Mosby Review - Section 6 Microbiology and Public Health

Environmental Health

Environmental Health

Epidemiology and Disease Management

Epidemiology and Disease Management

Principles of Microbiology

Principles of Microbiology

10. Why are gram-negative bacteria more resistant to antimicrobial agents (compared with gram-positive bacteria? a. the peptidoglycan layer in gram-negative bacteria is thicker b. there is an outer membrane c. all medically important gram-negative bacteria form endospores d. a capsule forms a physical barrier in all gram-negative bacteria

10. B. The outer membrane, made up of lipopolysaccharides, is present only in gram-negative bacteria and acts as a protective barrier to the passage of many molecules, including certain antimicrobial agents. Peptidoglycan is thicker in gram-positive bacteria, and neither capsules nor endospores are present in all gram-negative bacteria.

10. Which of the following terms describes an epidemiological study where exposed and non-exposed populations are identified and followed over time? a. cohort study b. case-control study c. descriptive study d. cross-sectional study

10. a. Analytical studies test the relationship between a health condition and possible risk factors that may increase the risk of that condition. Cohort study is one type of analytical studies where a group of healthy people who vary in the degree of their exposure are followed over time.

10. Which of the following organisms does NOT cross the placental barrier and cause congenital defects in humans? a. cytomegalovirus b. Toxoplasma gondii c. rubella virus d. herpes simplex virus, type 2

10. d. Herpes simplex virus type 2 (HSV-2) causes neonatal herpes, which originates from contact with active vesicular lesions within the birth canal. Despite their association with neonatal infections, neither HSV-1 nor HSV-2 can cross the placenta and cause congenital diseases.

11. Which of the following rates is calculated by dividing all current cases of a disease (old and new) by the total population? a. incidence rate b. prevalence rate c. attack rate d. case-fatality rate

11. B. Prevalence rate refers to the number of cases that exist at one point in time. It measures the extent of the disease in the community by counting all cases (old and new). It is affected by the duration of the disease.

11. Which of the following stains is considered differential? a. capsule stain b. crystal violet c. malachite green d. acid-fast stain

11. D. Grain stain and acid-fast stain are two important differential stains, both based on the cell wall constituents of bacteria. Gram stain differentiates between gram-positive and gram-negative bacteria, and acid-fast stain differentiates between acid-fast and non—acid-fast bacteria.

11. What is the most commonly reported tick-borne disease seen in the United States? a. AIDS b. Lyme disease c. Rocky Mountain spotted fever d. syphilis

11. b. Lyme disease is spread by the deer tick (the nymph phase). It is considered the most commonly reported tick-borne disease in the United States. Of the other choices, the only other tick-borne condition is Rocky Mountain spotted fever, which is not reported as often as is Lyme disease. Syphilis and AIDS are sexually transmitted conditions.

12. If a process kills 90% of the organisms per minute, how many minutes would it take to kill all organisms when starting with 10,000 organisms? a. 5 minutes b. 6 minutes c. 4 minutes d. 3 minutes

12. a. At the rate of 90% killing per minute, there will be 1000 (10%) organisms left at the end of 1 minute, 100 at the end of 2 minutes, 10 at the end of 3 minutes, 1 at the end of 4 minutes, and none at the end of 5 minutes.

12. The term used to describe the occurrence of a disease in a geographic area all the time is: a. Epidemic b. Pandemic c. Epizoodemic d. endemic

12. d. "Endemic" is a term used to describe a disease that exists in a geographic area at all times. For example, heart disease is endemic in Northern America.

12. Neisseria meningitidis uses which of the following virulence factors to its passage from the blood to the meninges? a. flagellum b. pilus c. pyrogenic exotoxin d. polysaccharide capsule

12. d. Neisseria meningitidis is an encapsulated gram-negative coccus that causes meningitis. It is able to survive in the bloodstream to reach the meninges due to its polysaccharide capsule.

13. Koch's postulates are used for which of the following purposes? a. to determine if a given organism causes the given disease b. to determine if the given organism is a bacterium or a fungus c. to determine an organism's growth requirements d. to determine if a given organism will produce an immune response

13. a. Robert Koch, in order to bring a scientific basis for causation of the disease by microorganisms, adopted the principles put forth by Henle. Koch's postulates state that a given organism must be consistently associated with the disease, be able to isolated from the infected host, and then upon introduction into a suitable animal species should give rise to the same disease and then be reisolated.

13. Which of the following has been implicated in hemolytic uremic syndrome (HUS)? a. Salmonella typhi b. Escherichia coli c. Salmonella enteritidis d. Vibrio choler

13. b. HUS has emerged as an important food/water-borne disease since it was first identified in the 1980s. The causative agent is E. coli 0157:H7.

13. The number of new cases of a specific disease within a specific time period in a given population is called the: a. prevalence b. epidemic c. mortality rate d. incidence

13. d. Incidence is the number of new cases of a disease occurring within a specified period in a given population; prevalence is the total number of cases (both old and new) in a given population at risk at a point in time; mortality rate is the measure of death due to a particular cause in a given population; and epidemic is the occurrence of a disease at higher-than-expected incidence with in a population.

