Current Geriatric Diagnosis & Treatment, 1st Edition

Section III - Common Disorders in the Elderly

34. Common Infections

Robert A. Bonomo MD

Mary Anne Johnson MD

ESSENTIALS OF DIAGNOSIS

  • The most common infections in the elderly are urinary tract infections, respiratory tract infections, gastroenteritis, and skin and soft tissue infections.
  • Diagnosing infections in the elderly may be challenging because of atypical presentations and the frequent presence of cognitive impairment.
  • Delirium, falls, or functional decline may be the presenting or only sign of an infection. Fever may be absent.
  • Viral respiratory infections, especially if caused by influenza or respiratory syncytial virus, are associated with significant morbidity and mortality.
  • Screening for latent tuberculosis in high-risk elderly and treating those with positive skin tests with isoniazid significantly reduces the risk of active tuberculosis.
  • Chronic medical conditions increase the risk of bacterial pneumonia in the elderly; nursing home residents are at greatest risk.
  • Asymptomatic bacteriuria is common in the elderly and requires no treatment.
  • Gastroenteritis in the community and nursing home can be caused by viruses or bacteria; mortality from gastroenteritis and dehydration is higher in the elderly than in any other age group.
  • Antibiotics are overused in nursing homes, contributing to antibiotic resistance.
  • Treatment of infections in the elderly may be complicated by comorbid conditions, which alter pharmacokinetics of antibiotics, and by the possibility of drug interactions.

General Considerations

Despite the significant progress that has been made with the development of highly potent antibacterial agents and life-saving therapies, infectious diseases are among the major causes of morbidity and mortality in the elderly. Pneumonia, influenza, and bacteremia are the most frequent fatal infections. Many other infections, including HIV infection, can also cause significant morbidity and mortality.

Atypical presentations of infection are common in the elderly and may lead to delays in therapy. Functional decline, delirium, weight loss, or falls may be the only clues to a serious underlying infection. Fever is absent in 20-30% of elderly patients harboring a serious infection. For example, > 20% of patients older than 65 will not develop fever in the setting of pneumococcal bacteremia.

Pathogenesis

The elderly are at increased risk for infection predominantly because of comorbid conditions (eg, diabetes mellitus, chronic obstructive pulmonary disease, congestive heart failure, malnutrition), which decrease resistance. In addition, age-related changes in organ function and a decline in immune function, predominantly cell-mediated immunity, also contribute. Another risk factor is disruption of normal barriers with use of invasive devices and procedures. Institutionalization increases risk, especially for epidemic infections, because of group living.

Prevention

Although few data exist on specific nutritional interventions to prevent infections, ensuring adequate overall nutrition should decrease risk. Optimal management of chronic illnesses such as diabetes, prevention of pressure ulcers, and avoidance of indwelling catheters are recommended to reduce risk of infection. Immunization with influenza and pneumococcal vaccines reduces infection and severity of illness. Nosocomial infections can often be avoided when caregivers routinely practice hand washing. Appropriate use of antibiotics in the hospital and nursing home can decrease the risk of infections with resistant organisms, such as Clostridium difficile. Community-dwelling elderly should be educated regarding hand washing and safe food practices as well as avoidance of contact with symptomatic persons.

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Treatment

Treatment of infections, once diagnosed, is challenging in the elderly. Older persons have reduced renal clearance of antibiotics, an increased risk of medication interactions and adverse drug effects, and problems with compliance because of cognitive impairment or financial and social problems.

Norman DC: Fever in the elderly. Clin Infect Dis 2000;31:148. [PMID: 10913413]

Stalam M, Kaye D: Antibacterial therapy. Antibiotic agents in the elderly. Infect Dis Clin North Am 2000;14:357. [PMID: 10829260]

Yoshikawa TT: Epidemiology and unique aspects of aging and infectious diseases. Clin Infect Dis 2000;30:931. [PMID: 10880303]

COMMON INFECTIONS

URINARY TRACT INFECTIONS

General Considerations

Increased risk for UTI in the elderly is associated with changes of aging, including prostatic hypertrophy and loss of estrogen effect, neurogenic bladder from stroke or diabetes, incontinence, and use of indwelling and condom catheters.

Clinical Findings

Asymptomatic bacteriuria (> 100,000 colonies/mL on 2 consecutive specimens in an asymptomatic patient) is common, affecting 1-6% of men and 10-20% of women over age 60 in the community and 15-35% of men and 25-50% of women in nursing homes. The most common organisms isolated are Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, and staphylococci. Asymptomatic bacteriuria in nursing home residents, especially those with indwelling catheters, is more likely to be polymicrobial compared with that in community-dwelling elderly, and organisms are more likely to be antibiotic resistant.

Distinguishing asymptomatic from symptomatic infection may be difficult. Pyuria is almost always present in asymptomatic bacteriuria; therefore, its presence cannot be used to distinguish asymptomatic from clinical infection.

Reliance on clinical evidence of infection in making a decision to treat is compromised by the frequent absence of fever in infected elderly patients and by the inability of many patients to describe symptoms. However, in the absence of some objective evidence of infection, such as fever, flank pain, or change in cognitive or functional status, treatment for a positive culture should be withheld and the patient observed.

