Nocardia asteroides
Introduction
Nocardia asteroides is a gram-positive BACTERIA, partially acid-fast, soil-born aerobic actinomycete that causes both localized and disseminated infection. Edmund Nocard first described Nocardia infection in 1888. Nocard originally isolated the organism on the island of Guadeloupe and named it Streptothrix farcinica from cattle afflicted with "bovine farcy." Cattle with bovine farcy developed a granulomatous disease with multiple abscesses, draining sinuses, pulmonary involvement, and emaciation leading to death. Within 2 years of Nocard, Eppinger described the first human case as a pseudotuberculosis syndrome with pulmonary disease and cerebral abscesses and renamed the organism Cladothrix asteroids. The organism was subsequently renamed Nocardia asteroides by Blanchard in 1896. Currently, numerous subgroups of Nocardia have been classified. The two that account for a vast majority of the human disease seen are N asteroides and N braziliensis. Nocardia asteroides accounts for 86% of systemic nocardiosis in humans, 98% of cerebral nocardial abscesses, and approximately 2% of all cerebral abscesses.
The direct examination of an optimal clinical specimen is of paramount importance in demonstrating the presence of Nocardia. Specimens frequently include sputum,
bronchoalveolar washes or lavage, lung biopsy or abscess fluid. If granules are obvious in the specimen, they should be selectively removed and examined. Gram stains demonstrate complex gram-positive branched bacilli. The branching is at right angles
and extensive, especially in purulent portions of the specimen. The tips of the long filaments break into coccoid forms. When this morphology is observed in a direct Gram stain or from a Gram stain of a primary culture isolate, the next test to be performed
should be a modified acid fast stain. Frequently but not always, a clinical specimen will demonstrate partial or weak acid fastness. The Gram stain and acid fast stain interpretation may critically influence the choice of initial antimicrobial therapy.
Nocardia can be isolated from media for routine bacteria, fungi, and mycobacteria. Specimens requesting Nocardia should be planted to blood agar held for seven days, SDA, BHI agar, and LJ or 7H10. BCYE or selective BCYE will support the growth
of Nocardia from potentially contaminated specimens such as sputum. Optimum recovery necessitates holding selective media for four weeks since these organisms grow slowly. Classical identification includes modified acid fast stain (best done from LJ or 7H10 media), presence of aerial hyphae, positive catalase test, growth in lysozyme, degradation of casein, xanthine, hypoxanthine, adenine, or tyrosine, reaction to acetamide
and arylsulfatase. Colony color may be white, tan, orange or salmon pink. Newer molecular techniques have shortened the time period and improved the accuracy of identification. These include PCR-based methods, DNA hybridization, and 16S
rRNA sequencing. A recently described algorithm by Kiska, et al. identifies Nocardia to species level utilizing reactions in API 20C AUX, several biochemicals and susceptibility results to five antibiotics. This approach provides accurate and timely identification of Nocardia species within one week of isolation.
Habitat / Distribution
N. asteroides is also involved in the saprophytic digestion and recycling of plant material in natural environments. It is in the soil and in dust particles. The primary reservoir of N. asteroides is thought to be the soil, but this organism can also be found in lake and marine sediments. However, there is little published information on the genetic diversity of N. asteroides strains associated with these natural habitats.
Identification / Characteristics (physical, morphology, nutrition)
Identification
Thirty-eight of 71 laboratories (53%) correctly identified this organism to genus level, and 16 identified to species level (23%); both identifications received excellent grades. Acceptable responses included: query Nocardia, and Gram positive, branching bacilli, partially acid-fast, filamentous, bacilli that fragment; common in soil, glabrous, heaped and folded, and white, pink, red, orange, or tan in color The 5 laboratories that reported "Gram positive bacilli" received unacceptable grades, because this response is too vague to provide useful clinical information.
Identification using Yeast killer system
Current methods of identification of Nocardia species, such as pattern of decomposition
of particular substrates or acid production from all carbohydrates except rhamnose, are unable to distinguish between these three species (i.e., N. asteroides, N. farcinica, and
N. nova). Because of their similarity, they were considered members of the N. asteroides complex.
However, their epidemiological, pathogenic, and antibiotic susceptibility patterns seem different and could lead to distinct management of infected patients and
clinical outcome. It is, therefore, important to evaluate an easy and quick method to differentiate between species of the N. asteroides complex.
