Korean J Lab Med.  2010 Jun;30(3):295-300. 10.3343/kjlm.2010.30.3.295.

Analysis of Acquired Resistance Genes in Stenotrophomonas maltophilia

• Song JH
• Sung JY
• Kwon KC
• Park JW
• Cho HH
• Shin SY
• Ko YH
• Kim JM
• Shin KS
• Koo SH

• KMID: 1781630
• DOI: http://doi.org/10.3343/kjlm.2010.30.3.295

Abstract

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.

Keyword

Stenotrophomonas maltophilia; Trimethoprim/sulfamethoxazole; sul1 gene; Class 1 integron

MeSH Terms

Anti-Bacterial Agents/*pharmacology
Bacterial Proteins/genetics
Carrier Proteins/genetics
DNA, Bacterial/genetics
Disk Diffusion Antimicrobial Tests
Drug Resistance, Multiple, Bacterial/genetics
Humans
Integrons/genetics
Polymerase Chain Reaction
Stenotrophomonas maltophilia/*drug effects/*genetics/isolation &purification
Trimethoprim-Sulfamethoxazole Combination/*pharmacology

Figure

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  Fig. 1. Repetitive extragenic palindromic-PCR (REP-PCR) fingerprints of S. maltophilia isolates. Lanes M1 are 1-kb DNA size markers.

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