The Quizzes about Physiology and Molecular Microbiology – Part 1 (20 test)

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The Quizzes about Physiology and Molecular Microbiology – Part 1 (20 test)
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Select the ONE answer that is BEST in each case.

A 28-year-old female with folliculitis is not responsive to a 10-day treatment course with penicillin. An enzyme produced by the etiologic agent is most likely responsible for this treatment failure. At which site on the molecule shown does this enzyme act to destroy penicillin?

The structural integrity of the β-lactam ring in penicillins is essential for their antimicrobial activity. Many resistant strains of staphylococci produce a β-lactamase (penicillinase) that cleaves the β-lactam ring of penicillin at the carbon-nitrogen bond (4 in diagram). Other organisms, including coliform bacteria and Pseudomonas, produce cephalosporinases, metallo-β- lactamases, and carbapenamases that cleave the β-lactam rings of cephalosporins and/or carbapenems, as well as penicillins, at the same site. Penicillin amidase inactivates penicillin by disrupting the bond between the radical and nitrogen in the free amino group (1 in diagram). Bonds 2, 3, and 5 are not commonly broken by bacterial enzymes.

 

See all quizzes of  the Physiology and Molecular Microbiology at here:

Part 1 | Part 2 | Part 3 |

1. A 28-year-old female with folliculitis is not responsive to a 10-day treatment course with penicillin. An enzyme produced by the etiologic agent is most likely responsible for this treatment failure. At which site on the molecule shown does this enzyme act to destroy penicillin?

a. 1
b. 2
c. 3
d. 4
e. 5

2. A 35-year-old male was treated with an aminoglycoside for an infection with a gram-negative rod. Which of the following bacterial processes is involved in transport of this antibiotic into the cell?
a. Facilitated diffusion
b. Fermentation
c. Group translocation
d. Oxidative phosphorylation
e. Transpeptidation
3. A 36-year-old male developed a painful purulent urethral discharge following a 2-week vacation to Thailand. A Gram stain reveals gramnegative diplococci. Iron, which it obtains through surface receptors, is essential for the expression of the microorganism’s virulence factors. From which of the following molecules does it obtain iron?
a. Ferric oxide
b. Lactoferrin
c. Lipopolysaccharide (LPS)
d. Pyocyanin
e. Siderophores
4. A female medical student is admitted to the emergency department with symptoms of severe urinary tract infection (UTI). The Escherichia coli strain isolated from urine produced extended-spectrum β-lactamase. In which anatomic area of the cell would this enzyme be located?

a. A
b. B
c. C
d. D
e. E

A 52-year-old male develops abscesses following surgery to repair an abdominal gunshot wound. Gram stain of the foul-smelling exudate from his abscess reveals numerous polymorphonuclear leukocytes (PMNs or neutrophils) and several gram-negative rods that did not grow on blood plates in the presence of O2. Metabolism of O2 results in toxic reactive oxygen species. Which of the following enzymes inactivates superoxide free radicals
a. ATPase
b. Catalase
c. Permease
d. Peroxidase
e. Superoxide dismutase
A 52-year-old male develops abscesses following surgery to repair an abdominal gunshot wound. Gram stain of the foul-smelling exudate from his abscess reveals numerous polymorphonuclear leukocytes (PMNs or neutrophils) and several gram-negative rods that did not grow on blood plates in the presence of O2. Metabolism of O2 results in toxic reactive oxygen species. Which of the following antibiotics would be the best choice for treating this patient’s infection?
a. Ampicillin
b. Chloramphenicol
c. Ciprofloxacin
d. Gentamicin
e. Metronidazole
7. A teenaged boy suffered a foot laceration while swimming in a polluted water area in a river. He did not seek medical treatment, and the wound developed a foul-smelling exudate. One of the bacteria isolated from the abscess exudate was missing superoxide dismutase, catalase, and a peroxidase. Which of the following statements best describes this microorganism?
a. It is a capnophile
b. It is a facultative anaerobe
c. It is a microaerophile
d. It is an anaerobe
e. It is an obligate aerobe
A 20-year-old pregnant female patient presents to the emergency room with a 4-day history of fever, chills, and myalgia. Two days prior to this, she had noted painful genital lesions that had begun as vesicles. Pelvic examination revealed extensive vesicular and ulcerative lesions on the left
labia minora and majora with marked edema, and inguinal lymphadenopathy. Which of the microorganisms causing genital ulcers can be demonstrated by dark field microscopy?
a. Chlamydia trachomatis LGV serovars
b. Haemophilus ducreyi
c. Herpes simplex virus type 2
d. Klebsiella granulomatis
e. Treponema pallidum
A 20-year-old pregnant female patient presents to the emergency room with a 4-day history of fever, chills, and myalgia. Two days prior to this, she had noted painful genital lesions that had begun as vesicles. Pelvic examination revealed extensive vesicular and ulcerative lesions on the left labia minora and majora with marked edema, and inguinal lymphadenopathy. Which of th following tests would prove that the patient is infectious for herpes simplex virus (HSV) type 2?
a. Culture
b. Detection of HSV2-specific IgM
c. Direct immunofluorescent assay
d. Nucleic acid amplification testing
e. Tzanck smear
10. Gram-negative diplococci were demonstrated in a Gram stain of urethral drainage from an 18 year-old male who presented with symptoms of urethritis. Continuous passage of this strain on laboratory medium resulted in the reversion of a fimbriated to a nonfimbriated strain. Which of the following is the most likely implication of this phenomenon?

a. A negative capsule strain
b. Death of the organism
c. Inability to colonize the mucosal epithelium
d. Loss of serologic specificity
e. Reversion to a gram-positive stain

