Reducing blood culture contamination by a simple information intervention. Department of Medical Microbiology, Skåne University Hospital, Sweden - PDF

JCM Accepts, published online ahead of print on September 0 J. Clin. Microbiol. doi:./jcm.00- Copyright 0, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

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JCM Accepts, published online ahead of print on September 0 J. Clin. Microbiol. doi:./jcm.00- Copyright 0, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved. Reducing blood culture contamination by a simple information intervention Roth A MD PhD 1, Wiklund AE 1, Pålsson AS, Melander EZ MD PhD, Wullt M MD PhD, Cronqvist J MD, Walder M MD PhD 1, Sturegård E MD PhD 1 Department of Medical Microbiology, Skåne University Hospital, Sweden Department of Infectious Diseases, Skåne University Hospital, Sweden Department of Infection Control, Skåne University Hospital, Sweden Corresponding author: Adam Roth Department of Medical Microbiology, Skåne University Hospital, SUS Malmö tel:+1 (The address may be published). Running head: Reducing blood culture contamination 1 ABSTRACT Compared to true-negatives, false-positive blood cultures not only increase laboratory work but prolong length of stay and use of broad-spectrum antibiotics, both likely to increase antibiotic resistance and patient morbidity. The increased patient suffering and surplus costs caused by blood culture contamination motivates substantial measures to decrease the rate of contamination, including the use of dedicated phlebotomy teams. The present study evaluated the effect of a simple information intervention aimed at reducing blood culture contamination at Skåne University Hospital (SUS) Malmö, Sweden, during. months focusing on departments collecting many blood cultures. The main outcome of the study was contamination rates pre- and post-intervention, analyzed in a multivariate logistic regression model, adjusting for relevant determinants of contamination. 1 blood culture sets were drawn from 1 patients during the study-period (January 00 December 00). The blood culture contamination rate pre-intervention was.% and decreased to.% postintervention (odds ratio 0.; % confidence interval 0.-0.). A similar decrease in relevant bacterial isolates was not found post-intervention. Contamination rates at three auxiliary hospitals did not decrease during the same time period. The effect of the intervention on phlebotomists knowledge of blood culture-routines was also evaluated with a clear increase in level of knowledge among interviewed phlebotomists post-intervention. The present study shows that a relatively simple information intervention can have significant effects on the level of contaminated blood cultures, even in a setting with low rates of contamination where nurses and auxiliary nurses conduct phlebotomies. INTRODUCTION Blood cultures are commonly contaminated, often representing as much as 0% of positive cultures. (1) Compared to true-negatives, false-positive (contaminated) blood cultures not only increase laboratory work but also prolong length of stay of patients and increase the use of broad-spectrum antibiotics, with negative consequences for antibiotic resistance and patient morbidity. Furthermore, false-positive results can cause confusion regarding antibiotic regime, endangering patient safety. (,,1) The dominating organism in blood culture contamination, Coagulase-negative staphylococci (CoNS), is also an increasingly important pathogen which is a significant clinical problem, since there is no true gold standard for determining contamination from relevant pathogens.(1,,1,) Although not applicable for clinical use in individual patients, a laboratory assessment definition of contamination for comparison of rates between institutions has been developed. Target rates should not exceed %, () but many teaching hospitals have contamination rates exceeding % or more. (,1,) Considering the potential savings in resource utilization it is justified to invest considerable resources in reducing blood culture contamination. () Since contamination most probably is a result of personnel introducing exogenous bacteria into the blood culture, education of phlebotomists is central to prevention. Many studies advocate the effectiveness of teams of specialized phlebotomists in reducing contamination rates. (,1,) Feedback, intense education in correct phlebotomy routines and long-term monitoring programs has also been shown to be effective. (,,,) In general, interventions seem less effective and contamination rates higher among nursing personnel conducting phlebotomy compared to specialized phlebotomy teams.