2 research outputs found
The minimal inhibitory concentration for sulbactam was not associated with the outcome of infections caused by carbapenem-resistant Acinetobacter sp. treated with ampicillin/sulbactam
OBJECTIVE: The objective of this study was to evaluate whether the outcomes of carbapenem-resistant Acinetobacter infections treated with ampicillin/sulbactam were associated with the in vitro susceptibility profiles. METHODS: Twenty-two infections were treated with ampicillin/sulbactam. The median treatment duration was 14 days (range: 3-19 days), and the median daily dose was 9 g (range: 1.5-12 g). The median time between Acinetobacter isolation and treatment was 4 days (range: 0-11 days). RESULTS: The sulbactam minimal inhibitory concentration (MIC) ranged from 2.0 to 32.0 mg/L, and the MIC was not associated with patient outcome, as 4 of 5 (80%) patients with a resistant infection (MIC≥16), 5 of 10 (50%) patients with intermediate isolates (MIC of 8) and only 1 of 7 (14%) patients with susceptible isolates (MIC ≤4) survived hospitalization. CONCLUSION: These findings highlight the need to improve the correlation between in vitro susceptibility tests and clinical outcome
Comparison of disc diffusion, Etest and broth microdilution for testing susceptibility of carbapenem-resistant P. aeruginosa to polymyxins
Abstract\ud
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Background\ud
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Considering the increasing use of polymyxins to treat infections due to multidrug resistant Gram-negative in many countries, it is important to evaluate different susceptibility testing methods to this class of antibiotic.\ud
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Methods\ud
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Susceptibility of 109 carbapenem-resistant P. aeruginosa to polymyxins was tested comparing broth microdilution (reference method), disc diffusion, and Etest using the new interpretative breakpoints of Clinical and Laboratory Standards Institute.\ud
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Results\ud
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Twenty-nine percent of isolates belonged to endemic clone and thus, these strains were excluded of analysis. Among 78 strains evaluated, only one isolate was resistant to polymyxin B by the reference method (MIC: 8.0 μg/mL). Very major and major error rates of 1.2% and 11.5% were detected comparing polymyxin B disc diffusion with the broth microdilution (reference method). Agreement within 1 twofold dilution between Etest and the broth microdilution were 33% for polymyxin B and 79.5% for colistin. One major error and 48.7% minor errors were found comparing polymyxin B Etest with broth microdilution and only 6.4% minor errors with colistin. The concordance between Etest and the broth microdilution (reference method) was respectively 100% for colistin and 90% for polymyxin B.\ud
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Conclusion\ud
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Resistance to polymyxins seems to be rare among hospital carbapenem-resistant P. aeruginosa isolates over a six-year period. Our results showed, using the new CLSI criteria, that the disc diffusion susceptibility does not report major errors (false-resistant results) for colistin. On the other hand, showed a high frequency of minor errors and 1 very major error for polymyxin B. Etest presented better results for colistin than polymyxin B. Until these results are reproduced with a large number of polymyxins-resistant P. aeruginosa isolates, susceptibility to polymyxins should be confirmed by a reference method.Financial support: Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP).Financial support: Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)