Loss of a Class A Penicillin-Binding Protein Alters β-Lactam Susceptibilities in Mycobacterium tuberculosis.
Recent studies have renewed interest in β-lactam antibiotics as a potential treatment for Mycobacterium tuberculosis infection. To explore the opportunities and limitations of this approach, we sought to better understand potential resistance mechanisms to β-lactam antibiotics in M. tuberculosis. We identified mutations in the penicillin-binding protein (PBP) ponA2 that were able to confer some degree of resistance to the cephalosporin subclass of β-lactams. Surprisingly, deletion of ponA2 also confers resistance, demonstrating that β-lactam resistance can spontaneously arise from PBP loss of function. We show that ponA2 mutants resistant to the cephalosporin subclass of β-lactams in fact show increased susceptibility to meropenem, a carbapenem that is known to target l,d-transpeptidases, thereby suggesting that in the absence of PonA2, an alternative mode of peptidoglycan synthesis likely becomes essential. Consistent with this hypothesis, a negative genetic selection identified the l,d-transpeptidase ldtMt2 as essential in the absence of ponA2. The mechanism of β-lactam resistance we outline is consistent with emerging models of β-lactam killing, while the investigation of ponA2 downstream and synthetic lethal genes sheds light on the mechanism of cell wall biosynthesis and the interaction between conventional PBPs and l,d-transpeptidases.
Department of Microbiology and Immunobiology, Harvard Medical School , 77 Avenue Louis Pasteur, Boston, Massachusetts 02115, United States.
Carl N
CN
Wivagg
Department of Microbiology and Immunobiology, Harvard Medical School , 77 Avenue Louis Pasteur, Boston, Massachusetts 02115, United States.|Department of Molecular Biology and Center for Computational and Integrative Biology, Massachusetts General Hospital, Richard B. Simches Research Center , 185 Cambridge Street, Seventh Floor, Boston, Massachusetts 02114, United States.
Samantha
S
Wellington
Broad Institute , 415 Main Street, Cambridge, Massachusetts 02142, United States.
James E
JE
Gomez
Department of Microbiology and Immunobiology, Harvard Medical School , 77 Avenue Louis Pasteur, Boston, Massachusetts 02115, United States.|Broad Institute , 415 Main Street, Cambridge, Massachusetts 02142, United States.|Department of Molecular Biology and Center for Computational and Integrative Biology, Massachusetts General Hospital, Richard B. Simches Research Center , 185 Cambridge Street, Seventh Floor, Boston, Massachusetts 02114, United States.
Deborah T
DT
Hung
D015964:Gene Expression Regulation, Bacterial; D016254:Mutagenesis, Insertional; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D046915:Penicillin-Binding Proteins / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D014376:Tuberculosis / Q000382:microbiology*; D018440:beta-Lactam Resistance / Q000187:drug effects* / Q000235:genetics*; D065093:beta-Lactamase Inhibitors / Q000494:pharmacology*; D047090:beta-Lactams / Q000037:antagonists & inhibitors*
D046915:Penicillin-Binding Proteins; D065093:beta-Lactamase Inhibitors; D047090:beta-Lactams
PonA2; actinobacteria; carbapenem; cephalosporin; loss of function; target site modification