Treatment

Asymptomatic bacteriuria should not be treated, except just before planned genitourinary tract surgery. Treatment of asymptomatic bacteriuria in nursing home residents has not been shown to alter mortality and may contribute to increased antibiotic resistance in nursing facilities.

Symptomatic UTIs in elderly women include cystitis and pyelonephritis. The infecting organisms are similar to those in asymptomatic bacteriuria. Cystitis in elderly women has traditionally been treated with 7 days of antibiotics; a shorter duration may also be effective, but more studies are needed. Men with UTI usually have a prostatic focus and require 2-6 weeks of treatment with an antibiotic such as trimethoprim-sulfamethoxazole or a quinolone, both of which penetrate well into the prostate. An ultrasound examination of the genitourinary system might be warranted.

Single-agent empiric antimicrobial therapy is appropriate for all patients with presumed UTI. In nursing home patients, breadth of coverage should be based on the antibiotic resistance pattern in the facility. Patients with suspected sepsis from UTI require hospitalization and treatment with a beta-lactam/beta-lactamase combination, a third-generation cephalosporin, or a quinolone such as ciprofloxacin. In catheterized patients, because of the possibility of infection with gram-positive organisms (ie, methicillin-resistant Staphylococcus aureus and enterococci in up to 20% of patients), it is also appropriate to consider using a beta-lactam/beta-lactamase inhibitor combination or adding vancomycin for empiric treatment. Once culture results are available, the empiric antibiotic regimen should be changed to an appropriate antibiotic with the narrowest spectrum. Recommended empiric therapy is included in Table 34-1.

Nicolle LE: Urinary tract infections in long-term-care facilities. Infect Control Hosp Epidemiol 2001;22:167. [PMID: 11310697]

RESPIRATORY TRACT INFECTIONS

Viral Infections

General Considerations

Older adults usually experience at least 1 upper respiratory tract infection (URI) per year. Although the incidence of URI is lower in older adults than in younger patients, the morbidity and mortality associated with viral URIs are significantly greater. The management of

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viral respiratory infections is problematic because it is often difficult to determine a cause and to distinguish viral from bacterial causes. Influenza types A and B, parainfluenza, coronavirus, and rhinovirus are the cause of most common viral respiratory infections. Influenza type A and respiratory syncytial virus (RSV) cause the greatest morbidity and mortality.

Table 34-1. Empiric therapy.

Infections

Drug

Respiratory tract

 

   Influenza

Amantadine

 

Rimantidine

 

Oseltamivir

 

Zanamivir

RSV

Ribavirin in selected cases

Tuberculosis (prophylaxis)

INH

Bronchitis exacerbation

 

   FEV1 > 35% predicted

Amoxacillin/clavulanic acid

 

   or macrolide

   FEV1 < 35% predicted

Antipneumococcal fluoroquinolone (levofloxacin)

Pneumonia

 

   Community acquired, treated as outpatient

Levofloxacin

 

   or azithromycin

 

   or doxycycline

   Community acquired, hospitalized

Ceftriaxone plus azithromycin

 

   or levofloxacin alone

   Nursing home acquired, treated in nursing home

Levofloxacin ± clindamycin

 

   or moxifloxacin

 

   or levofloxacin

 

   or ceftriaxone

   Nursing home-acquired, hospitalized

Beta-lactam/beta-lactamase inhibitor plus macrolide

 

   or ceftriaxone plus clindamycin

 

   or levofloxacin plus clindamycin

 

   or moxifloxacin

Infected pressure ulcers

Amoxacillin/clavulanic acid

 

   or piperacillin/tazobactam

 

   or ertapenem

 

   or levofloxacin/metronidazole

 

   or ciprofloxacin/clindamycin

Varicella-zoster virus

Famciclovir

 

Valacyclovir

 

Acyclovir

Gastroenteritis

Trimethoprim-sulfamethoxazole

 

   or ciprofloxacin

Urinary tract

Ciprofloxacin

 

Levofloxacin

 

Amoxacillin/clavulanic acid

 

Ceftriaxone

RSV, respiratory syncytial virus; FEV1, forced expiratory volume in 1S.

Influenza types A and B cause epidemics of disease almost every winter. In the United States, these winter influenza epidemics can cause illness in 10-20% of people and are associated with an average of 36,000 deaths and 114,000 hospitalizations every year, most frequently in the elderly. RSV is second to influenza as a cause of death from viral respiratory infections.

Prevention

Prevention of influenza is the most effective way to decrease morbidity and mortality. Hospitalization and mortality in both community-dwelling elderly and nursing home residents are reduced when vaccine is administered before the influenza season. Because the influenza

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virus undergoes minor antigenic change from year to year and significant antigenic change periodically, the composition of the vaccine changes annually. All at-risk individuals must, therefore, be immunized annually. The Centers for Disease Control (CDC) recommends influenza immunization for, among others, all those 50 years of age and older, those with chronic medical conditions or immunosuppression, and all nursing home residents. The recommendation to immunize those 50 years old and older is based on the fact that many individuals in this age group have undiagnosed high-risk conditions. To further protect those who may not mount a protective antibody response either because of age or immunosuppression, it is also recommended that caregivers for persons at risk be immunized. Physicians caring for the elderly should have an influenza immunization plan in place to ensure that all those at risk receive the vaccine each fall.

