Cellulose is degraded by bacteria, especially those of the genus Cytophaga, and by various fungi. Patients with degenerative diseases such as emphysema or impaired kidney function are susceptible to infections. Such viruses are called naked viruses; those with a nucleocapsid surrounded by an envelope are enveloped viruses. Recent increases in disease incidence in California are due in part to earthquake activity, which has produced excess dust. Some insects have specialized mouthparts for piercing skin and for sucking blood and can inflict painful bites. Approximately 3% of untreated strep throat cases Rheumatic fever progress to rheumatic fever. This is a problem that affects 19 nations and that will probably require $65 million to eradicate. States today, those most likely to become infected are members of religious groups who are opposed to immunization, and illegal aliens who are unprotected by a vaccine. This yellow fever situation represents an excellent example of how viral diseases can remain endemic to those parts of the world where an insect vector lives. Each kilogram of yeast introduced into one of these media can produce 100 kg of protein-1,000 times that obtained from 1 kg of soybeans and 100,000 times that obtained from 1 kg of beef. Microwaves, another form of nonionizing radiation, are useful for food preparation, cooking, and processing but not for preservation. Embryonated eggs also are often used, but they should be handled only by very experienced technicians and only in specially equipped isolation laboratories. In humans, calcification fails to stop the growth of cysticerci; if vital organs such as brain, heart, or lungs are involved, patients may suffer paralysis and convulsions. And it also makes sense to obtain recommended immunizations during infancy and early childhood. Pasteur made real progress in understanding the disease when he found evidence of the infectious agent in saliva, the central nervous system, and peripheral nerves. They can also migrate to the brain, causing damage such as vision loss, or to the skin where they may form nodules. The methionine is usually removed later, however, so not all proteins actually start with methionine. Filtration, the passage of water through beds of sand, removes nearly all the remaining microIn the United organisms. Primary and Secondary Responses 510 Animation: Antibody Mediated Immunity Kinds of Antigen-Antibody Reactions 511 monoClonal antIbodIes 513 Animation: Production of Monoclonal Antibodies Cell-medIated ImmunIty 515 Animation: Cell Mediated Immunity the Cell-Mediated Immune Reaction 515 Animation: What Is the Cell-Mediated Immune Response Stalin directed that when antibiotic resistant bacteria were discovered, they were to be sent to the institute in Tbilisi. A wide assortment of symptoms can appear; syphilis has been called the "great imitator" because its symptoms can mimic those of so many other diseases. It is thought that they have more effective killer T-cells, which kill cells infected with viruses. Radiation Radiation used to control microorganisms includes ultraviolet light, ionizing radiation, and sometimes microwaves and strong sunlight. Before antibiotics became available, erysipelas often occurred after wounds and surgery and sometimes after very minor abrasions. Foods can be dehydrated by natural means, such as sun drying, or by artificial means, by passing heated air over the food with controlled humidity. X-rays and gamma rays, which are more energetic than ultraviolet radiation, easily break chemical bonds in molecules (Chapter 3, p. Several factors are at work, and each may have a greater or lesser effect on an outbreak of a given epidemic. As long as there are more host bacteria, the phage keep eating them away, until they are all gone. For persons with penicillin or cephalosporin allergies, a single intramuscular dose of spectinomycin 2 g, is recommended. Disease Cycles Some diseases occur in cycles-there are just a few cases for several years, and then many cases suddenly appear. Such fusion would allow the genes that control the use of galactose to control the entire operon, including the making of the enzymes involved in biotin synthesis. These organisms may hydrolyze sucrose (table sugar) to glucose and fructose, both of which can be metabolized for energy production and growth.
