Morphotype switching was presented as the proportion (%) of alternative types in relation to the total colonies present. Discussion Our previous paper reported MI-503 supplier a process of B. pseudomallei colony morphology switching that occurred during human melioidosis, and in an animal model, mouse macrophage cell line J774A.1, human lung epithelial cell line A549, and under starvation conditions in vitro. In this study, we investigated whether the variable phenotype associated with different morphotypes resulted in a survival

fitness or disadvantage during interactions with a human macrophage cell line U937 and after exposure to factors that simulate the macrophage milieu. Although our previous report described 7 different morphotypes from clinical isolates, the five isolates used here from 3 different clinical and 2 environmental samples were only observed to switch under nutritional limitation from parental type I to types II and III, allowing comparison of 3 isogenic morphotypes with known variable phenotype. The initial interaction between the human macrophage cell

line U937 and 3 isogenic morphotypes of B. pseudomallei was not different between the three types. Despite a comparable rate of extracellular growth between isogenic morphotypes, heterogeneity in subsequent intracellular survival/growth after this time point was observed. Type III of each isolate was inconsistently capable of multiplication after uptake by human macrophages, and was associated with a change in morphotype. This suggests that type III has a fitness disadvantage under these circumstances. selleckchem A possible explanation for this is that type III does not appear to

produce www.selleckchem.com/products/Roscovitine.html biofilm [11]. A biofilm mutant demonstrated a mark reduction in intracellular survival in primary human macrophages than the wild type, suggesting that biofilm production is associated with the ability to survive in human macrophages [8]. Our previous study examined the survival and replication of B. pseudomallei strain 153 in the human respiratory epithelial cell line not A549 and the mouse macrophage cell line J744A.1. Our finding here that type III of strain 153 had increased survival in the human macrophage cell line U937 is consistent with our previous findings for the mouse macrophage cell line J774A.1 infected with the same strain [11]. However, the use of a wider number of strains in this study demonstrated that there was a lack of reproducibility between strains. We suggest that this is likely relate to variability in genomic content between the strains tested. Future testing strategies require the evaluation of a large numbers of strains that have undergone whole genome sequencing to facilitate statistically robust comparisons between genomic variation and phenotypic behaviour. Several components of the innate immune system are efficient in killing organisms within human macrophages [15].