Side effects of the influenza vaccine are the same for the elderly as for younger individuals: local soreness, low-grade fever, and muscle aches. The risk of Guillain-Barré syndrome with recent vaccines has been extremely small. The potential for serious complications from influenza far outweighs this small risk. When influenza occurs in a nursing home, the CDC recommends antiviral prophylaxis for all residents to prevent an epidemic. A plan for instituting such prophylaxis should be in place in all nursing homes. Prophylaxis should be continued for at least 2 weeks or, if cases continue to occur, until 1 week after the outbreak has ended. Amantadine prophylaxis has been shown to control influenza outbreaks in nursing homes. Fewer data are available on use of the newer agents in institutional outbreak control.

Clinical Findings

  1. SYMPTOMS & SIGNS

Classic influenza presents with abrupt onset of fever, chills, headache, and myalgias, which are accompanied by pharyngitis, nonproductive cough, and clear, watery nasal congestion. The fever accompanying influenza infection can last from 4-8 days. A characteristic symptom of influenza infection is retro-orbital eye pain. As patients age, they may have fewer symptoms of influenza infection and may present only with fever, cough, and confusion. The most common complications of influenza in the elderly are pneumonia (influenzal or bacterial) and exacerbation of underlying chronic lung disease.

Common symptoms of RSV infection include rhinorrhea, cough, sputum production, shortness of breath, and wheezing.

Parainfluenza virus, coronavirus, and rhinovirus cause the common cold, with symptoms of rhinorrhea, cough, and sneezing.

  1. LABORATORY TESTS

Viral culture for influenza using nasopharyngeal swab, is useful in making an etiological diagnosis because the symptoms of influenza may be similar to those of other viruses such as RSV. Rapid antigenic tests, with 80-90% sensitivity and specificity (depending on sample quality), are commercially available to detect influenza types A and B.

Unfortunately, the sensitivity of culture for RSV is extremely poor because the shedding of RSV in the oropharynx is low. In addition, RSV is thermolabile and does not survive long in transit.

Treatment

Antiviral treatment for influenza should be administered within 48h, and preferably within 12 h, of symptom onset. The earlier the antivirals are administered, the more effective they are in reducing symptoms and preventing complications. The older antivirals amantadine and rimantidine are active only against influenza type A. The neuraminidase inhibitors zanamivir (inhaled) and oseltamivir are effective against both influenza types A and B.

The treatment of RSV infection in the elderly is supportive, with hydration, oxygenation, and treatment of bronchospasm with bronchodilators. It is unclear whether aerosolized ribavirin affects symptoms in the elderly. Infection control measures are critical to stop the spread of RSV, especially in the institutional setting. RSV can survive for more than 6 h on environmental surfaces and is highly efficient in spreading among close contacts. Because compliance with hand washing in health care facilities is frequently poor, additional protective equipment such as gowns and gloves may decrease spread.

Treatment of the common cold is symptomatic with acetaminophen, decongestants, and antihistamines. However, many cold remedies contain medications that can cause adverse effects in the elderly or interact with prescription medications.

Tuberculosis

General Considerations

In the United States, ~12% of new cases of tuberculosis (TB) each year involve persons older than 65. Most TB in the elderly is a result of reactivation of latent infection and involves the lungs. However, extrapulmonary TB, including miliary disease, is more frequent in the elderly than in younger individuals. Reactivation is thought to occur because of a decline of cell-mediated immunity with age and the development of medical conditions. Malignancy, diabetes, lymphoreticular cancers,

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poor nutrition, renal insufficiency, and gastrointestinal surgeries as well as chronic institutionalization increase the risk of TB in the elderly.

Screening for Latent Disease

The tuberculin test is the best available screening test to detect previous infection. It is recommended that only those who have increased risk for TB be screened: residents and employees of nursing homes and other high-risk congregate living settings; persons with recent close contact with an active case; those who have immigrated within the past 5 years from a country with a high prevalence of TB; and those with certain medical conditions such as diabetes, renal disease, significant weight loss, some types of gastrointestinal surgery, and immunosuppression. In the elderly who have not received routine annual tests and in those admitted to nursing homes, a 2-step TB test should be done if the initial test is negative. A second test is performed a week after the first to detect the booster phenomenon. In many elderly persons who were infected at a young age, the delayed hypersensitivity has waned. The second test, if positive, will confirm that the first test has boosted this immunity. This is a positive test; it is not a conversion. Failure to perform a 2-step test initially, especially in nursing home residents, will result in an inability to discriminate the booster phenomenon from a conversion at the next annual test. A conversion requires evaluation for active disease, treatment, and an epidemiological investigation for a source case and other cases. Therefore, this distinction is critical.

