Question 1 - Single Best Answer
What is an effect of bacteria having a circular chromosome?
Point mutations are rare. DNA gyrase, which introduces supercoils, is a target of antimicrobials. There is no nuclear membrane. There are polycistronic mRNAs. Transcription and translation are coupled in the cytoplasm.
Question 2 - Single Best Answer
Because peptidoglycan is the major element of the cell wall, inhibition of cross-linking by beta-lactam antibiotics will result directly in:
inhibition of endocytosis and exocytosis by the bacteria. inhibition of segregation of the chromosome copies at cell division. lysis of the bacteria. inhibition of genetic exchange. inhibition of active transport.
Question 3 - Single Best Answer
How does peptidoglycan help gram-positive bacteria evade host defenses?
It prevents complement from lysing the bacteria. It prevents phagocytosis because it forms a slime layer. It is directly toxic to neutrophils. It prevents antibody synthesis by antigenic mimicry. It subverts cell-mediated immunity by killing T cells.
Question 4 - Single Best Answer
Each of the following is a characteristic or component of the outer membrane of gram-negative bacteria EXCEPT:
porin proteins lipopolysaccharide second set of electron transport and ATPase complexes resistance to bile salts reduces susceptibility to certain antibiotics
Question 5 - Single Best Answer
Acid fast bacteria:
usually cause disease in the stomach are treated with the same antibiotics as other bacteria are only found in humans grow rapidly in acidic media contain waxes and lipids in their cell wall
Question 6 - Single Best Answer
What is the difference between penicillins and vancomycin?
Vancomycin is active against gram-negatives, while penicillins are active only against gram-positives. Vancomycin binds to the D-Ala-D-Ala while penicillins mimic D-Ala-D-Ala. Resistance to penicillins is usually by point mutation, while resistance to vancomycin is usually by plasmid. Vancomycin resistance is a serious threat to health care, while penicillin resistance is not. Vancomycin inhibits transpeptidation of peptidoglycan while penicillins inhibit polymerization of peptidoglycan backbone.
Question 7 - Single Best Answer
Where is the energy for transpeptidation immediately derived from?
hydrolysis of ATP proton motive force cleaving the backbone cleaving off the terminal D-Ala Phosphoenyl pyruvate (PEP)
Question 8 - Single Best Answer
What is the most important characteristic of the third amino acid of the side chain in the peptidoglycan building block?
It must have an amino-containing side group. It must be hydrophobic It must be acidic It must be an aromatic amino acid It must be a glycine
Question 9 - Single Best Answer
What are penicillin binding proteins?
Mechanisms of resistance to beta-lactam antibiotics. Cell surface proteins of gram-negative bacteria Surface proteins of Mycoplasmas Enyzmes involved with peptidoglycan biosynthesis Enzymes involved with capsule production of gram-positive bacteria.
Question 10 - Single Best Answer
The goal of therapy for rheumatic fever caused by Group A streptococci is primarily aimed at:
clearing the bacterial infection of the heart clearing the bacterial infection of the joints clearing the bacteria infection of the pharynx decreasing inflammation, fever, and heart failure decreasing inflammation of the glomeruli
Question 11 - Single Best Answer
Which component of lipopolysaccharide is most likely to be involved with antigenic variety?
Lipid A Core oligosaccharide O-antigen Teichoic acid Beta-hydroxy myristic acid
Question 12 - Single Best Answer
Similarities between diphtheria toxin and pertussis toxin include
they both promote lymphocytosis they both cause pseudomembrane formation they both have ADP-ribosylation activity they are both composed of 5 B subunits and 1 A subunit they both cause deregulation of adenyl cyclase
Question 13 - Single Best Answer
Which of the following membranes of eukaryotic cells does NOT have a similar function in the bacterial cell (cytoplasmic) membrane?
nuclear membrane mitochondrial membrane endoplasmic reticulum cytoplasmic membrane All of the above DO share functions with the bacterial cell membrane.
Question 14 - Single Best Answer
To which aspect of bacterial metabolism/biosynthesis have we NOT produced a clinically useful antibiotic?
folic acid biosynthesis protein synthesis acquisition of iron RNA synthesis DNA synthesis
Question 15 - Single Best Answer
What role do biofilms have in medicine?
