Positive Blood Culture Bottles Research Articles

Rapid identification and susceptibility testing of positive blood culture caused by gram negative bacteria

Objective To reduce the turnaround time for laboratory diagnosis of bacteremia, the feasibility of rapid identification and susceptibility testing using samples taken directly from positive blood culture bottles was evaluated. Methods The growth of microorganisms in blood culture bottles was screened by the BACTEC 9000 blood culture system. 65 positive blood culture bottles containing gram-negative bacteria were adopted to test. Culture fluid was injected into BD SST vacutainer and centrifuged to pellet blood cells. After collecting required McFarland units, they were cultured on Phoenix 100 NMIC/ID-4(identification-gram-negative bacteria and susceptibility testing) cards using 0.25 McF and 0.5 McF methods respectively. They were also evaluated by the standard method, involving subculture tests from positive blood culture bottles. Results 63 of 65 gram-negative bacteria (96. 9% ) were correctly identified with 0. 25 McF method. 59 of 65 gram-negative bacteria(90.8% ) were correctly identified with 0.5 McF method. For antimicrobial susceptibility testing, the 0.25 McF direct method had an agreement rate more than 94% , the 0.5 McF method was more than 85.7% and direct blood sample KB method was more than 93.8% compared to the standard method. But the overall minor error rate in susceptibility testing of direct blood sample KB method is higher than other methods. Conclusion Applying 0. 25 McF and 0. 5 McF rapid identification and susceptibility test was practical. During to possessing more prominent advantages, laboratory put the 0. 25 McF direct method into practice had a timely, remarkable significance. Key words: Positive blood culture; Joint use; Rapid identification and susceptibility testing

A 1.5 Hour Procedure for Identification of <em>Enterococcus</em> Species Directly from Blood Cultures

Enterococci are a common cause of bacteremia with E. faecalis being the predominant species followed by E. faecium. Because resistance to ampicillin and vancomycin in E. faecalis is still uncommon compared to resistance in E. faecium, the development of rapid tests allowing differentiation between enterococcal species is important for appropriate therapy and resistance surveillance. The E. faecalis OE PNA FISH assay (AdvanDx, Woburn, MA) uses species-specific peptide nucleic acid (PNA) probes in a fluorescence in situ hybridization format and offers a time to results of 1.5 hours and the potential of providing important information for species-specific treatment. Multicenter studies were performed to assess the performance of the 1.5 hour E. faecalis/OE PNA FISH procedure compared to the original 2.5 hour assay procedure and to standard bacteriology methods for the identification of enterococci directly from a positive blood culture bottle.

A 1.5 Hour Procedure for Identification of <em>Enterococcus</em> Species Directly from Blood Cultures

Enterococci are a common cause of bacteremia with E. faecalis being the predominant species followed by E. faecium. Because resistance to ampicillin and vancomycin in E. faecalis is still uncommon compared to resistance in E. faecium, the development of rapid tests allowing differentiation between enterococcal species is important for appropriate therapy and resistance surveillance. The E. faecalis OE PNA FISH assay (AdvanDx, Woburn, MA) uses species-specific peptide nucleic acid (PNA) probes in a fluorescence in situ hybridization format and offers a time to results of 1.5 hours and the potential of providing important information for species-specific treatment. Multicenter studies were performed to assess the performance of the 1.5 hour E. faecalis/OE PNA FISH procedure compared to the original 2.5 hour assay procedure and to standard bacteriology methods for the identification of enterococci directly from a positive blood culture bottle.

