Gram-Positive Bacilli Part Four

Gram-Positive BacilliPart Four

MLAB 2434: MicrobiologyKeri 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

• 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– Gram positive rod– Branching– Spider-like– Non-acid-fast

Streptomyces:Laboratory Diagnosis

Morphology & Characteristics– 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-your-

thinking-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/

detail/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.