|Year : 2019 | Volume
| Issue : 3 | Page : 65-71
Impact of novel blood culture collection bundle to reduce blood culture contamination rates: An important continuous quality improvement indicator of laboratory medicine
Kinjal P Patel1, Trupti N Carval2, Aruna Poojary3, Reshma Poojary1
1 Department of Microbiology and Serology, Apoorva Diagnostics and Healthcare, Bhaktivedanta Hospital and Research Institute, Thane, Maharashtra, India
2 Infection Control Nurse, Bhaktivedanta Hospital and Research Institute, Thane, Maharashtra, India
3 Department of Pathology and Microbiology, Breach Candy Hospital Trust, Mumbai, Maharashtra, India
|Date of Submission||16-Oct-2019|
|Date of Acceptance||03-Apr-2020|
|Date of Web Publication||18-Aug-2020|
Dr. Kinjal P Patel
Apoorva Diagnostics and Healthcare, Bhaktivedanta Hospital and Research Institute, Mira Road, Thane, Maharashtra
Source of Support: None, Conflict of Interest: None
Introduction: Blood cultures play a very important role in the diagnostic algorithm for managing patients with sepsis. Contamination of blood cultures complicate patient care resulting in unnecessary antibiotic use, prolonged hospital stays and more financial burden on the patient. Hence, microbiology laboratories strive to keep contamination rates within <3% as per international standards.
Aim: To monitor blood culture contamination rate and reduce contamination using a novel blood culture collection (BCC) bundle.
Materials and Methods: A prospective interventional study carried out in a newly set up Microbiology laboratory of a 200 bed tertiary care hospital in North Mumbai. Blood cultures from various clinical areas of the hospital were processed using the BacT/Alert system (BioMereiux, Marcy l'etiole, France). All positive blood cultures were co-related clinically and assigned as pathogens or contaminants. Blood culture contamination rates were actively monitored and BCC bundle was introduced to reduce contamination, which comprised six steps to follow while performing BCC. Active surveillance, audits of the collection process and root cause analysis (RCA) of blood culture contamination were done simultaneously. This was followed by feedback to phlebotomists, nurses and doctors. Periodic and need-based onsite training of health-care workers was also done.
Results: Different types of Health Care Workers were performing the procedure. The most common contaminant grown were Gram-positive cocci 159 (25.5%), followed by Gram-negative bacilli 58 (9.32%), and Bacillus spp. 37 (5.95%). It was observed that skin disinfection and incorrect order of draw were two main reasons for the contamination. Over a period of 18 months, BCC bundle implementation reduced the contamination from 17% to 4%.
Conclusion: RCA, training, surveillance and audits are essential to improve the quality of blood culture results. Implementation of the BCC bundle benefits both the microbiology laboratory and the clinical teams by decreasing the growth of contaminants and improving the utility of blood culture for better management of patients in sepsis bringing in favorable outcomes.
Keywords: Blood cultures, contamination, blood culture collection bundle, targeted interventions
|How to cite this article:|
Patel KP, Carval TN, Poojary A, Poojary R. Impact of novel blood culture collection bundle to reduce blood culture contamination rates: An important continuous quality improvement indicator of laboratory medicine. J Patient Saf Infect Control 2019;7:65-71
|How to cite this URL:|
Patel KP, Carval TN, Poojary A, Poojary R. Impact of novel blood culture collection bundle to reduce blood culture contamination rates: An important continuous quality improvement indicator of laboratory medicine. J Patient Saf Infect Control [serial online] 2019 [cited 2022 Dec 6];7:65-71. Available from: https://www.jpsiconline.com/text.asp?2019/7/3/65/292436
| Introduction|| |
Despite many advances in health-care management, bloodstream infection is one of the major causes of mortality and morbidity. In the intensive care unit (ICU) settings, sepsis is one of the most common causes of mortality. Bloodstream infections can be acquired either in community or in health-care facilities and the sources of bacteraemia can either be primary or due to distant sites of infection like respiratory, gastrointestinal or integumentary systems. Accurate and rapid diagnosis of such pathogens, causing sepsis helps in initiating appropriate antibiotics, thereby improving clinical outcomes. Automated blood culture systems like BACTEC (BD Diagnostics, Sparks, USA) and BacT/Alert system (Biomerieux, Marcyl'etiole, France) increases the sensitivity of detecting microorganisms by >95% versus conventional methods. Automated systems have many advantages such as increased sensitivity, reduced contamination, faster detection time and streamlined laboratory workflow. Furthermore, they have the provision of keeping bottles for extended incubation when fastidious organisms are suspected. These features have made them the standard of care in the diagnostic algorithm of managing patients with sepsis.
