ABSTRACT
An 85-year-old male with a tumour in his right lung was admitted to Internal Diseases Ward to continue treatment after suffering a sudden cardiac arrest. An empiric antibiotic therapy with amoxycillin was introduced due to increased inflammation markers. Blood and sputum were collected. An abundant growth of AmpC ß-lactamase-producing Citrobacter freundii was observed in culture grown from the sputum. The antibiogram showed retained sensitivity to fluoroquinolones. The therapy was modified by replacing ß-lactam with ciprofloxacin. Neither clinical nor laboratory improvement were observed. Blood culture indicated sepsis of Acinetobacter baumannii etiology. The strain was suspected of producing OXA carbapenemase (CARBA test positive), KPC (-), MBL (-). Antibiogram illustrated retained sensitivity to gentamicin and colistin with complete resistance to ciprofloxacin. Another modification in treatment was implemented and ciprofloxacin was replaced with colistin.