Infections in Older Adults

Infections in elderly patients can prove diagnostically challenging. Age-related factors affecting the immune system in older individuals contribute to nonspecific presentations. Other age-related factors and chronic conditions have symptoms that may or may not point to an infectious diagnosis. Delay in administration of antimicrobials can lead to poor outcomes; however, unnecessary administration of antimicrobials can lead to increased morbidity and contribute to the emergence of multidrug-resistant organisms. Careful clinical assessment and consideration of patient history and risk factors is crucial. When necessary, antimicrobials should be chosen that are appropriate for the diagnosis and deescalated as soon as possible.

Key points

  • Older patients with infection can present atypically (altered mental status, lack of fever).

  • Symptoms of chronic conditions common in the elderly can mimic infectious symptoms.

  • Diagnosis should be made considering all patient factors, including history, risk factors, presentation, and objective data.

  • Asymptomatic bacteriuria is common in the elderly and should not be treated with antibiotics.

  • Unnecessary use of antibiotics contributes to increased morbidity and emergence of drug-resistant pathogens.


The world’s population is aging. A 2015 report estimates that, by 2050, the world’s population aged 65 years and older will have increased by almost 150%. In the United States, it is estimated that, by 2035, the elderly will account for more than one-fifth of the population. As the number of elders in the United States increases, so will the number presenting to US emergency departments (EDs). In 2009 to 2010, elders accounted for 15% of all ED visits. The rate of ED visits increased with age, 511 per 1000 persons aged 65 years and older compared with 832 per 1000 persons aged 85 and older.

A substantial number of ED visits and hospitalizations in the elderly are related to infectious diseases (IDs). In 2012 alone, US elders had more than 3 million visits to the ED for IDs, representing 13.5% of all geriatric ED visits that year. This number was more than the rates of both myocardial infarction and congestive heart failure combined. Lower respiratory tract infections, urinary tract infections (UTIs), and septicemia accounted for most ID-related ED visits. ID-related hospitalization rates are consistently higher in the geriatric population and have steadily increased over the past 2 decades. , The nation’s elderly tend to have longer and more costly hospitalizations for IDs compared with younger patients. ,

Considering the anticipated steady increase in the elderly population, their consistent and increasing use of EDs and hospitals, and the significant burden of IDs on these visits, emergency physicians must be prepared to effectively evaluate and treat elderly patients presenting with possible infection. This requirement can be especially challenging because elderly patients frequently present atypically.

Aging and the atypical presentation

A loss of integrity in physical barriers (such as skin), decreased effectiveness of both the innate and adaptive immune systems, and disease-induced and iatrogenic immunosuppression all put elders at greater risk of contracting and ineffectively fighting infections. The mucociliary apparatus and cough/gag reflex help prevent unwanted material from entering the lower respiratory tract. Both are impaired in the aging population. In addition to natural barrier breakdown, iatrogenic perturbation with implanted medical devices such as cardiac pacemakers and defibrillators, heart valves, prosthetic joints, and indwelling urinary catheters can serve as a nidus of infection.

The aging immune system places elders in a chronic state of immunosuppression, called immunosenescence. Both the adaptive and innate immune systems decline in efficacy with age. The bone marrow produces fewer naive B cells ready to react to new antigens. Thymic involution by the fifth decade leaves elders with reduced numbers of available naive T cells, and a breakdown of T-cell homeostasis by the seventh decade results in a dramatically decreased repertoire of T cells. The T cells that remain tend to have defects that inhibit their ability to effectively proliferate in response to antigen activation and contribute to decreased protective antibody response following vaccination. , Older dendritic cells have been shown to activate B cells 70% less effectively than in younger people. Neutrophils, macrophages, and natural killer cells all take a similar hit in functionality.