They can contaminate implanted medical devices and are difficult to clear with antibiotics. They have reduced the use of standard X-rays because they are more sensitive to irradiation. They prevent graft-versus-host disease. They are useful in culturing viruses. None of the above.
Question 16 - Single Best Answer
How are specialized transduction and F'-mediated genetic exchange related?
They both are mediated by phage. They both involve lysis of bacterial cells. They both involve a genetic element picking up DNA from a bacterial chromosome. These are the most prevalent mechanisms of genetic exchange related to virulence and antibiotic resistance. The genetic exchange does not involve the genome of the original element - only host genes move from cell to cell.
Question 17 - Single Best Answer
The major concern for lysogenic conversion in medicine is that:
most antibiotic resistance is created by this method. since bacteria change from lactose-positive to lactose-negative, laboratory diagnosis becomes more difficult. the transposon can insert itself randomly mediating antigenic variation. bacteria can acquire toxin genes and become virulent. plasmids become conjugative and can move antibiotic resistance among diverse species of bacteria.
Question 18 - Single Best Answer
Which of the following antibiotics would likely have the lowest therapeutic index?
polymyxins cephalosporin sulfamethoxazole rifampin ciprofloxacin
Question 19 - Single Best Answer
Why is clavulanic acid often mixed with amoxicillin?
One is active against gram-positives, while the other is active against gram-negatives. One is bacteriostatic, while the other is bactericidal. They both are active against the same molecular target, hence are synergistic. Clavulanic acid inhibits the resistance mechanism to amoxicillin. None of the above - this is actually an example of antagonism, hence these drugs should never be mixed.
Question 20 - Single Best Answer
What is the mechanism of resistance of methicillin-resistant Staphylococcus aureus?
It possesses an R plasmid with beta-lactamase. It acquired resistant penicillin binding proteins in the past. It is accumulating point mutations as patients fail to complete their courses of treatment. Methicillin is too large to fit through the porins. The bacteria pump the antibiotic out of the cell before it can be active.
Question 21 - Single Best Answer
The normal flora:
does not cause disease. is only found in healthy people. provides no benefit or detriment to the host. causes disease only at surface sites such as the skin or respiratory tract. can cause endogenous disease or infection.
Question 22 - Single Best Answer
Which of the following is NOT a means of preventing the encounter with a pathogen?
Immunizing with pneumococcal vaccine. Immunizing dogs and cats for rabies. Cooking food appropriately. Washing hands between patients. Spraying insecticides for mosquitoes.
Question 23 - Single Best Answer
What is NOT a common virulence factor of bacteria that do NOT spread? NOTE: THIS QUESTION WAS DISCARDED. THE CORRECT ANSWER IS (was) b.
Production of toxins. Invasion into macrophages. Adherence to epithelial cells. Entering the body at mucosal surfaces. All of the above ARE common virulence factors of bacteria that do not spread.
Question 24 - Single Best Answer
What do lipopolysaccharide and superantigens have in common?
They both have lipid and polysaccharide components. They both are made by gram-positive and gram-negative bacteria. They both lyse host cells. They both inhibit protein synthesis. They both act via cytokines produced by the host.
Question 25 - Single Best Answer
Many people experience numerous cases of pharyngitis caused by Streptococcus pyogenes because:
of antigenic variation during the infection process. the infection does not stimulate a measurable immune response. of antigenic variety among the strains. cell-mediated immunity is ineffective against the infection. None of the above - people generally do not experience multiple cases of streptococcal pharyngitis in their life.
Question 26 - Single Best Answer
Bacterial toxins act in each of the following ways EXCEPT:
lysing host cells inhibiting protein synthesis altering cAMP levels inducing apoptosis None of the above - bacterial toxins are known to perform each of the above functions.
Question 27 - Single Best Answer
In general, differential media:
allow most organisms to grow, but make them look dissimilar. allow different bacteria to grow, depending if they are resistant to antibiotics or bile salts. are only useful for gram-positive bacteria. are only useful for differentiating facultative anaerobes from strict anaerobes. enable the differentiation of gram-positive versus gram-negative bacteria.
Question 28 - Single Best Answer
The major way that streptococci are initially differentiated from each other is by:
the catalase test. the coagulase test. hemolysis on blood agar plates. pink color on MacConkey agar. the citrate test.