It was proved that the killer phenomenon, which is a secretion process of extracellular (glyco) proteins (killer toxins) by self-immune killer yeasts, was widespread among microorganisms. After a promising study that provided differentiation of strains belonging to the N. asteroides complex, Nocardia brasiliensis, and Nocardia otitidiscaviarum, we decided to evaluate this system in its ability to separate species
of the N. asteroides complex.
Identification of Nocardia asteroids and Nocardia farcinica
by the killer yeasts P. mrakii K9
Characteristics
Nocardia is a common saprophyte in the soil and water. This organism does not commonly colonize the upper respiratory tract, therefore when the organism is isolated it should be considered a pathogen. Nocardia asteroides is the causative organism for 80% of nocardiosis in humans. Nocardia brasiliensis may occur in patients with normal immunity, but it is more often (up to 70%) recovered from patients immunosuppressed by cancer or transplant medication, or underlying systemic diseases such as AIDS. Normal hosts may present with mild chronic respiratory tract symptoms, however, frequently there is a cough, purulent sputum (sometimes blood streaked), pleural pain and night sweats. After the initial infection, the organism has a tendency to disseminate, especially in severely immunocompromised patients. The central nervous system is involved in 30% of cases while the subcutaneous may be involved in up to 15%. Nocardia should be considered in any pneumonia that is chronic and persists despite conventional antimicrobial therapy.
Nocardia, Rhodococcus, and rapidly growing mycobacteria can grow on many routine media, usually within 3 days, can survive mycobacterial concentration procedures, including sodium hydroxide methods, and grow on Lowenstein-Jensen media and 7H10 (oleic-acid-albumen agar). However, there are some Nocardia that may take one week or more to develop. The typical glabrous, pigmented orange colonies of Nocardia may resemble those of rapidly growing mycobacteria. Rhodococcus are usually cream coloured but some can be pink. In questionable cases, use of compound (plate microscope) to identify presence of aerial hyphae typical of the actinomycetes can assist to identify Nocardia.
In an ordinary Gram stain of the sputum, Nocardia appear as branched, beaded filaments and coccoid cells. A Gram stain from the primary plate is an important part of a work-up of any slow growing micro-organism. A Gram stain of a fresh culture of Nocardia shows Gram positive branching filaments (less than 1 m m. in diameter). Old colonies fragment into bacillary and coccoid forms. A Gram stain of an old culture has predominantly coccoid forms that could resemble staphylococci to the unwary. When you see branching Gram positive bacilli, it is important to transmit this information to the clinician as this is consistent with the actinomycetes group, and this information will aid in the focus of diagnosis and treatment. When Gram positive branching bacilli are identified in a Gram stain of clinical material like sputum or from a stain of primary culture the next test to be performed should be a modified acid fast.
Nocardia are weakly acid fast, and can be stained using a modified acid fast stain. Primarily acid fast stains are used in bacteriology for the detection of mycobacteria because of the high lipid content in their cell walls. Mycobacteria are resistant to most stains, but once stained with basic fushin, they resist decolourization with an acid alcohol mixture, hence the description "acid-fast". Acid fastness is variable in Nocardia species. In order to demonstrate acid-fastness of Nocardia, it is necessary to modify the decolourization step of Ziehl-Neelsen and Kinyoun staining methods to not exceed 5 � 10 seconds or to use Hank�s Modified Acid Fast stain which uses a 5% H2SO4- methylene blue solution to counterstain and decolourize. The stain is controlled by the use of premade slides of Nocardia organisms that are grown on Middlebrook , Cohn 7H10, or casein agar. A facultative actinomycetes can be used as a negative control.
If acid fast staining of the primary plate is equivocal, staining may be enhanced by passing the organisms through a high lipid medium such as Middlebrook 7H10, Lowenstein-Jensen or Casein agar. Of the remaining medically important actinomycetes (Nocardiopsis, Streptomyces and Actinomadura species) none are acid fast and the latter two have the presence of spores in characteristic pattern.