14. The single most important measure to prevent the spread of infectious diseases is: a. handwashing b. proper cooking c. canning d. pasteurization

14. a. While cooking, canning, and pasteurization can reduce the chances of food-borne infections, handwashing is acknowledged as the single most important measure to prevent spread of infectious diseases. Handwashing with plain soap aids in the mechanical removal of dirt and microbes present on the hands, including potential pathogens, thus preventing the spread of many infectious diseases.

14. Why would a flagellated strain be more virulent than a nonflagellated strain? a. flagella can kill the white blood cells b. flagella allow the bacteria to negotiate in the mucus layers protecting body surfaces c. flagella give metabolic advantage to the bacterium d. flagella are major adhesive structures

14. b. Flagella are the major locomotor organ of microorganisms. They do not have the capacity to kill phagocytes or have any function in metabolism. Fimbriae are the major adhesive structures, and not flagella.

14. The acid-fast stain is used to identify which of the following types of microorganism? a. genus Treponema b. genus Mycoplasma c. genus Mycobacterium d. genus Corynebacterium

14. c. The acid-fast stain is classically used to identify members of the genus Mycobacterium. These bacteria have complex waxes and lipids in their cell wall that allow differentiation from other medically important bacteria. Although there are other acid-fast—positive bacteria, the most important medically important ones are in genus Mycobacterium. Members include the causative agents of tuberculosis, leprosy, and a variety of AIDS-associated opportunistic infections.

15. What is the type of virus replication where the virus remains dormant in the host cell called? a. lytic cycle b. lysogenic cycle c. abortive infection d. subclinical infection

15. B. In lysogeny, the viral DNA or pro-MA (for RNA viruses) will remain the cell without expressing the full viral replication cycle. It may, however, express some of its genes. In lytic cycle, the cell will be lysed or be destroyed. In abortive infection, which may result in subclinical infection, there is no persistence of the virus.

15. The period of time between exposure to an infectious agent and the onset of disease signs and symptoms is called the: a. prodromal period b. incubation period c. acute phase d. chronic phase

15. b. The interval between the exposure of a host to an infectious agent and the onset of illness is the incubation period. This is the mistaken for the microbe to colonize the host and elaborate the metabolites that would elicit the signs and symptoms of the disease.

15. Which of the following has been implicated in peptic ulcer disease? a. Mycobacterium b. Listeria c. Helicobacter d. Corynebacterium

15. c. Helicobacter emerged as a major pathogen in the 1980s and has been linked to peptic ulcer disease. Once thought to be a result of lifestyle, and treated as such, the majority of ulcers can now be treated and cured by getting rid of the organism. Helicobacter resides in the stomach, protecting itself from the low pH by producing a powerful urease. It is thought to be part of the normal flora in a large percentage of the world's population.

16. Which virus is most characterized by a bullet-shaped capsid? a. Ebola b. influenza c. rabies d. measles

16. C. Rabies is a viral disease caused by the rabies virus. If you examine an electron micrograph of rabies virus particles, you will see a characteristic bullet shape to the capsid. It will be rounded on one end and blunt on the other. Ebola (a filovirus) is more filamentous. Influenza (an orthomyxovirus) and measles (a paramyxovirus) more helically shaped.

16. Eating undercooked pork is associated with an increased risk of infection with which of the following? a. Trichinella b. Escherichia c. Salmonella d. Staphylococcus

16. a. Trichinosis is common in pigs, and if one consumes undercooked infected pork, this roundworm may be transmitted with ingestion. The larvae will hatch in the intestinal tract, move to the skeletal muscles, and encyst. The cysts will eventually calcify, leading to loss of function and pain. Clostridium perfringens is most often found in contaminated beef, Salmonella in contaminated chicken or eggs, and E. coli in contaminated water or hamburger.

16. Bacterial cells reproduce by what mechanism? a. spore formation b. binary fission c. sexual reproduction d. fusion

16. b. Bacteria replicate by asexual binary fission, meaning they grow to a certain size, replicate their DNA, and split into two cells. There is no such thing as sexual reproduction in bacteria. Spores are not indicate replication. environmental survival structures that protect bacteria against harsh environmental conditions and are not used for reproduction. Fusion typically does not indicate replication.

17. Which of the following is the causative agent of genital herpes? a. bacterium b. fungus c. virus d. parasitic worm

17. C. Genital herpes is caused by herpes simplex 2, a member of the herpes virus family.

17. Which of the following best describes a capsomer? a. a viral inclusion body b. the lipid envelope c. a protein spike d. part of a viral capsid

17. D. Most viruses are composed of a piece of nucleic acid inside a protein shell. The protein shell (called a capsid) is made up of individual proteins called capsomers. An inclusion body is an area of active viral replication inside a host cell. The lipid envelope is picked up from the host cell membrane and is phospholipid in composition. Protein spikes are on the capsid and are part of the capsomers when present.

17. Which of the following is TRUE of botulism? a. it is a viral infection b. it is spread by mosquitoes c. it is sexually transmitted d. it is caused by a toxin

17. d. Botulism is caused by the toxin produced by Clostridium botulinum. The toxin is a neurotoxin, affecting the neuromuscular Junction. Nerve impulses are prevented from crossing the synapse; thus, muscles do not contract. Without treatment, death occurs due to respiratory failure.

