1. Gram-Positive Bacilli Part Two
MLAB 2434: Microbiology
Keri Brophy-Martinez

2. Rods
Erysipelothrix
Lactobacillus
Gardnerella vaginalis

3. Erysipelothrix rhusiopathiae: General characteristics
Gram positive, non–spore-forming, pleomorphic rods (can produce long filaments)
Distributed in nature
Can cause disease in animals (swine, turkey, sheep); swine is the main reservoir
Humans acquire the infection through occupational exposure, such as cuts & scratches (fish handlers, animal products)

4. Erysipelothrix rhusiopathiae: Clinical Infections
Erysipeloid
Self-limiting localized infection at the site of inoculation
Produces painful swelling, usually on the hands or fingers
Heals within 3 to 4 weeks
Treat with penicillin, cephalosporin, erythromycin
Endocarditis
May occur in those who have had valve replacements
Disseminated infections may occur, but rarely

5. Laboratory Diagnosis: Erysipelothrix rhusiopathiae
Colony Morphology
CO2 is required
Grows on blood or chocolate agar
Colonies may appear gray or translucent, pinpoint
Alpha hemolysis or nonhemolytic

6. Laboratory Diagnosis: Erysipelothrix rhusiopathiae
Microscopic Morphology
Pleomorphic,
Gram-positive thin rods that may form long filaments or short rods
Arranged singly, in short chains, or in a V shape

7. Laboratory Diagnosis: Erysipelothrix rhusiopathiae
Identification
Catalase, nitrate, urease negative
Nonmotile
Production of H2S on TSI
Test tube brush growth in semisolid motility media

8. Characteristics of Corynebacterium, Listeria, and Erysipelothrix

9. Lactobacillus resistant to vancomycin (helps in diagnosis)
Widely distributed in nature
Normal flora of mouth, GI tract and female genital tract
Treat with pencillin plus an aminoglycoside
resistant to vancomycin (helps in diagnosis)
Clinical Infections
Bacterial vaginosis
Bacteremia, endocarditis, meningitis (rare)

10. Lactobacillus Colony Morphology Lab Diagnosis
Microscopic Morphology
Long, slender gram positive pleomorphic bacilli
Non-spore forming
Colony Morphology
SBA
Pinpoint
α- hemolytic or gamma colonies
Lab Diagnosis
Catalase negative

11. Gardnerella vaginalis
Member of the normal flora of the female genital tract
Associated with bacterial vaginosis
Foul odor
Vaginal pH > 4.5

12. Laboratory Diagnosis: Gardnerella vaginalis
Wet Prep
Look for clue cells
Large epithelials with various bacterial types on edges
Gram stain
Small, thin
Gram variable rods

13. Laboratory Diagnosis: Gardnerella vaginalis
Cultural Characteristics
Growth on BAP, CA
No growth on MAC
Human blood bilayer tween “V” agar
Beta-hemolytic
Requires a CO2 environment
Catalase negative

14. References
Engelkirk, P. G., & Duben-Engelkirk, J. (2008). Laboratory Diagnosis of Infectious Diseases: Essentials of Diagnostic Microbiology . Baltimore, MD: Lippincott Williams & Willkins.
Kiser, K. M., Payne, W. C., & Taff, T. (2011). Clinical Laboratory Microbiology: A Practical Approach . Upper Saddle River, NJ: Pearson Education, Inc.
Mahon, C. R., Lehman, D. C., & Manuselis, G. (2011). Textbook of Diagnostic Microbiology (4th ed.). Maryland Heights, MO: Saunders.