Abstract
BackgroundWith the increase of detection rate and long treatment period, nocardiosis has become a noticeable problem in China. However, there are limited large-scale studies on the epidemiology and antimicrobial susceptibility profiles of clinical Nocardia spp. in China. The present study aimed to explore the species distribution and drug susceptibility pattern of 82 clinical Nocardia isolates from three tertiary hospitals in China by multilocus sequence analysis (MLSA) and broth microdilution (BMD) method.ResultsPulmonary nocardiosis (90.2%) was the most common clinical presentation of infection. N. cyriacigeorgica (n = 33; 40.2%) and N. farcinica (n = 20; 24.4%) were the most frequently encountered Nocardia species, followed by N. otitidiscaviarum (n = 7; 8.5%), N. abscessus (n = 5; 6.1%), N. asiatica (n = 4; 4.9%), and N. wallacei (n = 4; 4.9%). Trimethoprim/sulfamethoxazole (SXT) remained high activity against all Nocardia isolates (susceptibility rate: 98.8%). Linezolid and amikacin were also highly active; 100 and 95.1% of all isolates demonstrated susceptibility, respectively. Except for N. otitidiscaviarum, all the Nocardia isolates exhibited high susceptibility rates to imipenem. The resistance rates of all isolates to clarithromycin and ciprofloxacin were 92.7 and 73.2%, respectively, but the resistance rate of N. farcinica to ciprofloxacin was only 25%.ConclusionsThe clinically isolated Nocardia spp. had diverse antimicrobial susceptibility patterns, which were similar to the reports by other groups elsewhere, but some differences were also observed, mainly including imipenem and ciprofloxacin. According to this study, SXT still can be the first choice for empirical therapy due to the low resistance rate. Linezolid can be chosen when a patient is allergic to SXT, and amikacin and imipenem can be the choice in a combination regimen.
Highlights
With the increase of detection rate and long treatment period, nocardiosis has become a noticeable problem in China
Our recent work shows that three-locus multilocus sequence analysis (MLSA) for identification of clinical Nocardia species is superior to five-locus MLSA which leads to misidentification for N. abscessus confirmed by digital DNA-DNA hybridization [17]
A phylogenetic tree was constructed from the 1902-bp concatenated gyrB-16S rRNA-secA1 sequences of 23 Nocardia type strains and 82 clinical Nocardia isolates by the neighbor-joining method [22] and Kimura two-parameter distances [23]
Summary
With the increase of detection rate and long treatment period, nocardiosis has become a noticeable problem in China. There are limited large-scale studies on the epidemiology and antimicrobial susceptibility profiles of clinical Nocardia spp. in China. The present study aimed to explore the species distribution and drug susceptibility pattern of 82 clinical Nocardia isolates from three tertiary hospitals in China by multilocus sequence analysis (MLSA) and broth microdilution (BMD) method. The available database of MALDI-TOF MS is limited for Nocardia strains leading to some uncommon isolates with no or false identification [10, 11]. The 16S rRNA gene sequencing is generally considered as the primary means for accurate identification of the clinically encountered Nocardia isolates [12], but it cannot discriminate closely related species due to high conservation, unless it combines with a housekeeping gene, such as gyrB or rpoB [13]. The three-locus MLSA was carried out in this study to accurately identify clinical isolates from three tertiary care centers
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