Listeria, Erysipelothrix

Listeria Classification – only one species of clinical significance – L. monocytogenes Morphology and general characteristics Small G+B which may appear pleomorphic Nonsporing Motile by peritrichous flagella at RT (umbrella motility) and polar flagella at 37 0 C.

Listeria Gram stain

Listeria umbrella motility at RT

Listeria Grows well on ordinary lab media. On CBA it produces beta hemolysis and colonies resemble Strep. pyogenes colonies Aerobic to microaerophilic Biochemistry Catalase + TSI= A/A, H 2 S- Esculin hydrolysis +

Listeria on CBA

Listeria CAMP + Grows in 6.5% NaCl Antigenic structure Four major serogroups (1-4) based on O antigen Serotypes based on H antigen Type 1b accounts for most infections although one may also find 1a and 4b in significant amounts

Listeria Virulence factors Monocytosis producing agent – is a lipid released by mechanical disruption of the cells. It causes a monocytosis to occur in the host Internalins (InlA)– are surface associated proteins that act to facilitate the uptake of the bacterium into epithelial cells. Oxygen labile hemolysin called listeriolysin (LLO) It is a pore forming toxin that facilitates the escape of the organism from the endosome to the cytosol

Listeria Phospholipase – is also involved in facilitating the escape of the organism from the endosome to the cytosol. Listeric polysaccharide – is a capsule component ActA – a surface protein that facilitates the rearrangement of actin to propel the organism through the cell and into an adjacent cell (organism is very invasive)

Listeria and actin polymerization

Listeria LPS-like substance – causes a high fever in the host Has a tropism for the CNS

Listeria invasion

Listeria Clinical significance In adults – disease is usually mild with flu-like symptoms or GI distress. Listeriosis Occurs in individuals with an underlying chronic primary disorder and is characterized by widely disseminated abscesses and granulomas. Lesions may be found in the liver, spleen, adrenals, respiratory tract, CNS,and skin. Meningitis with septicemia and pneumonia and a high mortality rate may occur.

Listeria Pregnancy renders an individual more susceptible to the infection, though the effect on the mom is usually minimal. It can be devastating for the fetus or newborn. In neonates, the disease occurs in two forms Early onset – the infant is infected transplacentally with the production of septicemia and granulomatous foci in many organs. This may result in abortion, stillbirth, premature delivery, or death soon after birth. The baby is born with cardio and respiratory distress, vomiting, diarrhea, meningitis, hepatosplenomegaly, and skin lesions. The fatality rate is 70-90% in untreated cases.

Listeria Late onset – the infant is infected from the genital tract during delivery. Infection usually begins 1-4 weeks after birth and is manifested as meningitis with a high fatality rate. Antimicrobic susceptibility/treatment Prognosis is poor in neonates so infected moms should be treated as soon as disease is diagnosed Penicillin is the drug of choice. Can also use erythromycin or tetracycline.

Erysipelothrix Classification – one species – E. rhusiopathiae Morphology and cultural characteristics Pleomorphic, small G+B Nonsporing and is related to Listeria Growth on CBA – produces alpha or gamma hemolysis. May form two types of colonies Smooth – contains rods and coccobacilli Rough – contains long, thin filaments Grows on chocolate agar, but not as well as on CBA Usually requires 48 hours for growth Microaerophilic with better growth in CO 2 or AnO 2 than in O 2

Erysipelothrix

Biochemistry Catalase – Nonmotile Esculin hydrolysis – TSI=A/A, H 2 S+ Virulence factors Adherence to heart valves Neuraminidase Hyaluronidase

Erysipelothrix Clinical significance Primarily a pathogen of swine, turkeys, and fresh water fish. In swine it primarily causes a cutaneous, reddish rash with occasional complications of septicemia, endocarditis, and arthritis. In man, the disease called erysipeloid is the most common form. It is an occupation associated disease in which a reddish- blue, edematous lesion at the site of inoculation, primarily following trauma to the hands. Occasionally the organism disseminates to cause septicemia, endocarditis, and arthritis.

Erysipeloid

Erysipelothrix Antimicrobial susceptibility Penicillin, tetracycline or erythromycin can be used