Pseudomonas aeruginosa infection

Introduction to Pseudomonas aeruginosa infection Pseudomonas aeruginosa, also known as Pseudomonas aeruginosa, is a genus of Pseudomonas and is an aerobic Gram-negative bacillus. Pseudomonas aeruginosa infections often occur in areas of persistently moist lesions, especially in the umbilical, burned surfaces of infants, and often occur in impregnated toe, external auditory canal, and auricle. When the body's immune function is impaired or defective, it can cause serious and even fatal infections; patients after surgery or after some treatment operations (tracheal incision, retention of catheters, etc.) are also susceptible to this infection, so It is one of the important pathogens for infection in hospitals. basic knowledge Sickness ratio: 0.0001% Susceptible people: no specific population Mode of infection: non-infectious Complications: adult respiratory distress syndrome

Causes of Pseudomonas aeruginosa infection

Pseudomonas aeruginosa infection (90%)

Pseudomonas aeruginosa is a Gram-negative aerobic bacterium, which is found in soil, dust, water and a few human intestinal tracts. It can also temporarily parasitize the skin, mainly in the anus, genital area, armpits and external auditory canal. Under normal circumstances, it generally does not cause disease. When the body's resistance is low, it can cause illness and can cause death. Typical strains produce blue-green pyocyanin and yellow-green pyocyanin. Systemic Pseudomonas aeruginosa infection can cause sepsis. Patients have fever, jaundice, splenomegaly, and pneumonia and urinary system can occur. Infection, meningitis. Pseudomonas aeruginosa infections often occur in areas of persistently moist lesions, especially in the umbilical, burned surfaces of infants, and often occur in impregnated toe, external auditory canal, and auricle.

Pathogenesis

Pseudomonas aeruginosa has a variety of products that are pathogenic, and endotoxin is a key factor in causing sepsis syndrome or systemic inflammatory response syndrome (SIRS), but due to the low endotoxin content of Pseudomonas aeruginosa, Therefore, the effect on the pathogenesis is smaller than that of Enterobacteriaceae. The exotoxin A (ExoA) secreted by it is the most important pathogenic and lethal substance. It is activated and activated to enter the sensitive cells to play a toxic role. Obstructed and cause tissue necrosis, causing local or systemic disease processes. Animal models indicate that hepatocyte necrosis, pulmonary hemorrhage, renal necrosis and shock may occur after injection of exotoxin A into the animal. For example, injection of exotoxin A antibody against P. aeruginosa The bacterial infection has a protective effect, Pseudomonas aeruginosa can still produce protease, and the virulence is greatest when exotoxin A and elastase are present simultaneously; the extracellular enzyme S is a different from exotoxin produced by Pseudomonas aeruginosa. A's ADP ribosyltransferase, which can destroy the cytoskeleton, thereby promoting the invasion and spread of Pseudomonas aeruginosa. Patients infected with Pseudomonas aeruginosa producing this enzyme may have liver function damage. Astragalus, in addition, such as alkaline protease, phosphatase, cytotoxin and other Pseudomonas aeruginosa exotoxin are often the cause of tissue destruction, bacterial dissemination, Pseudomonas aeruginosa is a conditional pathogen, intact skin is natural Barriers, high-energy toxins can not cause lesions. Normal healthy people contain opsonin and complement in serum, which can help neutrophils and monocyte macrophages to phagocytose and kill Pseudomonas aeruginosa, so it is not easy to cause Disease; however, such as changing or damaging the host's normal defense mechanisms, such as skin mucosal damage, indwelling catheter, tracheotomy, or immune mechanism defects such as neutropenia, hypoproteinemia, various tumor patients, application of hormones or Antibiotics in hospital environments can often develop from infection to infection, burns under eschar, infant and child skin, umbilical cord and intestines, the urinary tract of the elderly, often the primary focus of Pseudomonas aeruginosa sepsis or Invade the portal.

Pseudomonas can be divided into five major types based on their RNA/DNA homology. Pseudomonas aeruginosa is a representative species, and Pseudomonas aeruginosa produces blue-green on agar plates. Pyocyanin, which forms a green pus when infected with wounds. This bacterium is a non-capsulated, non-spore, Gram-negative bacterium that can move, has different forms, is arranged in pairs or short-chain, and is an aerobic bacterium. The suitable growth temperature is 37 ° C, and the pathogenic Pseudomonas aeruginosa can still grow at 42 ° C. According to this, it can be identified with Pseudomonas fluorescens. The growth of the bacteria is not high, and the bacterial O antigen has Two components, one is endotoxin protein (OPE), which is a protective antigen, and the other is an ester polysaccharide, which is specific. According to its structure, Pseudomonas aeruginosa can be divided into 12 serotypes. Phage or Pseudomonas aeruginosa type, Pseudomonas aeruginosa has strong resistance to the external environment, can survive for a long time in the wet place, is not sensitive to ultraviolet light, and is killed by moist heat at 55 ° C for 1 h. In addition, clinically common Pseudomonas bacteria and P. fluorescens, Smelly P. (P.putida) and so on.

