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In vitro sensitivity of Proteus organisms to gentamicin and sisomicin
Abstract:
The antibacterial activity of gentamicin and sisomicin was studied in 148 recent clinical isolates of Proteus obtained from patients hospitalized in Athens. Both gentamicin and sisomicin were found to be active with sisomicin generally being the more active of the two; P. mirabilis strains were less susceptible than the indole-positive strains, but P. mirabilis organisms isolated from the respiratory tract were more sensitive to sisomicin than those isolated from the urine. Susceptibility testing with the two aminoglycoside antibiotics was affected by inoculum size and by the test broth used. Sisomicin sensitivity testing with the disc-agar diffusion method and broth dilution method was reliable for the indole-positive strains of Proteus but did not separate all sensitive from resistant strains of P. mirabilis. An in vitro synergism was demonstrated between sisomicin and the semisynthetic penicillin, ticarcillin.
Insights
Sisomicin demonstrated superior antibacterial activity against Proteus clinical isolates compared to gentamicin. Synergistic effects were observed between sisomicin and ticarcillin, offering potential therapeutic advantages.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Proteus species are significant nosocomial pathogens.
- Aminoglycoside antibiotics like gentamicin and sisomicin are crucial for treating Proteus infections.
- Understanding the comparative efficacy and resistance patterns of these antibiotics is vital for effective clinical management.
Purpose of the Study:
- To evaluate and compare the in vitro antibacterial activity of gentamicin and sisomicin against clinical isolates of Proteus.
- To investigate the influence of inoculum size and test broth on antibiotic susceptibility testing.
- To explore potential synergistic interactions between sisomicin and ticarcillin.
Main Methods:
- Antibacterial activity testing of gentamicin and sisomicin against 148 clinical Proteus isolates.
- Susceptibility testing using disc-agar diffusion and broth dilution methods.
- Evaluation of synergistic activity between sisomicin and ticarcillin.
Main Results:
- Sisomicin exhibited greater activity than gentamicin against most Proteus strains.
- Indole-positive Proteus strains were more susceptible than P. mirabilis strains.
- Respiratory tract P. mirabilis isolates showed higher sensitivity to sisomicin than urinary isolates.
- In vitro synergism was observed between sisomicin and ticarcillin.
Conclusions:
- Sisomicin is a potentially more effective aminoglycoside than gentamicin for treating Proteus infections.
- Standardized susceptibility testing methods are crucial, as inoculum size and broth can affect results.
- The combination of sisomicin and ticarcillin shows promise for enhanced antibacterial efficacy.