Rapid Identification of Gram-Negative Bacteria with and without CTX-M Extended-Spectrum β-Lactamase from Positive Blood Culture Bottles by PCR Followed by Microchip Gel Electrophoresis

We evaluated the usefulness of PCR analysis of the 16S-23S rRNA gene internal transcribed spacer (ITS) and the CTX-M extended-spectrum β-lactamase (ESBL) followed by microchip gel electrophoresis (MGE) for direct identification and CTX-M detection of Gram-negative bacteria (GNB) from positive blood culture bottles. Of 251 GNB isolated from blood cultures containing a single bacterium, 225 (90%) were correctly identified at the species level directly from positive blood culture bottles by comparing the ITS-PCR patterns of the sample strain with those of the control strains. There were no cases of incorrect identification. Limitations encountered included the inability to detect mixed cultures (four bottles) as well as some species (Enterobacter species and Klebsiella oxytoca) demonstrating identical ITS-PCR patterns. A total of 109 ESBL-producing isolates from various clinical materials obtained between January 2005 and December 2008 were examined for bla(CTX-M), bla(SHV), and bla(TEM) genes by PCR and sequences of PCR products. CTX-M ESBL was detected in 105 isolates, and SHV ESBL was detected in two isolates. The remaining two isolates (K. oxytoca) were shown to harbor bla(OXY.) Twenty (19%) of 104 Escherichia coli isolates from blood cultures were suspected to produce ESBL by the combination disk method, and these isolates were shown to harbor CTX-M ESBL by PCR-MGE. The results were obtained within 1.5 h at a calculated cost of $6.50 per specimen. In conclusion, simultaneous detection of ITS length polymorphisms and bla(CTX)-(M) by single PCR followed by MGE is useful for rapid, cost-effective, and reliable species-level identification of CTX-M ESBL-producing GNB responsible for bloodstream infections.

The sensitivity of direct identification from positive BacT/ALERT™ (bioMérieux) blood culture bottles by matrix-assisted laser desorption ionization time-of-flight mass spectrometry is low

Recently, matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been presented as a novel method for the direct identification of bacteria from positive blood culture bottles. The rate of the MALDI TOF MS-based identification in the present study from positive BacT/ALERT (bioMérieux, Marcy l'Etoile, France) blood culture bottles was 30%, which is far below the previously reported sensitivities using the BACTEC (Becton Dickinson, Franklin Lakes, NJ, USA) system. We also found evidence that the Biotyper algorithm did not identify a second pathogen in cases of positive BacT/ALERT blood culture bottles containing two different species.

Validation of two methods for the identification of bacteria directly from blood cultures with the MALDI-TOF technique

Aim We validated two methods for the direct identification of bacteria from positive BACTEC blood culture bottles with the MALDI-TOF technique. Methods 872 blood culture bottles positive with the BACTEC system (BD) were tested. For MALDI-TOF identification two specimen collection and blood cell extraction methods were tested [Method 1: Vacutainer serum seperator tubes (BD); Method 2: MALDI Sepsityper Solutions (Bruker)]. For both methods, bacterial proteins were extracted by the formic acid/ acetonitrile standard method and measured in a MALDI-TOF spectrometer of the FLEX series (Bruker Daltonics). Identification results were compared to routine biochemical methods (VITEK 2, api-system, BioMe´rieux). Results Of 789 blood cultures tested with Method 1, 636 (80%) showed a valid (score value > 1,7) identification result with the MALDI-TOF. Of these valid samples, 630 (99%) were correctly identified to species level in comparison to routine biochemical methods. For Method 2, 83 blood cultures were tested, 75 (80%) were considered as valid, 99% showed a correct result to species level. Discussion The MALDI-TOF technique proved to be a fast and reliable method for the detection of bacteria directly from BACTEC blood culture bottles. Results are available 1–2 days earlier in comparison to conventional methods. We validated two methods for the direct identification of bacteria from positive BACTEC blood culture bottles with the MALDI-TOF technique. 872 blood culture bottles positive with the BACTEC system (BD) were tested. For MALDI-TOF identification two specimen collection and blood cell extraction methods were tested [Method 1: Vacutainer serum seperator tubes (BD); Method 2: MALDI Sepsityper Solutions (Bruker)]. For both methods, bacterial proteins were extracted by the formic acid/ acetonitrile standard method and measured in a MALDI-TOF spectrometer of the FLEX series (Bruker Daltonics). Identification results were compared to routine biochemical methods (VITEK 2, api-system, BioMe´rieux). Of 789 blood cultures tested with Method 1, 636 (80%) showed a valid (score value > 1,7) identification result with the MALDI-TOF. Of these valid samples, 630 (99%) were correctly identified to species level in comparison to routine biochemical methods. For Method 2, 83 blood cultures were tested, 75 (80%) were considered as valid, 99% showed a correct result to species level. The MALDI-TOF technique proved to be a fast and reliable method for the detection of bacteria directly from BACTEC blood culture bottles. Results are available 1–2 days earlier in comparison to conventional methods.

