1. Corynebacterium and Other Non–Spore-forming Gram-Positive Rods
Corynebacterium sp.
Listeria monocytogenes
Erysipelothrix rhusiopathiae

2. Case Study A 76-year-old woman is receiving corticosteroid therapy
Complained of fever and headache for 7 days
CBC count showed an elevated white cell count
CSF analysis showed
250 WBC/cu mm
Glucose 30 mg/dL
Protein 180 mg/dL
Culture grew beta-hemolytic colonies on sheep blood agar, gram-positive pleomorphic rods
Catalase positive, motile at room temperature
CAMP-factor positive

3. Points to Consider
What type of infection was suspected in this particular patient?
What predisposing risk factors were presented by the patient?
How are these organisms differentiated from other groups with similar characteristics?
What clinical forms of infections are associated with these groups of organisms?
Other points to consider

4. Corynebacterium Species: General Characteristics
Morphology
Gram-positive, non–spore-forming rods
Arrange in palisades: “L-V” shape; “Chinese characters”
Pleomorphic: “club-ends”

5. Corynebacterium Species
General characteristics
Found as free-living saprophytes
Members of the usual flora of humans and animals
Corynebacterium diphtheriae is the most significant pathogen
Other species may cause infections in the immunocompromised hosts

6. Other Corynebacteria Significant Corynebacterium species
C. xerosis
C. pseudodiphtheriticum
C. pseudotuberculosis
C. jekeium
C. ulcerans
Rhodococcus equi
Arcanobacterium haemolyticum

7. C. diphtheriae: Agent of Diphtheria
Toxigenic Corynebacterium diphtheriae
Worldwide distribution
rare in places where vaccination programs exist
Exotoxin as the virulence factor
Diphtheria toxin
Toxin is produced by certain strains
Lysogenized by bacteriophage with toxin gene (tox+)
Toxin is antigenic

8. Toxigenic Corynebacterium diphtheriae
Toxin consists of two fragments
A: Active fragment
Inhibits protein synthesis
Catalyzes transfer of ADPR to link with EF ADPR.EF (inactive)
Leads to cell/tissue death
B binds to specific cell membrane receptors
Binds to specific cell membrane receptors
Mediates entry of fragment A

9. Clinical Forms of Diphtheria
Respiratory
Acquired by droplet spray
Unimmunized individuals are susceptible
Nonrespiratory
Systemic
Skin and cutaneous forms

10. C. diphtheriae: Causative Agent of Diphtheria
Respiratory disease–diphtheria
Incubation period–2 to 5 days
Symptoms: sore throat, fever, malaise
Toxin is produced locally, usually in the pharynx or tonsils
Toxin causes tissue necrosis
Forms a tough grey to white pseudomembrane

11. Clinical Infections: Non-Respiratory Disease
Systemic infections
Toxin is absorbed in the blood stream and carried systemically
Affects the kidneys, heart, and nervous system
Death occurs due to cardiac failure

12. Clinical Infections: Non-Respiratory Disease
Cutaneous form
More prevalent in the tropics
Infections occur at the site of minor abrasions
Maybe superinfected with Streptococcus pyogenes and/or Streptococcus aureus

13. Laboratory Diagnosis Microscopic morphology
Gram-positive, non–spore-forming rods, club-shaped
Appear in palisades and give "Chinese letter" arrangement
Produce metachromatic granules or “Babes’ Ernst” bodies
Loeffler methylene blue stain of Corynebacterium sp.

14. Laboratory Diagnosis: Cultural Characteristics
Loeffler's slant or Pai's slant—Used to demonstrate pleomorphism and metachromatic granules; "Babes’ Ernst bodies"
Serum Tellurite or modified Tinsdale- brown or grayish to black halos around the colonies
Growth of C. diphtheriae on blood agar

15. Laboratory Diagnosis Identification Toxigenicity testing
Confirm identification by fermentation reactions
Toxigenicity testing
Elek test— Immunodiffusion test

16. Differentiating Characteristics of Corynebacterium Species

17. Listeria Monocytogenes: General Characteristics
Gram-positive, non–spore-forming rods
Widespread in nature
Known to infect a wide variety of animals
Human exposure is limited; direct or indirect
Transient colonization occurs without disease

18. Listeria monocytogenes: Clinical Infections
Adults
Septicemia/meningitis in the compromised/elderly
Mild flu-like syndrome in pregnant women could be fatal to fetus
Neonatal
Early onset from intrauterine transmission results in sepsis; high mortality rate
Late onset manifests as meningitis; lower mortality rate

19. Laboratory Diagnosis: L. monocytogenes
Identification
Microscopic morphology
Gram Positive non–spore-forming coccobacillary
Cultural characteristics
Grows well on blood agar; colonies produce a narrow zone of hemolysis similar to Group B Streptococcus

20. Laboratory Diagnosis: L. monocytogenes
Identification
Catalase positive
Motility:
Motile at 25o C; "umbrella" type
Tumbling motility in hanging drop preparations
“Umbrella” motility pattern (Left) typical for L. monocytogenes

21. Laboratory Diagnosis: L. monocytogenes
Identification
CAMP test
Produces a “block” type of hemolysis in contrast to “arrow”-shape produced by Group B Streptococcus
CAMP test with Listeria monocytogenes
Positive CAMP test for Group B Streptococcus

22. Differentiating Characteristics between L
Differentiating Characteristics between L. monocytogenes and Other Gram Positive Bacteria

23. Erysipelothrix rhusiopathiae: General characteristics
Gram positive, non–spore-forming, pleomorphic rods
Distributed in nature
Can cause disease in animals (swine, turkey, sheep)
Humans acquire the infection through occupational exposure

24. 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
Endocarditis
May occur in those who have had valve replacements
Disseminated infections may occur, but rarely

25. Laboratory Diagnosis: Erysipelothrix rhusiopathiae
Microscopy
Pleomorphic, gram-positive thin rods that may form long filaments, may be arranged singly, in short chains, or in a V shape

26. Laboratory Diagnosis: Erysipelothrix rhusiopathiae
Identification
Catalase negative
CO2 is required
Grows on blood or chocolate agar—colonies may appear gray or translucent with alpha hemolysis
Distinguishing characteristic: Production of H2S on TSI

27. Characteristics of Corynebacterium, Listeria, and Erysipelothrix

28. Points to Remember
Distinguishing characteristics of the genera Listeria, Corynebacterium, and Erysipelothrix from other gram positive bacteria
Clinical infections caused by each of these groups
Risk factors are associated with these infections
Biochemical and microscopic features of each of these species