Guidelines regarding criteria for positive tuberculin skin tests use ≥ 10 mm of induration as a positive test in most individuals; 5 mm of induration is considered positive in those with HIV infection, persons receiving immunosuppressive therapy, recent contacts of active cases, and patients with a chest x-ray film consistent with prior TB. Persons with positive skin tests should be evaluated for active TB with symptom review and chest x-ray film. If either of these indicate the possibility of TB, respiratory isolation, with transfer to the hospital for nursing home residents, and further evaluation are indicated. Clinicians should be aware of atypical presentations of TB in the elderly. Occasionally, pulmonary infiltrates will be located in the basal portions of the lung and be interpreted as aspiration pneumonia. Therefore, any pulmonary infiltrate in the presence of a positive skin test should be evaluated for the possibility of TB.

Treatment

If the chest x-ray film does not reveal evidence of active disease in a person with a positive skin test (ie, latent disease), it is recommended that isoniazid (INH) therapy be administered for 9 mo. Once-a-day dosing with 300 mg of INH has been shown to decrease the incidence of active TB by at least 60%. Elderly persons are at greatest risk for hepatotoxicity from INH, but the risk is low. Alcohol use may increase this risk. At least 1 study has shown no increased risk in those with chronic hepatitis, HIV infection or concurrent medication use. The use of rifampin and pyrazinamide for latent disease results in more hepatotoxicity than use of INH alone. In patients receiving treatment for latent disease, monthly clinical monitoring for symptoms is essential. In addition, patients must be instructed to stop INH and contact the clinician if unexplained nausea, anorexia, fatigue, fever, or right upper quadrant pain occurs.

Baseline liver function tests at the initiation of INH therapy are usually indicated in the elderly. Monthly laboratory monitoring of liver function tests is important in those who have cognitive impairment and who cannot report symptoms. It should also be done in those with baseline abnormalities in liver function tests, those receiving other hepatotoxic drugs, those who are positive for HIV, and those using alcohol. A rise in serum aminotransferase activity > 5 times normal or clinical evidence of hepatitis requires prompt discontinuation of INH therapy.

Some authorities suggest administering pyridoxine (vitamin B6) to reduce risk of neuropathy from INH in those at greatest risk for neuropathy (eg, those with diabetes, uremia, alcoholism, HIV, and malnutrition).

Active TB should be treated in conjunction with a specialist to ensure appropriate medication prescription and public health follow-up of the patient and contacts.

Bronchitis

General Considerations

Acute bronchitis in an elderly person without chronic lung disease is a self-limited condition that is generally viral in origin and requires no antibiotic treatment.

Clinical Findings

Symptoms of bronchitis are similar to those of pneumonia with cough, sputum production and sometimes fever. Clinical findings are insufficient to rule out pneumonia; thus a chest x-ray is essential.

Treatment

During an influenza outbreak, bronchitis in the context of an influenza-like disease should be treated with influenza antiviral therapy. Bronchitis causing an exacerbation

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of chronic lung disease is frequently treated with antibiotics. However, evidence supporting efficacy is lacking despite the findings of increased numbers of pneumococci and Haemophilus influenzae in the sputum. The decision to use antibiotics in bronchitis should be based on forced expiratory volume in 1 s (FEV1) and age. The more severely impaired patients (FEV1 < 35%) merit treatment for acute exacerbations.

Pneumonia

General Considerations

Pneumonia is the sixth most common cause of death in the United States; most of the deaths occur in the elderly. The mortality rate from pneumonia is 5 times greater in those older than 64 years than in those younger than 64.

The elderly possess many medical conditions that place them at risk for pneumonia: underlying chronic obstructive pulmonary disease or chronic bronchitis, alcoholism, dementia, neurological illness (strokes or parkinsonism), heart failure, diabetes, and renal disease.

Clinical Findings

  1. SYMPTOMS & SIGNS

Symptoms of pneumonia usually include fever and cough with sputum production, but in the elderly symptoms may be more subtle.

  1. LABORATORY TESTS

Sputum cultures are generally obtained for diagnosis. However, it is often difficult to obtain sputum cultures in the elderly and a satisfactory etiological diagnosis is not made. Blood cultures may be positive in a small percentage of patients.

Most studies in the elderly identify pneumococcus as the most prevalent pathogen. Other pathogens include H. influenzae, S. aureus, enteric gram-negative organisms, Legionella species, and Chlamydia. The most serious infections are due to S. pneumoniae and Legionella.

Treatment

Guidelines have been published for the empiric treatment of community-acquired pneumonia. Specific antibiotic recommendations for outpatient and inpatient treatment are in Table 34-1.

The severity of pneumonia often dictates site of care and has an impact on the choice of therapy. Guidelines for assessing severity of pneumonia in elderly outpatients are outlined in Table 34-2. In general, elderly outpatients have significant comorbidities, which make hospitalization necessary. In those who are hemodynamically stable, have mild symptoms, and can comply with therapy, outpatient management may be successful but close follow-up is essential.