In this case, it has long been thought that although the genotype has changed, the phenotype is unaffected. Several organisms account for a share each of vaginitis cases or at least serve as a marker for disruption of the vaginal flora. Fever may end 5 to 10 days after onset when untreated or within 24 hours after antibiotics are given. When released, these proteins induce neighboring cells to produce antiviral proteins, which prevent these cells from becoming infected. For this reason treatment with penicillin or one of its derivatives is often begun even before culture results are available. People touching contaminated objects or surfaces, who then touched their nose, mouth, or eyes, became infected, as did those kissing or hugging. The 5-bromouracil that replaced thymine may pair with guanine instead of with adenine, which normally pairs with thymine. Research is in progress to find a way to control mosquitoes and to develop an effective vaccine. If the allergen is inhaled, mucous membranes of the respiratory tract become inflamed, and the patient has a runny nose and watery eyes. However, finding these pathogens in pasteurized milk has not become a persistent problem, and no action has been taken, although back in 1950 the pasteurization temperature was raised to kill Coxiella burnetii bacteria found in milk. Similar events led to the emergence of antibiotic-resistant strains of many other organisms, including staphylococci, gonococci, Salmonella, Neisseria, and especially Pseudomonas. These viruses multiply in specialized portions of the host cell cytoplasm called viroplasm, where they can cause skin lesions typical of smallpox, molluscum contagiosum, and cowpox. This toxin has been implicated as a cause of: (a) Meningitis (b) Myelitis (c) Motor neuron disease (d) Encephalitis (e) Spastic paralysis 17. Large parasites, such as helminths, are most effectively attacked by: (a) Basophils (b) Erythrocytes (c) Platelets (d) Neutrophils (e) Eosinophils 13. Secondary Treatment Secondary treatment is the removal of organic matter by the action of aerobic bacteria. Lymph node inflammation occasionally obstructs and scars lymph vessels, causing edema of genital skin and elephantiasis (massive enlargement) of the external genitalia in both males and females. Microbes similar to the early evolving stages of life may still exist in its depths. Although the Washington fungus dwarfs its Michigan counterpart in size, it is actually younger, having an estimated age of 400 to 1,000 years. In the transformed state, the cells become rounded and do not adhere to the culture container. One scientist used a 1,000-watt microwave for 4 minutes, which heated the pie to 45 degrees. However, after she finishes her task, she washes her hands properly and suffers no ill effects. Examples of fomites include soiled handkerchiefs, dishes, eating utensils, doorknobs, toys, bar soap, and money (U. For by inhibiting example, neutrophils pass out of the blood prostaglandin by squeezing between endothelial cells lin synthesis. Extracellular Killing Eosinophils defend against parasitic worm infections by secreting cytotoxic enzymes. What percentage of the nitrogen fixed annually on Earth is fixed by the action of bacteria Polyene antibiotics, such as amphotericin B, bind to particular sterols, present in the membranes of fungal (and animal) cells. Comparisons of normal and mutant organisms have led to important advances in the understanding of both genetic mechanisms and metabolic pathways. Such shots may lead to tolerance, preventing B cells from maturing into plasma cells to make IgE antibodies. For example, many parasites that leave the human body through feces die from desiccation (drying out) before they reach another host. Approximately 400 million people are infected worldwide, most with chronic amebiasis. They inject an anticoagulant, and blood stains on the sheets from still oozing bites, are typical of infestations.
Treatment is a 7-day course of trimethoprimsulfamethoxazole (Bactrim, Septra), traditional antiprotozoan drugs being of no help. Scabies and House Dust Allergy Scabies, or sarcoptic mange, is caused by the itch mite Arthropod Bites and Diseases A variety of arthropods, including ticks, mites, and insects, cause human disease either directly or as vectors of pathogens. Cases in which Neisseria survived improper laundering in the hospital have been documented; in dried masses of pus, the bacteria can survive for 6 to 7 weeks! Dry Heat, Moist Heat, and Pasteurization Dry heat is used to sterilize metal objects and glassware. Examples include surgical errors, drug reactions, and infections acquired from hospital treatment. The arrangement of the strands is somewhat like two trains pointed in opposite directions, and base pairing is like passengers in the two trains shaking hands. Cases have been found in which shingles has been caused by reactivation of the virus in the vaccine. However, if the identity of the organism is known, a narrow-spectrum drug should be used. Surfactants include alcohols, detergents, and quaternary ammonium compounds, such as benzalkonium chloride, which dissolve lipids. Light repair, or photoreactivation, occurs in the presence of visible light in bacteria previously exposed to ultraviolet light. Deinococcus turned out to have two circular chromosomes, plus a megaplasmid and a smaller plasmid. Many of the Fungi Imperfecti have recently been placed in other phyla and given new genus names. In fact, host defenses might be able to destroy the small number of organisms such that the disease will not occur at all. The absence of a rash distinguishes ehrlichiosis from Rocky Mountain spotted fever. The period of viral growth that occurs from the time of host cell penetration to the time when new virions are first assembled within the host cell is called: (d) Eclipse period (a) Lag phase (b) Latent period (e) Generation time (c) Repication phase 7. In fact, the name Loa loa is believed to be derived from a voodoo term meaning "the rising of a devil within you. Classification of Diseases