Rapid Identification of Pathogens in Positive Blood Culture of Patients with Sepsis: Review and Meta-Analysis of the Performance of the Sepsityper Kit

Table 1

The 21 published reports on the Sepsityper sample preparation kit. BC: blood culture, ID: identification, cfu: colony forming units, LOD: lower limit of detection, and MALDI-TOF MS: Matrix-Assisted Laser Desorption Ionization Time-of-Flight Mass Spectrometry.

Author	Year	Reference	Blood culture system	Gram neg. bacteria; (% pos. ID)	Gram pos. bacteria; (% pos. ID)	Fungi; (% pos. ID)	Total monomicrobial samples (% pos. ID)	Log(score); cut-off used	Comments
Schubert et al.	2011	[25]	Bactec 924	98; 89.8% species	358; 86.3% species	17; 70.6% species	473; 86.5% species	>1.5 species	ID up to 48 hours earlier compared to conventional methods; In 18 of 27 mixed cultures at least one isolate was identified correctly; Misidentified were 5 Streptococcus mitis as Streptococcus pneumonia
Kok et al.	2011	[56]	Bactec FX; Plus Aerobic/F; Anaerobic/F; Lytic/10	187; 87.2% genus; 79.7% species	285; 68.4% genus; 46.3% species	—	472; 75.8% genus; 59.5% species	>1.7 genus >2.0 species	All genus results would be reported as species results by present day software; Misidentified were 4 Streptococcus mitis as Streptococcus pneumonia, corrected in later databank updates
Yan et al.	2011	[41]	Bactec FX	—	—	42; 100% species	42; 100% species	>1.9 species	LOD of yeast detection from positive BC bottles: 5.9 × 10^5 CFU/ml; Two washing steps added prior to the Sepsityper protocol
Buchan et al.	2012	[34]	Bactec Plus Aerobic/F and; Bactec Lytic/10	45; 97.7% genus; 91.0% species	100; 80.0% genus; 53% species	5; 0% genus	150; 85.5% genus; 64.8% species	>1.7 genus; >2.0 species	ID 24–130 h faster as compared to conventional methods; Log(score) >1.7 was sufficient for ID on species level, since overall concordance to routine ID was 96.6% to genus and 94.1% to species level; Five discrepant results: three Streptococcus oralis had Streptococcus pneumonia ID by MALDI; two were misidentified by conventional methods (16S sequencing confirmed MALDI)
Juiz et al.	2012	[43]	Bactec	24; 95.8% genus; 95.8% species	61; 96.7% genus; 84.7% species	—	85; 96.4% genus; 87.0% species	>1.7 genus; >2.0 species	Sepsityper performed better than an alternative in-house method for sample preparation; No correct ID of one Streptococcus pneumoniae
Klein et al.	2012	[35]	Bactec 9240; Bactec Plus Aerobic/F, Anaerobic/F, and Peds Plus/F	52; 99% species	71; 64% species	—	123; 82.9% species	>1.7 species (if matching organism stated several times in list)	Sepsityper performed better than alternative in-house method with gel separator tubes; ID for Gram negative better than for Gram positive; Misidentification of S. hominis instead of S. epidermidis and S. hominis instead of S. haemolyticus
Lagacé-Wiens et al.	2012	[36]	BacT/Alert SA; BacT/Alert SN	19; 100% species	40; 80% species	2; 50% species	61; 85.2% species; 88.5% if >1.5	>1.7 species; >1.5	Log(score) >1.5 gave 100% concordance to routine ID; Mean turnaround time for conventional ID was 40.9 h compared to 6.6 h for MALDI (if positive ID)
Loonen et al.	2012	[31]	BacT/Alert SA; BacT/Alert SN	47; 95.7% genus; 91.5% species	52; 65.4% genus; 42.3% species	—	99; 79.8% genus; 65.7% species	>1.7 genus; >2.0 species	Sepsityper performed better and was faster than two alternative sample preparation methods. Anaerobe BacT/Alert SN bottles lead to unreliable results, charcoal containing bottles not suitable
Martiny et al.	2012	[38]	Bactec Plus Aerobic; Bactec F Lytic Anaerobic	22; 72.7% genus; 59.1% species	37; 81.1% genus; 74.3% species	—	59; 78.0% genus; 68.4% species	>1.4 genus; >1.6 species (if 0.3 difference to next in list)	Relatively low number of BC tested. Gram positive bacteria resulted in better ID than Gram negative (unusual report, not confirmed by other studies). In direct comparison an in-house method performed better than Sepsityper. Log(score) cutoffs could be lowered to >1.6 for correct species ID, which increased the correct ID for both methods
Meex et al.	2012	[32]	BacT/Alert SN	40; 82.5% species	67; 58.2% species	—	107; 67.3% species	>1.8 species	Correct species ID accepted at any log(score), if first three database matches were identical; No difference between Sepsityper and in-house method using saponin lysis; ID of Salmonella paratyphi B only to genus level; Direct ID faster than conventional method (1–24 h)
