Clinical and microbiological characteristics of Nocardiosis including those caused by emerging Nocardia species in Taiwan, 1998–2008

Authors


Corresponding author and reprint requests: P.-R. Hsueh, Departments of Laboratory Medicine and Internal Medicine, National Taiwan University Hospital, No. 7 Chung-Shan South Road, Taipei 100, Taiwan
E-mail: hsporen@ntu.edu.tw

Abstract

Clin Microbiol Infect 2010; 16: 966–972

Abstract

The genus of Nocardia is rapidly expanding and the species distribution varies with different geographical locations. We retrospectively reviewed the laboratory records of the bacteriology laboratory at National Taiwan University Hospital from January 1998 to June 2008 to identify patients with nocardiosis. During the study period, 164 isolates of Nocardia spp. were identified from 134 patients but only 113 patients had Nocardia infection. Nocardia brasiliensis (n = 54) was the most common pathogen, followed by N. asteroides (n = 36), N. farcinica (n = 7), N. flavorosea (n = 4), N. otitidiscaviarum (n = 3), N. nova (n = 3), N. beijingensis (n = 2) and one each of N. puris, N. jinanensis and N. takedensis. The major types of infection were cutaneous infection (56.6%), pulmonary infection (33.6%) and disseminated infection (7.1%). Eighty-eight patients received sulfonamide-containing antibiotic and eight of 100 patients with available data on outcomes died during the episode of nocardiosis. In conclusion, the clinical and microbiological manifestations of Nocardiosis vary with the different Nocardia species. Accurate identification of the species is crucial to make the diagnosis.

Introduction

Members of the genus Nocardia are associated with the group of microorganisms known as the aerobic actinomycetes and belong specifically to the family Mycobacteriaceae. Nocardia are ubiquitous in the environment and can be found worldwide as saprophytic components in fresh and salt water, soil, dust, decaying vegetation, and decaying faecal deposits from animals [1]. They are Gram-positive and weakly acid-fast, branching bacteria whose hyphae are often fragmented to coccobacillary forms [2]. Nocardia species are facultative intracellular pathogens, and the pathogenesis of nocardiosis is complicated. Although a large number of species have been characterized both phenotypically and genotypically within the genus, the genotype remains greatly heterogeneous and continues to evolve [1]. Several species have been implicated in human infections, but the geographical prevalence of each may vary greatly throughout the world. Some species are more prevalent in geographical locations with a specific climate [1].

Nocardiosis is an uncommon bacterial infection with a wide variety of clinical manifestations in immunocompetent and immunocompromised patients. The number of cases reported in the literature is increasing. This might be due to an absolute increase in the number of immunocompromised patients but also to improvement in laboratory techniques to detect nocardiosis. Host resistance to nocardial infection depends on neutrophils in early lesions and then the cell-mediated immune response [1]. The most common predisposing factors to opportunistic Nocardia infections are long-term steroid usage, chronic obstructive pulmonary disease (COPD), neoplastic disease, and human immunodeficiency virus (HIV) infection [3,4]. Clinical manifestations of nocardiosis range from cutaneous infections caused by traumatic inoculation in normal hosts to severe pulmonary and central nervous system diseases in immunocompromised hosts.

The aim of this study was to assess the species distribution of Nocardia isolates based on the molecular methods in a teaching hospital over an 11-year period, and to investigate clinical manifestations, microbiological characteristics, response to treatment, and outcome of nocardiosis.

Materials and Methods

Patients and setting

This study was conducted at National Taiwan University Hospital (NTUH), a 2000-bed tertiary care centre in northern Taiwan. Patients with nocardial infection were identified by the Bacteriology Laboratory of NTUH from January 1998 to June 2008. The clinical charts of all patients included in this study were retrospectively reviewed. Information on age, gender, underlying immunocompromised conditions including history of immunosuppressant drug use, corticosteroid therapy, diabetes mellitus, COPD, chronic liver disease, chronic kidney disease, malignancy, organ transplantation, HIV infection, types of clinical specimen positive for Nocardia spp. and outcome were analysed.

