Legionnaires' disease-What is Legionnaires' disease?
Legionnaires' disease is not a military occupational disease, but a respiratory tract infection, the bacteria present in the water vapor. Legionnaires' disease or lobar pneumonia, is basically the same as a bacterial pneumonia, symptoms and pneumonia. American Legion Convention in Philadelphia in 1976, the first outbreak of Legionnaires' disease, the disease its name.China since 1982, Nanjing, Beijing and other places have reported the emergence of this disease. August 3, 2002, England found that the Legionnaires' disease.
Legionnaires' disease - Introduction
Veterans meeting was held in a hotel in Philadelphia, USA in July 1976, during the nearly 200 participants suffering from an unprecedented pneumonia and respiratory disease, resulting in 29 deaths. Symptoms are general malaise, headache, nausea, vomiting, diarrhea, muscle pain, fever, cough, initially dry cough, followed by a gray or bloody sputum, shortness of breath and violent illness, if not promptly treated, died of pneumonia and other concurrent syndrome.
After many months of investigation, and consumption of up to $ 2 million in costs, and finally found that the pathogen is a yet to be recognized bacilli, later known as "Legionella pneumophila bacteria. This disease was first found in the retired soldier who known as Legionnaires' disease.
Legionella bacteria are spread by air. Tank of air-conditioning system is the Legionella ideal breeding places, through the pipe throughout the entire building. Long-term air-conditioned indoor, should be particularly careful.
Legionellosis is a serious and sometimes fatal form of pneumonia. The disease is caused by the Legionella pneumophila bacteria, and other strains of Legionella. The bacteria are naturally present in the environment, and thrive in warm water and warm damp places. They are commonly found in lakes, rivers, creeks, hot springs and other bodies of water. They can also be found in soil and potting mix.
Legionnaires' disease - found that the history of
Legionnaires' disease in 1976, its 200th anniversary, a group of veterans in Philadelphia, "the beauty of Stratford hotel party two days after the participants have more than 180 people have been high fever, headache, vomiting, cough, whole body fatigue symptoms, 90% of cases chest X-ray showing pneumonia signs. The residents of the headquarters of the General Assembly vicinity of the hotel, there were 36 people there have the same symptoms. A total of 34 patients died.
After the outbreak, medical experts from the disease dead lung tissue isolated pathogenic bacteria known as Legionella, disease, hence the name "Legionnaires' disease". Since then, the Legionnaires' disease in the global total of more than 50 times in recent years are popular in Europe, USA, Australia and other countries and regions.
The major pathogens from soil and sewage, spread by air, since the respiratory tract invade. Clinically divided into two types: a fever, cough, pneumonia and lung inflammation dominated type, and dissemination-oriented, mild, and showed that fever, headache, myalgia, etc., without lung inflammation non-pneumonic also known Pangti Ake heat (Pontiacfever).
Legionnaires' disease - the cause
After a night stop the tap water in the faucet and the water mains nearby is at rest, residual microorganisms in the water to the large population, which may have a "Legionella". And poor management of artificial water systems (especially cooling and air conditioning and industrial cooling towers or evaporative condensers, public and private buildings in hot and cold water systems and whirlpool spas)-related disease outbreaks with this species of bacteria.
In addition, after a night stop moving water, the hydration reaction with the metal wall and the faucet metal chamber, the formation of metal-contaminated water, this is the morning the first time water will often see some anomalies, such as the color yellow, hair white or hair muddy reasons. In addition, our water most of the surface water by detergents and other organic pollution. Organic compounds will pass into the water disinfectant - chlorine reaction to generate the compounds of halocarbons such as chloroform. These substances have the potential carcinogenicity. Water released in the morning, the security risk is relatively large. This water contains harmful substances, not suitable for drinking, should not be used to brush your teeth, gargle can be released about the look of basin of water before then water.
Legionella necessary to cause infection is unknown, but may be considered susceptible to only a small amount of bacteria can cause infection, because patients have been known exposure to certain outbreaks source after only a few minutes or up to 3.2 km s outside contact with others outbreak source contracting the disease. Infection depends on the level of bacteria on the water contamination, bacterial formation and effectiveness of communication through the air, host factors and the toxicity of the particular strain of Legionella.
