Staphylococcal Infections

S. aureus bacteremia Bacteremia Bacteremia is the presence of bacteria in the bloodstream. It can occur spontaneously, during certain tissue infections, with use of indwelling genitourinary or IV catheters, or after dental... read more , which frequently causes metastatic foci of infection, may occur with any localized S. aureus infection but is particularly common with infection related to intravascular catheters or other foreign bodies. It may also occur without any obvious primary site.

S. epidermidis and 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 Impetigo and Ecthyma Impetigo is a superficial skin infection with crusting or bullae caused by streptococci, staphylococci, or both. Ecthyma is an ulcerative form of impetigo. Diagnosis is clinical. Treatment is... read more ) or sometimes cellulitis Cellulitis Cellulitis is acute bacterial infection of the skin and subcutaneous tissue most often caused by streptococci or staphylococci. Symptoms and signs are pain, warmth, rapidly spreading erythema... read more , or focal with nodular abscesses (furuncles and carbuncles Furuncles and Carbuncles Furuncles (boils) are skin abscesses caused by staphylococcal infection, which involve a hair follicle and surrounding tissue. Carbuncles are clusters of furuncles connected subcutaneously,... read more ). Deeper cutaneous abscesses are common. Severe necrotizing skin infections Necrotizing Soft Tissue Infection Necrotizing soft tissue infection is typically caused by a mixture of aerobic and anaerobic organisms that cause necrosis of subcutaneous tissue, usually including the fascia. This infection... read more may occur.

Staphylococci are commonly implicated in wound and burn infections, postoperative incision infections, and mastitis Mastitis Mastitis is painful inflammation of the breast, usually accompanied by infection. Fever later in the puerperium is frequently due to mastitis. Staphylococcal species are the most common causes... read more or breast abscess in breastfeeding mothers.

Neonatal infections usually appear within 4 weeks after birth and include

Pneumonia that occurs in a community setting is not common but may develop in patients with one or more of the following characteristics:

Staphylococcal pneumonia Community-Acquired Pneumonia Community-acquired pneumonia is defined as pneumonia that is acquired outside the hospital. The most commonly identified pathogens are Streptococcus pneumoniae, Haemophilus influenzae... read more may be a primary infection or result from hematogenous spread of S. aureus infection elsewhere in the body (eg, IV catheter infection, endocarditis, soft-tissue infection) or from injection drug use. However, S. aureus is a common cause of hospital-acquired pneumonia Hospital-Acquired Pneumonia Hospital-acquired pneumonia (HAP) develops at least 48 hours after hospital admission. The most common pathogens are gram-negative bacilli and Staphylococcus aureus; antibiotic-resistant... read more , including ventilator-associated pneumonia Ventilator-Associated Pneumonia Ventilator-associated pneumonia (VAP) develops at least 48 hours after endotracheal intubation. The most common pathogens are gram-negative bacilli and Staphylococcus aureus; antibiotic-resistant... read more .

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.

Endocarditis Infective Endocarditis Infective endocarditis is infection of the endocardium, usually with bacteria (commonly, streptococci or staphylococci) or fungi. It may cause fever, heart murmurs, petechiae, anemia, embolic... read more 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. aureus has become a leading cause of bacterial endocarditis.

S. aureus endocarditis 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 Osteomyelitis Osteomyelitis is inflammation and destruction of bone caused by bacteria, mycobacteria, or fungi. Common symptoms are localized bone pain and tenderness with constitutional symptoms (in acute... read more 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 S. aureus.

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 joints Prosthetic Joint Infectious Arthritis Prosthetic joints are at risk of acute and chronic infection, which can cause sepsis, morbidity, or mortality. Patients often have a history of a recent fall. Symptoms include joint pain, swelling... read more 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 syndrome Staphylococcal toxic shock Toxic shock syndrome is caused by staphylococcal or streptococcal exotoxins. Manifestations include high fever, hypotension, diffuse erythematous rash, and multiple organ dysfunction, which... read more may result from use of vaginal tampons or other devices or complicate any type of S. aureus infection (eg, postoperative wound infection, infection of a burn, skin infection). Although most cases have been due to methicillin-susceptible S. aureus (MSSA), cases due to MRSA are becoming more frequent.

Staphylococcal scalded skin syndrome Staphylococcal Scalded Skin Syndrome Staphylococcal scalded skin syndrome is an acute epidermolysis caused by a staphylococcal toxin. Infants and children are most susceptible. Symptoms are widespread bullae with epidermal sloughing... read more , 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 Staphylococcal Food Poisoning Staphylococcal food poisoning is due to a preformed toxin made by Staphylococcus aureus bacteria that have contaminated food. Symptoms of nausea and vomiting with abdominal cramps are... read more 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 < 12 hours.