MALDI-TOF mass spectrometry: the quantum leap

With this special issue on the matrix-assisted laser desorption-ionization time-of-flight (MALDI-TOF) mass spectrometry, our aim is that infectious diseases specialists and microbiologists not yet familiar with this new tool will appreciate the importance of this ‘magical laser’ for microbial identification. We hope that even specialists will appreciate this overview on this new technology and its applications, since MALDI-TOF mass spectrometry really represents a quantum leap in diagnostic microbiology. In their review article, Emonet et al. thoroughly explain how MALDI-TOF mass spectrometry allows identification of bacterial species available in pure culture. They also compare the different mass spectrometer specifically adapted to routine microbiology laboratories and discuss their respective advantages and disadvantages. Then, they nicely present two other recent mass spectrometry-based tools, i.e. the MALDI-resequencing (MALDI-RE) and the association of a new broad-range PCR approach coupled with the analysis of generated amplicons by electrospray ionization mass spectrometry (PCR-ESI-MS), that allows better discrimination of strains and may be performed directly on clinical samples without a culture-based amplification step. In the second article of this special issue, Bizzini and I present the performance of MALDI-TOF mass spectrometry in routine setting. Although current protocols allow accurate identification of most strains routinely isolated in clinical microbiology laboratories, some clades will repeatedly be misidentified due to poor quality of databases or due to the close relatedness of different species (i.e. within the Streptococcus genus; or between E. coli and Shigella species). Despite these limitations, MALDI-TOF mass spectrometry really appears as a quantum leap in diagnostic microbiology that significantly reduce the time to results and costs of microbial identification. The benefit of protein extraction is also discussed in this review as well as some future possible applications such as the search for virulence factors and/or for some antibiotic resistance determinants. In the article by M. Drancourt, the usefulness of MALDI-TOF mass spectrometry for direct bacterial identification starting from positive blood culture bottles is discussed. This approach was successful in various laboratories using different protocols. In the near future, it will be important to further improve the identification, especially of Gram positive cocci and to precise the clinical impact of such rapid identification of the etiological agents of bacteremia. Then, in the last article of this special issue, P. Murray presents an overview of the usefulness of MALDI-TOF mass spectrometry for taxonomy and epidemiology. Based on the literature currently available, it appears that MALDI-TOF mass spectrometry may be used for microbial identification at the subspecies level and might even prove to be as discriminative then pulse-field gel electrophoresis (PFGE) for some selected species. However, protein extraction and precise protein calibration seems important to obtain reliable results at subspecies, type and subtypes levels. This ‘magic laser’ technology will also have applications in the future in the taxonomy of obligate intracellular bacteria such as members of the Rickettsiales and Chlamydiales order, for which no or little phenotypic traits are available, given their strict intracellular growth. Although current protocols allows accurate identification of most strains routinely isolated in clinical microbiology laboratories, there are still much place for improvement, especially in the quality and completeness of databases and in the quality control of the process. Thus, as an example, it may be important to check the MALDI-TOF microplate for the absence of residual trace of proteins on cleaned microplates. The performance of the extraction step and of the MALDI-TOF mass spectrometer needs although to be daily checked by routinely testing a few selected bacterial ATCC strains with and without a specific extraction step. Thank to this special issue on MALDI-TOF mass spectrometry, you will surf from technical aspects to the application of this quantum leap technology allowing accurate, easy and cheap microbial identification and, to some extent, straightforward typing. The author has no conflicts of interest to declare.

