Over the last few years, the interest in Aeromonas infection in India has gone beyond the boundaries due to the increase of diseases which is responsible for watery diarrhea. Most reports have described gastroenteritis, septicemia, meningitis, pneumonia, or surgical wound infections, primarily in immune-compromised patients¹. Infections caused by resistant microorganisms often fail to respond to the standard treatment, resulting in prolonged illness costing a financial burden to families and greater risk of death. This bacterium produces a large number of extracellular virulence factors that are closely associated with specific diseases. It is known that Aeromonas spp possess different chromosomal b-lactamase genes and most of the antibiotics have been rendered futile against this environmental pathogen thus forcing mankind to device methods for control and treatment against them by locating new drug targets. In this study, a total of 30 stool samples were collected from patients in an around hospitals in south Chennai with diarrhoea. A large number of A. hydrophila colonies were isolated and their antibiotic susceptibility pattern was analyzed. Amp C beta-lactamase is Ambler class C enzymes that confer resistance to extended spectrum cephalosporins and their detection is crucial, since the phenotypic tests are not standardized leading to ambiguity in interpretation of results. PCR technique detects antibiotic resistance to more than one antibiotic resistant genes thus facilitating to identify the pervasiveness of extended spectrum b-lactamase (ESBL) producing genes such as CTX-M, TEM and SHV in this study.