(,,1,1,) In addition to presenting internationally comparable rates of blood culture contamination from a Swedish university hospital, the present study evaluates the effect of a simple information intervention aimed at reducing blood culture contamination in a setting where phlebotomy for blood culture is conducted by nurses and auxiliary nurses and not by dedicated phlebotomy teams. The major outcome of the study was intervention-effect on blood culture contamination rates. We also monitored the effect in a novel way, by assessing the impact of the intervention on phlebotomists knowledge of disinfection and phlebotomy routines. METHODS 1 Setting Skåne University Hospital (SUS) is a tertiary care teaching hospital in Sweden with two separate facilities, SUS Lund (formerly Lund University Hospital, USIL) and SUS Malmö (formerly Malmö University Hospital, UMAS). SUS Malmö consists of around 0 beds and 000 staff. The intervention was carried out at SUS Malmö during. months from February to May 00 focusing on phlebotomists (nurses and auxiliary nurses) at departments collecting many blood cultures. Effects of the intervention on phlebotomists knowledge of disinfection- and phlebotomy-routines as well as on contamination rates, was evaluated comparing periods before the intervention with periods during and after intervention (postintervention) At SUS Malmö phlebotomy for blood culture is carried out by nurses and auxiliary nurses and not by dedicated phlebotomy teams. The standard order for blood culture was two blood culture sets from different phlebotomies with no specified delay between the sets. Each blood culture set consisted of one aerobic BacT/ALERT FA (BioMérieux) and one anaerobic BacT/ALERT FN (BioMérieux) bottle containing -ml of blood. For children, and in some cases adults, the BacT/ALERT PF bottle containing 0.-mL blood was used. In the present study a blood culture set was defined as all bottles containing blood drawn from the same phlebotomy (typically bottles). Under certain conditions, physicians may decide to draw blood from intravascular lines, the recommendation in these cases was to draw a blood culture set by standard phlebotomy as well. The blood culture bottles were kept in room temperature and transferred as soon as possible ( % within hours) to the microbiology laboratory for analysis, where the patient identity and analysis order was manually entered into the computerized microbiology laboratory system. Blood cultures were incubated in the BacT/ALERT D instrument (BioMérieux) for. days or until microbial growth was detected. Detection of microbial growth was automatically registered in the computerized microbiology laboratory system. The incubation period could be extended to days on special indications (endocarditis, fungal infection, animal bites) Definition of contamination A blood culture set was defined as the bottles obtained from one blood sample (1- bottles) and considered contaminated if one of the following organisms were present in 0% of all blood culture sets obtained from one patient on the same day: Coagulase-negative staphylococci, alpha-hemolytic streptococci, Micrococcus species, Propionibacterium species, Corynebacterium species and Bacillus species. Since this definition of contamination could not be applied when only one bottle or one blood culture set was drawn for culture, pediatric blood culture bottles and single set samples were excluded from the present study. The recommendation for blood culture in children is to only draw blood (0,- ml) into a single pediatric bottle. If more than one organism was present in the culture, they were scored individually when calculating contamination rates, such that if 0% of blood culture sets in one patient had both a contaminant and a relevant organism, the set was still counted as contaminated. However, if two different contaminants were present in 0% blood culture sets, it was only counted as one contaminated set. The number of blood culture sets per patient was accumulated during the whole follow-up period, regardless of number of admissions. The intervention The problem of rising contamination rates at some departments was discussed with medical doctors and nurses at the departments of Hospital Hygiene, Infectious Diseases and Clinical Microbiology. Common experience was that phlebotomists did not always adhere to the guidelines on skin disinfection and phlebotomy, factors well known to affect contamination rates. Several reasons were suggested, such as a stressful working environment, impractical phlebotomy guidelines and lack of information and feedback. We decided to re-evaluate our guidelines and to perform an information intervention aimed at phlebotomists. After literature search on evidence for phlebotomy practices, our guidelines were re-written to better suit the current clinical situation. The recommendation to carefully disinfect the skin at the phlebotomy site for two minutes was changed to instead recommend one minute active disinfection before allowing to dry. This change was motivated by a general opinion that the previous recommendation was too time-consuming to be adhered to in a stressful working environment. A 1 minute long structured presentation on blood cultures, for usage at weekly staff-meetings by different discoursers, was composed. The presentation included 1 powerpoint-slides and aimed to deliver main messages: 1) What is a contamination/relevant