Increased Vancomycin Susceptibility in Mycobacteria: a New Approach To Identify Synergistic Activity against Multidrug-Resistant Mycobacteria

Abstract

Mycobacterium tuberculosis is wrapped in complex waxes, impermeable to most antibiotics. Comparing Mycobacterium bovis BCG and M. tuberculosis mutants that lack phthiocerol dimycocerosates (PDIM) and/or phenolic glycolipids with wild-type strains, we observed that glycopeptides strongly inhibited PDIM-deprived mycobacteria. Vancomycin together with a drug targeting lipid synthesis inhibited multidrug-resistant (MDR) and extensively drug-resistant (XDR) clinical isolates. Our study puts glycopeptides in the pipeline of potential antituberculosis (TB) agents and might provide a new antimycobacterial drugscreening strategy. Mycobacterium tuberculosis remains a leading cause of morbidity, tuberculosis (TB), and mortality in the world. M. tuberculosis is intrinsically resistant to most classical antibiotics, partly because of its impermeable cell wall (1-6). Due to selective mutations in M. tuberculosis, almost one-third of new TB patients are now infected with first-line drug-resistant strains, monoresistant strains, or multidrug-resistant (MDR) strains. Consequently, second-line therapies are often implemented, leading to the appearance of extensively drug-resistant (XDR) strains (7,8). There is therefore a growing urgency in the need for new antimycobacterial therapies.The mycobacterial cell wall is composed of peptidoglycan covalently attached to arabinogalactan, which are in turn esterified by very-long-chain mycolic acids. Various noncovalently attached lipids are embedded at the outer surface and necessary for capsule formation. Among these lipids, two related waxes, phthiocerol dimycocerosates (PDIM) and phenolic glycolipids (PGL), are involved in virulence (9-11). PDIM and PGL are only or mostly, respectively, found in pathogenic mycobacteria, but their roles in antibiotic resistance remain unclear (12-16). In Mycobacterium marinum, a mild (2-to 10-fold) increase in antibiotic susceptibility was observed in PDIM-and PGL-deficient strains (14, 15). In contrast, in PDIM-and PGL-deficient M. tuberculosis, no change was detected (13).The present study aimed to understand how mycobacteria can become susceptible to glycopeptides. Using PDIM-negative and/or PGL-negative strains of Mycobacterium bovis BCG and M. tuberculosis, we investigated the correlation between the absence of PDIM and the glycopeptide susceptibility. Subsequently, we investigated whether vancomycin could synergistically inhibit MDR and XDR strains with a mycobacterial lipids synthesis inhibitor.We recently reported that the chaperonin Cpn60.1/GroEL-1/ Hsp60-1 of M. bovis BCG was necessary for the integrity of the cell wall as the ⌬cpn60.1 strain showed an abnormal mycobacterial cell wall with a lack of PDIM and mycolates with two more carbon atoms (17). We investigated the susceptibility of the wild-type (WT), ⌬cpn60.1, and complemented ⌬cpn60.1 M. bovis BCG (GL2 strain) strains to several antituberculosis drugs. We used the NCCLS agar proportion method (18) to determine the MIC scale range of each antibiotic. We inoculated equal quantities of s...

Esx Systems and the Mycobacterial Cell Envelope: What's the Connection?

“…Both mycobacteria and diderm-LPS bacteria are intrinsically resistant to several antibiotics, including the large hydrophilic glycopeptide vancomycin (122,123). Consistent with the idea that mycobacterial lipids provide a permeability barrier, mycobacterial strains lacking PDIM have increased susceptibility to vancomycin (124,125).…”

Efficacy of β-lactam/β-lactamase inhibitor combination is linked to WhiB4-mediated changes in redox physiology of Mycobacterium tuberculosis

“…Lack of the Rv1258c pump and PDIM lipids have been reported to sensitize Mtb towards β-lactams and vancomycin (Dinesh et al, 2013; Soetaert et al, 2015). Several PE_PGRS genes involved in maintaining cell wall architecture and protection from oxidative stresses were up-regulated in MtbΔwhiB4 (Figure 6E) (Fishbein et al, 2015).…”

Mycobacterium tuberculosis Rv1152 is a Novel GntR Family Transcriptional Regulator Involved in Intrinsic Vancomycin Resistance and is a Potential Vancomycin Adjuvant Target

“…Van, in combination with lipid biosynthesis targeting antibiotic, was recently found more effective in killing multidrug-resistant (MDR) and extensively-drug resistant (XDR) M. tuberculosis 35. Interestingly, Rv1152 decreased susceptibility of M. smegmatis to vancomycin, as the MIC of MS_Rv1152 for vancomycin is 80 μg/ml while MS_Vec is 20 μg/ml, there is no significant difference in MIC when using Cip, OFL, Nor, Ery, INH, and Rif (Table 3).…”