Antibiotic susceptibilities, genotype profiles and biofilm forming abilities of clinical stenotrophomonas maltophilia strains

Nonfermentative, gram-negative bacilli Stenotrophomonas maltophilia is an opportunistic pathogen that is often isolated from respiratory system, urinary tract and wound infections. S. maltophilia, which usually leads to outbreaks in the intensive care units of hospitals, causes refractory infections as a result of its ability to form biofilms and natural resistance to many antibiotics. Trimethoprim-sulfamethoxazole (TMP-SXT) is the first choice for the treatment of S. maltophilia infections. However, in recent years, the resistance against this antibiotic has been raised slightly, and other treatment options or new antibiotics have been investigated. The aim of this study is to investigate and evaluate the antibiotic susceptibility, genotypic distribution and biofilm forming capacity of S. maltophilia isolates. In this study, 13 clinical S. maltophilia isolates which found to be intermediate susceptible or resistant to at least one antibiotic routinely tested were evaluated. The isolates were obtained from the Ege University Faculty of Medicine Medical Microbiology Department Bacteriology Laboratory culture collection in 2015. The susceptibility of these isolates to ciprofloxacin (CIP), levofloxacin (LEV) and moxifloxacin (MOK) antibiotics were investigated by microdilution method and the ability of biofilm formation was investigated by crystal violet method. The isolates were also molecularly typed by polymerase chain reaction (PCR) performed with M13 universal primers. According to the microdilution test results, CIP, LEV and MOK minimum inhibition concentration (MIC) ranges were found to be 2-32 µg/ml, 0,5-16 µg/ml, < 0,125-8 µg/ml, and the MIC50/MIC90 values were found to be 4-16 µg/ml; 2-8 µg/ml and 0,125-4 µg/ml, respectively. According to the data from the crystal violet test, two of the 13 isolates were determined as medium-level and the others strong-level biofilm producers. Molecular typing revealed three main groups and subgroups with clonally related. However, no common or distinctive profile was observed to facilitate classification according to the antibiotic susceptibility and biofilm formation characteristics of these groups. These findings regarding the sensitivity of the studies and data that isolates of S. maltophilia tend to generate high levels of biofilms resemble those in other studies conducted in Europe and Turkey. In conclusion, this study is thought to be an important source of data on resistance profile, spread, epidemiology and virulence properties of S. maltophilia. While investigating the presence of nosocomial opportunistic pathogens to prevent outbreaks in the hospital, it should be thought that S. maltophilia may also be a causative agent. Studies on epidemiology, virulence factors and resistance mechanisms related to S. maltophilia should be supported. Key words: Stenotrophomonas maltophilia; biofilm; antibiotic resistance; molecular typing