Characteristics confused?
Rhodococcus equi (formerly Corynebacterium equi) is a catalase producing aerobic actinomycetes, that can stain weak acid fast by modified Kinyoun, hence it can be confused with fragmented nocardial cells. When concerned about acid fast growers, differentiation can be done using tap water agar morphology medium (20 gm. plain agar in 100 ml. tap water). Inoculate the agar with a streak. Nocardia demonstrates fine-branched aerial hyphae, mycobacteria demonstrates frost-like to fir tree substrate hyphae, and Rhodococcus grow on the agar surface in classic diphtheroid fashion.
The following bio-chemical test can differentiate rhodococci from actinomycetes: Rhodococci species will degrade 1% ethylene glycol incorporated in solid 710 agar while other aerobic actinomycetes (including Nocardia) will generally fail.
Table 1: Presumptive Tests
|
|
Casein |
L-tyrosine |
Xanthine |
|
N. asteroides |
- |
- |
- |
|
N. brasiliensis |
+ |
+ |
- |
|
N. caviae |
- |
- |
+ |
Resistance Pattern of Nocardia asteroids
The Nocardia genus includes several species that are opportunistic pathogens in immunocompromised patients (3, 13). Species of Nocardia asteroides sensu stricto are the predominant human pathogens and are involved in pulmonary and brain abscesses (13). Since nocardiosis requires a long treatment (6 to 12 months or longer) and may cause a high mortality rate, the choice of the optimal antibiotic treatement is
crucial (7).
b-Lactams have been used as first-line treatment with little concern for the b-lactam susceptibility of Nocardia sp. Isolates (13). Knowledge of the mechanisms of b-lactam resistance profiles of Nocardia isolates may be critical for assessing thepotential clinical efficacy of b-lactams. A study of the antimicrobial susceptibility patterns of 78 clinical isolates belonging to the N. asteroides complex found that 95% of the isolatesexhibit one of the four major antibiotic resistance patterns (24). Type I (20% of the isolates) is susceptible to ampicillin and carbenicillin but intermediate in susceptibility to imipenem;
type III (18%) is susceptible to ampicillin and erythromycin; type V (17%) is resistant to broad-spectrum cephalosporins; and type VI, the most prevalent group (35%), is resistant
to ampicillin but susceptible to extended-spectrum cephalosporins and imipenem. Type II and type IV are extremely rare and not well characterized. Wallace et al. show that drug resistance patterns of type III and type V correlate with taxonomic groups and have been reclassified as Nocardia nova and Nocardia farcinica, respectively (21, 22). Isolates belonging to types I, IV, and VI are grouped into the same subspecies, named N.asteroides sensu stricto.
Although some nocardial b-lactamases have been characterized biochemically in N. asteroides (9, 17), Nocardia brasiliensis (19, 23), and N. farcinica (11, 20), the accurate role of b-lactamase in the b-lactam resistance pattern has scarcely been explored. Sequences of b-lactamase genes are available only for N.farcinica and the nonhuman pathogen Nocardia lactamdurans (5, 11).
Flowchart scheme for the identification of five species of Nocardia by using the chromogenic substrates MNP and PYR, IDX, and equivalent growth at 458C.
Strains of Nocardia studied
Normalized graph of rRNA gene restriction patterns obtained for strains belonging to the Nocardia asteroides complex.
Nutrition
Nocardia growth in different sterile media; Casein Agar � Tyrosine Agar � Xanthine Agar
Starch Agar
Nocardiosis is a disease of man, most frequently in patients who are severely immunocompromised, and animals caused by Nocardia species. The disease may resemble tuberculosis when the organism is inhaled, or may produce granulomatous
abscesses when the organism is introduced into tissue at the time of an injury.
Biochemical tests demonstrating the hydrolysis of casein, tyrosine, xanthine and/or starch, or growth in 0.4% gelatin may be used to differentiate Nocardia species and to differentiate Nocardia from Streptomyces species, which appear
morphologically similar to Nocardia in clinical materials and
in culture. Agar deeps are provided in a 20 mL fill so that the media
may be liquified and poured into Petri dishes. This provides a convenient source of medium with a longer shelf life than pre-poured plated media.