Despite being the most effective tool for diagnosing sepsis, contamination of blood cultures has been a notable health-care issue for decades. False-positive blood cultures cause misinterpretation subsequently leading to overuse of antibiotics, unwanted side effects of the drugs, increased risk of healthcare-associated infections with drug-resistant pathogens, extended length of hospital stay and financial burden.
As per definition, blood culture contamination refers to the isolation of normal skin flora from single blood culture bottle, which is of no clinical significance. This normal skin flora comprises of microorganisms such as coagulase-negative Staphylococci (CONS), Bacillus spp., Corynebacterium spp. and Propionibacteria spp. Another important cause of false-positive blood cultures is 'pseudobacteremia'. Pseudobacteremia defines as false positives blood cultures arises due to contamination, which occurs when organisms that are not actually present in a blood sample are grown in culture. These organisms include Burkholderia cepacia, Pseudomonas fluorescens, etc. Reporting such organisms in patients with no clinical history has a major impact on patient management. So, it is crucial to monitor the blood culture contamination rate as a continuous quality improvement indicator and to keep it within the international standard rate of ≤3%.
Studies have reported that 46%–68.2% errors in the total testing process occur in pre-analytical phase and only 7%–13% errors occur in the analytical phase. High error rates in the pre-analytical phase are often outside and beyond the direct control of the laboratory because it includes different types of health-care workers (HCWs) like doctors and nurses who perform primary sample collection., Many studies have shown that effective skin antisepsis reduces the rate of contamination., Even implementation of standardized phlebotomy practices by dedicated phlebotomy team along with use of blood culture collection (BCC) kits reduces contamination. Unfortunately, a dedicated phlebotomy team is not practical in developing countries like India. Another important step that needs to be emphasised is the 'order of draw for blood collection'. Guidelines recommend that the order of draw of blood during phlebotomy should be blood culture/sterile tubes first, followed by coagulation tubes, plain tubes/gel tubes and finally, tubes containing additives., This approach reduces contamination of blood culture bottles by preventing the mixing of blood with additives from previous tubes that could cause false-positive results. It is important to note that every step in the total testing process is performed by following correct and standardised procedure. It ensures the accuracy of results produced and the best patient care as well. Thus, the present study was aimed to calculate the rate of contamination to identify the possible reasons and the impact of targeted interventions taken to reduce blood culture contamination.
| Materials and Methods|| |
The present study is a prospective interventional study conducted at a 200-bed tertiary care hospital from December 2017 to May 2019. The study was reviewed and approved by the Institution Review Board. All blood culture samples were collected in the hospital either as outpatient or inpatient service sent to the microbiology laboratory for further processing. One set of aerobic blood culture bottle were collected and sent for processing. Received blood culture bottles were incubated in an automated system BacT/Alert (Biomerieux, Marcyl'etiole, France) for 5 days. Once the bottle flagged positive in the system, it was immediately removed from the machine and gram staining was performed. Simultaneously, inoculation of 5% sheep blood agar and MacConkey agar was done, and plates were incubated for 24 h at 37°C. Gram stain results were noted and informed to the respective consultant telephonically. A detailed patient's history was noted, and the relevance of the gram stain discussed. The organisms were considered contaminants if one bottle grew skin flora or Gram-negative bacilli with no clinically significant history. Organisms like CONS, B. cepacia, Diphtheroids, Bacillus species were considered as contaminants. Vitek2 compact system (BioMerieux, Salt Lake City, USA) was used for identification and antimicrobial susceptibility testing of all blood culture positive bottles. The final report was issued if there was no growth after 5 days of incubation. Environmental surveillance was conducted to identify the source of contamination, which included cultures of the disinfectant solutions, cotton swabs used for skin antisepsis, and culture of the vacutainers. All culture positives from the environmental sampling were identified, and drug susceptibility testing (DST) performed using the Vitek 2 Compact system to establish similarity between blood culture contaminants and environmental isolates.
