Red Book 28e

Staphylococcal Infections

Clinical Manifestations

Staphylococcus aureus causes a variety of localized and invasive suppurative infections and 3 toxin-mediated syndromes: toxic shock syndrome, scalded skin syndrome, and food poisoning (see Staphylococcal Food Poisoning). Localized infections include hordeola, furuncles, carbuncles, impetigo (bullous and nonbullous), paronychia, ecthyma, cellulitis, omphalitis, parotitis, lymphadenitis, and wound infections. S aureus also causes infections associated with foreign bodies, including intravascular catheters or grafts, pacemakers, peritoneal catheters, cerebrospinal fluid shunts, and prosthetic joints, which can be associated with bacteremia. Bacteremia can be complicated by septicemia; endocarditis; pericarditis; pneumonia; pleural empyema; soft tissue, muscle, or visceral abscesses; arthritis; osteomyelitis; septic thrombophlebitis of large vessels; and other foci of infection. Primary S aureus pneumonia also can occur after aspiration of organisms from the upper respiratory tract and typically is associated with mechanical ventilation or viral infections in the community (eg, influenza). Meningitis is rare unless accompanied by an intradermal foreign body (eg, ventriculoperitoneal shunt) or a congenital or acquired defect in the dura. S aureus infections can be fulminant and commonly are associated with metastatic foci and abscess formation, often requiring prolonged antimicrobial therapy, drainage, and foreign body removal to achieve cure. Risk factors for severe S aureus infections include chronic diseases, such as diabetes mellitus and cirrhosis, immunodeficiency, nutritional disorders, surgery, and transplantation.

Staphylococcal toxic shock syndrome (TSS) , a toxin-mediated disease, usually is caused by strains producing TSS toxin-1 or possibly other related staphylococcal enterotoxins. This toxin acts as a superantigen that stimulates production of tumor necrosis factor and other mediators that cause capillary leak, leading to hypotension and multiorgan failure. Staphylococcal TSS is characterized by acute onset of fever, generalized erythroderma, rapid-onset hypotension, and signs of multisystem organ involvement, including profuse watery diarrhea, vomiting, conjunctival injection, and severe myalgia (see Table 3.65). Although approximately 50% of reported cases of staphylococcal TSS occur in menstruating females using tampons, nonmenstrual TSS cases occur after childbirth or abortion, after surgical procedures, and in association with cutaneous lesions. TSS also can occur in males and females without a readily identifiable focus of infection. Prevailing clones of community-associated methicillin-resistant S aureus (MRSA) rarely produce TSS toxin. People with TSS, especially menses-associated illness, are at risk of a recurrent episode.

Table 3-65

Staphylococcal scalded skin syndrome (SSSS) is a toxin-mediated disease caused by circulation of exfoliative toxins A and B. The manifestations of SSSS are age related and include Ritter disease (generalized exfoliation) in the neonate, a tender scarlatiniform eruption and localized bullous impetigo in older children, and a combination of these with thick white/brown flaky desquamation of the entire skin, especially on the face and neck, in older infants and toddlers. The hallmark of SSSS is the toxin-mediated cleavage of the stratum granulosum layer of the epidermis (ie, Nikolsky sign). Healing occurs without scarring. Bacteremia is rare, but dehydration and superinfection can occur with extensive exfoliation.

Coagulase-Negative Staphylococci

Most coagulase-negative staphylococci (CoNS) isolates from patient specimens typically represent contamination of culture material (see Diagnostic Tests). Of the isolates that do not represent contamination, most come from infections that are associated with health care, in patients who have obvious disruptions of host defenses caused by surgery, medical device insertion, immunosuppression, or developmental maturity (eg, infants with very low birth weight). CoNS are the most common cause of late-onset bacteremia and septicemia among preterm infants, especially infants weighing less than 1500 g at birth, and of episodes of health care-associated bacteremia in all age groups. CoNS are responsible for bacteremia in children with intravascular catheters, cerebrospinal fluid shunts, peritoneal catheters, vascular grafts or intracardiac patches, prosthetic cardiac valves, pacemaker wires, or prosthetic joints. Mediastinitis after open-heart surgery, endophthalmitis after intraocular trauma, and omphalitis and scalp abscesses in neonates have been described. CoNS also can enter the bloodstream from the respiratory tract of mechanically ventilated preterm infants or from the gastrointestinal tract of infants with necrotizing enterocolitis. Some species of CoNS are associated with urinary tract infection, including Staphylococcus saprophyticus in adolescent females and young adult women, often after sexual intercourse, and Staphylococcus epidermidis and Staphylococcus haemolyticus in hospitalized patients with urinary tract catheters. In general, CoNS infections have an indolent clinical course in children with intact immune function and even in children who are immunocompromised.

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