Module 4

Question 1

What is the cellular morphology of Listeria?

Answer 1

Gram pos rods, longer bacillary forms in broth cultures

Question 2

What is the only pathogenic species of Listeria?

Answer 2

L. monocytogenes

Question 3

What are the characteristics of L. monocytogenes?

Answer 3

Motile with peritrichous flagella, no spores or capsules

Facultative anaerobe

Grows well in nutrient broth and nutrient and blood agar

Colonies resemble group B Strep

Small beta hemolysis

Grey/white, 0.5-2mm

Question 4

What is the ID for L. monocytogenes?

Answer 4

Catalase pos

Motility pos- tumbling end over end

BEA pos

Hippurate hydrolysis pos

cAMP reaction pos (rectangular area)

Sometimes cross reacts with group B Strep antisera

Question 5

What is the pathogenicity of L. monocytogenes?

Answer 5

Serious neonate infection, generalized infection after birth

Late form of neonatal infection, evident after 5 days, meningitis

Immunosuppressed patients- meningitis, pneumonia, septicaemia, endocarditis

Question 6

What is the antimicrobial susceptibility of L. monocytogenes?

Answer 6

Sensitive to penicillin, ampicillin, erythromycin, aminoglycosides

Often treated with a combo of penicillin and aminoglycoside

Question 7

What are the characteristics of Lactobacillus?

Answer 7

Normal flora, rare infections

Gram pos, nonmotile

Microaerophilic- scant growth when incubated in CO2

Often overgrown by other bacteria

Question 8

What is the pathogenicity of Lactobacillus?

Answer 8

Rare- few reports of endocarditis and meningitis

Normal flora of mucous membranes

Seen in healthy GI tract and vaginal mucosa

Question 9

When does Lactobacillus appear in vaginal flora?

Answer 9

2-3 days after birth, maternal estrogen induces glycogen deposition which induces colonization (acidic pH)

Once maternal estrogen is gone, no more glycogen, no more lactobacilli

Estrogen increases at puberty again

Question 10

How many species of Listeria are there?

Answer 10

8