Polymyxin-resistant Pseudomonas aeruginosa assigned as ST245: First report in an intensive care unit in Sao Paulo, Brazil

Abstract

Objectives: Pseudomonas aeruginosa is a Gram-negative bacterium that causes severe infections, especially in hospitalised and immunocompromised patients. Polymyxins are the last therapeutic option to treat infections caused by this micro-organism. Here we describe a polymyxin-resistant P. aeruginosa assigned as sequence type (ST) 245 for the first time in Brazil. Methods: Antimicrobial susceptibility testing of the isolate was performed. In addition, whole-genome sequencing was performed and its virulence and resistance genes were analysed. Results: The P. aeruginosa ST245 isolate was identified for the first time in Brazil in a patient with ventilator-associated pneumonia hospitalised at Hospital das Clinicas, Sao Paulo. Analysis of the genome showed the presence of several resistance and virulence genes. Mutations in beta-lactam resistance genes were found in beta-lactamases, outer membrane proteins, efflux pump and penicillin-binding proteins. Polymorphisms related to pathways leading to polymyxin resistance are also present, such as lipid A or keto-deoxyoctulosonate modification with aminoarabinose as well as activation of lipopolysaccharide (LPS). Conclusion: Such findings may represent an alert for the spread of an unusual profile in the country.