Genetic Control of  -Lactamase Production in Enterobacter cloacae

Korfmann, Gisela; Wiedemann, B.

doi:10.1093/clinids/10.4.793

Cited by 44 publications

(28 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The work described here has identified a new target for regulation by a two-component system, ␤-lactamase expression. Previously characterized regulatory systems for ␤-lactamase expression include those described for the class C cephalosporinases (13,17,31) and for some class A enzymes (7,15,46). The induction system of the class C enzymes involves repressor-activator protein AmpR with accessory proteins AmpD, AmpE, and AmpG (10,(16)(17)(18)(19)(20)(21).…”

Section: Discussionmentioning

confidence: 99%

Expression of the AsbA1, OXA-12, and AsbM1 beta-lactamases in Aeromonas jandaei AER 14 is coordinated by a two-component regulon

Alksne

Rasmussen

1997

J Bacteriol

View full text Add to dashboard Cite

Aeromonas jandaei AER 14 (formerly Aeromonas sobria AER 14) expresses three inducible ␤-lactamases, AsbA1, OXA-12 (AsbB1), and AsbM1. Mutant strains that constitutively overexpress all three enzymes simultaneously, suggesting that they share a common regulatory pathway, have been isolated. Detectable expression of the cloned genes for AsbA1 and OXA-12 in some Escherichia coli K-12 laboratory strains is achieved only in the presence of a blp mutation. These mutations map to the cre operon at 0 min, which encodes a classical two-component regulatory system of unknown function. Two regulatory elements from A. jandaei which permit high-level constitutive expression of OXA-12 in E. coli were cloned. Both loci encode proteins with characteristics of response regulator proteins of two-component regulatory systems. One of these loci, designated blrA, bestowed constitutive expression of all three ␤-lactamases in A. jandaei AER 14 when present on a multicopy plasmid, confirming its role in the regulatory pathway of ␤-lactamase production in this organism.Aeromonas jandaei AER 14 (formerly Aeromonas sobria AER 14 [5]) expresses three chromosomally encoded, inducible ␤-lactamases: a cephalosporin-hydrolyzing enzyme, AsbA1; a cloxacillin-hydrolyzing enzyme, OXA-12 (AsbB1); and a carbapenem-hydrolyzing metalloenzyme, AsbM1 (12,29,45). The three enzymes each exhibit ␤-lactam hydrolysis selectivity with minimal substrate overlap among them. Selection for resistance to the noninducing ␤-lactam cefuroxime identified a mutation that results in constitutive expression of all three enzymes, indicating that they are coordinately regulated (12,29,45). Inducible expression of the chromosomally encoded class C ␤-lactamases of gram-negative bacteria is regulated by a highly conserved and well-described AmpR repression system (15-21); however, little is known about the regulation of other classes of chromosomally encoded ␤-lactamases such as the carbapenem-hydrolyzing metalloenzymes. Mechanisms for the coordinate regulation of more than one inducible ␤-lactamase have not been previously described. Sequence analysis of the promoter regions of the two cloned ␤-lactamase genes asbA1 and asbB1, encoding AsbA1 and OXA-12, respectively, reveals sequence similarities that may be involved in coregulation; however, no ampR-like regulatory gene has been identified (29).In some laboratory strains of Escherichia coli the genes encoding AsbA1 and OXA-12 are expressed at high levels only if a blp mutation, mapping to the cre operon, is present (reference 29 and unpublished data). The cre operon encodes a classical two-component regulatory system of unidentified function (1, 40; for reviews, see references 38 and 39). While the cre sensor kinase component, CreC, has been demonstrated to cross regulate expression of the Pho regulatory machinery in a phoR background, the signals and targets of the Cre system have not been identified. The finding that components of the cre regulatory system affect the expression of the ␤-lactamases in E. coli prompted a se...

show abstract

Section: Discussionmentioning

confidence: 99%

Expression of the AsbA1, OXA-12, and AsbM1 beta-lactamases in Aeromonas jandaei AER 14 is coordinated by a two-component regulon

Alksne

Rasmussen

1997

J Bacteriol

View full text Add to dashboard Cite

show abstract

“…Therefore, ampD regions cloned from other organisms can be characterized by transforming them into this E. coli SN0302(pBP131) construct. The cloning strategy for ampD used in this study has been described previously (16,17). It requires the presence of the adjacent nadC gene, which is used as a selective marker in E. coli JRG582 recipients (the latter host lacks the nadC ampD ampE region) since ampD itself cannot be directly selected for.…”