pathogen? ) Describe how we recommend disinfecting and drawing blood for blood culture, but also why these are our recommendations ) Phlebotomist skill can make a difference for contamination rates ) Feedback on phlebotomy practice to phlebotomists is important for contamination rates. ) The department s contamination rates compared to the whole hospital ) Contamination of blood cultures may be very costly, not only for the laboratory but also for other clinics ) A promise to report back to the departments. The presentation was commented upon by doctors and nurses at the three involved departments. Directors of departments at SUS Malmö were informed of the study. During February to May 00, teams consisting of a nurse and a doctor subsequently conducted presentations at departments. The departments comprised the emergency ward, intensive care unit, infectious disease ward, orthopaedic ward, general medicine ward, general surgery ward and paediatric ward. The larger units were visited several times and we estimate that over half of all personnel conducting phlebotomies at the included departments attended the presentations, Sterilization procedure The sterilization procedure recommended when drawing blood for blood culture included: a) Hand disinfection (ethanol 0-%) b) Swab the top of the BacT/ALERT bottles (0,% chlorhexidine in 0% isopropyl alcohol) after removing the protective plastic from the bottles and allow to dry c) Swab the injection site (0,% chlorhexidine in 0% isopropyl alcohol) during two (pre-intervention)/one (post-intervention) minutes and allow to dry d) Do not palpate the vein again after skin disinfection e) Use protective gloves. 1 1 Knowledge among phlebotomists about blood culture contamination In order to evaluate the effect of the intervention we assessed the level of knowledge of correct blood culture practice among phlebotomists. A semi-structured interview with a questionnaire (Appendix), comprising four main questions, was developed: 1) Are phlebotomy routines for blood culture different from other blood samples, for instance for chemical analysis? ) How are the routines different? ) Why are the routines different? ) Describe the disinfection routines before drawing blood for blood culture. The interviews were performed orally with in total phlebotomists prior (n=1) and - weeks after (n=1) intervention at comparable departments. The answers to the questions were recorded simultaneously in the questionnaire by the interviewer. The phlebotomists had to have been present at the intervention lecture in order to be included in the group being interviewed after the intervention. In addition, adherence to blood culture routines recommending sets/blood culture order was investigated by comparing rates of single set cultures pre- and post- intervention. Contamination rates Contamination rates from (including January 00) prior to the intervention that started in February 00 were used as baseline value. Within the years (00-00) prior to the intervention we assessed determinants of contamination in a multivariate logistic regression model. The variables investigated were; year of blood culture (00, 00, 00), age at blood culture ( =0, 1-0, 1-0, 0 years), sex (male, female), number of blood culture sets taken (, -, -, sets/patient). The year of blood culture was included in this analysis to assess whether there were any trends or variance over time at SUS Malmö in contamination rates. If another variable was related to contamination rates at % level of significance it was included in the final model for analysis of intervention effect. Year of contamination could not be included in the final analysis due to co-linearity with the intervention period. Three auxiliary hospitals to SUS Malmö were also analyzed for contamination rates in blood cultures in a similar way in order assess whether the hospitals were of interest for comparison, albeit with a small number of blood cultures Contamination rates prior to intervention (January 00 to January 00) were compared to rates during and after the intervention (February 00 to December 00). The contamination rates from May 00 to December 00 were tested for trends to assess if there was a trend of increasing contamination rates in the time following the intervention period using nonparametric test for trends. Since there is no gold standard for when a CoNS is a contaminant or a pathogen, we also presented data for CoNS even when not classified as contamination by our definition: CoNS present in more than 0% of the blood culture sets obtained from one patient on the same day (typically / sets). Furthermore, data on three major blood stream infection organisms proven to almost always be pathogenic were presented; Escherichia coli, Staphylococcus aureus and Streptococcus pneumonia (). The analyses were set up in a multivariate logistic regression model, adjusting for relevant determinants of contamination. All analyses were done using Stata/SE (.0 edition) software. Ethics All phlebotomists agreed voluntarily to participate in the