The most frequently encountered aerobic actinomycetes, members of the order Actinomycetales, include the genera Nocardia, Streptomyces, Actinomadura, Nocardiopsis, Rhodococcus and Dermatophilus. The testing algorithm that
permits identification of most aerobic actinomycetes consists of direct microscopic techniques and a minimum number of biochemical reactions.
determining the ability of isolates to hydrolyze casein.
agar) for testing the ability of isolates to utilize starch.
agar) for testing the ability of isolates to decompose tyrosine.
agar) for testing the ability of isolates to decompose xanthine.
Influence of cultural conditions on growth and lipolytic activity in Nocardia asteroides.
The growth and the production of extracellular and intracellular lipases were
measured from Nocardia asteroides grown under different cultural conditions.
Maximal growth and intracellular and extracellular activities were observed at 3
d after inoculation. Among the tested media, synthetic medium induced maximal
growth and extracellular activity, whereas tryptic soy broth induced the maximal
intracellular lipase activity. The best carbon and nitrogen sources for growth
and lipolytic activity were glucose, fructose, glutamate and nitrate,
respectively. The optimal C:N ratio for growth was in the range of 1:4 to 2:3
and for lipase activity the range was 2:3 to 3:2. Anything above or below this
range was detrimental to the organism and its enzyme activity. Under the
conditions of this study, N. asteroides grew best and had the highest lipase
activity when compared to N. brasiliensis and N. caviae.
Influence of nutritional factors on growth and hydrolytic enzyme production in Nocardia asteroides.
The growth and production of hydrolytic enzymes such as alpha-amylase, esterase and peroxidase as influenced by the type of media, carbon and nitrogen sources and C:N ratio were monitored in Nocardia asteroides at 37 degrees C. Sabouraud dextrose and the synthetic media yielded maximum growth compared with tryptic soy broth. Among the carbon sources (dextrose, fructose, sucrose, maltose, starch and citrate), monosaccharides supported maximum growth and induced higher alpha-amylase activity but repressed the peroxidase activity. On the other hand, the disaccharides and starch produced less growth but induced maximum esterase and peroxidase activities. Glutamate among the nitrogen sources (nitrate, nitrite, ammonium, hydroxylamine, glutamate and casein) supported maximum growth. Glutamate, nitrate and casein induced alpha-amylase and esterase activities but suppressed peroxidase activity. Nitrite, ammonium and hydroxylamine stimulated peroxidase activity to the maximum but repressed alpha-amylase and esterase activities. Low, medium and high C:N ratios induced maximum peroxidase, esterase and alpha-amylase activities, respectively.
Reproduction
Nocardia asteroides are found growth on blood agar but in a slow rate. This bacterium are Non-hemolytic. The Colonies are adhering to agar and the color ranges are from bright white to yellow-orange. Both types of strains in class culture collection. The Colonies can be smooth and moist or wrinkly with a velvety surface because of aerial Filametation.
Because of the slower growth of Nocardia, growing bacteria can easily obscure Nocardia colonies. Therefore, it is important to Gram stain clinical specimens for a rapid diagnosis.
These saprophytic organisms are strictly aerobic, grow at a broad range of temperatures and have been isolated on teeth in significant numbers in advanced tooth decay. Does not form spores.
Other Reproduction Characteristic
� Soil saprophytes that degrade organic matter.
� Exposure is via wounds or inhalation.
� Causes opportunistic, generalized, chronic, progressive disease.
� Characterized by supperative, granulomatous lesions.
� Four serotypes exist.
Importance / Significance
Nocardia asteroids Infection
Nocardiosis 
Nocardiosis is a relatively uncommon bacterial infection but is strongly associated with immunosuppression. The majority of infections occur in patients with weakened cell-mediated immunity. Patients commonly include those who have received bone-marrow or solid-organ transplantations and are on immunosuppressive therapy, those with HIV/AIDS, and those with malignancies. Other immunocompromised states include alcoholism, hypogamma-globulinemia, chronic granulomatous disease, chronic obstructive pulmonary disease, pulmonary alveolar proteinosis, diabetes, sarcoidosis, tuberculosis, and systemic lupus erythematosis.
