Nocardiosis in the Illawarra-Shoalhaven region from 2010 to 2019

Abstract

Nocardia species are a diverse group of gram-positive bacteria that are encountered as pathogens in clinical practice. They are ubiquitous environmental organisms classically causing opportunistic infections in immunocompromised individuals. This case series describes the epidemiological, microbiological and clinical features of 26 culture-proven cases of nocardiosis presenting to the public healthcare service in a regional area of New South Wales over a ten year period. These cases involved ten distinct species of Nocardia and appeared to demonstrate increasing incidence over time. The majority of Nocardia isolates (88%) were grown on conventional bacteriological media and speciation was primarily via 16S rRNA sequencing and/or matrix assisted laser desorption ionisation—time of flight mass spectrometry. Similar to other Australian Nocardia studies, the isolates seen in this case series were universally susceptible to trimethoprim-sulfamethoxazole. This was reflected in treatment data, with all but one patient receiving this agent as part of their antibiotic regimen. While similar case series have been reported from other Australian states, there are no published clinical studies of nocardiosis in New South Wales. Given the nature of Nocardia species as an environmental saprophyte, this study examined the association between incidence of nocardiosis and regional geographic or climatic variation but was unable to demonstrate a statistically significant correlation.