REGULAR, NON-SPORING, GRAM-POSITIVE RODS

A General Introduction has been added to each disease chapter in an attempt to give a brief updated overview of the taxonomic, biological and other characteristics of the virus family or group of bacteria /protozoa that cause disease in livestock and, where relevant, involve wildlife. As the text of the three-volume book Infectious Diseases of Livestock is currently under revision the Editors are aware that there are inconsistencies between the updated introductions to chapters and the content of the chapters themselves. Once the chapters have been updated – a process that is currently underway – these inconsistencies will be removed.

This group of bacteria contains seven genera which do not belong to the same family. They are all rod-shaped, Gram positive, non-sporing and non-pigmented, and grow in complex media, but besides these have few common characteristics. ² Only two of the seven genera, namely Listeria and Erysipelothrix, are of veterinary importance.

Bacteria of the genus Listeria are widely distributed in nature, and may be isolated from the soil, water, vegetation, animal biological products, and human and animal carriers throughout the world.³ Two species of Listeria (L. monocytogenes and L. ivanovii) have been associated with disease in humans and animals. Of the three, L. monocytogenes is more common, and infections are usually sporadic. Different disease syndromes (septicaemia, meningoencephalitis, and abortions) may occur in infected animals and humans. Listeria ivanovii is rarely encountered, and has only been associated with abortions in sheep.²

The genus Erysipelothrix consists of three species; E. rhusiopathiae and the environmental E. inopinata being the only recognized species (formerly E. rhusiopathiae serotypes 3, 7, 10, 14, 20, 22 and 23).⁴ The species in this genus can be differentiated from Listeria spp. in that they are catalase negative, have the ability to produce hydrogen sulphide and show alpha but not beta-haemolysis on blood agar. Biochemically, E. tonsillarum is distinguished from E. rhusiopathiae by its ability to ferment sucrose. The bacteria are highly resistant and remain viable and infective even after being subjected to the effects of processes such as putrefaction or the curing of meat by smoking or pickling. Infections by E. rhusiopathiae are ubiquitous and affect humans and a large variety of animals, including cattle, sheep, horses, mice and various species of birds and fish. However, the bacterium is recognized particularly as a pathogen of pigs; it is responsible for the disease known as swine erysipelas or diamond skin disease. Erysipelothrix rhusiopathiae is one of the causes of fibrinopurulent polyarthritis in lambs, which results from the contamination of wounds (such as umbilical, castration and docking wounds).

It is also a cause of post-dipping lameness in sheep, which is an acute, deep dermatitis of the lower limbs, and infection being contracted by the cutaneous route in animals that have been dipped in contaminated dipping fluids not containing antibacterial substances. Disease in poultry caused by E. rhusiopathiae is usually an acute, fulminant infection of individuals within a flock, and is accompanied by a reduction in egg production. Humans usually contract E. rhusiopathiae infection while handling infected meat or fish, and develop a disease known as erysipeloid, which manifests either as a localized skin rash or septicaemia.¹ Erysipelothrix tonsillarum has been isolated from numerous water and animal sources as well as the tonsils of healthy pigs. It is considered to be nonpathogenic.⁴

References

1. BRICKER, J.M. & SAIF, Y.M., 1991. Erysipelas. In: calnek, b.w., barnes, h.j., beard, c.w., reid, w.m. & yoder, h.w., (eds). Diseases of Poultry. Ames, Iowa: Iowa State University Press.
2. KANDLER, O. & WEISS, N., 1986. Regular non-sporing Gram-positive rods. In: sneath, p.h.a., mair, n.s., sharpe, m.e. & holt, j.g., (eds). Bergey’s Manual of Systematic Bacteriology. Baltimore: Williams & Wilkins.
3. SEELIGER, H.P.R. & JONES, D., 1986. Genus Listeria Pirie 1940. In: sneath, p.h.a., mair, n.s., sharpe, m.e. & holt, j.g., (eds). Bergey’s Manual of Systematic Bacteriology. Baltimore: Williams & Wilkins.
4. TAKANASHI, T., FUJISAWA, T., TAMURA, Y., SUZUKI, S., MARAMATSU, M., SAWADA, T., BENNO, Y. & MITSUOKA, T., 1992. DNA relatedness among Erysipelothrix rhusiopathiae strains representing all twenty-three serovars and Erysipelothrix tonsillarum. International Journal of Systematic Bacteriology, 42, 469–473.