Classification of diseases as infectious or noninfectious gives a very limited view of human disease. They are part of the normal intestinal microflora of cattle, horses, and some humans. Acne Acne (acne vulgaris) affects more than 80% of teenagers and many adults, too. Antimony compounds are used to treat both kala azar and skin and mucous membrane lesions. Croup, a viral infection found in children, also involves the larynx and epiglottis. Match the following parasitic terms to their definitions: Accidental parasite (a) Host that harbors a paraHost specificity site while it reproduces Intermediate host sexually Reservoir host (b) Parasite that invades an Definitive host organism other than its Obligate parasite normal host (c) Must spend at least some of its life cycle on or in host (d) Harbors a parasite during any part of its developmental stage except the sexual reproductive stage (e) Range of different hosts in which a parasite can mature (f) Infected organisms that make parasites available for transmission to other hosts 6. The amoeba that causes this condition is found in brackish water, seawater, and hot tubs, as well as contaminated contact lens cleaning solution. However, sickle-cell patients or carriers of the defect tend to be resistant to malaria. Most rooms for patients with tuberculosis have an outer "hallway" outside the main door to the room. In rare instances the disease progresses to meningitis, arthritis, and pericarditis. This involves injecting dye in the circulatory system to analyze the function of the heart. This tiny Gram-negative bacillus or coccobacillus is present in the normal urogenital tract in 20 to 40% of healthy women. The protein structure of milk that has been warmed is recovered when the milk is cooled. The organisms enter the body through mucous membranes of the eyes, nose, or mouth or through skin abrasions.
This mechanism provides for the orderly transmission of genetic information from parent cell to daughter cells. It is possible that autoimmune diseases such as rheumatoid arthritis and multiple sclerosis may be caused by superantigens. Moreover, prokaryotes have few structural characteristics, and these characteristics are subject to rapid change when the environment changes. Researchers concluded that the lack of immune surveillance of tumor cells proved to be the immunodeficiency most responsible for his death. A new, as yet unlicensed, vaccine has been produced in India, where the government has promised to sell it for only $1 a dose. The severity of symptoms is directly correlated with the quantity of viruses released from infected epithelial cells of the upper respiratory tract. However, some bacteria further metabolize nitrates, so a negative test for nitrates does not preclude the presence of bacterial infection. Thus, both an effective chemotherapeutic agent and an appropriate concentration to control an infection can be determined. Additional tests, including tests in animals, are necessary to identify carcinogens, but initial screening with bacteria can eliminate some substances from further study. Forest Service-announced that they mushrooms (armillaria bulbosa) had been studying an even (Courtesy Johann N. Cases occurring in Africa earlier in the 20th century would probably have been overlooked, given the lesser numbers of cases and the state of health care existing then. Many individuals with several insect-sting allergies carry such kits with them at all times. These materials include media, special nutrients that might be added to media, and pharmaceutical products such as drugs, sera, and vitamins. Openings to the outside of the body, such as the ears, nose, mouth, eyes, anus, urethra, and vagina, allow microbes to enter. If lesions are widespread or difficult to treat topically, as when they infect nailbeds, griseofulvin is administrated orally. The use of embryos did not completely solve the problem of studying cellular effects caused by viruses. One problem has been to identify the stage of the parasite responsible for triggering the immune response in humans. However, other microbes, such as viruses and parasitic worms, are destroyed without being ingested by a defensive cell; they are destroyed extracel lularly by products secreted by defensin cells. Creating a taxonomic system that provides an organized overview of all living things and how they are related to each other poses certain problems. Helicobacter is able to survive the acidic conditions of the stomach by producing which enzyme Notice that several of the lower vertebrae have fused as a result of infection damage. Some bacteria have complex nutritional requirements because they: (a) Are composed of a large number of different types of molecules (b) Can make a great many of the molecules found in the cell from simple precursors (c) Have many different enzymes and therefore can make many molecules (d) Contain unique molecules not normally found in bacterial cells (e) Lack many enzymes and must therefore be provided with many of the molecules they need for growth 10. Reductase test Standard plate count Test for coliforms Directly measures viable bacteria. Others believe that a self antigen recognized by the immune system as foreign is involved. Of the 20 different se rum proteins so far identified in the complement system, 13 participate in the cascade itself and 7 activate or inhibit reactions in the cascade. Wells are made in an agar gel and filled with test solutions of antigen (Ag) and antibody (Ab). In the sexual phase, the mycelium that produces conidia also forms the gamete-producing structures, antheridia (male) and ascogonia (female). Eventually, the center of the lesion becomes black and necrotic, the scab resembling a piece of coal; hence the Bacillus anthracis name anthrax from the Greek word produces a toxin that for coal. Such testing is usually done on the extremities to keep any hypersensitive reaction away from major organs. Much unnecessary anguish could be avoided if people, especially children, were taught to appreciate unfamiliar animals without touching them.