Study of a novel method to assist in early reporting of sepsis from the microbiology laboratory

Microbiology laboratories must provide accurate blood culture reports with rapid turnaround time (TAT) to effectively manage patients with sepsis. In this study three methods are compared for reporting blood culture results: a manual method that included use of a serum separator tube (SST), the conventional manual, and an automated method for identification and susceptibility (ID/AST). Broth from positive blood culture bottles was added to an SST and then centrifuged. The pellet obtained was used to directly inoculate biochemical tests for identification and agar plates for AST on the first day of positivity. Biochemicals and AST plates were read the next day and final results reported on the second day at 24 hours. For conventional disk diffusion testing, the newly positive blood culture broth was also inoculated on solid media on the first day and incubated overnight. The next day AST by was performed as well as biochemical tests from pure colonies. These colonies were also used to inoculate panels for ID/AST using the automated MicroScan 40SI System. These results were recorded on the third day and results reported at 48 hours. The study included 851 samples Out of 106 (12.4%) positive blood cultures, 102 were included in the study; Comparison of the 3 methods showed good correlation. Identification was correctly reported in 95 (93.1%) isolates. The overall AST error rate was 3.8%. The use of SST and direct from pellet inoculation reduced TAT for identification and AST results between 18 and 24 hours.

Rapid identification of yeasts from positive blood culture bottles by pyrosequencing

We have developed a rapid protocol for the identification of Candida species from positive blood cultures by combining a simple method for nucleic acid extraction and preparation using microbial storage cardboards with polymerase chain reaction (PCR) and pyrosequencing of a small region of the 18S rRNA gene. The protocol is robust and easy to implement and can be performed in 4 h. The method was tested against a collection of clinical blood cultures. Agreement of sequence identifications with standard microbiological methods was 100%.

Rapid Identification of Bacterial Pathogens in Positive Blood Culture Bottles by Use of a Broad-Based PCR Assay Coupled with High-Resolution Melt Analysis

We evaluated a broad-based PCR assay coupled with high-resolution melt analysis for rapid bacterial identification in patients with bacterial sepsis. With a reference library of 60 clinically relevant bacterial species, 52 positive blood culture samples were tested. Our assay identified 46/52 samples at the species level, with 100% concordance to culture findings.

Pitfalls in the rapid diagnosis of positive blood culture

Bacteraemia and sepsis are among the most serious health problems with an incidence that is increasing worldwide, and brings about considerable economic burden. Blood cultures have traditionally been considered as the gold standard and are of great diagnostic value in defining bacteraemia and sepsis. The introduction of automated blood culture systems has provided continuous growth monitoring and improved the yield and shortened the time to positivity. When blood cultures turn positive, how to process the positive blood culture bottles is an important task for the microbiological laboratory. Technicians are challenged to process flagged positive blood culture at different circumstances. This article addresses relevant pitfalls associated with positive blood culture. Microbiological laboratory should have guidelines and strategies that can provide appropriate handling of positive blood culture.

Blood culture gram stain, acridine orange stain and direct sensitivity-based antimicrobial therapy of bloodstream infection in patients with trauma

