Infectious Disease and Immunization
What to know
Older adults have immunosenescence and atypical infection presentations: absence of fever, blunted leukocytosis, and delirium as the first sign. Common infections: pneumonia, urinary tract infection, skin/soft tissue, and sepsis. Asymptomatic bacteriuria should not be treated except in pregnancy or before urologic procedures-overtreatment drives resistance and C. difficile. Vaccination is core preventive care: influenza annually, pneumococcal (per current schedule), zoster (recombinant), COVID-19, and Td/Tdap. Antibiotic stewardship matters because of renal dosing and drug interactions. C. difficile is a major nosocomial risk, especially after antibiotics.
Traps
Don't treat asymptomatic bacteriuria. Don't assume absence of fever excludes infection-delirium may be the only sign. Adjust antibiotic doses for renal function. Watch for drug interactions (e.g., warfarin with antibiotics). Distinguish colonization from infection using clinical signs.
Rule of thumb
"Delirium is a fever equivalent in the frail elder": any acute confusion warrants infection workup.
Worked example
An 85-year-old with acute confusion, no fever, and a urinalysis showing pyuria but no urinary symptoms: do not treat asymptomatic bacteriuria; search for another delirium cause (medications, dehydration, pneumonia).
Worked example 2
A patient on warfarin started on an antibiotic: monitor INR closely; interaction can raise bleeding risk.