Identification of Risk Factors for Healthcare-Associated, Intrically Colistin Resistant Bacteries: A 12-Year Single Center Experience

Introduction: Colistin is one of the commonly used antibiotics in intensive care units for the treatment of multidrug-resistant bacterial infections, especially caused by carbapenem-resistant Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacteriaceae family members. The common use of colistin may result in emergence of colistin resistance, occurrence of unwanted side effects as well as an increased incidence of intrinsically colistin-resistant microorganisms. The present study aimed to investigate the effect of colistin use on the incidence of intrinsically colistin-resistant microorganisms and the distribution of these microorganisms in a tertiary hospital. Materials and Methods: Accordingly, the relationship between colistin use and the incidence of Burkholderia cepacia, Serratia marcescens, Proteus spp, Providencia spp, Morganella morganii and Stenotrophomonas maltophilia strains, which are colistin-resistant bacteria, isolated from healthcare-associated infections between January 2006 and September 2018 was evaluated. A total of 222 patients diagnosed with healthcare-associated infections were included in our study. Patients were divided into two groups as identified intrinsically colistin resistant bacteria and those infected with resistant Acinetobacter baumannii, Pseudomonas aurogenosa and Enterobacriaceae. Results: Two hundred and twenty-two patients were included in the study. Rates of colistin-resistant microorganisms were as follows: Proteus spp, 29%; Serratia spp., 9.9%; Morganella spp., 6.8%; S. maltophilia, 6.8%; B. cepacia, 2.7%; and Providencia spp., 0.5%. Findings revealed a 2.28-fold increase in the incidence of intrinsically colistin-resistant bacteria with the use of colistin. The incidence of colistin-resistant bacteria was statistically significantly higher in patients with coronary artery disease, patients with tracheostomy, and patients on mechanical ventilation, enteral feeding and carbapenem therapy compared to the control group (p=0.035, p= 0.037, p= 0.034, p= 0.023, p= 0.034). Conclusion: It should be kept in mind when using colistin that the frequency of intrinsically colistin-resistant bacteria may increase and alternatives to colistin should be used to reduce both the emergence of colistin resistance and the frequency of intrinsically coilstin-resistant bacteria.