Blood culture contamination rate was actively monitored from December 2017. All data were collated and analysed. The rate of blood culture contamination was calculated by dividing the total number of contaminated blood cultures by the total number of blood cultures received. Comparison was made with international standards for blood culture contamination.
For BCC, the original protocol for skin antisepsis at our facility was povidone iodine and alcohol. After 3 months of monitoring the contamination rate, a BCC bundle was introduced in March 2018 to reduce blood culture contamination. The main components of the bundle were as follows:
- Hand Hygiene: HCWs collecting the sample were asked to perform hand hygiene with alcohol rub before starting the procedure. Instructions were given to follow eight steps of hand hygiene with alcohol-based formulation as per the World Health Organisation guidelines 
- Personal protective equipment (PPE): All HCWs performing sample collection to wear appropriate PPE like gloves and masks
- Skin antisepsis: 2% chlorhexidine with 70% isopropyl alcohol to be used for skin antisepsis
- Cleaning the puncture site with sterile gauze piece in a circular motion starting from the intended needle insertion site to the outer direction allowing the antiseptic agent to dry before skin puncture
- Removing the cap from each blood culture bottle, cleaning the top of the culture bottles with 70% isopropyl alcohol and allow drying
- Order of draw: Follow the order of draw of blood during phlebotomy. If a request for blood culture is made along with other test requests, always collect and inoculate the blood culture bottles first. This will be followed by coagulation tubes, plain tubes/gel tubes and finally, tubes containing additives [Table 1].
HCWs comprising nurses, phlebotomists and resident doctors were trained on the bundle components. After the introduction of the BCC bundle, periodic and need-based onsite training of were given. To assess the BCC bundle compliance, active surveillance and audits of the collection process were done.
| Results|| |
During the study period from December 2017 to May 2019, a total of 4193 blood cultures samples received in the microbiology laboratory. Out of 622 (14.83%) blood culture bottles flagged positive, 273 (6.51%) blood cultures were false-positive, while 349 (8.32%) blood cultures had true bacteraemia [Figure 1]. It was noted that blood culture contamination was significantly higher during the month of December 2017 to February 2018. Location wise distribution showed that the highest rate of blood culture contamination was in ICU 151 (55%) followed by indoor wards 71 (26%) and outdoor patients 55 (20%) [Figure 2].
|Figure 1: Percentage of true bacteremia and contamination amongst positive flagged blood culture bottles|
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|Figure 2: Location wise distribution of contaminants observed during the period of December 2017 – May 2019|
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During periodic surveillance, we observed that when the order of draw was not followed, Gram-negative bacilli (Burkholderia cepcia) were grown as contaminants. The identification and DST of organisms isolated from vacutainer and blood culture were identical which were further proved by microbial culture of vacutainers, which grew B. cepacia. When skin antisepsis was not performed correctly, Gram-positive cocci and bacilli were isolated as contaminants. Accordingly, the most common contaminants were Gram-positive cocci (25.5%) followed by Gram-negative bacilli (9.32%) and Gram-positive bacilli (5.95%) [Figure 3]. After the introduction of BCC bundle in March 2018, the contamination rate significantly reduced from 17% to 4.10% over the period of 18 months [Figure 4].
|Figure 3: Percentage of different contaminants grown in blood cultures during the study period|
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|Figure 4: Trend of blood culture contamination rate during the study period of December 2017 – May 2019|
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| Discussion|| |
Blood cultures are an important diagnostic tool for health-care professionals managing sepsis. A true positive blood culture gives a definitive diagnosis that enables to start of targeted therapy. However, false-positive results greatly limit the utility of this important test, resulting in the waste of resources in the laboratory and the risk of erroneous reporting to the clinical team. Furthermore, the use of central venous catheters and other indwelling vascular access devices worsens the situation by increasing the risk for bacteraemia. And blood culture interpretation in this group of patients is quite challenging since results can also be due to line colonisation.
