STAPHYLOCOCCUS INFECTIONS

STEPHANIE SPECK

Bundeswehr Institute of Microbiology, Department of Virol­ogy and Rickettsiology, Munich, Germany

Staphylococci are commonly associated with suppurative pyogenic infections, abscess formation and skin infection.

Staphylococci are Gram-positive bacteria (0.5-1.5 μm in diameter), which occur singly, in pairs, tetrads, short chains of three to four cells, and in irregular clusters or ‘bunches of grapes’. Most staphylococci are catalase­positive facultative anaerobes, oxidase- negative and non- motile. Forty species of the genus Staphylococcus have been identified, ten of which contain a subdivision with subspe­cies designation¹-¹⁹).

Staphylococcus infection may result in a variety of disease conditions, including pyogenic skin infections, abscess for­mation, mastitis, septicaemia and toxic-shock syndrome.

Staphylococci commonly colonize the skin, skin glands, and mucous membranes of a wide range of animal species and humans. In addition, they can be found in the intes­tinal, genitourinary, and upper respiratory tract. They occur worldwide and have evolved with their host species to some degree. Different animal species harbour a differ­ent staphylococcal flora; hence, from a veterinary perspec­tive, distinguishing between host-associated groups of Staphylococcus strains can be useful. Although different Staphylococcus spp.

Staphylococci can be divided into two groups: ‘major’ and ‘minor’ pathogenic species. Formerly, the old terms ‘coagulase-positive’ and ‘coagulase-negative’ were used to distinguish between pathogenic and less pathogenic species and coagulase-production still continues to be widely used as criterion for the identification of pathogenic staphylo­cocci associated with acute infections. The major patho­genic staphylococci in veterinary medicine are mentioned above. The group of minor pathogenic species consists of e.g. S. epidermidis, S. warneri, S. delphini, S. schleiferi subsp. coagulani, S. pseudintermediui, S. caprae, S. haemo- lyticus, S. scuiri. Several potential virulence factors have been described as important for Staphylococcui infection. Most of these factors have been studied in S. aureui but have also been reported in S. intermedius and others. These factors can be divided into cell-associated components (Protein A, capsular polysaccharides, peptidoglycan, lipoteichoic acid, adhesins), exoenzymes (coagulase, lipase, hyaluronidase, hyaluronate lyase, proteases), and exotoxins (toxic-shock syndrome toxin (TSST-1), enterotoxins, epi- dermolytic toxins, haemolysins, leucocidin)⁽²⁸⁾.

Types of disease and pathologic changes in free-ranging and captive wildlife are given in Table 37.1. In hares (Lepus spp.), abscesses caused by Staphylococcus sp.

Specimens for diagnosis may include exudates, pus, milk, skin swabs and affected tissues. Direct microscopy of Gram-stained smears may show Gram-positive cocci in the typical ‘bunches of grapes’ formation. Staphylococci can be grown easily on Columbia sheep blood agar con­taining 5% blood.

It is certain that food animals or pets might be a source of human Staphylococcus infection, but humans may also serve as cause of infection in wild animals. A study on the Spanish imperial eagle (Aquila adalberti) revealed human-associated Staphylococcus infection in nestlings handled for wildlife conservation purposes. Chicks handled without disposable gloves showed a higher infec­tion rate (45%) compared with those handled with gloves (4%)⁽²⁹⁾. It is strongly recommended that people handling wildlife (casualties) should implement proper hygiene measures to prevent mutual transmission of staphylococci and other zoonotic pathogens. In captivity, particularly in breeding facilities, strict hygiene measures should be implemented.