Review on evaluations of currently available blood-culture systems.

Abstract

The choice of a blood-culture system to be used in a medical institution depends mainly on the financial resources. The most economic but not necessarily optimal system would probably be the in-house production of adequately supplemented aerobic and anaerobic broth media. Laboratories processing only limited numbers of blood cultures may choose one of the manual blood-culture systems, but automated systems like one of the continuous-monitoring blood-culture systems described below should be favored. This review is introduced with general considerations on blood-culture evaluations before the description of the most commonly known and used blood-culture systems followed by an overview of the results obtained with these. A blood-culture system can be selected based on scientific reports as a supplement to commercial arguments. One of the most challenging tasks facing clinical microbiologists is the validation of new blood-culture systems [1Elder BL Hansen SA Kellogg JA Marsik FJ Zabransky RJ McCurdy BW Cumitech 31, Verification and validation of procedures in the clinical microbiology laboratory. American Society for Microbiology, Washington, DC1997Google Scholar]. For the ideal clinical comparative evaluation, drawing of additional blood from each patient for parallel testing is not always possible. In addition, about 90% of blood cultures are normally negative, and therefore of no value for a comparison. Moreover, up to 3% of the microorganisms isolated are considered to be contaminants (Figure 1, Figure 2). A wide range of more than 20 different microbial species considered to be clinically relevant, including yeasts, anaerobes, and fastidious organisms, should be isolated during an evaluation. To test the ability of automated systems in detecting positive cultures, at least 500 cultures determined to be negative by the instrument should be blindly subcultured at the end of the incubation period. Instrument performance may be considered acceptable when >98% of all blood-culture vials positive on subcultures are detected by the instrument [1Elder BL Hansen SA Kellogg JA Marsik FJ Zabransky RJ McCurdy BW Cumitech 31, Verification and validation of procedures in the clinical microbiology laboratory. American Society for Microbiology, Washington, DC1997Google Scholar]. A French working group recommended the evaluation of about 1000 blood-culture sets with systematic subcultures of all vials to be included in any study. The subculture result is proposed to be the microbiological reference, so that sensitivity, specificity and positive and negative predictive values can be calculated for a new automated blood-culture system [2Mathieu D Nguyen J Grenier B Véron M Recommandations pour l'évaluation des automates pour hémocultures.Bull Soc Fr Microbiol. 1994; 9: 179-185Google Scholar].Figure 2Yield of pathogens and contamination rate of BACTEC Plus aerobic/F vials related to the volume of blood cultured (average=7.3±2 mL), during the study performed at the University Hospital Geneva [18Rohner P Pepey B Auckenthaler R Comparative evaluation of BACTEC aerobic Plus/F and Septi-Chek Release blood culture media.J Clin Microbiol. 1996; 34: 126-129PubMed Google Scholar].View Large Image Figure ViewerDownload (PPT) For the approval of blood-culture systems, the FDA guidelines require a comparison of recovery of at least 600 clinically important isolates from over 370 different septic episodes [3Wilson ML Blood cultures. Introduction.Clin Lab Med. 1994; 14: 1-7PubMed Google Scholar]. Since the positivity rate is directly related to the volume of blood cultured [4Li J Plorde JJ Carlson LG Effects of volume and periodicity on blood cultures.J Clin Microbiol. 