levinson questions Flashcards
clinical case 14: a 40 yo woman has blurred vision and slurred speech. she is afebrile. sie is famous in her neighborhood for her home-canned vegetables and fruits.
diagnosis?
botulism caused by clostridium botulinum. botulinum toxin causes a descending paralysis that starts with the cranial nerves, typically appearing initially as diplopia. the toxin is a protease that cleaves the proteins involved in release of acetylcholine at the neuromuscular junction. treat with antiserum immediately. confirm diagnosis with mouse protection test using a sample of food suspected of containing the toxin. wound botulism occurs in heroin users, especially in those who “skin pop.”
clinical case 42: a 20 yo man fell off his motorcycle and suffered a compound fracture of the femur. the fracture was surgically reduced and the wound was debrided. forty-eight hours later, he spiked a fever and the wound are became necrotic. crepitus was felt, and a foul-smelling odor was perceived originating from the wound. makred anemia and a white blood count of 22,800 were found. gram stain of the exudate showed large gram-positive rods. colonies grew on blood agar incubated anaerobically but not aerobically.
diagnosis?
gas gangrene cause by clostridium perfringens. the main virulence factor produced by this organism is an exotoxin that is a lecithinase. it causes necrosis of tissue and lysis of rbcs. the spores of the organisms are in the soil and enter at the wound site. a foul-smelling exudate is characteristic of infections caused by anaerobic bacteria.
28: each of the following statements concerning exotoxins is correct except:
A: when treated chemically, some exotoxins lose their toxicity and can be used as immunogens in vaccines
B: some exotoxins are capable of causing disease in purified form, free of any bacteria
C: some exotoxins act in the GI tract to cause diarrhea
D: some exotoxins contain lipopolysaccharides as the toxic component
D
33: each of the following statements concerning exotoxins is correct except:
A: exotoxins are polypeptides
B: exotoxins are more easily inactivated by heat than are endotoxins
C: exotoxins are less toxic than the same amount of endotoxins
D: exotoxins can be converted to toxoids
C
A: diphtheria toxin B: tetanus toxin C: botulinum toxin D: toxic shock syndrome toxin E: cholera toxin
47: causes paralysis by blocking release of AcH
C
A: diphtheria toxin B: tetanus toxin C: botulinum toxin D: toxic shock syndrome toxin E: cholera toxin
48: inhibits protein synthesis by blocking elongation factor 2
A
A: diphtheria toxin B: tetanus toxin C: botulinum toxin D: toxic shock syndrome toxin E: cholera toxin
49: stimulates T cells to produce cytokines
D
A: diphtheria toxin B: tetanus toxin C: botulinum toxin D: toxic shock syndrome toxin E: cholera toxin
50: stimulates the production of cyclic AMP by adding ADP-ribose to a G protein
E
A: diphtheria toxin B: tetanus toxin C: botulinum toxin D: toxic shock syndrome toxin E: cholera toxin
51: inhibits the release of inhibitory neurotransmitters causing muscle spasms
B
65: the most important protective function of the antibody stimulated by tetanus immunization is:
A: to opsonize the pathogen (clostridium tetani)
B: to prevent growth of the pathogen
C: to prevent adherence of the pathogen
D: to neutralize the toxin of the pathogen
D
82: the pathogenesis of which one of the following organisms is most likely to involve invasion of the intestinal mucosa?
A: vibrio cholerae
B: shigella sonnei
C: enterotoxigenic escherichia coli
D: clostridium botulinum
B
86: each of the following statements concerning clostridia is correct except:
A: pathogenic clostridia are found both in the soil and in the normal flora of the colon
B: antibiotic-associated (pseudomembranous) colitis is due to a toxin produced by C. Difficile
C: anaerobic conditions at the wound site are not required to cause tetanus, because spores will form in the presence of oxygen
D: botulism, which is caused by ingesting preformed toxin, can be prevented by boiling food prior to eating
C
111: each of the following statements concerning exotoxins is correct except:
A: some strains of escherichia coli produce an enterotoxin that causes diarrhea
B: cholera toxin acts by stimulating adenylate cyclase
C: diphtheria is caused by an exotoxin that inhibits protein synthesis by inactivating an elongation factor
D: botulism is caused by a toxin that hydrolyzes lecithin (lecithinase), thereby destroying nerve cells
D
122: each of the following statements concerning clostridium perfringens is correct except:
A: it causes gas gangrene
B: it causes food poisioning
C: it produces an exotoxin that degrades lecithin and causes necrosis and hemolysis
D: it is a gram-negative rod that does not ferment lactose
D
123: each of the following statements concerning clostridium tetani is correct except:
A: it is a gram-positive, spore forming rod
B: pathogenesis is due to the production of an exotoxin that blocks inhibitory neurotransmitters
C: it is a facultative organism; it will grow on a blood agar plate in the presence of room air
D: its natural habitat is primarily the soil
C
127: which one of the following statements concerning immunization against diseases caused by clostridia is correct?
