Background: In Brazil, cats in households has recently increased dramatically, likely due to their lower space and care requirements. We need to know the health of these companion animal species, since they have behavioral patterns that make them an important link in the epidemiological chain. Extended spectrum beta-lactamase producer strains (ESBL) are resistant to penicillin, cephalosporin and monobactam, but they are susceptible to clavulanate. The goal of this study is to detect strains of Enterobacteriaceae that produce extended spectrum beta-lactamase (ESBL) and evaluate the bacterial resistance profile in isolated cats (Felis silvestris catus) that live in a city located at west of Parana state, Brazil.Materials, Methods & Results: Swabs were aseptically collected from the anal orifice and oral cavity of 49 female domestic cats that were healthy upon clinical and physical examination, a minimum age of one year, weighing up to 3 kg, and had attended a veterinary clinic specializing in cats, in order to, later, perform the isolation and bacterial identification, antimicrobial sensibility phenotypic test and the phenotypic test to detect ESBL producer strains. From the 98 swabs collected it was possible to perform the bacterial isolation in 68 samples; 40.81% isolated from anal orifice and 28.57% isolated from oral cavity. From rectal and oral cavities 77.50% and 71.42% of the isolated were identified as Escherichia coli respectively, being 2.94% considered ESBL producer strains. In relation to bacterial resistance the antibiotics that shown more resistance in anal orifice were ampicillin, amoxicillin, nalidixic acid, sulfazotrim, tetracycline and aztreonam. In oral cavity they were ampicillin, amoxicillin, cefoxitin, amoxicillin + clavulanate, aztreonam, ceftriaxone and nalidixic acid; and the bacterial resistance index shown that 39.70% were considered high level risk.Discussion: Household cats have a very important role in society, since the benefits they provide to their owners are clear, however, it is worth pointing out that these animals also pose risks to human health, caused by the transmission of zoonoses and also the possibility of transfer of antimicrobial resistance genes between bacteria of animal and human origin, as well as between bacteria of the normal microbiota and pathogenic microorganisms of diferents origins. Therefore, it is important to understand the health of these companion animal species, because they exhibit behavioral patterns that make them an important link in the epidemiological chain of potentially infectious microorganisms, which may show antimicrobial resistance. Extended spectrum beta-lactamase producer strains (ESBL) are resistant to penicillin, cephalosporin and monobactam, but they are susceptible to clavulanate. These enzymes hydrolyze the beta-lactam ring of the antibiotic structure, inactivating them. Nowadays bacterial resistance is considered to be one of the greatest problems in public health worldwide, as infections and diseases outbraks are caused by multiresistant bacteria are more and more frequent. The results of this study demonstrate the presence of strains of Enterobacteriaceae family associated to the high bacterial resistance, with samples that indicate ESBL producer strains in domiciled cats, in a city of west Parana state in Brazil. These results confirm that these cats can be considered as reservoirs of different microbial agents and resistance gens, being a health problem by the possibility of dissemination. The cat population is multiplying in a higher proportion compared to dogs and may probably became predominant in less than one decade. Due this situation and thinking about human, animal and environmental health new phenotypic studies to confirm the resistance gens and ESBL producers should be conducted in this specie.