Delayed response predicts need for extended antibiotics for inpatients with low-risk, gram-negative bacteremias


Antibiotic therapy for 7 days or less may be just as effective as longer courses of antibiotics for select inpatients with uncomplicated gram-negative bacteremia from urinary infections, based on a retrospective, single-center analysis by researchers at Maimonides Medical Center in New York.

Hospitalized patients whose temperatures returned to levels below 100.4º F within 72 hours of starting therapy appeared to do well on short-course (7 days or less) antibiotic therapy, Siddharth Swamy, Pharm.D., and his colleagues reported in a study in Infectious Diseases in Clinical Practice posted online Dec. 30, 2015. However, increased clinical failures were noted in patients with a delayed response to therapy, indicating that duration of therapy needs to be individualized for each patient.

The researchers reviewed 178 eligible cases of gram-negative bacteremia. The most common source of bacteremia was the urinary tract (53%), followed by catheters (14%), and unknown sources (14%).

Patients were treated with antibiotics for either 7 days or less (42 patients), 8-14 days (100 patients), or more than 14 days (36 patients). The patients in the study were comparable, with the exception of a higher percentage of patients in the short-course antibiotic group who no longer had temperatures above 100.4º F within 72 hours of initiating therapy. The respective percentage of patients who had defervesced in 72 hours or less was 79% for 7 days or less of therapy, 69% for 8-14 days of therapy, and 36% for more than 14 days of therapy (P = .0002). Overall clinical response rates were 79% for 7 days or less of antibiotics, 89% for 8-14 days of therapy, and 81% for more than 14 days of therapy. Microbiologic cure rates were 83%, 89, and 92%, respectively; the differences were nonsignificant.

However, persisting fever predicted clinical response: Among patients who defervesced after 72 hours, the short-course treatment group had a significantly decreased clinical response rate, compared with intermediate- and long-course treatment groups (11%, 65%, 70%, respectively; P = .03).

The most common infectious pathogens were Escherichia coli (46%) and Klebsiella pneumoniae (22%); most cases were low-inocula bacteremias and were related to urinary tract infections in 53% of the cases. Thus, the findings “are not necessarily applicable to high-inocula bacteremias, nonlactose-fermenting gram-negative organisms, or multidrug-resistant gram-negative organisms,” the researchers wrote.

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