Nocardia asteroides infection is acquired from the environment through inhalation into the respiratory tract, which leads to pulmonary disease. Subsequent hematogenous dissemination occurs from the lungs, which leads to cerebral abscess formation as well as cutaneous skin lesions. Dissemination, with cerebral abscess formation, occurs in approximately 15% to 44% of patients with systemic nocardiosis. Mortality rates are reported at approximately 30% with current early diagnosis and treatment regimens. This is in sharp contrast to previously reported mortality rates of 78% to 90%. Mortality is significantly higher in patients with multiple abscesses and is 0believed to be a function of the patient's degree of immunosuppression.
Others infections
Nocardia infections are rare but do cause significant infections in immunocompromised hosts. Most infections are caused by the N. asteroides complex
(including N. asteroides sensu stricto type VI, N. nova, N. farcinica and N. abscessus). Infection is acquired by direct inoculation into the skin or eye, or inhalation. Serious complications include dissemination to brain, kidney, spleen, liver,bone, skin and joints with a high mortality. Predisposing factors include therapy with steroids or immunosuppressive drugs, neoplastic disease, solid organ and bone marrow transplant,
chronic bronchopulmonary disease and AIDS. Rarely patients with underlying pulmonary conditions such as tuberculosis may be predisposed to colonization. Immunocompetent
patients may present with a chronic lung infection that is unresponsive to antimicrobial therapy. Clinical presentation includes cough, purulent sputum (sometimes blood streaked), pleural pain and night sweats. Immunosuppressed hosts may have more progressive, disseminated and life threatening infections such as necrotizing pneumonia often with cavitation, empyema, abscess or nodules.
Nocardia asteroides pneumonia with bacteraemia
�The Medical Journal of Australia 2003 www.mja.com.au Print ISSN: 0025-729X Online ISSN: 1326-5377
Case:
A previously well 57-year-old man presented to the emergency department with a 3-day history of severe dyspnoea. Six weeks earlier he had noticed coryzal symptoms with subsequent lethargy, reduced appetite with weight loss, and a non-productive cough. He then developed ankle swelling and increasing abdominal girth. He had a background of excessive alcohol consumption, but had abstained for 10 years.
On examination, he was febrile and in respiratory distress, with a respiratory rate of 35 per minute, pulse rate of 130 bpm, and blood pressure of 130/85 mmHg. Chest auscultation revealed bilateral diffuse coarse crackles.
Despite treatment with broad-spectrum antibiotics (intravenous ceftriaxone, dicloxacillin and erythromycin), the patient�s condition deteriorated rapidly, and he required intubations within 24 hours of presentation. Trap sputa contained abundant thin, partially acid-fast, beaded, branching filaments, suggesting Nocardia asteroides, which was later confirmed on culture using conventional biochemical testing. Several blood cultures taken on admission also grew N. asteroides. All cultures for mycobacteria were negative. The patient was treated with intravenous trimethoprim�sulfamethoxazole for a total of 5 weeks and oral minocycline for 14 weeks. He spent 6 weeks in hospital.
Liver biopsy, performed because of persistently abnormal hepatic function at follow-up 8 weeks after hospital discharge, showed central fibrosis and non-caseating granulomatous hepatitis. The patient received no further treatment and remained well 18 months later, with almost normal hepatic function and a clear chest x-ray.
Nocardia bacteraemia is rare, although the incidence appears to be increasing in the immunosuppressed. Nocardia spp. are seldom isolated in blood cultures, with one study finding that blood was the source of only 8% of all Nocardia isolates. Up to 30% of patients with Nocardia bacteraemia have coexistent infection with gram-negative bacteria. There has been one previous report of Nocardia pneumonia associated with positive blood cultures and liver disease. However, this patient had documented end-stage chronic liver disease at presentation, was taking prednisolone, and developed nocardiosis after prolonged hospitalization with gram-negative sepsis.
Granulomatous reactions are well described in Nocardia infection. Although granulomatous hepatitis is also described in sarcoidosis, it is rare and usually presents with itch and obstructive abnormalities of liver function.
