Characterization of acquired beta-lactamases and their genetic support in multidrug-resistant Pseudomonas aeruginosa isolates in Taiwan: the prevalence of unusual integrons.
OBJECTIVE
The present study was conducted to investigate acquired beta-lactamases and their genetic support in 26 Pseudomonas aeruginosa isolates that were resistant to nearly all antipseudomonal drugs from six medical centres in Taiwan.


METHODS
Acquired beta-lactamases and their genetic support were determined by PCR-based strategies.


RESULTS
Four and 16 of the 26 isolates were found to produce VIM-2 and VIM-3 metallo-beta-lactamases (MBLs), respectively, and 1, 1 and 2 isolates produced OXA-17, OXA-10 and PSE-1, respectively. These bla genes are all in class 1 integrons that are probably chromosomally located. The bla(VIM-3)-containing integron, with a deletion between int1 and the bla(VIM-3) structural gene, has six gene cassettes, bla(VIM-3), a probable fosfomycin resistance determinant, aacA4, aacA4, aadB and aacA4. The bla(VIM-2)-containing integron, without detectable 5'-conserved segment, contains four genes cassettes (aacA7-bla(VIM-2)-dhfr-aacA5) and is ended by tniC. The bla(OXA-10)-containing integron includes a catB3 cassette and a fused gene cassette, which is made up of bla(OXA-17) and a novel streptomycin-spectinomycin gene, designated aadA15. The bla(OXA-17)-containing integron has three gene cassettes (aacA4-catB2-bla(OXA-17)) but the 59-base element of the bla(OXA-17) cassette is interrupted by a putative transposase gene. The bla(PSE-1)-containing integron has three gene cassettes, aacA4, an aadA3-related gene designated aadA3b and bla(PSE-1). PFGE revealed genetic diversity among the multidrug-resistant isolates from different hospitals.


CONCLUSIONS
This study demonstrated the high prevalence of VIM-type MBLs and the presence of unusual bla-encoding integrons in multidrug-resistant P. aeruginosa isolates in Taiwan. The spread of bla(VIM-2)-related genes by horizontal transfer might have occurred.
Yan
Jing-Jou
JJ
Department of Pathology, College of Medicine, National Cheng Kung University, Tainan, Taiwan.
Hsueh
Po-Ren
PR
Lu
Jang-Jih
JJ
Chang
Feng-Yee
FY
Ko
Wen-Chien
WC
Wu
Jiunn-Jong
JJ
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D004269:DNA, Bacterial / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial; D006801:Humans; D017403:In Situ Hybridization; D032023:Integrons / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D015995:Prevalence; D011552:Pseudomonas Infections / Q000453:epidemiology / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification; D013624:Taiwan / Q000453:epidemiology; D018440:beta-Lactam Resistance / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics*
D000900:Anti-Bacterial Agents; D017931:DNA Primers; D004269:DNA, Bacterial; D001618:beta-Lactamases