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Ethnicity: An Italian man may respond to pain expressions discount lithium 300 mg on-line symptoms by dpo, body positions order line lithium medicine rocks state park, crying order lithium online now symptoms 8 days past ovulation, and physio- with cries, moans, complaints, and so on, logic responses. Communication with parents whereas an Irish man may be calm and unemo- or guardians is vital for accurate pain tional about his pain. Religious beliefs: In some religions, pain is limit their independence; boredom, loneliness, viewed as suffering and as a means of puriﬁca- and depression may affect an older person’s per- tion to make up for individual or community ception of pain and willingness to report it. Anxiety and other stressors: Fear of the unknown may compound anxiety and aggravate pain. Potter’s symptoms are in pain or when the medication isn’t work- and pain history to determine what pharmaceutical ing anymore. What would be a successful outcome for this with cancer pain and other severe types of pain patient? What intellectual, technical, interpersonal, and/or tions and conscientiously assess any side effects. Duration of pain: “For how long have you been Intellectual: knowledge of the pain experience, pain experiencing this pain? Quantity and intensity of pain: “How frequently experience, such as stress and fatigue do you get these attacks? On a scale of 1 to 10, Interpersonal: ability to communicate and interact how would you rate the intensity of this pain? Study Guide for Fundamentals of Nursing: The Art and Science of Nursing Care, 7th Edition. Several nurses have expressed great Multiple Response Questions frustration caring for Tabitha because they ﬁnd it 1. Study Guide for Fundamentals of Nursing: The Art and Science of Nursing Care, 7th Edition. Nitrogen balance is a comparison between catabo- the decrease in growth is dramatic. Mobility, lism and anabolism and can be measured by com- autonomy, and coordination increase, as do paring nitrogen intake and nitrogen excretion. This age group When catabolism and anabolism are occurring at develops an attitude toward food. Appetite the same rate, as in healthy adults, the body is in a decreases and becomes erratic. Weight consciousness becomes bonds are broken, carbons can bind with addi- compulsive in 1 of 100 teenage girls and results tional hydrogen atoms. Smoking, alcohol abuse, and long-term use of support growth and maintain maternal homeo- certain medications stasis, particularly during the second and third c. Nutritional and physical activity and loss of lean body needs per unit of body weight are greater than mass, energy expenditure decreases. Carbohydrates Supply energy (4 cal/g); also spares protein, 50%–60% helps burn fat efﬁciently, and prevents ketosis b. Proteins Maintain body tissues; support new tissue 10%–20% growth; component of body framework c. Fats Important component of cell membranes; Saturated 10% synthesis of bile acids; precursor of steroid Unsaturated 35% hormones and vitamin D; most concentrated source of energy (9 cal/g); aids in absorption of fat-soluble vitamins; provides insulation, structure, and body temperature control. Water Essential for all biochemical reactions; participates 2,000–3,000 mL/day in many biochemical reactions; helps regulate body temperature, helps lubricate body joints; needed for adequate mucous secretions Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins. Study Guide for Fundamentals of Nursing: The Art and Science of Nursing Care, 7th Edition. Anorexia nervosa: Characterized by denial of room temperature, such as clear liquids plus appetite and bizarre eating patterns; may result milk, plain frozen desserts, pasteurized eggs, in extremely dangerous amount of weight loss; cereal gruels; high-calorie, high-protein supple- can be fatal. Typical individual is adolescent girl ments are recommended if used for more than from middle or upper socioeconomic class; 3 days competitive; obsessive; distorted body image. Bulimia: Characterized by episodes of gorging to eliminate foods that are hard to digest and followed by purging. Typical individual is chew, including those that are high in ﬁber and college student who fears gaining weight but is fat, adequate in calories and nutrients, and can overwhelmed by periods of intense hunger. Nasogastric feeding tube: Inserted through nose requirements than women because of their and into stomach. Disadvan- requirements that results from illness and tage: Introduces