In our patient, acute N. asteroides infection was the most likely cause of both the pulmonary infiltrate and the granulomatous hepatitis. Not only were results of modified acid-fast stains consistent with Nocardia spp., but cultures from multiple trap sputa and blood specimens also grew N. asteroides, suggesting a large load of this organism. No other organisms were isolated despite prolonged incubation of cultures, and the patient recovered after specific treatment directed at Nocardia spp. Furthermore, he remained well with no further treatment at 18-month follow-up, with near-normal hepatic function and no new abnormalities.
The Doctors conclude that N. asteroides infection can present as a fulminant community-acquired pneumonia with bacteraemia in the absence of immunosuppression or coexistent infection. This case illustrates the potential hepatic sequelae of Nocardia bacteraemia.
Chest x-ray of a patient with Nocardia asteroides pneumonia
Chest x-ray taken on admission to hospital, showing widespread non-symmetrical interstitial and airspace infiltrates.
Results of investigations
Breathing 10 L/min oxygen. � Occasional myelocytes, toxic granulation. � Levels of alanine and aspartate aminotransferase were in the reference range. � Including hepatitis B surface antigen and hepatitis C antibody. � Including antinuclear, extractable nuclear antigen, double-stranded DNA and antineutrophil cytoplasmic antibodies.
|
At presentation |
Result |
Reference range |
|
Arterial blood gases* |
|
|
|
pH |
7.37 |
7.35 �7.45 |
|
pCO2 (mmHg) |
43 |
35 � 45 |
|
pO2 (mmHg) |
60 |
75 �105 |
|
Bicarbonate (mmol/L) |
24 |
24 � 31 |
|
Base excess |
0 |
− 3 to 3 |
|
White cell count |
|
|
|
Total (x 109/L) |
31.5� |
4 �11 |
|
Neutrophils (x 109/L) |
30.2 |
2 � 7.5 |
|
Lymphocytes (x 109/L) |
0.7 |
2 � 4 |
|
Follow-up at 8 weeks |
|
|
|
Liver function tests� |
|
|
|
Bilirubin (μmol/L) |
9 |
< 18 |
|
Alkaline phosphatase (U/L) |
124 |
30 �100 |
|
γ-Glutamyl transferase (U/L) |
153 |
< 35 |
|
Iron studies |
|
|
|
Serum ferritin (μg/L) |
446 |
30 � 400 |
|
Serum iron (μmol/L) |
< 3 |
10 � 30 |
|
Transferrin (g/L) |
1.9 |
2.0 � 3.5 |
|
Transferrin saturation |
< 6% |
15%�50% |
|
Vitamin B12 (pmol/L) |
376 |
> 126 |
|
Immunological tests |
|
|
|
HIV antibodies |
Negative |
|
|
Hepatitis B and C� |
Negative |
|
|
Autoantibody screen� |
Negative |
|
|
Complement C3 (g/L) |
1.07 |
0.82 �1.45 |
|
Complement C4 (g/L) |
0.25 |
0.15�0.45 |
Liver biopsy in a patient with Nocardia asteroides pneumonia
Core biopsy of liver, showing a granuloma within the central portal triad (arrow); the portal ducts are expanded and fibrosed with a patchy lymphocytic infiltrate (original magnification x 40; haematoxylin and eosin stain).
Treatments for Nocardia asteroids.
Nocardiosis
Some observations on therapy: Nocardiosis has been treated with sulphonamides since the 1940's. The present treatment of choice for localised pulmonary and cutaneous nocardiosis is trimethoprim / sulfamethoxazole. In severe illness in patients with disseminated disease, a combination of supplemental agents such as amikacin, ceftriaxone, cefotaxime or imipenen are added. Also with treatment failure (prolonged treatment) or severe illness with Nocardia sensitivity testing should be done on the isolate.
