Haemophilus Influenza Infection  (流感嗜血杆菌感染)

流感嗜血杆菌是一种革兰氏阴性、兼性厌氧、不运动、不形成芽孢的细菌，是正常鼻咽部菌群的一部分，可引起侵袭性感染，尤其易感于免疫功能低下的宿主或幼儿。该菌的特征在于其多糖荚膜，这不仅增强了其毒力，也是血清分型的基础（其中B型最常与重症相关）。该菌需要特定的生长因子——X因子（原卟啉IX）和V因子（NAD或NADP）——才能实现最佳有氧生长，而这些因子通常由血液成分提供；这种依赖性使其得名“嗜血杆菌”（Haemophilus，嗜血菌）。该菌形态多形性，在染色涂片上呈球杆菌状或丝状，由于染色不一致，可能被误诊。琼脂平板上金黄色葡萄球菌菌落周围的卫星现象是一个有用的诊断特征，因为它会释放V因子。虽然它在5-10%的二氧化碳中生长最佳，但它在常温常压下也能存活。尽管早期人们误以为流感嗜血杆菌与流感有关，但现在人们已认识到流感嗜血杆菌是呼吸道感染、脑膜炎、会厌炎、化脓性关节炎和其他侵袭性疾病的主要原因，尤其是在未接种疫苗的人群中。

Haemophilus influenzae is a Gram-negative, facultative anaerobic, nonmotile, non-spore-forming bacterium that is part of the normal nasopharyngeal flora and can cause invasive infections, especially in immunocompromised hosts or young children. It is characterized by a polysaccharide capsule, which contributes to its virulence and is the basis for serotyping (with type b being most commonly associated with severe disease). The organism requires specific growth factors—X factor (protoporphyrin IX) and V factor (NAD or NADP)—for optimal aerobic growth, which are typically provided by blood components; this dependency led to its name "Haemophilus" (blood-loving). It exhibits pleomorphism in morphology, appearing as coccobacilli or filamentous forms on stained smears, and may be misidentified due to inconsistent staining. Satellitism around Staphylococcus aureus colonies on agar plates is a useful diagnostic feature due to the release of V factor. Although it grows best in 5–10% CO₂, it can survive under ambient conditions. Despite early misconceptions linking it to influenza, H. influenzae is now recognized as a major cause of respiratory tract infections, meningitis, epiglottitis, septic arthritis, and other invasive diseases, particularly in unvaccinated populations.

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