The importance of accurate blood culture interpretation plays a role in understanding hospital epidemiology too. The tracking and reporting of nosocomial infections and monitoring of bloodstream infection rates are both essential. Several studies have been done that explain multiple approaches to differentiate contaminants and true pathogens, but this determination continues to be a challenge, especially in new health-care set facilities like the one understudy. Co-relation with the clinical findings is the key to this differentiation.
The present study showed a blood culture contamination rate of 6.51% while the international benchmark of blood culture contamination has been determined to be 2%–3%. Many strategies and recommendations are available to reduce blood culture contamination. Amongst them, the main strategies include the use of effective antiseptic agents, educational interventions and the use of the appropriate technique by a dedicated phlebotomist. Studies have documented significant reductions after implementing standardized practices for BCC by a dedicated phlebotomy team and the use of collection kits. A dedicated phlebotomy team can be challenging in a developing country like ours. Therefore, to reduce blood culture contamination, we implemented a multifaceted approach that included education and training, on-site observations, senior supervision, BCC bundle implementation, feedbacks from staff and active surveillance.
It was observed that contamination rates were higher in the month of December 2017 to February 2018. This was the time when the microbiology laboratory was set up, and preliminary training was given to staff regarding best practices. This was further strengthened with education, training, on-site feedbacks and BCC bundle introduction in March 2018. Subsequently, a significant reduction to 3% was documented. All HCWs (resident doctors, nurses and technicians) were trained to follow the BCC bundle as each step plays a very significant role in reducing contamination. Amongst them, hand hygiene, which is a surrogate marker of infection control practices is very crucial. Emphasis was given on PPE. One randomized study involving interns in ICU/medical wards found that routine use of sterile gloves resulted in a lower contamination rate. It is crucial to resist the urge to palpate the vein after cleaning the site as this increases contamination.
In the present study, inappropriate skin antisepsis was the most common cause of blood culture contamination. The most common cause of false-positive results occurs due to contamination from the patient's own skin at the time of the collection of samples. Dawson et al. noted that alcohol-based products show statistically significant improvement in reducing false positive from skin contamination. Maiwald and Chan  suggested disinfection with 70% ethanol followed by chlorhexidine gluconate. There are studies where povidone-iodine was replaced by chlorhexidine gluconate and a significant reduction in contamination rates was observed., Studies also showed that chloraprep antiseptic alone did not reduce contamination. Roth et al. observed that education intervention, when combined with chlorhexidine use, reduces contamination significantly. Besides all published literature available, CDC guidelines also suggest use of chlorhexidine 0.5% w/v that demonstrated to be superior to povidone-iodine in preventing contamination. The original protocol for skin antisepsis at our facility was povidone-iodine and spirit. It was observed during our initial audit that compliance for skin antisepsis was poor because it was time consuming as povidone iodine solution required at least a 3 min contact time followed by alcohol repeated at least twice. Hence we replaced both solutions with a single solution containing 2%w/v chlorhexidine alcohol and all HCWs were educated and trained on skin antisepsis.
Along with the selection of antiseptics, the method of performing skin antisepsis is equally important. Conventionally, two skin cleaning techniques are known that is concentric circles and back and forth friction. Swabbing the site in concentric circles starting from the needle insertion site towards the periphery is the best practice to maintain good asepsis. Tepus et al. had addressed in his study about the correlation of proper skin preparation with different solutions, technique of application and length of time the solution is allowed to dry on the surface. The study showed a significant decrease in contamination rates when 2% chlorhexidine and 70% isopropanol was used versus the tincture of iodine. For scrubbing the site, 2% chlorhexidine applied by back and forth motion for complete 30sec followed by drying for 15–20 s, vigorous scrubbing was done to get into cracks and crevices of the skin. While tincture of iodine applied in outward circular motion and allowed to dry for 2 min. Limited research is available regarding the method of skin cleaning, as various solutions are used for these procedures and techniques used to apply differs with solution drying time as an additional variable. In the present study, the emphasis was given on swabbing the skin in concentric circles with sterile gauze piece.