A: antitoxin against tetanus protects against botulism as well, because the two toxins share antigenetic sites
B: vaccines containing alpha toxin (lecithinase) are effective in protecting against gas gangrene
C: the toxoid vaccine against c. diff. infection should be administered to the immunocompromised
D: immunization with tetanus toxoid induces effective protection against tetanus toxin
D
130: each of the following statements concerning wound infections caused by Clostridium perfringens is correct except:
A: an exotoxin plays a role in pathogenesis
B: gram-positive rods are found in the exudate
C: the organism grows only in human cell culture
D: anaerobic culture of the wound site should be ordered
C
clinical case questions, case 26:
your patient is a 70 yo man with a fever of 40 C and a very painful cellulitis of the right buttock. the skin appears necrotic, and there are several fluid-filled bullae. creptius can be felt, indicating gas in the tissue. a gram stain of the exudate reveals large gram-positive rods
of the following, which one is the most likely cause?
A: clostridium perfringens
B: bacillus anthracis
C: corynebacterium diphtheriae
D: actinomyces israelii
A
PE II: 11
a 6 yo boy fell and sustained a deep wound from a rusty nail that penetrated his thigh. his mother removed the nail and cleaned the wound with soap and water. the next morning, he had a temp of 102 F and his thigh was very painful and swollen. in the ER, crepitus was noted. a gram stain of exudate revealed large gram positive rods. which one of the following is the most likely cause?
A: actinomyces israelii B: clostricium perfringens C: clostridium tetani D: listeria monocytogenes E: mycobacterium fortuitumchelonei complex F: nocardia asteroides G: pseudomonas aeruginosa
B
10: each of the following statements concerning the normal flora is correct except:
A: the most common organism found on the skin is staphylococcus epidermidis
B: escherichia coli is a prominent member of the normal flora of the throat
C: the major site where bacteroides fragilis is found is the colon
D: one of the most common sites where staphylococcus aureus is found is the nose
B
36: each of hte following statements concerning the normal flora is correct except:
A: the normal flora of the colon consists predominantly of anaerobic bacteria
B: the presence of the normal flora prevents certain pathogens from colonizing the upper respiratory tract
C: fungi (eg yeasts) are not members of the normal flora
D: organisms of the normal flora are permanent residents of the body surfaces
C
38: each of the following statements concerning the normal flora is correct except:
A: streptococcus mutans is found in the mouth and contributes to the formation of dental caries
B: the predominant organisms in the alveoli are viridans streptococci
C: bacteroides frangilis is found in greater numbers than escherichia coli in the colon
D: candida albicans is part of the normal flora of both men and women
B
55: each of the following organisms is an important cause of UTI except:
A: escherichia coli
B: proteus mirabilis
C: klebsiella pneumoniae
D: bacteroides fragilis
D
56: your patient is a 30 yo woman with nonbloody diarrhea for the past 14 hours. which one of the following organisms is least likely to cause this illness?
A: clostridium difficile
B: streptococcus pyogenes
C: shigella dysenteriae
D: salmonella enteritidis
B
58: a 50 yo homeless alcoholic has a fever and is coughing up 1 cup of green, foul-smelling sputum per day. you suspect that he may have a lung abscess. which one of the following pairs of organisms is most likely to be the cause?
A: listeria monocytogenes and legionella pneumophila
B: nocardia asteroides and mycoplasma pneumoniae
C: fusobacterium nucleatum and peptostreptococcus intermedius
D: clostridium perfringens and chlamydia psittaci
C
64: which one of the following host defense mechanisms is the most important for preventing dysentery caused by salmonella?
A: gastric acid
B: salivary enzymes
C: normal flora of the mouth
D: alpha interferon
A
75: your patient is a 70 yo man who underwent bowel surgery for colon cancer 3 days ago. he now has a fever and abdominal pain. you are concerned that he may have peritonitis. which one of the following pairs of organisms is most likely to be the cause?
A: bacteroides fragilis and klebsiella pneumoniae
B: bordetella pertussis and salmonella enteritidis
C: actinomyces israelii and campylobacter jejuni
D: clostridium botulinum and shigella dysenteriae
A
79: your patient has a brain abscess that was detected 1 month after a dental extraction. which one of the following organisms is most likely to be involved?
A: anaerobic streptococci
B: mycobacterium smegmatis
C: lactobacillus acidophilus
D: mycoplasma pneumoniae
A
87: each of the following statements concerning bacteroides fragilis is correct except:
A: B. fragilis is a gram-negative rod that is part of the normal flora of the colon
B: B. fragilis forms endospores, which allow it to survive in the soil
C: the capsule of B. fragilis is an important virulence factor
D: B. fragilis infections are characterized by foul-smelling pus
B
92: five days ago a 65 yo woman with a lower UTI began taking ampicillin. she now has a fever and severe diarrhea. of the organisms listed, which one is the most likely to be the cause of the diarrhea?
