CharaCteristiCs of Actinomyces spp . and nocArdiA spp . simulating neoplasia

Introduction: Actinomyces and Nocardia are filamentous bacteria that can simulate neoplastic diseases, mainly in lungs. Methods: A retrospective study based on the analysis of the medical records of five cases of actinomycosis and nocardiosis, which has been primarily misdiagnosed as lung cancer according to their radiographic findings. Cases were selected from a sample of 38 patients diagnosed with actinomycosis and 29 patients diagnosed with nocardiosis at the Mycology Laboratory of Irmandade de Misericórdia Santa Casa de Porto Alegre (state of Rio Grande do Sul, Brazil) between January 1977 to December 2012. The diagnosis was established by culture and histological examination. The literature was also critically reviewed. Results: We reported data of three cases of nocardiosis and two cases of actinomycosis that was primary diagnosed as lung cancer. The patients’ mean age was 50.6 (ranged from 43-63), four were male and 80% (4/5) of patients were immunocompetent. In more than 50% of patients, diagnosis and also treatment of lesions required surgical intervention. Conclusions: The complete knowledge of disease manifestations accelerates diagnosis and treatment and decreases unnecessary surgical interventions and morbidity and mortality rates, which are high in these infections.

Actinomyces spp.and Nocardia spp.belong to the group of bacteria in the order Actinomycetales.The main agent of actinomycosis is Actinomyces israelii 1 .Actinomycosis is a rare, chronic, and slowly progressive bacterial infection that induces suppurative and granulomatous inflammation 2 .It has been documented in all age groups, with higher incidence in middle-aged individuals and in men.It is not typically considered an opportunistic infection 3 .Administration of high-dose intravenous penicillin for a long period of time is the primary treatment 2 .Early diagnosis has better prognosis with a high likelihood of cure.
Nocardia spp.are common in the environment worldwide, and infection by these bacteria has been reported in all ages and races, being two to three times more common in men 4 .It occurs mainly in patients with a deficiency of local pulmonary defense or systemic immunosuppression 5,6 .Nocardia asteroides complex is considered the most common species associated with human disease 1 .Treatments for nocardisosis include surgical drainage and antimicrobial agents.Trimethoprim-sulfamethoxazole (TMP-SMX) is considered the therapy of choice, and combinations of TMP-SMX with aminoglycoside or carbapenem are recommended for 6 to 12 months for nocardial brain abscesses 5 .
Many infections can resemble neoplastic diseases clinically and radiologically 7 .These infections can cause lesions that combine chronicity, progression through anatomical barriers, and production of masses similar to those found in cancer Actinomyces and Nocardia patients.In the present study, we investigated and described clinical and laboratorial findings of patients with Actinomyces spp. or Nocardia spp.infections simulating lung neoplasm.We consider that better understanding of these infections improves early diagnosis and decreases misdiagnosis.

METHODS
This is a retrospective study based on the analysis of the medical record of five cases of actinomycosis and nocardiosis that have been primarily misdiagnosed as lung cancer according to their radiographic findings.Cases were selected from a sample of 38 patients diagnosed with actinomycosis and 29 patients diagnosed with nocardiosis at the Mycology Laboratory of Irmandade de Misericórdia Santa Casa de Porto Alegre (state of Rio Grande do Sul, Brazil) between January 1977 to December 2012.
The radiological criteria for inclusion in the study were the following: presence of multiple lesions with predominance of pulmonary lesions in the lower lobes or presence of a solid solitary lesion with homogeneous soft-tissue attenuation and without benign calcification or spiculated margins.
The sample was analyzed to obtain information regarding signs and symptoms, underlying disease, diagnostic evaluation, clinical and radiological features, treatment, and outcome.A microbiological diagnosis was established by histological examinations (Kinyoun, Ziehl-Neelsen, Gram-Brown-Brenn, Giemsa, and methenamine-silver stains) and culture (aerobic, anaerobic).

RESULTS
From a total sample of 38 patients diagnosed with actinomycosis and 29 with nocardiosis in a 35-year period, two cases of actinomycosis (5%, 2/38) and three of nocardiosis (10%, 3/29) were selected.All five cases had been primarily misdiagnosed as lung cancer.The age of the patients ranged from 43 to 63 years (median, 50 years), and four patients were male.The immune system was compromised in one patient with renal transplantation.Disseminated nocardiosis was reported in one immunocompetent patient.
All articles addressing the diagnosis of actinomycosis and nocardiosis were identified by a search on MEDLINE (National of Medicine, Bethesda, MD) database using terms such as Actinomyces, Nocardia, nocardiosis simulating neoplasia, actinomycosis simulating neoplasia, pulmonary actinomycosis, pulmonary nocardiosis, Nocardia brain abscess.This search was complemented by a manual search on Index Medicus and a cross-referencing of published articles.We included only cases of pulmonary infection simulating neoplasia that met the same criteria used to select our case series.We found 12 cases of actinomycosis and 6 cases of nocardisosis (table 1).