risk for aspiration of tube feed- trauma varies with the intensity and duration ing solution into lungs. Alcohol abuse: Alcohol can alter the body’s use nose into the upper portion of the small intes- of nutrients and thereby its nutrient tine. Patient’s progress toward meeting nutritional gastrointestinal tract, increase gastrointestinal goals motility, damage the intestinal mucosa, or bind b. Patient’s tolerance of and adherence to the diet with nutrients, rendering them unavailable to when appropriate the body. Megadoses of nutrient supplements: An excess need for further diet instruction of one nutrient can lead to a deﬁciency of d. Johnston meet his nutritional and exercise record, plus interview designed to determine needs? A diet plan could then The nurse should explain the diet order to the be devised that would contain foods low in fat and patient, screen patients at home who are at nutri- cholesterol, enabling him to lose 1 to 2 tional risk, observe intake and appetite, evaluate pounds/week. The nurse should also set up an exer- patient’s tolerance for speciﬁc types of foods, cise program for Mr. Johnston that he could adapt assist the patient with eating, address potential to his busy lifestyle. For the greatest chance of suc- for harmful drug–nutrient interactions, and teach cess, the nurse should tailor diet instructions indi- nutrition. Advise the patient to eliminate any foods that recommended allowances of grains, vegetables, are not tolerated. MyPyramid Food Guide Copyright © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins. Study Guide for Fundamentals of Nursing: The Art and Science of Nursing Care, 7th Edition. Johnston manifests a weight loss to meet energy needs, as evidenced by a 5- to 10-lb of 2 pounds and has lower blood pressure and cho- weight gain. Do a 72-hour diet history to determine the aver- ethical/legal competencies are most likely to bring age number of calories he ingests daily. Provide whatever assistance he needs with feed- Intellectual: knowledge of nutrients and nutritional ing. Add high-calorie snacks to his diet, increas- requirements for patients across the life span. Until the desired weight is regained and through dietary restrictions maintained, weigh the patient daily and keep an Interpersonal: special interpersonal competencies to accurate ﬂuid I&O and calorie intake record. Explore nursing strategies to reduce agitation changes necessary to improve his nutritional status and hyperactivity, such as music, balance Ethical/Legal: ability to act as a trusted and effective between solitude and social interaction, rest peri- patient advocate ods, and so on. Evaluative Statement: 1/20/11: Expected outcome Consultation with a nutritionist, printed materials met—patient gained 8 lb over past month and seems on hypertension and high cholesterol, exercise to enjoy high-calorie snacks. Objective data are underlined; subjective data are in and Alzheimer’s disease; experienced in working boldface. Church, a 74-year-old white man, is being families; experienced gerontologic nurse admitted to the geriatric unit of the hospital for a 4.
Substance Withdrawal Deﬁned “Withdrawal” is deﬁned as the physiological and mental read- justment that accompanies the discontinuation of an addictive substance (Townsend purchase discount lithium online treatment resistant schizophrenia, 2009) purchase lithium 150 mg otc symptoms melanoma. The symptoms of withdrawal are speciﬁc to the substance that has been ingested and oc- cur after prolonged or heavy use of the substance 300 mg lithium symptoms quad strain. The effects are of sufﬁcient signiﬁcance to interfere with usual role performance. Low to moderate consumption produces a feeling of well-being and reduced inhibitions. At higher concentra- tions, motor and intellectual functioning are impaired, mood becomes very labile, and behaviors characteristic of depres- sion, euphoria, and aggression are exhibited. The only medical use for alcohol (with the exception of its inclusion in a number of pharmacological concentrates) is as an antidote for methanol consumption. Common substances containing alcohol and used by some dependent individuals to satisfy their need include liquid cough medications, liquid cold preparations, mouthwashes, isopropyl Substance-Related Disorders ● 73 rubbing alcohol, nail polish removers, colognes, and aftershave and preshave preparations. Opioids Opioids have a medical use as analgesics, antitussives, and an- tidiarrheals. They produce the effects of analgesia and