Staphylococcus

Staphylococcus (pl. Staphylococci) is a genus of spherical, gram-positive bacteria which occur in grape-like clusters. They are natural part of skin flora in most mammals and birds; they normally colonize the upper respiratory, alimentary and urogenital tracts. They are also the most common cause in pus-forming infections. At least 48 species of staphylococci have been recognized by biochemical analysis, most of them with a preference for a specific host. Eleven of these can be isolated from humans as commensals. S. aureus (nares) and S. epidermidis (nares, skin) are common commensals and also have the greatest pathogenic potential.1,3

Not all staphylococci are equally important as pathogens. Thus, in veterinary medicine, the most important species are S. aureus, S. hyicus, and S. intermedius. They are a common and important cause of disease in animals, including abscesses, dermatitis, furunculosis, meningitis, osteomyelitis, food poisoning, and wound infections.3

Staphylococcus aureus

Staphylococcus aureus is one of the most important human and veterinary pathogen, and its occurrence, pathology, and drug resistance (penicillin resistance) have been studied intensively.

Staphylococci can cause many forms of infection.

  1. Superficial skin lesions (boils, styes) and localized abscesses in other sites.
  2. Deep-seated infections, such as osteomyelitis and endocarditis and more serious skin infections (furunculosis).
  3. Hospital acquired (nosocomial) infection of surgical wounds.
  4. Food poisoning by releasing enterotoxins into food.
  5. Toxic shock syndrome by release of superantigens into the blood stream.
  6. S. saprophiticus causes urinary tract infections.
Staphylococcus aureus
Staphylococcus aureus
Source: CDC

Transmission

Ruminants carry staphylococcal strains on their skin. In poultry, S. aureus has been isolated from skin, nares, chick fluff, and air in poultry houses. Rabbits may be carriers of S. aureus strains found on flying hairs, cage materisl, and food chains.

Dogs may be carriers of S. pseudintermedius in the nares, throat, and on the anal ring. The same strains may be found in the nares of the dog owner.

Other species of staphylococci (S. lugdunensis, S. haemolyticus, S. warneri, S. schleiferi, S. intermedius) are infrequent pathogens.2

Antimicrobial Resistance

Since the beginning of the antibiotic era S. aureus has responded to the introduction of new drugs by rapidly acquiring resistance by a variety of genetic mechanisms. Hospital strains of S aureus are often resistant to many different antibiotics. Indeed strains resistant to all clinically useful drugs, apart from the glycopeptides vancomycin and teicoplanin, have been described.2,3

According to Dr. Eric P. Skaar, "Staph is the worst infectious threat to public health. It is the No. 1 cause of heart infections and skin infections, the No. 1 cause of soft tissue infections. It is a big cause of pneumonia. It is the No. 1 hospital acquired infection." Like all organisms, needs iron, and Dr. Skaar wondered how it got it. The answer, he discovered, is that the bacteria "pop open red blood cells and grab the iron." Dr. Skaar and his colleagues found the protein on staph that attaches to hemoglobin and discovered that it grabs onto segments of the blood protein that are specifically in humans. It can attach to similar segments in animal hemoglobins, but less avidly. He expects that if there are variations among human hemoglobins that determine genetic susceptibility to staph, he is likely to find them.



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Staphylococcus hyicus

In pigs, Staphylococcus hyicus causes exudative epidermatitis (greasy pig disease), a relatively rare infection of the skin characterized by greasy peeling skin and blister formation. It has also been reported to cause joint infections and cystitis in pigs. 10 Resistance to Staphylococcus hyicus is very high, especially to penicillin, streptomycin, and tetracyclin, as well as to macrolides antibiotics.3

Staphylococcus intermedius

Staphylococcus intermedius is part of natural skin flora of all canids. In dogs, Staphylococcus intermedius is a common cause of pyoderma (bacterial infection) and otitis following skin injuries. These infections are commonly treated with antimicrobial drugs. Recent studies identified a new staphylococcus species S. pseudintermedius. Some researchers suggest that all canine and some equie staphylococci previously identified as S. intermedius should be considered to be S. pseudintermedius.

References

  1. DNA Vaccines against Bacterial Pathogens
  2. NCBI » Bookshelf » Medical Microbiology
  3. Antimicrobial resistance in bacteria of animal origin. Frank M. Aarestrup
  4. Pathogenesis of Bacterial Infections in Animals. Carlton L. Gyles, John F. Prescott, Glenn Songer, Charles O. Thoen

 

 

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