Therapy For Bloodstream Infections Research Articles

Point-of-Care Method T2Bacteria®Panel Enables a More Sensitive and Rapid Diagnosis of Bacterial Blood Stream Infections and a Shorter Time until Targeted Therapy than Blood Culture.

Rapid diagnosis and identification of pathogens are pivotal for appropriate therapy of blood stream infections. The T2Bacteria®Panel, a culture-independent assay for the detection of Escherichia coli, Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa in blood, was evaluated under real-world conditions as a point-of-care method including patients admitted to the internal medicine ward due to suspected blood stream infection. Patients were assigned to two groups (standard of care-SOC vs. T2). In the SOC group 2 × 2 blood culture samples were collected, in the T2 group the T2Bacteria®Panel was performed additionally for pathogen identification. A total of 94 patients were included. Pathogens were detected in 19 of 50 patients (38%) in the T2 group compared to 16 of 44 patients (36.4%) in the SOC group. The median time until pathogen detection was significantly shorter in the T2 group (4.5 h vs. 60 h, p < 0.001), as well as the time until targeted therapy (antibiotic with the narrowest spectrum and maximal effectiveness) (6.4 h vs. 42.2 h, p = 0.043). The implementation of the T2Bacteria®Panel for patients with sepsis leads to an earlier targeted antimicrobial therapy resulting in earlier sufficient treatment and decreased excessive usage of broad-spectrum antimicrobials.

Days of Antibiotic Spectrum Coverage Trends and Assessment in Patients with Bloodstream Infections: A Japanese University Hospital Pilot Study.

The antibiotic spectrum is not reflected in conventional antimicrobial metrics. Days of antibiotic spectrum coverage (DASC) is a novel quantitative metric for antimicrobial consumption developed with consideration of the antibiotic spectrum. However, there were no data regarding disease and pathogen-specific DASC. Thus, this study aimed to evaluate the DASC trend in patients with bloodstream infections (BSIs). DASC and days of therapy (DOT) of in-patients with positive blood culture results during a 2-year interval were evaluated. Data were aggregated to calculate the DASC, DOT, and DASC/DOT per patient stratified by pathogens. During the 2-year study period, 1443 positive blood culture cases were identified, including 265 suspected cases of contamination. The overall DASC, DASC/patient, DOT, DOT/patient, and DASC/DOT metrics were 226,626; 157.1; 28,778; 19.9; and 7.9, respectively. A strong correlation was observed between DASC and DOT, as well as DASC/patient and DOT/patient. Conversely, DASC/DOT had no correlation with other metrics. The combination of DASC and DOT would be a useful benchmark for the overuse and misuse evaluation of antimicrobial therapy in BSIs. Notably, DASC/DOT would be a robust metric to evaluate the antibiotic spectrum that was selected for patients with BSIs.

654. Performance of the T2Resistance Panel in Detecting Antibiotic Resistant Bacteria Directly in Whole Blood, and Implications for Improving Appropriate Therapy of Bloodstream Infections

