Abstract
Little is known about mechanisms involved in high-level expression of plasmid-associated ampC genes. The sequence for blaMIR-1 has been elucidated, and the gene is not inducible. Although the sequence for the promoter (prA) that drives expression of Enterobacter cloacae chromosomal ampC is present upstream of blaMIR-1, high-level expression from bla MIR-1 is directed from a hybrid promoter (prB) located further upstream of prA. The purpose of this study was to determine the influence of each promoter on blaMIR-1 expression and β-lactam resistance. RNA expression by deletion clones with both promoters was measured and compared to that by clones in which -35 and/or -10 elements of prA and/or prB were altered. Primer extension revealed two start sites for blaMIR-1 transcription. Expression of blaMIR-1 in clones with both promoters was 171-fold higher than that in clones carrying only prA. In addition, bla MIR-1 expression from prA increased 11-fold in the presence of the prB -10 element compared to expression driven from prA alone. Ceftazidime and cefotaxime MICs increased 42- and 64-fold, respectively, for the clone expressing blaMIR-1 from both promoters compared to expression from prA alone. The upstream promoter prB of blaMIR-1 is solely responsible for high-level expression required for cefotaxime and ceftazidime resistance. These data suggest that resistance to extended-spectrum cephalosporins mediated by noninducible plasmid-associated ampC genes requires the formation of novel promoter elements that are capable of increasing ampC expression.
| Original language | English |
|---|---|
| Pages (from-to) | 4177-4182 |
| Number of pages | 6 |
| Journal | Antimicrobial Agents and Chemotherapy |
| Volume | 48 |
| Issue number | 11 |
| DOIs | |
| State | Published - Nov 2004 |
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All Science Journal Classification (ASJC) codes
- Pharmacology (medical)
Cite this
Promoter sequences necessary for high-level expression of the plasmid-associated ampC β-lactamase gene blaMIR-1 . / Reisbig, Mark; Hanson, Nancy D.
In: Antimicrobial Agents and Chemotherapy, Vol. 48, No. 11, 11.2004, p. 4177-4182.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Promoter sequences necessary for high-level expression of the plasmid-associated ampC β-lactamase gene blaMIR-1
AU - Reisbig, Mark
AU - Hanson, Nancy D.
PY - 2004/11
Y1 - 2004/11
N2 - Little is known about mechanisms involved in high-level expression of plasmid-associated ampC genes. The sequence for blaMIR-1 has been elucidated, and the gene is not inducible. Although the sequence for the promoter (prA) that drives expression of Enterobacter cloacae chromosomal ampC is present upstream of blaMIR-1, high-level expression from bla MIR-1 is directed from a hybrid promoter (prB) located further upstream of prA. The purpose of this study was to determine the influence of each promoter on blaMIR-1 expression and β-lactam resistance. RNA expression by deletion clones with both promoters was measured and compared to that by clones in which -35 and/or -10 elements of prA and/or prB were altered. Primer extension revealed two start sites for blaMIR-1 transcription. Expression of blaMIR-1 in clones with both promoters was 171-fold higher than that in clones carrying only prA. In addition, bla MIR-1 expression from prA increased 11-fold in the presence of the prB -10 element compared to expression driven from prA alone. Ceftazidime and cefotaxime MICs increased 42- and 64-fold, respectively, for the clone expressing blaMIR-1 from both promoters compared to expression from prA alone. The upstream promoter prB of blaMIR-1 is solely responsible for high-level expression required for cefotaxime and ceftazidime resistance. These data suggest that resistance to extended-spectrum cephalosporins mediated by noninducible plasmid-associated ampC genes requires the formation of novel promoter elements that are capable of increasing ampC expression.
AB - Little is known about mechanisms involved in high-level expression of plasmid-associated ampC genes. The sequence for blaMIR-1 has been elucidated, and the gene is not inducible. Although the sequence for the promoter (prA) that drives expression of Enterobacter cloacae chromosomal ampC is present upstream of blaMIR-1, high-level expression from bla MIR-1 is directed from a hybrid promoter (prB) located further upstream of prA. The purpose of this study was to determine the influence of each promoter on blaMIR-1 expression and β-lactam resistance. RNA expression by deletion clones with both promoters was measured and compared to that by clones in which -35 and/or -10 elements of prA and/or prB were altered. Primer extension revealed two start sites for blaMIR-1 transcription. Expression of blaMIR-1 in clones with both promoters was 171-fold higher than that in clones carrying only prA. In addition, bla MIR-1 expression from prA increased 11-fold in the presence of the prB -10 element compared to expression driven from prA alone. Ceftazidime and cefotaxime MICs increased 42- and 64-fold, respectively, for the clone expressing blaMIR-1 from both promoters compared to expression from prA alone. The upstream promoter prB of blaMIR-1 is solely responsible for high-level expression required for cefotaxime and ceftazidime resistance. These data suggest that resistance to extended-spectrum cephalosporins mediated by noninducible plasmid-associated ampC genes requires the formation of novel promoter elements that are capable of increasing ampC expression.
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U2 - 10.1128/AAC.48.11.4177-4182.2004
DO - 10.1128/AAC.48.11.4177-4182.2004
M3 - Article
VL - 48
SP - 4177
EP - 4182
JO - Antimicrobial Agents and Chemotherapy
JF - Antimicrobial Agents and Chemotherapy
SN - 0066-4804
IS - 11
ER -