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Nosocomial gram-negative bloodstream isolates: a comparison of in vitro antibiotic potency
G L Stanley1, M A Pfaller, M Mori
1Department of Internal Medicine, University of Iowa College of Medicine, Iowa City.
Abstract:
Nosocomial bloodstream infections add to the morbidity, mortality and length of hospitalization that is attributed to the underlying diseases alone. We have compared the in vitro potency of fifteen antibiotics against 136 isolates from clinically significant nosocomial gram-negative bacteraemias. Ciprofloxacin was the most potent antibiotic and had the broadest spectrum of activity (98% of isolates susceptible, MIC90 range: 0.06-0.5 micrograms ml-1). We subjected all isolates to beta-lactamase induction but antibiotic susceptibility was unaffected by this procedure.
Insights
Ciprofloxacin demonstrated superior in vitro potency and the broadest spectrum against gram-negative bacteria causing nosocomial bloodstream infections. Antibiotic susceptibility remained unchanged after beta-lactamase induction in these isolates.
Area of Science:
- Infectious Diseases
- Microbiology
- Pharmacology
Background:
- Nosocomial bloodstream infections significantly increase patient morbidity, mortality, and hospital stays.
- Gram-negative bacteria are common causative agents of these serious hospital-acquired infections.
Purpose of the Study:
- To compare the in vitro effectiveness of fifteen different antibiotics against clinically significant nosocomial gram-negative bacteria.
- To identify the most potent antibiotic with the broadest spectrum of activity for treating these infections.
Main Methods:
- Evaluated the in vitro potency of fifteen antibiotics against 136 bacterial isolates from nosocomial gram-negative bacteraemias.
- Determined antibiotic susceptibility profiles, including Minimum Inhibitory Concentration 90 (MIC90) values.
- Assessed the impact of beta-lactamase induction on antibiotic susceptibility.
Main Results:
- Ciprofloxacin exhibited the highest in vitro potency and broadest spectrum of activity.
- 98% of the bacterial isolates were susceptible to ciprofloxacin, with an MIC90 range of 0.06-0.5 µg/mL.
- Beta-lactamase induction did not alter the antibiotic susceptibility of the tested isolates.
Conclusions:
- Ciprofloxacin is a highly effective antibiotic against the studied gram-negative bacteria responsible for nosocomial bloodstream infections.
- The findings support the use of ciprofloxacin for empirical or targeted therapy in such cases.
- Beta-lactamase production did not confer resistance to the tested antibiotics in this cohort.