BackgroundAppropriate antibiotic (Ab) therapy of bloodstream infections (BSI) is often delayed by time to blood culture (BC) positivity, species (sp) identification and Ab sensitivity (sensi). The T2Resistance (T2R) Panel is a direct-from-blood (culture-independent) diagnostic that detects 13 genetic markers associated with methicillin-resistant S. aureus (MRSA), vancomycin-resistant Enterococcus (VRE), ESBL- and carbapenemase-producing Enterobacteriaceae (E). We assessed T2R performance in detecting these resistant bacteria in whole blood (WB) and analyzed possible impact on time to appropriate Ab. MethodsWe performed T2R using WB samples obtained from patients (pts) on the same day as BCs from July 2019-2020. Receipt of appropriate Ab was assessed at time of empiric, Gram stain-directed, MALDI-directed (sp identification) and sensi-directed therapy. T2R results were not available to care teams. Teams were notified of positive BCs. Stewardship optimized Abs based on sensi. ResultsBC from 103 pts grew 114 bacterial sp: E (n=54; 16 ESBL-, 1 KPC-producer), S. aureus (n=29, 22 MRSA), Enterococcus (n=21, 16 VRE), P. aeruginosa and others (n=10). 12 ESBL-E produced CTX-M 14/15. T2R sensitivity and specificity was 78% and 99%, respectively, compared to sequencing of resistance markers. Sensitivity was excellent for vanA/B, KPC (100% each), and CTX-M14/15 (92%); sensitivity was 58% for mecA/C. T2R detected resistance determinants in 3-7h. Median time to appropriate Ab was 16.3h, which was significantly longer for VRE (25.6h) and ESBL- or KPC-E (50.9h) BSIs than for T2R marker-negative bacteria (6.7h; p=0.04). Pts with VRE or ESBL-/KPC-E BSI were less likely to received appropriate empiric Ab (18% and 30%, respectively) than pts with T2R marker-negative BSI (63%; p=0.02; Fig.1). Median times to achieve ≥80% appropriate Ab therapy of marker-negative, VRE and CTX-M/KPC-E BSIs were 15.5h (after Gram stain), 43.9h (after MALDI) and 63.5h (after sensi), respectively.Antibiotic Therapy ConclusionThere was a significant delay in appropriate Ab therapy of BSIs, especially in pts infected with VRE and ESBL/KPC-E. T2R rapidly and accurately detected BSI caused by VRE and ESBL/KPC-E, and has the potential to significantly shorten time to appropriate Ab.Disclosures Cornelius J. Clancy, MD, Merck (Grant/Research Support) Ryan K. Shields, PharmD, MS, Shionogi (Consultant, Research Grant or Support) Minh-Hong Nguyen, MD, Merck (Grant/Research Support)

МИКРОБИОЛОГИЧЕСКАЯ ЭФФЕКТИВНОСТЬ КОМБИНАЦИЙ АНТИБИОТИКОВ В ОТНОШЕНИИ ИНВАЗИВНЫХ ШТАММОВ KLEBSIELLA PNEUMONIAE

Background. Combined antibiotic therapy is the main treatment for infections caused by antibiotic-resistant bacteria. The aim of this research was to identify the synergistic activity of antibiotic combinations against invasive extensively drug-resistant K. pneumoniae strains producing carbapenemases. Material and methods. For 12 invasive KPC-, OXA-48- and NDM-producing K. pneumoniae strains, the minimum inhibiting concentrations of antibiotics were determined. The susceptibility to antibiotic combinations was determined using the modified disk diffusion method. Results. The effect of potentiating the activity of colistin with aztreonam (58.3% of strains), azithromycin (33.3%), clarithromycin (41.7%), rifampicin (33.3%) as well as doxycycline (50%) was noted. High microbiological efficiency of ceftazidime/avibactam against all producers of KPC and OXA-48-carbapenemases was demonstrated. For MBLNDM-producing strains, a synergistic effect of the combination of ceftazidime/avibactam and aztreonam with restoration of susceptibility was revealed. Conclusion. The obtained findings open up perspectives for combination therapy of bloodstream infections caused by XDR-strains of K. pneumoniae.

Sepsis—A Retrospective Cohort Study of Bloodstream Infections

Bloodstream infections (BSIs) are among the leading causes of morbidity and mortality worldwide, among infectious diseases. Local knowledge of the main bacteria involved in BSIs and their associated antibiotic susceptibility patterns is essential to rationalize the empiric antimicrobial therapy. The aim of this study was to define the incidence of infection and evaluate the antimicrobial resistance profile of the main pathogens involved in BSIs. This study enrolled patients of all ages and both sexes admitted to the University Hospital “San Giovanni di Dio e Ruggi d’Aragona”, Salerno, Italy between January 2015 to December 2019. Bacterial identification and antibiotic susceptibility testing were performed with Vitek 2. A number of 3.949 positive blood cultures were included out of 24,694 total blood cultures from 2015 to 2019. Coagulase-negative staphylococci (CoNS) were identified as the main bacteria that caused BSI (17.4%), followed by Staphylococcus aureus (12.3%), Escherichia coli (10.9%), and Klebsiella pneumoniae (9.4%). Gram-positive bacteria were highly resistant to Penicillin G and Oxacillin, while Gram-negative strains to Ciprofloxacin, Cefotaxime, Ceftazidime, and Amoxicillin-clavulanate. High susceptibility to Vancomycin, Linezolid, and Daptomycin was observed among Gram-positive strains. Fosfomycin showed the best performance to treatment Gram-negative BSIs. Our study found an increase in resistance to the latest generation of antibiotics over the years. This suggests an urgent need to improve antimicrobial management programs to optimize empirical therapy in BSI.