Question 29 - Single Best Answer
Immunological classifications of gram-negative bacteria include each of the following EXCEPT:
lipopolysaccharide flagella capsule teichoic acid All of the above ARE used to immunologically type gram-negative bacteria.
Question 30 - Single Best Answer
Medically relevant fastidious bacteria generally:
grow very fast. do not cause disease. are not culturable. require complex or rich media. are obligate intracellular pathogens.
Question 31 - Single Best Answer
Bacteria that cause respiratory disease:
are always contagious. do not cause disease at other anatomical sites. never spread beyond the respiratory epithelium. are always extracellular. None of the above are true.
Question 32 - Single Best Answer
Each of the following usually requires ordering the use of a special medium for cultivation EXCEPT:
Mycobacterium tuberculosis Streptococcus pyogenes Bordetella pertussis Corynebacterium diphtheriae Legionella pneumophila
Question 33 - Single Best Answer
Which of the following bacteria has a vaccine that is aimed at preventing the evasion of immune defenses normally part of the bacterial pathogenesis?
Corynebacterium diphtheriae Bordetella pertussis Streptococcus pneumoniae Mycoplasma pneumoniae Streptococcus pyogenes
Question 34 - Single Best Answer
Which of the following best describes the typical course of primary infection with Mycobacterium tuberculosis?
Colonization of the upper respiratory tract, followed by aspiration, followed by severe cough with rust-colored sputum. Hematogenous spread from tissues into the lung parenchyma with coughing up of blood. Direct inhalation into the alveoli with symptomatic disseminated infection (lymphadenopathy, skin rash, high fever, and disseminated intravascular coagulation) Direct inhalation into the alveoli with no symptoms ranging to flu-like symptoms. Colonization of the nasopharynx without symptoms for several years.
Question 35 - Single Best Answer
The vaccine for whooping cough consists of:
7 different polysaccharides conjugated to diphtheria toxoid 23 different polysaccharides the B portion of a toxin whose A subunit inhibits protein synthesis Filamentous Hemagglutinnin (FHA) plus a toxoid a live attenuated virus that contains 7 subunits of RNA
Question 36 - Single Best Answer
Which of the following antibiotics would most likely be used to treat pneumonia caused by Mycoplasma pneumoniae?
erythromycin vancomycin bacitracin amoxicillin carbapenem
Question 37 - Single Best Answer
The method by which Legionella pneumophila evades host defenses is related to:
its carbohydrate capsule. secretion of IgA protease since it colonizes the upper respiratory tract. antigenic variation of its pili used for adherence. its relationship with amoeba in water. its ability to shift the immune response from antibody to cell-mediated.
Question 38 - Single Best Answer
Typical symptoms of Group A streptococcal pharyngitis include all of the following EXCEPT:
doughnut lesions. tonsillar exudates. fever. rhinorrhea. anterior cervical adenopathy.
Question 39 - Single Best Answer
The most contagious period for whooping cough is:
the incubation period. the catarrhal phase. the paroxysmal phase. the convalescent phase. None of the above - whooping cough is not contagious.
Question 40 - Single Best Answer
Which of the following is LEAST likely to cause permanent damage in the lungs of diseased patients?
Mycobacterium tuberculosis Staphylococcus aureus Streptococcus pneumoniae Klebsiella pneumoniae None of the above - ALL of the organisms cause extensive, permanent damage to the lungs from disease
Question 41 - Single Best Answer
When diagnosing pneumonia:
a sputum gram-stain is usually sufficient. a sputum culture is usually sufficient. a blood culture is usually sufficient. a chest X-ray should be performed. serology should always be performed.
Question 42 - Single Best Answer
Reactivation tuberculosis usually occurs in the apical areas of the lung because:
they have the highest oxygen levels. they have the lowest level of immune cells. they are most likely to experience trauma later in life. they are the site most seeded by aspiration. they are the only site initially seeded with the bacteria during primary infection.
