Objectives: To investigate the extrahospital dissemination of carbapenem-resistant Klebsiella pneumoniae isolates and the mechanisms of acquired resistance.
Methods: Patients who were referred to the outpatient department of Serres General Hospital with community-onset infections due to carbapenem-resistant K. pneumoniae isolates during August 2007-October 2008 were included in the study. The selected isolates were tested by determination of agar dilution MICs, phenotypic carbapenemase testing and PFGE. PCR and sequencing analyses were employed for identification of bla genes and mapping of the integron carrying the metallo-β-lactamase (MBL) gene. The location of the MBL allele was investigated by mating experiments, plasmid analysis and PCR assays.
Results: Twenty-four carbapenem-resistant K. pneumoniae isolates causing urinary tract infections were recovered from 12 outpatients. Six of the patients presented with recurrent infections within a period of 1-6 months after the initial extrahospital isolation. All patients reported prior hospitalization within the preceding 4 months, whilst two were infected by carbapenem-resistant K. pneumoniae isolates during their previous hospitalization. Imipenem, meropenem and ertapenem MICs ranged from 8 to 64 mg/L, 4 to 32 mg/L and 8 to 128 mg/L, respectively. All studied isolates as well as those obtained from prior hospitalization belonged to a single PFGE clone. They harboured a plasmid-mediated bla(VIM-1) gene in an integron structure that has been previously described among K. pneumoniae isolates causing hospital-acquired infections in Greece.
Conclusions: This is the first study to document the dissemination of an MBL-producing K. pneumoniae strain in the community. The successful strain caused recurrent community-onset infections and was most likely acquired during patients' previous hospitalization.