euphoria by stimulating the opiate receptors in the brain, thereby mim- icking the naturally occurring endorphins. Hallucinogens Hallucinogens act as sympathomimetic agents, producing effects resembling those resulting from stimulation of the sympathetic nervous system (e. At this time there is no real evidence of the safety and efﬁcacy of the drug in humans. Cannabinols Cannabinols depress higher centers in the brain and consequently release lower centers from inhibitory inﬂuence. They produce an anxiety-free state of relaxation characterized by a feeling of ex- treme well-being. Marijuana has been used therapeutically in the relief of nau- sea and vomiting associated with antineoplastic chemotherapy. Inhalants Inhalant disorders are induced by inhaling the aliphatic and aromatic hydrocarbons found in substances such as fuels, solvents, adhesives, aerosol propellants, and paint thinners. The effects are relatively brief, lasting from several minutes to a few hours, depending on the speciﬁc substance and amount consumed. A genetic link may be involved in the develop- ment of substance-related disorders. Children of alcoholics are three times more likely than are other children to become alcoholics (Harvard Medical School, 2001). Studies with monozygotic and dizygotic twins have also supported the genetic hypothesis. A second physiological hypothesis relates to the possibility that alcohol may produce morphine- like substances in the brain that are responsible for alco- hol addiction. This occurs when the products of alcohol metabolism react with biologically active amines. The psychodynamic approach to the etiology of substance abuse focuses on a punitive super- ego and ﬁxation at the oral stage of psychosexual develop- ment (Sadock & Sadock, 2007). Individuals with punitive superegos turn to alcohol to diminish unconscious anxi- ety and increase feelings of power and self-worth. Sadock and Sadock (2007) stated, “As a form of self-medication, alcohol may be used to control panic, opioids to diminish anger, and amphetamines to alleviate depression” (p. The effects of modeling, imita- tion, and identiﬁcation on behavior can be observed from early childhood onward. Various studies have shown that children and adolescents are more likely to use substances if they have parents who provide a model for substance use. Peers often exert a great deal of inﬂuence in the life of the child or adolescent who is being encouraged to use substances for the ﬁrst time. Modeling may continue to be a factor in the use of substances once the individual enters the work force. This is particularly true in the work setting that provides plenty of leisure time with coworkers and where drinking is valued and is used to express group cohesiveness. Drinks in secret; hides bottles of alcohol; drinks ﬁrst thing in the morning (to “steady my nerves”) and at any other opportunity that arises during the day. During a binge, drinking continues until the individual is too intoxicated or too sick to consume any more. Behavior borders on the psychotic, with the individual wavering in and out of reality. Periods of amnesia occur (in the absence of intoxication or loss of consciousness) during which the individual is unable to remember periods of time or events that have occurred. Experiences multisystem physiological impairments from chronic use that include (but are not limited to) the following: a. Peripheral Neuropathy: Numbness, tingling, pain in extremities (caused by thiamine deﬁciency). Wernicke-Korsakoff Syndrome: Mental confusion, agita- tion, diplopia (caused by thiamine deﬁciency). Without immediate thiamine replacement, rapid deterioration to coma and death will occur. Alcoholic Cardiomyopathy: Enlargement of the heart caused by an accumulation of excess lipids in myocardial cells. Esophageal Varices: Distended veins in the esophagus, with risk of rupture and subsequent hemorrhage. Gastritis: Inﬂammation of lining of stomach caused by irritation from the alcohol, resulting in pain, nausea, vomiting, and possibility of bleeding because of erosion of blood vessels. Pancreatitis: Inﬂammation of the pancreas, resulting in pain, nausea and vomiting, and abdominal distention. With progressive destruction to the gland, symptoms of diabetes mellitus could occur. Alcoholic Hepatitis: Inﬂammation of the liver, resulting in enlargement, jaundice, right upper quadrant pain, and fever. Cirrhosis of the Liver: Fibrous and degenerative changes occurring in response to chronic accumulation of large amounts of fatty