Thirty five sinus samples obtained from endoscopic patients who were suffering from chronic sinusitis and admitted to AL-Jumhori, AL-Rabie private, AL-Zahrawi private hospitals in Mosul city from March 2013 to March 2014 were conducted .Samples were cultured and pure isolates were identified to species level using morphological, biochemical and physiological tests. PCR was done using plasmids isolated from species under study by using primers for mrkA gene .mrkA gene was found in four species: Moraxella spp., Enterobacter aerogenes, E. coli and Citrobacter freundii. Nucleotide sequencing was done for isolated mrkA gene and homology searches were conducted between the sequences of standard gene BLAST program which is available at the National Center for Biotechnology Information (NCBI) and Basic Local Alignment Search program Tool(BLAST). Variations appear as transversion mutation which causes change tryptophan amino acid to leucine amino acid and there was transition mutation which causes change from aspartite amino acid to asparagine.