Detection of the Smqnr quinolone protection gene and its prevalence in clinical isolates of Stenotrophomonas maltophilia in China

Abstract

The aim of this study was to detect novel variants of the Stenotrophomonas maltophilia Smqnr gene family and analyse the prevalence of Smqnr genes in clinical isolates of S. maltophilia in China. In total, 442 clinical isolates of S. maltophilia were collected from nine hospitals in four provinces in China. Antimicrobial susceptibility testing against six commonly used antibiotics was performed on these isolates. The sequences of the Smqnr genes amplified by PCR were aligned with those of known Smqnr genes in GenBank and an Smqnr database. The resistance rate against co-trimoxazole was highest at 48.6 %, followed by resistance rates against ceftazidime, chloramphenicol, ticarcillin/clavulanate and tigecycline at 28.7, 21.3, 19.0 and 16.1 %, respectively. The highest susceptibility was shown to levofloxacin, with a resistance rate of just 6.1 %. Smqnr genes were detected in 114 isolates, and comprised 11 previously identified genes and 20 new variants, bringing the total number of known Smqnr genes to 47. The 20 novel Smqnr genes were designated Smqnr28-47 and the encoded proteins showed only 1-12 amino acid differences among each other. The most common Smqnr genes in China were Smqnr8 and its variant Smqnr35 with prevalences of 17.5 % (20/114) and 13.2 % (15/114), respectively. Both the known and the novel Smqnr genes were discovered in both quinolone non-sensitive and sensitive isolates with similar frequency, suggesting that the Smqnr gene makes little contribution to quinolone resistance in this organism.

Smqnr VARIANTS IN CLINICAL ISOLATES OF Stenotrophomonas maltophilia IN BRAZIL

“…The qnr genes in S. maltophilia isolates have been studied by some authors 3 6 17 18 . In our study, among 13 isolates harboring Sm qnr ; two were resistant (MIC 8 and 16 mg/L) and two exhibited increased MIC to levofloxacin (MIC 4 mg/L) and eight isolates exhibited resistant to ciprofloxacin.…”

“…A recent study conducted in China, evaluated 442 clinical isolates of S. maltophilia from nine hospitals. The resistance against co-trimoxazole was 48.6%, and a high susceptibility was shown to levofloxacin, only 6.1% of strains were resistant to levofloxacin 18 . Sm qnr genes were detected in 114 (26%) isolates in similar frequency in both quinolones sensitive and nonsensitive strains.…”

“…Sm qnr genes were detected in 114 (26%) isolates in similar frequency in both quinolones sensitive and nonsensitive strains. Twenty new variants of Sm qnr genes were identified and called Sm qnr (28-47) 18 . An in vitro study, showed that overexpression of Sm qnr upon deletion increased modestly the MIC of nalidixic acid and moxifloxacin 3 .…”

A Monte Carlo pharmacokinetic/pharmacodynamic simulation to evaluate the efficacy of minocycline, tigecycline, moxifloxacin, and levofloxacin in the treatment of hospital-acquired pneumonia caused byStenotrophomonas maltophilia

“…However, resistance to SXT has increased in recent decades. The resistance rate is as high as 48.6% in some regions of China and even reaches 100% elsewhere [1,3]. The high resistance rate, plus frequent allergic reactions, intolerance, and other contraindications pose great challenges.…”

“…Hospital-acquired pneumonia (HAP) is the most common infection, followed by bacteremia in immunosuppressed or debilitated patients [1]. Because this bacillus shows high-level intrinsic resistance to most antibiotic classes (b-lactams, quinolones, aminoglycosides, tetracyclines) treatment choices are limited [1][2][3][4]. The mainstay therapy for infections caused by S. maltophilia has been trimethoprim/sulfamethoxazole (SXT) [1,2].…”