Comparative Antimicrobial Activity of Amikacin and Gentamicin on Clinically Important Bacteria - Abstract
Aminoglycosides discovered 80 years ago are still the drug of choice for combating a range of infections, including those caused by multiple drug-resistant (MDR) strains of bacteria. These bactericidal antibiotics are nephrotoxic and ototoxic and often not permitted for therapeutic use in animals and birds. This study analyzed the comparative in vitro antimicrobial activity of amikacin and gentamicin on 517 isolates of potentially pathogenic bacteria isolated from environment and food samples (53), reference strains (11) and from clinical samples (453) of defined ailments in animals (299), humans (85), and birds (69). Gentamicin inhibited 77.37%, and amikacin inhibited 73.11% of the isolates. Of 378 strains of bacteria susceptible to amikacin 13.76% were resistant to gentamicin, and of the 400 strains susceptible to gentamicin 18.50% were resistant to amikacin. A significant (p <0.001) correlation between carbapenem resistance and amikacin (r, 0.264) and gentamicin (r, 0.31) resistance was apparent. Susceptibility to gentamicin and amikacin varied among different bacteria like Alcaligenes spp. (15.38%, and 23.08%), Enterococcus spp. (37.50%,
and 37.50%), Escherichia spp.(27.13%, and 24.03%), Klebsiella spp. (1.58%, and 21.05%), Pantoea agglomerans(24.14%, and 31.03%), Proteus spp. (28.57%, and 78.57%), Pseudomonas spp. (15.38%, 26.92%), Salmonella enterica ssp. enterica serovars (16.67%, and 16.67%), Staphylococcus spp. (18.81%, and 24.75%), and Streptococcus spp. (34.69%, and 44.90%), respectively. Source of the bacterial strains also affected the susceptibility viz., 13.33% and 46.67% of E. coli isolates from poultry birds were resistant to gentamicin and amikacin, respectively but none of the E. coli isolated
from infections in pigs was resistant to gentamicin or amikacin. Bacteria associated with eye, gastrointestinal tract and genital tract infections were more often resistant to amikacin than those associated with otitis and septicaemia. Proteus, Staphylococcus and Streptococcus species strains showed more resistance to amikacin than to gentamicin but the difference was statistically insignificant (p, >0.05). A wide variation in susceptibility of bacterial strains of different species causing various types of infections in animals and birds under different husbandry practices suggests that antimicrobial susceptibility should be conducted before the use of amikacin or gentamicin in therapeutics.