18. Which of the following is characterized by possessing a thick layer of peptidoglycan? a. all bacteria b. all viruses c. gram-positive bacteria d. gram-negative bacteria

18. C. Both gram-positive and gram-negative cells possess peptidoglycan, a substance unique to bacterial cell walls. The gram-positive bacteria possess a very thick layer. The gram-negative bacteria peptidoglycan is thinner and is covered by an outer layer of lipopolysaccharide. Viruses do not possess any peptidoglycan.

18. In cases of meningitis, in which age group is Neisseria meningitidis most often implicated? a. newborns b. 3 years to 6 years c. young adults, college aged d. older adults, elderly

18. C. Many microbes cause meningitis, and sometimes knowing the age of the patient can give a hint as to what might be the cause. Although Neisseria meningitidis may cause disease in all age groups, it is most often the culprit when the patient is a young adult, of college age, or a military recruit. In newborns, the common first choices are E. coli, Listeria, and Streptococcus agalactiae (group B streptococci). In those who are 3 to 6 years old, consider Haemophilus influenzae. Older adults are often affected by Streptococcus pneumoniae.

18. What is the major cause of death in the United States? a. respiratory infections b. enteric disease c. lifestyle conditions d. lack of prenatal care

18. c. Lifestyle is the prominent factor for cause of death of U.S. citizens Heart disease, obesity, alcohol abuse, substance abuse, tobacco abuse, and diabetes all play roles. With the advent of medical care and immunizations, microbial disease is low on the list of killers it the United States. Respiratory and enteric diseases, however, are the top causes of death worldwide.

19. The most common cause of skin lesions such as boils or abscesses is which of the following bacteria? a. Streptococcus pneumoniae b. Staphylococcus aureus c. Bacillus cereus d. Listeria monocytogenes

19. b. When presented with a case history involving boils or inflamed skin lesions, the first choice should be to rule out Staphylococcus aureus. S. aureus is common on the skin and has many enzymes and virulence factors that cause inflammation. Streptococcus pyogenes may also cause these lesions, however, this option was not given. Streptococcus pneumoniae is not associated with skin infections.

2. Acute rheumatic fever is a nonsuppurative complication that follows infection by which of the following organisms? a. Streptococcus pneumoniae b. Streptococcus pyogenes c. Enterococcus faecalis d. Salmonella typhi

2. b. Approximately 2 weeks after group A streptococcal infection (Streptococcus pyogenes), there is usually pharyngitis, and rheumatic fever may develop. Rheumatic fever is due to an autoimmune reaction between cross-reacting antibodies to certain streptococcal M-proteins and antigens of joints and heart tissue.

2. What characteristic makes agar a useful culture medium? a. it is liquid at room temperature b. it is resistant to contamination by fungi c. it cannot be digested by most microorganisms d. it both melts and solidifies at 100° C

2. c. Agar is a complex polysaccharide obtained from red algae. Although nutrients added to agar are digested by microorganisms, the agar itself is not. It melts at 100° C and solidifies at 42° C and is solid at room temperature.

2. Which term is defined as the "spread of disease from parent to offspring"? a. nosocomial transmission b. horizontal transmission c. vertical transmission d. vector transmission

2. c. Vertical transmission is the spread of a disease from parent to offspring via the gametes, placenta, or milk. Nosocomial infections are those that are obtained at a hospital or clinic. Horizontal transmission of a disease is from one individual to another, not parent to child. Vectors are associated with diseases transmitted from animals to humans.

20. Which of the following water-borne enteric diseases is characterized by massive amounts of fluids passed in the feces? a. salmonellosis b. cholera c. hepatitis A d. E. coli enteritis

20. b. Many organisms may cause diarrhea) disease from drinking of contaminated water. The key in the symptomatology presented is "massive amounts of fluids." This points directly to cholera. The other choices cause a much less severe diarrhea, which is usually not life threatening. Without treatment, patients with cholera can dehydrate within 24 to 48 hours.

21. Which of the following describes the typical appearance of sputum in the patients with pneumonia due to Klebsiella pneumoniae? a. sputum is purulent and rusty color b. sputum is thin and watery c. sputum is bloody and gelatinous d. scant amount of sputum

21. c. Klebsiella pneumoniae produces a large amount of capsular material and slime, giving a gelatinous quality to the sputum. It also produces a lot of necrosis in the lung, causing bleeding in the lung. Rusty or purulent sputum is seen in Streptococcus pneumoniae infection.

22. If a patient is complaining of chest pain, fever, dry cough, and some confusion and has diarrhea and abdominal pain, which of the following organisms is most likely to be the pathogen? a. Bordetella pertussis b. Legionella pneumophila c. Mycobacterium tuberculosis d. Streptococcus pneumoniae

22. b. Legionella pneumophila will cause dry cough, fever, and chest pain due to lung infection resulting in microabscesses and pleurisy. It can cause diarrhea and abdominal pain due release of inflammatory mediators during bacteremia in about one fourth of the patients. The confusion is caused by an unknown mechanism, probably due to impending respiratory failure and hypoxia.

23. Antigenic drift seen in influenza is responsible for which of the following epidemiologic phenomenon? a. a patient who had suffered from influenza previously has partial immunity to the new influenza virus b. a patient who had suffered from influenza previously has no immunity against the new influenza virus c. a patient who had suffered from influenza previously has a booster: effect to his or her immunity d. there is no effect on the immunity of a previously infected patient

23. a. Iii antigenic drift of the influenza virus, a segmented RNA virus, small mutations occur resulting in minor antigenic changes. The antibodies against the original strain may still be able to attach and neutralize the virus but may not be completely effective.

