Molecular epidemiology and risk factors of Stenotrophomonas maltophilia infections in a Chinese teaching hospital

Abstract

Background: Stenotrophomonas maltophilia (S. maltophilia) is an important opportunistic pathogen obtained in hospitals. With the abuse of broad spectrum antibiotics and invasive surgical devices, the rate of S. maltophilia infections is increasing year by year. This study is aimed at epidemiological analysis of the clinical and molecular characteristics of S. maltophilia infections in a Chinese teaching hospital. We wish to have a comprehensive understanding of the status of S. maltophilia infections, in order to provide strong epidemiological data for the prevention and treatment of S. maltophilia infections. Results: 93 isolates from the Renji Hospital affiliated to Shanghai Jiaotong University School of Medicine were included, in which 62 strains were from male patients and 81 isolates were cultured from sputum samples. 86 patients had underlying diseases. All patients have received antibiotic therapeutics. MLST analysis indicated that 61 different sequence types (STs) were found (including 45 novel STs), and MLST did not show significantly adominant STs. PFGE showed weak genetic linkage between strains. The resistant rates of Trimethoprim/sulfamethoxazole (TMP/SMX) and levofloxacin were 9.7% and 4.3%. All the strains were susceptible to minocycline. The positive rates of the four virulence genes Stmpr1, Stmpr2, Smf-1 and Smlt3773 locus were 79.6%, 91.4%, 94.6% and 52.7%. The positive rates of the three biofilm genes rmlA, spgM and rpfF were 82.8%, 92.5% and 64.5%. The mean biofilm forming level of OD492 was 0.54 ± 0.49, and there was no significant difference between genders and among different age groups. The data from patients with ICU and the control group were analyzed retrospectively, and the risk factors infected in ICU included the hypoimmunity and the increase of the use of antibiotics were independent risk factors. Conclusion: Most of the patients had prior medical usage history and baseline diseases. The carrying rate of virulence genes was high, the drug resistance rate of S. maltophilia was low, and the biofilm formation ability was strong. The increased use of antibiotics is an independent risk factor for S. maltophilia infection, which should be payed more attention. No obvious clonal transmission was found in the same department.