General Principles in Older Adults
Older adults are at greater risk for skin and soft-tissue infections (SSTIs) owing to immunosenescence, multiple comorbid conditions (specifically diabetes, peripheral vascular disease, underlying skin conditions [eg, eczema, venous stasis, and edema]), and/or frequent trauma. Defective cutaneous immunity with aging increases the susceptibility of older adults to SSTIs. Additionally, older adults have a greater likelihood of being bed-bound and hence at an increased risk for pressure ulcers.
Common types of SSTIs in older adults include cellulitis, necrotizing fasciitis, frunculosis, carbunculosis, pressure ulcers, and surgical site infections (SSIs). The incidence of each of these SSTIs varies; 1% to 9% for cellulitis and 2% to 24% for pressure ulcers in long-term care facility residents. Older adults with SSTIs have a higher mortality, morbidity, and attributable hospital costs compared to younger adults with SSTIs. For example, older adults with SSIs are 3 times more likely to die as compared to younger adults with SSIs.
The prevention of SSTIs varies by type. Cellulitis can be prevented by elevating the limb to aid adequate fluid drainage and prevent edema, using medical stockings, and treating macerated skin with topical antifungals to prevent recurrences. Similarly, furuncles and carbuncles can be prevented by practicing good hand hygiene, using antibacterial soap baths, and not sharing personal items, which will target infections by community-acquired methicillin-resistant S. aureus (CA-MRSA). Prevention strategies for pressure ulcers include frequent turning of bed-bound patients, good nutrition, and maintaining moist sacral skin. The principles of preventing of SSIs are very similar in older and younger adults including rigorous glucose control, preventing hypothermia, smoking cessation, and appropriate timing and dosing of prophylactic antibiotics.
Similar to other infections, SSTIs may manifest atypically in older adults with absence of fever and declining mental status as compared to SSTIs in younger adults. Infected pressure ulcers may go unnoticed in chronically bed-bound older adults.
Cellulitis presents with limb swelling, redness, and tenderness, whereas erysipelas involves the dermis causing a raised rash with sharp borders. Both cellulitis and erysipelas are usually caused by Streptococci species and S. aureus. Necrotizing fasciitis (type 1 and type 2) is a more severe form of SSTI that involves deeper subcutaneous tissue destroying the fascial planes. Type 1 is polymicrobial (E. coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and anaerobic bacteria), which commonly follows surgical procedures or patients with pressure ulcers, whereas type 2 is monomicrobial (usually Streptococcus pyogenes) and relatively common in older adults with diabetes. In both types of disease, the area is extremely tender and red, often with an exudate. A Gram stain of cells from the edge of the lesion can aid in diagnosis; however, a strong index of clinical suspicion is needed. Pressure ulcers are often polymicrobial and most commonly affect the sacrum, heels, elbows, and lower extremities. Diagnosis is clinical and treatment is dependent on the Gram stain results and culture of the ulcerative matter.
Scabies is a commonly missed diagnosis in older adults and hence responsible for outbreaks in skilled nursing facility residents. It is caused by a mite (Sarcoptes scabiei), which can cause normal scabies or crusted scabies, both of which can be difficult to diagnose in older adults. Normal scabies presents as raised, red, itchy lesions called burrows, typically in interdigital areas and ankles. Crusted scabies, on the other hand, presents more atypically (itching being present in only 50% of patients) in older adults owing to their lack of ability to scratch and mount an immune response. The burden of mites on the skin is much higher in crusted scabies than in normal scabies, hence there are more opportunities for outbreaks. Skin scraping and testing helps to confirm the diagnosis for crusted scabies as it is often confused with psoriasis or eczema.
Both cellulitis and erysipelas are usually caused by Streptococci species or S. aureus and hence antimicrobial therapy targeting these organisms should be used. Antimicrobial choices include first-generation cephalosporins, vancomycin, and clindamycin. In cases where CA-MRSA is suspected (eg, a purulent SSTI), therapy with vancomycin, daptomycin, clindamycin, or linezolid should be considered. The decision between oral versus intravenous therapy generally depends on the severity at presentation and comorbidities. Necrotizing fasciitis can be especially severe in older adults. Surgical intervention is the gold standard diagnostic and treatment modality. In addition to antimicrobial therapy, it is important in infection management. For severe streptococcal or clostridial necrotizing fasciitis infections, clindamycin and penicillin are the antimicrobials of choice, whereas for mixed polymicrobial infections, a broad coverage for Gram-positive and Gram-negative bacteria and anaerobes is warranted. Because all pressure ulcers, like the skin, are colonized with bacteria, antibiotic therapy is not appropriate for a positive surface-swab culture without the signs and symptoms of infection. True infection of a pressure ulcer (cellulitis, osteomyelitis, or sepsis) is a serious condition, generally requiring broad-spectrum parenteral antibiotics, sometimes leading to surgical debridement in an acute-care facility.
Therapy for rashes without confirming the diagnosis of scabies unnecessarily exposes residents to the toxic effects of the topical agents. Because scabies can be transmitted by linen and clothing, the environment should be cleaned thoroughly. This includes cleaning inanimate surfaces, hot-cycle washing of washable items (clothing, sheets, towels, etc), and carpet cleaning. Topical permethrin cream with a repeat application after a week is the recommended treatment of choice for both kinds of scabies. Oral treatment with Ivermectin may be considered in patients with erosive skin from crusted scabies. Prevention is the key to avoiding outbreaks. Major preventive strategies include cleaning of fomites, adequate hand hygiene and personal protective equipment use by staff, retreatment of patients after a week to prevent reinfestation, and avoiding overcrowding in skilled nursing facilities.