Delights Test Banks 1
, Delights Test Banks 2
SECTION 1: ESBL Mechanisms & Molecular Basis
Questions 1–30 (MCQs)
1. Which of the following ESBLs has emerged as the most globally
prevalent variant in recent years?
A) TEM-1
B) SHV-2
C) CTX-M-15
D) OXA-48
Rationale: CTX-M-15 has surpassed TEM and SHV variants in prevalence
globally, especially in E. coli. Its success is tied to rapid plasmid-mediated
transmission and association with ST131 clones. OXA-48 is a carbapenemase,
not an ESBL.
2. The gene bla<sub>CTX-M</sub> is most commonly found on which
type of mobile genetic element?
A) Bacteriophage
B) Plasmid
, Delights Test Banks 3
C) Transposon
D) Integrative conjugative element (ICE)
Rationale: bla<sub>CTX-M</sub> is frequently carried on conjugative
plasmids, facilitating horizontal transfer between E. coli, Klebsiella, and other
Enterobacterales. This contributes to its pandemic spread.
3. The ESBL activity of CTX-M enzymes primarily hydrolyzes which class
of antibiotics?
A) Carbapenems
B) Extended-spectrum cephalosporins
C) Aminoglycosides
D) Glycopeptides
Rationale: CTX-M enzymes hydrolyze cefotaxime, ceftriaxone, and other third-
generation cephalosporins. They do not act on carbapenems or non-beta-
lactams.
4. Which mechanism contributes most directly to the rapid horizontal
spread of bla genes encoding ESBLs?
A) Spontaneous mutation
B) Conjugative plasmid transfer
, Delights Test Banks 4
C) Transcriptional activation
D) Ribosomal frameshift
Rationale: Plasmid-mediated conjugation is the key driver of horizontal gene
transfer among Enterobacterales, allowing the spread of resistance genes like
bla<sub>TEM</sub>, bla<sub>SHV</sub>, and bla<sub>CTX-M</sub>.
5. Which of the following enzymes is not classified as an ESBL?
A) SHV-2
B) CTX-M-15
C) NDM-1
D) TEM-52
Rationale: NDM-1 is a metallo-beta-lactamase that confers resistance to
carbapenems, not a classical ESBL. SHV-2, CTX-M-15, and TEM-52 are all
ESBLs.
6. Which ESBL variant is primarily associated with the E. coli ST131
clone?
A) SHV-5
B) TEM-3
, Delights Test Banks 2
SECTION 1: ESBL Mechanisms & Molecular Basis
Questions 1–30 (MCQs)
1. Which of the following ESBLs has emerged as the most globally
prevalent variant in recent years?
A) TEM-1
B) SHV-2
C) CTX-M-15
D) OXA-48
Rationale: CTX-M-15 has surpassed TEM and SHV variants in prevalence
globally, especially in E. coli. Its success is tied to rapid plasmid-mediated
transmission and association with ST131 clones. OXA-48 is a carbapenemase,
not an ESBL.
2. The gene bla<sub>CTX-M</sub> is most commonly found on which
type of mobile genetic element?
A) Bacteriophage
B) Plasmid
, Delights Test Banks 3
C) Transposon
D) Integrative conjugative element (ICE)
Rationale: bla<sub>CTX-M</sub> is frequently carried on conjugative
plasmids, facilitating horizontal transfer between E. coli, Klebsiella, and other
Enterobacterales. This contributes to its pandemic spread.
3. The ESBL activity of CTX-M enzymes primarily hydrolyzes which class
of antibiotics?
A) Carbapenems
B) Extended-spectrum cephalosporins
C) Aminoglycosides
D) Glycopeptides
Rationale: CTX-M enzymes hydrolyze cefotaxime, ceftriaxone, and other third-
generation cephalosporins. They do not act on carbapenems or non-beta-
lactams.
4. Which mechanism contributes most directly to the rapid horizontal
spread of bla genes encoding ESBLs?
A) Spontaneous mutation
B) Conjugative plasmid transfer
, Delights Test Banks 4
C) Transcriptional activation
D) Ribosomal frameshift
Rationale: Plasmid-mediated conjugation is the key driver of horizontal gene
transfer among Enterobacterales, allowing the spread of resistance genes like
bla<sub>TEM</sub>, bla<sub>SHV</sub>, and bla<sub>CTX-M</sub>.
5. Which of the following enzymes is not classified as an ESBL?
A) SHV-2
B) CTX-M-15
C) NDM-1
D) TEM-52
Rationale: NDM-1 is a metallo-beta-lactamase that confers resistance to
carbapenems, not a classical ESBL. SHV-2, CTX-M-15, and TEM-52 are all
ESBLs.
6. Which ESBL variant is primarily associated with the E. coli ST131
clone?
A) SHV-5
B) TEM-3