Pseudomonas aeruginosa infection prevention

Pseudomonas aeruginosa is widely distributed in nature and spreads in hospitals through various channels; therefore, it is necessary to strictly disinfect the instruments, dressings, medical staff and caregivers to wash hands frequently, and perform aseptic operations carefully. Patients should be isolated and their dressings should be To burn, while actively treating the primary disease, removing the predisposing factors, Pseudomonas aeruginosa vaccine is divided into multi-price and monovalent, both of which have certain effects on the prevention and treatment of infection, and can be improved with the combination of multivalent and high-efficiency antiserum. The immunogenicity of the vaccine, other chemical vaccines prepared by bacterial components such as endotoxin vaccine, OPE vaccine, etc., also play a role in protecting the same strain.

Pseudomonas aeruginosa infection complications Complications, adult respiratory distress syndrome, shock

Can be complicated with migratory abscesses, often accompanied by shock, adult respiratory distress syndrome or DIC.

Symptoms of Pseudomonas aeruginosa infection Common symptoms Complex urinary tract infection Corneal ulcer Skin soft tissue infection Pustular keratitis Subcutaneous nodules Nodular shock Meningitis

Septicemia

Pseudomonas aeruginosa sepsis is secondary to large areas of burns, leukemia, lymphoma, malignant tumors, tracheotomy, venous catheters, heart valve replacement and various serious chronic diseases, etc. The gram-negative bacilli sepsis is 7% to 18%, ranking third or fourth, with the highest mortality rate. The clinical course is similar to that of other Gram-negative bacilli. Except for premature infants and young children, the patient may There are relaxation or missed heat, often accompanied by shock, adult respiratory distress syndrome (ARDS) or disseminated intravascular coagulation (DIC), etc., the skin may have characteristic gangrenous deep pustules, the surrounding ring with erythema, after the rash appears 48 ~72h, the center is grayish black gangrene or ulcer, small blood vessels have fungus plugs, the oozing smear Gram stain or culture easy to find bacteria, rash can occur in any part of the body, but more in the perineum, buttocks or underarms Occasionally, in the oral mucosa, limb abscesses may occur in the late stage of the disease.

2. Respiratory infection

Primary Pseudomonas aeruginosa pneumonia is rare, often secondary to impaired host immune function, especially on the basis of chronic lung disease, such as chronic bronchitis, bronchiectasis, tracheotomy, artificial respiration After the machine, the X-ray showed bilateral bronchial pneumonia with nodular oozing shadows, rarely empyema, secondary to sepsis, critical illness, small muscle arteries or venous necrosis in the lungs. Its type is similar to gangrenous erythema, and the mortality rate is extremely high. The chronic pulmonary infection of Pseudomonas aeruginosa occurs mostly in patients with cystic fibrosis, often accompanied by chronic cough, cough and progressive pulmonary dysfunction.

3. Endocarditis

Often occurs on the basis of the original heart disease, after cardiac surgery, valve replacement, bacteria are often inoculated on the wound suture or patch, can also occur in the normal heart valve of patients with burns or drug addiction, lesions can be involved The various valves of the heart, but the tricuspid valve is more common, the neoplasm involving the left heart valve, the prognosis is more serious, compared with the endocarditis caused by Streptococcus viridans, the cure rate of this disease is low, even in sensitive The cure rate of antibacterial drugs is still less than 30%, so the hernia should be removed early and the diseased valve should be replaced.

4. Urinary tract infection

Pseudomonas is a common bacterial infection in the urinary tract of hospitals, accounting for the second place in the hospital for infection of urinary tract isolates. Indwelling catheters are the cause of infection in paraplegic patients. Others such as neurogenic bladder, urinary tract obstruction, chronic Long-term use of urinary tract infections is also susceptible to Pseudomonas infection, and 40% of Pseudomonas aeruginosa sepsis is a urinary tract infection.

5. Central nervous system infection

Mainly caused by Pseudomonas aeruginosa, manifested as meningitis or brain abscess, often secondary to craniocerebral trauma, head and neck tumor surgery and lumbar puncture or ventricular drainage, but also by ear, mastoid, sinus infection Spread and spread, granulocyte deficiency, severe burns are risk factors for migration to the brain during Pseudomonas aeruginosa sepsis. The clinical manifestations are the same as other bacterial central infections, but the prognosis is poor, and the mortality rate is above 60%.

