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Resistance to imipenem among selected gram-negative bacilli in the United States
1Hospital Infections Program, National Center for Infectious Diseases, Centers for Disease Control, Atlanta, Georgia 30333.
Objectives:
Identification of imipenem resistance among selected gram-negative bacilli, especially Pseudomonas aeruginosa and Enterobacter species.
Methods:
We analyzed 1986-1990 National Nosocomial Infection Surveillance (NNIS) data from 3,316 P aeruginosa isolates and 1,825 Enterobacter species isolates for which susceptibility results to imipenem were reported.
Results:
For P aeruginosa, 11.1% of the isolates were resistant to imipenem; 16.1% were either intermediate-susceptible or resistant to the drug. A logistic regression model found that resistance was more common among P aeruginosa isolated from the respiratory tract, patients in intensive care units, and in teaching hospitals. Additionally, resistance to imipenem increased by 25% in teaching hospitals from 1986-1988 to 1989-1990. For Enterobacter species, 1.3% of the isolates were resistant to imipenem; 2.3% were either intermediate-susceptible or resistant to the drug. However, imipenem resistance for these isolates did not differ between the two periods and was not more common in patients in an intensive care unit or infections at any specific site.
Conclusions:
The frequency of resistance to imipenem is greater among P aeruginosa than among Enterobacter species. Resistance to imipenem among the P aeruginosa isolates is more common from strains isolated from patients with nosocomial infections in an intensive care unit, from the respiratory tract, and from teaching hospitals. Resistance appears to be increasing among nosocomial P aeruginosa isolated in teaching hospitals.
Insights
Imipenem resistance is higher in Pseudomonas aeruginosa than Enterobacter species. Resistance in P. aeruginosa is increasing, particularly in teaching hospitals and intensive care units.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Nosocomial infections pose a significant threat in healthcare settings.
- Gram-negative bacilli are common causes of hospital-acquired infections.
- Imipenem is a critical broad-spectrum antibiotic used to treat serious infections.
Purpose of the Study:
- To identify the prevalence of imipenem resistance in Pseudomonas aeruginosa and Enterobacter species.
- To analyze trends and risk factors associated with imipenem resistance.
Main Methods:
- Analysis of National Nosocomial Infection Surveillance (NNIS) data from 1986-1990.
- Inclusion of 3,316 P. aeruginosa and 1,825 Enterobacter species isolates with reported imipenem susceptibility.
- Logistic regression modeling to identify resistance predictors.
Main Results:
- 11.1% of P. aeruginosa isolates were resistant to imipenem; 16.1% were intermediate or resistant.
- P. aeruginosa resistance was associated with respiratory tract infections, intensive care units, and teaching hospitals.
- Imipenem resistance in P. aeruginosa increased by 25% in teaching hospitals between 1986-1988 and 1989-1990.
- 1.3% of Enterobacter species isolates were resistant; 2.3% were intermediate or resistant.
- No significant differences in Enterobacter species resistance were observed over time or by patient location/infection site.
Conclusions:
- P. aeruginosa exhibits a higher frequency of imipenem resistance compared to Enterobacter species.
- Risk factors for P. aeruginosa resistance include intensive care unit stays, respiratory infections, and teaching hospital environments.
- A concerning increase in imipenem resistance among nosocomial P. aeruginosa in teaching hospitals was observed.