Species distribution and antibiotic susceptibility of Nocardia isolates from Yantai, China

Abstract

Purpose: This study aimed to investigate the species distributions and drug sensitivities among 19 strains of Nocardia isolated from Yantai, China, from 2017 to 2019. Patients and methods: Definitive species identification was performed by sequencing a fragment of the 16S rRNA gene (1480 bp) and by matrix-assisted laser desorption/ ionization-time of flight mass spectrometry (MALDI-TOF MS). The susceptibilities of the isolates to 15 commonly-used antibiotics were tested using the microbroth dilution method. Results: Among the 19 Nocardia isolates, five species were confirmed. Seventeen of the 19 Nocardia spp. strains were identified consistently by the two methods, while two isolates of N. cyriacigeorgica were misidentified as N. otitidiscaviarum by MALDI-TOF MS. N. farcinica was the most common species (8/19), followed by N. cyriacigeorgica (6/19), N. otitidiscaviarum (2/19), N. brasiliensis (2/19), and N. nova (1/19). All isolates were susceptible to trimethoprim-sulfamethoxazole and amikacin, followed by linezolid and tigecycline (94.7% susceptibility rates). The sensitivity and minimum inhibitory concentration patterns for ciprofloxacin, moxifloxacin, clarithromycin, and tobramycin were significantly correlated with the species. Conclusion: These results regarding the distribution and antibiotic resistance features of Nocardia species further our understanding of the diversity of Nocardia species circulating in Yantai, China, and thus support the use of more accurate empirical treatments.