Identification by microarray of a common pattern of gene expression in intact intestine and cultured intestinal cells exposed to virulent Aeromonas hydrophila isolates

Predicting virulence of Aeromonas isolates based on changes in transcription of c-jun and c-fos in human tissue culture cells

AIMS

To screen for the virulence potential of Aeromonas isolates based on the change in regulation of c-jun and c-fos in the human intestinal tissue culture cell line Caco-2.

METHODS AND RESULTS

Aeromonas cells were added to Caco-2 cells at a ratio of approx. 1 : 1. After 1-, 2- and 3-h incubation at 37 degrees C, mRNA was extracted from the cells and gene expression of two host genes, c-jun and c-fos, quantified. Aeromonas isolates which were pathogenic in the neonatal mouse model demonstrated up-regulation of c-jun and c-fos compared to avirulent isolates.

CONCLUSIONS

Human cell culture results showed that c-jun and c-fos were predictive of Aeromonas virulence.

SIGNIFICANCE AND IMPACT OF THE STUDY

An Aeromonas relative virulence scale is proposed for use in the testing of Aeromonas drinking water isolates.

Evaluating virulence of waterborne and clinical Aeromonas isolates using gene expression and mortality in neonatal mice followed by assessing cell culture's ability to predict virulence based on transcriptional response

AIMS

To assess the virulence of Aeromonas spp. using two models, a neonatal mouse assay and a mouse intestinal cell culture.

METHODS AND RESULTS

After artificial infection with a variety of Aeromonas spp., mRNA extracts from the two models were processed and hydridized to murine microarrays to determine host gene response. Definition of virulence was determined based on host mRNA production in murine neonatal intestinal tissue and mortality of infected animals. Infections of mouse intestinal cell cultures were then performed to determine whether this simpler model system's mRNA responses correlated to neonatal results and therefore be predictive of virulence of Aeromonas spp. Virulent aeromonads up-regulated transcripts in both models including multiple host defense gene products (chemokines, regulation of transcription and apoptosis and cell signalling). Avirulent species exhibited little or no host response in neonates. Mortality results correlated well with both bacterial dose and average fold change of up-regulated transcripts in the neonatal mice.

CONCLUSIONS

Cell culture results were less discriminating but showed promise as potentially being able to be predictive of virulence. Jun oncogene up-regulation in murine cell culture is potentially predictive of Aeromonas virulence.

SIGNIFICANCE AND IMPACT OF THE STUDY

Having the ability to determine virulence of waterborne pathogens quickly would potentially assist public health officials to rapidly assess exposure risks.