1994; 32: 2829-2831PubMed Google Scholar, 5Reller LB Murray PR MacLowry JD Washington JA Cumitech 1A, Blood cultures II. American Society for Microbiology, Washington, DC1982Google Scholar, 6Dunne WM Nolte FS Wilson ML Hindler JA Cumitech 1B, Blood cultures III. American Society for Microbiology, Washington, DC1997Google Scholar, 7Weinstein MP Mirrett S Wilson ML Reimer LG Reller LB Controlled evaluation of 5 versus 10 milliliters of blood cultured in aerobic BacT/Alert blood culture bottles.J Clin Microbiol. 1994; 32: 2103-2106PubMed Google Scholar, 8Rohner P Delaspe O Ruiz I Auckenthaler R Comparison of Roche Septi-Chek, Oxoid Signal and BioMérieux Hémoline blood culture systems [abstract 203/OS11].in: Abstracts of the 4th European Congress of Clinical Microbiology. European Society of Clinical Microbiology and Infectious Diseases, Paris1989: 103Google Scholar, 9Rohner P Auckenthaler R Comparative evaluation of the BCB Roche and Oxoid Signal blood culture systems.Eur J Clin Microbiol Infect Dis. 1989; 8: 150-153Crossref PubMed Scopus (7) Google Scholar] (Figure 1, Figure 2), the volume of blood inoculated into each vial must be controlled so that inadequately filled bottles can be excluded from the evaluations. Therefore, at least 8000 blood-culture sets should be evaluated, assuming positivity rates of 6–16%, an acceptable contamination rate of up to 4% (Table 1, Table 2, Table 3), and about 80% compliant sets, depending on the institutions [3Wilson ML Blood cultures. Introduction.Clin Lab Med. 1994; 14: 1-7PubMed Google Scholar]. Since no blood-culture system may be considered as an absolute reference, sensitivities and specificities cannot be accurately calculated [3Wilson ML Blood cultures. Introduction.Clin Lab Med. 1994; 14: 1-7PubMed Google Scholar, 10Ilstrup DM Statistical methods in microbiology.Clin Microbiol Rev. 1990; 3: 219-226PubMed Google Scholar]. A new blood-culture system should be compared to a system already approved by the FDA. The new system may be considered validated if it detected >95% of the microorganisms detected by the reference system [1Elder BL Hansen SA Kellogg JA Marsik FJ Zabransky RJ McCurdy BW Cumitech 31, Verification and validation of procedures in the clinical microbiology laboratory. American Society for Microbiology, Washington, DC1997Google Scholar]. However, earlier studies of manual blood-culture systems evaluating less than 5000 blood-culture sets remain useful, even though statistical conclusions may not be as firm as for recent, well-controlled evaluations where >8000 blood-culture sets were evaluated (Table 1, Table 2, Table 3).Table 3Study design and results achieved in selected evaluations comparing automated blood‐culture systemsPercentagePathogens isolated from:System AMedium ASystem BMedium BNumber testedPositiveContaminatedSystem A and system BSystem A onlySystem B only% difference A to BP valueaP values were calculated applying the McNemar exact test [14]; P values >0.05 not significant (NS).ReferenceBacT/AlertAerobic and anaerobic standardBACTEC 9000Plus aerobic/F and Plus anaerobic/F463219.54.24875416420.3<0.0001[30Auckenthaler R Rohner P Bernard D et al.Continuous monitoring blood culture systems.in: Program of the 6th European Congress of Clinical Microbiology. European Society of Clinical Microbiology and Infectious Diseases, Paris1993: 36Google Scholar]BacT/AlertAerobic and anaerobic standardBACTEC 9000Plus anaerobic/F Plus aerobic/F and64378.52.63696015722.6<0.0001[24Smith JA Bryce EA Ngui Yen JH Roberts FJ Comparison of BACTEC 9240 and BacT/Alert blood culture systems in an adult hospital.J Clin Microbiol. 