>>>Part 5
50.1 The most important mechanism by which tetracycline antibiotics exert antimicrobial action is:
A. They chelate Ca2+ ions and alter permeability of bacterial cell membrane
B. They bind to 30S ribosomes and inhibit bacterial protein synthesis
C. They bind to 50S ribosomes and interfere with translocation of the growing peptide
chain in the bacteria
D. They interfere with DNA mediated RNA synthesis in bacteria
50.2 Select the most potent tetracycline antibiotic:
A. Demeclocycline
B. Oxytetracycline
C. Minocycline
D. Doxycycline
50.3 The following tetracycline has the potential to cause vestibular toxicity:
A. Minocycline
B. Demeclocycline
C. Doxycycline
D. Tetracycline
50.4 Mammalian cells are not inhibited by low concentrations
of tetracyclines that inhibit sensitive microorganisms because:
A. Host cells lack active transport mechanism for tetracyclines
B. Host cells actively pump out tetracyclines
C. Protein synthesizing apparatus of host cells has low affinity for tetracyclines
D. Both ‘A’ and ‘C’ are correct
50.5 Bacteria develop tetracycline resistance by the following mechanisms except:
A. Losing tetracycline concentrating mechanisms
B. Elaborating tetracycline inactivating enzyme
C. Synthesizing a ‘protection protein’ which
interferes with binding of tetracycline to the target site
D. Actively pumping out tetracycline that has entered the cell
50.6 An 8-year-old child presented with brownish discoloured
and deformed anterior teeth. History of having
received an antibiotic about 4 years earlier was
obtained. Which antibiotic could be responsible for the condition:
A. Chloramphenicol
B. Tetracycline
C. Erythromycin
D. Gentamicin
50.7 Choose the correct statement about tetracyclines:
A. Being broad spectrum antibioics they are dependable for empirical treatment of lifethreatening infections
B. Currently, they are not the first choice antibiotic for any specific infection
C. They reduce stool volume and duration of diarrhoea in cholera
D. The are preferred for treatment of anaerobic bacterial infections
50.8 The drug of choice for atypical pneumonia due to
Mycoplasma pneumoniae is:
A. Doxycycline
B. Ciprofloxacin
C. Ceftriaxone
D. Gentamicin
50.9 The most suitable tetracycline for use in a patient with impaired renal function is:
A. Tetracycline
B. Demeclocycline
C. Oxytetracycline
D. Doxycycline
50.10 Compared to older tetracyclines, doxycycline produces a
lower incidence of superinfection diarrhoea because:
A. It is completely absorbed in the small intestines so that drug concentration in the
colonic contents is low
B. It is inactivated by the gut microflora
C. It is not active against the microbes of the normal gut flora
D. It is a potent tetracycline and inhibits the superinfection causing microbes as well
50.11 Select the antibiotic(s) that can be used to treat
nonspecific urethritis due to Chlamydia trachomatis:
A. Azithromycin
B. Doxycycline
C. Clindamycin
D. Both 'A' and 'B' are correct
50.12 Tetracyclines are still the first choice drugs for the following disease:
A. Granuloma inguinale
B. Chancroid
C. Syphilis
D. Gonorrhoea in patients allergic to penicillin
50.13 Tetracyclines are active against the following gram
negative bacteria:
A. Salmonella typhi
B. Pseudomonas aeruginosa
C. Yersinia pestis
D. All of the above
50.14 A patient treated with capsule oxytetracycline 500
mg 6 hourly complained of epigastric pain. Which of
the following measures will you recommend to
counteract the side effect:
A. Take the capsules with milk
B. Take the capsules with meals
C. Take aluminium hydroxide gel 15 minutes before the capsules
D. None of the above measures is suitable.
Change the antibiotic if pain is distressing
50.15 A child presented with polyuria, weakness and fever.
On the basis of investigations he was labelled to be
suffering from Fancony syndrome. A history of taking
some old left over antibiotic capsules was obtained.
What could have been the antibiotic:
A. Tetracycline
B. Chloramphenicol
C. Ampicillin
D. Cephalexin
50.16 Chloramphenicol inhibits bacterial protein synthesis by:
A. Binding to 30S ribosome and inhibiting attachment of aminoacyl tRNA
B. Binding to 50S ribosome and preventing peptide bond formation
C. Binding to 50S ribosome and blocking translocation of peptide chain
D. Binding to both 30S and 50S ribosome and inducing misreading of mRNA code
50.17 Chloramphenicol is more active than tetracyclines against:
A. Bateroides fragilis
B. Treponema pallidum
C. Streptococci
D. Staphylococci
50.18 The following antibiotic penetrates blood-CSF barrier the best:
A. Erythromycin
B. Gentamicin
C. Tetracycline
D. Chloramphenicol
50.19 The most important mechanism by which gram negative
bacilli acquire chloramphenicol resistance is:
A. Decreased permeability into the bacterial cell
B. Acquisition of a plasmid encoded for chloramphenicol acetyl transferase
C. Lowered affinity of the bacterial ribosome for chloramphenicol
D. Switching over from ribosomal to mitochondrial protein synthesis
50.20 A premature neonate suffered respiratory distress
and was given an antibiotic 100 mg/kg/day orally.
Over the next two days his condition worsened, he
become dull, stopped feeding, developed abdominal
distention and an ashen gray appearance. Which is
the most likely antibiotic given to him:
A. Ampicillin
B. Chloramphenicol
C. Erythromycin
D. Ciprofloxacin
50.21 Combination therapy with two (or more) antimicrobials
is superior to monotherapy with any single effective
drug in case of the following diseases except:
A. Typhoid fever
B. Leprosy
C. AIDS
D. Subacute bacterial endocarditis
50.22 What is true of drug therapy of typhoid fever:
A. Combination of chloramphenicol with ciprofloxacin is superior to either drug alone
B. Ceftriaxone (i.v.) is one of the fastest acting and most dependable treatment
C. Prolonged treatment with chloramphenicol eradicates typhoid carrier state
D. All of the above are correct
50.23 What is the most important reason for the restricted use of systemic chloramphenicol:
A. Emergence of chloramphenicol resistance
B. Its potential to cause bone marrow depression
C. Its potential to cause superinfections
D. Its potential to inhibit the metabolism of many drugs
50.24 The primary reason why chloramphenicol is not
being used as the first line drug for typhoid fever in most areas is:
A. Toxic potential of chloramphenicol
B. Delayed defervescence with chloramphenicol
C. Delayed bacteriological cure with chloramphenicol
D. Spread of chloramphenicol resistance among S. typhi
50.25 Empiric therapy with chloramphenicol is valid in the following conditions except:
A. Urinary tract infection
B. Pelvic abscess
C. Endophthalmitis
D. Meningitis in a 4-year-old child
Ans:
50.1 B 50.2 C 50.3 A 50.4D 50.5 B 50.6 B 50.7 C 50.8 A 50.9D 50.10 A 50.11D 50.12 A 50.13 C 50.14D 50.15 A 50.16 B 50.17 A 50.18D 50.19 B 50.20 B 50.21 A 50.22 B 50.23 B 50.24D 50.25 A
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