Acinetobacter infection

Introduction to Acinetobacter infection Acinetobacter is a conditional pathogen. When the body's resistance is reduced, it is easy to cause infection. It is one of the most important pathogens causing nosocomial infection. This bacteria can cause respiratory infection, sepsis, meningitis. , endocarditis, wound and skin infections, genitourinary tract infections, etc., severe cases can lead to death. Acinetobacter infections are more common in the elderly and infants. In recent years, the outbreaks and drug resistance of the bacteria in hospitals have increased, and they are multi-drug resistant, which has caused clinical attention. basic knowledge The proportion of illness: the incidence rate is about 0.003% - 0.007% Susceptible people: more common in the elderly and infants Mode of infection: non-infectious Complications: ventriculitis, brain abscess, hydrocephalus, septic arthritis, osteomyelitis

Causes of Acinetobacter infection

Pathogenic bacteria (30%):

Acinetobacter is a type of Gram-negative bacilli that does not ferment sugars. The classification of this genus has undergone multiple changes, such as calcium acetate micrococci, cocci, vaginal seaweed, nitrate-negative bacilli, and chromobacter nitrite. , Polymorphic mimic bacteria and Lofira Mori, etc., in the 1984 Berger Handbook, the strain belongs to Nesico, only one species, A. calcioaceticus, divided into two Subspecies, one of which is A. calcoaceticus subsp. antratum and A. calcoaceticus subsp. lwoffii; the latter is called mima polymotha. The main difference between the two subspecies is that the former can oxidize and decompose glucose, xylose, lactose, etc., and acid production does not produce gas, while the latter does not decompose any sugar. In recent years, Acinetobacter has been divided into 19 by DNA hybridization technology. Species, seven of which have been named, Acinetobacter calcoaceticus, Acinetobacter baumannii, A. haemolytius, A. baumanii, Acinetobacter baumannii (A .junii) and Acinetobacter johnsonii, Acinetobacter baumannii (Ar Adioresistance), the nitrate-negative Acinetobacter and Acinetobacter baumannii are more pathogenic, the bacteria are Gram-negative bacilli, the size is 2.0m × 1.2m, but the shape is mostly club-shaped, can exist alone However, it is often arranged in pairs, sometimes forming a chain shape. In the solid medium, it is mainly composed of dicocci. In the liquid medium, it is mostly short rod-shaped, evenly filamentous. Gram staining is often difficult to decolorize, so it is easy to cause false Positive bacteria,

Reduced body resistance (30%):

The bacteria is obligate aerobic bacteria, has no special requirements for nutrition, and grows well on ordinary medium. The optimum temperature is 37 °C. After 24 hours, the colonies have round protrusions, smooth surface, neat edges, grayish white, opaque, Mucus, no power, capsule, hemolytic Acinetobacter can be hemolysis on blood agar dry plate, generally does not produce pigment, a few strains produce yellow-brown pigment, the bacteria oxidase is negative, the enzyme reaction is uncertain, , hydrogen sulfide, methyl red, Voges-Proskauer (VP) are negative, do not produce phenylalanine deaminase, lysine decarboxylase, ornithine decarboxylase and fine Nitrate double hydrolase, can not reduce nitrate, most strains can use citrate, Acinetobacter is widely found in nature, mainly in water and soil, but also from healthy human skin, saliva, pharynx, The eyes, ears, respiratory tract, genitourinary tract and other parts are separated. The bacteria can also be detected in milk, dairy products, poultry and frozen foods. The pathogenicity of the bacteria is not strong, among which Acinetobacter baumannii, calcium acid is not Bacillus and Lofi Strong pathogenicity, generally do not cause infection, it can cause onset of body resistance is lowered.

