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.