acids in the liver. In cirrhosis, symptoms of alcoholic hepatitis progress to include the following: • Portal Hypertension: Elevation of blood pressure through the portal circulation resulting from defective blood ﬂow through the cirrhotic liver. Symptoms of alcohol intoxication include disinhibition of sexual or aggressive impulses, mood lability, impaired judgment, impaired social or occupational functioning, slurred speech, incoordination, unsteady gait, nystagmus, and ﬂushed face. Physical and behavioral impairment based on blood alcohol concentrations differ according to gender, body size, physical condition, and level of tolerance. The legal deﬁnition of intoxication in most states in the United States is a blood alcohol concentration of 80 or 100 mg ethanol per deciliter of blood (mg/dL), which is also measured as 0. Nontolerant individuals with blood alcohol concentrations greater than 300 mg/dL are at risk for respiratory failure, coma, and death (Sadock & Sadock, 2007). Occurs within 4 to 12 hours of cessation of, or reduction in, heavy and prolonged alcohol use. Symptoms include coarse tremor of hands, tongue, or eye- lids; nausea or vomiting; malaise or weakness; tachycardia; sweating; elevated blood pressure; anxiety; depressed mood or irritability; transient hallucinations or illusions; headache; seizures; and insomnia.
As the salt it is most com- children discount generic lithium canada medications migraine headaches, which is most marked during the first year of life purchase genuine lithium on-line medications given before surgery. Pharmacokinetics The pharmacokinetics of smoked crack cocaine are almost About 90% of nicotine from inhaled smoke is absorbed buy cheap lithium 300mg on line symptoms kidney disease, while identical to those of intravenous cocaine. A high concentration of nicotine may be Repeated large doses commonly precipitate an extreme surge present in the breast milk of smokers. Myocardial infarction or arterial lating nicotine is metabolized in the liver, kidneys and lungs. Nicotine and its oids, which addicts tend to use on a regular basis, cocaine is metabolites are excreted in the urine. The metabolite cotinine used in binges, where doses may be taken several times an can be used to quatitate exposure. However, upon stopping a cocaine binge, withdrawal symp- toms including excessive sleep, fatigue and mild depression, Table 53. Repeated cocaine use may produce adverse effects including anorexia, confusion, exhaustion, palpitations, dam- Ischaemic heart disease (strongest correlation) age to the membranes lining the nostrils and, if injected, Cancers of the lung, other respiratory sites and the oesophagus, blood-borne infections. Use of cocaine in pregnancy is associ- lip and tongue ated with damage to the central nervous system of the fetus. Chronic bronchitis and emphysema, respiratory tuberculosis ‘Crack babies’ can usually be cured of their ‘addiction’ by Pulmonary heart disease abstinence over a few weeks. Currently, there are no specific Aortic aneurysm drug treatments for cocaine dependence. Effect of smoking on drug disposition and effects Caffeine dependence The most common effect of tobacco smoking on drug dispos- Tolerance is low grade and dependence is not clinically ition is an increase in elimination consistent with induction of important. Withdrawal can lead temically, but is of great medical importance because of its to an abstinence syndrome consisting of craving, irritability and pathological and psychological effects when used as a bever- sometimes physical features (e. Alcohol is the most important drug of dependence, and Substitution of nicotine via skin patches or nicotine gum as in Western Europe and North America the incidence of alco- part of a smoking cessation programme significantly increases holism is about 5% among the adult population. The antidepressant bupropion appears to reduce the desire to smoke and is licensed as an adjunct to motivational Pharmacokinetics support in smoking cessation. It is contraindicated in patients Ethyl alcohol is absorbed from the buccal, oesophageal, gastric with a history of seizures or of eating disorders, or who are and intestinal mucosae – approximately 80% is absorbed from experiencing acute alcohol or benzodiazepine withdrawal. Alcohol delays gastric emptying and in Varenicline, a selective nicotinic receptor partial agonist, is high doses delays its own absorption. It is started 1–2 weeks tration, alcohol can usually be detected in the blood within five before stopping