Species Identification And Antibiotic Susceptibility Testing Of The Nocardia Genus: Advances And Clinical Challenges

Summary

This review summarizes key diagnostic methods for Nocardia species identification, recent advances in antimicrobial susceptibility testing, and clinical challenges and future research directions.

Abstract

The genus Nocardia comprises bacteria widely distributed in nature that can cause infections in both humans and animals. Due to their diverse clinical manifestations and prolonged culture time, infections are frequently misdiagnosed or overlooked. In recent years, advances in biological techniques have markedly improved molecular diagnostic methods, enabling more precise species identification. However, the increasing issue of antimicrobial resistance poses significant challenges for clinical management, particularly among immunocompromised patients, for whom treatment is more complex. Although multiple therapeutic agents are currently available, rising resistance rates highlight the critical importance of antibiotic susceptibility testing. This review discusses molecular identification methods for Nocardia species, including recent advances in 16S rRNA gene sequencing, multilocus sequence analysis (MLSA), matrix-assisted laser desorption ionization–time-of-flight mass spectrometry (MALDI-TOF MS), whole-genome sequencing (WGS), and metagenomic next-generation sequencing (mNGS). The advantages and limitations of each technique are explored, with particular emphasis on their applications in detecting antibiotic resistance. The review also examines the clinical implementation of these molecular technologies, highlighting their contributions to rapid Nocardia identification, improved diagnostic accuracy, and reduced misdiagnosis. Finally, current limitations and future research directions are discussed, with particular attention to challenges related to cost, sensitivity, and standardization.

Introduction

Nocardia spp. are Gram-positive, facultative anaerobic bacteria ubiquitously present in the environment¹. They have attracted increasing attention in recent years due to their ability to cause severe infections in high-risk populations, particularly in susceptible individuals²˒³. Such infections include pulmonary, central nervous system, and cutaneous (soft tissue) diseases¹. Because of their pathogenicity and heterogeneous clinical manifestations, diagnosing and treating Nocardia infections remains challenging¹. Importantly, s....