Tag: Antimicrobial Resistance

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Unique lipid A modifications in Pseudomonas aeruginosa isolated from the airways of patients with cystic fibrosis
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Ernst RK, Moskowitz SM, Emerson JC, et al. J Infect Dis. 2007 Oct

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 patientswith 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. … Continue readingUnique lipid A modifications in Pseudomonas aeruginosa isolated from the airways of patients with cystic fibrosis

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pmrA(Con) confers pmrHFIJKL-dependent EGTA and polymyxin resistance on msbB Salmonella by decorating lipid A with phosphoethanolamine
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Murray SR, Ernst RK, Bermudes D, et al. J Bacteriol 2007 Jul

Mutations in pmrA were recombined into Salmonella strain ATCC 14028 msbB to determine if pmrA-regulated modifications of lipopolysaccharide could suppress msbB growth defects. A mutation that functions to constitutively activate pmrA [pmrA(Con)] suppresses msbB growth defects on EGTA-containing media. Lipid A structural analysis showed that Salmonella msbB pmrA(Con) strains, compared to Salmonella msbB strains, have increased amounts of palmitate and phosphoethanolamine but no aminoarabinose addition, suggesting that aminoarabinose is not incorporated into msbB lipid A. Surprisingly, loss-of-function mutations in the aminoarabinose biosynthetic genes restored EGTA and polymyxin sensitivity to Salmonella msbB pmrA(Con) strains. These blocks in aminoarabinose biosynthesis also prevented lipid A phosphoethanolamine incorporation and reduced the levels of palmitate addition, indicating previously unknown roles for the aminoarabinose biosynthetic enzymes. Lipid A structural analysis of the EGTA- and polymyxin-resistant triple mutant msbB pmrA(Con) pagP::Tn10, which contains phosphoethanolamine but no palmitoylated lipid A, suggests that phosphoethanolamine addition is sufficient to confer EGTA and polymyxin resistance on Salmonella msbB strains. Additionally, palmitoylated lipid A was observed only in wild-type Salmonella grown in the presence of salt in rich media. Thus, we correlate EGTA resistance and polymyxin resistance with phosphoethanolamine-decorated lipid A and demonstrate that the aminoarabinose biosynthetic proteins play an essential role in lipid A phosphoethanolamine addition and affect lipid A palmitate addition in Salmonella msbB strains. … Continue readingpmrA(Con) confers pmrHFIJKL-dependent EGTA and polymyxin resistance on msbB Salmonella by decorating lipid A with phosphoethanolamine