Elderly persons in nursing homes have a 10-fold greater incidence of pneumonia than those in the community, and pneumonia is the most common reason for transfer of nursing home residents to the hospital. Nursing home residents represent 10-18% of all patients hospitalized with pneumonia. The decision to transfer a patient with pneumonia from a nursing home to the hospital may be aided by published guidelines for predicting pneumonia mortality (Table 34-3). These guidelines predict 30-day mortality using clinical criteria: respiratory rate > 30/min, pulse > 125/min, acute change in mental status, and history of dementia. When 2 or more of these findings are present, mortality is 30%. Factors that have been associated with treatment failure in the nursing home include respiratory rate > 30, pulse > 90, temperature > 38.1°C, oxygen saturation < 92%, use of a mechanically altered diet, feeding tube dependence, and altered level of consciousness.

The possibility of infection with penicillin-resistant pneumococci should be considered when choosing empiric antibiotic therapy for nursing home-acquired pneumonia. There have been several outbreaks of pneumococcal pneumonia in nursing homes, some of which have involved penicillin-resistant pneumococci. Because of the prevalence of the pneumococcus as a pathogen and because of increasing antibiotic resistance, immunization of the elderly with the 23-valent polysaccharide pneumococcal vaccine should be a priority in all settings. Recommendations for treating nursing home-acquired pneumonia are included in Table 34-1. No prospective studies have established the superiority of one antibiotic regimen over another.

Table 34-2. Severity assessment for lower respiratory tract infection in community-dwelling elderly.

Independent variables associated with mortality within 30 days
   Acute aggravation of coexisting illness
   Respiratory rate ≥ 25 breaths/min
   Elevated C reactive protein (≥ 100 mg/L)

In one study, the mortality rate was 2.2% if the patients had none or only 1 of the independent risk factors and 20% if they had all 3 risk factors.

Table 34-3. Independent variables associated with mortality within 30 days in nursing home-acquired pneumonia.

Respiratory rate > 30 breaths/min
Pulse > 125 beats/min
Altered mental status
History of dementia

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Bartlett JG et al: Practice guidelines for the management of community-acquired pneumonia in adults. Infectious Diseases Society of America. Clin Infect Dis 2000;31:347. [PMID: 10987697]

Centers for Disease Control: Prevention and control of influenza. MMWR Morb Mortal Wkly Rep 2002;51:1. [PMID: 12002171]

Centers for Disease Control: Targeted tuberculin testing and treatment of latent tuberculosis infection. American Thoracic Society. MMWR Morb Mortal Wkly Rep 2000;49:1. [PMID: 10881762]

Feldman C: Pneumonia in the elderly. Med Clin North Am 2001; 85:1441. [PMID: 11680111]

Fine MJ et al: A prediction rule to identify low-risk patients with community-acquired pneumonia. N Engl J Med 1997;336: 243. [PMID: 8995086]

Johnson JC et al: Nonspecific presentation of pneumonia in hospitalized older people: age effect or dementia? J Am Geriatr Soc 2000;48:1316. [PMID: 11037021]

Koivula I et al: Risk factors for pneumonia in the elderly. Am J Med 1994;96:313. [PMID: 10421277]

Marrie TJ: Community-acquired pneumonia in the elderly. Clin Infect Dis 2000;31:1066. [PMID: 11049791]

Medina-Walpole AM, Katz PR: Nursing home-acquired pneumonia. J Am Geriatr Soc 1999;47:1005. [PMID: 10443864]

Muder RR: Management of nursing home-acquired pneumonia: unresolved issues and priorities for future investigation. J Am Geriatr Soc 2000;48:95. [PMID: 10642029]

Naughton BJ, Mylotte JM: Treatment guideline for nursing home-acquired pneumonia based on community practice. J Am Geriatr Soc 2000;48:82. [PMID: 10642027]

Naughton BJ et al: Outcome of nursing home-acquired pneumonia: derivation and application of a practical model to predict 30 day mortality. J Am Geriatr Soc 2000;48:1292. [PMID: 11037018]

Nuorti JP et al: An outbreak of multidrug-resistant pneumococcal pneumonia and bacteremia among unvaccinated nursing home residents. N Engl J Med 1998;338:1861. [PMID: 9637804]

Seppa Y et al: Severity assessment of lower respiratory tract infection in elderly patients in primary care. Arch Intern Med 2001; 161:2709. [PMID: 11732936]

GASTROENTERITIS

General Considerations

More than 75% of all deaths from diarrhea in the United States occur in those older than 55; 50% occur in those older than 74. The greatest risk to the elderly person with diarrhea is dehydration, which may lead to cardiac, renal, and cerebrovascular complications.

A decrease in gastric acidity as a result of medications, gastric atrophy, surgery, and systemic illnesses increases the risk of infection with gastrointestinal pathogens. Elderly patients living in nursing homes or other group settings are at particularly high risk because of shared bathrooms and dining facilities, the high prevalence of incontinence, and poor staff compliance with hand-washing practices.

The principal bacterial pathogens causing diarrhea in the elderly are C. difficile, Campylobacter species, Escherichia coli, Salmonella species, and Shigellaspecies. When onset of symptoms is within 12 h of ingestion of contaminated food, the toxins of Clostridium perfringens, Bacillus cereus, or S. aureus may be responsible.