1995; 33: 1905-1908PubMed Google Scholar]BacT/AlertAerobic and anaerobic FANBACTEC 900Plus aerobic/F and Plus anaerobic/F440221.58.148210180‐3.60.14 NS[91Ziegler R Johnscher I Martus P Lenhardt D Just HM Controlled clinical laboratory comparison of two supplemented aerobic and anaerobic media used in automated blood culture systems to detect bloodstream infections.J Clin Microbiol. 1998; 36: 657-661PubMed Google Scholar]BacT/AlertAerobic FANBacT/AlertAerobic standard684711.94.028914862‐19.7<0.0001[15Weinstein MP Mirrett S Reimer LG et al.Controlled evaluation of BacT/alert standard aerobic and FAN aerobic blood culture bottles for the detection of bacteremia and fungemia.J Clin Microbiol. 1995; 33: 978-981PubMed Google Scholar]BacT/AlertAerobic FANBACTEC 9000Plus aerobic/F719013.73.3232114110‐1.20.84 NS[23Pohlman JK Kirkley BA Easley KA Basille BA Washington JA Controlled clinical evaluation of BACTEC Plus Aerobic/F and BacT/Alert Aerobic FAN bottles for detection of bloodstream infections.J Clin Microbiol. 1995; 33: 2856-2858PubMed Google Scholar]BacT/AlertAerobic FANBACTEC 9000Plus aerobic/F740113.94511261432.90.33 NS[21Jorgensen JH Mirrett S McDonald LC et al.Controlled clinical laboratory comparison of BACTEC Plus aerobic/F resin medium with BacT/Alert aerobic FAN medium for detection of bacteremia and fungemia.J Clin Microbiol. 1997; 35: 53-58PubMed Google Scholar]BacT/AlertAerobic FANESP80A66361776962‐2.80.6 NS[29Welby-Sellenriek PL Keller DS Ferrett RJ Storch G Comparison of the BacT/Alert FAN aerobic and the DIFCO ESP 80A aerobic bottles for pediatric blood cultures.J Clin Microbiol. 1997; 35: 1166-1171PubMed Google Scholar]BacT/AlertAerobic FANESP80A630612.25.430112663‐14.8<0.0001[90Doern GV Barton A Rao S Controlled comparative evaluation of BacT/Alert FAN and ESP 80A aerobic media as means for detecting bacteremia and fungemia.J Clin Microbiol. 1998; 36: 2686-2689PubMed Google Scholar]BacT/AlertAerobic standardBacT/AlertAnaerobic standard556612.32.94378464‐3.80.12 NS[17Rohner P Pepey B Auckenthaler R Comparison of BacT/Alert with Signal blood culture system.J Clin Microbiol. 1995; 33: 313-317PubMed Google Scholar]BacT/AlertAerobic standardBacT/AlertAnaerobic standard1228910.6793309204‐9.5<0.0001[85Bannister ER Woods GL Evaluation of routine anaerobic blood cultures in the BacT/Alert blood culture system.Am J Clin Pathol. 1995; 104: 279-282Crossref PubMed Scopus (19) Google Scholar]BacT/AlertAerobic standardBACTEC NRbNR includes non‐radioactive BACTEC instruments 660, 730 and 860.NR6A59186.22307659‐5.60.17 NS[87Wilson ML Weinstein MP Reimer LG Mirrett S Reller L Controlled comparison of the BacT/Alert and BACTEC 660/730 nonradiometric blood culture systems.J Clin Microbiol. 1992; 30: 323-329PubMed Google Scholar]BacT/AlertAerobic standardESP80 A54218.020845689.10.04[88Zwadyk P Pierson CL Young C Comparison of Difco ESP and Organon Teknika BacT/Alert continuous-monitoring blood culture systems.J Clin Microbiol. 1994; 32: 1273-1279PubMed Google Scholar]BacT/AlertAnaerobic FANBacT/AlertAnaerobic standard769410.53.031614596‐10.60.002[16Wilson ML Weinstein MP Mirrett S et al.Controlled evaluation of BacT/alert standard anaerobic and FAN anaerobic blood culture bottles for the detection of bacteremia and fungemia.J Clin Microbiol. 1995; 33: 2265-2270PubMed Google Scholar]BacT/AlertAnaerobic standardBACTEC NRbNR includes non‐radioactive BACTEC instruments 660, 730 and 860.NR7A59925.62047657‐6.80.12 NS[87Wilson ML Weinstein MP Reimer LG Mirrett S Reller L Controlled comparison of the BacT/Alert and BACTEC 660/730 nonradiometric blood culture systems.J Clin Microbiol. 