24. Which of the following fungi cause granulomas in the lung that are mistaken for tuberculosis? a. Histoplasma capsulatum b. Blastomyces dermatitidis c. Coccidioides immitis d. Pneumocystis carinii

24. a. Histoplasma capsulatum gives rise to chronic granulomatous lesions that resemble tuberculosis due to the presence of central necrosis that appears like caseating necrosis. Pneutnocystis carinii remains in the alveoli and does not cause granulomas; Blastomyces, and Coccidiodes would more commonly cause a noncaseating or 1/4 suppurative type of granulomas.

25. Which of the following could cause hemolytic uremic syndrome? a. enterohemorrhagic E. coli b. enteroaggregative E. coif c. enteropathogenic E. coli d. enterotoxigenic E. coli

25. a. Enterohemorrhagic E. coli possesses a plasmid DNA that allows it to produce the Shiga toxin, which causes hemolytic uremic syndrome. Other strains of E. coli do not have this toxin-encoding plasmid.

26. Which of the following is one of the characteristics of food intoxication due to preformed toxins? a. very long incubation period b. very short incubation period c. live bacteria must be ingested in the food d. only cold foods are involved in transmitting this disease

26. b. Because the toxin responsible for the clinical symptoms is already present in the food being ingested, such food poisoning is also called food intoxication. The toxin just needs to reach the gastrointestinal tract and exert its action, so typically the incubation period is in hours. It does not involve multiplication of microorganisms in the body and establishment of infection.

27. In which of the following tissues would the larvae of Trichinella spiralis be commonly found? a. striated muscle b. brain c. bones d. lungs

27. a. Trichinella spiralis larvae in humans tend to become encysted in the muscles, including striated muscles, heart muscle, and subcutaneous tissue. It is a dead-end infection in humans.

28. In which of the parasitic infections does the filariform larvae directly penetrate through the skin to infect a new host? a. common round worm b. whipworm c. hookworm d. thread worm

28. c. In hookworms, Ancylostoma duodenale and Necator americanus, the filariform larvae developing in the soil and in intermediate hosts are able to penetrate the intact skin, especially in people walking barefoot. In the other three organisms, the eggs containing rhabditiform larvae are ingested, resulting in human infection.

29. Which of the following causes Whitlow, a lesion commonly seen on the fingers of nurses? a. papillomavirus b. adenovirus c. herpes simplex d. rubella

29. c. Herpes simplex can cause vesicular lesions called Whitlow, which is sometimes seen on the hands of nurses who take care of patients with active herpes lesions. The patient's lesions are found around the mucocutaneous junctions, or the virus is shed in the patient's saliva.

3. Following a barbecue hosted by a hunter who served "pork hamburgers," several guests developed abdominal pain and diarrhea. Their condition progresses about a week later to fever, myalgia, and periorbital edema. Blood analysis shows an increased eosinophil count. Which of the following is the most likely cause of these symptoms? a. anthrax b. botulism c. Escherichia coli gastroenteritis d. trichinosis

3. D. These clinical manifestations are characteristic of trichinosis disease, which is caused by Trichinella spiralis (an intestinal nematode). Humans are infected by eating raw or undercooked pork meat containing larvae that are then encysted in the muscle.

3. Who first used pure cultures to establish the cause of microbial diseases? a. Robert Koch b. Antonie van Lecuwenhock c. Joseph Lister d. Louis Pasteur

3. a. Robert Koch developed pure culture methods to prove that certain microbes cause infectious disease. These came to be known as "Koch's postulates." van Leeuwenhoek used a simple microscope to describe microorganisms. Pasteur, the "father of microbiology," developed pasteurization and studied fermentation. Lister developed antiseptic surgical techniques.

3. Which of the following is NOT a communicable infectious disease? a. chickenpox b. tetanus c. hepatitis B d. influenza

3. b. Communicable infectious diseases are those in which the pathogen is spread from human to human directly or indirectly. Noncommunicable diseases are acquired from one's own microflora or from the nonliving environment such as soil.

30. Which of the following causes erythema infectiosum? a. measles Virus b. varicella zoster virus c. parvovirus B19 d. herpes virus type 6

30. c. Erythema injectiosum, or fifth disease, is an infection characterized by fever, "slapped cheeks" appearance (due to the characteristic rash), and sometimes aplastic anemia because parvovirus B19 Preferentially multiplies in the bone marrow, especially in erythrold cells.

31. What is the etiologic agent that causes a patient to have high fever malaise, and either pneumonia or painful swollen lymph nodes called "bubos?" a. Yersinia pestis b. Shigella sonneri c. Yersinia enterocolitica d. Vibrio cholerae

31. a. Yersinia pestis is the causative agent of bubonic plaque. The plague bacillus reservoir is generally in rodents and is transmitted to humans via flea bites.

32. Which of the following diseases is NOT one of the childhood exanthems? a. Measles b. mumps c. rubella d. rubeola

32. b. The five childhood exanthems are chickenpox (varicella zoster), measles (a paramyxovirus), rubella or German measles (a togavirus), roseola (human herpes virus 6 or 7), and fifth disease (parvovirus B16). Exanthems are characteristic rashes that appear on affected individuals and are accompanied by a fever. Mumps is not associated with a rash.