Question 43 - Single Best Answer
Multiple drugs are usually prescribed to treat tuberculosis because:
there are high loads of bacteria in infected patients. there is not time to determine sensitivities before treatment is initiated. spontaneous mutations can render the bacteria resistant. all of the above none of the above
Question 44 - Single Best Answer
What percentage of antibiotics in the United States is administered to humans, as opposed to farm animals?
about 90% about 75% about 50% about 25% less than 10%
Question 45 - Single Best Answer
Why does diphtheria toxin act on heart muscle cells?
The A portion of the toxin acts better on the adenyl cyclase of heart cells. Heart cells can synthesize diphthamide in greater amounts than some other cells. The A portion activates an inhibitor of EF2 in heart cells. The B portion of the toxin binds to heart cells. The bacterial pili bind preferentially to heart cells.
Question 46 - Single Best Answer
Mycoplasma pneumonia is most similar to which of the following?
Streptococcal pneumonia Chlamydial pneumonia Legionnaire's disease Streptococcal pharyngitis Staphylococcal pneumonia
Question 47 - Single Best Answer
NAD participates in the action of diphtheria toxin as a
hydrogen acceptor. hydrogen donor. energy source. donor of ADP-ribose. site of binding of the B portion.
Question 48 - Single Best Answer
The energy for glucose transport comes directly from NOTE: This question was discarded. Although Case 43 talked about glucose transport and said glucose gets phosphorylated by PEP as it is transported, it didn¹t say that this provided the energyŠ.but it does.
an energized membrane. ATP. PEP. LPS. NAD.
Question 49 - Single Best Answer
Fermentation and respiration are both methods for the regeneration of what substance?
NAD NADH2 ATP glucose energized membrane
Question 50 - Single Best Answer
The mechanism by which most Streptococcus pneumoniae become resistant to penicillin is somewhat unusual in that:
it is a chromosomal mutation coding for beta-lactamase it is a plasmid gene coding for beta-lactamase it is a chromosomal mutation in penicillin binding proteins it is a plasmid-carried pathway for peptidoglycan synthesis it is a change in the outer membrane that keeps penicillin from entering the cell
Question 51 - Single Best Answer
Antibiotics fed to farm animals for growth enhancement will likely cause:
bacteria to mutate to antibiotic resistance. transposons to jump from plasmids to chromosomes. insertion sequences to transfer between cells. the selection of antibiotic resistant bacteria. antigenic variation.
Question 52 - Single Best Answer
Chloramphenicol acetyl transferase (CAT) can act to inactivate chloramphenical and cause bacteria to be resistant. The genetic information for the CAT is most likely found
on an insertion sequence. on a plasmid. on a prophage. as a chromosomal gene. as a mitochondrial gene.
Question 53 - Single Best Answer
Cystic fibrosis patients are more likely than normal individuals to be colonized with
Staphylococcus aureus and Pseudomonas areuginosa Staphylococcus aureus and Streptococcus pyogenes Pseudomonas areuginosa and Pneumococcus (Streptococcus pneumoniae) Haemophilus influenzae and Pneumococcus Mycobacterium tuberculosis and Haemophilus influenzae
Question 54 - Single Best Answer
A woman that was severely burned in a bus crash caused by terrorists was hospitalized and was doing quite well until her doctor noticed a fruity odor coming from her wounds. He swabbed her burns and sent the swab to the lab. The lab most likely identified a(an):
aerobic rod. anaerobic rod. aerobic coccus. anaerobic coccus. facultatively aerobic coccus in bunches.
Question 55 - Single Best Answer
Apical lung infiltrates are most indicative of
staphylococcal pneumoniae. mycoplasma pneumonia. pneumococcal pneumonia. first exposure to Mycobacterium tuberculosis in immunologically normal individuals. reactivation of tuberculosis.
Question 56 - Single Best Answer
Which of the following best describes the pathogenesis of Staphylococcal toxic shock syndrome?
The bacteria initially grow locally, then enter the bloodstream and cause systemic symptoms due to release of peptidoglycan fragments. The bacteria infect a wound and synthesize an exotoxin that stimulates cytokine activity and causes shock. The bacteria produce an abscess, the coagulase stimulates the growth of a gram-negative organism which enters the bloodstream, releases LPS, and causes shock. The bacteria produce an abscess with the help of the coagulase and release an enzyme that causes destruction of capillary endothelial cells, causing fluid to leak into the tissues and shock to ensue.