(two) pathogenesis

Acinetobacter is a conditional pathogen and a component of the normal flora of the human body. The bacteria are found in human skin, conjunctiva, nasopharynx, gastrointestinal tract, urinary tract, saliva, etc., 25% of normal skin carries this bacterium. 7% of adults and infants can be temporarily infected with pharynx, 45% of tracheotomy is colonized by Acinetobacter, and the pathogenicity of the bacteria is not strong, among which Acinetobacter baumannii, Acinetobacter aceti, and Lofi Acinetobacter has strong pathogenicity, and its pathogenic virulence factors are less, mainly related to bacteriocin, capsule, pili, etc., the bacteria do not cause disease under normal circumstances, only the body's resistance is reduced. When it can cause infection, the current clinical infection of Acinetobacter, Acinetobacter baumannii and bacteria Acinetobacter calformin accounted for the vast majority (80%), the predisposing factor of this disease is that patients often have serious primary diseases such as Chronic lung disease, malignant tumors, burns, immunocompromised and elderly hospitalized patients usually occur after 1 week of hospitalization; patients are treated with hormones, immunosuppressants and broad-spectrum antibiotics, which can change the body's immune function and normal bacteria in the body. Clumps leading to dysbacteriosis; Clinical application of various catheters, tracheal intubation, artificial devices and major surgery, etc., are often the route of infection; infection sites are often ICU, burn wards, etc., opportunistic infections caused by this genus include skin wound infection, genitourinary Infection, pneumonia, lung abscess, can also cause sepsis, endocarditis, meningitis, brain abscess, etc., accounting for 1% to 3% of infections in hospitals, and occasionally can cause acquired infections outside the hospital.

Prevention of Acinetobacter infection

1. Actively treat the primary disease, remove the incentives as early as possible, such as various catheters, timely stop hormones, broad-spectrum antibiotics, etc.

2. The hospital staff must wash their hands carefully. After contact with the patient, they should wash their hands and use a disinfectant such as benzalkonium bromide to soak hands.

3. Once the original infected person leaves, the patient room should be carefully cleaned and disinfected. The used catheter and tracheal intubation should be specially cleaned and disinfected.

Acinetobacter infection complications Complications ventriculitis brain abscess hydrocephalus septic arthritis osteomyelitis

Can be complicated by ventriculitis, brain abscess, hydrocephalus, septic arthritis, osteomyelitis, peritonitis, abdominal abscess, eye infection and oral abscess.

Symptoms of Acinetobacter infection Common symptoms Shock, ecchymosis, eye infection, bacterial infection, chest pain, bedridden, prostatic hypertrophy, neck, tonic, hepatosplenomegaly

The clinical manifestations vary greatly depending on the location of the infection and the severity of the condition.

1. Respiratory tract infections: more common, mostly in patients with severe underlying diseases, such as the original lung disease, long-term bedridden, receiving a large number of broad-spectrum antibiotics, tracheotomy, tracheal intubation, artificial assisted breathing, etc. Among the isolates of respiratory specimens in ICU patients in China, Acinetobacter baumannii ranked third (11%), with fever, mostly mild or moderate irregular fever, cough, chest pain, shortness of breath, and severe cases with cyanosis. The lungs may have moderate to fine wet sounds. Chest X-ray examinations often show bronchial pneumonia. They may also be large-leaf or flaky infiltrates, occasionally abscesses or exudative pleurisy, complicated by sepsis and meningitis. Culture and tracheal aspirate culture have a large number of bacterial growth, bacteremia is rare, if not treated in time, the mortality rate is higher (40% ~ 64%).

2. Septicemia: Acinetobacter septicemia mainly occurs in nosocomial infections. Among the 2576 strains of sepsis, Acinetobacter infection in hospitals is second only to Escherichia coli, Pseudomonas, and Klebsiella pneumoniae in Gram-negative bacilli. The separation rate is almost equal, about 8%, and the incidence of Acinetobacter is the least in the infection of nine Gram-negative bacilli in hospitals. Acinetobacter septicemia occurs mostly in the use of indwelling venous catheters and catheters. Or surgical patients, or suffering from serious underlying diseases, long-term use of corticosteroids or cytotoxic drugs, often combined with respiratory infections, patients with fever, symptoms of toxemia, skin defects, hepatosplenomegaly, etc. In severe cases, shock can occur, and the mortality rate of this disease is quite high (17% to 46%). The important reason is related to the drug resistance and multiple bacterial infections. Bowman's fixed rod infection is usually heavier. The case fatality rate is also high.

