NocardiaNocardia, , ActinomyceActinomyces, s, PropionibacteriumPropionibacterium

NocardiaNocardia, , ActinomyceActinomyces, s, PropionibacteriumPropionibacterium

Aerobic Gram-Positive Bacilli Aerobic Gram-Positive Bacilli Form filamentsForm filaments

(Aerobe, Anaerobe)(Aerobe, Anaerobe)

Order: Actinomycetales• Fungus-like characteristics, branching (like

mycelium)• Filaments; pleomorphic, diphtheroid, coccoid

cells• Bacteria (prokaryote) not fungal (eukaryote)

– Prokaryote cell wall, internal structures– Antibiotic susceptibility

• All slow growing• Considered higher prokaryotes • Aerobic

– Nocardia - cutaneous, pulmonary, CNS, opportunistic infection

• Anaerobic – Actinomyces - actinomycosis– Propionibacterium - acne, opportunistic infection

Nocardia• Found worldwide soil,

vegetation• G(+), may be weak;

branching filaments, fragment bacillary, coccoid forms

• Partially acid fast (use weak acid decolorize), due to mycolic acid in cell wall

• Wide infection range – colonize, mycetoma, systemic, pulmonary, opportunist

Nocardia: Lab culture

• Slow growth most lab media; require up to 1 week culture

• Specimens inoculated enriched media– Brain heart infusion agar – 7H10, Lowenstein-Jensen

(designed for Mycobacterium culture)

• Colonies - orange, dry, crumbly, adherent

• Better isolation on enriched selective media such as BCYE + antibiotics

• Aerial hyphae on colony surface

Nocardia: Mycetoma (Cutaneous)

• Mainly caused by N. brasiliensis; common in tropical, semi-tropical areas, rare in USA

• MO enters body through breaks in skin, often splinters, thorns of hands and feet

• Localized infection involving skin, cutaneous, subcutaneous tissue

• Three features seen:– Swelling, pus– Draining sinus tracts– Granules (yellow, “sulfur”) in pus

Nocardia: Nocardiosis (Inhalation)

• Mainly caused by Nocardia asteroides• Usually disease of compromised host• Localized, disseminated disease

following inhalation of MO• Resembles TB – bronchopneumonic,

acute or relapsing; abscesses coalesce, extensive tissue damage

• May disseminate, predilection for brain meninges

• High mortality

Nocardia: Treatment and Prevention

• Antibiotic therapy - 6 weeks or more to prevent dissemination of infection

• Mycetoma– Aminoglycoside– Proper wound care and drainage– Surgical intervention

• Nocardiosis– Sulfonamides, SXT– Combination antibiotics for severe,

progressive disease• MO ubiquitous in environment,

impossible to avoid

Actinomyces• “ray” “fungus”• G(+) pleomorphic, diphtheroid

bacilli; filamentous• Not acid fast• Facultative anaerobe, strict

anaerobe• Grow slowly on anaerobic CBA, PEA

– Rough, granular colonies, resemble molars

• Lab ID:– Gas liquid chromatography (GLC) of

metabolic by-products– Specific fluorescent antibody staining

assay

• Most commonly isolated – Actinomyces israelii

Actinomyces: Actinomycosis

• Normal flora in humans, animals• Colonize - URT, GI, female GU tract• Endogeneous infection – NF invade

host when mucosal disrupted (trauma, surgery, ingestion, foreign bodies i.e. intrauterine device)

• Cervicofacial infection - “lumpy jaw”– Following tooth extraction, dental

surgery– May invade bone– Rare today due to prophylactic

antibiotics• Thoracic, abdominal infection• Meningitis, endocarditis, genital

infection• Slow developing, chronic infection

Actinomycosis • Infection

characterized by draining sinuses

• Characteristic granules– Bacteria colonies;

dense rosettes of club-shaped filaments

– Radial arrangement

• Treatment– Penicillin– Surgical removal

diseased tissue

Propionibacterium: Genera• “propionic acid”• Normal flora of skin,

oropharynx, female GU tract

• G(+) small bacilli, pleomorphic, diphtheroids

• Most common isolates– P. acnes – acne,

oportunistic infection– P. propionicus – oral

abscess

Propionibacterium: Lab Culture

• Grow well on CBA– Tiny translucent, opaque, white to

gray colonies • Growth may be slow• Anaerobic• Occasional strains grow in CO2

(aerotolerant)

Propionibacterium: Infection and Disease

• Skin normal flora• Implicated in acne

– Adolescence more sebum produced– P. acnes metabolizes sebum to fatty acids– Contribute to inflammatory response in

acne

• Opportunistic infection – prosthetic device (heart valves, joints), IV lines (catheter, CSF shunt)

Propionibacterium: Treatment and

Prevention• Skin cleansing not effective, lesion

develops in sebaceous follicle• Topical benzoyl peroxide and

antibiotics• Accutane

– Inhibits sebum formation– Used only in severe case of acne because

of side effects• Effectively treated by erythromycin,

clindamycin

Class Assignment• Textbook Reading

– Chapter 16 Aerobic Gram-Positive Bacilli• Aerobic Actinomycetes - Nocardia

– Chapter 22 Anaerobes of Clinical Significance• Actinomyces• Propionibacterium

• Key Terms• Learning Assessment Questions

Lecture Exam IITue., Feb. 28, 2012

• Vibrio thru New Molecular Methods • Lecture, Reading, Key Terms, Learning

Assessment Questions• Case Study 4, 5, 6 (Pseudomonas,

Francisella, Bacillus)• Exam Format

– Multiple Choice– Terms– True/False Statements– Short Essay

• Review, Review, Review!

Case Study Reports (Revised Due Date)

• March 1 - CS #7 Mycobacterium• March 6 – CS #8 Clostridium• March 8 – CS #9 Chlamydia• March 13 – CS #10 Legionella