11. Twenty-eight hours after eating undercooked chicken, a 50-year-old farmer presents to the emergency room with abdominal pain, cramping, bloody diarrhea, and nausea. An isolate from the stool is biochemically identified as Salmonella enterica; however, the isolate cannot be serotyped. Which of the following has this organism lost?
a. Capsule
b. Flagella
c. Mannose receptor
d. Pili
e. O-specific polysaccharide
12. A 2-year-old infant is diagnosed with meningitis. A lumbar puncture reveals numerous neutrophils and gram-positive cocci in pairs that appear encapsulated. She is admitted to the hospital and started on intravenous (IV) β-lactams. Which of the following targets would most likely play a role in the development of resistance to this antibiotic in the most likely etiologic agent of this child’s meningitis?
a. Bactoprenol
b. DNA gyrase
c. Penicillin-binding protein
d. Reverse transcriptase
e. RNA polymerase
13. A cattle farmer develops necrotic lesions on his arms and face following a traumatic encounter with a bull. Selective inhibition of synthesis of dipicolinic acid by the etiologic agent of the infection would most likely inhibit the formation of the infective structure. Which of the following would be inhibited?

a. Bacterial spore formation
b. Bacterial vegetative cells
c. Fungal arthrospores
d. Fungal microconidia
e. Mycobacterial vegetative cells

A 30-year-old male presents to the emergency room with high fever and malaise, which he reports that it began 4 days ago and got progressively worse each day. He appears underweight and very ill. Physical examination reveals needle marks in both antecubital fossae. Upon listening for heart sounds, you hear a distinctive systolic heart murmur. You order blood cultures and make a presumptive diagnosis of acute bacterial endocarditis. Following is the growth curve of the organism growing in a nutrient medium at 35°C with both O2 and added CO2 present. In which of the following growth phases would the organism most likely be resistant to β-lactam antibiotics?
a. Lag phase
b. Log phase
c. Stationary phase
d. Death phase
A 30-year-old male presents to the emergency room with high fever and malaise, which he reports that it began 4 days ago and got progressively worse each day. He appears underweight and very ill. Physical examination reveals needle marks in both antecubital fossae. Upon listening for heart sounds, you hear a distinctive systolic heart murmur. You order blood cultures and make a presumptive diagnosis of acute bacterial endocarditis. Following is the growth curve of the organism growing in a nutrient medium at 35°C with both O2 and added CO2 present. On which of the following growth phases would treatment with gentamicin have a maximal effect?
a. Lag phase
b. Log phase
c. Stationary phase
d. Death phase
16. An outbreak of diarrhea is thought to be related to a group of vendors who were selling hot dogs at the county fair. Stool cultures are positive for Shigella in almost all individuals who ate the hot dogs. Growth of the isolated colonies in nutrient liquid medium without the transfer to fresh medium will eventually induce the death phase of the organism. Which of the following is a limiting factor in microbial growth under laboratory conditions?
a. Accumulation of oxygen-free radicals
b. Accumulation of peroxide
c. Accumulation of toxic products in the growth medium
d. Loss of superoxide dismutase
e. Oxygen
17. A 62-year-old woman with diagnosed type 2 diabetes lived alone and did essentially nothing to manage her illness, including disregarding her physician’s instructions. She was taken to her local emergency room (ER) with severe, multiple infected foot lesions, which yielded a variety of opportunistic microbes with a mixture of antibiotic susceptibilities. The physician decided to treat with systemic and topical antimicrobials. Which of the following antimicrobial agents must only be used topically?
a. Bacitracin
b. Gentamicin
c. Itraconazole
d. Penicillin
e. Vancomycin
18. A 42-year-old alcoholic man presents with fever, chills, cough, and chest x-ray suggestive of pneumonia. The Gram-stained smear of sputum shows many PMNs and gram-positive cocci in pairs and chains. Which of the following is the correct order of the procedural steps when performing the Gram stain?
a. Fixation, crystal violet, alcohol/acetone decolorization, safranin
b. Fixation, crystal violet, iodine treatment, alcohol/acetone decolorization, safranin
c. Fixation, crystal violet, iodine treatment, safranin
d. Fixation, crystal violet, safranin
e. Fixation, safranin, iodine treatment, alcohol/acetone decolorization, crystal violet
19. A 78-year-old man presents to the local emergency department with a severe headache and stiff neck. The cerebrospinal fluid (CSF) specimen is cloudy. Analysis reveals 400 white blood cells per cubic millimeter (95% PMNs), a protein concentration of 75 mg/dL, and a glucose concentration of 20 mg/dL. While in the ER, a resident does a Gram stain of the CSF but mistakenly forgets the iodine treatment step. If the meningitis is caused by Streptococcus pneumoniae, how will the bacteria seen on the resident’s slide appear?
a. All the cells will be blue
b. All the cells will be decolorized
c. All the cells will be purple
d. All the cells will be red
e. All the cells will lyse; thus, no Gram stain results will be obtained
f. Half of the cells will be red and the other half will be blue
20. A 28-year-old female just returned from a 1-week cruise with stops along the coast of Mexico. Forty-eight hours after her return she is reported to have headache, fever, abdominal cramps, and constipation. Over the next 5 days, her fever increases with continued complaints of myalgias, malaise, and anorexia. A blood culture is positive for S. enterica ser. Typhi. Her condition improves with a treatment course of a ciprofloxacin. Which of the following is the function of porins that would prevent the effective use of this antimicrobial?
a. Hydrolysis of hydrophilic antimicrobials
b. Metabolism of phosphorylated intermediates
c. Serologic stabilization of the O antigen
d. Inactivation of hydrophobic antimicrobials
e. Transfer of molecules through the outer membrane

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