Legionnaires' disease - Pathogens
Legionnaires' disease Legionella pneumophila bacilli (Legionellapneumophila), pale staining, gram-negative pleomorphic short bacillus, 2 ~ 5 × 0.3 ~ 0.9μm, and occasionally filamentous body (8 ~ 20μm), Bacillus, and its genome size 2.5 × 109, is much larger than the gene of Rickettsia, Mycoplasma, and Chlamydia. The bacteria Gram dyeing difficulties Giensa dyed red, and some visible flagella, modified Dieterle saturated silver staining, showing the distribution of cells inside and outside the dark brown to black bacilli, direct fluorescent antibody staining method for detecting the bacteria, the more specific .
This aerobic bacteria and 2.5% carbon dioxide, Ph6.0 ~ 7.0, temperature 35 ° C and grow best in, but do not grow in normal medium, need to add a cysteine and ferric pyrophosphate Mueller-Hinton culture based growth, or charcoal yeast infusion agar growth.
The bacteria have more than 20 serotypes currently known about people at least have more than 10 serotypes, 1 type 1 predominant strains. China may 1 5 or type 6.
The bacteria spread nature, resistance to the external environment, can survive for two to four months in distilled water, tap water can survive for a year or so. 0.1% carbolic acid, glutaraldehyde, hydrochloric acid (pH1.7), 2% formalin, 70% alcohol in vitro killing effect.
Known Legionella can be parasitic in natural fresh water and artificial piping water to survive in the soil. Studies have shown that the incubation period of Legionnaires' disease is 5-10 days range. The main symptoms are fever, accompanied by chills, muscle pain, headache, cough, chest pain, dyspnea, and diarrhea, the case fatality rate was 10%, a serious condition will die. Are generally not human contact, can not easily identify with the general pneumonia.
In general, when the water temperature between 31-36 degrees Celsius, the water rich in organic matter, such bacteria can be long-term survival, when the water temperature to 60 ° C, Legionella not easy to survive. Legionnaires' disease in the city is mainly caused by the sin of Health Legionella bacteria in air humidifiers, water storage systems, air-conditioning systems and other wet environment.
Legionnaires' disease - EpidemiologyLegionnaires' disease is a) the source of infection of bacteria can be separated from the river water, soil and other samples. Has not yet proven in humans and animals as a source of infection.
B) the route of transmission of pathogens spread through the respiratory tract. Has been confirmed Legionnaires' disease outbreak in the excavation of soil, canals. Air conditioners, cooling water and humidifier water sprayer can be affected by this bacteria contamination. The disease spread has nothing to do with diet. Has been ruled out human contact transmission.
C) are generally susceptible to susceptible population groups, more common in the elderly. Men than women. The distribution of cases of Chinese medicine hospital-acquired infections accounted for 5 percent of nosocomial infections, pneumonia, accounting for more than 20%. Chronic diseases, long-term blood purification treatment or kidney transplant patients, cancer patients. The immunohistochemical preparations and smoked alcoholics susceptible to this disease.Disease after 6 to 7 days of serum specific antibody titers rose to five weeks and reached the peak, the number of months of decline. Pangti Ake hot secondary outbreak reports. Epidemiological investigations suggest that a latent infection.
D) the epidemiological characteristics of Legionnaires' disease was the worldwide distribution of the disease reports, or was sporadic, spotty outbreaks have been dozens of countries. All year round disease. However, more common in summer and autumn. Elderly, smoking, alcoholism, and immunocompromised persons contracting this disease.
Legionnaires' disease - pathogenesisLegionnaires' disease pathogenesis depends on the interaction between the cell structure of the lower respiratory tract disease of the external structure and host. Studies have shown that Legionella cell adhesion in lung tissue, first of all rely on their pili, flagella or cilia can invade the host lung tissue, but also through specific adhesins (adhisins) the release of toxic substances and enzymes directly, and which to settle.