Definitions

Disseminated nocardiosis was defined as the isolation of Nocardia species from specimens from two or more non-contiguous organs such as lungs, lymph node, skin, brain or blood. A diagnosis of pulmonary nocardiosis required at least one positive culture from respiratory samples, and the presence of clinical symptoms and a new lesion on chest xray film at admission. The respiratory samples included expectorated sputum, endotracheal aspiration, pleural effusion, bronchoalveolar lavage or lung tissue obtained from biopsy. Long-term steroid usage was defined as prescription of oral prednisolone at least 10 mg/day for > 2 months before the infection episode. Patients who had any one of bronchiectasis, COPD or pneumoconiosis with previous symptoms and compatible old lesions on chest xray films were categorized as having underlying chronic lung disease. Mortality was defined as death from all causes during the study episode of hospitalization.

Bacterial isolates

Identification of Nocardia species was based on positive Gram stain (Gram-positive branching, beaded, and filamentous bacilli) and positive modified acid-fast stain results, colonial morphotypes, and conventional biochemical reactions, including hydrolysis of casein, xanthine, hypoxanthine and tyrosine. All isolates of identified and unidentified Nocardia species, based on these conventional methods, were further identified or confirmed by 16S rRNA gene analysis [5]. Partial sequencing analysis of the 16SrRNA gene of the isolates was performed using primers Noc1 (5′-GCTTAACACATGCAAGTCG-3′) (positions 46–64, Escherichia coli numbering system) and Noc2 (5′-GAATTCCAGTCTCCCCTG-3′) (positions 663–680, E. coli numbering system) [5]. The sequences were compared with published sequences in the 16SrRNA database. The closest matches and GenBank accession number were obtained. For the isolates causing disseminated nocardiosis and unusual Nocardia species, susceptibility testing of the agents used in the patients with these infections was used. The agar dilution method was used for susceptibility testing, in accordance with the guidelines recommended by the NCCLS [6].

Results

Microbiological investigation

A total of 164 Nocardia isolates were identified from 134 patients during the 11 years. After reviewing the medical records of these patients, 113 patients were confirmed as having Nocardial infection. Of 113 episodes of nocardiosis, N. brasiliensis (n = 54) was the most common pathogen, followed by N. asteroides (n = 36), N. farcinica (n = 7), N.flavorosea (n = 4), N. otitidiscaviarum (n = 3), N. nova (n = 3), N. beijingensis (n = 2) and one each of N. puris, N. jinanensis and N. takedensis. One isolate was not available for further identification to species level (Table 1). Most of the pulmonary infections were caused by N. asteroides, but N. brasiliensis caused most of the cutaneous infections. Among patients with disseminated nocardiosis, N. asteroides was the most common pathogen, followed by N. farcinica.

Table 1. Clinical manifestations, microbiological characteristics and outcomes of 113 patients with nocardiosis
VariablesNo. (%) of all patients (n = 113)No. (%) of patients with pulmonary infection (n = 38)No. (%) of patients with cutaneous infection (n = 64)No. (%) of patients with disseminated infection (n = 8)
  1. * The isolate was not available for further identification to species level.