1992; 30: 323-329PubMed Google Scholar]BacT/AlertAnaerobic standardESP80 N50356.6150345712.50.02[88Zwadyk P Pierson CL Young C Comparison of Difco ESP and Organon Teknika BacT/Alert continuous-monitoring blood culture systems.J Clin Microbiol. 1994; 32: 1273-1279PubMed Google Scholar]BacT/AlertPedi‐BacTBACTEC 9000Peds Plus/F5041238399620.6<0.0001[89Mirrett S Reller LB Adholla PO Gilligan PH Wait K Controlled comparison of BACTEC Peds Plus/F versus BacT/Alert Pedi-BacT medium for detection of bloodstream infections in pediatric patients [abstract C-434].in: Abstracts of the 97th General Meeting of the American Society for Microbiology. American Society for Microbiology, Washington, DC1997: 196Google Scholar]BACTEC NRbNR includes non‐radioactive BACTEC instruments 660, 730 and 860.26A+27ABACTEC NRbNR includes non‐radioactive BACTEC instruments 660, 730 and 860.6A+7A1234110.81.9717380114‐24.2<0.0001[25Koontz FP Flint KK Reynolds JK Allen SD Multicenter comparison of the high volume (10 ml) NR BACTEC Plus system and the standard (5 ml) NR BACTEC system.Diagn Microbiol Infect Dis. 1991; 14: 111-118Abstract Full Text PDF PubMed Scopus (26) Google Scholar]BACTEC NRbNR includes non‐radioactive BACTEC instruments 660, 730 and 860.NR 26BACTEC 9000Plus aerobic/F52829.53.02485248‐1.30.76 NS[95Schwabe LD Thomson Jr, RB Flint KK Koontz FP Evaluation of BACTEC 9240 blood culture system by using high-volume aerobic resin media.J Clin Microbiol. 1995; 33: 2451-2453PubMed Google Scholar]BACTEC NRbNR includes non‐radioactive BACTEC instruments 660, 730 and 860.Peds Plus/FVitalAerobic62769.01.832611548‐15.2<0.0001[11Zaidi AK Mirrett S McDonald JC et al.Controlled comparison of bioMérieux VITAL and BACTEC NR-660 systems for detection of bacteremia and fungemia in pediatric patients.J Clin Microbiol. 1997; 35: 2007-2012PubMed Google Scholar]BACTEC 90006 FBACTEC NRbNR includes non‐radioactive BACTEC instruments 660, 730 and 860.NR6A93914009966‐6.60.013[92Nolte FS Williams JM Jerris RC et al.Multicenter clinical evaluation of a continuous monitoring blood culture system using fluorescent-sensor technology (BACTEC 9240).J Clin Microbiol. 1993; 31: 552-557PubMed Google Scholar]BACTEC 90007 FBACTEC NRbNR includes non‐radioactive BACTEC instruments 660, 730 and 860.NR7A895130811441‐17.3<0.0001[92Nolte FS Williams JM Jerris RC et al.Multicenter clinical evaluation of a continuous monitoring blood culture system using fluorescent-sensor technology (BACTEC 9240).J Clin Microbiol. 1993; 31: 552-557PubMed Google Scholar]BACTEC 9000Lytic anaerobic/FBACTEC 9000Standard anaerobic/F20929.34.179367‐25.2<0.0001[94Hollick GE Edinger R Martin B Clinical comparison of the BACTEC 9000 Standard Anaerobic/F and Lytic/F blood culture media.Diagn Microbiol Infect Dis. 1996; 24: 191-196Abstract Full Text PDF PubMed Scopus (8) Google Scholar]BACTEC 9000Lytic anaerobic/FBACTEC 9000Plus aerobic/F1091411.31.66112412834.90.07NS[22Rohner P Pepey B Auckenthaler R Advantage of combining resin with lytic BACTEC blood culture media.J Clin Microbiol. 1997; 35: 2634-2638PubMed Google Scholar]BACTEC 9000Plus aerobic/FBACTEC 9000Plus anaerobic/F611611.92.0420105107‐0.40.95 NS[18Rohner P Pepey B Auckenthaler R Comparative evaluation of BACTEC aerobic Plus/F and Septi-Chek Release blood culture media.J Clin Microbiol. 1996; 34: 126-129PubMed Google Scholar]BACTEC 9000Plus aerobic/F and Plus anaerobic/FVitalAerobic and anaerobic standard645612.34.135514130‐22.4<0.0001[26Lelievre H Giminez M Vandenesch F et al.Multicenter clinical comparison of resin-containing bottles with standard aerobic and anaerobic bottles for culture of microorganisms from blood.Eur J Clin Microbiol Infect Dis. 1997; 16: 669-674Crossref PubMed Scopus (19) Google Scholar]a P values were calculated applying the McNemar exact test [14McNemar Q Psychological statistics. 