【医学英语第5期】基础篇之微生物学（二）

发布时间：2021/11/19 11:34:13

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本期为微生物学的第二讲，主要讨论炭疽和蛔虫病这两种既往常见而当今社会较为罕见的疾病。炭疽是由炭疽杆菌所致的一种人畜共患的急性传染病。人因接触病畜及其产品及食用病畜的肉类而发生感染。临床上主要表现为皮肤坏死、溃疡、焦痂和周围组织广泛水肿及毒血症症状；似蚓蛔线虫简称蛔虫，是人体内最常见的寄生虫之一。成虫寄生于小肠，可引起蛔虫病。其幼虫能在人体内移行，引起内脏幼虫移行症。

案例分析

Case 1：A local craftsman who makes garments from the hides of goats visits his physician because over the past few days he has developed several black lesions on his hands and arms. The lesions are not painful, but he is alarmed by their appearance. He is afebrile and his physical examination is unremarkable.

案例1：一名使用鹿皮做皮衣的当地木匠来就医，主诉过去几天中手掌和手臂上出现几个黑色皮肤损害。皮损无痛，但是外观较为骇人。患者无发热，体检无异常发现。

1. What is the most likely diagnosis?

Cutaneous anthrax, caused by Bacillus anthracis. The skin lesions are painless and dark or charred ulcerations known as black eschar. It is classically transmitted by contact with the hide of a goat at the site of a minor open wound.

皮肤炭疽：由炭疽杆菌引起，皮损通常无痛、黑色或称为焦痂样溃疡。主要通过鹿皮经由皮肤细小伤口传播。

2. How will the causative microorganism appear on Gram staining?

B anthracis is a G+ spore-forming rod. The spores are resistant to many chemical disinfectants, heat, UV, and drying and are therefore a feared biological warfare.

微生物学特性：炭疽杆菌为革兰氏阳性芽孢杆菌，由于芽孢能耐受大多数消毒剂、高温、紫外线和烘干，故常被作为生化武器。

3. What is the other spore-forming microorganism?

Clostridium species are the other G+ spore-forming bacteria. Bacillus and Clostridium species can be differentiated by their ability to neutralize oxygen fee radicals. Bacillus species have catalase and superoxide dismutase-enzymes that can survive in aerobic environments. Clostridium species don’t have these enzymes and therefore obligate anaerobics.

芽孢菌鉴别诊断：芽孢杆菌vs 梭状芽孢杆菌。主要看其中和氧自由基的能力，芽孢杆菌有过氧化氢酶和超氧化物歧化酶，能分解氧自由基→兼性厌氧；梭状芽孢杆菌则没有→专性厌氧。

4. What is other manifestation of this infection?

B anthracis also causes pulmonary anthrax. In this condition, inhaled anthrax spores reach the alveoli, taken up by macrophages and carried to mediastinal lymph nodes. This can result in mediastinal hemorrhage and a bloody pleural effusion. X-ray of the chest reveals a widened mediastinum.

炭疽其他表现：主要是通过吸入芽孢导致肺炭疽→抵达肺泡→巨噬细胞携带芽孢到达纵隔淋巴结→纵隔出血、血性胸水，胸脯显示纵隔扩大。

★炭疽病要点总结：特殊接触史+特殊焦炭样皮损+微生物学鉴定★

Case 2: A 49-year-old woman from rural area presents with diffuse, crampy abdominal pain that has persisted for 4 days. She has had no bowel movements since the pain started and has noticed a weight loss of 4.5kg over the past month. CT of the abdomen reveals an inflamed gallbladder and an irregular mass in the second portion of the duodenum. Stool sample reveals rough-surfaced eggs. Complete blood count and liver function test results are as follows:

WBC count: 14,000/mm3

ALT/AST/AKP: normal

Eosinophils: 20%

Total bilirubin/direct bilirubin: normal

Albumin: 3.2g/dL

案例2：49岁农村女性主诉弥漫、痉挛性腹痛4天，肠蠕动减少。过去一个月体重减轻4.5kg。CT显示胆囊炎症，十二指肠有不规则肿块。粪检显示粗糙表明的球形虫卵。血检提示白细胞升高，嗜酸性粒细胞显著升高。

1. What is the most likely diagnosis?

Ascariasis, caused by a nematode (roundworm) found in the rural and tropical climates. Ascariasis is the most common helminthic infection worldwide. Eosinophilia is a classic finding in helminth infection and is due to the release of eosinophilic of major basic protein.

蛔虫病：由蛔虫（圆线虫）引起，多见于农村及热带地区。蛔虫病是全世界范围内最常见的蠕虫感染，典型表现为嗜酸性粒细胞显著升高，主要与蠕虫感染后嗜酸性粒细胞大量释放碱性蛋白有关。

2. What tests can be used to confirm the diagnosis?

Analysis of a stool sample shows eggs with a knobby, rough surface.

蛔虫病诊断：粪便检查可见多结节、表面粗糙的球形虫卵。

3. What are the appropriate treatments for this condition?

Mebendazole or albendazole is the drug of choice. The bendazoles work by disrupting helminthic microtubule synthesis, which weakens cell structure.

治疗：甲苯咪唑或丙硫咪唑为首选药物。机理为干扰蠕虫微管合成，破坏其细胞结构。

★蛔虫病要点总结：特殊地区+腹痛、体重减轻病史+影像学检查肠道有包块（蛔虫团块）+嗜酸性粒细胞显著升高+粪检虫卵阳性★

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