As many as 40% of males and 60 to 80% of females remain asymptomatic after infection and can act as carriers for 5 to 15 years. It allows passage of menstrual flow, receives sperm during intercourse, and forms part of the birth canal. Some can be vacuum-filtered, ensuring that what is forced into the bottle or flask will be sterile. In 1885 Daniel Carrion, a Peruvian medical student, Systemic Diseases 755 Table 23. During subsequent exposures with the surface antigen, antibodies bind to the antigen and activate complement. Both are found only on the western slopes of the Andes in Peru, Ecuador, and Colombia- the habitat of the sandfly Phlebotomus, which transmits the organism. It is particularly useful in preventing transplant rejection: It allows T cells to regain function after the drug is stopped, and it does not reduce resistance to infections provided by B cells. By studying many different phage transductions, scientists can determine where they were inserted on the chromosome and which adjacent genes they are capable of transferring. Nystatin was named for the New York State Health Department, where it was discovered. Whereas cells from the original cultures failed to grow, some from the mixed cultures did grow. If the antibody is present, it reacts with the antigen and forms immune complexes. Examples of Cell-Mediated Disorders Contact dermatitis occurs after second contact with poison ivy, metals, or another substance and usually appears as eczema. After excess unbound antigen is washed out, the solution being tested for antibody is added and allowed to react. The rhizobia then change from their free-living rod shape and become spherical, flagellated cells called swarmer cells. Humans have protective devices against microbial invasion or infection of the eyes and mucous membranes. Nearly all adults in Africa and India have been infected, and annual economic losses due to malaria exceed $1 billion in Africa alone. Furthermore, tuberculosis bacteria somehow stimulate the immune system to react as if they were viruses rather than bacteria. The main human pathogens found in soil belong to the genus Clostridium (Chapter 24, p. These enzymes include extracellular enzymes, usually produced by Gram-positive rods, which act in the medium around the organism, and periplasmic enzymes, usually produced by Gram-negative organisms, which act in the periplasmic space. A few drops of 1% silver nitrate solution in the eyes immediately after birth kills gonococci, but it is not effective against chlamydias and can irritate the eyes. Nutritional deficiency diseases lower resistance to infectious diseases and contribute to the severity of infections. Monoclonal antibodies are also being used to prevent respiratory syncytial virus infections in children, prevent acute kidney transplant rejection, and to treat rheumatoid arthritis. Such indirect fecal-oral transmission occurs when pathogens from feces of one organism infect another organism. Bacterial endospores, fungal spores, plant pollens, insect parts, and hundreds of mites (small organisms related to spiders; see photo) also abound in dust. During polio epidemics (before 1955) in the United States, (a) row after row of iron lungs was filled with patients (Courtesy March of Dimes Birth Defects Foundation) (b) such as this 2-year-old girl. No vaccines are available for bird flu, but companies are testing some candidate vaccines. By observing which phages cause holes in the lawn, researchers can identify the strain. Meningitis causes necrosis (death of tissues in a given area), clogging of blood vessels, increased pressure within the skull from edema, decreased cerebrospinal fluid flow, and impaired central nervous system function. Several antiprotozoan agents have been found that are successful in controlling or even curing most protozoan infections, but some have rather unpleasant side effects.
Satmooli (Asparagus Racemosus). Prinivil.