Unsurprisingly, elders with infections tend to present differently than their younger counterparts. Nonspecific symptoms commonly seen in the elderly include confusion, generalized malaise/fatigue, failure to thrive, difficulty ambulating with frequent falls, weight loss, and urinary incontinence, none of which are specific to an infectious cause. Presence of dementia and polypharmacy can make history-taking difficult and/or unreliable. In addition, the tendency of patients to associate some symptoms with normal aging can lead to delays in presentation and underrepresentation of symptoms.

Atypical presentation has been associated with increased mortality in the elderly. In a recent study of patients aged 65 years or older, altered mental status and malaise/fatigue did not predict diagnosis of bacterial infection; however, fever greater than 38.0°C was largely predictive. The presence of fever is a helpful benchmark, but fever is absent or blunted in up to a third of elderly patients with an acute infection. In addition, elders tend to have lower baseline temperatures, suggesting that a normal febrile response in elders may not reach traditional fever cutoffs, , and development of fever can be delayed by as much as 12 hours.

Pneumonia and influenza

Incidence and Mortality

Pneumonia and influenza remain the leading causes of infectious death in the older population. One in 20 people aged 85 years or older have a new episode of community-acquired pneumonia (CAP) every year. Those aged 65 years and older account for more than 90% of influenza-related mortality in the United States every year. Age-related changes in lung function and comorbid conditions increase risk of pneumonia ( Table 1 ) and reduce the elder’s ability to successfully recover from respiratory infections, often making these events a trigger of further functional decline.

Table 1

Risk factors for pneumonia and aspiration

Risk Factors for Pneumonia Risk Factors for Aspiration
Tobacco use
Lung cancer
Chronic obstructive pulmonary disease
Impaired cough reflex
Impaired mucociliary apparatus
Impaired swallowing mechanism


Atypical presentation of pneumonia is common in elders. The classic triad of fever, dyspnea, and productive cough may be absent in more than 40% of elders with pneumonia. , Instead, they may present with delirium or other acute change in mental status, generalized fatigue, decreased functional status, urinary incontinence, and falls. , Older adults with pneumonia tend to report fewer symptoms than their younger counterparts, and a change in mental status is often the sole indication of an acute decline caused by infection. Incidence of tachypnea has been shown to increase with age and may indicate an underlying pulmonary process in an otherwise atypical presentation.


All patients presenting to the ED with suspicion of pneumonia should receive a chest radiograph. Clinical features and examination findings alone are notoriously inaccurate in diagnosing pneumonia. , If the initial chest radiograph is negative but clinical suspicion remains high, a chest computed tomography (CT) scan can be considered. The 2007 Infectious Diseases Society of America (IDSA)/American Thoracic Society (ATS) guidelines suggest empiric initiation of antibiotics and repeat chest radiograph in 24 to 48 hours. Further recommendations regarding diagnostic testing depend on the severity and treatment setting. Per 2019 IDSA/ATS guidelines, pneumococcal and Legionella antigen testing can be considered in patients with severe CAP ( Box 1 ). Blood and sputum cultures should be obtained in patients with severe CAP and in those empirically treated for methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa . Influenza testing should be done if in season. Procalcitonin measurements are not recommended by the IDSA to help determine whether or not to initiate antibiotics.

Several prognostic tools, such as the Pneumonia Severity Index and the CURB-65 ( C onfusion; U remia, blood urea nitrogen >7 mmol/L or 20 mg/dL; R espiratory rate ≥30 breaths per minutes; B lood pressure, systolic <90 mmHg or diastolic ≤60 mmHg; Age ≥ 65 years) criteria have been used for decades as decision aids to determine which patients with CAP can be safely managed as outpatients. , However, recent studies have suggested these tools may not be as accurate in older individuals, citing inappropriate emphasis on age and the lack of assessment of comorbidities such as functional status. , Emergency physicians should use these tools with caution and ultimately rely on their own best clinical judgment when deciding whether a patient needs hospitalization. The 2007 IDSA/ATS CAP severity criteria can also be used to determine level of care (see Box 1 ).

