Basmah almaarik #Lab 7. Listeria monocytogenes is the only species that infect humans. Infection...
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Transcript of Basmah almaarik #Lab 7. Listeria monocytogenes is the only species that infect humans. Infection...
LISTERIA MONOCYTOGENESBasmah almaarik
#Lab 7
LISTERIA SPP. Listeria monocytogenes is the only
species that infect humans.
Infection most common in:Pregnant women still birthFetuses Newborns Immunocompromised individuals.
Specimen received: CSF.Blood.
LISTERIA MONOCYTOGENES MORPHOLOGY Gram Positive Bacilli Pleomorphic rods
(coccobacilli = short bacilli) can form chains.
Non-capsulated
CULTURE OF LISTERIA Aerobic and
facultative anaerobe.
Grow on Nutrient Agar: very light growth & give bluish coloration reflect blue light. Nutrient Agar
CULTURE OF LISTERIA On BA: small
translucent drop-like colonies (moist) with small zone of slight beta-hemaolysis
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.
HOW TO DIFFERENTIATE BETWEEN GROUP
B STREPTOCOCCUS AND LISTERIA?Listeria.
Catalase +ve.
CAMP +ve.
Group B Streptococcus.
Catalase –ve.
CAMP +ve (GBS)
HOW TO DIFFERENTIATE BETWEEN GROUP
D STREPTOCOCCUS AND LISTERIA
Listeria.
Catalase +ve.
Esculin Hydrolysis +ve
Group D Streptococcus
Catalase -ve.
Esculin hydrolysis +ve (GDS)
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 temperature
MOTILITY OF LISTERIA MONOCYTOGENES
Semisolid medium showing the typical "umbrella" growth.
Negative control non-
motile
Positive umbrella
like motility at Room
Temperature
MOTILITY TESTING USING WET PREPARATION Wet preparation examined under
microscope X40.
Slide + drop of saline examine under X40
Listeria monocytogenes Distinctive tumbling motility in a liquid medium @ 25 ºC
SUMMARY OF LISTERIA IDENTIFICATION USED IN THE LABORATORY
1. Gram stain (short gram positive rods)
2. Catalase +ve.
3. Slight beta-hemolysis on blood agar.
4. Umbrella like motility on semi-sold
media (soft agar) at room temperature.
•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:
YOUR WORK FOR TODAY: 1. Perform Gram Stain.2. Perform Catalase.3. Inoculate organism in soft agar to see
Umbrella like motility.
FOR DEMONSTRATION:4. See Listeria on blood agar.5. See listeria on Nutrient agar.6. See umbrella like motility in a soft agar.7. See gram stain of Listeria.