Antibiotic-associated diarrhea caused by C. difficile is common in the elderly because of more hospitalizations, nursing home stays, and antibiotic use. Up to 50% of patients older than 65 will develop C. difficile-associated diarrhea after hospitalization and antibiotic use. Much of the problem with C. difficile is due to poor infection control practices.

Clinical Findings

  1. SYMPTOMS & SIGNS

The patient experiencing diarrhea may have crampy lower abdominal pain, anorexia, fever, malaise, and watery or bloody diarrhea. In general, symptoms are not specific enough to identify the causative pathogen.

  1. difficilecan cause severe diarrhea, fever and systemic toxicity.
  2. LABORATORY TESTS

Cultures of stool and testing for C. difficile toxin in outpatients are indicated when there is a history of recent travel, recent hospitalization, inflammatory bowel disease, prior antibiotic use or unsafe food ingestion; when illness occurs in a cluster; when fever, dehydration, abdominal pain, or bloody diarrhea is present; when the patient is immunocompromised; when symptoms are severe or prolonged; and when fecal leukocytes or blood are present. Bacterial cultures for Salmonella, Shigella, E. coli, and Yersinia should always be obtained in patients hospitalized because of diarrhea and in nursing home patients with diarrhea. A stool examination for ova and parasites should be done when the patient is immunocompromised, has traveled recently, or has prolonged diarrhea. Identification of a pathogen helps tailor antibiotic therapy and assists in public health surveillance for actual or potential outbreaks.

Suspicion of C. difficile should be high in any hospital or nursing home-acquired diarrhea, especially with a

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history of antibiotic use. Diagnosis can be made by identifying the toxin in stool specimens. Flexible sigmoidoscopy or colonoscopy looking for pseudomembranes should be performed for persistent diarrhea with negative stool studies.

Treatment

In outpatients with diarrhea, viral pathogens are most common, and treatment focuses on rehydration and electrolyte replacement. Elderly patients, especially those who are frail, can become dehydrated after only 1 or 2 loose stools. Therefore, the first step in managing diarrhea is to ensure that patients have adequate oral or, if necessary, intravenous, replacement of fluids and electrolytes.

Patients with infectious inflammatory diarrhea, as evidenced by the presence of fecal leukocytes, may be started on empiric antibiotics before culture results. Antimotility drugs should not be given for inflammatory diarrhea. Where Shiga toxin-producing E. coli is suspected (nonbloody diarrhea without fever), antibiotics are not recommended because they may increase the risk of hemolytic uremic syndrome. In other causes of community-acquired or traveler's diarrhea, trimethoprim-sulfamethoxazole or a quinolone can be used. Campylobacter may be resistant to quinolones and require erythromycin.

  1. difficileshould be treated with oral metronidazole. Recurrent or severe disease may require oral vancomycin, but this should not be used as first-line therapy.

Guerrant RL et al: Practice guidelines for the management of infectious diarrhea. Clin Infect Dis 2001;32:331. [PMID: 1170940]

Slotwiner PK, Brandt LJ: Infectious diarrhea in the elderly. Gastroenterol Clin North Am 2001;30:625. [PMID: 11586549]

INFECTED PRESSURE ULCERS

Clinical Findings

  1. SYMPTOMS & SIGNS

Clinical evidence of infection includes warmth, tenderness, purulent discharge, foul odor and tissue crepitus.

  1. LABORATORY TESTS

Determining whether a pressure ulcer is infected is a challenge. Superficial swab cultures collect surface-contaminating organisms, and a positive swab culture does not necessarily mean that the ulcer is infected. The ultimate decision is clinical, based on information obtained at the bedside and histopathological evidence. If there is clinical evidence of infection, superficial cultures do not effectively reveal the infecting organism. Tissue biopsy and culture and fluid irrigation/aspiration cultures are superior alternatives. However, tissue irrigation and aspiration may yield positive results even in noninfected ulcers.

The diagnosis of infection from deep tissue biopsy requires the finding of > 106 micro-organisms per gram of tissue. Often up to 4 isolates, including anaerobes 25% of the time, will be recovered from appropriately obtained samples. The most common aerobic isolates obtained from cultures are Proteus mirabilis, enterococci, E. coli, staphylococci, and Pseudomonas. The most common anaerobic isolates are peptostreptococci, Bacteroides, and Clostridia.Bacteremia from infected pressure ulcers is more frequently from anaerobes than aerobes and is associated with a high mortality.

  1. SPECIAL TESTS

Bone biopsy should be done if osteomyelitis is clinically suspected based on an elevated white blood cell count, elevated sedimentation rate, and positive radiographic findings.

Plain films should be obtained to look for evidence of osteomyelitis, but these are often nondiagnostic. Computed tomography scans have high specificity but limited sensitivity. Their role is to assess the size of the ulcer, presence of fistulas, and possible joint involvement. Magnetic resonance imaging has a sensitivity of 98% and a specificity of 89% in detecting osteomyelitis. Radionucleotide scintigraphy and gallium scanning have been shown to be sensitive but not specific. Indium-labeled white blood cell scanning has been shown to have a specificity of seventy-seven percent compared with bone biopsy. Indium studies are particularly helpful when there is associated soft tissue inflammation. However, this procedure has not been well studied in patients with pressure ulcers.