A: clostridium difficile
B: bacteroides fragilis
C: proteus mirabilis
D: bordetella pertussis
A
105: each of the following statements concerning actinomyces and nocardia is correct except:
A: a. israelii is an anaerobic rod found as part of the normal flora in the mouth
B: both actinomyces and nocardia are branching, filamentous rods
C: N. asteroides causes infections primarily in immunocompromised patients
D: infections are usually diagnosed by detecting a significant rise in antibody titer
D
A: bacteroides fragilis
B: haemophilus influenzae
C: pseudomonas aeruginosa
D: chlamydia pneumoniae
158: anaerobic gram-negative rod that is an important cause of peritonitis
A
extended matching: 560: causes peritonitis; is an obligate anaerobe
A: escherichia coli B: shigella sonnei C: salmonella typhi D: salmonella enteritidis E: proteus mirabilis F: pseudomonas aeruginosa G: vibrio cholerae H: campylobacter jejuni I: helicobacter pylori J: bacteroides fragiis
J
clinical case questions case 9:
your patient is a 27 yo woman who was treated with oral ampicillin for cellulitis caused by strep. pyogenes. several days later, she developed bloody diarrhea. you suspect that she may have pseudomembanous colitis.
regarding the causative organism of pseudomembranous colitis, which one of the following is the most accurate?
A: it is an aerobic gram-positive rod that produces exotoxins
B: it is a common-shaped gram-negative rod that grows best at 41 C
C: it is an obligate intracellular parasite that grows in cell culture but not on blood agar
D: it is a yeast that forms germ tubes when incubated in human serum at 37 C
A
clinical case questions case 15:
your patient is a 20 yo man who was in a fist fight and suffered a broken jaw and lost two teeth. several weeks later, he developed an abscess at the site of the trauma that drained to the surface of the skin, and yellowish granules were seen in the pus.
regarding this disease, which one of the following is most accurate?
A: the causative organism is a gram-positive rod that forms long filaments
B: the causative organism is a comma-shaped gram-negative rod that produces an exotoxin which increases cyclic AMP
C: the causative organism cannot be seen in the gram stain but can be seen in an acid-fast stain
D: a combination of gram-negative cocci and spirochetes cause this disease
A
clinical case questions case 26:
your patient is a 70 yo man with a fever of 40 C and a very painful cellulits of the right buttock. the skin appears necrotic, and there are several fluid-filled bullae. crepitus can be felt, indicating gas in the tissue. a gram stain of the exudate reveals large gram-positive rods
of the following, which one is the most likely cause?
A: clostridium perfringens
B: bacillus anthracis
C: corynebacterium diphtheriae
D: actinomyces israelii
A
clinical case questions case 40:
your patient is a 40 yo woman with systemic lupus erythematosus who is being treated with high-dose prednisone during a flare of her disease. she develops a fever to 38 C and a cough productive of a small amount of greenish sputum. on physical examination, you hear coarse breath sounds in the left lower lobe. chest xray reveals an infiltrate in that region. gram stain of the sputum reveals long filaments of gram-positive rods.
which one of the following organisms is the most likely cause of this disease?
A: mycobacterium kansasii
B: listeria monocytogenes
C: nocardia asteroides
D: mycoplasma pneumoniae
C
clinical case questions case 43:
your patient is a 62 yo woman with a history of carcinoma of the sigmoid colon that was removed 5 days ago. the surgery was complicated by the escape of bowel contents into the peritoneal cavity. she now has fever and pain in the perineum and left buttock. on physical examination, her temp is 39 C and myonecrosis with a foul-smelling discharge is found. a gram stain of the exudate reveals gram-negative rods
of the following, which one is the most likely organism to cause this infection?
A: helicobacter pylori
B: bacteroides fragilis
C: salmonella typhi
D: vibrio parahaemolyticus
B
PE II: 16
an 80 yo man had a carcinoma of the colon removed 3 days ago. he was doing well until this morning, when he spiked a fever to 39 C and complained of severe abdominal pain. examination revealed a boardlike abdomen indicative of peritonitis. he was taken to the OR where it was discovered that his anastomosis had broken down and bowel contents had spilled into the peritoneal cavity. a foul-smelling exudate was observed. a gram stain of the peritoneal exudate revealed many gram-negative rods. which one of the following sets of bacteria is the most likely cause of this infection?
