Bacterial diarrhea is a serious public health concern, especially in children under five. Early exposure to a wide range of enteric bacterial infections causes children in underdeveloped countries to suffer from many episodes of diarrheal illness.

Background: Diarrheal diseases are a common disease worldwide associated with high morbidity and mortality rates in children under the age of five especially in developing countries. Enteric bacterial are most common causative agents of diarrhea and become a challenges to prevent and treat diarrhea due to emergency of antimicrobial resistant. Objective: The aims of this study was to isolate and determine prevalence and antimicrobial susceptibility patterns of Escherichia coli , Salmonella , and Shigella species among under five years age diarrheal children attending Mettu Karl Comprehensive Specialized Hospital, Southwest Ethiopia June to August, 2023 Methods: A cross-sectional study was conducted from June to August 2023 on 382 at Mettu Karl Comprehensive Specialized Hospital, Southwest Ethiopia. A structured questionnaire were used to collect data from children under five who had diarrhea. Data collection was done using convenience sample technique. Each collected sample was inoculated onto Selenite F broth and MacConkey agar. Antimicrobial susceptibility testing was performed using the Kirby Bauer disk method on Muller Hinton agar. Socio-demographic, clinical, and laboratory results data were entered in EpiData v4.6.0.6 and analyzed using SPSS version 25. Descriptive summaries, frequency, tables, and graphs were used to describe the study variables. Results: From the 382 children screened, bacteria were isolated from 44 (11.52%). This included; 19(5.0%) Escherichia coli , 14(3.66%) Salmonella species, and 11 (2.9%) Shigella . The highest resistance among bacteria was observed against Ampicillin (89.5%), cotrimoxazole (73.7%), and cefazolin (57.1%). Almost all of E.coli, Salmonella, and Shigella were susceptible to imipenem, cefepime, and cefotaxime. Of the total 44 isolates, 20(45.5%) showed multidrug resistance. Conclusion and Recommendation: This study indicates that E. coli, Salmonella , and Shigella were isolated pathogenic bacteria. The identified bacteria were susceptible to Imipenem, cefepime, and cefotaxime. The highest prevalence of antimicrobial resistance was observed for ampicillin followed by cotrimoxazole and cefazolin. Also, isolated bacteria showed resistance to ceftriaxone, ceftazidime, azithromycin, and ciprofloxacin and multiple antimicrobial resistances were high among those bacteria. It is better to use potent antimicrobials like Imipenem, Cefepime, and Cefotaxime for the treatment of bacterial-caused diarrhea.