Human bloodstream infection caused by a Colistin multidrug-resistant Acinetobacter baumannii strain: a case report

Multidrug-resistant Acinetobacter baumannii is an important pathogen causing healthcare-associated infections. The onset of Pan Drug Resistant (PDR) strains of A. baumannii, which are also resistant to colistin due to its excessive consumption, makes these strains difficult to eradicate. The appearance of new aggressive phenotypes among sentinel microorganisms in the control of healthcare-associated infections (HAI) requires the molecular approach to define a database of local nosocomial strains. Whole Genome Sequencing (WGS) is a useful tool to monitor the emergence of new aggressive bacterial phenotypes among sentinel microorganisms for the control of HAI. We describe a case report of colistin-resistant A. baumannii strain isolated from a blood-stream infection and evaluate the presence of antibiotic resistance genes (ARGs) by whole-genome sequencing (WGS). A colistin-resistant, PDR A. baumannii strain was isolated from blood cultures, bile fluid and wound in a patient with bacteremia in "Santa Maria delle Grazie Hospital" , Pozzuoli Italy. The strain was characterized by both biochemical and Whole Genome Sequencing (WGS) analysis. We identified a colistin-resistant strain of A. baumannii from a human bloodstream infection. WGS results were integrated with diagnostic procedures for a better characterization of the co-occurrence of several distinct antibiotic resistance mechanisms.