Aminoglycoside Resistance in Common Pathogens

This study investigated the resistance patterns to aminoglycosides among 137 bacterial isolates derived from various clinical specimens submitted to the Microbiology Laboratory at XXX Training and Research Hospital in the year 2005. The bacterial isolates were Escherichia coli (n=34), Klebsiella pneumoniae (n=30), Pseudomonas aeruginosa (n=30), Acinetobacter baumannii (n=23), and Staphylococcus aureus (n=20). Staphylococcus aureus was further classified into methicillin-susceptible strains (MSSA, n=13) and methicillin-resistant strains (MRSA, n=7). We examined the susceptibility against eight distinct aminoglycosides. Isepamicin exhibited the lowest overall resistance rates within Gram-negative bacilli, particularly among isolates of P. aeruginosa and A. baumannii derived from intensive care units (ICUs). Streptomycin presented the highest levels of resistance. Statistically significant differences in resistance rates were observed between ICU and non-ICU isolates for gentamicin (χ² = 11.19, p = 0.0037), amikacin (χ² = 8.82, p = 0.0121), and isepamicin (χ² = 9.67, p = 0.0079). This suggests an increased resistance rate in intensive care units. MRSA strains were more resistant to various aminoglycosides, including gentamicin, tobramycin, and isepamicin, in comparison to MSSA strains. These observed differences were not statistically significant. These resistance patterns highlight the limitations of older drugs like streptomycin and kanamycin. The sustained efficacy of isepamicin and netilmicin positions them as viable treatment alternatives, particularly for infections caused by multidrug-resistant organisms. The results point to the necessity for routine susceptibility testing, careful antimicrobial stewardship, and judicious antibiotic selection to enhance patient outcomes and address resistance in high-risk environments such as the ICU.