Actinomycetes
Actinomycetes:The family Actinomycetaceae consists of parasitic or pathogenic gram + microorganisms. These organisms have been shown to be higher bacteria,but they were thought to be fungi for many years because they have filamentous forms,which appear to branch.How ever ,that they are closer of bacteria than to the fungi including cell wall compositionandsensitivity to penicillin.
Actinomycetes (order)
Three genera Actinomyces species Nocardia species Streptomyces species*Are true bacteria with long _branching filaments analogus to fungal hyphae *The chemical structure of the cell wall of these organisms is similar to that of Corynebacteria and mycobacteria . *Actinomyces spp.are microaerophilic or anaerobic while Nocardia spp.and Streptomces spp.are aerobic organisms. *Nocardia stain partially acid fast while Actinomyces and Streptomyces are not acid fast. *Actinomyces produce granules,most actinomyces in tissue do not stain with H and E stain commonly used for general histopathology.
Actinomycetes:
Asmall amount of the specimen is placed on the microscope slide ,a dye (carbol fuchsin ) is placed on the slide and heated ,the slide then washed with an acid alcohol,then counter stain is placed (methylene blue). Bacteria that retain the first dye areacid fast(because of their resisttance to acid wash ,presence of mycolic acid). Bacteria that wash free of the first dye and take the counter stain are non acid fast. Non acid fast---blue Acid fast-----red
Acid fast stain
Gram Positive Filamentous Bacteria
GENUSOXYGEN
GRANULE
ACIDFAST
Mycobacteria
aerobe
no
yes
Actinomyces
ANAEROBE
YES
no
Nocardia
aerobe
sometime
PARTIALLY
Streptomyces
aerobe
YES
no
Nocardia acid fast stain
Actinomyces spp.Although most Actinomyces are soil organisms , they are potentially pathogenic commensals. *They are a major component of dental plaque *Other sites colonzed are the female genital tract & the tonsillar crypts.
Granules
Actinomces species*Actinomyces israelli . actinomycosis in human. A.bovis,an animal parasite,in lumpy jaw of cattle. A. odontolyticus: A close relationship between this m.o. and the earliest stages of enamel demineralization A. naselundii,is capable of inducing periodontal disease,plaque formation ,root canal caries and gingivitis.
A.myeri A.viscosus. Isolated from human root surface, from mandibular abscess
Habitat of Actinomyces: *Not highly virulent. *Component of oral flora ,dental plaque,tonsilar crypts,periodontal pockets *An association between root surface caries and Actinomyces has been described. *Are known to be increased in gingivitisA.Israelli # Anaerobic gram positive bacilli exhibit true branching,non motile non sporing ,and non acid fast #This organism is commensal of the mouth and possibly of the female genital tract #Amagor agent of human actinomycosis #Clumps of the organisms can be seen as yellowish (sulphur granules) in pus discharching from sinus tract.
Culture and identification Grows slowly under anaerobic conditions, on blood or serum glucose agar. Colonies on blood agar resemble bread crumbs or the surface of molar teeth. Because of the exacting growth requirements and relatively slow growth. Isolation of this organism from clinical specimens is difficult. Particularly because the other faster growing bacteria in pus . Sulphur granules in lesions are a clue to their presence ,when possible ,these granules should crushed ,gram stained and observed for G+ branching filaments and also cultured. Sulphur granule production a tangled mass of filamentous organisms and debris ----hall mark of actinomucosis.
Sulphur granules
Pathogenisity *Chronic, granulomatous, endogenous infections of the orofacial region. *Typically the lesion present as chronic abscess ,commonly at the angle of the lower jaw ,with multiple external sinuses, there is usually a history of trauma such as a tooth extraction or a blow to the jaw *While the majority of the lesions (60-65)% are in the cervicofacial region ,some 10_20% of abdominal and others are in the lung(( thoracic)). *Although most infections are monomicrobial in nature a significant proportion of infections could be polymicrobial with other bacteria such as A.actinomycetemcomitans Haemophilus spp. and anaerobes acting as coinfecting agentTreatment sensitive to penicillin, For chronic infections ,prolonged courses up to 6 weeks are necessary. *Tetracycline its good for bone penetration. *Prevention of these infections is difficult because of their endogenous nature . *Surgical intervention may be necessary of their endogenous nature .