Association of sul genes and class 1 integron with trimethoprimsulfamethoxazole Resistance in Stenotrophomonas maltophilia clinical isolates in Zagazig University, Egypt
Background: Stenotrophomonas maltophilia (S.maltophilia) is an intrinsically drug resistant opportunistic pathogen associated with serious infections in humans. Acquired resistance to trimethoprim-sulfamethoxazole (SXT,co-trimoxazole), the main stay of therapy against S. maltophilia ,has made its treatment more problematic. Objectives: This work aimed to determine the occurrence of SXT resistance among S. maltophilia isolated from Zagazig University Hospitals in Egypt and to assess the association of sul genes and integron1 with SXT-resistant isolates.
Material and Methods: Thirty-two S.maltophilia isolates were identified in this study during the period from 2013 to 2015. Screening of SXT-resistant isolates was done by Kirby-Bauer method. Minimum inhibitory concentration(MIC) values for SXT were determined by agar dilution. S. maltophilia isolates were tested for the presence of sul1, sul2, sul3, and int 1 genes by multiplex polymerase chain reaction.
Results: Amongst the 32 S. maltophilia isolates, 12(37.5%) were resistant to SXT. All SXT-resistant isolates were found to harbor sul1 gene and integron1. One of these isolates had sul2 gene (1/12,8.3%). Meanwhile, sul3 gene was not detected in any of the SXT-resistant isolates. Only 2 of the 20 SXT-susceptible isolates was found to yield positive PCR results for sul1 gene, one of them gave positive result for class 1 Integron. The association of sul genes and Integrin1 with resistance to SXT had a statistically significant difference( P<0.0001). Conclusion: Our study indicated a high frequency of SXT resistance among clinical S.maltophilia isolates from Zagazig University Hospitals, in which sul genes and class 1 integron were found to have a major role.
Keywords: Stenotrophomonas maltophilia; Sulphamethoxazole-trimethoprim-resistant; Multiplex PCR; sul genes; Integron 1