Nocardia cyriacigeorgica is the most commonly linked to respiratory tract infections [3] - [12] but also from samples from several other sites [13] - [19] . Nocardia cyriacigeorgica typically causes infections in immunocompromised individuals and has been identified in clinical specimens worldwide. However, several case reports have also documented infections in immunocompetent patients [20] - [22] . Over the past year, nine cases of Nocardia cyriacigeorgica infection have been reported in PubMed. The cohort included seven men and two women, with six patients over the age of 50. Pulmonary nocardiosis was diagnosed in four cases, all of which occurred in immunosuppressed individuals. Regarding treatment, the majority of patients (78%) received trimethoprim-sulfamethoxazole (TMP-SMX) (see Table 1 ). There is no report of Nocardia species cross contaminations in human populations using immunosuppressive agents, suggesting that environmental exposure is the main cause of infection.

We present the case of a Nocardia cyriacigeorgica infection in an immunocompetent patient suffering from bronchiectasis and chronic obstructive pulmonary disease (COPD), who had no history of immunosuppressive agent use and signs of immunodeficiency. The isolation and identification of Nocardia cyriacigeorgica in routine diagnostic microbiology laboratories has been a complex and time-consuming process. However, with the advent of mass spectrometry techniques, such as matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), rapid and accurate identification has become increasingly feasible.

On August 1st, 2022, a 66-year-old female outpatient presented to the Eurofins LAMM laboratory in Lucca, located in the Tuscany region of Italy, with a diagnosis of bronchiectasis and a request for a sputum culture. Over the following days, the patient submitted two additional sputum samples, both of which confirmed the results from the initial sample.

The sputum cytology, using Papanicolaou staining, revealed a notable presence of polymorphonuclear leukocytes ( Figure 1 ). The culture, grown on blood agar, showed a high bacterial count (>100,000 CFU/mL) ( Figure 2 ) and microscopic examination of the colonies revealed Gram-positive beaded branching filaments. The positive samples were subsequently identified as Nocardia cyriacigeorgica through Matrix-Assisted Laser Desorption Ionization Time-Of-Flight (MALDI–TOF) mass spectrometry [32] .

Antimicrobial resistance was assessed using ETEST^® (Biomerieux), which utilizes a predefined gradient of 15 antimicrobial concentrations on a plastic strip. The results are detailed in Table 2 .

Following the laboratory diagnosis, the patient was admitted on September 15^th to the Pneumology Unit at the University Hospital of Pisa, where she performed a chest CT scan that revealed multiple bilaterally peribronchiectatic consolidations and signs of mucoid infarction of the small airways in a pattern of known diffuse cylindrical and cystic bronchiectasis ( Figure 3 ). Brain and abdomen MRI excluded further localizations of Nocardia. She received intravenous carbapenem (imipenem 500 mg every 6 hours with 3-hour extended infusion) and oral cotrimoxazole (3 vials in the morning + 3 vials in the afternoon + 4 vials in the evening for a total of 10 vials in a day). Therapy with cotrimoxazole was discontinued due to the occurrence of an adverse reaction, characterised by nausea and vomiting unresponsive to antiemetics and a diffuse erythematous-papular rash on the upper and lower limbs. The patient was subsequently treated for a total of about 4 weeks with intravenous imipenem and addition an oral antibiotic of the oxazolidine family, linezolide 600 mg b.i.d., with no adverse reactions. Meanwhile, the microbiological sputum culture’s results have turned negative. Upon discharge, she was prescribed an oral bactericidal antibiotic that belongs to the class of third-generation cephalosporines, cefexime 400 mg b.i.d., which she continued until May 2024 as a long-term therapy. Since then, the patient has remained free of Nocardia re-infection.

At times, the administration of antimicrobial treatment occurs before a precise diagnosis is made, which may result in some infections going undiagnosed. Clinicians should remain vigilant and consider the possibility of Nocardia infection when conventional empirical treatment fails. This approach will facilitate timely communication with microbiology laboratories to appropriately extend the culture duration, helping to prevent misdiagnosis.

Nocardia infection should be considered not only in immunocompromised patients, but also in immunocompetent hosts, especially if they have predisposing pulmonary conditions such as bronchiectasis and COPD.

When searching for “Nocardia cyriacigeorgica” on PubMed, out of 169 results, only three publications mention infections caused by this microorganism in Italian regions [33] - [35] . This likely indicates an underestimation of infections in these areas.

This clinical case presentation highlights how advanced laboratory techniques, such as mass spectrometry, have facilitated the identification of Nocardia cyriacigeorgica. Our report underlines the importance for healthcare providers to consider this microorganism as a potential cause of infection, even in immunocompetent patients, especially in those with predisposing conditions like bronchiectasis and COPD. We conclude by suggesting that Nocardia cyriacigeorgica may be emerging as a significant pathogen in Italy.

An informed consent for the publication of this case report was obtained from the patient.