interviews. RESULTS Contamination rates During the complete study period, January 00 to December 00, 1 blood culture sets were drawn from 1 patients at SUS Malmö. The rate of contamination was.0% of all blood culture sets, representing % of positive blood culture sets. The dominating contaminant was CoNS (Table 1) Determinants of contamination During the three years prior the intervention, 00-00, there was no change in contamination rates over time. Furthermore, there was no association between sex and contamination rate, whilst age above 0 years and having many cultures taken were associated with high rates of contamination (Table ). Pooling blood culture sets from three auxiliary hospitals (n=1) displayed larger variance in contamination rates between the years, with contamination rates ranging from.% 00 to.1% Assessment of the effect of the intervention on phlebotomy and disinfection practice Phlebotomists interviewed after the intervention consequently scored better on the questions concerning both knowledge on blood culture routines and disinfection practice. Phlebotomists interviewed both pre- and post-intervention were better at describing why than how procedures were different between phlebotomy for blood culture versus a regular sample. However, post-intervention interviewees scored higher both on stating which routines were different and also in explaining why they were different. (Figure 1) In addition, a significant reduction of single set blood cultures was seen post-intervention, Odds Ratio (OR) 0. (% Confidence Interval (CI) ), demonstrating better adherence to the guidelines recommending sets/blood culture order Effect of the intervention on contamination rates Of the 0 blood cultures taken before the intervention (pre-intervention: January 00 to January 00).% were classified as contaminated. Post-intervention (including intervention period: February 00 to December 00) the contamination rate was.%, which was a significant decrease also when adjusting for relevant determinants of contamination OR 0. (% CI 0.-0.) (Table ). There was no significant trend of increasing rates of contamination (p=0.) during the months following the intervention (June 00 to December 00). The rate of CoNS not classified as contaminants were not reduced by the intervention, OR 0. (% CI ). There was an increase of S. pneumoniae during the intervention period (Table ). Pooling the three relevant pathogens E. coli, S. aureus and S. pneumoniae, there was no significant increase during the intervention period OR 1. (% CI 0.-1.) whereas there was a significant decrease of contaminants (Table ). Pooling the contamination rates for the three auxiliary hospitals there was no difference in contamination rates comparing pre-intervention to post-intervention period, OR 0. (% CI ) adjusting for relevant determinants of contamination. 0 1 DISCUSSION 1 1 The rate of positive blood cultures at SUS Malmö were similar to studies from other hospitals while contamination rates of blood cultures before our intervention were comparatively low by international standards. Contamination rates did not increase during the four years included in the study. Having many blood cultures taken and increasing age of patients were both independent risk factors for blood culture contamination. The information intervention had apparent effects on nurses and auxiliary nurses knowledge and understanding of disinfection and phlebotomy routines. Despite a low rate of contamination, the intervention also had a significant effect on contamination rates at the intervention hospital but there was no observable effect during the corresponding time periods at three auxiliary hospitals. The intervention did not decrease the rates of E. coli, S. aureus, S. pneumoniae or CoNS not defined as contaminants Compared to other studies using a similar definition of contamination, the present study was considerably larger with lower pre-intervention baseline rates of contamination than those presented in most recent studies. (-,,1) However, our contamination rates preintervention were comparable to the mean rates of large multi-center studies from the US, (,1) while previous studies from Sweden or similar settings to ours have not been presented. For optimal detection of pathogens it is recommended by the Swedish reference group for clinical microbiology to collect 0ml of blood per blood culture set. (0) Compared to some of the previous studies, we therefore routinely collect larger volumes of blood (usually -0ml) which may partly explain the low contamination rates since these are inversely related to blood volume. () Some authors have suggested that blood culture contamination rates are increasing, possibly due to better identification instruments and more 1 extensive use of indwelling intravenous catheters for drawing blood culture (). There was however no increase in blood culture contamination during the four years of follow-up in the present study, which is in line with the findings from a major previous m
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