33. Pertussis can be a serious life-threatening disease due to what bacterial effect on the respiratory system? a. swelling of the epiglottis b. formation of a pseudomembrane c. destruction of the mucociliary action of the respiratory epithelium d. pneumonia

33. C. Pertussis, or whooping cough, is caused by Bordetella pertussis. It is characterized by paroxysmal coughing due to the buildup of mucus and blockage of respiratory passageways.

34. Which type of virus possesses a double-stranded RNA and a double capsid? a. reovirus b. flavivirus c. retrovirus d. alphavirus

34. a. The reoviruses have a double capsid in which the outer capsid consists of structural proteins and the inner capsid contains the enzymes needed to transcribe and replicate the double-stranded RNA.

35. Trypanosoma cruzi causes which of the following diseases? a. African sleeping sickness b. toxoplasmosis c. Chagas disease d. leishmania

35. c. The protozoan Trypanosoma cruzi is transmitted to humans by triatomine bugs indigenous to North, Central, and South America. The disease is characterized by chronic cardiomyopathy, megaesophagus, or megacolon.

36. Tinea unguium is a fungal infection of what part of the body? a. scalp b. between the toes c. nails d. groin

36. c. Fungal infections that are confined to the nonliving layers of the epidermis are referred to as the dermatophytoses, or ringworm. They are caused by a large number of different species of fungus and are classified by the area of the body they infect. Ringworm of the nails is called Tinea unguium. Ringworm of the scalp is called Tinea capitis. Ringworm of the groin is termed Tinea cruris. Generalized ringworm on any smooth area of the skin is termed Tinea corporis.

37. Which of the following is a gram-negative, oxidase-positive, facultative anaerobe? a. Escherichia coil b. Klebsiella pneumoniae c. Pseudomonas aeruginosa d. Haemophilus influenza

37. d. The only gram-negative oxidase-positive facultative anaerobe in the group is Haemophilus influenzae, which causes acute bacterial meningitis. E. coli and Klebsiella are oxidase negative. Pseudomonas is oxidase positive, but it is an aerobe.

38. A patient complains of diarrhea, abdominal pain, and flatulence shortly after returning from a rafting trip in Canada. He admits drinking water infected from the streams. With what flagellate protozoan is he most likely infected? a. Giardia b. Toxoplasmosis gondii c. Entamoeba histolytica d. Leishmania donovani

38. a. The intestinal symptoms described are due to a Giardia lamblia infection. Giardia cysts are very hardy and can be ingested in contaminated water or food. Toxoplasma is a sporozoan protozoan that is transmitted to humans by eating undercooked meat or by exposure to oocysts in the cat litterbox. Entatnoeba infection can be due to eating or drinking contaminated water but is not a flagellate. Leishmania is transmitted via a sand fly vector, causes Kala-Azar (Dumdum fever), and occurs in Asia, Africa, and South America.

39. Which term refers to an "infection that is acquired in a hospital"? a. zoonosis b. fomite c. nosocomial d. septicemia

39. c. Infectious diseases that are obtained in a hospital or clinic are called nosocomial infections. A zoonosis is an infection in which an animal is the natural host for the disease and the disease is transmitted to humans. Fomites are nonliving objects that can be contaminated with a pathogen. Septicemia refers to an infection i the blood.

4. Which precautions would be appropriate to prevent the spread of tuberculosis from an infected patient? a. gowns and gloves are necessary b. proper disposal of urine- or feces-contaminated items c. wear masks and disinfect items contaminated with saliva d. no special precautions are warranted

4. c. Because tuberculosis is spread via the respiratory route, masks may prevent infection. Tuberculosis is not an enteric disease, so urine and feces are not a concern. Gowns and gloves are not required.

4. Which of the following contains LPS (lipopolysaccharides), which forms the basis of endotoxins? a. both gram-positive and gram-negative cells b. gram-positive cells c. gram-negative cells d. fungi

4. c. Endotoxin is an intracellular toxin released from disrupted gram-negative bacteria that can cause severe shock and fever. It is derived from lipopolysaccharides (LPS).

4. All of the following agents cause opportunistic infection in AIDS patients except for: a. Candida b. cytomegalovirus c. Plasmodium d. Mycobacterium avium-intercellular

4. c. Plasmodium is a blood protozoan that causes malaria disease. Humans are infected after being bitten by a female Anopheles mosquito. This is most likely to occur in tropical areas such as Asia, Africa, and Central and South America. This disease is not dependent upon immune-suppressed conditions.

40. Filaria parasites are transmitted by what means? a. ingestion b. arthropod bite c. sexual contact d. penetration through the skin

40. b. Filaria are nematodes that are transmitted via arthropod bites. Examples include Wuchereria bancrofti, which causes elephantiasis, and Onchocera volvulus, which causes river blindness.

41. A patient presents with a high fever, pharyngitis, lymphadenopathy, and lymphocytosis with atypical lymphocytes. Which infectious disease do the signs and symptoms BEST characterize? a. fifth disease b. shingles c. parainfluenza d. infectious mononucleosis

41. d. Infectious mononucleosis (or "mono") is caused by the Epstein-Barr virus, which is a herpesvirus. The disease is most commonly spread by direct oral contact or by saliva-contaminated fomites. Mono is therefore also termed the "kissing disease."

