infectious diseases
Staphylococcal Infections
Diseases Caused by Staphylococci
Staphylococci cause disease by Direct tissue invasion Sometimes exotoxin production Direct tissue invasionis the most common mechanism for staphylococcal disease, including the following: Staphylococcal skin infections None Staphylococcal pneumonia None Staphylococcal endocarditis None Staphylococcal osteomyelitis None Acute Infectious Arthritis None Multipleexotoxinsare sometimes produced by staphylococci. Some have local effects; others trigger cytokine release from certain T cells, causing serious systemic effects (eg, skin lesions, shock, organ failure, death). Panton-Valentine leukocidin (PVL) is a toxin produced by strains infected with a certain bacteriophage. PVL is typically present in strains of community-associated methicillin-resistantS. aureus(CA-MRSA) and has been thought to mediate the ability to necrotize; however, this effect has not been verified. Toxin-mediated staphylococcal diseases include the following: Staphylococcal toxic shock syndrome None Staphylococcal scalded skin syndrome None Staphylococcal food poisoning None The infections and disorders listed below are further discussed elsewhere in THE MANUAL. Bacteremia , which frequently causes metastatic foci of infection, may occur with any localized S. epidermidisand other coagulase-negative staphylococci increasingly cause hospital-acquired bacteremia associated with intravascular catheters and other foreign bodies because they can form biofilms on these materials. Staphylococcal bacteremia is an important cause of morbidity (especially prolongation of hospitalization) and mortality in debilitated patients. Skin infections are the most common form of staphylococcal disease. Superficial infections may be diffuse, with vesicular pustules and crusting ( Impetigo and Ecthyma ) or sometimes In impetigo, clusters of vesicopustular or bullous lesions form, rupture, and develop a honey-colored crust. Image courtesy of Thomas Habif, MD. This photo shows clusters of vesicles and pustules with developing honey-colored crust on the nose. DR P. MARAZZI/SCIENCE PHOTO LIBRARY Furuncles (boils) are tender nodules or pustules that involve a hair follicle and are caused by staphylococcal infection. Image provided by Thomas Habif, MD. Staphylococci are commonly implicated in wound and burn infections, postoperative incision infections, and Mastitis or breast abscess in breastfeeding mothers. Neonatal infections usually appear within 4 weeks after birth and include Skin lesions with or without exfoliation Neonatal Sepsis None Neonatal Bacterial Meningitis None Neonatal Pneumonia None Pneumonia that occurs in a community setting is not common but may develop in patients with one or more of the following characteristics: Influenza Chronic bronchopulmonary or other high-risk diseases Corticosteroid or immunosuppressant therapy Indwelling IV catheters for home parenteral therapy or hemodialysis Injection drug use Community-Acquired Pneumonia may be a primary infection or result from hematogenous spread of Staphylococcal pneumonia is occasionally characterized by formation of lung abscesses followed by rapid development of pneumatoceles and empyema. CA-MRSA often causes severe necrotizing pneumonia. Infective Endocarditis can develop, particularly in people who use injection drugs and patients with prosthetic heart valves. Because intravascular catheter use and implantation of cardiac devices have increased, S. aureusendocarditis is an acute febrile illness often accompanied by visceral abscesses, embolic phenomena, pericarditis, subungual petechiae, subconjunctival hemorrhage, purpuric lesions, heart murmurs, perivalvular abscess, conduction defects, and heart failure secondary to cardiac valve damage. Osteomyelitis occurs more commonly in children, causing chills, fever, and pain over the involved bone. Subsequently, the overlying soft tissue becomes red and swollen. Articular infection may occur; it frequently results in effusion, suggesting septic arthritis rather than osteomyelitis. Most infections of the vertebrae and intervertebral disks in adults involve Joints typically become infected via hematogenous infection, but infection can also be caused by extension of a bone infection, trauma, or direct infection during joint surgery. Prosthetic Joint Infectious Arthritis are particularly prone to infection. Staphylococcal infection of a prosthetic joint in the months after implantation is usually acquired during surgery, whereas infections occurring more than 12 months after surgery are likely due to hematogenous spread. However, infections still may be secondary to organisms that were inadvertently introduced at the time of implantation and remained dormant and then became clinically evident several months later. Staphylococcal toxic shock may result from use of vaginal tampons or other devices or complicate any type of Staphylococcal Scalded Skin Syndrome , which is caused by several toxins termed exfoliatins, is an exfoliative dermatitis of childhood characterized by large bullae and peeling of the upper layer of skin. Eventually, exfoliation occurs. Scalded skin syndrome most commonly occurs in infants and children < 5 years. Staphylococcal Food Poisoning is caused by ingesting a preformed heat-stable staphylococcal enterotoxin. Food can be contaminated by staphylococcal carriers or people with active skin infections. In food that is incompletely cooked or left at room temperature, staphylococci reproduce and elaborate enterotoxin. Many foods can serve as growth media, and, despite contamination, they have a normal taste and odor. Severe nausea and vomiting begin 2 to 8 hours after ingestion, typically followed by abdominal cramps and diarrhea. The attack is brief, often lasting 