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J Glob Antimicrob Resist. 2019 Aug 7. pii: S2213-7165(19)30162-6. doi: 10.1016/j.jgar.2019.06.018. [Epub ahead of print]

Antimicrobial susceptibility profiles and species distribution of medically relevant Nocardia species: Results from a large tertiary laboratory in Australia.

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Department of Microbiology, Singapore General Hospital, 20 College Road Singapore 169856, Singapore. Electronic address:
Clinical Mycology Reference Laboratory, Centre for Infectious Diseases and Microbiology Laboratory Services, ICMPR, New South Wales Health Pathology, Westmead Hospital, NSW, Australia; Centre for Infectious Diseases and Microbiology, University of Sydney, NSW, Australia.



There are limited surveillance studies on the epidemiology and resistance rates of Nocardia species in Australia, particularly in the jurisdiction of New South Wales. This study aimed to investigate the species distribution and antimicrobial susceptibility of a large number of contemporary (2011-2016) clinical Nocardia species referred to a large tertiary hospital in Sydney, Australia.


Two hundred and seventy Nocardia isolates identified to the species level by dual target gene sequencing were investigated. Susceptibility testing was performed using the Sensititre™ RAPMYCOI panel with the minimum inhibitory concentration and geometric mean obtained for each species and drug combination. The susceptibility profiles and species distribution were analysed.


The respiratory system is the most affected site of nocardiosis. N. nova complex was the most frequently isolated Nocardia species (n = 80, 29.6%) in this survey followed by N. cyriacigeorgica (n = 61, 22.6%), N. brasiliensis (n = 52, 19.3%) and N. farcinica (n = 38, 14.1%). Of the tested isolates, 9.3% and 59.3% displayed resistance to trimethoprim-sulfamethoxazole and imipenem respectively. N. farcinica accounted for the highest number of resistant strains to trimethoprim-sulfamethoxazole. High imipenem resistance in N. cyriacigeogica is atypical to its drug pattern but has been reported elsewhere. All tested isolates remained susceptible to linezolid with only 0.7% exhibiting resistance to amikacin.


Linezolid and amikacin remain as good empiric option for nocardiosis treatment. Routine susceptibility testing for Nocardia is advisable with the detection of sulphonamide resistance and atypical antibiograms in this study.


Australia; Medically-relevant Nocardia; Species distribution; Susceptibility


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