CASE 1
A 57-year-old male was admitted to the hospital complaining of chest pain for 2 months.On physical examination he presented with fever, cough, dyspnea, and dental caries.Chest X-ray showed signs of consolidation and fibroatelectasic retraction of the left upper lobe.The patient had a presumptive diagnosis of cancer and returned three months later, when a new radiograph revealed increased lung injury with small necrotic cavities.Transbronchial needle aspiration was performed, special stain using the Gram-Brown-Brenn method was positive for filamentous bacteria, and Kinyoun and Ziehl-Neelsen stain were negative for acid-fast bacteria .Actinomyces spp. was isolated from anaerobic culture.Treatment was initiated with penicillin G (24 million UI/day/2 weeks), continued with procaine penicillin (600,000 UI/12 hours/2 weeks), and finished with erythromycin (2 g/day/6 months).
After one-year follow-up he presented in good clinical condition.

CASE 2
A 46-year-old male, smoker, alcoholic, previously healthy, was treated for bronchopneumonia for a period of 3 months, without clinical improvement.He presented with systemic symptoms and signs of meningeal irritation and started therapy with dexamethasone 12 mg/day.After 40 days of steroid therapy, chest X-ray showed pulmonary nodules in the right axillary segment, suggesting malignancy.Pulmonary auscultation revealed diffuse tracheal stenosis.A transcutaneous fine needle aspiration showed chronic inflammation with mild interstitial fibrosis in the parenchyma and was negative for malignant cells.Abdominal ultrasound was normal.Brain computed tomography (CT) showed multiple nodular lesions with cortical involvement in the parietal lobes and in the posterior fossa.Open lung biopsy was performed of the middle lobe, revealing Gram-positive branched filaments.Additionally, Kinyoun stain was positive for acid-fast bacteria, and Nocardia was also isolated in culture.The patient started treatment with SMX-TMP, but he had clinical worsening and died one month after the diagnosis of nocardiosis.

CASE 3
A 44-year-old male presented with hemoptysis.This patient had a history of several hospitalizations for the same reason without a diagnosis.In addition, he complained of anorexia, asthenia, dyspnea, and left chest pain.A chest radiograph showed atelectasis of the left upper lobe and bronchial and lingular stenosis.The patient underwent left upper lobectomy.Microscopic examination of the lung tissue stained by Gram-Brown-Brenn and Kinyoun techniques revealed filamentous bacteria consistent with Nocardia spp.

CASE 4
A 43-year-old male, smoker, previously healthy, was admitted with symptoms of pneumonia (chest pain and weight loss of 12 kg).He had a history of pneumonia, treated with azithromycin, a year ago.Chest CT showed multilobulated lesion with soft tissue density and calcification in the left lower lobe (figures 1 and 2).Lung biopsy stained by hematoxyline and eosine (H&E) showed sulfur granules and Gram stain showed characteristic Gram-positive filamentous bacteria, and Actinomyces israelii grew in anaerobic culture.The treatment of choice would be penicillin  Actinomyces and Nocardia G in high doses (18 million to 24 million IU/day) for 2-6 weeks, then oral amoxicillin for 6-12 months 1,2 .

CASE 5
A 63-year-old female who had undergone renal transplantation presented with productive cough.A chest CT showed lesion in the right lower lobe, with a halo of ground-glass opacities and hilar lymphadenopathy (figure 3 and 4), suggestive of a neoplastic lesion.Laboratory analysis of lung biopsy showed Gram-positive filamentous bacteria, Kinyoun stain was positive for acid-fast bacteria, and Nocardia sp was also isolated in culture.SMX-TMP is currently accepted as the first-line treatment for nocardiosis.
Furthermore, the antimicrobial susceptibility of Nocardia sp to meropenem, amikacin and ceftriaxone has also been reported to be high 4,5 .