Human alveolar macrophages may be the most important primary cellular defense, blood monocytes and alveolar macrophages of the bacteria did not, the reason, studies have shown that Legionella toxin to phagocytic cells serosal polarized. Serous membrane depolarization role performance is oxygen consumption, phosphate hexose slip activity as well as oxygen free radicals increase, which damage the bactericidal mechanism of phagocytes, bacteria able to live in the cell memory. But inhibited the growth of bacteria in activated macrophages.
The pathological changes in the lung parenchyma (ie, alveoli and terminal respiratory bronchioles), lesions were diversity have lobular Tai leaves or leaf inflammation, abscess was red or gray hepatocyte degeneration and visible consolidation the edge of edema, hyperemia, and focal hemorrhage. Severe pulmonary necrosis, abscess. The pleural visible fibrinous inflammation of serous exudation. Bronchi and large bronchioles are not involved. The Dietterle silver staining and direct immunofluorescence, can be found within a lesion cluster of bacteria and macrophages. Its specificity. Outside the lung, bone marrow, lymph nodes, liver, spleen, muscle, blood vessels and central nervous system and other damage. The microscopic lesions were seen in acute diffuse alveolar damage and acute fibrinous suppurative pneumonia two kinds of damage.
Legionnaires' disease - symptoms of the diseaseLegionnaires' disease has an incubation period of 2-10 days (but in some recent well-documented outbreaks recorded an incubation period of up to 16 days). The initial symptoms are fever, anorexia, headache, malaise and lethargy. Some patients also have muscle pain, diarrhea and confusion. Also usually an initial mild cough, but as many as 50% of patients can present phlegm. About one-third of the patients Blood-streaked phlegm or hemoptysis. The severity of disease from mild cough to a rapidly fatal pneumonia. Accompanied by respiratory failure and / or shock and multiple organ failure, progressive pneumonia resulting in death.
Legionnaires' disease treatment usually worsens during the first week. And other risk factors for severe pneumonia, Legionnaires' disease is the most common complication was respiratory failure, shock and acute kidney failure and multiple organ failure. Without exception, requires antibiotic treatment, recovery, and usually after a few weeks or months to fully recover. Occasional severe progressive pneumonia or ineffective treatment for pneumonia and, in rare cases, brain in sequelae.
Mortality caused by the Legionnaires 'disease is dependent on: the severity of the disease, the appropriateness of initial antimicrobial therapy, infection of Legionnaires' disease environment and host factors (in patients with immuno-suppression, the disease is usually more severe). The case fatality rate as high as 40-80% in the immuno-suppressed patients treated through appropriate case management and depending on the severity of clinical signs and symptoms can be reduced to 5-30%. Able to develop an immune response, the death rate is usually in the range of 10-15% within
Legionnaires' disease - clinical manifestationsLegionnaires 'disease Legionnaires' disease is a generic term describing the pneumonic and non-pneumonic Legionella infection.
Non-pneumonic form is an acute, self-limiting influenza-like illness, usually lasting 2-5 days. The incubation period varies from hours to 48 hours. The main symptoms are fever, chills, headache, malaise and myalgia. This type of infection does not cause death.
A) pneumonia incubation period is generally 2 to 10 days. Prodromal symptoms: fatigue, headache, aching muscles, sudden onset of fever in 1 to 2 days up to more than 40 ℃, mostly missed heat. The course of the disease can occur early multi-system involvement prominent characteristic symptoms of this disease. The vast majority of patients have a cough, initially dry cough, and half of the patients converted to non-purulent viscous sputum or slightly purulent sputum, sputum often contain a small amount of blood stained, the individual may be hemoptysis, a small number of patients with chest pain, difficulty breathing are more common.
Neurological symptoms are more common in the very period, and sometimes very prominent, including varying degrees of disturbance of consciousness, muscle tone, enhance or array trembling, unsteady gait, etc., may have a temporary limb flaccid paralysis, nervous systemic signs, cerebrospinal fluid examination no abnormal prompted the central nervous system symptoms and more sources are caused by toxic encephalopathy. 8 to 10 days, the majority of cases the body temperature decreased along with improvement in systemic symptoms such as pneumonia.
