Antibiotic choices critical for elderly with bloodstream infections

By Eleanor McDermid, Senior medwireNews Reporter

Failure to treat patients with bacteremia with an appropriate antibiotic is particularly harmful in elderly patients, report researchers.

"We emphasize the consideration of the patient's age as one of the critical issues in choosing empiric antimicrobial therapy," say Wen-Chien Ko (National Cheng Kung University Hospital, Tainan, Taiwan) and colleagues in the American Journal of Emergency Medicine.

Their study shows that making an incorrect choice of empirical antibiotic increased mortality risk in patients aged 65 years or older, whereas it had no noticeable impact in younger patients.

The overall 28-day mortality rate for patients presenting to an emergency department with bacteremia was significantly higher among the 288 who were at least 65 years old than among 230 younger patients, at 11.8% versus 6.1%.

Inappropriate empirical antibiotic therapy was defined as failure to treat patients with at least one drug to which the pathogen isolated from their blood samples showed in vitro susceptibility. This occurred in similar proportions of the older and younger age groups, at 29.5% and 30.9%, respectively, yet the impact on survival was markedly different.

Among elderly patients, inappropriate therapy was given to 44.1% of patients who died, compared with 27.6% of those who died, which was a significant difference. This effect persisted after accounting for confounders, with inappropriate antibiotic therapy associated with a 3.7-fold increased mortality risk.

By contrast, the rate of inappropriate antibiotic therapy did not differ between surviving and nonsurviving younger patients, and no difference emerged on multivariate analysis. The only mortality predictor in younger patients was a Pittsburgh bacteremia score of 4 points or higher, which raised mortality risk 13.7-fold.

Severe bacteremia also predicted mortality in the elderly patients, as did malignancy, bacteremia due to foci other than urinary tract infection, coronary artery disease, and elevated serum creatinine.

The types of pathogen isolated from the patients were broadly similar between the two age groups, except for a lower rate of Staphylococcus aureus in elderly versus younger patients (7.7 vs 12.9%) although they had a higher proportion of S. aureus that was resistant to methicillin (62.5 vs 29.4%).

Ko et al conclude that the approach toward empirical antibiotic therapy should differ in elderly versus younger patients with bacteremia, to ensure that elderly patients receive the best possible therapy in the emergency department.

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