DISCUSSION
Actinomyces spp.bacteria are components of the oropharynx human microbiota, gastrointestinal tract, and female genital tract; they have low virulence, being unable to penetrate the intact mucosa 4,8 .Actinomycosis manifested clinically by combining chronicity, progression through anatomical barriers, and production of tumor-like lesions that mimics cancer 3 .The main clinical presentations are cervicofacial, abdominal-pelvic and thoracic 1,9 .
Pulmonary actinomycosis represents approximately 15% of the total burden of disease 3 .Thoracic involvement can be seen as a bronchopulmonary disease that produces chronic inflammation, fibrosis, and cavitation resulting in invasion and destruction of the surrounding structures [10][11][12] .Imaging tests usually reveal an area of persistent subsegmental consolidation or a mass that can cavitate 13 .It may invade the interlobar fissures, pleura, chest wall, soft tissue, and even bone and mediastinum 14 .In our review, 83% of cases have presented lesions in the form of masses/nodules, and 92% (11/12) of the cases of actinomycosis occurred in immunocompetent patients (table 1).
A case series from Korea 2 found that common clinical manifestations of actinomycosis are cough, hemoptysis, and sputum; moreover, consolidation is the predominant radiological feature on CT scan and the majority cases are initially diagnosed as lung cancer.In our cases, two cases (1 and 4) showed the importance of the differential diagnosis of lung cancer diseases and that late diagnosis and inadequate treatment lead to clinical worsening 15 .In case 1, the patient underwent the growth rate test, excluding neoplastic disease.This was based on the observation that benign lesions usually have doubling times of fewer than 30 days or greater than 450 days, and malignant lesions have doubling times between these values 16 .
Nocardia spp.are filamentous, branched, Grampositive, acid-fast resistant, aerobic bacteria that live freely in the soil, are ubiquitous in nature, and have a worldwide distribution 17 .The isolation of Nocardia spp. in patients should be carefully evaluated for the presence of disseminated disease, especially in immunocompromised hosts 1 .This condition often affects patients with leukemia, lymphoma, transplantation, AIDS, chronic lung disease (chronic obstructive pulmonary disease, asthma, sarcoidosis, and bronchiectasis) or using corticosteroids 5,6 .fragments.Colonial morphology, filamentation and fragmentation are extremely variable among clinical isolates.Aerial filaments distinguish the genus Nocardia from related nocardioform gram-positive bacteria (Rhodococcus, Gordona, Tsukamurella, Actinomadura, and Corynebacterium species) and mycobacteria 17 .

Nocardiosis occurs mainly by inhalation of bacterial
In pulmonary nocardiosis, chest radiographs demonstrated a variety of findings, such as lumbar infiltrate, cavitation, nodules, and pleural involvement 18 .The most common feature found on chest CT is consolidation, usually large and often with cavitation.Some patients have single or multiple cavitary lesions that may, giving a thick wall abscess, be crucial to differentiate from cancer 13,17 .A retrospective study carried out in China revealed that pulmonary disease was the most common presentation of nocardiosis (85.0%) and that the most frequent chest CT results were airspace opacities, multifocal nodules or masses 18 .Because of this variety of findings, sometimes nocardiosis can simulate neoplastic disease, which occurred in our cases 2, 3, 5, and one case published by our group 19 .
Disseminated nocardiosis is often a late-presenting and potentially life-threatening infection with a mortality rate of 7-44% in immunocompetent patients and greater than 85% in immunocompromised 17 .Approximately 50% of all cases of pulmonary nocardiosis will disseminate to other organs, usually the brain, through the blood stream 1,20 .Case 2 of our series and 83% of the cases of nocardiosis reported in literature (table 1) had brain involvement and worse prognosis.Nocardia spp.brain abscess is extremely rare 21,22 , accounting for about 2% of all bacterial abscesses, and the mortality rate of patients with this condition is three times higher than that of patients with other bacterial infections 23,24 .
The infections that simulated cancer described here occurred mostly in immunocompetent patients, and the lung was the main organ involved 25 .There are no secure distinguishing characteristics to differentiate infections from neoplasms.In patients with suspected Nocardia and Actinomyces infection, a definitive diagnosis usually depends on the detection of the organisms in smears or sections examined microscopically together with isolation and identification by microbiological culture.Many pathogenic Nocardia species organisms from clinical material are variably acid-fast on primary isolation, a property quickly lost in subcultured colonies.Compared to Mycobacterium species, they retain fuchsine less tenaciously, so the modified Kinyoun stain that decolorizes is best for demonstrating the variable and transient acid-fast property of Nocardia species 26 .Actinomyces species are blue with Giemsa stains, dark gray or black with the Grocott-Gomori methenamine-silver stain (GMS) and not acid-fast when stained by the Ziehl-Neelsen or Kinyoun method 5 .The importance of direct microscopic examination of stained preparations of clinical specimens in the diagnosis of Actinomyces infections cannot be overemphasized.However, this examination may provide a rapid and specific diagnosis of the patient's infection, and the information that it yields may critically influence the clinician's choice of initial antimicrobial therapy.
In summary, infections by Nocardia spp.and Actinomyces spp.may resemble neoplastic disease.The complete knowledge of disease manifestations accelerates diagnosis and treatment and decreases unnecessary surgical interventions and morbidity and mortality rates, which are high in these infections.

Figure 1 :
Figure 1: Computed tomography of the thorax showing a multilobulated lesion with soft tissue density and calcification in the left lower lobe.

Figure 3 :
Figure 3: Computed tomography of the thorax showing a lesion in the right lower lobe, with a halo of ground-glass opacities and hilar lymphadenopathy.

Figure 4 :
Figure 4: Reconstruction of a computed tomography (figure 3) in the coronal plane.

Table 1 :
Literature review of cases of actinomycosis and nocardiosis simulating lung cancer.