Genomic variations between colistin-susceptible and -resistant Pseudomonas aeruginosa clinical isolates and their effects on colistin resistance.
OBJECTIVE
The emergence of colistin-resistant Pseudomonas aeruginosa is becoming a serious concern worldwide. We investigated genetic variations involved in the acquisition and loss of colistin resistance in three clinical isogenic P. aeruginosa isolates (GKK-1, GKK-2 and GKK-3) recovered from a single patient and assessed their impacts on colistin resistance.


METHODS
We applied whole genome sequencing technology to identify single nucleotide polymorphisms and insertions or deletions in two colistin-resistant isolates compared with a susceptible isolate.


RESULTS
Thirty-seven non-synonymous mutations in 33 coding sequences were detected in the colistin-resistant isolates GKK-1 and GKK-3. Only one gene (PA1375) was significantly down-regulated in both colistin-resistant isolates; this gene encodes erythronate-4-phosphate dehydrogenase. Among the eight genes that were up-regulated in the colistin-resistant isolates, three encoded hypothetical proteins (PA1938, PA2928 and PA4541) and five were predicted to be involved in core biological functions, encoding a cell wall-associated hydrolase (PA1199), a response regulator EraR (PA1980), a sensor/response regulator hybrid (PA2583), a glycosyltransferase (PA5447) and an arabinose efflux permease (PA5548). All mutants with allelic replacement of these candidate genes, apart from one (PA1375), exhibited increases in colistin susceptibility, ranging from 2- to 16-fold. Colistin susceptibility decreased in complemented strains compared with the mutants; however, in three cases, resistance did not reach wild-type level.


CONCLUSIONS
This study demonstrates genetic differences between P. aeruginosa isogenic isolates and identifies novel determinants that may be associated with the acquisition of colistin resistance. These findings will lay the foundation for a complete understanding of the molecular mechanisms of colistin resistance in P. aeruginosa.
Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon, South Korea.
Ji-Young
JY
Lee
In Young
IY
Na
Young Kyoung
YK
Park
Kwan Soo
KS
Ko
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003091:Colistin / Q000494:pharmacology*; D004252:DNA Mutational Analysis; D024881:Drug Resistance, Bacterial; D016680:Genome, Bacterial; D006801:Humans; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D017422:Sequence Analysis, DNA
D000900:Anti-Bacterial Agents; D003091:Colistin
glycosyltransferases; two-component regulatory systems; whole genome sequencing