Co-production of SFO-1 and DHA-1 β-lactamases and 16S rRNA methylase ArmA in clinical isolates of Klebsiella pneumoniae.
OBJECTIVE
To investigate the epidemiology and genetic characteristics of the plasmid-mediated extended-spectrum β-lactamase (ESBL) gene bla(SFO-1) in clinical isolates of ESBL-producing Klebsiella pneumoniae and Escherichia coli.


METHODS
The prevalence of the bla(SFO-1) gene was examined by PCR amplification. Conjugation and transformation experiments were performed and the presence of antimicrobial resistance determinants was investigated by the PCR method. The genetic environments of the bla(SFO-1) and armA genes were determined by direct sequencing of plasmid pHS20. Plasmids were typed by PCR-based replicon typing. PFGE and multilocus sequence typing were performed on SFO-producing strains.


RESULTS
Of 158 ESBL-producing strains of K. pneumoniae, 3 (1.9%) carried the bla(SFO-1) gene. All of the SFO-producing isolates belonged to the ST11 epidemic clone, with a single PFGE type and had high-level resistance to third-generation cephalosporins, aminoglycosides and ciprofloxacin. The bla(SFO-1) gene was co-transferred with the armA, aac(6')-Ib-cr and bla(TEM-1) genes by transformation, whereas the armA, bla(DHA-1) and qnrB4 genes were co-transferred by conjugation. The armA genes were located within the composite transposon Tn1548 on two different plasmids in the strain 08-129. The bla(SFO-1) gene was located upstream of an ampR gene from the coding region and flanked by two inverted repeats of IS26. Plasmids carrying bla(DHA-1) were identified as IncFII, while the bla(SFO-1)-bearing plasmids were non-typeable.


CONCLUSIONS
Although SFO-1 is a low-occurrence ESBL, it has been captured by a plasmid accumulating multiple resistance determinants including armA and aac(6')-Ib-cr, and accompanied by a large DHA-1-bearing IncFII plasmid in a prevalent K. pneumoniae ST11 clone.
Institute of Antibiotics, Huashan Hospital, Fudan University, Shanghai, China.
Qinglan
Q
Guo
Peng
P
Wang
Ying
Y
Ma
Yang
Y
Yang
Xinyu
X
Ye
Minggui
M
Wang
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology; D006801:Humans; D007710:Klebsiella Infections / Q000382:microbiology*; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D008780:Methyltransferases / Q000235:genetics*; D058885:Multilocus Sequence Typing; D010957:Plasmids; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D014169:Transformation, Bacterial; D001618:beta-Lactamases / Q000235:genetics*
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D008780:Methyltransferases; C035181:rRNA (adenosine-O-2'-)methyltransferase; D001618:beta-Lactamases