quarta-feira, 13 de abril de 2011

Staphylococcus xylosus

Staphylococcus xylosus is a species of bacteria belonging to the genus Staphylococcus. It is a Gram-positive bacterium that forms clusters of cells. Like most staphylococcal species, it is coagulase-negative and exists as a commensal on the skin of humans and animals and in the environment.

It appears to be far more common in animals than in humans. S. xylosus has very occasionally been identified as a cause of human infection, but in some cases it may have been misidentified.

IdentificationS. xylosus is normally sensitive to fleroxacin, methicillin, penicillin, teicoplanin, tetracycline and resistant erythromycin and novobiocin. It is highly active biochemically, producing acid from a wide variety of carbohydrates.

Acid and gas are produced from D-(+)-galactose, D-(+)-mannose, D-(+)-mannitol, maltose and lactose. Caseinolytic and gelatinase activities are normally present.

It normally produces slime but not capsules. This ability is lost upon subculture. Cell wall peptidoglycan similar to L-Lys-Gly3-5. L-Ser0.6-1.5 type found in predominately human species

Clinical importanceStaphylococcus xylosus has been associated with the following conditions:

Nasal dermatitis in gerbils
Pyelonephritis in humans
Avian staphylococcosis
Bovine intermammary infection
It is also found

In milk, cheese & sausages
On skin of many animals

REF: http://en.wikipedia.org/wiki/Staphylococcus_xylosus Acesses: 13/04/11

Staphylococcus xylosus is a Gram positive bacterium with a low G + C content. It belongs to the coagulase-negative group of staphylococci. It is a commensal bacterium of the skin which is of major interest for several reasons.
This bacterium is used as a fermenting agent in the production of meat (sausage) and milk (cheese) products. It contributes to the development of the red color characteristic of sausages through its nitrate reductase activity (photo 1) and to the orange color on the surface of certain cheeses, since some strains of S. xylosus are pigmented (photo 2).

This bacterium is mentioned as a dominant species in production facilities. Some strains of S. xylosus are capable of colonizing surfaces by forming biofilms (photo 3).
There is a great diversity of strains within this species. As a result of this diversity, certain strains isolated from milk and raw ham produce enterotoxins D, C or E, and as such may present a risk for the consumer. Other strains of S. xylosus are opportunistic pathogens of animals. Strains of S. xylosus, some of which have been isolated in nosocomial infections, have been described as multi-resistant to diverse antibiotics.

The genome of S. xylosus is estimated at 2.8 Mb. The complete sequence of this genome will lead to the establishment of the genetic bases of the specific properties of this species in comparison with the genomes of other staphylococci: S. aureus, S. epidermididis and S. carnosus. It will also make it possible to identify the genetic bases for the adaptation of this bacterium to the agro-alimentary environment, and functions of technologic interest. The stud of the genome of S. xylosus will make it possible to evaluate the innocuousness of the strains used as fermenting agents.

REF: http://www.cns.fr/spip/Staphylococcus-xylosus-commensal.html Access: 13/04/11

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