Gram-Positive Bacilli
Part Four
MLAB 2434: Microbiology
Keri Brophy-Martinez
Non-Spore Formers &
Branching
• Gram positive rod
• Non-spore formers
• Pleomorphic morphology
– Branching
• Genera
– Actinomyces
– Nocardia
– Streptomyces
Aerobic Actinomyces
• Member of the normal flora of mouth,
head, and neck
• Pathogens
– Human bite wounds, eye cultures
– Cervicitis and endometritis in women
– Actinomycosis
Aerobic Actinomyces
• Gram stain
– Gram positive rod
– Filamentous,
branching
– Can be beaded
• Non acid-fast
Aerobic Actinomyces
• Colony morphology
– Spider or granular center
– Branching filaments
– Takes up to 7-14 to develop
• Key Biochemicals
– Catalase negative
– Nonmotile
– Non-fermenters
– Produce H2S
Aerobic Actinomycetes
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Nocardia
Streptomyces
Actinomadura
Gordonia
Rhodococcus
Tsukamurella
Nocardiopsis
Dermatophilus
Nocardia:
Clinical Significance
• Pulmonary form
– Mostly in
immunocompromised
– High fatality
– Starts as lung lesion
• Cutaneous
– Three forms
• Mycetoma
• Lymphocutaneous
• Superficial
Sulfur granules collected
from draining sinus tracts
in mycetoma
Nocardia:
Laboratory Diagnosis
• Microscopy
– Gram-positive
branching filaments
– May show beading
appearance
– Verify with acid fast
stain
• Weakly Acid-fast
Gram-stained smear of sputum
showing Gram-positive branched
beaded bacilli.
Nocardia:
Laboratory Diagnosis
• Gram-positive filamentous bacilli
• Suspicious for actinomycetes
Nocardia:
Laboratory Diagnosis
• Cultural characteristics
– Chalky, matte, dry, crumbly
appearance
– May be pigmented
– Beta hemolytic
• Identification
– Urease positive
– Catalase positive
– Molecular testing
Streptomyces
• Habitat
– Soil and decaying vegetation
• Disease states
– Mycetoma- a chronic, localized, painless,
subcutaneous infection
• Sites: head and neck
– Wound & Skin infections
Streptomyces:
Laboratory Diagnosis
• Microscopic Morphology
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Gram positive rod
Branching
Spider-like
Non-acid-fast
Streptomyces:
Laboratory Diagnosis
Morphology & Characteristics
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Aerobic growth in 3-30 days
Waxy, bumpy or velvety rugose forms, yellow to orange
Will grown on SBA, mycology media and LJ media
GPR with extensive branching, chains and spores
• Identification
– Acid-fast= negative
References
• http://www.atsu.edu/faculty/chamberlain/golden2000/case5.htm
• http://chesschumpion.blogspot.com/2007/03/time-to-put-on-yourthinking-caps.html
• http://en.wikipedia.org/wiki/File:Bacillus_subtilis_Gram.jpg
• https://labs.uhstx.com/clinical_int/dols/appb.htmlhttp://www.iccb.state.il
.us/pt3/mod/science/mod_bio111/mod10/p4.html
• http://www.flickr.com/photos/microbeworld/sets/72157625392265538/d
etail/http://www.uaz.edu.mx/histo/pathology/ed/ch_9b/c9b_clue.htm
• Kiser, K. M., Payne, W. C., & Taff, T. A. (2011). Clinical Laboratory
Microbiology: A Practical Approach . Upper Saddle River, NJ: Pearson
Education.
• Mahon, C. R., Lehman, D. C., & Manuselis, G. (2011). Textbook of
Diagnostic Microbiology (4th ed.). Maryland Heights, MO: Saunders.