Purpose: The purpose of this study was to ascertain if the simple practice of Gram stain, acridine orange stain and direct sensitivity determination of positive blood culture bottles could be used to guide early and appropriate treatment in trauma patients with clinical suspicion of sepsis. The study also aimed to evaluate the error in interpreting antimicrobial sensitivity by direct method when compared to standard method and find out if specific antibiotic–organism combination had more discrepancies. Findings from consecutive episodes of blood stream infection at an Apex Trauma centre over a 12-month period are summarized. Materials and Methods: A total of 509 consecutive positive blood cultures were subjected to Gram staining. AO staining was done in BacT/ALERT-positive Gram-stain negative blood cultures. Direct sensitivity was performed from 369 blood culture broths, showing single type of growth in Gram and acridine orange staining. Results of direct sensitivity were compared to conventional sensitivity for errors. Results: No ‘very major’ discrepancy was found in this study. About 5.2 and 1.8% minor error rates were noted in gram-positive and gram-negative bacteria, respectively, while comparing the two methods. Most of the discrepancies in gram-negative bacteria were noted in β lactam – β lactamase inhibitor combinations. Direct sensitivity testing was not reliable for reporting of methicillin and vancomycin resistance in Staphylococci. Conclusions: Gram stain result together with direct sensitivity testing is required for optimizing initial antimicrobial therapy in trauma patients with clinical suspicion of sepsis. Gram staining and AO staining proved particularly helpful in the early detection of candidaemia.

Rapid Identification of Bacteria from Positive Blood Culture Bottles by Use of Matrix-Assisted Laser Desorption-Ionization Time of Flight Mass Spectrometry Fingerprinting

Early and adequate antimicrobial therapy has been shown to improve the clinical outcome in bloodstream infections (BSI). To provide rapid pathogen identification for targeted treatment, we applied matrix-assisted laser desorption-ionization time of flight (MALDI-TOF) mass spectrometry fingerprinting to bacteria directly recovered from blood culture bottles. A total of 304 aerobic and anaerobic blood cultures, reported positive by a Bactec 9240 system, were subjected in parallel to differential centrifugation with subsequent mass spectrometry fingerprinting and reference identification using established microbiological methods. A representative spectrum of bloodstream pathogens was recovered from 277 samples that grew a single bacterial isolate. Species identification by direct mass spectrometry fingerprinting matched reference identification in 95% of these samples and worked equally well for aerobic and anaerobic culture bottles. Application of commonly used score cutoffs to classify the fingerprinting results led to an identification rate of 87%. Mismatching mostly resulted from insufficient bacterial numbers and preferentially occurred with Gram-positive samples. The respective spectra showed low concordance to database references and were effectively rejected by score thresholds. Spiking experiments and examination of the respective study samples even suggested applicability of the method to mixed cultures. With turnaround times around 100 min, the approach allowed for reliable pathogen identification at the day of blood culture positivity, providing treatment-relevant information within the critical phase of septic illness.

Triplex real-time polymerase chain reaction assay for simultaneous detection of Staphylococcus aureus and coagulase-negative staphylococci and determination of methicillin resistance directly from positive blood culture bottles

We describe here a 1-step, triplex real-time polymerase chain reaction (PCR) assay for the detection and identification of staphylococci directly from signal-positive blood culture bottles containing Gram-positive cocci in clusters (GPCC). The triplex assay targeted and detected tuf, nuc, and mecA genes in a single tube and had a detection limit of 10 5 CFU/mL for each gene target. A total of 341 GPCC-positive blood culture bottles were collected between November 12, 2008, and August 11, 2009. Among them, 230 methicillin-resistant coagulase-negative staphylococci (CoNS), 54 methicillin-susceptible CoNS, 22 methicillin-resistant Staphylococcus aureus, 22 methicillin-susceptible S. aureus, and 13 nonstaphylococci species were identified by conventional methods. The results obtained by triplex assay were in agreement with those of conventional methods for tuf (99.7%), nuc (100.0%), and mecA (99.1%), respectively. The triplex assay was found to have sensitivities of 99.7%, 100%, and 99.2% and specificities of 100%, 100%, and 98.7%, respectively, for the tuf, nuc, and mecA gene targets. The triplex real-time PCR assay accurately detects and identifies staphylococci directly from positive blood cultures without nucleic acid extraction prior to amplification.

