3. Actinomycetes

8/3/2019 3. Actinomycetes

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ACTINOMYCETES



INTRODUCTION-1-

• Actinomycetes include three genera :Actinomyces , Nocardia , and Streptomyces .

• These organisms have been shown to behigher bacteria, but they were thought to befungi for many years because they have

filamentous forms, 0.5 to 0.8 microns indiameter, which appear to branch.



INTRODUCTION-2-

Streptomyces spp. -Gram-positive, filamentous or irregular-shapedprokaryote; used in the production of the antibiotic streptomycin.



INTRODUCTION-3-

• The clinical manifestations of infection are similar tothose of a systemic fungal infection. It is now clearthat they are not fungi but are closely related to themycobacteria.

• Some properties of these genera include:• Actinomyces are anaerobic, while Nocardia and

Streptomyces are aerobic.

• Nocardia stain partially acid-fast, Actinomyces andStreptomyces are not acid-fast.



ACTINOMYCOSIS-1-

• Actinomycosis is a chronic suppurative and granulomatousdisease of the cervico-facial, thoracic or abdominal areas.

• The most common cause of actinomycosis is the organism

Actinomyces israelii which infects both man and animals.

• In cattle, the disease is called "lumpy jaw" because of the hugeabscess formed in the angle of the jaw.

• In man, A. israelii is an endogenous organism that can be isolatedfrom the mouths of healthy people



IllustrationsActinomycosis Cervicofacial



ACTINOMYCOSIS-2-

• Frequently, the infected patient has a tooth abscess or a toothextraction and the endogenous organism becomes established in thetraumatized tissue and causes a suppurative infection. These abscessesare not confined to the jaw and may also be found in the thoracic areaand abdomen.

• The patient usually presents with a pus-draining lesion, so the pus willbe the clinical material sent to the laboratory. This diagnosis can bemade on the hospital floor. When the vial of pus is rotated, the yellowsulfur granules, characteristic of this organism, can be seen with thenaked eye. These granules can also be seen by running sterile waterover the gauze used to cover the lesion. The water washes away the

purulent material leaving the golden granules on the gauze.

• This organism, which occurs worldwide, can be seen histologically as"sulfur granules" surrounded by polymorphonuclear cells (PMN) formingthe purulent tissue reaction.



Sulphur granules in actinomycosis



Staining

Histopathologic changes due to the gram-positive organism, Actinomyces israelii .Using a modified Fite-Faraco stain, a “sulphur granule” is shown in the middle of the image.

These granules actually represent colonies of A. israelii , a gram-positive, anaerobicfilamentous bacteria



ACTINOMYCOSIS-3-

• The organism is a gram positive rod thatfrequently branches.

• The laboratory must specifically beinstructed to culture for this anaerobicorganism.

• These lesions must be surgically drained priorto antibiotic therapy and the drug of choice islarge doses of penicillin



NOCARDIOSIS -1-

• Nocardiosis primarily presents as a pulmonary diseaseor brain abscess in the U.S.

• In Latin America, it is more frequently seen as thecause of a subcutaneous infection, with or withoutdraining abscesses. It can even present as a lesion inthe chest wall that drains onto the surface of thebody similar to actinomycosis.

• Brain abscesses are frequent secondary lesions.



NOCARDIOSIS-2-

• The most common species of Nocardia thatcause disease in human beings are N.brasiliensis and N. asteroides .

• These are soil organisms which can also befound endogenously in the sputum ofapparently healthy people.

• N. asteroides is usually the etiologic agent ofpulmonary nocardiosis while N. brasiliensis isfrequently the cause of sub-cutaneous lesions



Nocardia asteroides and Nocardia

brasiliensis

Gram-positive acid-fast Nocardia brasiliensis bacteria using a modified Fite-Faraco stain.80% of cases of Nocardiosis show clinical features of invasive pulmonary infection,

disseminated disease, or brain abscess; 20% show cellulitis.

Gram-positive aerobic Nocardia asteroides slideculture reveals chains of amongst aerial mycelia



NOCARDIOSIS-3-

• The material sent to the lab, depending on the presentation ofthe disease, is sputum, pus, or biopsy material.

• These organisms rarely form granules. The Nocardia are

aerobic, gram-positive rods and stain partially acid-fast (i.e., theacid-fast staining is not uniform).

• There are no serological tests, and the drug of choice isBactrim (Trimethoprim plus sulfamethoxazole).

• The Nocardia grow readily on most bacteriologic and TB media.The geographic distribution of these organisms is worldwide.



STREPTOMYCOSIS-1-

• The streptomyces species usually cause the disease entity known asmycetoma (fungus tumor).

• These infections are usually subcutaneous, but they can penetratedeeper and invade the bone.

• Some species produce a protease which inhibits macrophages.

• Material sent to the lab is pus or skin biopsy.

• The streptomycetes are aerobic like Nocardia , and can grow on both

bacterial and fungal (Sabouraud) media. They produce a chalky aerialmycelium with much branching



STREPTOMYCOSIS-2-

• It is important to let the lab know the suspectedorganism because most bacterial pathogens will growout overnight, but the actinomycetes take longer tobe visible on the culture plates (48-72 hours).

• The various species of streptomyces produce granulesof different size, texture and color.

• These granules, along with colonial growth andbiochemical tests, allow the bacteriologist ormycologist to identify each species.



streptomyces granules

Actinomycotic mycetomatous granule due to the bacteria Streptomyces somaliensis



STREPTOMYCOSIS-3-

• The organisms are found world-wide.

• There are no serological tests

• The drugs of choice are the combination ofsulfamethoxazole/trimethoprim or amphotericin B.

• In the tropics, this disease may go undiagnosed oruntreated for so long that surgical amputation may bethe only effective treatment.

3. Actinomycetes

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