J Med Assoc Thai 2021; 104 (10):126-133

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Factors Associated with Microbiological Outcomes to Colistin in Patients with Multidrug-resistant Gram-Negative Bacterial Infections
Promsen P Mail, Arrayasillapaotorn N , Anutrakulchai S , Chetchotisakd P , Anunnatsiri S

Background: Multidrug-resistant (MDR) gram-negative bacterial infections continuously increases in prevalence, rate of ICU admission and mortality. Although, colistin has been used to treat MDR organisms, the controversial outcomes regarding its efficacy and safety were reported. Therefore, factors related with microbiological response to colistin should be determined.
Objective: To evaluate the rate and related factors of microbiological outcome in patients who received intravenous colistin for treatment of MDR gram-negative bacterial infections.
Materials and Methods: The retrospective cohort study was performed in adult patients between June 2015 and June 2017. Patient information, microbiology data, duration of colistin treatment and clinical outcomes were reviewed and analyzed. Microbiological responses were classified as either eradication or persistence of the initial MDR bacteria. Factors influencing microbiological response were determined by multiple logistic regression analysis.
Results: 303 colistin-given patients were enrolled with the mean age of 62.8±18.3 years. Pneumonia and soft tissue infections were the most two common sites of infection. Reports of culture revealed monomicrobial gram-negative bacteria 80.5%. Acinetobacter baumannii and Pseudomonas aeruginosa were the major organisms accounting for 79.9% and 17.2%, respectively. Microbiological clearance rate of colistin was 66%. Multivariate analysis demonstrated the factors related with poor microbiological response were (a) AKI before colistin treatment associated with higher severity of AKI (b) presence of pneumonia, (c) infection with P. aeruginosa and (d) mixed gram-negative bacterial infections. The overall mortality rate was 39.3% with no significant differences of mortality rate and incidence of AKI after colistin administration between the eradication and persistence groups.
Conclusion: Colistin accomplished with rather good microbiological response in clearance of MDR gram-negative bacteria. AKI influenced the microbiological response therefore early and aggressive care to prevent AKI is mandatory. Additionally, because of high non-response rate in P. aeruginosa infection, combined antibiotics and surveillance may be crucial.

Keywords: Colistin; Microbiological response; Factors for good and poor outcomes

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