Study On The Species Distribution And Antimicrobial Susceptibility Of Clinical Nocardia Isolates In Hebei

Objective: To investigate the Species distribution and antimicrobial sensitivity of clinical Nocardia isolates of in Hebei.Methods:1.We collected 100 strains isolated from 15 hospitals in hebei province from 2016 to 2020 and retrospectively analysed the characteristics of the cases.2.Definitive species identification was performed by amplification a nd sequencing the 16 S rRNA gene and secA1 and by matrix-assisted laser desorption/ionization-time of flight mass spectrometry(MALDI-TOF MS).3.The susceptibilities of the 60 isolates to 12 antibiotics were tested using the microbroth dilution method.Results:1.100 Nocardia isolates were identified as N.cyriacigeorgica(40),N.farcinica(21),N.abscessus(10),N.otitidiscaviarum(9),N.brasilimsis(8),N.asiatica(4),N.puris(2),N.wallacei(2),N.nova(1),N.b eijingensis(1),N.transvalensis(1),N.terpenica(1)by sequencing successfully.Only 85 Nocardia isolates were identified successfully to the species level by MALDI-TOF MS,while four isolates of N.asiatica,three isolates of N.abscessus,two isolates of N.puris,two isolates of N.wallacei,one isolate of N.nova,one isolate of N.beijingensis,one isolate of N.transvalensis and one isolate of N.terpenica were identified unsuccessfully.2.Among the 100 Nocardia strains,the majority were isolated from respiratory specimens(73%)and secretion specimens(20%).The most commonly species isolated from respiratory sources were N.cyriacigeorgica(48%) and N.farcinica(15.1%);The most commonly species isolated from secretion sources were N.brasiliensis(25%)and N.farcinica(25%).3.The most sensitive antibiotics were linezolid,amikacin and trimethoprim/sulfamethoxazole,and the sensitivity rates were 100%,98.3% and 96.7%,respectively.Minocycline was the second,and the sensitivity rate was 76.7%.The sensitivity rates of amoxicillin clavulanate,imipenem and ceftriaxone were 58.3%,35% and 21.7%,respectively.The sensitivity rate of vancomycin was 0.The sensitivity rate of N.cyriacigeorgica to ceftriaxone was only 40%,and the resistance rate to imipenem was 90%,which was not consistent with the expected pattern of M62.M inocycline remained high susceptibility to tested strains.Conclusions:The clinical Nocardia isolates can be identified by mass spectrometry,supplemented by sequencing.The distribution of Nocardia species was different in different infected sites.Drug sensitivity varies greatly among different species,and drug sensitivity patterns are different in different regions.Therefore,appropriate drugs should be selected according to drug sensitivity.