Effect of colony morphology variation of Burkholderia pseudomallei on intracellular survival and resistance to antimicrobial environments in human macrophages in vitro.
BACKGROUND
Primary diagnostic cultures from patients with melioidosis demonstrate variation in colony morphology of the causative organism, Burkholderia pseudomallei. Variable morphology is associated with changes in the expression of a range of putative virulence factors. This study investigated the effect of B. pseudomallei colony variation on survival in the human macrophage cell line U937 and under laboratory conditions simulating conditions within the macrophage milieu. Isogenic colony morphology types II and III were generated from 5 parental type I B. pseudomallei isolates using nutritional limitation. Survival of types II and III were compared with type I for all assays.


RESULTS
Morphotype was associated with survival in the presence of H2O2 and antimicrobial peptide LL-37, but not with susceptibility to acid, acidified sodium nitrite, or resistance to lysozyme, lactoferrin, human neutrophil peptide-1 or human beta defensin-2. Incubation under anaerobic conditions was a strong driver for switching of type III to an alternative morphotype. Differences were noted in the survival and replication of the three types following uptake by human macrophages, but marked strain-to strain-variability was observed. Uptake of type III alone was associated with colony morphology switching.


CONCLUSIONS
Morphotype is associated with phenotypes that alter the ability of B. pseudomallei to survive in adverse environmental conditions.
Department of Microbiology and Immunology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Sarunporn
S
Tandhavanant
Aunchalee
A
Thanwisai
Direk
D
Limmathurotsakul
Sunee
S
Korbsrisate
Nicholas Pj
NP
Day
Sharon J
SJ
Peacock
Narisara
N
Chantratita
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D023181:Antimicrobial Cationic Peptides; D016957:Burkholderia pseudomallei / Q000145:classification / Q000166:cytology* / Q000187:drug effects / Q000254:growth & development / Q000302:isolation & purification; D054804:Cathelicidins / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008264:Macrophages / Q000382:microbiology*; D008554:Melioidosis / Q000382:microbiology*; D050296:Microbial Viability / Q000187:drug effects; D020298:U937 Cells
D000900:Anti-Bacterial Agents; D023181:Antimicrobial Cationic Peptides; D054804:Cathelicidins; D006861:Hydrogen Peroxide