| Congresso Brasileiro de Microbiologia 2023 | Resumo: 941-2 | ||||
Resumo:Enterobacterales resistant to carbapenems are frequently isolated from blood cultures, associated with high morbidity and mortality and require the use of last resource antibiotics, such as polymyxins. Rapid and accurate detection of polymyxins resistance is required, as they remain an important therapeutic choice in many regions of the world. We evaluated the rapid colorimetric polymyxin B microelution (RCPEm) test, from colonies obtained after the isolation of the pathogens in solid culture medium and directly from positive blood cultures, to quickly detect polymyxin B resistance. Blood cultures bottles positive for Enterobacterales (only one per patient), recovered from patients attending Hospital de Clínicas de Porto Alegre from April to May, 2023, were included in the study. Colonies from solid culture medium were subject to broth microdilution (BMD) to determine susceptibility to polymyxin B, as recommended by EUCAST/BRCAST. E. coli ATCC 25922 and Morganella morganii (intrinsically resistant to polymyxins) were used as susceptible and resistant controls, respectively. The RCPEm methodology consists of exposing bacteria to a solution (NP solution) where a disc of polymyxin B was previously eluted to obtain a concentration of 3 μg/mL. The test is read every 1 hour for up to 4 hours. Bacterial growth was detected by the change in color of the solution, which contains the phenol red indicator. According to BMD, of the 50 isolates tested (50 blood cultures), 44 were susceptible and 6 were resistant to polymyxin B. The RCPEm presented 100% of concordance when performed directly from blood cultures and from colonies. Reproducibility of results was also maintained across errors, with a major error for K. pneumoniae (MIC 2 μg/mL) and a very major error for K. pneumoniae (MIC 4 μg/mL). The RCPEm presented 83.3%, 97.7%, 83.3% and 97.7% of sensitivity, specificity, positive and negative predictive values, respectively. Overall, RCPEm presented a satisfactory performance for detecting polymyxin B resistance directly from positive blood cultures, with the exception of isolates with borderline MICs. Palavras-chave: blood culture, colorimetric test, microelution, polymyxin | |||||