Question 57 - Single Best Answer
Virulence of Mycoplasma is not well understood. One factor that has been identified in Mycoplasma pneumoniae that contributes to its virulence is:
its ability to grow intracellularly in the ciliated epithelium. its extra thick peptidoglycan that prevents complement lysis. an adhesin called P1 found at the organisms tip. flagellar motility that allow it to invade the lungs. an IgA protease.
Question 58 - Single Best Answer
The fastest way to diagnose Legionnaire's disease is:
grow the organism on blood agar and look for alpha hemolysis. look for Legionella antigen in the urine. do a Gram stain of the sputum and look for the wall-less organisms. look for a rise in antibody titer to Legionella. do a blood culture and look for organisms that are sensitive to optichin.
Question 59 - Single Best Answer
The reservoir of Legionella is:
birds. mosquitoes. amoeba. humans only. army veterans.
Question 60 - Single Best Answer
Why is vancomycin resistance unusual from the perspective of general rules for antibiotic resistance?
It is a pump in the outer membrane of gram-negative bacteria. It is an enzyme that degrades the antibiotic, but it arose by a point mutation. It is caused by a set of resistant penicillin binding proteins (PBPs) that were inherited long ago and are established in S. aureus strains. It is a change in the target that is plasmid-encoded. The sensitive bacteria cease making the target altogether and thereby become resistant.
Question 61 - Single Best Answer
Pharyngitis caused by Neisseria gonorrhoeae in a child:
can lead to heart and kidney problems later on. is diagnosed by pseudomembrane formation. is always indicative of child sexual abuse. can be diagnosed by looking for beta hemolytic colonies on blood agar never occurs.
Question 62 - Single Best Answer
A Gram stain is not a good way to diagnose the cause of pharyngitis because: NOTE: WE ALLOWED TWO RIGHT ANSWERS FOR THIS QUESTION
viruses are too small to be seen in an ordinary light microscope. there are many normal flora in the pharynx. Mycoplasma don't stain with the Gram's procedure. acid fast bacteria will be missed. Corynebacteria are obligate intracellular pathogens.
Question 63 - Single Best Answer
Post-streptococcal rheumatic fever is caused by:
bacteria growing on the heart valves. autoimmunity to a bacterial product. intracellular growth in heart cells. immune complexes causing blockage of the coronary capillaries. a toxin that stops protein synthesis in heart muscle cells.
Question 64 - Single Best Answer
In unimmunized children suspected of having diphtheria it is imperative to give them:
the toxoid. the toxin. horse anti-diphtheria serum. antibiotics that work on intracellular bacteria. muscle relaxants.
Question 65 - Single Best Answer
Major criteria in diagnosing rheumatic fever caused by Group A streptococci (Jones criteria) include each of the following EXCEPT:
carditis. polyarthritis. elevated antibody titers to Streptolysin O (ASO) or DNAse B. erythema marginatum. Sydenham's chorea (spasms, incoordination, weakness).
Question 66 - Single Best Answer
Diphtheria toxin acts by:
hydrolyzing heart muscle cells. stimulating TNF in macrophages stimulating adenylate cyclase in fibroblasts. inhibiting protein synthesis in heart and kidney cells. causing swelling of the epiglottis.
Question 67 - Single Best Answer
A 2 month old infant recently brought to this country from Haiti was brought to the Emergency Room of a Miami hospital with a 10-day history of coughing spells. The illness had started with a runny nose and some coughing but had gotten progressively worse in the last week. The baby's coughing was so violent that he often became cyanotic and gasped for breath when the coughing subsided. In addition, he had several episodes of vomiting associated with his coughing. His pulse is rapid, and he is also breathing rapidly. His throat is somewhat red, but contains no pus, swelling, or gray, membranous structure.
swab the anterior nares and plate on Bordet-Gengou agar. swab the throat and plate on MacConkey agar. swab the throat and plate on tellurite medium. draw blood for a blood culture. look for antigen in the urine.