Treatment

Antibiotic therapy for infected pressure ulcers should be used in conjunction with débridement, appropriate wound dressings, and management of pressure ulcer risk factors. Empiric antibiotics often must be administered in very ill patients. The superiority of one empiric regimen over another has not been assessed. Because these infections are polymicrobial, the use of a beta-lactam/beta-lactamase inhibitor combination should bestrongly considered. Quinolone combined with metronidazole or clindamycin is another option. Because of poor tissue perfusion of infected pressure ulcers, antimicrobial therapy should be administered intravenously in all patients who are extremely ill. Topical treatment is not effective for any infected pressure ulcer.

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Livesley NJ, Chow AW: Infected pressure ulcers in elderly individuals. Clin Infect Dis 2002;35:1390 [PMID: 12439803]

HERPES ZOSTER

General Considerations

Herpes zoster (HZ) is a neurocutaneous reactivation disease, occurring only in those previously infected with the varicella-zoster virus (VZV). Almost all persons older than 65 have been previously infected. The incidence of HZ in the elderly is 7-11 cases per 1000 persons per year. Risk factors for the reactivation of VZV include increasing age, immunosuppression, chronic diseases, and use of some medications. Illnesses most frequently associated with VZV reactivation include lymphomas, leukemias, HIV infection, and autoimmune diseases such as lupus and rheumatoid arthritis.

Prevention

VZV can be transmitted to seronegative susceptible contacts, especially during the vesicular stage. Direct contact or airborne or droplet nuclei may transmit infection. Immunization of health care workers and appropriate isolation procedures should help prevent the spread of this infection in the institutional setting. If exposure of susceptible persons occurs in an institutional setting, consultation with an infection control expert is essential to prevent an outbreak.

Clinical Findings

  1. SYMPTOMS & SIGNS

Clinicians should consider the possibility of zoster in any cutaneous syndrome involving acute unilateral dermatomal pain. Pain occurs 2-3 days before a rash develops and, in rare cases, may be the only manifestation of VZV infection. Dermatomal distribution of maculopapular followed by vesicular lesions on an erythematous base generally is sufficient to make the diagnosis, although laboratory studies may be needed in some instances to distinguish herpes simplex from varicella-zoster infection. Vesicle formation may continue for 5 days, and it usually takes 7-12 days for the vesicles to crust over.

  1. LABORATORY TESTS

Direct fluorescent antibody testing for the detection of VZV antigens in vesicular fluid is extremely specific and sensitive.

Complications

The major complication of VZV is postherpetic neuralgia, a persistent burning, throbbing, or stabbing pain that can be severely incapacitating and lead to depression, dependence, and isolation. Postherpetic neuralgia occurs in up to 50% of untreated adults older than 50 and in 75% of those older than 70. Pain may last more than 1 year, especially in those older than 70. Other rare neurological complications may occur, such as focal motor paresis in the affected area. Ophthalmic HZ, presenting with periocular, forehead, and nasal pain and lesions, is an ophthalmologic emergency because vision loss may occur. Ophthalmic HZ can also cause granulomatous angiitis of the carotid artery, which may lead to stroke. Cutanous dissemination and visceral involvement can occur in immunocompromised patients, but the risk of dissemination is decreased significantly with antiviral therapy. Bacterial superinfection with streptococci and staphylococci can also occur.

Treatment

Antiviral therapy with acyclovir, famciclovir or valacyclovir reduces acute inflammation and pain in most patients treated within 72 h of rash onset. Patients may also benefit from therapy begun after 72 h, especially if new vesicle formation continues. Because famciclovir and valacyclovir dosing schedules are simpler than that for acyclovir, these drugs may be preferable. The duration of postherpetic neuralgia is decreased by as much as 50% with antiviral therapy. Although steroids may improve acute pain, they do not decrease the incidence of postherpetic neuralgia. One study has shown that elderly persons (with no contraindications to steroids) treated with a short course of tapering prednisone in combination with acyclovir had improved quality of life, improved sleep, and more rapid return to normal activities than those treated with acyclovir alone. Steroid treatment had no effect on incidence or duration of postherpetic neuralgia. The role of steroids in combination with antiviral therapy in healthy elderly persons with HZ remains unclear but may beconsidered in those with no contraindications. In the treatment of VZV-induced facial paralysis, steroids may have a role in conjunction with antiviral therapy.

Because postherpetic neuralgia can be profoundly debilitating, early and aggressive pain management is essential. A number of medications have been used for the treatment of postherpetic neuralgia, including topical lidocaine, gabapentin, and tricyclic antidepressants. Unfortunately, none of these therapies has been prospectively studied. Opiates will be necessary in many patients to treat pain, although these medications may be associated with side effects in the elderly.

