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IV. Replace the underlined words with their synonyms from the list




Signs, intense, toilets, continuous, in the end, show, generally, declining, considerable, ailments, dividing

1. People infected with HIV eventually develop symptoms that also may be caused by other less serious condi tions.

2. With HIV infection, however, these symptoms are prolonge d and often more severe.

3. HIV commonly causes a severe "wasting syndrome", resulting in substantial weight loss, a general decline in health, and, in some cases, death.

4. Studies indicate that HIV is not transmitted through air, food, or water, or by insects.

5. No known cases of AIDS have resulted from sh aring eating utensils, bathrooms, locker rooms, living space, or classrooms.

V. Answer the following questions.

1. What is AIDS?

2. When and where were the first cases of AIDS identified?

3. When and where did researchers detect HIV in a specimen for the first time?

4. What is AIDS caused by?

5. Where do HIV-1 and HIV-2 occur?

6. What cells does HIV infect?

7. What are the symptoms of HIV?

8. What are the periods in AIDS flow?

9. What are the ways of HIV transmission?

10. What are the ways of preventing HIV transmission?

11. How is HIV not transmitted?

VI. Say whether the following statements are true or false.

1. The virus named HIV-1 occurs mainly in Africa.

2. HIV-2 occurs throughout the world.

3. HIV destroys CD4 cells as fast as they are produced.

4. There are six periods in AIDS flow.

5. An infected person can transmit the virus to another person only if symptoms are present.

6. All people who have the virus know about it.

7. People who have the virus may look and feel completely well.

 

VII. Fill in the words from the list, then make sentences using the completed phrases.

key, eating, yeast, closely, transmit, share, weight, health-care, immunodeficiency, develop

1. __________ related

2. __________ role

3. __________ symptoms

4. __________ infections

5. __________ loss

6. __________ a virus

7. __________ needles

8. __________workers

9. __________utensils

10._________ syndrome

 

 

Antibiotics.

.

1. ;

2. , , ;

3. .

Text 1

Read the text and correct the false statements.

1. Antibiotic is a kind of microbes.

2. Antibiotics damage all cells of the body.

3. The number of deaths that are caused by meningitis, pneumonia, and scarlet fever had declined before people began using antibiotics.

4. Antibiotics are not effective in treating infectious diseases in animals.

Antibiotics

Antibiotic is a drug produced by certain microbes. Antibiotic substances are obtained from bacteria and fungi that live in the air, soil, and water. Most antibiotics are used by physicians to fight various diseases caused by harmful microbes. A few are used to treat certain cancers.

Antibiotics are selectively toxic that is, they damage certain types of cells, but do not damage others. Many antibiotics are harmful to the cells of pathogenic (disease-causing) microbes, but they do not normally damage human cells. Physicians use these types of antibiotics to treat a variety of bacterial diseases, including gonorrhea, syphilis, and tuberculosis, and infections caused by staphylococcal and streptococcal bacteria. A small number of antibiotics, however, were developed to attack human cells. Some of these are used to treat cancer. They are selectively toxic mostly because they only damage cells that are in the process of dividing.

Antibiotics are sometimes called "wonder drugs" because they can cure many diseases that once were often fatal. The number of deaths that are caused by meningitis, pneumonia, and scarlet fever has declined drastically since people began using antibiotics.

Antibiotics are also used to treat infectious diseases in animals and to control bacteria and fungi that damage fruits and grains. Farmers sometimes add small amounts of antibiotics to livestock feed to stimulate the animals growth.

Text 2

Read the text and choose the correct variant.

1. Antibiotics are used to treat viral/bacterial infections.

2. Limited-spectrum/broad-spectrum antibiotics fight G+ and G- infections.

3. Antibiotics that fight pathogenic fungi/G+ infections include nystatin and griseofulvin.

4. Every/No broad-spectrum antibiotic is effective against all bacterial infections.

Kinds of Antibiotics

There are more than 70 clinically useful antibiotics. Most of them are used to treat bacterial infections. Others fight harmful fungi and protozoa, and a few are used to treat cancer. Antibiotics are not effective against most viruses, and so they cannot be used for chickenpox, measles, and most other viral diseases.

Antibacterial antibiotics. Many bacteria can be classified as either Gram-positive (G+) or Gram-negative (G-). This classification method was developed by Hans C. J. Gram, a Danish bacteriologist of the late 1800s. According to Gram's system, many bacterial infections are classified as either G+ or G-, depending on the type of bacteria that caused them. The bacteria in each group have certain characteristics that help determine the sensitivity of these microorganisms to antibiotics. Some antibiotics are most effective against G+ infections, and others work best for G- infections. Both these kinds of drugs are called limited-spectrum antibiotics. However, various broad-spectrum antibiotics fight G+ and G- infections, as well as other bacterial infections.