3rd edn. John Wiley & Sons, Inc., New York1962: 209-239Google Scholar]; P values >0.05 not significant (NS).b NR includes non‐radioactive BACTEC instruments 660, 730 and 860. Open table in a new tab The volume of blood inoculated into each vial should be determined during all blood-culture evaluations, as previously mentioned. Weighing the vials before and after the blood inoculation is the most accurate procedure. It remains the only reliable method when small volumes of blood can be obtained, in particular from pediatric patients [11Zaidi AK Mirrett S McDonald JC et al.Controlled comparison of bioMérieux VITAL and BACTEC NR-660 systems for detection of bacteremia and fungemia in pediatric patients.J Clin Microbiol. 1997; 35: 2007-2012PubMed Google Scholar], but this procedure is time-consuming. For larger volumes (>5 mL) of blood cultured from adult patients, visual comparisons of liquid levels to levels of non-inoculated vials may be sufficient. Only sets with adequately filled vials and with limited differences in volume should be included in the evaluations. The method used to determine the blood volume inoculated as well as the inclusion criteria should be well indicated in reports and publications. It is recommended to determine every identified microorganism as either the cause of sepsis, as contaminant, or indeterminate as the cause of sepsis, according to established and widely accepted criteria [12Weinstein MP Reller LB Murphy JR Lichtenstein KA The clinical significance of positive blood cultures: a comprehensive analysis of 500 episodes of bacteremia and fungemia in adults. I. Laboratory and epidemiologic observations.Rev Infect Dis. 1983; 5: 35-53Crossref PubMed Scopus (581) Google Scholar, 13Weinstein MP Towns ML Quartey SM et al.The clinical significance of positive blood cultures in the 1990s: a prospective comprehensive evaluation of the microbiology, epidemiology, and outcome of bacteremia and fugemia in adults.Clin Infect Dis. 1997; 24: 584-602Crossref PubMed Scopus (961) Google Scholar]. Once these categories have been attributed, the overall number of compliant blood-culture sets containing one or more microorganisms causing sepsis and the number of sets contaminated should be calculated. The result section or tables should contain the numbers of pathogens isolated from both systems, or from either system only. Based on such results, most studies apply the McNemar exact test for statistical analysis [14McNemar Q Psychological statistics. 3rd edn. John Wiley & Sons, Inc., New York1962: 209-239Google Scholar]. It is useful to know the same distribution for contaminants per system. Several recent studies [15Weinstein MP Mirrett S Reimer LG et al.Controlled evaluation of BacT/alert standard aerobic and FAN aerobic blood culture bottles for the detection of bacteremia and fungemia.J Clin Microbiol. 1995; 33: 978-981PubMed Google Scholar, 16Wilson ML Weinstein MP Mirrett S et al.Controlled evaluation of BacT/alert standard anaerobic and FAN anaerobic blood culture bottles for the detection of bacteremia and fungemia.J Clin Microbiol. 1995; 33: 2265-2270PubMed Google Scholar, 17Rohner P Pepey B Auckenthaler R Comparison of BacT/Alert with Signal blood culture system.J Clin Microbiol. 1995; 33: 313-317PubMed Google Scholar, 18Rohner P Pepey B Auckenthaler R Comparative evaluation of BACTEC aerobic Plus/F and Septi-Chek Release blood culture media.J Clin Microbiol. 1996; 34: 126-129PubMed Google Scholar, 19Kirkley BA Easley KA Washington JA Controlled clinical evaluation of Isolator and ESP aerobic blood culture systems for detection of bloodstream infections.J Clin Microbiol. 