Egyptian Journal of Medical Microbiology Volume 26 / No.1 / January 2017 105-111 Egyptian Journal of Medical Microbiology 105 ORIGINAL ARTICLE Molecular Characterization of Trimethoprim Sulpha-methoxazole Resistant Stenotrophomonas maltophilia at Sohag University Hospital 1 Hameda Hassan Mohamed* , 1 Asmaa Mohamed Goda, 3 Ghada Abd El-Gaber 3 Department of Medical Microbiology and Immunology 1 , Anaethesia and Surgical Intensive Care 3. Sohag University ABSTRACT Key words: Molecular, Trimethoprim Sulpha- methoxazole, Stenotrophomonas maltophilia *Corresponding Author: Hameda Hassan Mohamed Department of Medical Microbiology and Immunology Email: dr_hd_66@yahoo.com ; Tel.: 01286663663 01015019536 Background: Stenotrophomonas maltophilia (S. maltophilia) is an opportunistic human pathogen that is intrinsically multidrug resistant causing serious infections in humans and its emerged resistance to trimethoprim-sulfamethoxazole (SXT) is worldwide reported. Objectives: This work aimed to determine the occurrence of SXT resistance among S. maltophilia isolated from Sohag University Hospitals and to assess the association of sul genes with SXT-resistant isolates. Methodology: This study carried during the period from December 2015 to November 2016 in the microbiology laboratory of Sohag University Hospital on 65 Stenotrophomonas maltophilia isolates collected from 380 inpatients samples admitted to the Intensive care units (ICUs) of Sohag university hospital through this period. Identification and antibiotic susceptibility of S. maltophilia was done by the Vitek- 2 colorimetric compact system (bioMérieux, France) then multiplex PCR was done to detect the presence of SUL1, SUL2, SUL3 genes in the isolates. Results: Among the 65 S. maltophilia isolates, 17(26.2%) were resistant to SXT. All SXT-resistant isolates were found to harbor sul1 gene (17/17, 100%), one of these isolates had sul2 gene (1/17,5.9%). Only 2 of the 48 SXT-susceptible isolates were found to yield positive PCR results for sul genes, one of them gave positive result for SUL1(1/48,2%) the other for SUL2 (1/48, 2%) genes. Meanwhile, sul3 gene was not detected in any of the isolates. Conclusions: Our study reported that S. maltophila is among the common causes of infections occurring in the ICUs of Sohag university hospital specially those of the respiratory tract. Presence of SXT resistance among clinical S. maltophilia isolates from Sohag University Hospital, in which sul1 gene was found to have a major role. Tigecycline and levofloxacin are the antimicrobials of choice for treatment of infections caused by S. maltophilia. INTRODUCTION Stenotrophomonas maltophilia is a glucose non fermentative Gram-negative aerobic motile bacillus, generally found in aquatic environments, which causes human disease in immunocompromised patients 1 , behind Pseudomonas aeruginosa and Acinetobacter baumannii, S. maltophilia is the third most common non-fermenting Gram-negative bacillus responsible for healthcare-associated infections 2 . The organism was first isolated in 1943 and named Bacterium bookeri. In 1961, it was reclassified as a member of the genus Pseudomonas, then Xanthomonas in 1983 and finally Stenotrophomonas in 1993 3 . It is an environmental multidrug resistant organism (MDRO) can survive on almost any aqueous surface forming biofilm and can colonize areas of the body without causing infection 4 . But, in immunocompromised, hospitalized patients, S. maltophilia can cause a wide range of serious infections, including nosocomial pneumonia, bacteremia, urinary tract infections, wound infections, skin and soft tissue infections, meningitis, and endocarditis 3 . The incidence of hospital-acquired S. maltophilia infections is increasing, and cases of community- acquired S. maltophilia have also been reported 6 . The risk for S. maltophilia infection is increased in ICU patients, patients with long hospital stay, HIV infection, cancer, cystic fibrosis, recent surgery, trauma, mechanical ventilation, and previous therapy with broad-spectrum antibiotics 7 . S. maltophilia has high level intrinsic resistance to many antibiotics because of its multidrug-efflux pumps and low outer membrane permeability 5 . In addition, it can acquire antibiotic resistance by horizontal transfer of resistance genes which carried on plasmids, transposons and Integrons making infections difficult to treat 8 . The World Health Organization classify S. maltophilia as one of the causative multidrug resistant organisms (MDROs) of infection in hospital settings 9 Trimethoprim/sulfamethoxazole (SXT, cotrimoxazole) is considered the first-line agent recommended for the treatment of S. maltophilia 7 .