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He periodically returned to Berlin for treatment, leaving his troops without his brilliant and charismatic leadership. Following a severe case, the skin may peel, and the fingernails can fall off-but they will grow back. Identification of serovars is sometimes useful in tracing the source of disease outbreaks. Bacterial Endocarditis Bacterial endocarditis (en-do-kar-ditis), or infective endocarditis, is a life-threatening infection and inflammation of the lining and valves of the heart. However, more and more resistant organisms are being isolated the overall cost of from infections among the general antibiotic resistance population, and the risk of acquiring in the United States a drug-resistant infection is increasing is estimated between for everyone. A few agents are suitable as both disinfectants and antiseptics, although most disinfectants are too harsh for use on delicate skin tissue. The prognosis is poor when infections occur in fetuses because the damage is done before a diagnosis is made in the neonate. Local religious leaders told people that the vaccine was designed to make their children sterile. Now suppose that city B, the same size as city A, has not carried out a successful measles vaccination program. More people live long enough to develop degenerative diseases, and as they age their likelihood of developing a malignant disease increases. In otherwise healthy adults, salmonellosis lasts 1 to 4 days and is self-limiting. Acid in these foods inhibits the germination of most spores, should some survive the boiling-water treatment. One prion, when alcohol from fermenting yeast reaches about 10 times normal, refolds and triggers a change to a multicellular filamentous form of the fungus. The minimum time used for sterilization by autoclaving is: (a) 5 minutes (b) 15 minutes (c) 45 minutes (d) 1 hour (e) 2 hours 15. In fact, to maintain accreditation by the American Hospital Association, hospitals must have programs that include surveillance of nosocomial infections in both patients and staff, a microbiology laboratory, isolation procedures, accepted procedures for the use of catheters and other instruments, general sanitation procedures, and a nosocomial disease education program for staff members. Using sterile technique, press a standard-sized piece of sterile velvet or Velcro against a portion of your skin. Poor nutrition also increases the severity of measles and contributes to deaths from the disease. Identifying these various nuisance organisms in water is a tedious task because different tests are required for each kind of organism. Plaque from severely diseased gums contains dense mats of nonmotile filaments, cocci, and numerous motile organisms. Reservoirs of Infection Reservoirs of infection include humans, other animals, and nonliving sources from which infectious diseases can be transmitted. The importance of Protists Protists are important in food chains as producers and decomposers; they can be economically beneficial or detrimental. Unfortunately, the quinolones have been used so frequently in the Philippines that quinolone-resistant strains of Neisseria gonorrheae have already emerged there. Implementing these measures prevented future pandemics from spreading extensively into the United States. The bacteria living here are extremeophiles, possibly much like many of the bacteria that were present when life first emerged on Earth. In most cases acne disappears or decreases in severity as the body adjusts to the hormonal changes of puberty and as the functioning of the sebaceous glands stabilizes. Viral nucleic acid can be single-stranded or doublestranded, and linear, circular, or segmented (existing as several fragments). Because these organisms act at high temperatures, their metabolic rates are higher than those of other fermenters, and they produce alcohol at a more rapid rate. Invertebrates Invertebrates also have nonspecific defenses for fending off invaders.
The areas sprayed with fertilizer were soon nearly clean of oil to a depth of about one-third of a meter, while untreated areas were still coated with sticky oil. Transmission can occur by several modes, which we have grouped into three categories: contact transmission, transmission by vehicles, and transmission by vectors. As more archaeobacteria and their extremozymes are discovered, new manufacturing applications are certain to be developed. A complex capsid is a combination of helical and icosahedral shapes, and some viruses have a bullet-shaped capsid. Without treatment, half the patients die, but with the current best treatment, only 5% to 10% die. Serologic tests are available to diagnose dengue fever, and a vaccine against one immunological type of the virus appears to confer immunity. The fungi grew so slowly that contamination was not quickly seen in products, as bacterial contamination would have been. The vegetative cycle is repeated at intervals of 20 minutes or more, and the sporulation cycle is initiated periodically. These structures fuse, their nuclei mingle, and hyphal cells with dikaryotic nuclei grow from the fused mass. Adult worms are responsible for inflammation in lymph ducts, fever, and eventual blockage of lymph channels in affected areas. A fetal immunological reaction can occur when a mother with Rh-negative blood carries her second Rh-positive fetus. These links are shown by somewhat randomly placed cross branches, as the specific sequence of most transfers is unknown. Especially in the staphylococci, the hemolysins can damage other types of cells as well. Go to the companion web site to finetune your understanding of the chapter concepts and discover answers to the questions posed below. These modified sweat glands develop at puberty and contain gland cells, embedded in fat, that produce milk and ducts that carry the milk to the nipple. Unfortunately, many tumors and cancers show little regard for control by the immune system. To try to prevent allograft rejection, it is necessary to determine if the graft has histocompatibility antigens not found in the recipient. Reimmunization of adults every 10 years could be aided by administration of diphtheria toxoid and tetanus toxoid together, rather than tetanus toxoid alone after injuries. Johnson/ Biological Photo Service) In an activated sludge system, the effluent from primary treatment is constantly agitated, aerated, and added to solid material remaining from earlier water treatment. Once such para sites are destroyed, macrophages can engulf the parasite fragments. Diagnosis from blood cultures is difficult; the highly infectious organisms are hard to grow on ordinary laboratory media. Such diseases are most often transmitted by direct sexual contact, including kissing, but some can be transmitted by oral or anal sex. Even when inhibition has been properly interpreted in a disk diffusion test, the most inhibitory chemotherapeutic agent may not cure an infection. The enzyme, an -galactosidase, breaks the alpha linkages in the complex sugars, digesting them before they reach the bacteria in the colon, thus reducing the amount of flatulence. If a drug combines with a protein, however, the protein-drug complex sometimes can induce hypersensitivity. Lyme disease is treated with antibiotics such as doxycycline and amoxicillin, which are more effective the earlier they are administered in the course of the disease. Inflammation causes insulin resistance, which in turn causes more inflammation, resulting in diabetes. Several other arenavirus infections, including Bolivian hemorrhagic fever, have been identified in humans, especially in Africa and South America.
