[Analysis of acquired resistance genes in Stenotrophomonas maltophilia].
BACKGROUND
Stenotrophomonas maltophilia is a gram-negative bacillus and a nosocomial pathogen in immunocompromised patients. Trimethoprim/sulfamethoxazole (TMP/SMX) is the drug of choice for treating S. maltophilia infection; however, resistance to TMP/SMX is increasing. In this study, we investigated the relationship between the incidence of TMP/SMX resistance and the presence of sul genes and mobile elements.


METHODS
A total of 120 S. maltophilia isolates were collected from 3 university hospitals between April 2007 and April 2009. Antimicrobial susceptibilities were determined using the disk diffusion method. PCR and DNA sequencing were conducted for the detection of sul1, sul2, class 1 integron, and ISCR2 element. Repetitive extragenic palindromic sequence-based PCR (REP-PCR) was carried out to evaluate the genetic relatedness.


RESULTS
The TMP/SMX-resistant (R) isolates harbored a significantly higher proportion of sul1 gene and class 1 integron than TMP/SMX-susceptible (S) isolates (P<0.001). Seventeen of 28 isolates with sul1 also had a class 1 integron, but none of the isolates without sul1 had a class 1 integron. The identified gene cassettes within class 1 integrons include aacA4, aadA1, aac6'-II, and qac. None of the 120 isolates carried sul2, glmM, or ISCR2 element. REP-PCR did not show any genetic relatedness among the isolates.


CONCLUSIONS
In Korea, the resistance of S. maltophilia isolates to TMP/SMX is due to sul1 within a class 1 integron rather than to sul2. The class 1 integron also harbors multiple antibiotic resistance genes in addition to sul1, and therefore it could mediate multidrug resistance in S. maltophilia.
Song
Jeong Hoon
JH
Department of Laboratory Medicine, Chungnam National University, Daejeon, Korea.
Sung
Ji Youn
JY
Kwon
Kye Chul
KC
Park
Jong Woo
JW
Cho
Hye Hyun
HH
Shin
So Yeon
SY
Ko
Young Hyun
YH
Kim
Ji Myung
JM
Shin
Kyeong Seob
KS
Koo
Sun Hoe
SH
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D052978:Disk Diffusion Antimicrobial Tests; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D006801:Humans; D032023:Integrons / Q000235:genetics; D016133:Polymerase Chain Reaction; D020615:Stenotrophomonas maltophilia / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; C491369:Sul2 protein, bacteria; D015662:Trimethoprim, Sulfamethoxazole Drug Combination