Listeria monocytogenes and Erysipelothrix rhusiopathiae, Lactobacillus genus and Bifidobacte- rium. Pre- and probiotics.

Question 1

General features and habitat of listeria Monocytogenes

Answer 1

Gram +
Rod shape
Motile- flagella is causing tumbling motility only
Habitat- intestine of animals (ubiquitous)

Question 2

Biochemical Properties of listeria Monocytogenes

Answer 2

Catalase +
CAMP +
Capsule

Question 3

Pathogenesis of listeria Monocytogenes

Answer 3

Contaminates unpasteurized milk, cheese and deli meat (can tolerate high salt concentration)

Resistant to cold temperature- can even contaminate frozen food (i.e. in fridge)

Transmitted by contaminated food or trans-placental infection to newborn

Facultative intracellular- can enter macrophages and enterocytes

Adhesion to the cells by Internalin A / Internalin B

Bacteria enter by phagosome, then lyses the phagosome membrane by
listeriolysin O (hemolysin) and is released into the cytosol

Replication of bacteria in cytosol


Propels itself to the next cell by polymerization of actin filaments in host’s cell

Actin filaments allows “jet” motility that enable the bacteria to travel from cell to cell Mechanism- Listeria surface protein ActA interacts with actin filament inside hosts’ cells

Question 4

Clinical Features (Listeriosis) of listeria Monocytogenes

Answer 4

Pregnant women are at risk- can cross placenta in septicemia with fever and chills
Can cause termination of pregnancy (spontaneous abortion or stillbirth)

Early onset (intrauterine infection)- granulomatosis infantiseptica (disseminated granulomas with central necrosis) and sepsis with high mortality

Late onset (2-3 weeks after birth)- meningitis or meningoencephalitis with sepsis

Meningitis or encephalitis in immunocompromised patients (> 60 years old)
Symptoms in healthy adults- vary from:
Asymptomatic, resembling mild flu, gastroenteritis, endocarditis and meningitis

Question 5

Diagnosis of listeria Monocytogenes

Answer 5

Beta-Hemolysis on Blood agar, isolation can be enhanced in 4C (“cold-enrichment”)

Gram staining- from CSF specimen on medium (it is usually negative)

Serology- ELISA to determine serological type (Ia, Ib, IVb)

PFGE- Pulsed-Field Gel Electrophoresis or phage typing

Question 6

Treatment of listeria Monocytogenes

Answer 6

Ampicillin with Gentamycin (added for immunocompromised patients)

Question 7

Prevention of listeria Monocytogenes

Answer 7

Pregnant women and immunocompromised patients should avoid raw and cold deli food

Question 8

General Features of Erysipelothrix rhusiopathiae

Answer 8

Gram +
Rod shape
Habitat- zoonosis (pigs)

Question 9

Pathogenesis of Erysipelothrix rhusiopathiae

Answer 9

Transmitted from animals (e.g. touch) or from animal products (no human-to-human transfer)

In humans:
Erysipeloid- mild cutaneous infection
Endocarditis (rarely)

In animals:
Erysipelas

Question 10

Clinical Features (Erysipeloid) of Erysipelothrix rhusiopathiae

Answer 10

Pain
Skin lesions without pus
Violaceus- purple spots on skin

Question 11

Diagnosis of Erysipelothrix rhusiopathiae

Answer 11

Cultivation on blood agar

Appear as small, transparent colonies

Question 12

Treatment of Erysipelothrix rhusiopathiae

Answer 12

Self-limiting (3-4 weeks) or Penicillin

Question 13

Prevention of Erysipelothrix rhusiopathiae

Answer 13

Vaccination of pigs, use gloves

Question 14

General Features of Lactobacillus (acidophilus or fermentum)

Answer 14

Gram +
Rod shape

Part of normal flora:
Oral cavity
Gut (intestine)
Vagina (Döderlein rods)

Question 15

Clinical Features of Lactobacillus

Answer 15

Used as Probiotic- benefits (health) the host and for making fermented food- lactose fermenter
Have a role in the pathogenesis of dental caries
Fermenting sugar into lactic acid which damage enamel

Rarely can cause: (as an endogenous pathogen) endocarditis, meningitis, cellulitis, orbital osteomyelitis, prostatitis, salpingitis, sepsis

Question 16

Diagnosis of Lactobacillus

Answer 16

Culture from CSF, amniotic fluid or exudate

Rogosa medium- anaerobic conditions with low pH (5.6-6.5 - acidic) and high glucose concentration. Also with yeast extract, manganese and magnesium

Blood agar- 5% CO2 for 24 hours.
Colonies are white-yellowish, round-shaped raised with “yogurt smell” (no hemolysis, few strains might be beta)

Question 17

Treatment of Lactobacillus

Answer 17

Dependent of susceptibility test, Vancomycin resistant

Question 18

Bifidobacterium features

Answer 18

Gram-positive, lactic acid forming bacteria.

They have been described as “friendly” bacteria in the intestine of humans.

Question 19

Bifidobacterium bifidum

Answer 19

The predominant bacterial species in the intestine of breast-fed infants, where it presumably prevents colonization by potential pathogens.

These bacteria are sometimes used in the manufacture of yogurts and are frequently incorporated into probiotics.

Question 20

Prebiotics:

Answer 20

Prebiotics are non-digestible foods that make their way through our digestive system and help good bacteria grow and flourish − Prebiotics keep beneficial bacteria healthy

Mostly come from carbohydrate fibers called oligosaccharides or resistant starch


Sources of oligosaccharides include fruits, legumes, and whole grains

Question 21

Probiotics

Answer 21

Live microorganisms administered in adequate amounts which confer a beneficial health effect on the host

Known as our “friendly bacteria”

Supplements with live active bacteria cultures

Found and used in the making of fermented foods (e.g. fermented food such as sauerkraut, yogurt, kefir, kombucha etc.)

Common strains include Lactobacillus and Bifidobacterium families of bacteria, but the yeast Saccharomyces cerevisiae and some E. coli or Bacillus species are also used as probiotics

Question 22

Function of pre and probiotics

Answer 22

Prebiotics and probiotics can restore the balance of bacteria in your digestive tract.

This can have vast advantages on our overall health- from sleeping better to mood and many more.