This allows the organisms to obtain and use a larger proportion of the few nutrient molecules that are available. There it causes serious congenital defects, including the accumulation of cerebrospinal fluid, abnormally small head, blindness, mental retardation, and disorders of movement. Desensitization to prevent a Type I allergic response is accomplished by stimulating the body to make: (a) IgE antibodies and antigen presenting cells (b) Antigen (allergen) (c) Histamine (d) IgG antibodies and regulatory T cells (e) Antihistamine 5. But because they have such a wide sprectrum of activity, they destroy the normal intestinal microflora and often produce severe gastrointestinal disorders. These fungi are properly called Ascomycota (asko-mi-kota); unlike other fungi, they produce a saclike ascus (plural: asci) during sexual reproduction (figure 11. The most common response is the production of antibodies that will inactivate an antigen and lead to destruction of infectious organisms. The Deep hot Biosphere Bacteria have been found at the deepest depths ever drilled. These patches contain lymphocytes and macrophages that protect the small intestine from microbial invasion from the large intestine. Treatment with antibiotics such as penicillin and medications to lessen discomfort may be necessary. Septicemias and related diseases are diagnosed by culturing appropriate samples and are treated with antibiotics. Some fastidious organisms, including those that cause gonorrhea, grow quite well in the human body but still cannot be easily grown in the laboratory on nutrient media. If he mates with a female infected by the same strain of Wolbachia, the offspring live and spread the same strain to their offspring. The endospores of this organism are the most heat-resistant known; the organism is: (a) Clostridium tetani (b) Clostridium botulinum (c) Mycobacterium leprae (d) Streptococcus thermicos (e) Listeria monocytogenes 18. Surveys of pregnant women reveal that 11% have Chlamydia in the cervix; postpartum fever is common among infected women. Specific diagnosis of shigellosis can be difficult because the organisms are very sensitive to acids in feces. Surgical removal, sometimes every 2 to 4 weeks, is the only treatment for these obstructive growths. The new champion, Carsonella ruddii, has only one-third that number, 159,662, which provide only 182 protein-coding genes. In addition, in 1991, 29 cases of transmissible spongiform encephalopathies were reported in British cats, and 2 were reported in ostriches in the Berlin Zoo. Levels of IgE are elevated in patients with allergies and in those harboring worm parasites. Numerical Taxonomy In numerical taxonomy, organisms are compared on the basis of a large number of characteristics and grouped according to the percentage of shared characteristics. Resistance to chemotherapeutic agents is a greater problem in viruses than in bacteria because so few antiviral agents are available. Its filaments clog filters and create floating clumps of undigested organic matter. Controlling Disease Transmission Several methods are currently available for full or partial control of communicable diseases. Often children are so badly behind when they return to school, especially if this happens several years in a row, that they become permanent drop-outs. These cells contain a water-proofing protein called keratin, which prevents water-soluble substances from entering the body. In an infection, acute inflammation functions to (1) kill invad ing microbes, (2) clear away tissue debris, and (3) repair injured tissue. Mucous membranes of the nose, throat, urethra, and vagina also provide warm, moist conditions, although nutrients are in shorter supply. Pathogenic microorganisms might develop resistance to the antibiotics, so treatment of the diseases they cause would become difficult or impossible. A virulent phage is capable of causing infection and, eventually, the destruction and death of a bacterial cell.
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