Impact of rapid microbial identification directly from positive blood cultures using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry on patient management

Abstract

For septic patients, delaying the initiation of antimicrobial therapy or choosing an inappropriate antibiotic can considerably worsen their prognosis. This study evaluated the impact of rapid microbial identification (RMI) from positive blood cultures on the management of patients with suspected sepsis. During a 6-month period, RMI by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) was performed for all new episodes of bacteraemia. For each patient, the infectious disease specialist was contacted and questioned about his therapeutic decisions made based on the Gram staining and the RMI. This information was collected to evaluate the number of RMIs that led to a therapeutic change or to a modification of the patient's general management (e.g. fast removal of infected catheters). During the study period, 277 new episodes of bacteraemia were recorded. In 71.12% of the cases, MALDI-TOF MS resulted in a successful RMI (197/277). For adult and paediatric patients, 13.38% (21/157) and 2.50% (1/40) of the RMIs, respectively, resulted in modification of the treatment regimen, according to the survey. In many other cases, the MALDI-TOF MS was a helpful tool for infectious disease specialists because it confirmed suspected cases of contamination, especially in the paediatric population (15/40 RMIs, 37.50%), or suggested complementary diagnostic testing. This study emphasizes the benefits of RMI from positive blood cultures. Although the use of this technique represents an extra cost for the laboratory, RMI using MALDI-TOF MS has been implemented in our daily practice.

Instant screening and verification of carbapenemase activity in Bacteroides fragilis in positive blood culture, using matrix-assisted laser desorption ionization–time of flight mass spectrometry

“…Direct ID from positive blood cultures by MALDI-TOF MS is routinely performed at the Department of Clinical Microbiology at Central hospital in Växjö, and the spiked bottles were treated as any other positive blood culture according to the previously described protocol (Martiny et al, 2013). Score values from direct ID of the B. fragilis strains are presented in Tables 1 and 2, and ranged between 1.865 and 2.414.…”

“…Bottles were incubated in a BD BACTEC FX (Becton Dickinson) until positive signalling from the system was obtained. As control, a bottle containing blood without bacteria was used and incubated for 24 h. Direct identification was performed according to the published protocol by Martiny et al (2013) with the modification of adding 1 ml of 70 % formic acid on the spotted target plate before applying 1ml HCCA matrix (2.5 mg a-cyano-4-hydroxycinnamic acid dissolved in 50 % acetonitril, 47.5 % HPLC-pure H 2 O and 2.5 % trifluoroacetic acid; Bruker Daltonics) and left to dry. Identification was performed according to the manufacturer's instructions in the MALDI Biotyper 3.1 software (Bruker Daltonics).…”

“…When treating patients with septic shock, a delay in implementing the appropriate antimicrobial treatment will considerably reduce the average survival of the patient (Kumar et al, 2009). Martiny et al (2013) showed in their study that the introduction of direct identification (direct ID) from blood cultures led to modification of therapy in 13.38 % of adult patients, and in 37.50 % of paediatric patients a suspected contaminant could be confirmed.…”

Sepsis: the LightCycler SeptiFast Test MGRADE®, SepsiTest™ and IRIDICA BAC BSI assay for rapidly identifying bloodstream bacteria and fungi – a systematic review and economic evaluation

“…It is thought that the increasing number of invasive procedures (such as catheterisation), immunosuppressive therapy, antibiotic therapy and life support measures has resulted in an increase in health-care-associated bloodstream infections. 12 In 2011, an estimated 6.4% [95% confidence interval (CI) 4.7% to 8.7%] of patients in acute care hospitals were diagnosed with a health-care-associated infection, with the largest proportion (23.4%) within the ICU. 13 Of patients with a health-care-associated infection, it was estimated that 7.6% had a bloodstream infection.…”

“…The spectrum of pathogens isolated from these people may differ from those associated with health-care-acquired bloodstream infection. 12 Bloodstream infection is also a risk for people who are immunocompromised, particularly among people with neutropenia (abnormally low neutrophil levels in the blood), who are at risk of developing neutropenic sepsis. People who are immunocompromised have a higher incidence of infections caused by pathogens that pose low risk to those whose immune system is not impaired, such as Pseudomonas species, Listeria monocytogenes, Corynebacterium species, Candida species, coagulase-negative staphylococci, enterococci and viridans streptococci.…”