains resistant to third-generation cephalosporins. For moderate infections, imipenem (imipenem) is administered intravenously at a dose of 500mg, 3 times daily, and for severe infections, 2.0 to 4.0g/d, administered in 3 to 4 divided intravenous doses. In order to improve the therapeutic effect of antibiotics for Citrobacter pneumonia, the following points should be noted when using antibiotics:

　　(1) Before using antibiotics, send blood, sputum, and other samples for bacterial culture and drug sensitivity tests, and inquire about past use of antibiotics, types, dosages, methods of use, and efficacy, in order to consider the possibility of drug-resistant strains.

　　(2) Regularly check bacteria and drug sensitivity, adjust antibiotics according to the results of drug sensitivity and therapeutic response. For those without drug sensitivity results, amikacin can be used in combination with a third-generation cephalosporin or quinolone antibiotic.

　　(3) Adhere to the principles of early, adequate, intravenous medication, and sufficient course of treatment. For critically ill patients, combined drug therapy should be used, and for citrus acid杆菌 pneumonia with sepsis, 4-6 weeks should be used. But pay attention to liver and kidney function.

　　(4) For patients with neutropenia, piperacillin/triazobutane combined with amikacin (gentamicin) or cefoperazone (carbapenem) 2.0-6.0g/d, administered twice, or imipenem (imipenem) can be used for treatment.

　　2. Promote expectoration and correct hypoxia:For citrus acid杆菌 pneumonia, it is encouraged to cough and expectorate sputum, and for sputum that is sticky, nebulization inhalation can be used to expectorate sputum while supplementing water. Use bronchodilators and expectorants to keep the respiratory tract unobstructed. Oxygen therapy corrects hypoxemia, and prevents and treats heart, kidney, liver, and brain failure.

　　3. Strengthen the treatment of primary disease, complications, and nutritional support:For citrus acid杆菌 pneumonia with primary disease and complications, active treatment should be given, and sufficient nutrition should be supplemented. For severe patients, fresh plasma, human serum albumin, human serum immunoglobulin (IgG), and human white blood cells can be administered to those with granulocytopenia. And strengthen nursing care, prevent cross-infection.

　　II. Prognosis

　　The prognosis of this disease is poor. For those with sepsis, shock, renal failure, granulocytopenia, infants and the elderly, mixed infection with multiple bacteria, and those with severe underlying diseases, the prognosis is poor.