A: escherichia coli and brucella melitensis
B: enterobacter cloacae and salmonella enteritidis
C: fusobacterium nucleatum and bacteroides ragilis
D: haemophilus influenzae and actinomyces israelii
E: shigella dysenteriae and serratia marcescens
C
clinical case 5: a 12 yo boy has a painful arm that he thought he had injured while pitching in a little league baseball game. the pain has gotten worse over a 2-week period, and he now has a temperature of 100 F. X-ray of the humerus reveals raised periosteum. aspirate of lesion reveals gram positive cocci in clusters.
diagnosis?
osteomyelitis caused by staphylococcus aureus. this organism is the most common cause of osteomyelitis in children. osteomyelitis in prosthethic joints is often caused by staph. epidermidis.
clinical case 24: a 34 yo man was in his usual state of health until last night, when he felt feverish, had a shaking chill, and became short of breath at rest. T 39 C, BP 110/60, P 104, R 18. scattered rales were heard in both bases. a new murmur consistent with tricuspid insufficiency was heard. needle tracks were seen on both forearms. gram-positive cocci in clusters grew in blood culture.
diagnosis?
acute endocarditis caused by staph. aureus. this organism is the most common cause of acute endocarditis in IV drug users. the valves on the right side of the heart are often involved
clinical case 30: a 24 yo woman experienced the sudden onset of high fever, myalgias, vomiting, and diarrhea. her vital signs were T 40 C, BP 70/30, P 140, R 30. A sunburn-like rash appeared over most of her body. blood cultures and stool cultures are negative. she is recovering from a surgical procedure on her maxillary sinus and the bleeding was being staunched with nasal tampons. gram positive cocci in clusters were seen in blood adherent to the nasal tampon.
diagnosis?
toxic shock syndrome caused by staph aureus. toxic shock syndrome toxin is a superantigen that stimulates the release of large amounts of cytokines from many helper T cells
A: diphtheria toxin B: tetanus toxin C: botulinum toxin D: toxic shock syndrome toxin E: cholera toxin
49: stimulates T cells to produce cytokines
D
52: an outbreak of sepsis caused by staph. aureus has occurred in the newborn nursery. you are called upon to investigate. according to your knowledge of the normal flora, what is the most likely source of the organism?
A: colon
B: nose
C: throat
D: vagina
B
62: the coagulase test, in which the bacteria cause plasma to clot, is used to distinguish:
A: streptococcus pyogenes from enterococcus faecalis
B: streptococcus pyogenes from staphylococcus aureus
C: staphylococcus aureus from staphylococcus epidermidis
D: staphylococcus epidermidis from neisseria meningitidis
C
63: which one of the following is a virulence factor for staphylococcus aureus?
A: a heat-labile toxin that inhibits glycine release at the inter-nuncial neuron
B: an oxygen-labile hemolysin
C: resistance to novobiocin
D: protein A that binds to the Fc portion of IgG
D
74: each of the following statements concerning staphylococcus aureus is correct except:
A: gram-positive cocci in grape-like clusters are seen on gram-stained smear
B: the coagulase test is positive
C: treatment should include a beta-lactamase resistant penicillin
D: endotoxin is an important pathogenic factor
D
78: two hours after a delicious thanksgiving dinner of barley soup, roast turkey, stuffing, sweet potato, green beans, cranberry sauce, and pumpkin pie topped with whipped cream, the Smith family of four experience vomiting and diarrhea. which one of the following organisms is most likely to cause these symptoms?
A: shigella flexneri
B: campylobacter jejuni
C: staphylococcus aureus
D: salmonella enteritidis
C
88: each of the following statements concerning staphylococci is correct except:
A: S. aureus is differentiated from S. epidermidis by the production of coagulase
B: S. aureus infections are often associated with abscess formation
C: the majority of clinical isolates of S. aureus produce penicillinase; therefore, penicillin G should not be used for antibiotic therapy for S. aureus infections
D: scalded skin syndrome caused by S. aureus is due to enzymatic degradation of epidermal desmosomes by catalase
D
93: the pathogenesis of which one of the following diseases does not involve an exotoxin?
A: scarlet fever
B: typhoid fever
C: toxic shock syndrome
D: botulism
B
107: tissue degrading enzymes play an important role in the pathogenesis of several bacteria. which one of the following is not involved in tissue or cell damage?
A: lecithinase of clostridium perfringens
B: hyaluronidase of streptococcus pyogenes
C: M protein of streptococcus pneumoniae
D: leukocidin of staphylococcus aureus
C
116: each of the following statements concerning enterotoxins is correct except:
A: enterotoxins typically cause bloody diarrhea with leukocytes in the stool
B: staphylococcus aureus produces an enterotoxin that causes vomiting and diarrhea
C: vibrio cholerae causes cholera by producing an enterotoxin that increases adenylate cyclase activity within the enterocyte
D: escherichia coli enterotoxin mediates ADP-ribosylation of a G protein
A
