The Genus Staphylococcus. Contains about 40 species and several species have a number of “subspecies” (Bergey’s Manual) The two we are concerned about are S. aureus and S. epidermidis Gram-positive, non-motile cocci that exist as “grape-like” clusters
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From 1980-1989, in a large number of participating hospitals, 26% of all nosocomial infections were caused by coagulase-negative S. aureus strains; 1992-1997, 40% of bacteremias
Causes the most common type of food poisoning reported
Side point: In US, 2,000,000 cases of nosocomial infections per year. Added expenditure to patients estimated at $4.5 billion. Highest rates of infection in: burn, neonatal, and pediatric ICUs.
Cells organized in irregular clusters resembling grapes
Facultative anaerobe (can ferment)
Yellow colonies on most media
“Normal” member of nasal membrane, nasopharynx, skin, perineum, GI tract and genital tract
Causes a variety of infections including:
Furuncles (boils), carbuncles, impetigo, toxic epidermal necrolysis, pneumonia, osteomyelitis, meningitis, endocarditis, mastitis, bacteremia, abscesses, food poisoning, enterocolitis, urogenital infections and toxic shock syndrome
Toxic Shock Syndrome
Superficial skin lesions
Deep seated infections
Double zone of
Some strains produce two types of hemolysis:
Inner zone caused by a toxin
Outer zone caused by the b toxin
*Sphingomyelin is a lipid found only in some animal cell membranes-
particularly in nerve cells
New York Times, July 27, 2004
Special supplies of clean coats and hand wipes, combined with tough policies on visitors and jewelry, helped a British hospital unit cut hospital-acquired infections drastically, a new study reports.
The effort, in the orthopedic unit of Broomfield Hospital in Chelmsford, was described by Dr. Leela C. Biant in a recent article in BMJ, the journal of the British Medical Association. Infections after knee and hip replacement surgery had more than tripled when patients were placed among the general hospital population in 1998, after an orthopedic unit was shut, Dr. Biant wrote. One patient died of an infection with drug resistant staphylococcus, called MRSA.
In July 2000, the hospital's orthopedic surgeons set out to seal off a 28-bed ward from infections. The first step was to limit the ward to orthopedic patients, who were tested before surgery for signs of exposure to MRSA; patients who tested positive were restricted to a second, smaller ward, where they were treated with antibiotics as a preventive measure.
Along with standard precautions against the spread of infection, nurses were given aprons that they wore at the bedside and then discarded. All staff members washed their hands before they approached a patient and afterward. Doctors wore coats from a supply that was laundered daily. Watches were not allowed on the ward; the only jewelry permitted were wedding rings and small earrings. Visitors were restricted to two at a time for two hours a day only, and were forbidden to sit on the patient's bed. In the year before the policy began, 417 joint replacement operations had produced 43 infections, including nine MRSA cases, Dr. Biant wrote. In the year after its introduction, 488 similar operations produced only 15 infections, none of which were drug resistant, she said.
Little known about the pathogenicity of S. epidermidis