• Aine O'Brien, Julie Hart, Ammie Higgins, Ian Arthur, Gar-Hing Lee, Michael Leung, Karina Kennedy, Susan Bradbury, Sarah Foster, Sanchia Warren, Tony M Korman, Iain J Abbott, Claire Heney, Cheryl Bletchley, Morgyn Warner, Nicholas Wells, Desley Wilson, Hemalatha Varadhan, Robert Stevens, Monica Lahra, Peter Newton, Michael Maley, Sebastian van Hal, and Paul R Ingram.
• Department of Infectious Diseases, Fiona Stanley Hospital, Perth, Western Australia, Australia.
• Intern Med J. 2024 Apr 1; 54 (4): 613619613-619.

BackgroundNocardia is a ubiquitous saprophyte capable of causing human disease. Disease is primarily respiratory or cutaneous, usually acquired via inhalation or inoculation. Under the influence of environmental and host factors, Nocardia incidence and species distribution demonstrate geographical variation.AimsTo examine for differences in Nocardia incidence within Western Australia (WA) and analyse species distribution in the context of prior published studies. To analyse antibiogram data from a nationwide passive antimicrobial resistance surveillance program.MethodsRetrospective extraction of laboratory data for Western Australian Nocardia isolates over a 21-year period. Analysis of Nocardia antimicrobial susceptibility testing data submitted to the Australian Passive Antimicrobial Resistance Surveillance (APAS) program between 2005 and 2022.ResultsNine hundred sixty WA isolates were identified, giving an annual incidence of 3.03 per 100 000 population with apparent latitudinal variation. The four most common species identified within WA and amongst APAS isolates were N. nova, N. cyriacigeorgica, N. brasiliensis and N. farcinica. APAS data demonstrated that all species exhibited high rates of susceptibility to linezolid (100%) and trimethoprim-sulfamethoxazole (98%). Amikacin (>90% susceptibility for all species except N. transvalensis) was the next most active parenteral agent, superior to both carbapenems and third-generation cephalosporins. Susceptibility to oral antimicrobials (other than linezolid) demonstrated significant interspecies variation.ConclusionsWe demonstrate geographical variation in the distribution of Nocardia incidence. Four species predominate in the Australian setting, and nationwide data confirm a high in vitro susceptibility to trimethoprim-sulphamethoxazole and linezolid, justifying their ongoing role as part of first-line empiric therapy.© 2023 Royal Australasian College of Physicians.

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