Plasmid pKpQIL encoding KPC-3 and TEM-1 confers carbapenem resistance in an extremely drug-resistant epidemic Klebsiella pneumoniae strain.
OBJECTIVE
An extremely drug-resistant (XDR) clone of KPC-3-producing Klebsiella pneumoniae emerged in Israel in 2006, causing a nationwide outbreak. We aimed to characterize the local KPC-3-encoding plasmid carried by these isolates and study its contribution to antibiotic resistance.


METHODS
Mechanisms of carbapenem resistance were investigated in seven selected isolates (isolated between 2006 and 2008) belonging to the epidemic clone. Isolates underwent MIC testing, and were examined for the presence of KPC, Tn4401, class I integron elements and additional antibiotic resistance genes. Plasmids were analysed by transformation, transconjugation, restriction mapping, curing and complementation experiments. Outer membrane protein (OMP) analysis was performed.


RESULTS
OMP analysis did not reveal loss of porins. KPC-3-producing K. pneumoniae isolates possessed various plasmids but all harboured a common self-transmissible 105 kb plasmid, termed pKpQIL, encoding bla(TEM-1) and bla(KPC-3). Curing of pKpQIL led to a complete loss of resistance to cephalosporins and carbapenems, proving its crucial role in carbapenem resistance. Transformation of plasmid pKpQIL into the cured Klebsiella strain resulted in full reconstitution of carbapenem resistance. The presence of all Tn4401 transposon elements located upstream of the KPC-3 gene was detected by PCR and sequencing. pKpQIL lacked additional antibiotic resistance genes.


CONCLUSIONS
Our findings demonstrate the presence of pKpQIL, a 105 kb KPC-3- and TEM-1-encoding plasmid, in the XDR K. pneumoniae epidemic strain in Israel. pKpQIL is unique and appears consistently in all isolates of this clone over the years. The extensive beta-lactam resistance phenotype of this clone is primarily mediated by this single self-transmissible plasmid.
Leavitt
Azita
A
Molecular Epidemiology and Antimicrobial Resistance Laboratory, Division of Epidemiology, Tel Aviv Medical Center, Tel Aviv, Israel.
Chmelnitsky
Inna
I
Ofek
Itzhak
I
Carmeli
Yehuda
Y
Navon-Venezia
Shiri
S
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000235:genetics; D015780:Carbapenems / Q000494:pharmacology*; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000235:genetics; D004196:Disease Outbreaks; D024901:Drug Resistance, Multiple, Bacterial; D006801:Humans; D007557:Israel / Q000453:epidemiology; D007710:Klebsiella Infections / Q000453:epidemiology / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D010957:Plasmids / Q000032:analysis* / Q000235:genetics; D016133:Polymerase Chain Reaction; D001618:beta-Lactamases / Q000096:biosynthesis* / Q000235:genetics
D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D015780:Carbapenems; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D001618:beta-Lactamases; C495220:beta-lactamase KPC-3, Klebsiella pneumoniae; C034413:beta-lactamase TEM-1