High occurrence of antibiotic resistance and biofilm-formation among Stenotrophomonas maltophilia isolated from a tertiary hospital in Southwest of Iran

Abstract

IntroductionThe emergence of Stenotrophomonas maltophilia (S. maltophilia) causes of morbidity and mortality infections associated with hospitalized or compromised patients. The aim of this study was to evaluate the antimicrobial resistance patterns, biofilm formation ability as well as the clonal and genetic diversity among clinical isolates of S. maltophilia. Materials and methodsDuring 8-months period, 109 non-repetitive S. maltophilia isolates were obtained from a tertiary hospital in Shiraz, Iran. Minimum inhibitory concentrations (MICs) was performed by broth microdilution. To detect rmlA, rpfF, spgM, and smf-1 genes, polymerase chain reaction (PCR) was performed. Moreover, to evaluate biofilm-forming ability of the isolates, microtiter plate method was used. Finally, to determine clonal relatedness among isolates, ERIC-PCR was performed. ResultsAmong 109 clinical isolates, 92.7% of isolates were collected from blood samples. The highest susceptibility was against levofloxacin (100%) followed by minocycline (96.3%) and the most resistance rate was against TMP/SMX (54.1%). Among the genes associated with biofilm formation, rmlA, spgM, rpfF, and smf-1 were detected in 78.9, 86.2, 58.7, and 32.1% of isolates, respectively. Moreover, 52.3% of S. maltophilia isolates were able to produce strong biofilm. ERIC-PCR typing revealed that 103 isolates with biofilm formation ability were classified into 7 clusters. ConclusionIn conclusion, high occurrence of antibiotic resistance in S. maltophilia isolates seems to be alarming for the health care systems. Moreover, the most detection biofilm formation gene was spgM. This study revealed a high-level of biofilm formation. Also, a close relationship between the presence of rpfF gene and biofilm formation was observed. Thus, it is challenging for physicians to treat infections resulting from these resistant bacteria. Also, molecular typing of S. maltophilia showed that isolates were relatively heterogeneous.