Age, years (mean ± SD)   55.8 ± 19.1   57.5 ± 17.2   54.5 ± 20.7   59.0 ± 17.3
Male:female   79:34   29:9   41:23   6:2
Underlying disease condition
 Diabetes mellitus17 (15.0)6 (15.8)8 (12.5)1 (14.3)
 Chronic kidney disease16 (14.2)5 (13.2)6 (9.4)4 (57.1)
 Autoimmune disease16 (14.2)7 (18.4)3 (4.7)2 (28.6)
 Solid cancer12 (10.6)4 (10.5)4 (6.3)3 (42.9)
 Chronic lung disease11 (9.7)10 (26.3)0 (0.0)1 (14.3)
 Chronic liver disease10 (8.8)2 (5.3)6 (9.4)0 (0.0)
 Transplant recipient10 (8.8)4 (10.5)3 (4.7)2 (28.6)
 Haematological cancer7 (6.2)3 (7.9)3 (4.7)0 (0.0)
 Thyroid dysfunction5 (4.4)1 (2.6)4 (6.3)0 (0.0)
 AIDS3 (2.7)1 (2.6)2 (3.1)0 (0.0)
Receiving immunosuppressant14 (12.4)5 (13.2)5 (7.8)2 (28.6)
Receiving steroid23 (20.4)11 (28.9)6 (9.4)2 (28.6)
Mortality8/100 (8.0)5/36 (13.9)1/52 (1.9)2/8 (25.0)
Nocardia spp.
 N. brasiliensis 54 (47.8)2 (5.3)52 (81.3)0 (0.0)
 N. asteroides 36 (31.8)22 (57.9)7 (10.9)5 (62.5)
 N. farcinica 7 (6.3)3 (7.9)0 (0.0)3 (37.5)
 N. flavorosea 4 (3.5)3 (7.9)1 (1.6)0 (0.0)
 N. otitidiscaviarum 3 (2.7)2 (5.3)1 (1.6)0 (0.0)
 N. nova 3 (2.7)3 (7.9)0 (0.0)0 (0.0)
 N. beijingensis 2 (1.8)2 (5.3)0 (0.0)0 (0.0)
 N. puris 1 (0.9)1 (2.6)0 (0.0)0 (0.0)
 N. jinanensis 1 (0.9)0 (0.0)1 (1.6)0 (0.0)
 N. takedensis 1 (0.9)0 (0.0)1 (1.6)0 (0.0)
 Nocardia sp.*1 (0.9)0 (0.0)1 (1.6)0 (0.0)

Clinical features

The demographical and clinical data of patients and the annual numbers of nocardiosis cases are summarized in Table 1 and Fig. 1, respectively. Primary cutaneous Nocardia infection was the most common presentation in 64 (56.6%) patients. Nocardia caused pulmonary infection in 38 (33.6%) patients, disseminated infection in eight (7.1%) brain abscess in two (1.8%) patients and one patient with acute mastoiditis. The clinical characteristics of the eight patients with disseminated nocardiosis are summarized in Table 2.

Figure 1.

 The annual number of nocardiosis cases from January 1998 to June 2008 according to species of Nocardia (a) and types of infections (b).

Table 2. Summary of clinical characteristics and outcome of eight patients with disseminated nocardial infection
No. (year)Age years/sexUnderlying diseases or conditionSites of infection Nocardia speciesGenBank (accession no.)Specimens of isolateAntimicrobial therapy (MIC, μg/mL)Outcome
  1. AM, amikacin; MEP, meropenem; MIN, minocycline; SXT, trimethoprim-sulfamethoxazole; TZP, piperacillin/tazobactam.

1. (2000)31/FRenal transplant, SLE, Immunosuppressant, and steroid therapyLung, brain N. asteroides  Sputum, brainSXT (2)Survived
2. (2001)72/MChronic obstructive pulmonary diseaseLung, brain N. asteroides  Lung aspirateSXT (8), MINSurvived
3. (2001)61/MChronic kidney disease, renal transplant, immunosuppressant treatmentLung, Lymph node N. asteroides  Sputum, neck lymph nodeSXT (4)Survived
4. (2003)68/FDiabetes mellitus, chronic kidney diseaseLung, brain N. asteroides  Sputum, lung aspirateCefpime + AM (0.25), SXT (4)Survived
5. (2003)70/MGastric cancerLung, brain N. asteroides  SputumCefpime + AM (1), SXT (64)Survived
6. (2004)68/MESRD, ITP with splenectomy, colon cancer, steroid therapyLung, brain N. farcinica EU417670.1Sputum, bloodMEP (4) + SXT (4); SXT(4)Survived
7. (2004)32/MOral cavity cancerLung, blood N. farcinica EU417670.1Sputum, bloodMEP (4), SXT (4)Died (1 month after diagnosis)
8. (2007)70/MBronchiectasis, Sjögren’s disease, steroid therapyLung, blood N. farcinica EU417670.1Sputum, bloodTZPDied (2 days after diagnosis)