1994; 32: 1547-1549PubMed Google Scholar, 20Pohlman JK Kirkley BA Easley KA Washington JA Controlled clinical comparison of Isolator and BACTEC 9240 Aerobic/F resin bottle for detection of bloodstream infections.J Clin Microbiol. 1995; 33: 2525-2529PubMed Google Scholar, 21Jorgensen JH Mirrett S McDonald LC et al.Controlled clinical laboratory comparison of BACTEC Plus aerobic/F resin medium with BacT/Alert aerobic FAN medium for detection of bacteremia and fungemia.J Clin Microbiol. 1997; 35: 53-58PubMed Google Scholar, 22Rohner P Pepey B Auckenthaler R Advantage of combining resin with lytic BACTEC blood culture media.J Clin Microbiol. 1997; 35: 2634-2638PubMed Google Scholar] have analyzed the performance of different systems per septic episode, which provides more relevant information for individual patient care. In addition, many evaluations separately analyzed the results obtained from patients receiving antimicrobial therapy [11Zaidi AK Mirrett S McDonald JC et al.Controlled comparison of bioMérieux VITAL and BACTEC NR-660 systems for detection of bacteremia and fungemia in pediatric patients.J Clin Microbiol. 1997; 35: 2007-2012PubMed Google Scholar, 15Weinstein MP Mirrett S Reimer LG et al.Controlled evaluation of BacT/alert standard aerobic and FAN aerobic blood culture bottles for the detection of bacteremia and fungemia.J Clin Microbiol. 1995; 33: 978-981PubMed Google Scholar, 16Wilson ML Weinstein MP Mirrett S et al.Controlled evaluation of BacT/alert standard anaerobic and FAN anaerobic blood culture bottles for the detection of bacteremia and fungemia.J Clin Microbiol. 1995; 33: 2265-2270PubMed Google Scholar, 18Rohner P Pepey B Auckenthaler R Comparative evaluation of BACTEC aerobic Plus/F and Septi-Chek Release blood culture media.J Clin Microbiol. 1996; 34: 126-129PubMed Google Scholar, 20Pohlman JK Kirkley BA Easley KA Washington JA Controlled clinical comparison of Isolator and BACTEC 9240 Aerobic/F resin bottle for detection of bloodstream infections.J Clin Microbiol. 1995; 33: 2525-2529PubMed Google Scholar, 22Rohner P Pepey B Auckenthaler R Advantage of combining resin with lytic BACTEC blood culture media.J Clin Microbiol. 1997; 35: 2634-2638PubMed Google Scholar, 23Pohlman JK Kirkley BA Easley KA Basille BA Washington JA Controlled clinical evaluation of BACTEC Plus Aerobic/F and BacT/Alert Aerobic FAN bottles for detection of bloodstream infections.J Clin Microbiol. 1995; 33: 2856-2858PubMed Google Scholar, 24Smith JA Bryce EA Ngui Yen JH Roberts FJ Comparison of BACTEC 9240 and BacT/Alert blood culture systems in an adult hospital.J Clin Microbiol. 1995; 33: 1905-1908PubMed Google Scholar, 25Koontz FP Flint KK Reynolds JK Allen SD Multicenter comparison of the high volume (10 ml) NR BACTEC Plus system and the standard (5 ml) NR BACTEC system.Diagn Microbiol Infect Dis. 1991; 14: 111-118Abstract Full Text PDF PubMed Scopus (26) Google Scholar, 26Lelievre H Giminez M Vandenesch F et al.Multicenter clinical comparison of resin-containing bottles with standard aerobic and anaerobic bottles for culture of microorganisms from blood.Eur J Clin Microbiol Infect Dis. 1997; 16: 669-674Crossref PubMed Scopus (19) Google Scholar, 27Weinstein MP Mirrett S Wilson ML Harrell LJ Stratton CW Reller LB Controlled evaluation of BACTEC Plus 26 and Roche Septi-Chek aerobic blood culture bottles.J Clin Microbiol. 1991; 29: 879-882PubMed Google Scholar, 28Eisenach K Dyke J Boehme M Johnson B Cook MB Pediatric blood culture evaluation of the BACTEC PEDS Plus and the Du Pont Isolator 1.5 systems.Diagn Microbiol Infect Dis. 1992; 15: 225-231Abstract Full Text PDF PubMed Scopus (16) Google Scholar, 29Welby-Sellenriek PL Keller DS Ferrett RJ Storch G Comparison of the BacT/Alert FAN aerobic and the DIFCO ESP 80A aerobic bottles for pediatric blood cultures.J Clin Microbiol. 