Box 1

Criteria for diagnosis of severe community-acquired pneumonia

Adapted from Mandell LA, Wunderink RG, Anzueto A, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis Off Publ Infect Dis Soc Am. 2007;44 Suppl 2:S27-72.

a Caused by infection alone (ie, not chemotherapy induced).

  • 2007 IDSA/ATS criteria for diagnosis of severe CAP

    • Defined as presence of either 1 major or 3 or more minor criteria

  • Minor criteria

    • Respiratory rate ≥30 breaths/min

    • Pa o 2 /Fi o 2 ratio ≤ 250

    • Multilobar infiltrates

    • Confusions/disorientation

    • Uremia (blood urea nitrogen level ≥20 mg/dL)

    • Leukopenia a (white blood cell count <4000 cells/μL)

    • Thrombocytopenia (platelet count <100,000/μL)

    • Hypothermia (core temperature <36°C)

    • Hypotension requiring aggressive fluid resuscitation

  • Major criteria

    • Septic shock with need for vasopressors

    • Respiratory failure requiring mechanical ventilation


Antibiotic management of CAP is summarized in Table 2 . Fluoroquinolones should be used with caution in the elderly because they can increase the risk of life-threatening side effects, including aortic dissection and aortic aneurysm rupture. , They should be reserved for situations when other treatment options are prohibited. Macrolides as monotherapy should also be used cautiously because of high resistance patterns in some areas.

Table 2

Management of community-acquired pneumonia

Data from Metlay JP, Waterer GW, Long AC, et al. Diagnosis and Treatment of Adults with Community-acquired Pneumonia. An Official Clinical Practice Guideline of the American Thoracic Society and Infectious Diseases Society of America. Am J Respir Crit Care Med. 2019;200(7):e45-e67.

Treatment Duration
Outpatient without comorbidities Monotherapy with amoxicillin, doxycycline, or a macrolide At least 5 d and should not be discontinued until the patient is afebrile for at least 48 h and clinically improving
Patients initially started on intravenous antibiotics may transition to equivalent oral therapy when they are clinically improving, hemodynamically stable, and can tolerate oral medications
Outpatient with comorbidities a (1) Amoxicillin/clavulanate, (2) cephalosporin plus macrolide or doxycycline, or (3) monotherapy with a respiratory fluoroquinolone (levofloxacin or moxifloxacin)
Inpatient (1) Combination therapy with a beta-lactam (ampicillin-sulbactam, cefotaxime, ceftriaxone) and a macrolide (azithromycin or clarithromycin) or (2) monotherapy with a respiratory fluoroquinolone

a Comorbidities such as chronic cardiac, pulmonary, hepatic, or renal disease; diabetes; alcoholism; malignancy; or asplenia.

If the patient has risk factors for MRSA or Pseudomonas (previous infection with these organisms or recent intravenous [IV] antibiotics), coverage for these organisms should be added to the regimen. Cultures should be obtained (eg, nasal MRSA polymerase chain reaction [PCR]) and, if negative, additional coverage should be discontinued. Risk factors such as residence in a nursing home, recent hospitalization, and chronic dialysis that defined the health care–associated pneumonia classification in previous guidelines have been abandoned because they do not consistently identify individuals at higher risk for antibiotic-resistant pathogens. Current guidelines do not recommend routinely adding anaerobic coverage for suspected aspiration pneumonia unless there is suspicion for lung abscess or empyema. , , Evidence suggests timely administration of empiric antibiotics (within 4–8 hours of arrival to the hospital) results in reduced mortality. , Patients with pneumonia who test positive for influenza should be given antiviral therapy regardless of timing of symptom onset.

Elders tend to have extended recovery times, and many do not return to their previous functional status. Given the extensive burden these infections can have on the geriatric population, routine pneumococcal and influenza vaccination is warranted.