Evaluation of the alkaline wash/lysis procedure for the molecular diagnosis of a positive bacterial blood culture in clinical routine practice

Blood culture is commonly used to detect microorganisms in patients with a suspected blood infection. This study evaluated the alkaline wash/lysis procedure to extract DNA of microorganisms in a clinical blood culture. A multiplex polymerase chain reaction (PCR) targeting the 16S rDNA (ribosomal DNA) gene and the fungal ITS (internal transcribed spacer) gene was used as a reliable indicator for the presence of microorganism DNA in the extracts. A total of 535 BacT/ALERT positive blood culture bottles were evaluated. Multiplex PCR showed positive results in 530 DNA extracts, but 5 DNA extracts gave negative results. We conclude that the alkaline wash/lysis procedure in combination with the multiplex PCR is a simple and sensitive method, which can be used in a standard diagnostic laboratory to detect microorganisms in blood culture material.

Direct Identification of Bacteria in Positive Blood Culture Bottles by Matrix-Assisted Laser Desorption Ionisation Time-of-Flight Mass Spectrometry

BackgroundWith long delays observed between sampling and availability of results, the usefulness of blood cultures in the context of emergency infectious diseases has recently been questioned. Among methods that allow quicker bacterial identification from growing colonies, matrix-assisted laser desorption ionisation time-of-flight (MALDI-TOF) mass spectrometry was demonstrated to accurately identify bacteria routinely isolated in a clinical biology laboratory. In order to speed up the identification process, in the present work we attempted bacterial identification directly from blood culture bottles detected positive by the automate.Methodology/Principal FindingsWe prospectively analysed routine MALDI-TOF identification of bacteria detected in blood culture by two different protocols involving successive centrifugations and then lysis by trifluoroacetic acid or formic acid. Of the 562 blood culture broths detected as positive by the automate and containing one bacterial species, 370 (66%) were correctly identified. Changing the protocol from trifluoroacetic acid to formic acid improved identification of Staphylococci, and overall correct identification increased from 59% to 76%. Lack of identification was observed mostly with viridans streptococci, and only one false positive was observed. In the 22 positive blood culture broths that contained two or more different species, only one of the species was identified in 18 samples, no species were identified in two samples and false species identifications were obtained in two cases. The positive predictive value of bacterial identification using this procedure was 99.2%.Conclusions/SignificanceMALDI-TOF MS is an efficient method for direct routine identification of bacterial isolates in blood culture, with the exception of polymicrobial samples and viridans streptococci. It may replace routine identification performed on colonies, provided improvement for the specificity of blood culture broths growing viridans streptococci is obtained in the near future.

Multiplex PCR-Ligation Detection Reaction Assay for Simultaneous Detection of Drug Resistance and Toxin Genes from Staphylococcus aureus , Enterococcus faecalis , and Enterococcus faecium

A multiplex PCR-ligation detection reaction (PCR-LDR) assay was developed for rapid detection of methicillin, tetracycline, and vancomycin resistance, as well as toxic shock toxin and Panton-Valentine leukocidin. The assay was tested on 470 positive blood culture bottles containing Staphylococcus aureus or enterococci. PCR-LDR exhibited a sensitivity and specificity of > or = 98% for all components except tetracycline resistance, which had a sensitivity of 94.7%. Rapid and sensitive detection of antimicrobial resistance and virulence genes could help guide therapy and appropriate infection control measures.

Enhanced detection of staphylococcal genomes in positive blood cultures using a polymeric enzyme complex

This article describes a simple and inexpensive signal amplification method, termed polymeric enzyme detection (PED), which permits rapid and sensitive detection of conserved sequences in the tuf gene that identify Staphylococcus genus, conserved sequences in the femB gene that specifically detect Staphylococcus aureus species, and the methicillin resistance gene mecA directly from positive blood culture bottles. Microbe-specific capture probes were immobilized onto microtiter plates or silicon chips. Target sequences and biotin-labeled, target-specific probes were hybridized to complementary capture probes to create a biotin-labeled, surface-immobilized tripartite complex. In a two-step process, signal was amplified by incubating the surface-immobilized biotin with streptavidin followed by the addition of a 500-kDa dextran polymer conjugated with approximately 80 biotins. Signal was then developed by binding of a streptavidin–horseradish peroxidase conjugate followed by incubation with the substrate tetramethylbenzidine. Use of the PED method improved the lower limit of detection 10- to 100-fold in model DNA hybridization assays with limits of detection as low as 1fmol/L target DNA. This level of sensitivity permits detection of genomic DNA from methicillin-resistant S. aureus positive blood cultures within 25 to 35min using either a thin film biosensor chip or a microtiter plate-based assay.