But severe cases can occur in the heart, liver, renal dysfunction, and even failure death, persistent can also be complicated by pulmonary abscess, 70% in patients with X-ray initial test involving only the unilateral performance of edge blur circular shadow or flake bronchial as pneumonia, can progress to large patchy shadows deepen density, can affect the large-leafed, leafy, or both, may be associated with a small amount of pleural effusion.
B) non-pneumonic (Pang embankment Ake hot) This type of light for the bacteria infection. The incubation period is 5 to 66 hours, half of about 36 hours. Chills, fever onset, body temperature is generally no more than 39.5 ° C, accompanied by headache, myalgia. Respiratory symptoms are not serious, half of the patients with only mild dry cough and chest pain, part of the dry throat pain; X-ray pneumonia shadow. The individual may have diarrhea, water samples will be. Or insomnia, dizziness, memory loss, the sense of dim items strong, tremor and other neurologic manifestations. Were mild. Duration of 3 to 5 days of non-pneumonic form of self-healing, to restore more smoothly.
Legionnaires' disease - the spread of diseaseThe causative agents, legionellae, are freshwater bacteria that are found in the aquatic environment within the world-wide, but the artificial water systems sometimes provide an environment conducive to growth of Legionella bacteria. The bacteria survive as parasites in the viable cell protozoa internal or between and survival in the biofilm formed in the bacteria survive in water systems. They use a mechanism similar to infect protozoa, infecting other human cells, can cause human infections. The Legionella pneumophila bacteria most frequently isolated from the community, travel, or hospital-acquired Legionnaires' disease patients.
Legionella organisms can be through the air (such as wind) spread. Inhalation of contaminated water sprays or mists can cause an infection. May also occur through the respiratory infection, especially in disease outbreaks during the hospitals. The bacteria live in water temperature of 20-50 degrees C (optimum temperature 35 degrees Celsius) in the hot and cold water systems, the formation of groups. They contaminate air conditioning cooling towers, hot and cold water systems, humidifiers, whirlpool spas and other water-containing devices. There is no direct interpersonal communication.
Legionnaires' disease - the disease rangeAccording to the survey and the diagnostic methodology, the incidence of community-acquired Legionnaires' disease vary widely. As many countries lack the appropriate method of diagnosing the infection or the ability to monitor the epidemic monitoring system, the real magnitude of the problem is unknown. 34 (Population: 4.6776 million) in 2003, the 36 countries of Legionella infection in Europe working group reported a total of 4578 cases, which means that the European average incidence rate of 9.8 cases per million population. In Denmark, a high level of testing for legionella in patients with pneumonia. According to the findings of the country, of the 36 countries in a more realistic incidence would be closer to 10,000 cases a year.
In the community and travel-associated Legionnaires' disease risk factors include: smoking, male, 50 years, history of alcohol abuse and lung disease related deaths, immuno-suppression, and debilitating chronic diseases.
Host risk factors for hospital-acquired pneumonia: recent surgery, intubation (program) to place the catheter in the trachea, mechanical ventilation, breathing, use of a nasogastric tube, and the use of respiratory therapy equipment. The most susceptible hosts are immuno-compromised patients, including organ transplant recipients and those receiving corticosteroid treatment.
The prediction of Legionnaires' disease death factors, including delays in diagnosis and administration of appropriate antibiotic treatment, increasing age and coexisting disease.
Legionnaires' disease - clinical diagnosisThe clinical diagnosis of Legionnaires' disease bacillus infection is more difficult, alone, the clinical manifestations difficult to swollen infections caused by other pathogens to identify, it must be confirmed serological or pathologic examination.
A) epidemiological data in the summer and autumn, in the same building or under certain environmental conditions, sudden onset. More common in men, the elderly or middle-aged.
B) clinical manifestations specificity was diversity, is divided into the pneumonic and non-pneumonic, may have multiple organ involvement, is not easy to find the cause, should be combined with epidemiological data to diagnose.
C) laboratory tests
A. Like the total number of leukocytes in peripheral blood increased, mostly between 10 ~ 20 × 109 / L, neutrophils increased, showing a left shift.
