STAPHYLOCOCCUS

Description

Staphylococcus epidermidis is a normal resident of the skin, the gut and upper respiratory tract. It is a true opportunistic pathogen, requiring a major breach in the host's defenses to establish infection. It is usually hospital acquired. It is associated with skin penetration by implanted prostheses, for example Spitz Holter valves (used to treat hydrocephalus), prosthetic heart valves, IV lines, intraperitoneal catheters and orthopedic prostheses. The organism's adherence to a foreign surface is facilitated by the production of a viscous slime. It is a major cause of bacteremia (blood stream infection) in neutropenics and in all patients where there is a risk of endocarditis. It is also a serious neonatal infection, particularly in very low birth weight infants. It is also of major importance in the development of foley catheter related urinary tract infections in women in hospitals.

Staphylococcus aureus is a bacterium that is a common colonizer of human skin and mucosa. Staphylococcus aureus can cause disease, particularly if there is an opportunity for the bacteria to enter the body. Skin infection illnesses such as "scalded skin" syndrome, impetigo, furuncles, carbuncles, abscesses, and wound infections are caused by S. aureus. This organism can also cause urinary tract infections, pneumonia, lung abscesses, and bacteremia with seeding to the lungs, heart and brain. It can also cause food poisoning. Most strains of this bacterium are sensitive to many antibiotics, and infections can be effectively treated. However some S. aureus bacteria are resistant to the antibiotic methicillin, and other more common antibiotics such as oxacillin, and penicillin and so are termed methicillin-resistant Staphylococcus aureus (MRSA). Staph infections, including MRSA, occur most frequently among persons who have weakened immune systems and are in hospitals and healthcare facilities (such as nursing homes and dialysis centers).

Most cases of Toxic Shock Syndrome (TSS) have been associated with certain strains of S. aureus. These strains are rarely present in vaginal cultures from healthy women but are regularly recovered from women with menstrually associated TSS or in those with TSS following gynecologic surgery. Today, 55% of cases are associated with the use of tampons. Other risk factors include the use of contraceptive diaphragms and vaginal contraceptive sponges, infection following childbirth or abortion.

Where are they found?

Humans and rarely animals.

How do we get infections?

Transmssion is through contact with a person who either has a purulent lesion or discharge or is an asymptomatic carrier, (usually nasal). Twenty to 30% of the general population are nasal carriers of S. aureus and S. epidermidis. Persons with draining lesions or any purulent discharge are the most common spread of epidemic spread. Airborne spread is rare. The role of transmission via contaminated surfaces has been documented in nursery outbreaks as well as from hospital mattresses.

Incubation period

Variable and indefinite; usually 4-10 days

Treatment

In localized skin infections systemic antibiotics are not indicated unless the infection spreads significantly. Local skin cleaning followed by the application of an appropriate topical antimicrobial agent is adequate. Avoid hot wet compresses which may spread infection; hot dry compresses may help localize infections. Abscesses should be incised to permit drainage of pus. For severe infection, a penicillinase-resistant penicillin should be prescribed. In penicillin sensitive individuals, a cephalolsporin or clindamycin may be used. Vancomycin is the drug of choice for the treatment of severe infection with coagulase negative staphylococci and methicillin resistant S. aureus. Since the late 1990s, some strains of S. aureus have shown resistance to Vancomycin. These cases were reported in the USA and Japan.

Prevention

1. Use gloves when having contact with infected area or dressings. Place all contaminated articles in a plastic or leak proof bag prior to disposal.
2. Wash hands with an antimicrobial lotion soap. If soap and water are not available, the use of an alcohol gel or foam may be used followed by hand washing as soon thereafter as possible.
3. Clean and disinfect patient's immediate surroundings as well as commonly touched surfaces.
4. Whenever a moderate of heavy abundance of staphylococci is known or suspected to be present in draining pus or the sputum of a patient with pneumonia, the patient should be considered to be placed in a private room until adequate treatment has been attained.