Amikacin for the treatment of carbapenem-resistant Klebsiella pneumoniae infections: clinical efficacy and toxicity

Infections by carbapenem-resistant Klebsiella pneumoniae (CRKp) are an increasing global threat with limited therapeutic options. Our objective was to evaluate clinical and microbiological outcomes of patients treated with amikacin for CRKp infections. We did a retrospective cohort of patients > 18 years old, with CRKp infections treated with amikacin in two tertiary care hospitals in Porto Alegre, Brazil. The impact of clinical factors, antibiotic treatment, and amikacin minimum inhibitory concentration (MIC) on patients’ 30-day mortality was assessed. Microbiological clearance and nephrotoxicity (assessed by RIFLE score) were evaluated as secondary outcomes. A Cox regression analysis was done for mortality. We included 84 patients for analysis. Twenty-nine (34.5%) patients died in 30 days. Amikacin MIC values ranged from 0.125 to 8 μg/mL and did not influence on mortality, regardless of the prescribed dose of this antibiotic (P = 0.24). Bacterial clearance occurred in 17 (58.6%) of 29 patients who collected subsequent cultures. Two (16.6%) of the 12 persistently positive cultures changed the amikacin susceptibility profile from susceptible to intermediate. Twenty-nine (37.2%) patients developed acute kidney injury (AKI): risk 13, injury 11, and failure 5. Risk factors for AKI were higher baseline eGFR (P < 0.01) and combination therapy with colistin (P = 0.02). Comparing patients who received combination with colistin vs polymyxin B, AKI occurred in 60.0% vs 20.6%, respectively, P < 0.01. Fifteen of the 16 (16.6%) patients who developed renal injury or failure were receiving colistin. In conclusion, amikacin was an effective treatment for CRKp infections. Within susceptible range, amikacin MIC values did not influence on clinical outcomes. Combination therapy of amikacin and colistin was highly nephrotoxic and should be used with caution.