aminoarabinose and Pseudomonas-Infections

Colistin represents the last-line treatment option against many multidrug-resistant Gram-negative pathogens. Several lines of evidence indicate that aminoarabinosylation of the lipid A moiety of lipopolysaccharide (LPS) is an essential step for the development of colistin resistance in Pseudomonas aeruginosa. However, whether it is sufficient to confer resistance in this bacterium remains unclear. The aim of this work was to investigate the specific contribution of lipid A aminoarabinosylation to colistin resistance in P. aeruginosa and evaluate the effect of this resistance mechanism on bacterial fitness. Recombinant strains constitutively expressing the enzymes for lipid A aminoarabinosylation were generated in a small collection of reference and clinical isolates and verified by quantitative reverse transcription polymerase chain reaction (qRT-PCR), lipid A extraction and mass spectrometry. The effect of aminoarabinosylated lipid A on colistin resistance was found to be strain- and culture condition-dependent. Higher levels of resistance were generally obtained in the presence of divalent cations, which appear to be important for aminoarabinosylation-mediated colistin resistance. High colistin resistance was also observed for most strains in human serum and in artificial sputum medium, which should partly mimic growth conditions during infection. The results of growth, biofilm, cell envelope integrity and Galleria mellonella infection assays indicate that lipid A aminoarabinosylation does not cause relevant fitness costs in P. aeruginosa.

Topics: Animals; Anti-Bacterial Agents; Arabinose; Biofilms; Colistin; Disk Diffusion Antimicrobial Tests; Drug Resistance, Multiple, Bacterial; Humans; Lipid A; Moths; Pseudomonas aeruginosa; Pseudomonas Infections

Three structural features of lipid A (addition of palmitate [C16 fatty acid], addition of aminoarabinose [positively charged amino sugar residue], and retention of 3-hydroxydecanoate [3-OH C10 fatty acid]) were determined for Pseudomonas aeruginosa isolates from patients with cystic fibrosis (CF; n=86), from the environment (n=13), and from patients with other conditions (n=14). Among P. aeruginosa CF isolates, 100% had lipid A with palmitate, 24.6% with aminoarabinose, and 33.3% retained 3-hydroxydecanoate. None of the isolates from the environment or from patients with other conditions displayed these modifications. These results indicate that unique lipid A modifications occur in clinical P. aeruginosa CF isolates.

Topics: Arabinose; Child; Child, Preschool; Chronic Disease; Cystic Fibrosis; Decanoic Acids; Humans; Infant; Lipid A; Lung Diseases; Palmitates; Prevalence; Pseudomonas aeruginosa; Pseudomonas Infections

Cystic fibrosis (CF) patients develop chronic airway infections with Pseudomonas aeruginosa (PA). Pseudomonas aeruginosa synthesized lipopolysaccharide (LPS) with a variety of penta- and hexa-acylated lipid A structures under different environmental conditions. CF patient PA synthesized LPS with specific lipid A structures indicating unique recognition of the CF airway environment. CF-specific lipid A forms containing palmitate and aminoarabinose were associated with resistance to cationic antimicrobial peptides and increased inflammatory responses, indicating that they are likely to be involved in airway disease.

Topics: Acylation; Antimicrobial Cationic Peptides; Arabinose; Bacterial Proteins; Cells, Cultured; Cystic Fibrosis; Drug Resistance, Microbial; Humans; Infant; Interleukin-8; Lipid A; Lipopolysaccharides; Magnesium; Mutation; Palmitates; Peptides; Polymyxins; Pseudomonas aeruginosa; Pseudomonas Infections; Respiratory System; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Virulence