Blood Cultures for the Diagnosis of Infective Endocarditis: What Is the Benefit of Prolonged Incubation?

Vincent Fihman,Pascal Lim,Amina Moussafeur,Raphaelle Huguet,Hélène Faury,Adrien Galy,Paul-Louis Woerther,Raphaël Lepeule,Sébastien Gallien

doi:10.3390/jcm10245824

Abstract

To assess the need for prolonged incubation of blood culture bottles beyond five days for the diagnosis of infectious endocarditis (IE), we conducted a retrospective cohort study of 6109 sets of two blood culture bottles involving 1211 patients admitted to the Henri Mondor University Hospital for suspicion of IE between 1 January 2016 and 31 December 2019. Among the 322 patients with IE, 194 had positive blood cultures in our centre. Only one patient with a time-to-positivity blood culture of more than 120 h (5 days) was found. The main cause for the 22 patients with positive blood cultures after five days was contamination with Cutibacterium acnes. Our results do not support extending the duration of incubation of blood culture bottles beyond five days for the diagnosis of infectious endocarditis, with the exception of patients with risk factors for C. acnes infection.

Highlights

Evidence of sustained bacteraemia is the cornerstone of the diagnosis of infective endocarditis (IE)
The last version of the European recommendations for clinical microbiology laboratories advised a duration of incubation of 7 to 15 days [4], whereas a multicentre study showed that incubation beyond five days was unnecessary for the bacterial documentation of endocarditis due to HACEK [5]
140,629 sets of two blood culture bottles for aerobic and anaerobic incubation were analysed by our clinical microbiology laboratory

Summary

Introduction

Evidence of sustained bacteraemia is the cornerstone of the diagnosis of infective endocarditis (IE). It has been suggested that the detection of fastidious Gram-negative bacilli of the HACEK group or Brucella spp. may require prolonged incubation [2]. A previous review on IE due to rare and fastidious bacteria reported that an incubation of 8 days is required to detect IE due to Aggregatibacter actinomycetemcomitans and 21 days for IE due to Brucella spp. The last version of the European recommendations for clinical microbiology laboratories advised a duration of incubation of 7 to 15 days [4], whereas a multicentre study showed that incubation beyond five days was unnecessary for the bacterial documentation of endocarditis due to HACEK [5]. We conducted a retrospective cohort study to evaluate the impact of increasing the duration of incubation of blood cultures to 15 days versus the standard five-day protocol for the bacterial documentation of IE

Methods

Results

Conclusion