Gnann JW Jr, Whitley RJ: Herpes zoster. N Engl J Med 2002; 347:340. [PMID: 12151472]

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O'Donnell JA, Hofmann MT: Skin and soft tissues. Management of four common infections in the nursing home patient. Geriatrics 2001;56:33. [PMID: 11641861]

Schmader K: Herpes zoster in older adults. Clin Infect Dis 2001;32:1481. [PMID: 11317250]

FEVER OF UNKNOWN ORIGIN

General Considerations

Fever of unknown origin (FUO) has been defined as a temperature > 101°F persisting without diagnosis for at least 3 weeks despite at least 1 week of evaluation in the hospital. The definition has been revised to reflect the 4 different major causes, and hence different evaluation and treatment strategies: classic FUO, nosocomial FUO, immune-deficient FUO, and HIV-associated FUO. In the elderly, compared to younger persons, classic FUO is more likely to be caused by collagen vascular diseases such as temporal arteritis, by TB, or by malignancy (usually hematological). Other noninfectious causes include medications, alcoholic hepatitis, thyroiditis, hyperthyroidism, and venous thromboembolism. One third of FUOs in the elderly are caused by infection, the most common of which are infective endocarditis, tuberculosis, abscesses (usually intra-abdominal), and complicated urinary tract infections. The percentage of FUOs caused by abscesses has declined recently with the availability of more sophisticated diagnostic imaging tools.

Clinical Findings

Evaluation of an elderly patient with FUO should include a thorough history (eg, travel history; risk for immunosuppression, including HIV infection; medications; prior antibiotic use, procedures, or surgery; and TB history or exposure). Because patients with FUO have already had an extensive evaluation, further studies should be based on findings from those studies, additional information from repeated histories or examinations, and data published about the frequency of particular causes.

Treatment

Most FUOs in the elderly represent atypical presentations of common diseases, and many are treatable. Therefore, persistence in the evaluation is indicated, particularly in ruling out TB and temporal arteritis, which may require urgent treatment. In general, the recommendation is to delay therapy of the fever unless a cause is specifically identified or the patient is at imminent risk of dying. Initiating empiric antibiotics can lead to confusion in subsequent assessments.

Knockaert DC et al: Fever of unknown origin in adults: 40 years on. J Intern Med 2003;253:263. [PMID: 12603493]

Tal S et al: Fever of unknown origin in the elderly. J Intern Med 2002;252:295. [PMID: 12366602]

ANTIBIOTIC RESISTANCE

Antibiotic resistance in nursing homes is a serious concern and has resulted, in part, because of excessive use of antibiotics in this setting. In addition, patients admitted to nursing homes frequently come from hospitals and are colonized with resistant organisms from that setting. Nursing home residents may be colonized or become infected with vancomycin-resistant enterococci, methicillin-resistant S. aureus, penicillin-resistant pneumococci, multiresistant gram-negative bacilli, quinolone-resistant Pseudomonas species, and Acinetobacterspecies (Table 34-4). Blood stream infection with methicillin-resistant S. aureusposes a significant threat in the nursing home patient.

Guidelines have been published to help clinicians who work in nursing homes to diagnose and treat infections. Promoting appropriate antibiotic use through such guidelines, providing education, and monitoring

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antibiotic use and antibiotic-resistance patterns are all measures designed to reduce inappropriate use of antibiotics and thereby reduce the emergence of resistant organisms

Table 34-4. Resistant pathogens found in long-term care facilities.

Multiresistant gram-negative bacilli
   Extended spectrum beta-lactamase producing gram-
      negative bacilli (Escherichia coli and Klebsiella
      pneumoniae)
Inhibitor resistant beta-lactamase producing E. coli,
      Klebsiella
 spp, or Proteus spp.
Plasmid-mediated third-generation cephalosporin-
      resistant Klebsiella pneumoniae, and E. coli
Third-generation cephalosporin-resistant Enterobacterand
      Citrobacter spp
   Quinolone-resistant Pseudomonas aeruginosa
   TMP/SMX-resistant E. coli
Resistant gram-positive bacteria
   Methicillin-resistant Staphylococcus aureus
   Vancomycin-resistant enterococci (VRE)
   Penicillin-resistant Streptococcus pneumoniae (resistant
      also to macrolides, clindamycin, sulfamethoxazole, and
      tetracyclines)

TMP, trimethoprim-sulfamethoxazole.

Bentley DW et al: Practice guideline for evaluation of fever and infection in long-term care facilities. J Am Geriatr Soc 2001;49:210. [PMID: 11207876]

Bonomo R: Multiple antibiotic-resistant bacteria in long-term care facilities: an emerging problem in the practice of infectious diseases. Clin Infect Dis 2000;31:1414. [PMID: 11096012]

Bradley SF: Issues in the management of resistant bacteria in long-term-care facilities. Infect Control Hosp Epidemiol 1999; 20:362. [PMID: 10349960]

Loeb M et al: Colonization with multiresistant bacteria and quality of life in residents of long-term-care facilities. Infect Control Hosp Epidemiol 2001;22:67. [PMID: 10968724]

Mody L et al: Prevalence of ceftriaxone- and ceftazidime-resistant gram-negative bacteria in long-term-care facilities. Infect Control Hosp Epidemiol 2001;22:193. [PMID: 1137907]

Nicolle LE et al: Antimicrobial use in long-term-care facilities. SHEA Long-Term-Care Committee. Infect Control Hosp Epidemiol 2000;21:537. [PMID: 10968724]