Evaluation of Microbiological Performance and the Potential Clinical Impact of the ePlex® Blood Culture Identification Panels for the Rapid Diagnosis of Bacteremia and Fungemia.

Molecular rapid diagnostic assays associated with antimicrobial stewardship have proven effective for the early adaptation of empiric therapy in bloodstream infections. The ePlex® BCID (GenMark Diagnostics) Panels allow identification of 56 bacteria and fungi and 10 resistance genes in 90 min directly from positive blood cultures. We prospectively evaluated 187 sepsis episodes at Grenoble University Hospital and retrospectively analyzed the cases to measure the potential clinical impact of the ePlex BCID results. Identification of all pathogens was obtained for 164/187 (88%) bloodstream infections with 100% detection of antimicrobial resistance genes (17 blaCTX-M, 1 vanA, and 17 mecA genes). Only 15/209 (7%) strains were not covered by the panels. Sensitivity for detection of micro-organisms targeted by the RUO BCID-GP, BCID-GN, and BCID-FP Panels was respectively 84/84 (100%), 103/107 (96%), and 14/14 (100%). Interestingly, accurate identification of all pathogens was achieved in 15/17 (88%) polymicrobial samples. Retrospective analysis of medical records showed that a modification of antimicrobial treatment would have been done in 45% of the patients. Treatment modifications would have been an optimization of empiric therapy, a de-escalation or an escalation in respectively 16, 17, and 11% of the patients. Moreover, 11% of the samples were classified as contaminants or not clinically relevant and would have led to early de-escalation or withdrawal of any antibiotic. Detection of resistance genes in addition to identification alone increased escalation rate from 4 to 11% of the patients. Absence of the ePlex result was considered a lost opportunity for therapy modification in 28% of patients.

2171. Phenotypic Correlations for the Presence of CTX-M in Enterobacteriaceae and mecA in Staphylococcus aureus using the Verigene® Blood Culture System

BackgroundRapid identification of antimicrobial resistance markers has the potential to help targeting antimicrobial therapy and enhance efforts for antibiotic stewardship. However, limited data are available to correlate phenotypic and genotypic results for some of these platforms in positive blood cultures (BC). Here, we aimed to evaluate the ability of the Verigene® (VG) Blood Culture System to predict phenotypic susceptibility patterns with the detection of the genes encoding the CTX-M in Enterobacteriaceae and MecA in S. aureus (SA) in a large dataset.MethodsPhenotypic susceptibility and VG results were retrospectively collected between August 2017 and December 2018 from 12 hospitals in Houston, TX. VG testing was performed on only the first isolate was considered in persistent positive BCs. The VG report of the presence of blaCTX-M or mecA was correlated with phenotypic susceptibility to ceftriaxone (CTO) (E. coli [EC] and Klebsiella spp.[KL]) or oxacillin (SA), respectively.ResultsWe identified a total of 5,937 VG results. The final analysis was performed on 2,356 cases where EC, KL or SA was identified. Isolates detected KPC and NDM by VG were excluded. 30 EC/KL were missed by VG in polymicrobial bacteremia. 7 polymicrobial positive BCs with coagulase-negative staphyloccocci were mislabeled as MecA positive MSSA. Among isolated detected by VG, there were the high sensitivity and specificity of CTX-M to identify CTO resistance (97.2% and 99.7% in EC and 91.4% and 99.2% in KL). For SA, the sensitivity and specificity of mecA were 100% and 99.6% to identify oxacillin resistance. 2 isolates with mecA positive by VG were reported as oxacillin-suscpetible.ConclusionOur results revealed that there is a high correlation between VG and phenotype. For SA, discrepancies between genotype and phenotype seem to be influenced by the presence of other organisms in the sample. Genotypic information seems reliable and should guide targeted therapy in bloodstream infections. Disclosures All authors: No reported disclosures.

