A Comprehensive Review on the Antimicrobial Culture Susceptibility Patterns and Intravenous-to-Oral Conversion of Antibiotics

Abstract Antimicrobial resistance is a major challenge in managing bacterial infections, emphasizing appropriate antibiotic selection, culture-directed therapy, and antimicrobial stewardship. This review summarizes antimicrobial culture and susceptibility patterns and examines the principles and application of intravenous-to-oral (IV-to-oral) antibiotic conversion. Culture and susceptibility testing support identification of causative microorganisms, selection of effective targeted therapy, and de-escalation of unnecessary broad-spectrum antibiotics. Local susceptibility patterns reported from tertiary-care hospitals in and around Coimbatore highlight the importance of hospital-specific microbiological data for empirical antibiotic selection. IV-to-oral conversion can be considered when patients show clinical improvement, hemodynamic stability, adequate gastrointestinal function, and the ability to tolerate oral medication with an effective oral antibiotic available. Sequential, switch, and step-down therapies are the main approaches to conversion. Appropriate conversion can reduce unnecessary intravenous exposure, catheter-related complications, treatment costs, nursing requirements, and hospital stay while improving patient comfort and mobility. Clinical pharmacists contribute by identifying eligible patients, reviewing antimicrobial therapy, interpreting susceptibility results, and supporting rational antibiotic selection. Standardized protocols, regular antibiotic review, updated antibiograms, and multidisciplinary collaboration can strengthen implementation. Integrating microbiological evidence with structured IV-to-oral conversion supports safer and more rational antibiotic use. Keywords: Antimicrobial resistance; Antibiotic susceptibility; Microbial culture; Intravenous-to-oral conversion; Sequential therapy; Step-down therapy; Antimicrobial stewardship; Clinical pharmacist