Song Jeong Hoon, Sung Ji Youn, Kwon Kye Chul, Park Jong Woo, Cho Hye Hyun, Shin So Yeon, Ko Young Hyun, Kim Ji Myung, Shin Kyeong Seob, Koo Sun Hoe
Department of Laboratory Medicine, Chungnam National University, Daejeon, Korea.
Korean J Lab Med. 2010 Jun;30(3):295-300. doi: 10.3343/kjlm.2010.30.3.295.
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.
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.
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.
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.
嗜麦芽窄食单胞菌是一种革兰氏阴性杆菌，是免疫功能低下患者的医院病原体。甲氧苄啶/磺胺甲恶唑（TMP/SMX）是治疗嗜麦芽窄食单胞菌感染的首选药物；然而，对TMP/SMX的耐药性正在增加。在本研究中，我们调查了TMP/SMX耐药性的发生率与sul基因和移动元件的存在之间的关系。
2007年4月至2009年4月期间，从3所大学医院收集了总共120株嗜麦芽窄食单胞菌分离株。采用纸片扩散法测定抗菌药物敏感性。进行PCR和DNA测序以检测sul1、sul2、1类整合子和ISCR2元件。进行基于重复外显子回文序列的PCR（REP-PCR）以评估遗传相关性。
TMP/SMX耐药（R）分离株中sul1基因和1类整合子的比例明显高于TMP/SMX敏感（S）分离株（P<0.001）。28株携带sul1的分离株中有17株也有1类整合子，但没有sul1的分离株中没有一株有1类整合子。1类整合子中鉴定出的基因盒包括aacA4、aadA1、aac6'-II和qac。120株分离株中均未携带sul2、glmM或ISCR2元件。REP-PCR未显示分离株之间有任何遗传相关性。
在韩国，嗜麦芽窄食单胞菌分离株对TMP/SMX的耐药性是由于1类整合子中的sul1而非sul2。1类整合子除了sul1外还含有多个抗生素耐药基因，因此它可以介导嗜麦芽窄食单胞菌的多药耐药性。