Identification and antimicrobial susceptibility testing of Gram-positive and Gram-negative bacteria from positive blood cultures using the Accelerate Pheno\u2122 system

Rapid identification and antimicrobial susceptibility testing remain a crucial step for early efficient therapy of bloodstream infections. Traditional methods require turnaround times of at least 2 days, while rapid procedures are often associated with extended hands-on time. The Accelerate Pheno™ System provides microbial identification results within 90 min and susceptibility data in approximately 7 h directly from positive blood cultures with only few minutes of hands-on time. The aim of this study was, therefore, to evaluate the performance of the Accelerate Pheno™ System in identification and antimicrobial susceptibility testing of both Gram-positive and Gram-negative bacteria directly from clinical blood culture samples. We analyzed 108 and 67 blood culture bottles using the Accelerate PhenoTest™ BC kit with software version v1.0 and the FDA-cleared version v1.2, respectively. Reliable identification was achieved for Enterobacteriaceae, staphylococci, and enterococci, with 76/80 (95%), 42/46 (91%), and 10/11 (91%) correct identifications. Limitations were observed in the identification of streptococci, including Streptococcus pneumoniae and Streptococcus pyogenes, and coagulase-negative staphylococci. Antimicrobial susceptibility results for Enterobacteriaceae, for amikacin, ertapenem, ciprofloxacin, gentamicin, meropenem, and piperacillin-tazobactam ranged between 86 and 100% categorical agreement. Using v1.2, results for ceftazidime showed 100% concordance with the reference method. For staphylococci, the overall performance reached 92% using v1.2. Qualitative tests for detection of methicillin or macrolide-lincosamide-streptogramin B (MLSB) resistance caused major and very major errors for isolates. Overall, the present data show that the Accelerate Pheno™ system can, in combination with Gram stain, be used as a rapid complementation to standard microbial diagnosis of bloodstream infections.

Impact of inappropriate empiric antimicrobial therapy on mortality in pediatric patients with bloodstream infection: a retrospective observational study

Inappropriate empiric antibiotic therapy for bloodstream infection could be associated with mortality in adults. However, data for pediatric patients have been scarce. The purpose of this study was to investigate the impact of an inappropriate empiric antibiotic therapy on mortality in pediatric patients with bloodstream infection. We retrospectively analyzed the data of pediatric patients with consecutive positive blood culture in the university hospital between 2007 and 2016. The association between the use of inappropriate empiric therapy and mortality was investigated. A total of 247 bacteremia events in 223 pediatric patients were analyzed. Overall, 208 (84%) events were hospital acquired and 16 (6%) patients died within 28 days. The most frequent causative microorganisms were Gram-positive bacteria (150 events, 61%), followed by Gram-negative bacteria (90 events, 36%) and Candida spp. (7 events, 3%). Inappropriate empiric antibiotic therapy was prescribed within 48 h in 34 (16%) events. Significantly better 28-day survival rates were obtained in patients that received appropriate empiric antibiotic therapy compared with those who received inappropriate therapy (p = 0.004). Multivariate Cox regression analysis showed that inappropriate empiric antibiotic therapy was an independent prognostic factor of 28-day mortality (hazard ratio, 4.39; 95% confidence interval, 1.48–11.94; p = 0.01), after adjusting for age and McCabe score. Inappropriate empiric antibiotic therapy was associated with poor 28-day mortality in pediatric patients with bloodstream infection. Strategies to increase appropriate selection of empiric antibiotic therapy might be an option for improving survival in pediatric patients with bloodstream infection.

