Actinomycetes (Micro Exam 3)
Misc. pathogens
1. Legionella sp.--Legionnaires' disease 2. Bartonella sp. --Cat scratch disease/other 3. Eikenella corrodens--Human bite wound
Actinomycetes
1. large group= characteristics of bacteria and fungi 2. form branches or filaments=hyphae 3. infections resemble fungal diseases 4. bacterial=procaryotic cell wall 5. susceptible to penicillin like bacteria
Actinomycetes functions and characteristics
1.form of fungi-like bacteria 2. sometimes called thread bacteria 3. in composting, they give off an earthy smell 4. primary decomposers of woody stems, newpapers, and bark 5. are very common in the soil at a rate of 1/4 pound per cubic foot in healthy soil especially higher pH soil (alkaline) and drier soils 6. comprises 5% of soil's total population
Actinomycosis
Actinomyces israelii and others
______ is the primary source of antibiotics used in topical antibiotic creams
Actinomycetes
B. henselae
Cat Scratch Disease -scratches, bites, cat fleas -chronic regional swelling of lymph nodes -culture often negative -view organism on tissue sections -antibiotics=often not used; tetracycline, erythromycin, rifampin
Nocardiosis
Nocardia asteroides and others
Actinomycosis diagnosis
-examine pus for white or yellow granules -Gram stain (+) -filamentous -culture -immunofluorescence
Actinomycosis genital
-intrauterine devices=inflammation
Legionella Epidemiology
-located in fresh water -attach to pipes, rubber, plastics -avoid chlorination-gobbled by amoeba -aerosols=human-human not shown -70% predisposed=underlying illness, older, heavy smoker
Nocardiosis diagnosis
-microscopic appearance=granules, filaments -grow on appropriate medium= 7-10 days. -Gram +, acid-fast organism -biochemical tests (casein hydrolysis +, urea hydrolysis +, tyrosine hydrolysis +)
Actinomycosis cervicofacial
-most common -lower jaw=abscess formation -sinus tracts that reach the skin
Legionella
-respiratory disease -difficult to isolate -CDC identified the organism
Nocardiosis treatment
-surgical debridement -early diagnosis important-poor recovery after systemic infection -treat with cotrimazole or sulfadiazine -respiratory infections may require several months
Actinomycosis treatment
-surgical debridement of damaged tissue is a pre-requisite to antibiotic therapy -Penicillin G for 3-4 weeks= treatment of choice -Trimethoprim and sulfamethoxazole result in more rapid cure
Those at risk for nocardiosis:
-weakened immune system -chronic lung disease -chronic steroid therapy -cancer -organ/bone marrow transplants -HIV/AIDS
______ is the most numerous of all actinomycetes
Streptomyces
Sugar consumption=...
acid production which erodes the enamel surface = dental carie
periodontitis
destruction of the bone that supports teeth
If plaque not removed...
inflammation of the gums=gingivitis
Actinomycetes are Gram ____
positive
How do A. viscosus organisms attach to enamel surface?
production of pili and extracellular polysaccharides (sticky)
Actinomycosis abdominal
trauma of intestine or abdominal wall
Eikenella
-E. corrodens -most frequently isolated -human bite wounds or fist fight injuries -may lead to sinusitis, brain abscess, pneumonia, endocarditis -slow growing, fastidious organism that "corrodes" the agar -opportunist
Legionella pneumophila
-Gram -, aerobic bacillus -Facultative intracellular parasite -produces a cytotoxin
Actinomycosis thoracic
-aspiration into lung -extension of cervicofacial -hematogenous
Nocardia asteroides
-compromised patients -steroid administration= patient more susceptible -inhalation or introduction to traumatized tissue -see nodular abscesses -in skin and soft tissue= see sinuses and granules -as sinus tracts extend to deep muscle and bone=actinomycetoma
Legionella diagnosis
-culture from sputum or lung specimen on BYCE agar -use direct fluorescent antibody test/moderate sens -use indirect fluorescent antibody test=4-fold rise, not very useful early in disease -Radioimmunoassay=detect AG in urine, 86%
Bartonella
-8 species -short, Gram- bacilli -aerobic -fastidious growth requirements -animal reservoirs/insect vectors
Dental plaque
-Actinomyces viscosus -organisms attach to enamel surface
Actinomycosis
-Cervicofacial -Thoracic -Abdominal -Genital