3. Wounds and skin infections: wound infection accounts for 17.5% of the total infections of the bacteria. The incidence rate is traumatic infection, post-operative infection, wound infection after burn, wound infection can also be mixed with the bacteria and other bacteria, such as the intestine. Bacillus, Pseudomonas aeruginosa, Enterococcus, Staphylococcus or Streptococcus pyogenes cause mixed infections. Intravenous catheter contamination can cause severe skin cellulitis, and severe wound infections often involve sepsis.

4. Genitourinary tract infection: The detection rate of the genitourinary system is higher, second only to the respiratory system. Some domestic scholars have reported that the urinary tract infection caused by the genus is 28.6%. The primary disease has prostatic hypertrophy and urethra. Calculus, urethral stricture, the cause is mostly indwelling catheter, bladder fistula, etc., clinical manifestations of urethritis, pyelonephritis, vaginitis, etc., mostly based on the genus of the genus, mainly mixed with other bacterial infections, there are Some are asymptomatic carriers.

5. Meningitis: mostly occurs after craniocerebral surgery, but also for primary infection, especially in children, the predisposing factors are craniocerebral surgery, craniopharyngioma puncture suction, lumbar puncture, etc., clinical manifestations of fever , headache, vomiting, neck stiffness, Kelnigues positive and other purulent meningitis changes, infants have gaze, screaming, convulsions, nystagmus, anterior tibiofemoral fullness, increased suture and increased limb muscle tension, Skin may also appear sputum, ecchymosis, clinically misdiagnosed as epidemic cerebrospinal meningitis, should pay attention to, can also be complicated by ventriculitis, brain abscess, hydrocephalus, etc., cerebrospinal fluid examination appearance turbidity, total number of cells and Increased neutrophils, increased protein, decreased sugar content, smear of smear of the lungs can be found in Gram-negative bacilli.

6. Others: The bacteria can cause infection in other parts, and form suppurative inflammation, such as septic arthritis, osteomyelitis, peritonitis, abdominal abscess, eye infection and oral abscess.

Examination of Acinetobacter infection

The total number of white blood cells increased significantly, and neutrophils reached more than 80%.

X-ray examination of the lungs can be characterized by multi-lobular tracheobronchial pneumonia, occasional abscess formation and exudative pleurisy, cerebrospinal fluid examination appearance turbidity, total number of cells and neutrophils increased.

Diagnosis and identification of Acinetobacter infection

The clinical manifestations of this disease are not characteristic. Intra-hospital infections, infections in patients with severe primary diseases should consider the infection of the bacteria, the body's resistance is reduced, the immune function is low, the elderly and premature infants, tracheotomy and intubation, Long-term arteriovenous catheters, catheters, broad-spectrum antibiotics, and intensive care rooms are important susceptibility factors. The diagnosis of Acinetobacter infection depends on bacterial culture. This strain is very morphologically Moraxella and Neisseria. Similar, but there are certain differences. Generally, Neisseria is kidney-shaped and relatively arranged; Moraxella is a short bacillus, which is arranged in double and connected at both ends. The form of Acinetobacter can vary depending on the medium used, such as The agar plate cultured in 18~24h is usually smear of 1.0m×0.7m; while the smear of broth culture is a typical 2.0m×1.2m bacillus, which can be identified according to different biochemical reactions. However, in judging the results, the characteristics of the bacteria should be taken into consideration, that is, the distribution of Acinetobacter is extensive, the nutrient conditions are low, and it is easy to grow and reproduce, which is prone to specimen contamination and false positives, so it should be strictly disinfected. Collecting specimens is generally considered to have a diagnostic value at the top of the culture for 2 times. If only one culture is positive, it should be combined with clinical considerations, whether or not the above-mentioned susceptibility factors are present, and whether the results of the drug susceptibility test are consistent with the clinical efficacy, etc. Still need to pay attention to urine, sputum or pharyngeal culture positive is not necessarily a pathogenic bacteria, must be positive or pure culture can be judged as pathogenic bacteria, such as urine culture positive bacteria count should be >100,000 / ml; For those who are cultured positive, the number of Acinetobacter colonies per dry plate should be more than 30.

The diagnosis of Acinetobacter infection depends on bacterial culture. The bacteria are similar in morphology to Moraxella and Neisseria, but there are also some differences. Generally, Neisseria is kidney-shaped and relatively arranged; Moraxella is Brevibacterium. Arranged in pairs, connected at both ends.

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