Apport du test GeneOhm StaphSR® (Becton Dickinson) pour la prise en charge des patients infectés par Staphylococcus aureus

We evaluated the impact of identification in 2 h directly on positive blood cultures bottles of Staphylococcus aureus associated with mecA gene detection by GeneOhm StaphSR ® test (GOSSR) on the delay of optimal treatment and on the isolation of the methicillin-resistant S. aureus -infected patients (SARM). Sixty-nine blood cultures positives for staphylococci at direct exam corresponding to 62 patients were tested for: GOSSR, culture with identification, antibiotic susceptibility and result of SARM colonization. Seventeen blood cultures were positive for S. aureus : 10 strains susceptible to meticilline and seven resistant. Results of GOSSR were according to phenotypic results in 15/17. Despite two discordant cases (resistant strain not detected), this test allowed: to avoid the administration of vancomycine for six patients, to reduce duration of vancomycine therapy for one patient and to know SARM colonization for two patients. Nous avons évalué l’impact de l’identification de Staphylococcus aureus , en deux heures directement sur le flacon d’hémoculture positif, associée à la détection du gène mecA par le test GeneOhm StaphSR ® (GOSSR) sur le délai d’instauration d’une antibiothérapie adaptée et la mise en isolement du patient infecté par S. aureus résistant à la méticilline (SARM). Soixante-neuf hémocultures avec staphylocoques à l’examen direct chez 62 patients, sur lesquels ont été réalisés : GOSSR, culture avec identification, antibiogramme et recueil du résultat du portage de SARM. Dix-sept hémocultures étaient positives à S. aureus : dix sensibles à la méticilline et sept résistantes. Le test GOSSR a permis de les identifier dans 15/17. Malgré deux cas discordants (résistance à la méticilline non détectée), ce test a permis d’éviter l’administration de vancomycine pour six patients, de réduire la durée de son administration pour un patient et de placer en isolement septique deux patients dont la colonisation à SARM était inconnue.

Blood Culture Techniques: Increasing Yields and Reducing Contamination

Bloodstream infections are associated with significant patient mortality and health care costs. Isolation of the causative organism will direct the clinician to institute specific treatment. But isolation of the implicating organism is hampered by lack of yield and increased level of contamination. The rates of contamination and reduced yield are more relevant in Sri Lanka as most of our public sector laboratories use manual blood culture system and do not adhere to correct aseptic techniques of blood collection. This has led to delay in identifying the causative organism. Increase rates of contamination not only have hindered specific treatment but also have prompted clinicians to use antibiotics of increased cost and toxicity. Though differentiation between true pathogen and contamination is not clearly set, certain parameters, namely identification of the organism, proportion of the positive blood culture sets, Number of positive blood culture bottles within a blood culture set, time to growth, source of cultures (catheter drawn versus percutaneous) along with clinical and laboratory clues might help the clinicians and microbiologist to make a reasonable conclusion. Proper skin preparation with correct disinfectants, adherence to recommended techniques and contact time along with the collection of optimal volume of blood through a peripheral vein by a trained phlebotomy team has been found to increase the yield and reduce the rates of contamination. These recommendations could be practiced with ease in resource poor settings similar to Sri Lankan public sector hospitals.Keywords: Blood culture; infectionsCitation: Chinniah TR. Blood Culture Techniques: Increasing Yields and Reducing Contamination. Sri Lanka Journal of Critical Care 2009;1:15-24DOI: 10.4038/sljcc.v1i1.938