Outbreak of hypervirulent Klebsiella pneumoniae harbouring blaVIM-2 among mechanically-ventilated drug-poisoning patients with high mortality rate in Iran

Carbapenem-resistant Klebsiella pneumoniae infections are associated with increased rates of treatment failure and death. Several studies have reported isolates with a combined hypervirulent and antimicrobial-resistant phenotype. In this study, the molecular characteristics of hypervirulent K. pneumoniae (hvKP) isolated from mechanically-ventilated patients admitted to a toxicological intensive care unit (ICU) in Tehran, Iran, were examined. String test, antimicrobial susceptibility testing, virulence factors analysis and plasmid replicon typing were performed. The clonal relatedness of the isolates was analysed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). hvKP accounted for 9.4% (5/53) of K. pneumoniae isolated from ventilator-associated pneumonia among patients admitted to the ICU with acute drug poisoning. The mortality rate was 7.5% (4/53) among K. pneumoniae-infected patients. All fatal K. pneumoniae were hvKP isolates, were resistant to imipenem and harboured an aacA7, blaVIM-2 and dhfrI cassette arrangement in a class 1 integron. The isolates were shown to be ST23 (Pasteur scheme) and exhibited similar PFGE patterns. Plasmid analysis revealed a class 1 integron harbouring blaVIM-2 located on an ca. 45-kb IncN plasmid. Here we describe the emergence of VIM-2-producing hvKP serotype K1/ST23 in an outbreak with high mortality in a hospital toxicological ICU. It appears that we must alert and prepare the hospital's surveillance system for the appearance, expansion and clinical importance of new K. pneumoniae clones associated with high antimicrobial resistance and robust virulence capabilities.