Clinical profile and outcome of antibiotic lock therapy for bloodstream infections in pediatric hematology/oncology patients in a tertiary care hospital, Karachi, Pakistan.

BackgroundIntravascular catheters are susceptible to infections, thus requiring catheter removal and leading to increased morbidity and costs. Antibiotic lock therapy (ALT) is a therapeutic technique that is used to salvage the catheter. The aim of this study was to evaluate the outcome of antibiotic lock therapy in bloodstream infections in pediatric hematology/oncology patients in a tertiary care hospital, Karachi.MethodsA retrospective review was performed from January 2013 to December 2017 of pediatric hematology/oncology patients with bloodstream infections and who received ALT at Aga Khan University Hospital. All cases of polymicrobial infections, catheter removal, or malfunction before the completion of ALT were excluded. Descriptive analysis was carried out using SPSS version 20.ResultsA total of nine hematology/oncology patients were eligible. The catheter was salvaged in 7/9 (77.8%) children, and in 2/9 (22.2%) cases, catheter was removed because of persistent bacteremia. The most common organism isolated was Staphylococcus non-aureus species (33.3%). Relapse with a similar pathogen occurred in 2 (22.2%) patients and 2 (22.2%) of them developed an exit-site infection.ConclusionIn our experience, in almost two thirds of the cases, the catheter was salvaged, but disappointingly, relapses were high when the infection was due to Staphylococcus spp. Although this is a small study, our results show that ALT can be a potential safe adjunctive strategy to treat catheter-related bloodstream infections (CRBSI). However, we need larger prospective studies to test the safety and efficacy of ALT to develop specific ALT recommendations and guidelines particularly in children.

1052. Do Healthcare Providers De-Escalate β-Lactam (BL) Antibiotic Therapy Based on Results of Antibiotic Susceptibility Testing (AST)? Analysis of Bloodstream Infections (BSI) Caused by Escherichia coli and Klebsiella pneumoniae From the Veterans Health Administration (VHA)

BackgroundAchieving appropriate therapy for BSI caused by Gram-negative rods (GNR) is challenging. The availability of AST results allows de-escalation from broad- to narrow-spectrum agents. De-escalation is a goal of antimicrobial stewardship (AS). Through the analysis of inpatient BL antibiotic regimens in a nationwide cohort of patients with Escherichia coli and Klebsiella pneumoniae BSI, we compared the relative spectrum of empiric and definitive treatments to AST results and identified opportunities for de-escalation.MethodsUsing a cohort of patients hospitalized within VHA, we identified patients with a blood culture positive for E. coli or K. pneumoniae between 2006 and 2015. We analyzed the subset of patients receiving inpatient BLs before and after Gram stain (GS) and AST results. BLs were grouped into five tiers of increasing spectrum, both with and without a requirement for anaerobic activity (Figure 1). Tiers of BLs across the treatment periods were summarized and compared with the lowest-spectrum tier with an active agent. Rates of inactive, optimal, and overly broad BL therapy were summarized by organism and treatment period.ResultsOf 36,531 BSI identified, we analyzed a subset of 10,825 (7,100 E. coli, 3,725 K. pneumoniae) that met our inclusion criteria (Figure 2). The use of inactive BL agents decreased across time, falling from 11% in early empiric to 4.5% in definitive treatments. The proportion of patients receiving the narrowest available effective BL therapy (“optimal” therapy) increased from 5% to 8% after GS results and to 14% after AST results (Figure 3). De-escalation to optimal therapy after AST results was observed in only 7% of opportunities. If anaerobic activity was required, a smaller proportion of cases would be considered overtreated in the empiric periods (45–46%), but de-escalation after AST results was observed in only 10% of these cases.ConclusionChanges in BL agents across treatment periods reflect an escalation to active treatment, but the absence of de-escalation after AST results was available. This was true both with and without considering a need for anaerobic activity. Expansion of this analysis to include additional classes such as fluoroquinolones may reveal opportunities for AS and de-escalation to optimal therapy in the treatment of E. coli and K. pneumoniae BSI. Disclosures R. Patel, CD Diagnostics, BioFire, Curetis, Merck, Hutchison Biofilm Medical Solutions, Accelerate Diagnostics, Allergan, and The Medicines Company: Grant Investigator, Research grant – monies paid to Mayo Clinic. Curetis, Specific Technologies, Selux Dx, GenMark Diagnostics, PathoQuest and Genentech: Consultant and Scientific Advisor, Consulting fee – monies paid to Mayo Clinic. ASM and IDSA: Travel reimbursement and editor’s stipends, Travel reimbursement and editor’s stipends. NBME, Up-to-Date and the Infectious Diseases Board Review Course: Varies, Honoraria. Mayo Clinic: Employee, Salary. R. Banerjee, Accelerate Diagnostics, Biomerieux, BioFire: Grant Investigator, Research grant and Research support.

