Listeria monocytogenes and Erysipelothrix rhusiopathiae, Lactobacillus genus and Bifidobacte- rium. Pre- and probiotics. Flashcards
General features and habitat of listeria Monocytogenes
Gram +
Rod shape
Motile- flagella is causing tumbling motility only
Habitat- intestine of animals (ubiquitous)
Biochemical Properties of listeria Monocytogenes
Catalase +
CAMP +
Capsule
Pathogenesis of listeria Monocytogenes
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
Clinical Features (Listeriosis) of listeria Monocytogenes
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
Diagnosis of listeria Monocytogenes
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
Treatment of listeria Monocytogenes
Ampicillin with Gentamycin (added for immunocompromised patients)
Prevention of listeria Monocytogenes
Pregnant women and immunocompromised patients should avoid raw and cold deli food
General Features of Erysipelothrix rhusiopathiae
Gram +
Rod shape
Habitat- zoonosis (pigs)
Pathogenesis of Erysipelothrix rhusiopathiae
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
Clinical Features (Erysipeloid) of Erysipelothrix rhusiopathiae
Pain
Skin lesions without pus
Violaceus- purple spots on skin
Diagnosis of Erysipelothrix rhusiopathiae
Cultivation on blood agar
Appear as small, transparent colonies
Treatment of Erysipelothrix rhusiopathiae
Self-limiting (3-4 weeks) or Penicillin
Prevention of Erysipelothrix rhusiopathiae
Vaccination of pigs, use gloves
General Features of Lactobacillus (acidophilus or fermentum)
Gram +
Rod shape
Part of normal flora:
Oral cavity
Gut (intestine)
Vagina (Döderlein rods)
Clinical Features of Lactobacillus
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
Diagnosis of Lactobacillus
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)
Treatment of Lactobacillus
Dependent of susceptibility test, Vancomycin resistant
Bifidobacterium features
Gram-positive, lactic acid forming bacteria.
They have been described as “friendly” bacteria in the intestine of humans.
Bifidobacterium bifidum
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.
Prebiotics:
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
Probiotics
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
Function of pre and probiotics
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.
