Erysipelothrix rhusiopathiae is a Gram-positive, catalase-negative, rod-shaped, non-spore-forming, nonacid-fast, nonmotile bacterium. Distributed worldwide, E. rhusiopathiae is primarily considered an animal pathogen, causing the disease known as erysipelas that may affect a wide range of animals. Pigs, turkeys and laying hens are most commonly affected, but cases have been reported in other mammals, birds, fish, and reptiles. In pigs, the disease is known as diamond skin disease. The bacterium can also cause zoonotic infections in humans, called erysipeloid. The human disease called erysipelas is not caused by E. rhusiopathiae, but by various members of the genus Streptococcus.

History

Erysipelothrix rhusiopathiae was first isolated by Robert Koch in 1876. A few years later the bacterium was recognised as the cause of erysipelas in pigs and in 1884 the organism was first established as a human pathogen. In 1909, the genus was named Erysipelothrix. In 1918 the name Erysipelothrix rhusiopathiae was introduced and in 1920 it was designated as the type species of the genus.

Epidemiology

Erysipelothrix rhusiopathiae may be isolated from soil, food scraps, and water contaminated by infected animals. It can survive in soil for several weeks. In pig faeces, the survival period of this bacterium ranges from 1 to 5 months.

Erysipeloid is transmitted by several animals, particularly pigs, in which the disease (very common in the past) has several names (swine erysipelas in English, rouget du porc in French and mal rossino in Italian). Urticaria-like lesions, arthralgia, arthritis, endocarditis, and sepsis are the most characteristic features of swine erysipelas. Other animals that can transmit the infection are sheep, rabbits, chickens, turkeys, ducks, emus, scorpion fish, and lobsters.

Erysipeloid is an occupational disease, mainly found in animal breeders, veterinarians, slaughterhouse workers, furriers, butchers, fishermen, fishmongers, housewives, cooks, and grocers. One epidemic of erysipeloid was described in workers involved in manufacturing buttons from animal bone.

Clinical disease

Humans

In humans, E. rhusiopathiae infections most commonly present in a mild cutaneous form known as erysipeloid.

It occurs most commonly as an occupational disease. The disease is characterized clinically by an erythematous oedema, with well-defined and raised borders, usually localized to the back of one hand and/or fingers. The palms, forearms, arms, face, and legs are rarely involved.

Poultry

The bacterium has been isolated from a wide range of avian species and differences in susceptibility depending on species have been suggested. Erysipelas outbreaks have been reported in almost all poultry species. Historically, erysipelas has been considered a disease of significant importance primarily in turkeys. However, an increasing number of outbreaks in laying hen flocks have been reported in several countries. Signs seen during an outbreak of erysipelas in a laying hen flock include sudden onset of high mortality and egg production losses.

Muskox

Due to unregulated hunting of muskox the species was almost wiped out in the late 19th century. However, by 1917 regulations were in place and the herds began to recover to such an extent that regulated hunting was permitted in the 1980s. By the 1990s hunters were permitted to take 10,000 muskox on Banks Island alone and in 2001 it was estimated that there were more than 68,000 muskox on the island making it the largest population in the world. However, since then the numbers have dropped by 70% due to E. rhusiopathiae.

Virulence factors

Various virulence factors have been suggested as being involved in the pathogenicity of E. rhusiopathiae. The presence of a hyaluronidase and neuraminidase has been recognized, and neuraminidase was shown to play a significant role in bacterial attachment and subsequent invasion into host cells. The role of hyaluronidase in the disease process is controversial. The presence of a heat-labile capsule has been reported as important in virulence. As implemented in that instance by MicroGen DX (Lubbock, TX), E. rhusiopathiae could be detected by targeted amplification and sequencing of the 16S rRNA gene which is useful for broad characterization of bacterial pathogens in a clinical sample. The method may be especially beneficial for rapid identification or confirmation of atypical pathogens in human infection such as Erysipelothrix.

Treatment

Humans

Penicillin is the treatment of choice for both disease states in humans. E. rhusiopathiae is sensitive in vitro and in vivo mainly to penicillins, but also to cephalosporins (cefotaxime, ceftriaxone), tetracyclines (chlortetracycline, oxytetracycline), quinolones (ciprofloxacin, pefloxacin), clindamycin, erythromycin, imipenem, and piperacillin. It is resistant to vancomycin, chloramphenicol, daptomycin, gentamicin, netilmicin, polymyxin B, streptomycin, teicoplanin, tetracycline, and trimethoprim/sulfamethoxazole. Penicillins and cephalosporins are the first-line choices for treatment. A 7-day course is appropriate, and clinical improvement is usually observed 2–3 days after the beginning of the treatment. Penicillin is the drug of choice for treatment of poultry, however the disease may reoccur. Therefore, antibiotic treatment may be combined with vaccination.

References

  • Type strain of Erysipelothrix rhusiopathiae at BacDive - the Bacterial Diversity Metadatabase