Analysis on the distribution and drug resistance features of anaerobes isolated from clinical infectious specimens

Abstract

Objective: To clarify distribution and drug resistance characteristics of anaerobes isolated from clinical infectious samples, and to provide experimental data for guiding on treatment of infections caused by anaerobes. Methods: The anaerobes, isolated from 1 057 different clinical specimens from inpatients admitted to the Affiliated Hospital of Inner Mongolia Medical University from March 2016 to November 2017, were identified by VITEK-2 anaerobes and corynebacterium (ANC) card and bacteroides fragilis isolates were further verified by 16S-rRNA sequencing. Meanwhile, broth dilution method was employed to detect the drug sensititities of bacteroides fragilis and PCR method was used to detect the carbapenem resistance gene cfiA. Results: Totally 303 strains of anaerobic bacteria were isolated, among which 199 strains were gram-negative bacteria, accounted for 65.68%. Among the gram negative anaerobes, bacteroides species were the most common, accounted for 35.64%, followed by prevotella spp., which accounted for 19.14%. B. fragilis were the most common among Bacteroides spp., accounted for 21.54%, followed by Prevotella bivia, accounted for 5.94%. The coincidence rate of 16S-rRNA sequencing results of Bacteroides fragilis and that of ANC card identification results was 100% (65/65). The drug resistance of B. fragilis to penicillin, clidamycin, ampicillin/sulbactam, amoxicillin/clavulanic, were 100%, 90.77%, 56.92% and 66.67%, respectively. The resitance rate of B. fragilis to chloramphenicol was the lowest, which was 1.54%.Moreover, the resistance rate of B. fragilis to imipenem and metronidazole were both higher, which were 38.46%(25/65) and 23.08%(15/65), respectively, and the positive rate of beta lactamase was 100% (65/65). The carrying rate of carbapenems resistance gene cfiA for 65 strains of Bacteroides fragilis was 52.3% (34/65), and 72.00%(18/25)for imipenem resistant strains. Conclusions: The obligate anaerobic bacteria are widely distributed in clinical specimens, and the great majority are gram negative anaerobic bacteria, and the most frequently isolated one is Bacteroides fragilis. Bacteroides fragilis isolates are found to be resistant to several kinds of common antibiotics, especially for imipenem and metronidazole, which should be given more attention to.