All of these patients had pulmonary involvement and five of them had brain abscesses. The MICs of trimethoprim/sulfamethoxazole against seven isolates varied, ranging from 2 to 64μg/dL, whereas amikacin had the lowest MICs of 0.25 and 1 μg/mL against two isolates. Seven of the eight patients received sulfonamide-based therapy and two patients died during the episode of disseminated nocardial infection.

The clinical and microbiological features of 15 cases of nocardiosis caused by the unusual Nocardia species, including N. otitidiscaviarum, N. jinanensis, N. flavorosea, N. takedensis, N. nova, N. beijingensis and N. puris are summarized in Table 3. All of the 15 pathogens from these cases were identified by conventional methods and by 16S rRNA gene analysis. Nocardia flavorosea caused pulmonary infection in three immunocompromised patients and cellulitis in one immunocompetent patient with tattoo wound. Nocardia nova caused pneumonia in two heart transplant recipients and empyema thoracis in one patient with autoimmune disease who was receiving steroid therapy. A gardener with a history of exposure to soil had cellulitis caused by N. jinanensis. One diabetic patient had N. takdensis cellulitis, but she did not recall any recent insect bite, injury or wound and denied any exposure to a soil environment. Only one fatal case of acute respiratory failure was caused by N. puris. Trimethoprim/sulfamethoxazole showed good in vitro activities against most of these unusual isolates, except N. otitidiscaviarum (MICs of 16 mg/L). MIC of N. puris isolate to imipenem was 1 mg/L.

Table 3. Summary of clinical characteristics and outcomes of 15 patients with nocardiosis caused by unusual Nocardia species
No. of patient (year)Age (years)/ sexUnderlying diseases or condition Nocardia speciesGenBank (accession no.)Clinical diagnosisSite of isolateAntimicrobial therapy (MIC, μg/mL)Outcome
 1. (1999)73/MNil N. jinanensis DQ462650.1 CellulitisSkin pusSXT (4)Improved
 2. (1999)29/MAIDS N. flavorosea EU841599.1 PneumoniaSputumSXT (4)Improved
 3. (1999)68/FChronic kidney disease, diabetes mellitus N. takedensis AB156277.1 CellulitsSkin pusSXT (4)Improved
 4. (2000)58/MHeart transplant, immunosuppressant therapy N. nova DQ840026.1 Pulmonary infectionLung aspirateSXT (8)Improved
 5. (2001)64/MHeart transplant immunosuppressant therapy N. nova DQ840026.1 Pulmonary infectionLung biopsySXTImproved
 6. (2002)66/MAutoimmune haemolytic anaemia, steroid therapy, chronic hepatitis C, diabetes mellitus N. nova DQ840026.1 EmpyemaPleural effusionSXT + CIP + VATS decorticationImproved
 7. (2003)21/MImmunosuppressant therapy, dermatomyositis N. beijingensis DQ659901.1 PneumoniaSputumSXT (4)Improved
 8. (2004)75/FBronchiectasis N. beijingensis DQ659901.1 Pulmonary infectionSputumSXT (4)Improved
 9. (2004)81/MIdiopathic pulmonary fibrosis, steroid therapy N. puris AB097455.1 Pulmonary infectionEndotracheal aspirateImipenem (1)Died
10. (2005)51/MNil N. otitidiscaviarum DQ659912.1 Pulmonary infectionBronchial washing and sputumSXT (16)Improved
11. (2005)34/FTattoo wound N. flavorosea EU841599.1CellulitisSkin pusSXT (4)Improved
12. (2005)63/MSteroid therapy, chronic kidney disease N. flavorosea EU841599.1 Pulmonary infectionLung aspirateSXT (4)Improved
13. (2006)89/MLung cancer, chronic pulmonary obstructive disease N. otitidiscaviarum DQ659912.1 Pulmonary infectionBronchial washing and sputumSXT (16)Died
14. (2007)79/MNil N. otitidiscaviarum DQ659912.1 Cutaneous infectionSkin pusUnknownUnknown
15. (2008)84/MChronic myelogenous leukaemia, chronic pulmonary obstructive disease, steroid therapy N. flavorosea EU841599.1 Pulmonary infectionSputumSXT (4)Improved