Medical management with trimethoprim/sulfametho-xazole, an agent that readily penetrates the central nervous system, is the first-line treatment for nocardiosis. Second-line treatments include imipenem/cilastatin, amikacin, cefo-taxime, minocycline, and other antibiotics. Nocardia species are generally resistant to penicillin and require 6 months to 1 year of antibiotic treatment. Surgical management for cerebral nocardia infection is often based upon the patient's clinical and immune status and the number and size of lesions. In immunocompromised patients and those with multiple abscesses, a more aggressive surgical approach, such as craniotomy and excision, is indicated to maximize likelihood of survival. In non-immunocompromised patients or those with a single lesion, stereotactic aspiration followed by antibiotic therapy may be sufficient. Fleetwood et al suggest stereotactic or open biopsy of nonspecific cerebral lesions for diagnostic and therapeutic purposes, even in cases in which a presumptive diagnosis has been made based on sputum cultures. This is based on the possibility of multiple organism infections that commonly occur in immunocompromised patients. Medical treatment would be based on susceptibility results.
Others
N. asteroides complex is usually susceptible to trimethoprim-sulfamethoxazole (the drug of choice), amikacin, cefotaxime and ceftriaxone, ciprofloxacin and minocycline. N. nova is characterized by susceptibility to erythromycin and broad spectrum cephalosporins but resistance to amoxicillin-clavulanic acid. Since Nocardia remain such a heterogeneous group of organisms and have variable susceptibility patterns, therapy must be adjusted to the particular species or strain present and to the site and type of infection. Susceptibility testing of clinically significant isolates at a reference laboratory is recommended.
Human isolates of Nocardia asteroides selected for comparative analysis of
interactions in the brain and lungs.
Scanning electron micrographs of log-phase cells of eight strains of Nocardia asteroides in the lungs of BALB/c mice 3 h after intranasal administration. (A) UC-111; (B) UC-44; (C) GUH-2; (D) UC-59; (E) UC-129; (F) UC-34; (G) UC-63; (H) ATCC 19247. All of the nocardial cells shown in panels A to H have approximately the same filament diameter of 0.4 to 0.6 mm. The arrows in panels A to D point to areas of penetration of the host cell by the nocardial filament. The arrow in panel G indicates longitudinal adherence of a nocardial filament to a goblet cell. Abbreviations: AS, alveolar surface; CC, Clara cell; CE, ciliated epithelial cell; GC, goblet cell; IS, interalveolar septum.
Conclusion
Description
Colonies are slow growing, aerobic,
gram-positive, acid-fast to partially acid-fast, glabrous, heaped and folded,
and white, pink, red, orange, or tan in color. Filaments are branched,
fragmenting into rod and coccoid forms. Aerial filaments usually present.
Salient Characteristics
Medically important species of Nocardia are lysozyme resistant and do not produce acid from cellobiose.
Laboratory Precautions
Handle with care, but special precautions are not necessary.
Symtpoms
The most common symptoms with the pulmonary form of nocardiosis are fever, cough, and chest pain. With brain nocardiosis, the symptoms are usually headache, lethargy, confusion, seizures, and sudden onset of neurologic problems.
Treatment
� Sulfonamides
� TMP/SMX
� Minocycline
� Amikacin
� growth in nonactivated macrophages
� intracellular growth
� prevention of phagolysosome
Preventions
� It is not a contagious infection.
� It is an opportunistic infection
� No preventive measures can be taken
Other Species
� Nocardia brasiliensis
� Nocardia otitidiscaviarum
Diseases
� mycetoma
� nocardiosis
Extra Features
A
B 
C
D
E
F
A = Perivascular growth of Nocardia asteroides GUH-2 in the region of the substantia nigra 24 h after infection.
B = Growth of Nocardia asteroides GUH-2 within cells beneath the basement membrane of the capillary 24 h after infection.
C = Growth of Nocardia asteroides GUH-2 in a neuron 24 h after infection.
D = Interactions of Nocardia asteroides GUH-2 with axons 24 h after infection.
E = Nocardia asteroids induced axonal degeneration and myelin disruption 24 h after infection.
F = Interaction of phagocytic cells (probable microglia) with Nocardia asteroides GUH-2 in the brain 24 h after infection.
Source
http://www.pubmedcentral.gov/
http://www.interchg.ubc.ca/cmpt/html/
http://www.medscape.com/viewarticle/
http://www.ncbi.nlm.nih.gov/entrez/
http://www.mja.com.au/public/issues/
http://iai.asm.org/cgi/content/abstract/
http://www.doctorfungus.org/thefungi/nocardia.htm
http://www.dermnetnz.org/index.html