1997; 35: 1166-1171PubMed Google Scholar, 30Auckenthaler R Rohner P Bernard D et al.Continuous monitoring blood culture systems.in: Program of the 6th European Congress of Clinical Microbiology. European Society of Clinical Microbiology and Infectious Diseases, Paris1993: 36Google Scholar] (Figure 3). Peer-reviewed publications are a considerable aid in choosing a new blood-culture system. Additional seeded blood-culture studies, which may be performed in almost all laboratories, are recommended as an important verification of a new blood-culture system [1Elder BL Hansen SA Kellogg JA Marsik FJ Zabransky RJ McCurdy BW Cumitech 31, Verification and validation of procedures in the clinical microbiology laboratory. American Society for Microbiology, Washington, DC1997Google Scholar]. The time needed for a system to reveal a positive blood culture is an important criterion. However, too many variables of different institutions (such as distance between wards and the laboratory, transport system available, patient population served) limit the value of comparisons of detection times determined at different sites. In addition, investigators use different time intervals to calculate the detection times of blood-culture systems. For the studies conducted in Geneva, the detection time has always been considered as the time interval between the vial inoculation at the patient’s bedside and the detection of a positive blood culture by the technician after a positive Gram stain result during the working hours from 7 a.m. to 7 p.m. Another acceptable detection time standard is the incubation time required to reveal a positive blood culture, without considering the transport time. Conventional broth-based blood-culture methods are technically simple, but labor-intensive, since visual inspection is required. Each bottle should be examined daily for macroscopic signs of microbial growth, such as turbidity of the medium, hemolysis, gas production, or formation of colonies. A great variety of broth blood-culture media are commercially available (Table 4). Furthermore, laboratories can produce their own blood-culture vials, depending on their resources. Generally, blood-culture bottles contain 50–100 mL of broth, which is supplemented with 0.025–0.05% sodium polyanetholsulfonate (SPS). Of two bottles inoculated, one should be transiently vented, to create an aerobic atmosphere in the headspace of the bottle. Microscopic examination or terminal, blind subcultures of visually negative blood culturing is of little value [6Dunne WM Nolte FS Wilson ML Hindler JA Cumitech 1B, Blood cultures III. American Society for Microbiology, Washington, DC1997Google Scholar].Table 4Media and vial characteristics for commercially available blood‐culture systems according to package inserts and references [6Dunne WM Nolte FS Wilson ML Hindler JA Cumitech 1B, Blood cultures III. American Society for Microbiology, Washington, DC1997Google Scholar, 71Reimer LG Wilson ML Weinstein MP Update on detection of bacteremia and fungemia.Clin Microbiol Rev. 1997; 10: 444-465PubMed Google Scholar, 77Wilson ML Weinstein MP Reller LB Automated blood culture systems.Clin Lab Med. 1994; 14: 149-169PubMed Google Scholar]SystemVialBasic mediumBrothc volumec (mL)Inoculumc volumec (mL)Headspacec atmosphere%c SPSc concentrationSpecialc additivesManipulationc beforec incubationHémolineAerobicTSB40<10Air0.025VentingSepti‐ChekTSBTSB708–10CO20.05Mount agar slideBHIBHI708–10CO20.025Mount agar slideReleaseBHI708–10CO20.0250.165% saponinMount agar slideSignalTSB70∼10CO20.03Attach signalIsolator(0.7)6–102.8% saponinCentrifugationBACTECStandard