Brain involvement

A total of 28 patients underwent either computed tomography (CT) or brain magnetic resonance imaging (MRI) in this series. Among them, four patients had positive brain image findings with multiple brain abscesses and another three patients had a solitary brain abscess. The temporal lobe was the most common site of involvement, followed by the frontal lobe. Neurological symptoms, including unilateral weakness, vertigo and incoherent speech, presented in only four patients.

Treatment and outcomes

Eighty-eight patients a received sulfonamide-containing antibiotic and 13 received combined medical and surgical treatment. Medical records adequate to determine outcome were available in 100 of 113 patients.

The crude mortality rate was 8.0% (8/100), and was lowest for primary cutaneous infection (1.9%) and highest for disseminated disease (25.0%).

Discussion

Nocardia are slow-growing organisms that are found extensively worldwide, and the genus Nocardia is rapidly expanding, with at least 80 species described (http://www.bacterio.cict.fr/n/nocardia.html) to date. Nocardia asteroides is the most common Nocardia species associated with human disease [7,8]; however, some Nocardia species are more prevalent in geographical locations with a specific climate. For instance, N. brasiliensis is associated with tropical environments and often observed in the southern USA [9–11]. Nocardia farcinica has been reported more frequently in western European countries [12,13]. This study of 113 patients was performed in a subtropical area where N. brasiliensis is the most common nocardial pathogen, followed by N. asteroides and N. farcinica. Previous studies [1,14–16] showed that pulmonary nocardiosis is the most common nocardial disease, especially in immunocompromised hosts. However, during the 11-year period of this survey, we found that primary cutaneous nocardiosis was the most common presentation of all Nocardia infections, followed by pulmonary involvement. These differences among study findings could be entirely due to geographical variations in Nocardia spp. distribution. Nocardia brasiliensis was the most common pathogen in this study and the majority of primary cutaneous nocardiosis cases were caused by N. brasiliensis.

Identification of clinical isolates beyond the genus level is important since Nocardia species differ in the clinical spectrum of the disease they cause and their susceptibility to antibiotics [17]. After presumptive identification, final determination is now accomplished in reference labs using molecular techniques, such as 16S rRNA sequence analysis. This study reports the first isolates of N. flavorosea, N. nova, N. puris, N. beijingensis, N.  jinanesis and N. takedensis from Taiwan, and these rare strains caused pulmonary and cutaneous infections in 15 patients.

Nocardia flavorosea was originally isolated from soil by Chun et al. in 1998 [18]. To the best of our knowledge, this is the first reported case series of human infection with N. flavorosea. It caused nocardiosis in three immunocompromised patients with pulmonary infection and another immunocompetent woman with tattoo wound infection. Though optimal therapy for N. flavorosea infection has not been established, all four patients responded well to sulfonamide treatment. Nocardia jinanensis, a novel species, was first isolated from soil samples [19], but its clinical significance was unknown. Here we report the first case of N. jinanensis cellulitis in a gardener, who was thought to be infected because of soil contact. In 2003, a new species of Nocardia, N. puris, was described and isolated from a human abscess in Germany [20]. Three years later in Japan, the second strain of N. puris was isolated from an 81-year-old man with choroiditis [21]. Here, we report the third case of N. puris, which was recovered from endotracheal aspirates and caused a fatal pneumonia in a patient receiving steroids. Nocardia takedensis was recently isolated from a sediment sample taken from the moat surrounding Takeda Shrine and only one case of human infection, without a detailed clinical description, has been reported, by Watanabe et al. [22]. We report the second case of human infection by N. takedensis, which was isolated from a biopsy of foot tissue. The portal of entry of the organism in our patient was not easily clarified because of the absence of any recent contact history or environmental conditions suitable for propagation of the organism. We supposed that the organism might have gained access via a contaminated trivial cutaneous lesion. Our results are consistent with previous reports [22,23] that N. nova can cause opportunistic infection in transplant recipients and cancer patients, but thoracic empyema due to N. nova has never been reported.