Antibiotics used to treat chiefly G+ infections include clindamycin, erythromycin, and penicillin G. Those used for mainly G- infections include colistin and gentamicin. Such antibiotics as chloramphenicol and tetracycline fight both G+ and G- infections, as well as other types of bacterial infections. No limited-spectrum antibiotic works against all G+ infections or against all G- infections. Similarly, no broad-spectrum antibiotic is effective against all bacterial infections. Research has shown which antibiotics work best against certain infections, and physicians follow these guidelines when prescribing drugs.

Other kinds of antibiotics. Antibiotics that fight pathogenic fungi include nystatin and griseofulvin. For example, griseofulvin is used to treat various fungus diseases, such as ringworm and other types of skin infections. Paromomycin is used to treat amebiasis, a disease caused by protozoa. Anticancer antibiotics include doxorubicin, which is used to treat acute leukemias, and bleomycin, which is used to treat Hodg-kin's disease.

Text 3

Read the text and say how antibiotics work according to the following plan:

1. Prevention of cell wall formation.

2. Disruption of the cell membrane.

3. Disruption of chemical processes.

How Antibiotics Work

Antibiotics fight pathogenic microbes and cancer cells by interfering with their normal cell processes. In most cases, this interference can occur in one of three ways: (1) prevention of cell wall formation, (2) disruption of the cell membrane, and (3) disruption of chemical processes.

Prevention of cell wall formation. The contents of bacterial cells are enclosed in a membrane that is surrounded by a rigid wall that prevents cells from splitting open. Penicillins and some other antibiotics destroy pathogenic microbes by hindering the formation of this wall. Human cells do not have rigid cell walls and so are not damaged by these antibiotics.

Disruption of the cell membrane. Some antibiotics, including amphotericin and nystatin, disrupt the cell membrane of certain microbes. This membrane controls the movement of materials in and out of the cell. If the membrane is disrupted, vital nutrients may escape from the cell, or poisonous substances may enter and kill the cell. But the membranes of human cells are not affected because these antibiotics disrupt cell membranes that contain elements found only in microbial cells.

Disruption of chemical processes. All cells produce proteins and nucleic acids, which are vital to the life of any organism. Some antibiotics fight diseases by interfering with the chemical processes by which these substances are produced. For example, streptomycin and tetracycline prevent certain kinds of microbes from producing proteins, and rifampin interferes with nucleic acids formation.

Human cells produce proteins and nucleic acids in much the same way that microbial cells do. But these processes differ enough so that some antibiotics interfere with chemical activities in microbial cells but not in human cells. However, the antibiotics that are used to treat cancer interact with DNA (deoxyribonucleic acid), thereby preventing human cancer cells from dividing.

Text 4

Read the text and tell as much as you can about the three main dangers of antibiotics:

allergic reactions;

destruction of helpful microbes;

damage to organs and tissues.

Dangers and Limitations of Antibiotics

Many antibiotics are recognized as safe drugs when properly used. But antibiotics can cause unpleasant or dangerous side effects. The three main dangers are (1) allergic reactions, (2) destruction of helpful microbes, and (3) damage to organs and tissues. The effectiveness of antibiotics is sometimes limited because pathogenic microbes can become resistant to them.

Allergic reactions, in most cases, are mild and produce only a rash or fever. But a severe reaction to the drug may result in death. Although all antibiotics can produce allergic reactions, such reactions occur most frequently with penicillins. About 10 per cent of the people of the United States are allergic to penicillins. Before prescribing an antibiotic, physicians usually ask if the patient has ever had an allergic reaction to the drug. Most people who are allergic to one antibiotic experience no such reaction to another one that has a significantly different chemical composition.

Destruction of helpful microbes. Certain areas of the body commonly harbor both harmless and pathogenic microbes. These two types of microbes compete for food, and so the harmless microorganisms help restrain the growth of those that cause disease.

Many antibiotics especially broad-spectrum drugs do not always distinguish between harmless and dangerous microbes. If a drug destroys too many harmless microorganisms, the pathogenic ones will have a greater chance to multiply. This situation often leads to the development of a new infection called a suprainfection. In most instances, physicians prescribe a secondary drug to combat the suprainfection.

Damage to organs and tissues is rare in people using antibiotics that act only against the cells of pathogenic microbes. However, extensive use of some of these antibiotics may damage tissues and organs. For example, streptomycin, which is used to treat tuberculosis, has caused kidney damage and deafness. Physicians only take such risks if there is no other effective drug.

Anticancer antibiotics are most toxic to groups of cells that are constantly dividing, such as cancer cells. However, some normal cells, especially cells in the bone marrow, stomach, and intestines, are also constantly dividing. Healthy tissues made up of such cells can be damaged by the use of anticancer antibiotics.

Resistance to antibiotics may be acquired by pathogenic microbes. Such resistance develops through changes in the genetic information of microbial cells. In some cases, it develops when a spontaneous genetic change called a mutation occurs. In other cases, resistant microbes transfer genetic material to nonresistant microbes and cause them to become resistant. During antibiotic treatment, nonresistant microbes are destroyed, but resistant types survive and multiply. Thus, extensive use of antibiotics can encourage the growth of resistant species. Mutations may also occur in cancer cells, making them resistant to anticancer antibiotics.

Text 5





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