aerobic/FSCD255CO2 in air0.025NoStandard anaerobic/FSCD255CO2 with N20.025NoPlus aerobic/FSCD258–10CO2 in air0.0517% resinsNoPlus anaerobic/FSCD258–10CO2 with N20.0517% resinsNoPeds Plus /FSCD40<4CO2 in air0.0210% resinsNoLytic anaerobic/FSCD408–10CO2 with N20.0350.26% saponinNoMyco/F LyticMB 7H9401–5CO2 in air0.0250.24% saponinNoBacT/AlertAerobicTSB408–10CO2 in air0.035VentingAnaerobicTSB408–10CO2 with N20.035NoPedi‐BacTBHI20<4CO2 in air0.02VentingAerobic FANBHI408–10CO2 in air0.05EcosorbVentingAnaerobic FANBHI408–10CO2 with N20.05EcosorbNoESPESP 80 A aerobicSCP80<10CO2 in air0.006NoESP 80 N anaerobicPP80<10CO2 in N2NoNoEZ DRAW 40 ASCP40<5CO2 in air0.006NoEZ DRAW 40 NPP40<5CO2 in N2NoNoVitalAerobicSCD4010CO2 in air0.025NoAnaerobicSCD4010CO2 with N2NoBHI, brain–heart infusion broth; MB, Middlebrook; PP, proteose peptone broth; SCD, soybean–casein digest broth; SCP, soycasein peptone broth; SPS, sodium polyanetholsulfonate; TSB, tryptic soy broth. Open table in a new tab BHI, brain–heart infusion broth; MB, Middlebrook; PP, proteose peptone broth; SCD, soybean–casein digest broth; SCP, soycasein peptone broth; SPS, sodium polyanetholsulfonate; TSB, tryptic soy broth. Biphasic blood-culture systems consist of a conventional broth medium which can flood, and thus inoculate, a solid agar medium in a closed system, using different devices and techniques. Back in 1947, a biphasic medium was described for convenient detection of Brucella spp. [31Castaneda MR A practical method for routine blood cultures in brucellosis.Proc Soc Exp Biol Med. 1947; 64: 114-115Crossref PubMed Scopus (44) Google Scholar]. Similar to this biphasic Castaneda medium, the Hémoline aerobic vial (BioMérieux, Lyon, France) is commercially available. A rectangular flask allows the agar to remain attached to the side of the bottle. About one-third of the agar surface remains in the 40 mL of broth. The upper two-thirds of the agar is inoculated by simply turning the vial and flooding the surface. Colonies growing on the transparent agar are easily visible. In a smaller study that we conducted at the University Hospital Geneva, the performance of the Hémoline aerobic vial was similar to that of the Signal system [8Rohner P Delaspe O Ruiz I Auckenthaler R Comparison of Roche Septi-Chek, Oxoid Signal and BioMérieux Hémoline blood culture systems [abstract 203/OS11].in: Abstracts of the 4th European Congress of Clinical Microbiology. European Society of Clinical Microbiology and Infectious Diseases, Paris1989: 103Google Scholar] (Oxoid Ltd, Basingstoke, UK), but it was inferior to that of the Septi-Chek BHI medium (P= 0.009) [8Rohner P Delaspe O Ruiz I Auckenthaler R Comparison of Roche Septi-Chek, Oxoid Signal and BioMérieux Hémoline blood culture systems [abstract 203/OS11].in: Abstracts of the 4th European Congress of Clinical Microbiology. European Society of Clinical Microbiology and Infectious Diseases, Paris1989: 103Google Scholar] or the Septi-Chek Release medium (P<0.0001) in another study [32Etienne J Grando J Celard M Brun Y Fleurette J Evaluation of a blood culture medium BHI-S-Lysis for BCB Release system Roche.Pathol Biol. 1992; 40: 218-222PubMed Google Scholar], as illustrated in Table 1. Mainly staphylococci and members of the Enterobacteriaceae were recovered more often with the Septi-Chek media. In a further study, the Hémoline recovered less pathogens (P=0.04) than the aerobic medium of the automated Vital system [33Avril JL Mathieu D Saulnier C Hignard M Clinical evaluation of the Vital system compared with the Hemoline diphasic method for the detection of aerobic blood cultures.Ann Biol Clin. 1995; 53: 21-24PubMed Google Scholar]. This biphasic blood