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Gentamicin-resistant Pseudomonas aeruginosa: Mayo Clinic Experience, 1970-1976
Abstract:
During the period 1970 through 1976, there were 144 patients from whom gentamicin-resistant Pseudomonas aeruginosa (minimum inhibitory concentration [MIC], more than 5 microgram/ml) was isolated. In 20(21 percent) of the 95 patients who acquired such organisms within our institutions, the occurrence was considered clinically significant. Factors that favored the appearance of gentamicin-resistant P. aeruginosa included prolonged hospitalization, previous antibiotic treatment, increased gentamicin usage, underlying disease, and instrumentation (70 percent). Virulence of gentamicin-resistant isolates appeared less than that of susceptible organisms, with bacteremia due to these isolates occurring in only three cases. Resistant isolates with MICs for gentamicin of 8 to 16 microgram/ml were more susceptible to tobramycin than to amikacin, whereas isolates with MICs for gentamicin of 64 microgram/ml or greater were more susceptible to amikacin than to tobramycin. Eighty percent of all strains were susceptible to 128 microgram/ml or less of carvenicillin. Favorable results occurred in 12 or 13 cases treated with gentamicin plus carbenicillin, whereas treatment with either of these agents alone resulted in failure or relapse in 7 of 14 cases.
Insights
Gentamicin-resistant Pseudomonas aeruginosa emerged in hospitalized patients, often linked to prolonged stays and antibiotic use. Combination therapy with gentamicin and carbenicillin showed favorable outcomes for treating resistant infections.
Area of Science:
- Medical Microbiology
- Infectious Diseases
- Clinical Pharmacy
Background:
- Gentamicin resistance in Pseudomonas aeruginosa poses a significant clinical challenge.
- Understanding the epidemiology and risk factors for gentamicin-resistant P. aeruginosa is crucial for infection control.
Purpose of the Study:
- To investigate the incidence, clinical significance, and risk factors associated with gentamicin-resistant Pseudomonas aeruginosa.
- To evaluate the in vitro susceptibility of resistant isolates to other antibiotics and assess treatment outcomes.
Main Methods:
- Retrospective analysis of patient data from 1970-1976.
- Isolation and susceptibility testing of Pseudomonas aeruginosa strains.
- Clinical outcome assessment for patients with gentamicin-resistant P. aeruginosa.
Main Results:
- 144 patients had gentamicin-resistant P. aeruginosa isolated; 21% of hospital-acquired infections were clinically significant.
- Prolonged hospitalization, prior antibiotics, increased gentamicin use, and instrumentation were key risk factors.
- Resistant strains showed variable susceptibility to tobramycin and amikacin; most were susceptible to carbenicillin.
- Combination therapy (gentamicin plus carbenicillin) yielded better results than monotherapy.
Conclusions:
- Gentamicin resistance in P. aeruginosa is associated with specific patient and treatment factors.
- Susceptibility patterns guide antibiotic selection for resistant infections.
- Combination therapy with gentamicin and carbenicillin appears effective in managing gentamicin-resistant P. aeruginosa infections.