42. Which virus is currently the only poxvirus that causes disease in humans, which appears as papules and nodules on the skin? a. variola major b. vaccinia c. poxvirus of molluscum contagiosum d. varicella zoster

42. c. The variola viruses cause smallpox, which is a disease that was eradicated in the 1970s. The last reported case was in Somalia in 1977. Vaccinia causes cowpox, and varicella is not classified as a poxvirus.

43. Which of the following is NOT a causative agent of the common cold? a. adenovirus b. rhinovirus c. coronavirus d. hantavirus

43. d. The four viruses associated with the common cold are adenovirus, rhinovirus, coronavirus, and coxsackievirus. Hantavirus causes the hantavirus pulmonary syndrome of the lung epithelia obtained by inhalation of airborne particles of dried rodent feces.

44. Pharyngitis with a diffuse erythematous rash appearing on the head and extremities and the appearance of a "strawberry tongue" is descriptive of what disease? a. scarlet fever b. rheumatic fever c. pyoderma d. toxic shock syndrome

44. a. All of the listed diseases are caused by Streptococcus pyogenes, group A streptococci, but the symptoms are characteristic of scarlet fever.

45. Which correctly describes the appearance of Staphylococcus under the microscope? a. gram-negative cocci in clusters b. gram-positive cocci in clusters c. gram-negative cocci in short chains d. gram-positive cocci in short chains

45. b. Staphylococci are gram positive, and they divide in more than one plane, forming clusters.

46. Bacteria are often cultured on blood agar to detect the presence of hemolytic cytotoxins. What type of hemolysis is Beta-hemolysis? a. no hemolysis is detected b. incomplete hemolysis on blood agar c. complete hemolysis d. irregular hemolysis

46. c. a-Hemolysis is incomplete hemolysis, Beta-hemolysis is complete hemolysis, and y-hemolysis is where no hemolysis is detected. P-Hemolysis is the type produced by Streptococcus pyogenes, whereas Streptococcus pneumoniae demonstrates ot-hemolysis.

47. When Staphylococcus aureus enters the blood and it is carried to the bone, it causes an infection given what name? a. osteonecrosis b. osteopenia c. osteolysis d. osteomyelitis

47. d. Besides S. aureus, other organisms can cause osteomyelitis, including various aerobic and anaerobic bacteria, mycobacteria, and fungi.

48. Which food-borne disease is MOST associated with home canning? a. botulism b. cholera c. listerosis d. typhoid fever

48. a. The etiologic agent of botulism is Clostridium botulinum. The disease is due to the presence of spores in poorly sterilized food, such as in home canning. The spores germinate and produce botulinum toxin within the can. Ingestion of the toxin leads to flaccid paralysis of skeletal muscle.

49. The Mantoux test is used to detect prior infection by which agent? a. Clostridium difficile b. Mycobacterium tuberculosis c. Mycobacterium leprae d. Cornybacterium diphtheriae

49. B. The Mantoux test is a screening test for tuberculin sensitivity. A small amount of tuberculin is injected under the skin. If there is a 10-mm red patch of skin produced within 48 hours at the site of injection, prior exposure to TB is indicated.

5. Negri bodies are the major pathological changes seen in which disease? a. Rabies b. bronchiolitis c. croup d. AIDS

5. a. Negri bodies are eosinophilic cytoplasmic inclusion of infected neurons of the central nervous system (CNS) by rabies virus (an enveloped-RNA virus). Transmission is usually from the bite of wild animals. The virus infects the sensory neurons and then is transported to the CNS. Negri bodies then develop within these neurons and are diagnosed by fluorescent-antibody staining of a biopsy specimen.

5. Which of the following epidemiologic terms is defined as the "ratio between the number of new cases of a disease divided by the number of healthy individuals in a population"? a. incidence b. prevalence c. morbidity rate d. mortality rate

5. a. The incidence is the number of new cases of a disease found within a population over a specified time. Prevalence is the percent of all affected individuals in a population, not just new cases.

5. Bacilli can be described as having what shape? a. Spherical b. Spiral c. Spring d. Rod

5. d. Bacilli are rod-shaped bacteria. Cocci are spherical, spirochetes are spiral shaped, and spirilla are spring shaped.

50. Select the TRUE statement concerning rabies. a. the incubation phase is very short; approximately 2 to 10 days b. it is caused by a coronavirus c. it is an encephalitis with neuron degeneration d. it is a spongiform encephalitis caused by a prion

50. c. Rabies is caused by a rhabdovirus that is transmitted to humans via the bite of an infected animal. The disease has a long incubation phase of 60 days to 1 year, followed by a short prodrome phase consisting of flu-like symptoms, and then neurologic symptoms follow due to encephalitis. Coma and death are the ultimate outcomes.

51. A finding, of gram-positive encapsulated diplococci in sputum is indicative of what organism? a. Escherichia coli b. Pseudomonas aeruginosa c. Streptococcus pneumoniae d. Neisseria gonorrhoeae

51. c. Streptococcus pneumoniae is a gram-positive organism, occurring in pairs, and is a common pathogen of the respiratory tract; the other bacteria listed are all gram negative.