6. Osteoarticular infection

Mainly due to blood migration of sepsis or infection from adjacent tissue, complicated urinary tract infection and genitourinary surgery or device operation in the elderly, can cause multiple vertebral osteomyelitis. In recent years, it has been reported that heroin is often caused by injection of heroin. Inflammation, the clinical process is nothing special, less painful, and poor prognosis.

7. Eye infections

Pseudomonas aeruginosa is one of the common pathogens of corneal ulcer or keratitis. It is often secondary to corneal abrasion after ocular trauma or rural rice threshing. Pseudomonas aeruginosa contaminates contact lenses or lens fluids. Another important way is that the infection develops rapidly and can spread to the whole eye within 48 hours. It can cause corneal lysis quickly and should be treated urgently, otherwise it will cause blindness.

8. Ear, mastoid and sinus infection

After swimming, the pH of the external auditory canal is alkaline due to water ingress, which is beneficial to the growth of Pseudomonas aeruginosa, causing otitis externa, diabetes with vascular disease, and occasionally chronic painless malignant otitis externa caused by Pseudomonas aeruginosa, such as If the treatment is not timely, the consequences are poor. The otitis media and mastoiditis caused by the bacteria are often secondary to malignant otitis externa or acute otitis media. When there is diabetes or other diseases, Pseudomonas aeruginosa can cause intracranial infection through the vascular sheath. .

9. Skin and soft tissue infection

Septicemia patients may be secondary to erythematous rash, subcutaneous nodules, deep abscess, cellulitis and other skin lesions, burn wounds, hemorrhoids, traumatic wounds and varicose veins, often can be cultured Pseudomonas aeruginosa.

10. Digestive tract infections

Pseudomonas aeruginosa can cause lesions in any part of the digestive tract, which is common in infants and children with immunodeficiency of chemotherapeutic granulocytes, which can cause diarrhea in infants and adults, cecalitis or rectal abscess, Pseudomonas aeruginosa infection It is also one of the important invasion portals for sepsis.

Examination of Pseudomonas aeruginosa infection

Take specimens of infected parts, such as pus, sputum, blood, urine, rash, puncture or exudate, etc., and identify them according to the characteristics of microorganisms. Diagnosis can be established. Green pus and cerebrospinal fluid can be directly smeared first. Or after centrifugation, the sediment smear is stained. If it is Gram-negative bacteria, the diagnosis can be clearly confirmed by combining clinical manifestations.

Respiratory infection, X-ray showed bilateral lungs scattered in bronchial pneumonia with nodular oozing shadows.

Diagnosis and identification of Pseudomonas aeruginosa infection

diagnosis

Take the infected part specimens, such as pus, sputum, blood, urine, rash, puncture or exudate, etc. for bacterial culture, and identify according to the characteristics of microorganisms to establish a diagnosis.

Differential diagnosis

Culture positive, and biochemical identification as Pseudomonas can be diagnosed, can be identified as Pseudomonas aeruginosa on the selection of the medium and produce the green pus pigment, if there is no pigment or not fermented lactose on the identification medium or Gram-negative bacilli of glucose can be further identified by the following methods.

1. Pigment identification The bacteria can be inoculated into King A, B slant medium, and observed at 37 ° C for 24 hours or at room temperature for 5 days.

(1) P. aerugin pigment: dark green on the slope of King A, green in liquid medium contact with air, if the pigment is not obvious or mixed with other pigments, add chloroform to the slope, and observe at room temperature for 1 to 24 hours, if still not Obviously, dilute hydrochloric acid can be added dropwise to the chloroform solution, and the pus pigment is red in the acid layer.

(2) Pseudomonas fluorescein: Pseudomonas aeruginosa, Pseudomonas fluorescens, Pseudomonas putida showed yellow-green fluorescence on King B slant medium.

(3) red pus pigment: reddish purple on King A slant medium, such as 37 ° C 24h red is not obvious, can be set at room temperature for 3 to 5 days to observe, Pseudomonas aeruginosa is more common in the production of red septic .

(4) Black septic toxin: Pseudomonas aeruginosa often produces black pus toxin when growing in peptone-containing medium, and also has black pus toxin produced by Stenotrophomonas maltophilia.

2. Other identifications of Pseudomonas aeruginosa and other Pseudomonas are glucose oxidative decomposition, oxidase, arginine double hydrolysis, acetamidase, gluconic acid oxidation, nitrate reduction ammonia production test are positive, green Patients with pyogenic bacteria have copper-green proteinuria in the urine, and the patient's urine is adjusted to be acidic, alkaline and neutral. They are placed in the dark room and irradiated with ultraviolet light respectively. If there is abuminuria, light green fluorescence occurs.

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