monocytogenes Basmah almaarik Lab 7 Listeria spp Listeria monocytogenes is the only species that infect humans Infection most common in Pregnant women still birth Fetuses ID: 332783
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Slide1
Listeria monocytogenes
Basmah
almaarik
#Lab 7Slide2
Listeria spp.
Listeria
monocytogenes
is the only species that infect humans.
Infection most common in:
Pregnant women
still birth
Fetuses
Newborns
Immunocompromised
individuals.
Specimen received:
CSF.
Blood.Slide3
Listeria monocytogenes
morphology
Gram Positive Bacilli
Pleomorphic
rods (coccobacilli = short bacilli) can form chains.Non-capsulatedSlide4
Culture of listeriaAerobic and facultative anaerobe.
Grow on Nutrient Agar: very light growth & give bluish coloration
reflect blue light.
Nutrient AgarSlide5
Culture of listeria
On BA: small translucent drop-like colonies (moist) with small zone of slight beta-
hemaolysisSlide6
Culture of listeria
Can grow at refrigeration temperature (4 ˚C)
Temperature range for growth is 3 – 45 ˚C; with an optimum of
30 ˚C.
24 h.Slide7
How to differentiate between Group B streptococcus and
listeria
?
Listeria
.
Catalase +
ve.CAMP +ve.
Group B Streptococcus.
Catalase
–
ve
.
CAMP +
ve
(GBS)Slide8
How to differentiate between Group D streptococcus and
listeria
Listeria
.
Catalase
+ve.
Esculin Hydrolysis +ve
Group D Streptococcus
Catalase
-
ve
.
Esculin
hydrolysis +
ve
(GDS)Slide9
How to differentiate between corynebacterium and
listeria
?
Listeria
Short gram positive rods, can occur as
diplobacilli or in short chain.
Catalase +ve.Motile at room temperature
25 ºC
Corynebacterium
spp.
Polymorphic gram positive rods.
Catalase +
ve
.
Non motile at any temperatureSlide10
Motility of Listeria
monocytogenes
Semisolid medium showing the typical "umbrella" growth.
Negative control non-motile
Positive umbrella like motility at Room TemperatureSlide11
Motility testing using wet preparationWet preparation examined under microscope X40.
Slide + drop of saline
examine under X40
Listeria
monocytogenes
Distinctive tumbling motility in a liquid medium
@
25 ºCSlide12
Summary of Listeria identification used in the laboratory
Gram stain (short gram positive rods)
Catalase
+
ve
.
Slight beta-hemolysis on blood agar.Umbrella like motility on semi-sold media (soft agar) at room temperature. Slide13
Keep your refrigerator clean and cold—below 40° F.
Refrigerate or freeze food within two hours.
Thoroughly cook meat and poultry.
If you just can’t resist the idea of a pastrami and Swiss, be sure to heat the meat until steaming to kill bacteria.
Separate uncooked meats from other foods.
Eat only pasteurized dairy products.
Avoid soft cheeses like feta .
Don't eat refrigerated meat or seafood spreads, and smoked seafood
For Pregnant women and others at higher risk for
Listeriosis
: Slide14
Your Work For Today: Perform Gram Stain.
Perform
Catalase
.
Inoculate organism in soft agar to see Umbrella like motility.
For demonstration:See Listeria
on blood agar.See listeria on Nutrient agar.See umbrella like motility in a soft agar.
See gram stain of
Listeria
.