BACTERIOLOGY OF LISTERIA

 What is Listeria?

Listeria is a group of aerobic bacteria belonging to the family (Corynebacteriaceae) containing small coccid Gram positive rod,  found on the feces of humans and other animals, on vegetation and on silage and  parasitic on poikilothermic and warm blooded animals including man.

Listeriosis

This is a disease of man and animal cause the bacterium Listeria monocytogenes, especially in pregnant women or inimmunocompromised individuals.

Listeria, is a bacterium genus made up of three species, named after Joseph Listeria, an Englishman  who discovered Sterile surgery.  They are a group of Gram+ bacillus, typified by Listeria monocytogene, the organism that causes Listeriosis.

   SPECIES OF LISTERIAS

a. Listeria grual

b. Listeria innocua

c. Listeria ivanovii

d. Listeria monocytogen

e. Listeria seeligeri

f. Listeria murraci

EPIDERMOLOGY: Listeria is the causative agent of listerosisa serious infection caused by eating food contaminated with the bacteria, the disease affect primarily pregnant women, newborn, and adult with the weakened immune system. It has low ability to cause infection. It can become contaminated from the soil and animal can become carriers and has been found in uncooked meats, uncooked vegetable, unpasteurized milk, food made unpasteurized milk and processed foods. Pasteurization and effective cooking kills  the bacteria, however, contamination may occur after cooking.

PATHOGENESIS: Listeria is hard and able to grow in temperature ranging from 4^0C(32^0f) the temperature of a refrigerator to 37^0C(99^0f) the body internal temperature. Listeria uses the cellular machinery to move around inside the host cell, it includes directed polymerization of action transmembrane protein thus pushing bacteria cells around. An example is Listeria monocytogen which encode virulence gene that are thermo regulated. Temperature of the host cells meet the structure and allow translation initiation for the virulence gene.

CLINICAL MANIFESTATION: Clinical manifestation of listeria include, sepsis and meningitis, meningitis is often complicated by encephalitis. It may affect newborn due to it ability to penetrate endothelial layer of the placenta.

MICROSCOPIC EXAMINATION: Listeria species appear as small gram positive rod which are sometimes arranged in short chains. In direct smear they may be coccoid, so they can be mistaken for streptococci longer cells or may resemble cornea bacteria, flagella are produced at room temperature but not at 35^0C. hemolytic activity on blood agar has been used to distinguish Listeria monocytogen among other species of the organism, but it is not an absolutely defining criteria. Further biochemical characterization may be necessary to distinguish between the different species as gram positive, none spore forming, catalase positive rod etc.

PREVENTION:The prevention of Listeria as a food illness involves effective sanitation of food contact surfaces. Alcohol has proven to be an effect topical sanitizer against Listeria quaternary. Ammonia could be used with alcohol as a food contact safe sanitizer with increased duration of sanitizing action. Refrigerated food should be kept at temperature below 4^0C to discourage bacteria growth.

TREATMENT: antibiotic effective against the bacteria species include, Ampicillin, Vancomycin, Ciprofloxacin, Linezolid, Azithromycin, Listexploo and bacteriophages.

REFERENCES: Farber, peterkin, p.c September 1991 (listeria monocytogen a food pathogen.)

American society for microbiology 55(3). 476 – 311.

Microbiol Rev

v.55(3); 1991 Sep

PMC372831