Our report suggests that the clinical manifestations of N. nova are protean among severely immunocompromised patients. Wang et al. [24] first isolated N. beijingensis from soil in China in 2001 and Kageyama et al. [25] reported this new species in human infectious samples in 2004. Here, we report two cases of pulmonary infection due to N. beijingensis, and both patients improved after treatment with trimethoprim/sulfamethoxazole. However, it is believed that some of these unusual Nocardia species are widely distributed in South-East Asia, including China and Japan [21]. Therefore, diseases caused by these microorganisms may be underreported. Because of the diversity of Nocardia species, accurate identification is imperative before proper treatment can be determined. Studies of more clinical isolates are needed to decipher the spectrum of clinical diseases caused by these rare pathogens.

Disseminated nocardiosis has been rarely reported [14–16,26,27]; eight cases were identified in our study. In most of these cases the patients were immunocompromised and the infections were caused by N.  asteroides. All of these cases had pulmonary involvement, which, not surprisingly, accounted for the origin of the dissemination. Although five patients had brain abscesses, three patients did not have a focal neurological or meningeal sign. Although disseminated nocardiosis is supposed to occur via haematogenous spread, only two patients had a blood culture positive for Nocardia. All eight patients received trimethoprim/sulfamethoxazole-based therapy, and only two cases with nocardial bacteraemia died, despite the wide range of MICs of trimethoprim/sulfamethoxazole in the in vitro study. Further clinical studies are needed to establish the relationship between in vitro susceptibility and in vivo results. Furthermore, our findings suggest the importance of brain imaging and blood culture for the diagnosis of disseminated nocardiosis, especially in immunocompromised patients.

In this study, isolated brain abscess was found in two patients; one of these infections was caused by N. farcinica and the other by N. asteroides. Five of the eight patients with disseminated infection had brain involvement. In fact, 28 patients had previously undergone brain CT or MRI when pulmonary nocardial infection was diagnosed. Among them, four patients had neurological symptoms but another three patients with nocardial brain abscess did not have any neurological deficits. These findings suggest that brain imaging should be performed routinely in patients with pulmonary nocardiosis to detect possible brain abscess even in asymptomatic patients.

Acute mastoiditis is an uncommon complication of otitis media and is rarely caused by Nocardia spp. [28,29]. Most of the reported cases of acute mastoiditis [28,29] occurred in immunocompromised patients. One patient in this study, a 37-year-old man with nasopharyngeal carcinoma who had received concurrent chemo-radiotherapy, developed N. asteroids-related acute mastoiditis. The infection was cured by trimethoprim/sulfamethoxazole monotherapy. Although this clinical entity is extremely rare, it may have a fatal outcome by evolving into a brain abscess [28].

In conclusion, nocardiosis is not rare in Taiwan. It is a protean disease that manifests with different clinical and microbiological features depending on the infecting Nocardia species. Therefore, accurate identification of Nocardia species using molecular techniques is important to make the diagnosis and to elucidate the epidemiology. Fortunately, our findings indicate that a sulfa-containing regimen remains effective in treating nocardial infection.

Transparency Declaration

All authors declare no conflicts of interest.

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