Value of rapid antigen detection tests (RADTs) for diagnosis of invasive group A Streptococci (GAS)

• 3-centre, retrospective study: N=192 miscellaneous clinical samples (pleural and synovial fluids, subcutaneous, gynaecological/digestive abscesses,...):

– GAS+ (by culture and/or 16S rRNA PCR): N=75

– GAS-: N=117• Compare diagnostic value of 3 RADTs with GAS culture and with the ‘gold

standard’ GAS-specific real-time PCR (targeting ntpB gene encoding putative V-type Na+ATPase subunit B)

Gazzano V. ECCMID 2014 abs. P0623

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Data from poster

Value of rapid antigen detection tests (RADTs) for diagnosis of invasive group A Streptococci (GAS)

The 3 RADTs showed a higher sensitivity than GAS culture, but were less sensitive than GAS-specific PCR. They may be used to speed

up diagnosis when invasive GAS infections are suspected

Gazzano V. ECCMID 2014 abs. P0623

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Data from poster

Unique blood culture (UBC) vs multiple blood culture (MBC): diagnostic performance

• 1-yr, multi-centre, prospective study (France): N=826 pts ≥18 yr admitted to adult ICU with fever ≥38.5°C, hypothermia ≤36.0°C, chills or shock

• N=300 pts with positive BC (mean age: 67.3 yr): Pathogens: N=245 / Contaminants: N=55

Dargere S. ECCMID 2014 abs. P0484

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Data from poster

Unique blood culture (UBC) vs multiple blood culture (MBC): diagnostic performance

UBC may decrease the # of false positives and false negatives compared with MBC and may lead to significant cost savings

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Data from poster

Dargere S. ECCMID 2014 abs. P0484

• Discrepancies:

• MBC vs UBC (1 centre): cost savings: 193,275 €/yr (materials, labour time)

Unique blood culture (UBC) vs multiple blood culture (MBC): diagnostic performance

• MBC vs UBC (1 centre): cost savings: 193,275 €/yr (materials, labour time)

UBC may decrease the # of false positives and false negatives compared with MBC and may lead to significant cost savings

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Data from poster

Dargere S. ECCMID 2014 abs. P0484

MALDI-TOF for pathogen identification in blood cultures (BCs): improved methods

Short-incubation (SI) MALDI-TOF for rapid pathogen identification1:

3-centre study (Finland):

•50-100 ml blood from pos. BC bottle aspirated onto blood, chocolate and FAA agar plates → incubation 3-4h 37°C CO2 atmosphere

•Sample from application area of each plate spread on a MALDI-TOF target plate, even if no visible growth + 1 µl matrix suspension added + air drying → samples analysed in MALDI-TOF instruments

•Comparison with conventional MALDI-TOF or other identification methods

1Kalanti A. ECCMID 2014 abs. P04952Østergaard C. ECCMID 2014 abs. P0494

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Data from poster

MALDI-TOF for pathogen identification in blood cultures (BCs): improved methods

MALDI-TOF-MS directly on positive BCs2:

Single-centre study (2013-2014; Denmark): N=1,068 unique isolates

•2 ml blood from pos. BC bottle centrifuged (1,000g; 2 min) to remove RBCs → supernatant centrifuged (14,000g; 10 min) → bacteria in pellet

•Sample from pellet transferred to MALDI-TOF target plate, without protein extraction + standard matrix added → analysed in MALDI-TOF instrument

•Comparison with conventional MALDI-TOF (samples cultured on 5% Danish blood or anaerobic agar plates) (cut-off score: 1.7)

Short-incubation MALDI-TOF or MALDI-TOF directly on pos. BC bottles may simplify and fasten pathogen identification in BCs

1Kalanti A. ECCMID 2014 abs. P04952Østergaard C. ECCMID 2014 abs. P0494

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Data from poster

MALDI-TOF + antimicrobial stewardship team (AST) intervention: impact on outcomes in pts with bloodstream infections (BSIs)

• Single-centre before-after study (USA): N=501 adult pts with BSI

– Pre-intervention phase (Sep-Nov 2011): BSI identified by conventional methods

– Intervention phase (Sep-Nov 2012): BSI identified via MALDI-TOF + real-time evidence-based antibiotic recommendations by AST

Huang AM et al. Clin Infect Dis 2013;57:1237-45

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• Multivariate analysis for predictors of mortality: Acceptance of AST intervention: trend towards reduced mortality: OR=0.55; 95% CI:0.28-1.06; P=0.075

MALDI-TOF + antimicrobial stewardship team (AST) intervention: impact on outcomes in pts with bloodstream infections (BSIs)

MALDI-TOF + AST intervention may decrease time to organism identification and time to effective and optimal antibiotic therapy

Huang AM et al. Clin Infect Dis 2013;57:1237-45

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1,3-β-D-glucan (BG) antigenaemia: accuracy for diagnosing intraabdominal candidiasis (IAC)

• Fungal Infection Network of Switzerland (FUNGINOS): 2-centre, prospective, observational cohort study (2007-2010): median FU: 19 days

• N=89 adult ICU pts (≥72h in ICU) with recurrent GI tract perforation (N=68) or acute necrotising pancreatitis (N=21); 920 sera analysed (9 sera/patient)

Tissot F et al. Am J Respir Crit Care Med 2013;188:1100-9

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• Mortality/sepsis rate among pts with documented IAC (N=29):

• Time between microbiological diagnosis of IAC (day 0) and time of reaching value above the cut-off value (per diagnostic method):

1,3-β-D-glucan (BG) antigenaemia: accuracy for diagnosing intraabdominal candidiasis (IAC)

Tissot F et al. Am J Respir Crit Care Med 2013;188:1100-9

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Accuracy (N=29 pts with documented IAC; maximum value up to time of IAC diagnosis compared with day 7 after inclusion in pts without IAC)

1,3-β-D-glucan (BG) antigenaemia: accuracy for diagnosing intraabdominal candidiasis (IAC)

In high-risk surgical ICU pts, BG antigenaemia was more accurate than CS and (C)CI and anticipated diagnosis of blood culture-neg. IAC

Tissot F et al. Am J Respir Crit Care Med 2013;188:1100-9

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*Accuracy=(true positives + true negatives)/ all results; †2 consecutive BG measurements; (C)CI: (corrected) Candida colonisation index; CS: Candida score; NPV: neg. predictive value; PPV: pos. predictive value