Two. Respiratory secretions (sputum or endotracheal aspirates) Gram stain can not be found a large number of dominant flora, and only see a small amount of neutrophils.
3. Serological tests (1) The indirect fluorescent antibody method: double antibody titer increased more than four times, and up to ≥ 1:128, or recovering from a single titer ≥ 1:956 to diagnose the disease more than 3 weekend (with a few six weeks) serum antibody titers up to the diagnostic criteria. About 80% positive rate of this Law. (2) direct fluorescent antibody method: from the known antibody to detect pathogens of the respiratory secretions of patients, the positive rate of up to 50%, do the early diagnosis.
4. Cell culture: sputum, endotracheal aspirates, bronchoscopy lotion, pleural effusion or lung tissue homogenate was inoculated on Mueller-Hinton medium plus 0.025% ferric pyrophosphate and 0.04% L-cysteine, or inoculated in carbon Yeast infusion agar medium. That the latter positive rate of 60 to 70 percent.In addition, the ELISA test for detection of sputum or urine of patients with Legionella pneumophila bacteria antigen, can also be used for early diagnosis.
Legionnaires' disease - treatment of diseaseApproximately 15% case fatality rate of Legionnaires' disease, and older, the higher fatality rate, the underlying disease or immune deficiency mortality was also high. Most of the cause of death was respiratory failure, followed by shock and acute renal failure. Such as early diagnosis and providing them with effective treatment, the mortality can be reduced.
Specific treatment with erythromycin as the drug of choice. 2.0 ~ 4.0g daily, oral administration is ineffective and should be intravenous infusion for 3 weeks. General medicine within 48 hours after the temperature drops, systemic and respiratory symptoms improved. Such a course of less than two weeks, there may be recurrent or prolonged convalescence. Erythromycin efficacy is not satisfied, or a serious condition, with rifampicin, the daily dose of 600 to 900mg Dayton clothing or 2 times a day orally. Penicillins, aminoglycosides, cephalosporins had no significant effect on the disease.
In addition, the general treatment of the symptomatic treatment of this disease is also very important. Maintain water and electrolyte balance, the application of artificial ventilation in respiratory failure, shock, vasoactive drugs and other anti-shock measures, acute renal failure, dialysis therapy are important therapeutic measures.
Legionnaires' disease - prevention measuresThere is no vaccine available for Legionnaires' disease.
Legionnaires' disease is caused by the threat to public health through preventive measures. Although it is impossible to eradicate the source of infection, but can significantly reduce the risk. Prevention of Legionnaires' disease depends on the good management of possible sources, including regular cleaning and disinfection as well as other physical (temperature) or chemical measures (biocide) to minimize growth. For example, the cooling tower on a regular basis cleaning and disinfection with frequent or continuous addition of biocides; biocides to maintain an adequate level of chlorine in a spa pool, and at least once a week to drain and clean the entire system; hot and cold water systems clean and hot water maintained at 60 ° C, cold water remains below 20 ° C, or using the appropriate biocide to limit growth. Use of these control measures, especially in hospitals, industrial sites, hotels, leisure centers and will greatly reduce the risk of legionella contamination and prevent the occurrence of sporadic cases.
Such control and prevention measures must be accompanied by proper vigilance on the part of general practitioners and community health services for the detection of cases.
Legionella out a very wide range of environmental distribution, self-protection is to pay attention to maintain clean showers, air conditioning systems, hot water pipes leading water transport pipeline. The above-mentioned appliances should be regularly clean up, the conditions should be disinfected regularly. If Legionnaires' disease outbreak, the need for timely reporting to local disease prevention and control department, conducted an epidemiological study, so that as soon as possible to clear contaminated sites, timely and clear water pollution. Has by Legionella contaminated water can be taken to heat disinfection (water temperature rose above 70 ℃, flush all water supply pipelines), ozone disinfection (ozone concentration in the 1 ~ 2mg / L), ultraviolet disinfection disinfection.
Non-pneumonic infection do not require any antibiotic treatment, symptomatic treatment is sufficient. After laboratory confirmation of the Legionnaires' disease require antibiotic treatment, without exception.