52. What term is defined as a "symbiotic relationship in which one benefits and the other is unaffected"? a. commensalism b. parasitism c. mutualism d. antagonism

52. a. Symbiosis is the living together of two organisms in a more or less permanent relationship. Mutualism is where both the partners benefit; parasitism is where one benefits at the expense of the other; and commensalism is when one partner benefits and the other is unaffected.

53. In human beings, the most common habitat of Staphylococcus aureus is the: a. throat b. urethra c. skin d. nasal chamber

53. d. The nose is the most common site of carriage of Staphylococcus aureus. The skin usually has Staphylococcus epidermidis.

54. What clinical sign can usually diagnose many childhood diseases caused by viral infections of the upper respiratory tract? a. type of rash b. type of cough c. type of fever d. incubation period

54. a. Most upper respiratory viral infections of childhood manifest as exanthems (rashes). The distribution and appearance of the rash are quite distinctive for different virus infections (for example, measles, chickenpox, rubella, erythema infectiosum, and roseola). The rash, in combination with other clinical findings, is useful diagnostically.

55. Otitis media and sinusitis are usually preceded by what infection? a. middle ear infection b. infection with Pseudomonas c. nasopharyngeal infection d. lower respiratory tract infection

55. c. Otitis media and sinusitis are usually preceded by nasopharyngeal infection with organisms such as Haemophilus influenzae and Streptococcus pneumoniae.

56. In adults, about 60% of the bacterial pneumonias that require hospitalization are caused by what organism? a. Myeoplasma pneumoniae b. Streptococcus pneumoniae c. Staphylococcus aureus d. Klebsiella pneumonia

56. b. Pneumococcus is the most common cause of bacterial pneumonia in adults that would require hospitalization. Gram-negative bacteria such as Klebsiella cause pneumonia in immunocompromised individuals. Pneumonia due to Mycoplasma is very mild (hence called "walking pneumonia"). Staphylococcus is not a frequent cause of bacterial pneumonia in adults.

57. During which stage of syphilis is the patient noninfectious? a. first stage (primary syphilis) b. second stage (secondary syphilis) c. third stage (tertiary syphilis) d. fourth stage (quaternary syphilis)

57. C. Of the three stages of syphilis, the first two stages are infectious. Tertiary syphilis represents a hypersensitivity reaction to small numbers of Treponema pallidum that persist in the tissues; gummas (granulomatous necrotizing masses) can be seen at this stage. At this stage, the patient is not infectious. There is no fourth stage.

58. When epidemics of bacterial meningitis occur, they usually involve which organism? a. Neisseria meningitidis b. Streptococcus pneumoniae c. Haemophilus influenzae d. Streptococcus pyogenes

58. a. While Neisseria meningitidis, Streptococcus pneurnoniae, and Haemophihis influenzae can all cause bacterial meningitis, for reasons not well understood, only Neisseria meningitidis has the propensity to cause epidemics in crowded and stressed populations.

59. What is the most common etiological agent(s) causing subacute bacterial endocarditis? a. Streptococcus pyogenes b. Pseudomonas aeruginosa c. normal skin or mouth flora d. Escherichia coli

59. C. Virulent bacterial species such as Staphylococcus aureus and Streptococcus pyogenes are usually responsible for acute bacterial endocarditis. However, opportunistic pathogens such as members of the normal flora of skin (Staphylococcus epidermidis) or mouth (a-hemolytic viridans streptococci) are mostly responsible for subacute bacterial endocarditis. This is usually associated with heart valves that are deformed due to a birth defect or rheumatic fever, etc.

6. Which two bacteria genera are spore-forming? a. Bacillus and Clostridium b. Staphylococcus and Streptococcus c. Neisseria and Mycobacteria d. Escherichia and Salmonella

6. a. Bacillus and Clostridium form endospores that are capable of withstanding extremes of temperature, desiccation, radiation, andi chemicals that would ordinarily destroy vegetative cells.

6. A disease that occurs with relative regularity only in the southwesteen United States would be described having what type of disease occurrence? a. pandemic b. epidemic c. sporadic d. endemic

6. d. Endemic diseases are those that occur regularly within a geographical area. Sporadic diseases are randomly distributed cases. Epidemics are sudden outbreaks of a disease within a population, and pandemics are worldwide epidemics.

6. A "slapped-cheek" rash in children is characteristic of which disease? a. papillomavirus b. measles virus c. chickenpox d. parvovirus B19

6. d. Parvovirus B19 causes erythema infectiosum ("slapped cheeks" syndrome, fifth disease). This DNA virus is nonenveloped.

Symptoms of AIDS appear when: a. CD4 counts are <300/milliliter of blood b. CD4 counts are >900/milliliter of blood c. CD8 counts are >1000/milliliter of blood d. CD8 counts are <700/milliliter of blood

60. a. The normal CD4 (Th cells) count is 1000/ml of blood. These cells are the major targets for viral invasion and replication in HIV infection. These cells diminish in numbers as HIV disease progresses. When the CD4 cell counts fall below 300/ml of blood, symptoms of AIDS start appearing (malignancies and opportunistic infections).

7. Which of the following describes a plasmid? a. it is an extrachromosomal DNA for antibiotic resistance b. it is a single-stranded extrachromosomal RNA for toxin resistance c. it is an extrachromosomal DNA for heat resistance d. it is a single-stranded DNA for dehydration resistance

7. a. Plasmids are small genetic elements (extrachromosomal DNA) that are capable of replication within one prokaryotic (bacteria) cell and may be transferred to another cell, which confers a resistance to antibiotic treatment.

