Epidemiology and Drug Resistance of Pulmonary Nocardiosis Among Tuberculosis-Suspected Patients in Guangzhou, China

Chunming Luo,1 Guimin Zou,1 Yigang Tan,2 Jialou Zhu,1 Xin Liu,1 Cairong Zou,1 Kun Li1 1State Key Laboratory of Respiratory Disease, Guangzhou Key Laboratory of Tuberculosis Research, Department of Medical Laboratory, Guangzhou Chest Hospital, Institute of Tuberculosis, Guangzhou Medical University, Guangdong, 510095, People’s Republic of China; 2State Key Laboratory of Respiratory Disease, Guangzhou Key Laboratory of Tuberculosis Research, Department of Tuberculosis Internal Medicine, Guangzhou Chest Hospital, Institute of Tuberculosis, Guangzhou Medical University, Guangdong, 510095, People’s Republic of ChinaCorrespondence: Kun Li, Email [email protected]: This study aimed to analyze the detection characteristics, species distribution, and drug susceptibility profiles of Nocardia isolates among tuberculosis-suspected patients in the Guangzhou region, thereby offering valuable insights for clinical diagnosis and treatment.Methods: This study included 77,550 clinical samples collected from tuberculosis-suspected patients. All specimens were cultured using the MGIT 960 liquid culture system. Culture-positive isolates underwent acid-fast staining, followed by Nocardia subculture purification and species identification using mass spectrometry. Subsequently, antimicrobial susceptibility testing was performed on 97 Nocardia clinical isolates against 13 antimicrobial agents.Results: Species identification revealed Nocardia farcinica as the predominant species, accounting for 95.36% of all isolates. Morphological analysis following cultivation showed that Nocardia farcinica exhibited partial acid-fast staining characteristics, with a light blue background and faint red or pink filamentous bacilli displaying definitive branching structures. These features clearly distinguished it from the cord-like arrangements typically observed in mycobacteria. Antimicrobial susceptibility testing demonstrated that co-trimoxazole, amikacin, moxifloxacin, and linezolid were reliable therapeutic options. In contrast, the tested β-lactams, macrolides, and tetracyclines exhibited high resistance rates, limiting their clinical utility.Conclusion: This study elucidates the epidemiological characteristics and antimicrobial susceptibility profiles of Nocardia infections in Guangzhou, providing valuable insights for early diagnosis and targeted therapy. Morphological analysis serves as an effective tool for reducing the risk of misdiagnosing Nocardia as mycobacteria. Future efforts should focus on optimizing detection methods and conducting multicenter studies to better understand prevalence trends and resistance mechanisms, ultimately improving clinical management.Keywords: Nocardia infections, antimicrobial susceptibility, tuberculosis, acid-fast morphology