Can inhibitor-resistant substitutions in the Mycobacterium tuberculosis β-Lactamase BlaC lead to clavulanate resistance?: a biochemical rationale for the use of β-lactam-β-lactamase inhibitor combinations.
The current emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis calls for novel treatment strategies. Recently, BlaC, the principal β-lactamase of Mycobacterium tuberculosis, was recognized as a potential therapeutic target. The combination of meropenem and clavulanic acid, which inhibits BlaC, was found to be effective against even extensively drug-resistant M. tuberculosis strains when tested in vitro. Yet there is significant concern that drug resistance against this combination will also emerge. To investigate the potential of BlaC to evolve variants resistant to clavulanic acid, we introduced substitutions at important amino acid residues of M. tuberculosis BlaC (R220, A244, S130, and T237). Whereas the substitutions clearly led to in vitro clavulanic acid resistance in enzymatic assays but at the expense of catalytic activity, transformation of variant BlaCs into an M. tuberculosis H37Rv background revealed that impaired inhibition of BlaC did not affect inhibition of growth in the presence of ampicillin and clavulanate. From these data we propose that resistance to β-lactam-β-lactamase inhibitor combinations will likely not arise from structural alteration of BlaC, therefore establishing confidence that this therapeutic modality can be part of a successful treatment regimen against M. tuberculosis.
Department of Internal Medicine, Division of Pulmonary, Critical Care, and Sleep Medicine, University Hospitals Case Medical Center, Cleveland, Ohio, USA.
Sebastian G
SG
Kurz
Kerstin A
KA
Wolff
Saugata
S
Hazra
Christopher R
CR
Bethel
Andrea M
AM
Hujer
Kerri M
KM
Smith
Yan
Y
Xu
Lee W
LW
Tremblay
John S
JS
Blanchard
Liem
L
Nguyen
Robert A
RA
Bonomo
D019943:Amino Acid Substitution; D000995:Antitubercular Agents / Q000494:pharmacology*; D019818:Clavulanic Acid / Q000494:pharmacology*; D004359:Drug Therapy, Combination; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D054908:Extensively Drug-Resistant Tuberculosis / Q000382:microbiology; D015870:Gene Expression; D006801:Humans; D000077731:Meropenem; D008826:Microbial Sensitivity Tests; D016297:Mutagenesis, Site-Directed; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification; D015202:Protein Engineering; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013845:Thienamycins / Q000494:pharmacology*; D065093:beta-Lactamase Inhibitors / Q000494:pharmacology*; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
D000995:Antitubercular Agents; D011994:Recombinant Proteins; D013845:Thienamycins; D065093:beta-Lactamase Inhibitors; D019818:Clavulanic Acid; D001618:beta-Lactamases; D000077731:Meropenem