7. In 2003, the first cases of severe acute respiratory syndrome (SARS) were reported in Asia. Soon, many cases were reported from four continents. How would this spread of SARS be classified? a. an outbreak b. an epidemic c. sporadic cases d. a pandemic

7. d. A pandemic involves a spread of a communicable disease across more than one continent. An outbreak and an epidemic are geographically limited. Sporadic cases are isolated cases of the communicable disease.

1. Which of the following is the most effective way to sterilize heat-sensitive liquids? a. autoclave b. filtration c. iodine d. freezing

1. b. Filtration removes infectious agents from liquids rather than destroys them. Autoclaving is steam sterilization under pressure (heat), iodine is used as a topical antiseptic, and freezing slows the growth of microbes but does not sterilize.

1. Which of the following is a feature unique to prokaryotic cells? a. they have a cell wall b. they have circular DNA c. they arc unicellular organisms d. they lack ribosomes

1. b. Prokaryotic organisms, such as bacteria, contain circular DNA in their cytoplasm and lack nuclei. Although prokaryotes have cell walls and are unicellular, these are not unique to prokaryotes. For example, plants are eukaryotes with cell walls, and yeasts and protozoa are unicellular eukaryotes. Both prokaryotes and eukaryotes have ribosomes for protein synthesis.

1. A 27-year-old man went to the hospital for a deep laceration on his foot that he received during his construction job. He received a shot for a specific type of organism. This organism is classified as which of the following? a. gram-positive cocci, ferments lactose b. gram-positive rod, anaerobic, and spore forming c. gram-negative bacilli, aerobic, and spore forming d. it is difficult to stain with gram stain

1. B. The organism is Clostridiri tetani, a gram-positive rod. Their spores are widespread in soil, enter through a deep laceration (wound) of the skin, and cause a rigid contraction of the muscle by the organism's toxin (tetanospasmin).

7. A 31-year-old woman with systemic lupus erythematosus (SLE) is found to have a positive serologic test for syphilis (VDRL test). She denies having had sexual contact with a partner who had symptoms of a venereal disease. What would be the next best step to confirm a venereal syphilitic disease? a. reassure her that the test is a false-positive reaction for autoimmune disease b. trace her sexual contact for serological testing c. refer her to a physician to prescribe tetracycline as an antibiotic d. perform a fluorescent treponemal antibody-absorbed (FTA-ABS) test

7. d. Syphilis is caused by Treponema pallidum. The VDRL test is a nonspecific test for syphilis because it mays have a false positive reaction with other infections such as leproy, hepatitis, or SSE. This test result becomes negative after treatment, but FTA-ABS is a specific test for syphilis and remains positive for life.

8. Which is NOT an organism that is transmitted by larva or cercaria that penetrates the skin? a. Ancylostoma duodenale b. Strongyloides stercoralis c. Wuchereria bancrofti d. Schistosoma haematobium

8. c. Humans are infected by Wuchereia bancrofii when the female mosquito (Anopheles or Culex species) deposits infective larvae in the skin. The larva by itself lacks the capability to enter the skin without the mosquito bite, as can the other organisms on the list.

8. Which of the following bacterial structures is MOST involved in adherence? a. capsule b. lipopolysaccharide c. ordinary pili d. O-specific side-chain

8. c. Pili are hairlike filaments that extend from cell surface, are shorter than flagella, and are found mainly on gram-negative bacteria. They mediate the adherence of bacteria to specific receptors on human cell surfaces to initiate infection.

8. Which is a term that refers to a disease that is primarily an infection of animals and is accidentally transmitted to humans? a. sporadic b. secondary infection c. zoonosis d. reservoir

8. c. Zoonoses are primarily maintained in nature by circulation of these pathogens in animals. These animals and their vectors can accidentally transmit the infection to humans who come in contact with animals. These animals serve as a reservoir for these pathogens as in the plague (brucellosis).

9. All of the following procedures are useful for the diagnosis of fungal infection EXCEPT which? a. serology test b. gram stain test c. direct microscopic examination d. culture fungi on Sabouraud's agar

9. B. The gram stain test is useful for prokaryotic cells (bacteria) and not for eukaryotic cells such as fungi. Most of the cell walls of the bacteria have peptidoglycan and lipopolysaccharides that are sensitive to the staining procedures.

9. A patient you treated in the morning has influenza, a viral illness caused by an enveloped RNA virus. Which of the following methods of infection control should you use for your adjusting table? a. sterilization b. pasteurization c. high-level disinfectant d. intermediate-level disinfectant

9. D. Enveloped viruses such as influenza are easily destroyed by intermediate-level disinfectants such as alcohol- based sprays or Lysol.

9. Poliovirus replicates in and causes damage to which of the following structures? a. sensory neuron (dorsal horn of the spinal cord) b. motor neuron (anterior or ventral horn of the spinal cord) c. skeletal muscle fibers d. cardiac muscle fibers

9. b. In the central nervous system, poliovirus preferentially replicates in the motor neurons located in the anterior horn of the spinal canal. Death of these cells results in paralysis of the muscles innervated by those neurons (poliomyelitis disease).

Communicable and Infectious Diseases

Communicable and Infectious Diseases