Some institutions that have a high incidence of methicillin-resistant S. aureus (MRSA) nosocomial infections routinely screen admitted patients for MRSA (active surveillance) by using rapid laboratory techniques to evaluate nasal swab specimens. Some institutions screen only high-risk patients (eg, those who are admitted to the intensive care unit, who have had previous MRSA infection, or who are about to undergo vascular, orthopedic, or cardiac surgery).

Quick identification of MRSA does the following:

In patients with pneumonia, polymerase chain reaction (PCR) testing for MRSA colonization in the nares has been shown to have a negative predictive value of > 95% for MRSA lung infection and may therefore be useful in antibiotic management.

Many staphylococcal strains produce penicillinase, an enzyme that inactivates several beta-lactam antibiotics; these strains are resistant to penicillin G, ampicillin, amoxicillin, and antipseudomonal penicillins (eg, piperacillin).

Community-acquired strains are often susceptible to penicillinase-resistant penicillins (eg, methicillin, oxacillin, nafcillin, cloxacillin, dicloxacillin), cephalosporins, carbapenems (eg, imipenem, meropenem, ertapenem), tetracyclines, macrolides, fluoroquinolones, trimethoprim/sulfamethoxazole (TMP/SMX), gentamicin, vancomycin, and teicoplanin.

MRSA isolates have become common, especially in hospitals. MRSA isolates are resistant to almost all beta-lactam antibiotics, including most cephalosporins and carbapenems; however, they may be susceptible to the newest class of MRSA-active cephalosporins (eg, ceftaroline, ceftobiprole [not available in the United States]). Hospital-acquired MRSA is also commonly resistant to many other antibiotics, including erythromycin, clindamycin, and fluoroquinolones. In addition, community-associated MRSA (CA-MRSA) has emerged over the past several years in most geographic regions. CA-MRSA tends to be less resistant to multiple antibiotics than hospital-acquired MRSA. These strains, although resistant to most beta-lactams, are often susceptible to TMP/SMX and tetracyclines (minocycline, doxycycline) and are often susceptible to clindamycin, but there is the potential for emergence of clindamycin resistance by strains inducibly resistant to erythromycin (laboratories may report these strains as D-test positive).

Vancomycin is effective against most MRSA, sometimes with rifampin and an aminoglycoside added for some serious infections (ie, osteomyelitis, prosthetic joint infections, prosthetic valve endocarditis). An alternative antibiotic (daptomycin, linezolid, tedizolid, dalbavancin, oritavancin, telavancin, tigecycline, omadacycline, lefamulin, eravacycline, delafloxacin, quinupristin/dalfopristin, TMP/SMX, ceftaroline) should be considered when treating MRSA strains with a vancomycin minimum inhibitory concentration (MIC) of ≥ 1.5 mcg/mL.

Vancomycin-resistant S. aureus (VRSA; MIC ≥ 16 mcg/mL) and vancomycin-intermediate–susceptible S. aureus (VISA; MIC 4 to 8 mcg/mL) strains have appeared in the United States. These organisms require linezolid, tedizolid, quinupristin/dalfopristin, daptomycin, TMP/SMX, delafloxacin, oritavancin, or ceftaroline. Dalbavancin and telavancin are active against VISA but have little activity against VRSA. Oritavancin is active against both VISA and VRSA.

Because incidence of MRSA has increased, initial empiric treatment for serious staphylococcal infections (particularly those that occur in a health care setting) should include an antibiotic with reliable activity against MRSA. Thus, appropriate antibiotics include the following:

Table summarizes treatment options.

The S. aureus organism recurs in up to 50% of carriers and frequently becomes resistant. For certain MRSA carriers (eg, preorthopedic, vascular, and cardiovascular surgical patients), some experts recommend nasal decolonization with mupirocin ointment 2 times a day for 5 to 10 days and topical body decolonization regimens with a skin antiseptic solution (eg, chlorhexidine) or dilute bleach baths (about 5 mL/L) for 5 to 14 days.

Topical nasal mupirocin has been proved somewhat effective for reducing MRSA infection in hospitalized patients (eg, patients in intensive care units, those undergoing major surgeries). Although mupirocin resistance is emerging, a large study showed a 30% reduction in postdischarge MRSA infection risk over 1 year for patients who were colonized with MRSA and treated with decolonization for 5 days 2 times a month for 6 months. Each 5-day decolonization regimen included 2% nasal mupirocin once a day, a 4% chlorhexidine bath or shower once a day, and 0.12% chlorhexidine mouthwash 2 times a day (1 Prevention references Staphylococci are gram-positive aerobic organisms. Staphylococcus aureus is the most pathogenic; it typically causes skin infections and sometimes pneumonia, endocarditis, and osteomyelitis... read more ).