A Multicenter Evaluation of Blood Culture Practices, Contamination Rates, and the Distribution of Causative Bacteria

Abstract

Background:The prognostic value of blood culture testing in the diagnosis of bacteremia is limited by contamination.Objectives:In this multicenter study, the aim was to evaluate the contamination rates of blood cultures as well as the parameters that affect the culture results.Materials and Methods:Sample collection practices and culture data obtained from 16 university/research hospitals were retrospectively evaluated. A total of 214,340 blood samples from 43,254 patients admitted to the centers in 2013 were included in this study. The blood culture results were evaluated based on the three phases of laboratory testing: the pre-analytic, the analytic, and the post-analytic phase.Results:Blood samples were obtained from the patients through either the peripheral venous route (64%) or an intravascular catheter (36%). Povidone-iodine (60%) or alcohol (40%) was applied to disinfect the skin. Of the 16 centers, 62.5% have no dedicated phlebotomy team, 68.7% employed a blood culture system, 86.7% conducted additional studies with pediatric bottles, and 43.7% with anaerobic bottles. One center maintained a blood culture quality control study. The average growth rate in the bottles of blood cultures during the defined period (1259 - 26,400/year) was 32.3%. Of the growing microorganisms, 67% were causative agents, while 33% were contaminants. The contamination rates of the centers ranged from 1% to 17%. The average growth time for the causative bacteria was 21.4 hours, while it was 36.3 hours for the contaminant bacteria. The most commonly isolated pathogens were Escherichia coli (22.45%) and coagulase-negative staphylococci (CoNS) (20.11%). Further, the most frequently identified contaminant bacteria were CoNS (44.04%).Conclusions:The high contamination rates were remarkable in this study. We suggest that the hospitals’ staff should be better trained in blood sample collection and processing. Sterile glove usage, alcohol usage for disinfection, the presence of a phlebotomy team, and quality control studies may all contribute to decreasing the contamination rates. Health policy makers should therefore provide the necessary financial support to obtain the required materials and equipment.

Pre‐hospital antibiotic therapy preceded by blood cultures in a physician‐manned mobile emergency care unit

“…When working pre‐hospitally in less than optimal conditions, it is often easiest to draw BCs from the peripheral venous catheter as this is being inserted. This, however, has proven to be associated with higher contamination rates 27 …”

Best Practices of Blood Cultures in Low- and Middle-Income Countries

“…Another measure to decrease contamination is to disinfect the blood culture bottle septum with 70% isopropyl alcohol or ethanol before injecting the blood sample (88, 193, 229, 230); in many institutes, however, this is not done routinely (193, 231). Bekeris et al did not find evidence for the effectiveness of this measure in decreasing contamination, however they noted that their study was not powered to detect such an effect as they had quite low rates of contamination overall (206).…”

Estimation of missed bloodstream infections without the third blood culture set: a retrospective observational single-centre study

“…Furthermore, we must emphasize the possible loss of 10/298 cases of candidemia and six cases of MRSA bacteraemia because of the high morbidity and mortality of these infections [21e24]. Prior studies have reported contamination rates of less than 3% of positive blood cultures, in which CoNS was the most frequent microorganism (44.0%) [25,26].…”