smoking. Peak concentrations occur between 30 minutes and Side effects include gastro-intestinal disturbances, headache, two hours. Hepatic This group of compounds includes caffeine (present in tea oxidation to acetaldehyde is catalysed by three parallel and colas, as well as coffee), theobromine (present in choco- processes. The major effects of these com- Alcohol elimination follows Michaelis–Menten kinetics, pounds are mediated by inhibition of phosphodiesterase, with saturation occurring in the concentration range encoun- resulting in a raised intracellular cyclic adenosine monophos- tered during social drinking. Its use does not lead to Nervous system: Alcohol decreases concentration, judgement, improved intellectual performance except perhaps when discrimination, and reasoning and increases self-confidence. Progressively increasing plasma concentrations are associated Circulatory effects include direct myocardial stimulation with sensations of relaxation followed by mild euphoria, producing tachycardia, increased cardiac output, ectopic beats incoordination, ataxia and loss of consciousness. Caffeine use should be curtailed in patients concentrations, the gag reflex is impaired, vomiting may occur who suffer paroxysmal dysrhythmias. Its effect on blood pres- and death may result from aspiration of gastric contents. Cerebral vasoconstriction provides some importance of alcohol as a factor in road traffic accidents is rationale for use of caffeine in migraine. The central depressant actions of muscle relaxes and respiration is stimulated centrally. Mild alcohol greatly enhance the effects of other central depressant diuresis occurs due to an increased glomerular filtration rate drugs. In patients with organic brain damage, alcohol may subsequent to dilatation of the afferent arterioles. Chronic neurological accompaniments of persistent alcohol abuse include various forms of central Cytoplasmic and peripheral neurodegeneration, most commonly involving Catalase alcohol Microsomal the vermis of the cerebellum, and a peripheral neuropathy. Any evidence of Wernicke’s encephalopathy should be immediately treated with intravenous thiamine followed by oral thiamine for several Acetate months. Hyperuricaemia occurs (particularly, it is said, in beer drinkers) and can cause acute gout. Neutrophil dysfunction is common even when the neutrophil count is 20 normal, predisposing to bacterial infections (e. There are characteristic facial features which include microcephaly, micrognathia and a short upturned 0 20 40 60 80 100 120 140 160 180 nose. This so-called fetal alcohol syndrome is unlike that Blood alcohol concentration (mg/100 mL) reported in severely undernourished women. The patient should be nursed in a quiet environment with careful attention to fluid and electrolyte Acute effects of alcohol balance. Benzodiazepines (intravenous if necessary, Chapters • Central effects include disinhibition, impaired 18 and 22) are usually effective in terminating prolonged with- judgement, inco-ordination, trauma (falls, road traffic drawal seizures – if they are ineffective the diagnosis should accidents), violence and crime. Psychiatric assessment and social support • Convulsions, enhancement of sedative drugs. Delirium tremens occurs in less • Dependence than 10% of alcoholic patients withdrawing from • Behavioural changes alcohol. Psychological and social management: Some form of psychological and social management is important to help the patient to remain abstinent. Whatever approach is used, Medical uses of alcohol the focus has to be on abstinence from alcohol. Systemic alcohol is minority of patients may be able to take up controlled used in poisoning by methanol or ethylene glycol, since it drinking subsequently, but it is impossible to identify this competes with these for oxidation by alcohol dehydrogenase, group prospectively, and this should not be a goal of slowing the production of toxic metabolites (e. Management of alcohol withdrawal Alcohol-sensitizing drugs: These produce an unpleasant Awithdrawal syndrome develops when alcohol consumption reaction when taken with alcohol. The only drug of this type is stopped or severely reduced after prolonged heavy alcohol used to treat alcoholics is disulfiram, which inhibits aldehyde intake. Several features of acute withdrawal are due to auto- dehydrogenase, leading to acetaldehyde accumulation if nomic overactivity, including hypertension, sweating, tachy- alcohol is taken, causing flushing, sweating, nausea, cardia, tremor, anxiety, agitation, mydriasis, anorexia