Activities of fluoroquinolone, macrolide, and aminoglycoside drugs combined with inhibitors of glycosylation and fatty acid and peptide biosynthesis against Mycobacterium avium

Abstract

Smooth-and rough-colony variants of Mycobacterium avium serovar 4 were treated with three classes of drugs. The drugs were chosen for their potential inhibitory effects on the biosynthesis of the cell envelopeassociated serovar-specific glycopeptidolipid antigens. Growth was monitored radiometrically with a BACTEC 460-TB instrument, and MICs were determined for each drug. Both variants were then treated with inhibitory drugs in combination with antimicrobial agents that have demonstrated effectiveness against M. avium. No growth inhibition was observed with 6-fluoro-6-deoxy-D-glucose or avidin. Inhibitors of glycosylation, i.e., 2-deoxy-D-glucose, bacitracin, and ethambutol, were inhibitory to smooth-and rough-colony variants, whereas drugs that inhibit peptide synthesis, i.e., N-carbamyl-L-isoleucine and m-fluoro-phenylalanine, were more inhibitory for the rough-colony variant. Cerulenin, which affects fatty acid synthesis, was inhibitory for both variants, but it appeared to be more effective at inhibiting the growth of the smooth-colony variant at equivalent concentrations. Generally, when inhibitors of glycosylation were used with sparfloxacin and amikacin, a synergistic effect was observed for only the smooth variant. When drugs that affect peptide synthesis were used in combination with amikacin, a synergistic effect was observed for the rough variant, and when cerulenin was used in combination with sparfloxacin or amikacin, a synergistic effect was observed for both variants. Lipid analysis revealed that although the rough variant lacks the serovar-specific glycopeptidolipid antigens, it does possess a group of phenylalanine-isoleucine-containing lipopeptides that may explain its different susceptibility patterns to m-fluoro-phenylalanine and N-carbamyl-L-isoleucine. The significance of these results is discussed with reference to various components in the cell envelope and their importance in cell wall permeability.The new emphasis of the National Institute of Allergy and Infectious Diseases is "to spark efforts" to better understand the opportunistic infections associated with AIDS so that new and effective treatments can be developed (45). A major obstacle preventing the development of better therapies for those opportunistic pathogens is a "basic lack of knowledge about the pathogens that cause such diseases" (45). The Mycobacterium avium complex represents one of the most important groups of opportunistic pathogens infecting patients with AIDS (23,45 Rastogi et al. (33) proposed that a polysaccharide outer layer may be responsible for the impermeability of smoothtransparent variants to various substrates and drugs and also increased pathogenicity. The presence of the fibrillar material described by Draper (13) and Kim et al. (21) and later referred to as the superficial L, layer (2) may also be important as a barrier because of the polar glycopeptidolipids (GPLs) that make up its superficial location (4, 6, 44). Crowle et al. (9) suggested that both the polysaccharide layer (32, 33) and the GPL layer...

Genes Required for Intrinsic Multidrug Resistance in Mycobacterium avium

“…The multidrug resistance of MAC is usually ascribed to intrinsic properties of the organism's lipid-rich cell wall, although additional factors may contribute (2,19,23,27,36). A role for the cell wall has been inferred from indirect observations.…”

A Unique Phenylalanine‐Containing Lipopeptide Isolated from a Rough‐Colony Variant of Mycobacterium Avium

“…When examined by TLC, the distribution of radioactivity in internally radiolabeled lipids extracted from MAC 702 revealed a group of lipids that radiolabeled with [14C]Phe and ['4C]Ile (Fig. 1) [7,91. The HPLC pattern for radiolabeled lipid extracted from MAC702 is given in Fig.…”

“…Neither lipopeptide contained alaninol, a component commonly found in glycopeptidolipid components, and neither contained carbohydrate [lo]. The presence of the phenylalanineisoleucine-containing lipopeptide has been noted in three rough- colony variants of M. avium serovars 4, 8, and 20 [9], a smoothcolony variant of serovar 4 [7], and more recently has been observed in a smooth-opaque, a smooth-transparent, and roughcolony variant of at least one other M. avium isolate [31]. In addition, Belisle et al have reported the presence of a phenylalanine-containing lipopeptide proposed to be a precursor in glycopeptidolipid biosynthesis [8].…”

“…A rough colony variant was chosen because of their inability to produce complete glycosylated glycopeptidolipid components [7,8,113. By using ['4C-]phenylalanine and ['4C-]isoleucine to internally radiolabel the lipids of this rough colony variant (results reported here), it was apparent that a similar lipopeptide was present in sufficient quantities to allow for structural studies.…”

“…More recently, it has become apparent that other phenylalanine-containing lipopeptides are associated with the cell envelope of M. avium and may play a role in glycopeptidolipid biosynthesis [7, 81. One such lipopeptide has been previously identified in both smooth and rough colony variants of M. avium [7, 91. This particular lipopeptide was observed to accumulate following inhibition of glycopeptidolipid biosynthesis, and it was thought that it might represent a precursor in that biosynthetic pathway [lo].…”