COMPARATIVE ANALYSIS OF DISC DIFFUSION WITH SERIAL DILUTION FOR SUSCEPTIBILITY TESTING OF SOME BACTERIAL ISOLATES

Abstract

Antimicrobial resistance remains a major public health challenge, necessitating reliable laboratory methods for determining bacterial susceptibility. This study aimed to compare the disc diffusion and serial dilution methods to evaluate their accuracy and level of agreement in antimicrobial susceptibility testing (AST). Twenty (20) bacterial isolates comprising Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus were identified through Gram staining and biochemical tests, then tested using both methods following CLSI guidelines. Results revealed a high level of resistance, particularly to ciprofloxacin and amoxicillin, with both methods producing comparable interpretations. Statistical analysis showed no significant difference (p > 0.05) and a Cohen’s Kappa value of 0.88, indicating almost perfect agreement. The study concludes that both methods are reliable for AST; however, while disc diffusion is simple and cost-effective for routine diagnostics, the serial dilution method offers greater precision for determining minimum inhibitory concentrations (MICs).