Streptococcus Pneumoniae Bacteremia Secondary to Community-Acquired Pneumonia: Another Case of Shorter Is Better?

The optimal duration of antibiotic therapy for Streptococcus pneumoniae bacteremia remains a topic of debate in clinical practice. The mortality rate of bacteremia associated with a pneumococcal infection ranges from 6% to 20%.¹ Balancing effective treatment with the need to minimize antibiotic exposure is critical, as prolonged courses can contribute to increased risk of Clostridioides difficile infection (CDI) and resistance patterns. Current guidelines from the American Thoracic Society and the Infectious Diseases Society of America for the treatment of community-acquired pneumonia (CAP) recommend a short course (5-7 days) of treatment, but they do not comment on the duration of therapy for bloodstream infections (BSIs) secondary to a pneumonia.² Shorter durations of therapy for other types of infections have been a topic of recent research, but there are limited data available for S pneumoniae BSI.

The retrospective, single-center cohort study investigated whether a short course (5-10 days) vs a long course (11-16 days) led to significant differences in clinical outcomes in patients with a bacteremia secondary to CAP. The primary outcome was clinical failure defined as a composite of all-cause hospital readmission, bacteremia recurrence with S pneumoniae, and all-cause mortality within 30 days of first positive blood culture result. Secondary outcomes included hospital length of stay, intensive care unit (ICU) length of stay, rate of CDI, and rate of central venous catheter placement. Key inclusion criteria included patients who were 18 years or older, had S pneumoniae isolated in at least 1 bottle of blood cultures, received antibiotic therapy within 48 hours of the first positive blood culture result, and achieved clinical stability by day 10 of first positive blood culture result. Patients met exclusion criteria if treatment duration was less than 5 days or more than 16 days, if death occurred before 10 days of therapy, if they had a polymicrobial BSI, or if there was evidence of an invasive infection. Conducted from April 1, 2017, to May 31, 2023, in a 6-hospital health system, the study included 162 patients meeting inclusion criteria, with pertinent demographics shown in the TABLE. The average age of the patient population was 59 years, with a range of 23.5% to 30.6% of patients requiring ICU admission or transfer and the majority having pneumonia (86.5-98%). The most common antibiotic choice was combination β-lactam and macrolide as empiric therapy.

The primary composite outcome was not statistically significant between the short duration and long-duration groups (27.5% and 18.9%, respectively; P = .225). Though numerically higher in the short-duration group (27.5%) vs the long-duration group (18.2%), the rates of all-cause hospital readmission were not statistically significant (P = .214). All 4 secondary outcomes were no different between the 2 cohorts. To mitigate prescriber bias of antibiotic selection, the study investigators used inverse probability of treatment weighting and found no statistical difference when stratified by selected variables (ie, patient age > 70 years, immunocompromised patients, Pitt bacteremia score).

At discharge, oral β-lactam monotherapy was most frequently chosen for continued therapy, followed by an oral fluoroquinolone, for an average of 2 days in the short-duration group and 7 days in the long-duration group. Like most retrospective observational study designs, there are several limitations, including reliance on accurate documentation in the electronic health record, prescriber bias when choosing antibiotic therapies, and assessment of patient adherence to outpatient therapy. However, the results of this study contribute crucial stewardship findings to support shorter courses of antimicrobial therapy in an area lacking robust clinical data. The study findings also add to growing evidence to support oral step-down therapy in uncomplicated bacteremias. In findings from a study by Ramos-Otero et al, the average length of antibiotic therapy was 11.8 days, with an oral β-lactam as the most common oral option chosen upon discharge, which was a similar finding in the highlighted study.³

Although this article adds data to our antimicrobial stewardship tool kit to support shorter courses being equally as efficacious as longer courses, it is important to keep the study population in mind. The majority of these patients were not in an ICU setting and had uncomplicated S pneumoniae bacteremia secondary to a pulmonary source of infection, therefore making it challenging to apply data from this population to other patient populations. Further prospective randomized trials are necessary to confirm the observed findings for clinicians to change practice habits.

HIGHLIGHTED STUDY Crotty M, Devall H, Cook N, et al. Short versus long antibiotic duration in Streptococcus pneumoniae bacteremia. Open Forum Infect Dis. 2024;11(9):ofae478. doi:10.1093/ofid/ofae478

References
1.Kalin M, Ortqvist A, Almela M, et al. Prospective study of prognostic factors in community-acquired bacteremic pneumococcal disease in 5 countries. J Infect Dis. 2000;182(3):840-847. doi:10.1086/315760
2.Metlay J, Waterer GW, Long AC, et al. ATS/IDSA guidelines for diagnosis and treatment of adults with community-acquired pneumonia. Am J Respir Crit Care Med. 2019;200(7):e45-e67.
3.Ramos-Otero GP, Sarangarm P, Walraven C. A retrospective analysis of intravenous vs oral antibiotic step-down therapy for the treatment of uncomplicated streptococcal bloodstream infections. J Clin Pharmacol. 2022;62(11):1372-1378. doi:10.1002/jcph.2097