Surveillance Cultures In Pediatric Hematopoietic Stem Cell Transplantation: The Possibility Of Early Directed Antimicrobial Therapy For Bloodstream Infections With Throat Swabs
Authors: Kim Hyery , Lee Ji Won , Kang Hyoung Jin , Park Kyung Duk , Shin Hee Young , Ahn Hyo Seop 
Published: October 2019

Introduction
Bloodstream infection (BSI) is one of the most serious complications in patients undergoing hematopoietic stem cell transplantation (HSCT). Early detection and optimal antimicrobial therapy according to antimicrobial susceptibilities is important. This study is to assess the utility of surveillance cultures in predicting invasive pathogens when bacteremia occurs in HSCT patients.

Patients & Methods
Microbial and susceptibility results of surveillance cultures from patients who underwent HSCT from December, 1999 to May, 2013 in our institution were retrospectively reviewed. A total of 612 transplantations in 527 patients were evaluated (309 allogeneic, 303 autologous). Surveillance cultures were obtained weekly from the day of admission (d-9 or d-10) to the day of neutrophil over 1,000/uL. Five cultures were taken as one set by aseptic cotton swabs at the different body sites; axilla, external auditory canal, throat (posterior pharyngeal wall), nasal cavity and anus. As supportive preventions for infection, patients gargled with sodium bicarbonate solution and took showers every day with decontaminated water during admission.

Results
Total 10,180 cultures were done in all patients, and average 16.6 cultures were done in one HSCT. The first set of cultures was done in all 612 HSCTs (immediate after admission), the second in 579 HSCTs, and the third in 450 HSCTs, respectively. Positive culture rates were highest in the first set of cultures; axilla 80%, ear 33.3%, throat 98.3%, nasal 53.5%, and anus 45%. Although positive culture rates of four other sites were decreasing in sequential cultures, those of throat cultures were the highest among five body sites and sustained through 1st to 5th sets (median 62%, range 40∼98.5%). The most common microbes were Staphylococcus epidermidis, Streptococcus species, viridans group and Staphylococcus hominis. Almost all cases of Staphylococcus were methicillin resistant (95%). There was no significant difference in culture positive rates and microbial results between allogeneic and autologous groups or between different stem cell sources or different intensities of conditioning.
Forty-four patients were diagnosed with BSI. Among those, ten patients showed the same organisms with identical susceptibilities in blood and surveillance cultures (Table). Two patients died from BSI, and in both cases, the organisms were resistant to the usual broad-spectrum antibiotics. The positive culture site of surveillance in these patients included throat, and 7 out of 10 patients showed earlier proven results of the same organisms in throat cultures.

Conclusion
In surveillance cultures other than blood, throat was the highest culture positive site. Although most of the organisms from surveillance cultures were normal flora, to the patients who showed fever with suspicious BSI, prior throat cultures could offer important information to choose early directed antibiotics. If BSI was suspected and there were resistant organisms in prior throat surveillances, rapid addition of susceptible antibiotics to those organisms could be considered.

Disclosures:
No relevant conflicts of interest to declare.