Saffert et al.	2012	[37]	Bactec 9240; Bactec Plus Aerobic/F; Anaerobic/F; Peds Plus/F	35; 94% genus; 83% species	64; 80% genus; 70% species	—	99; 85% genus; 75% species	>1.5 genus; >1.7 species	Sepsityper and two in-house methods compared; One Streptococcus viridans was identified as Streptococcus pneumoniae Log(score)s <1.5 in combination with Gram stain results would lead to another 9 correct ID
Chen et al.	2013	[33]	Bactec Plus Aerobic, Bactec F Lytic Anaerobic, and Bactec Myco Lytic	106; 99% genus; 88.7% species	75; 96% genus; 72% species	—	181; 97.8% genus; 81.8% species	>1.6 genus; >2.0 species	Sepsityper used with Biotyper generated significantly more accurate identifications than with Vitek MS; Only genus level ID in both systems for Salmonella spec.; In 21 mixed cultures, correct double ID by Biotyper in 5
Haigh et al.	2013	[28]	BacT/Alert 3D FA, BacT/Alert 3D PF, and BacT/Alert SN	123; 90% species	168; 64% species	6; 0%	297; 74% species	>1.7 species	Most ID failures resulted from BC bottles with charcoal; therefore BacT/Alert bottles with charcoal are not the optimal culture medium in combination with Sepsityper
Jamal et al.	2013	[46]	Bactec 9240 or BacT/Alert	53; 66% species	99; 75,8% species	8; 50% species	160; 75.6% species	>2.0 species	No data on genus identification shown. Definition of positive ID often independent of log(score). The term “misidentified” instead of “unidentified” was used for ID scores <1.5, 10 species not identified by routine method but MALDI
Nonnemann et al.	2013	[40]	Bactec FX	53; 88.7% genus; 81% species	148; 60% genus; 44% species	22; 77% species	223; 64% genus; 56% species	>1.6 genus; >1.8 species	The fungi experiments contained mainly spiked BC samples; A lower cutoff (>1.5 for species ID) was also applied. Combined with Gram staining, a log(score) >1.3 increased Gram positive results to 85% without misidentifications
Tadros and Petrich	2013	[45]	Bactec Aerobic/F, Anaerobic/F, and Peds Plus/F	19; 94.7% genus; 94.7% species	60; 93.3% genus; 66.7% species	1; 100% genus; 100% species	80; 93.8% genus; 78% species	>1.7 genus; >2.0 species	Some Gram positive specimens were excluded from species analysis; Total number of samples contained also 7 cerebrospinal fluids spiked into BC bottles and 10 polymicrobial samples
Gorton et al.	2014	[42]	Bactec	—	—	50; 76% genus; 56% species	50; 76% genus; 56% species	>1.6 genus; >1.8 species	100–200 cfu of yeast was spiked into BC bottles and after positive growth extracted by Sepsityper; A lower log(score) (>1.5) for correct species ID and repeated measurements increased ID on species level to 84%; Gram staining not sufficient for fungal ID!
Hazelton et al.	2014	[44]	Bactec Plus Aerobic/F, Lytic/10, Anaerobic/F, and Peds Plus/F	64; 98.4% species	—	—	64; 98.4% species	>2.0 species	Main focus of the study was the use of the Sepsityper kit for direct antibiotic resistance testing in the BD Phoenix system with 97.9% concordance in susceptibility testing
Martinez et al.	2014	[26]	VersaTREK Redox	46; 86.9% genus; 80.4% species	95; 89.4% genus; 81.0% species	5; 60% genus; 60% species	146; 87.7% genus; 80.1% species	>1.6 genus; >1.8 species	Additional washing step added in protocol; Anaerobic BC cultures excluded by design; Also at least one correct ID in 77% of polymicrobial cultures; Misidentification of 4 Streptococcus viridans specimens as S. pneumoniae
Schieffer et al.	2014	[27]	Bactec Plus Aerobic/F, Standard/10 Aerobic/F, Peds Plus/F, Lytic/10 Anaerobic/F, and VersaTREK Redox	94; 97.8% genus; 95.7% species	225; 95.5% genus; 81.7% species	6; 50% genus; 16% species	325; 94.7% genus; 84.0% species	>1.6 genus; >1.8 species	Sepsityper was used in two hospitals; BC extraction on site; pellet was stored at RT until shipment, MALDI-TOF MS performed off site
Idelevich et al.	2014	[39]	Bactec 9240, Plus Aerobic/F, Plus Anaerobic/F, Mycosis-IC/F, and Peds Plus/F	—	—	24; 62.5% species	24; 62.5% species	>1.5 species; If first two results were identical	Sepsityper protocol was followed without prior washing steps (compare to Yan et al. [41]). Manual shooting and double protein concentration for MALDI were tried out to increase log(score)s >1.7,; Mean yeast for positive ID was 4.5 × 10^7. Results were 23.5 h earlier than standard method; Sepsityper pellets generated antibiotic susceptibility profiles in 72.7% of samples 15 h earlier