E.Rhusiopathiae, Corynebacterium, A.Hemolyticum, Lactobacillus, Nocardia Flashcards
What are the characteristics of E.Rhusiopathiae?
Gram positive rods forming long filaments
Facultative Anaerobe
Slow growth
Small gray colonies
Alpha hemolytic
Catalase Neg (differentiate from listeria)
Non-motile
WEak fermenter
Produce H2S on TSI (ONLY GRAM + PRODUCING H2S)
What is the epidemiology of E.Rhusiopathiae?
Found in soil and groundwater worldwide
Uncommon disease in humans, more in animals
Humans acquire infection from animals
What are the 2 forms of human infections of E.Rhusiopathiae?
Erysipeloid: localized skin infection on fingers or hands that spreads peripherally as discoloration fades
Septicemic: uncommon; if present associated with endocarditis
How is E.Rhusiopathiae treated?
Penicillin
What are the characteristics of Corynebacterium?
Gram Positive Rods
Resemble CHINESE LETTERS
Grows aerobic or facultatively anaerobic
Small white non-hemolytic colonies
Where is Corynebacterium found?
Plants and animals
What are the important species of corynebacterium?
C.Diptheriae
C.Jeikeium
What are the characteristics of C.Diphtheriae?
Infection transmitted via respiratory droplets or direct contact with cutaneous infection
Causes Diphtheria
Rare in US due to immunization
What is the form of vaccine for C.Diphtheriae?
Vaccinate with toxoid treated with formalin
REvaccinate every 10 years
Describe the pathogenesis of C.Diphtheriae
Caused by potent exotoxin -> inhibits proteiin synthesis of cells
2 Subunits
A: inhibit protein synthesis
B: Binds cell receptor
What makes C.Diphtheria virulent?
If it is infected with bacteriophage with the toxin gene
What are the clinical presentations of a pt with diphtheria?
Pharyngitis with exudates on tonsiles, uvula, soft palate
Tough, gray pseudomembrane of fibrin, WBC, bacteria, debris
Can have cardiac injury if toxin travels to heart
Reversible paralysis if toxin gets to CNS
How is Diptheria diagnosed?
Clinical Evaluation, no rapid lab test
Take throat swab for cultures to prove prsence of toxin
How is Diptheria treated?
Antitoxin + Penicillin or Erythromycin
What are the important characteristics of C.Jeikeium?
Infects immunocompromised patients
From blood cultures, catheter lines, skin
Resistant to most Abx EXCEPT VANCOMYCIN
What are the characteristics of Arcanobacterium Hemolyticum?
Nonspore forming Gram positive rod Irregular curved formation Catalase Negative B-hemolytic
Where is A.Hemolyticum isolated mostly from?
Young Adults symptomatic of pharyngitis, rash, fever, pseudomembranes in pharynx/tonsils and submandibular lymphadenopathy
Wounds, abscesses and blood of patients iwth septicemia and endocarditis
What is A.Hemolyticum similar to on plates?
Group A Strep. But doesnt type wiht Group A Strep Anti-sera
What are the characteristics of Lactobacillus
Gram Positive Rod
Non-spore forming
Prefers Anaerobic
Opportunistic Pathogen- sepsis, endocarditis
Where is Lactobacillus normally found?
Yogurt
Oral Cavity, vaginal tract
What are aerobic actinomycetes?
Aerobic Gram Positive Rods
Catalase Positive
Where are Aerobic Actinomycets found?
Soil and decaying vegetation
Colonize animals and humans
What is Nocardia?
Aerobic Actinomycetes
What are the characteristics of Nocardia?
Gram Positive Rods Partially Acid FAst Cell wall: MYCOLIC ACID Strict AEROBE Grows well on nonselective agars Prolonged incubation time
How does Nocardia look on gram stain?
Beaded rod appearance
Need to use acid fast stain because it doesn’t stain well
How does Nocardia look on modified acid fast stain?
STains pink with similar appearance to gram stain
How does nocardia infection occur?
Exogenous infection via inhalation or traumatic introduction (cutaneous)
What are predisposing factors for nocardia infection?
Immunocompromised patients with chronic pulmonary disease or T cell deficiencies
Why don’t we cell Nocardia with AIDS patients?
AIDS pts are given Bactrim prophylatically -> Nocardia is also prophylaxis with Bactrim
Would see if they didn’t take Bactrim
What does Nocardia infection cause?
Bronchopulmonary Disease
Primary or 2ndary Cutaneous Infections
Secondary CNS Infections (ex: Brain Abscess)
How are Nocardia infections treated?
Sulfonamides and proper wound care
• A 22 year old medical student presents with symptoms
of pharyngitis with a fever, and cutaneous rash. A
throat culture reveals small beta hemolytic colonies
that are catalase-negative and stain as short Grampositive rods exhibiting Chinese character
morphology. What is the most likely agent of this
students pharyngitis?
A. Arcanobacterium hemolyticum
B. Corynebacterium diphtheriae
C. Erysipelothrix rhusiopathiae
D. Listeria monocytogenes
E. Streptococcus pyogene
b