and headache, tachycardia and hypotension. These are most severe 12–48 hours after stopping may occur if large amounts of alcohol are consumed. Some small amounts of alcohol included in many medicines may be patients have seizures (‘rum fits’ generally 12–48 hours post sufficient to produce a reaction and it is advisable for the abstinence). A third set of symptoms consists of alcohol with- patient to carry a card warning of the danger of alcohol drawal delirium or ‘delirium tremens’ (acute disorientation, administration. Disulfiram also inhibits phenytoin severe autonomic hyperactivity, and hallucinations – which metabolism and can lead to phenytoin intoxication. Delirium tremens often follows after with- Unfortunately, there is only weak evidence that disulfiram drawal seizures and is a medical emergency.
For technical rea- sons safe lithium 150mg professional english medicine, a number of infections cannot fulfill the postulates in their strictest sense as formulated by R buy generic lithium 150mg on-line treatment writing. In the medical teachings of Hippocrates discount lithium amex treatment jokes, the cause of infections occurring fre- quently in a certain locality or during a certain period (epidemics) was sought in “changes” in the air according to the theory of miasmas. This concept, still reflected in terms such as “swamp fever” or “malaria,” was the predominant academic opinion until the end of the 19th century, despite the fact that the Dutch cloth merchant A. At the time, general acceptance of the notion of “spontaneous generation”—creation of life from dead organic material—stood in the way of implicating the bacteria found in the corpses of infection victims as the cause of the deadly diseases. It was not until Pas- teur disproved the doctrine of spontaneous generation in the second half of the 19th century that a new way of thinking became possible. By the end of that century, microorganisms had been identified as the causal agents in many familiar diseases by applying the Henle-Koch postulates formulated by R. The History of Infectious Diseases 3 The Henle–Koch Postulates 1 The postulates can be freely formulated as follows: & The microorganism must be found under conditions corresponding to the pathological changes and clinical course of the disease in question. However, the fact that these conditions are not met does not necessarily exclude a contribution to disease etiology by a pathogen found in context. In particular, many infections caused by subcellular entities do not fulfill the postulates in their classic form. The Present The frequency and deadliness of infectious diseases throughout thousands of years of human history have kept them at the focus of medical science. The development of effective preventive and therapeutic measures in recent dec- ades has diminished, and sometimes eliminated entirely, the grim epidemics of smallpox, plague, spotted fever, diphtheria, and other such contagions. As a result of these developments, the attention of medical researchers was diverted to other fields: it seemed we had tamed the infectious diseases. Previously unknown pathogens causing new diseases are being found and familiar organisms have demonstrated an ability to evolve new forms and reassert themselves. The origins of this reversal are many and complex: human behavior has changed, particularly in terms of mobility and nutrition. Further contributory factors were the in- troduction of invasive and aggressive medical therapies, neglect of estab- lished methods of infection control and, of course, the ability of pathogens to make full use of their specific genetic variability to adapt to changing con- ditions. The upshot is that physicians in particular, as well as other medical professionals and staff, urgently require a basic knowledge of the pathogens involved and the genesis of infectious diseases if they are to respond effec- tively to this dynamism in the field of infectiology. Prokaryotic and Eukaryotic Microorganisms According to a proposal by Woese that has been gaining general acceptance in recent years, the world of living things is classified in the three domains bac- teria, archaea, and eucarya. In this system, each domain is subdivided into Kayser, Medical Microbiology © 2005 Thieme All rights reserved. This domain includes the kingdom of the heterotrophic eubacteria and includes all human pathogen bacteria. The other kingdoms, for instance that of the photosynthetic cyanobacteria, are notpathogenic. It