Section: Methodsmentioning

confidence: 99%

Altered phenotypes associated with ampD mutations in Enterobacter cloacae

Korfmann

Sanders

Moland

1991

Antimicrob Agents Chemother

View full text Add to dashboard Cite

A study was done to determine the genetic locus responsible for altered expression of AmnpC 3-lactamase in Enterobacter cloacae 1194E and several mutants derived from E. cloacae 029. These phenotypes were defined by units of enzyme activity found in sonic extracts of cells before and after induction with cefoxitin and included (units uninduced/units induced) the wild-type (7/219), high-level constitutive (10,911/10,862), temperaturesensitive (at 30°C 82/706 and at 42C 5,031/6,020), and hyperinducible (19/1,688) phenotypes. When the ampD region of each E. cloacae strain was cloned and introduced into an ampD mutant Escherichia coli strain, the altered phenotypes were found to reside within this locus. Furthermore, transformants containing wid-type ampD were poorly inducible at 42C while those with high-level constitutive or hyperinducible ampD were unaffected by temperature. Since the source of ampD was the only variable in these E. coli transformants, these results suggested that ampD encodes a protein that is involved in sensing the inducer. To test this possibility, the responses to different inducers of E. coli transformants containing various ampD regions were assessed. In the presence of wild-type ampD, transformants responded equally to cefoxitin and cefotetan, regardless of temperature. In the presence of temperature-sensitive ampD, induction by cefotetan was similar to that by cefoxitin at 30°C but greater than that by cefoxitin at 42°C. These results suggest that ampD encodes a protein involved in induction of AmpC P-lactgmase in E. cloacae.

show abstract

“…In many of these species, expression of the enzyme is inducible by various 1-lactam antibiotics (29,32,34). This inducibility can be altered by mutation resulting in elevated production of P-lactamase and resistance to many of the new ,B-lactam antibiotics (9,15,16,21,26,31). To date the genetic apparatus responsible for both the inducible and the high-level expression of class I P-lactamase in Enterobacter cloacae and Citrobacter freundii has not been fully delineated.…”

mentioning

confidence: 99%

“…From these studies, two regulatory genes affecting expression of ampC, the structural gene, have been identified. ampR, which is adjacent to ampC, appears to encode a DNA-binding protein that serves as the activator of ampC (13,16,(20)(21)(22). A second regulatory gene, ampD, not closely linked to the ampRampC region, is responsible for low-level expression of ampC in uninduced E. cloacae wild-type strains.…”

mentioning

confidence: 99%

See 1 more Smart Citation

ampG is essential for high-level expression of AmpC beta-lactamase in Enterobacter cloacae

Korfmann

Sanders

1989

Antimicrob Agents Chemother

115

120

View full text Add to dashboard Cite

Mutants of Enterobacter cloacae 55 were studied to delineate more completely the genetics of inducible expression of AmpC beta-lactamase. E. cloacae 55M-L, derived by mutagenesis from a mutant with high-level cefotaxime resistance (MIC, greater than 64 micrograms/ml), E. cloacae 55M, demonstrated a novel phenotype by producing only low levels of AmpC constitutively. Neither the parental phenotype of E. cloacae 55M nor the wild-type phenotype of E. cloacae 55 could be restored in E. cloacae 55M-L by the introduction of functional ampR, ampC, or ampD genes. Cloning each of these genes from E. cloacae 55M-L confirmed the same genotype for this mutant as for its parental strain. Mutation of E. cloacae 55M-L to the E. cloacae 55M phenotype was found to occur spontaneously at a frequency of 10(-8). All such revertants demonstrated an inducible wild-type phenotype after introduction of a functional ampD. These results suggested that the E. cloacae 55M-L phenotype was due to a mutation in an as yet unrecognized gene, designated ampG. Verification of this gene was obtained by the restoration of the E. cloacae 55M phenotype in E. cloacae 55M-L by introduction of a cloned 2.9-kilobase BamHI fragment from the E. cloacae 55 chromosome. Transformation of both ampG and ampD into E. cloacae 55M-L reconstituted the inducible wild-type phenotype. These results indicate that ampG is required for the activation of ampC by AmpR. Without ampG, neither induction nor high-level expression of AmpC is possible. It is likely that the ampG gene product and AmpD together modulate the ability of AmpR to activate ampC expression.

show abstract

Genetic Control of -Lactamase Production in Enterobacter cloacae

Cited by 44 publications

References 0 publications

Expression of the AsbA1, OXA-12, and AsbM1 beta-lactamases in Aeromonas jandaei AER 14 is coordinated by a two-component regulon

Expression of the AsbA1, OXA-12, and AsbM1 beta-lactamases in Aeromonas jandaei AER 14 is coordinated by a two-component regulon

Altered phenotypes associated with ampD mutations in Enterobacter cloacae

ampG is essential for high-level expression of AmpC beta-lactamase in Enterobacter cloacae

Contact Info

Product

Resources

About