Correlation between the Transcriptional Level of iss and bor Virulence Genes of Avian Pathogenic Escherichia Coli O78 Inoculated to Chicken Serum

Background: Blue Open Reading (bor) and increased serum survival (iss) genes, with intense structural and possible functional similarities, engage in the serum resistance of Avian Pathogenic Escherichia coli O78 (APEC-O78). Objectives: This research aimed to determine whether there is a correlation between the transcriptional level of bor and iss of APEC-O78 inoculated in serum. Methods: Total RNA was extracted 24, 28, and 32 hrs after the inoculation of an APEC-O78 isolate, χ1378, to chicken serum. The fluorescence intensities related to the bands of gel electrophoresis of bor and iss were computed after cDNA synthesis and reverse transcription -PCR reaction assay. Using Pearson’s partial correlation tests, the relationship between the transcriptional levels of bor and iss, and the influence of the selected time points on the possible relationship were respectively measured at p <0.05 for statistical significance. Results: A correlation was observed between the transcription levels of bor and iss (P=.012), which was not influenced by the selected time points (P=.001). Conclusions: The bor must be carefully weighed in the transcriptional analysis including iss and vice versa. The number of transcripts/alleles, upstream sequence, regulation process at the pre-transcriptional phase, and the location of bor and iss in χ1378, and taking samples from different time intervals may explain our result. Our findings emphasizes the multifactorial and complex mechanism of APEC-O78 serum resistance, and can lay the foundation for further studies on the transcription of bor and iss, particularly in the specific strain and the three time points.