Microorganisms play an important role in causing diseases, sinusitis is one of these diseases which cause a health problems to many people. This study therefore was oriented to nominate the species of microorganisms isolated from Acute, Subacute and Chronic sinusitis. The causative organisms were identified by biochemical and physiological tests, and their susceptibility to selective antibiotics were tested, the Colony Forming Unit (CFU/cm 3) and the number of pus cells were also determined. The following bacterial species were isolated from sinusitis patients: Klebsiella pneumoniae (24%), Streptococcus viridans (9%), Staphylococcus aureus (8%), Bacillus spp. (6.7%), Staphylococcus epidermidis (6.1%), Streptococcus pneumoniae (4.9%), Proteus vulgaris (4%), Escherichia coli (3%), Moraxella catarrhalis (2%), Streptomyces somaliensis (1.2%), Corynebacterium diphtheriae (0.6%), Coryn. Pseudodiphtheriticum (0.6%), Coryn. Haemolyticum (0.6%), Coryn. Pyogenes (0.6%), Nocardia asteroids (0.6%), Listeria monocytogenes (0.6%), Candida albicans (0.6%). On the other hand Haemophilus influenzae could not be isolated. Chronic sinusitis dominated in male cases (11-15) years old and in female (16-20) years old. The antibiotic biogram showed that Ciprofloxacin has an activity against all bacterial isolates which were resistant to Colxacillin, Penicillin G and Ampicillin and produced β-lactamase.

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.