Question 68 - Single Best Answer
A 22-year-old University of Florida student was hospitalized in early December because of increasing shortness of breath and a cough with rust-colored sputum that had developed over a 2-day period. One week before hospitalization, he developed a cold characterized by a mild sore throat and nonproductive cough, malaise, and a generalized dull headache. The day before hospitalization at exactly 2:05 p.m. the patient experienced a severe shaking chill that lasted for two minutes. Physical examination revealed a temperature of 104, a pulse rate of 130/min, and respirations of 38/min. Each respiration was accompanied by an audible grunt. The chest was hypo-resonant to percussion (i.e., dull) and filled with inspiratory and expiratory wheezes. Fine crackling rales were heard on inspiration over the lower anterior chest just to the right of the sternum. A bacterium that produced alpha hemolysis on blood agar was isolated from the second of three blood cultures. To positively identify the bacterium, it should be further tested for
sensitivity to penicillin. sensitivity to bacitracin. sensitivity to optichin. production of coagulase. utilization of citrate.
Question 69 - Single Best Answer
A child from a commune that opposes vaccination is brought to the emergency room with a red, sore throat which was diagnosed as a Streptococcal pharyngitis. She is given penicillin but returns after a week much sicker than she was and having trouble breathing. She is hospitalized and given anti-toxin and other treatment as appropriate. In spite of all this she died. She likely died from:
being unable to breathe as a pseudomembrane cannot be removed.. being unable to breath as her epiglottis was so swollen and the antitoxin was not given in time heart valve failure due to bacteria growing on the valves. heart or kidney failure due to an exotoxin. low blood pressure that proceeded to shock due to an exotoxin.
Question 70 - Single Best Answer
A 67-year-old retired Army sergeant was transferred to Shands via helicopter from a community hospital in Ft. Pierce. He had a high fever, cough, and chest pain. He had presented to his local physician 3 days previously complaining of fever, headache, malaise, and vague respiratory symptoms. Over the next 3 days, his symptoms became progressively worse and he now had considerable difficulty breathing and was disoriented and lethargic. Chest x-rays indicated patchy alveolar infiltrates on both the right and left sides. His white cell count was 12,000 with 70% neutrophils. The "sputum" sample consisted of only thin, watery secretions. A gram stain of the sputum showed many neutrophils, no epithelial cells, and a very few poorly staining gram-negative bacteria. Multiple routine cultures of blood and sputum were negative. His wife indicated that he is a very heavy drinker and that he has smoked two packs of cigarettes a day since he was 14 years old. A test of his urine was diagnostic. What is the best course of action in this case?
This patient should be immediately placed in respiratory isolation as he is a threat to others. All of this patient's contacts should receive prophylactic antibiotics. This patient should be given amantidine. All of this patient's contacts should be vaccinated. The patient should receive antibiotics.
Question 71 - Single Best Answer
In this image, the + and - indicate the test and negative control reagents, respectively, in the Phadebact test kit. A patient with pharyngitis whose sample was tested in areas 1 and 2 should be treated how?
Provided with analgesics and sent home. A throat culture should be taken. Started with a course of polymyxin Started with a course of isoniazid (INH) and ethambutol A blood culture should be taken.
Question 72 - Single Best Answer
Based on your experience with the laboratory exercise and assuming that both citrate tubes shown in the figure were inoculated with bacteria, the tube at the bottom is consistent with which of the following?
atypical "walking" pneumonia thin secretions in a elderly man who smokes and drinks rust colored sputum following a single shaking chill pseudomembrane formation in the pharynx current jelly-like sputum
Question 73 - Single Best Answer
The bacteria in the Gram stain shown in this image are most likely to be associated with:
rust colored sputum and a single shaking chill. severe coughing in a child, cyanosis, vomiting, and an inspiratory whoop. normal mouth flora. atypical "walking" pneumonia. watery secretions in an elderly man who drinks and smokes.
Question 74 - Single Best Answer
The bacteria streaked on this blood agar plate with a bacitracin disk are showing which of the following characteristics?
beta-hemolysis and bacitracin resistance alpha-hemolysis and bacitracin resistance beta-hemolysis and bacitracin sensitivity beta-hemolysis and bacitracin sensitivity gamma-hemolysis and bacitracin sensitivity
Question 75 - Single Best Answer
The liquid on this slide is hydrogen peroxide. The bacteria placed in the right-most drop are most likely to be further identified with which of the following tests?
bacitracin sensitivity optichin sensitivity Phadebact test coagulase test anti-DNase B