ABSTRACT Background: Breast cancer is one of the most prevalent types of malignant tumors in the world. Bacteria have been linked with cancer through two mechanisms, the frst, stimulating chronic infammation, and the second, production of carcinogenic bacterial metabolites. The most common types of adenovirus in cancer patients are serotypes 7 and 11 of type B, and serotypes 1, 2, and 5 are of type C. Methods: In this study, 98 blood and 50 urine, samples were collected from women with breast cancer at the Center for Oncology and Hematology in Kirkuk city in addition to 30 blood and 20 urine samples collected from healthy persons as control. Pathogenic gram-negative bacteria were isolated, identifed in addition to checking their susceptibility to antibiotics. Antibodies (IgM, IgG) of adenovirus type-7 were involved in this study by the ELISA technique. Results: In this study, 22 gram-negative bacterial species were isolated from patients with breast cancer, including (31.81% Klebsiella pneumoniae, 45.45% E. coli, 18.18% Proteus mirabilis and 4.54% Acinetobacter baumannii). Gram-negative bacteria showed high resistance to antibiotics (approximately absolute resistance) amoxicillin/clavulanic acid, ampicillin, ceftazidime, amoxicillin, cephalothin, vancomycin. Adenovirus type-7 antibodies were detected by using the ELISA technique (3.84% IgM and 91.02% IgG). Viral and bacterial co-infection were also included in this study caused by the involvement of Escherichia coli + ADV-7, P. mirabilis + ADV-7, and K. pneumoniae + ADV-7. Keywords: Breast cancer, Gram-negative bacteria, Multi-drug resistance, Adenovirus Type-7 (IgM and IgG), ELISA, Co-infection. International Journal of Pharmaceutical Quality Assurance (2020); DOI: 10.25258/ijpqa.11.2.5 How to cite this article: Ali AA, Alabden SSZ, Zaman NAQ. Prevalence of some gram-negative bacteria and adenovirus in breast cancer patients in Kirkuk city. International Journal of Pharmaceutical Quality Assurance. 2020;11(2):224-227. Source of support: Nil Confict of interest: None Prevalence of some Gram-Negative Bacteria and Adenovirus in Breast Cancer Patients in Kirkuk City Asmaa A Ali 1 , Salah S Z Alabden 2 , Najat A Zaman 3 1,3 Department of Biology, College of Science, University of Kirkuk, Iraq 2 Department of Biology, College of Education for Pure Science, University of Kirkuk, Iraq Received: 16th March, 2020; Revised: 19th April, 2020; Accepted: 28th May, 2020; Available Online: 25th June, 2020 INTRODUCTION Breast cancer is one of the most common types of malignant tumors in cancer records; cancer caused by breast tissue and most common from the inner lining of milk ducts or lobules that supply ducts to milk. Breast cancer is one of the most common causes of death in women and is the most frequently diagnosed cancer in women. 1 Most breast tumors are benign. Breast cancer is a term given to malignant breast tumors and is more common in women and less frequent in men. Genetic factors cause 25% of breast cancer. 2,3 Breast cancer is one of the leading causes of mortality worldwide, afecting one in eight women worldwide. Regardless of the eforts spent through intensive research, the exact causes of breast cancer are still unknown, but many genetic, genetic, and environmental factors have been identifed as a result. The origin of the vast majority of 70% of breast cancer cases is still unknown. 4 Cancer patients undergo intensive chemotherapy with immunosuppressive drugs and radiation therapy in an attempt to destroy the RESEARCH ARTICLE tumor. These measures also attack the immune system, which reduces the patient’s immunity, which exposes the patient to opportunistic diseases. 5 More than 15% of malignant tumors worldwide can be attributed to microorganism infection or about 1.2 million cases per year. 6 Recent research suggests that microorganisms in women with breast cancer are diferent from healthy ones. 4 Women with breast cancer have a higher incidence of Staphylococcus, Bacillus, and Enterobacteriaceae than women who have not had breast cancer .7,8 Multiple bacterial resistance increases mortality, as many bacteria have developed multiple resistance mechanisms. For example, the predominant mechanism of resistance to β-lactam antibiotics by the gram-negative bacteria is the production of the enzyme β-lactamase, while gram-positive bacteria are resistant to β-lactam antibiotics by altering the target location of penicillin-binding proteins (PBPs). 9 * Author for Correspondence: bahar.o@yahoo.com