Somaye Abbasi - Department of Pathobiology, Faculty of Veterinary Medicine, University of Zabol, Zabol, Iran
Saeed Salari - Department of Pathology, Faculty of Veterinary Medicine, University of Zabol, Zabol, Iran
Ahmad Rashki - Department of Pathobiology, Faculty of Veterinary Medicine, University of Zabol, Zabol, Iran
Mohsen Najimi - Department of Pathobiology, Faculty of Veterinary Medicine, University of Zabol, Zabol, Iran

 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 O۷۸ (APEC-O۷۸). OBJECTIVES: This research aimed to determine whether there is a correlation between the transcriptional level of bor and iss of APEC-O۷۸ inoculated in serum. METHODS: Total RNA was extracted ۲۴, ۲۸, and ۳۲ hrs after the inoculation of an APEC-O۷۸ isolate, χ۱۳۷۸, 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<۰.۰۵ for statistical significance. RESULTS: A correlation was observed between the transcription levels of bor and iss (P=.۰۱۲), which was not influenced by the selected time points (P=.۰۰۱). 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 χ۱۳۷۸, and taking samples from different time intervals may explain our result. Our find-ings emphasizes the multifactorial and complex mechanism of APEC-O۷۸ 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.

APEC, bor, iss, semi-quantitative Reverse Transcription PCR, serum resistance