is estimated that bacterial spe- cies on Earth number in the hundreds of thousands, of which only about 5500 have been discovered and described in detail. This domain includes forms that live under extreme environmental con- ditions, including thermophilic, hyperthermophilic, halophilic, and methanogenic microorganisms. The earlier term for the archaea was archaebacteria (ancient bac- teria), and they are indeed a kind of living fossil. Thermophilic archaea thrive mainly in warm, moist biotopes such as the hot springs at the top of geothermal vents. The hyperthermophilic archaea, a more recent discovery, live near deep-sea volcanic plumes at temperatures exceeding 1008C. The plant and animal kingdoms (animales and plantales) are all eukaryotic life forms. These organisms are obligate intracellular parasites that are able to reproduce in certain human cells only and are found in two stages: the infectious, nonreproductive particles called elementary bodies (0. These organisms are obligate intracellular parasites, rod- shaped to coccoid, that reproduce by binary transverse fission. Theyare found in a wide variety of forms, the most common being the coccoid cell (0. Fungi (Mycophyta) are nonmotile eukaryotes with rigid cell walls and a classic cell nucleus. They contain no photosynthetic pigments and are carbon heterotrophic, that is, they utilize various organic nutrient substrates (in contrast to carbon autotrophic plants). Of more than 50 000 fungal spe- cies, only about 300 are known to be human pathogens. Protozoa are microorganisms in various sizes and forms that may be free-living or parasitic. They possess a nucleus containing chromo- somes and organelles such as mitochondria (lacking in some cases), an en- Kayser, Medical Microbiology © 2005 Thieme All rights reserved. Host–Pathogen Interactions 7 doplasmic reticulum, pseudopods, flagella, cilia, kinetoplasts, etc. Many para- sitic protozoa are transmitted by arthropods, whereby multiplication and 1 transformation into the infectious stage take place in the vector. Medically signif- icant groups include the trematodes (flukes or flatworms), cestodes (tape- worms), and nematodes (roundworms). These animals are characterized by an external chitin skele- ton, segmented bodies, jointed legs, special mouthparts, and other specific features. Their role as direct causative agents of diseases is a minor one (mites, for instance, cause scabies) as compared to their role as vectors trans- mitting viruses, bacteria, protozoa, and helminths. Host–Pathogen Interactions & The factors determining the genesis, clinical picture and outcome of an infection include complex relationships between the host and invading or- ganisms that differ widely depending on the pathogen involved. Despite this variability, a number of general principles apply to the interactions be- tween the invading pathogen with its aggression factors and the host with its defenses. Since the pathogenesis of bacterial infectious diseases has been re- searched very thoroughly, the following summary is based on the host–in- vader interactions seen in this type of infection. The determinants of bacterial pathogenicity and virulence can be outlined as follows: & Adhesion to host cells (adhesins). The above bacterial pathogenicity factors are confronted by the following host defense mechanisms: & Nonspecific defenses including mechanical, humoral, and cellular sys- tems. The response of these defenses to infection thus involves the correlation of a number of different mechanisms. Primary, innate defects are rare, whereas acquired, sec- ondary immune defects occur frequently, paving the way for infections by microorganisms known as “facultative pathogens” (opportunists). The terms pathogenicity and virulence are not clearly defined in their relevance to microorganisms. It has been proposed that pathogenicity be used to characterize a particular species and that virulence be used to describe the sum of the disease-causing properties of a population (strain) of a pathogenic species (Fig. Determinants of Bacterial Pathogenicity and Virulence Relatively little is known about the factors determining the pathogenicity and virulence of microorganisms, and most of what we do know concerns the disease-causing mechanisms of bacteria. Host–Pathogen Interactions 11 Virulence, Pathogenicity, Susceptibility, Disposition 1 virulent strain avirulent type or var (e. The terms disposi- tion and resistance are used to characterize the status of individuals of a suscep- tible host species.