Urinary tract infection

Prevalence and Risk Factors

The incidence of UTI is second only to respiratory infections in adults more than 65 years old. It is the most common infection diagnosed in nursing home residents. UTI is more common in women, but the incidence in men increases with age. Functional disability and neurogenic bladder resulting from stroke, Alzheimer’s and Parkinson’s disease, as well as bladder outlet obstruction from prostatic hypertrophy in men contribute to urinary retention and allow microorganisms to colonize and proliferate. Urinary incontinence, urogynecologic surgery, and chronic indwelling urinary catheters promote bacterial seeding of the urinary tract.

Diagnosis and Asymptomatic Bacteriuria

Diagnostic criteria for UTI and asymptomatic bacteriuria (ASB) are defined in Table 3 . ASB is common in the geriatric population. , In people living in long-term care facilities, the prevalence of ASB may be as high as 50% in women and 35% in men. Current IDSA guidelines recommend against treating ASB in the geriatric population because this has not been shown to improve outcomes.

Table 3

Definition of urinary tract infection based on symptoms and urinalysis

Adapted from Rowe TA, Juthani-Mehta M. Diagnosis and Management of Urinary Tract Infection in Older Adults. Infect Dis Clin North Am. 2014;28(1):75-89.

Term Definition
Pyuria >10 WBC/mm 3 per HPF
Bacteriuria Urinary pathogen of ≥10 5 CFU/mL
Laboratory-confirmed UTI Pyuria (>10 WBC/mm 3 /HPF) plus bacteriuria (≥10 5 CFU/mL)
Asymptomatic bacteriuria Bacteriuria in the absence of genitourinary signs or symptoms
Symptomatic UTI Bacteriuria in the presence of genitourinary symptoms (ie, dysuria, suprapubic pain or tenderness, frequency, or urgency)
Uncomplicated UTI Genitourinary symptoms (ie, dysuria, suprapubic pain or tenderness, frequency, or urgency) with evidence of pyuria plus bacteriuria in a structurally normal urinary tract
Complicated UTI UTI occurring in a patient with evidence that infection extends beyond the bladder

Abbreviations: CFU, colony-forming units; HPF, high-power field; WBC, white blood cells.

Distinguishing between ASB and true UTI is challenging in older patients. Many elders regularly experience urinary incontinence, increased frequency or urgency, dysuria, and pelvic pain even when infection is not present. More than half of women aged 80 years and older experience urinary incontinence, with a third experiencing it several times a week. These symptoms can reflect other conditions often seen in the elderly, such as bladder and pelvic floor dysfunction, atrophic vaginitis in women, and prostatic hypertrophy and chronic prostatitis in men. Patients with neurogenic bladder and UTI tend to present with back pain, increased spasticity, and urinary incontinence.

Vague presentations are clouded by shortcomings of the urinalysis (UA) or dipstick ( Table 4 ). Proper collection technique is paramount to ensure reliability. Even when the clinical presentation and UA suggest a UTI, culture data may take several days to result. In 1 study, 43% of elderly patients diagnosed with UTI in the ED ended up having a negative culture, and 95% of those were inappropriately treated with antibiotics.

Table 4

Limitations of urinalysis or dipstick

Data from Gupta K, Hooton TM, Naber KG, et al. International Clinical Practice Guidelines for the Treatment of Acute Uncomplicated Cystitis and Pyelonephritis in Women: A 2010 Update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases. Clin Infect Dis. 2011;52(5):e103-e120; and Oplinger M, Andrews CO. Nitrofurantoin contraindication in patients with a creatinine clearance below 60 mL/min: looking for the evidence. Ann Pharmacother. 2013;47(1):106-111.

Dipstick Finding Suggests Limitation
Positive leukocyte esterase Pyuria False-positive with contamination, concurrent trichomoniasis, use of medication, or consumption of food that colors the urine red
Positive nitrite Presence of nitrate-reducing bacteria (Enterobacteriaceae) Absent with non–nitrate-reducing bacteria ( Staphylococcus saprophyticus and Enterococcus )

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Jul 11, 2021 | Posted by in EMERGENCY MEDICINE | Comments Off on Infections in Older Adults

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