Cleaning the tops and neck of culture bottles before collection also reduces the chances of contamination. Swab the rubber stopper with antiseptic before inoculating the sample. Unpublished literature suggests that povidone iodine should not be used to clean the tops as it may degrade the rubber septum and will compromise the sterile integrity of bottles. It has been well reported that most errors occur in the pre-analytical phase, an area that is usually outside of direct control of the laboratory. Proper blood collection can drastically reduce the instance of contamination and its related consequences. Guidelines recommend the 'order of draw' of blood during phlebotomy should be practised, which is an important step in the total testing process of blood cultures. Knowing the fact that ideal phlebotomy conditions and protocols are not always followed or possible, European Federation for Clinical Chemistry and Laboratory Medicine Working Group for the Preanalytical phase recommend to follow the correct order of draw for venous blood collection. In the present study, it was observed that the order of draw was not followed. Audits revealed that coagulation tubes were collected before blood culture bottles, a process that has earlier also shown to cause pseudobacteraemia by Mcneil et al. due to unsterile coagulation tubes. When blank vacutainers from critical areas were processed for bacterial culture, they grew B. cepacia phenotypically identical to the blood culture contaminants. Literature showed many pseudo outbreaks and outbreaks due to Burkholderia spp. that were acquired nosocomially. It was observed that major contaminant isolated was B. cepacia that gradually reduced after implementation of the BCC bundle [Figure 5]. Hence, the following order of draw was very crucial.
|Figure 5: Impact of blood culture collection bundle on rates of contaminants during the study period|
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In present study, it was observed that Gram-positive cocci, which include Micrococcus spp. and CONS were the most common bacteria isolated as a contaminant followed by Gram-negative bacilli which was B. cepacia. Many studies reported the CONS as the most common contaminant., Differentiation between contamination and true bacteraemia is very critical for proper management of patients and for appropriate utilisation of hospital resources. Isolation of the same organism from multiple blood culture sets is the proven methodology that helps to differentiate contamination from true infection. And it is always recommended to correlate with the clinical history of the patient for better judgement. For example, CONS can cause bloodstream infections in immunocompromised patients and neonates, so differentiation between contamination and true bacteraemia can be done by noting down proper clinical history of the patient.
Despite numerous advances in blood culture methodology and systems in recent decades, the possibility of blood culture contamination still exists. Such unexpected observations in newer automated blood culture processing system may be due to improved algorithms for detecting microbial growth even if present in low numbers, which were easily missed by conventional methods previously. Even several broth medium formulations available today have improved detection capacity for Staphylococcus spp., including CONS, which is the most common amongst contaminants. Somehow, this ability of new systems and media to detect organisms with small numbers may be responsible in some part for the observed increase in the proportion of blood cultures with contaminants.
To maintain a low rate of contamination, analysis of blood culture contaminants, active surveillance followed by an audit of practices and feedback are essential. Reduction of blood culture contamination is important patient safety and quality intervention which lowers the risk of patient's exposure to unnecessary antimicrobial agents and their untoward side effects and prevents waste of laboratory resources.
| Conclusion|| |
Despite its limitations, blood culture remains the gold standard for the detection of bacteraemia. Hence, controlling contamination is essential to ensure effective utilisation of this service. Implementation of BCC bundle along with root cause analysis, training, surveillance audits and feedback can significantly reduce blood culture contamination. Targeted interventions are the key to enhance patient care, help hospitals to utilise laboratory facilities and other clinical resources more efficiently and make caregivers responsible stewards of antimicrobial use.
Financial support and sponsorship
Hospital Infection Control team, Microbiology Laboratory.
Conflicts of interest
There is no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]