In 1976, the American Legion veterans organization in Philadelphia, Pennsylvania, to meet for an outbreak of a pneumonia epidemic when, with 221 human cases, resulting in 34 deaths. At that time of unknown etiology, known as legionellosis. 1977 pathogens isolated from the disease the following year named Legionella bacteria, referred to as Legionella, is a Division of Legionella Legionella (legionella).
Rod. Size 2 ~ 20 × 0.3 ~ 0.9um. Weak negative Gram stain. Usually gimenez dieterle silver staining or staining staining. Often negative for acid-fast staining. No spores, no capsule, but one to the number of pili and flagella, can exercise. At different growth stages have different forms, such as mycelium-like, short hyphae-like, rod-shaped and so on. Cell wall contains large amounts of branched-chain fatty acids, total fatty acids for 68% or more. The similar characteristics and mycobacteria, but not with other gram-negative bacilli were significantly different.
Special nutritional requirements, often seeded in complex medium, the growth of the environment must contain cysteine and iron. Aerobic, 2.5 ~ 5% co2 can promote growth. Optimum growth temperature is 35 ℃, the optimum ph6.1. Slow growing, round colonies visible after 3 days, diameter 1 ~ 2mm, color changing, shiny, moist, translucent, with special smell. Most of Legionella produced gelatinase and β ~ lactic acid enzyme, catalase positive, uremic enzymes negative, do not reduce nitrate. Generally do not ferment sugars. Legionella pneumophila biodegradable ma niu salt.
Legionella strong resistance in nature, especially in the water as the most, tap water can survive for about one year. Still sensitive to chemical disinfectants, 0.05% phenol for a minute or iodine 10 ppm-minute death. Resistant to acid, hydrochloric acid can be tolerated on the ph2 30 minutes.
80 ~ 85% of Legionella infection caused by the Legionella pneumophila. It is often hidden in the air cooler (tower), hot water pipes, shower heads, etc., and in the form of aerosol transmission of the host. Legionella pneumophila with micro-structure of the capsule and pili, resistance to host phagocytic cells the role of bactericidal substances, and in which growth and reproduction, resulting in a variety of enzymes, exotoxin and endotoxin-like substances, leading to cell death, release of out of hundreds of bacteria.
Legionella pneumophila is the intracellular bacterial parasite, the disease is directly dependent on the ability of intracellular parasites. When bacteria invade the body, usually the first neutral cells and macrophages, but can not kill the bacteria, but is conducive to spread. After 7 to 10 days, the body's immune system to produce a specific cellular immunity to pathogens, complement each other with non-specific immunity, inhibit bacterial growth and enhance the intracellular activity of anti-nk cells infected cells. In addition, specific antibodies also have a role, can play the role of opsonin and activates complement, increased macrophage phagocytosis.
Microbial samples for the diagnosis of sputum, pleural fluid, blood or lung biopsy. Silver staining method was used dieterle smear samples, specific fluorescent antibody can also be used directly to check on the specimen. Carbon isolated yeast extract with buffer (bcye) agar medium, according to colony characteristics, morphology staining, and biochemical reactions were identified. In addition, by using specific DNA probes and polymerase chain reaction and poly (pcr) method of diagnosis. Treatment of choice of spiramycin, erythromycin and rifampin drugs. |