Direct identification from positive blood broth culture by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS)

Bloodstream infections (BSIs) are among the most concerning bacterial infections. They are one of the leading causes of morbidity and mortality, and occur in 30–70% of critical care patients. The prompt identification of the causative microorganism can help choosing the appropriate antimicrobial therapy that will lead to better clinical outcomes. Blood culture is one of the most relevant tests for microbiological diagnosis of bacterial infections. The introduction of the MALDI-TOF microbiological diagnosis significantly decreased the time of identifying microorganisms. However, it depends on the growth on solid culture medium. In this study, 538 bottles of positive blood cultures were evaluated to test the accuracy of an in house modified protocol. The study sample consisted of 198 Gram-negative and 350 Gram-positive bacteria. In all, 460 (83.94%) species were identified based on the direct plate findings. The protocol allowed the identification of 185/198 (93.43%) of the Gram-negative bacteria, including aerobes, anaerobes, and non-fermenters, and 275/350 (78.85%) of the Gram-positive bacteria. The proposed method has the potential to provide accurate results in comparison to the traditional method with the potential to reduce the turnaround time for the results and optimize antimicrobial therapy in BSI.

Optimal Duration of Antimicrobial Therapy for Bloodstream Infections Due to Gram-Negative Bacilli

Optimal Duration of Antimicrobial Therapy for Bloodstream Infections Due to Gram-Negative Bacilli

Early deaths in bloodstream infections: a population-based case series

A notable portion of deaths in bloodstream infections (BSI) have previously been shown to occur within 2 days after taking the first positive blood culture specimen. The aim of this study was to analyse patients’ characteristics and causative pathogens of BSIs, leading to early deaths in order to explore possibilities for prevention. Patients with BSI in Helsinki and Uusimaa region (population = 1.5 million) in 2007 were identified from the National Infectious Disease Register (n = 2181) and their deaths within 2 days after the first positive blood culture from the Population Information System (n = 76). Of the early fatal BSIs, 42 (55%) were community-acquired (CA-BSI) and 34 (45%) healthcare-associated (HA-BSI). Charlson comorbidity index was moderate-to-high (index ≥ 3) in 71% of HA-BSIs and 60% of CA-BSIs. The most common pathogens in CA-BSIs were Streptococcus pneumoniae (29%) and Escherichia coli (24%) and in HA-BSIs Pseudomonas aeruginosa (24%) and Staphylococcus aureus (18%). The respiratory tract (50%) was the most common focus of infection. Empiric antimicrobial treatment was more often appropriate in CA-BSIs vs HA-BSIs (81% vs 41%, p < 0.001), but treatment delays were longer in CA-BSIs. The majority of the BSI patients who died early had severe comorbidities. S. pneumoniae accounted for one third of CA-BSIs, highlighting the potential role of pneumococcal vaccines in prevention. Early recognition of BSI and its origin (CA-BSI vs HA-BSI) is crucial. Continuous surveillance data on causative microbes and resistance trends in hospitals is needed to propose guidelines for empiric antimicrobial therapy of BSIs.

Impact of same-day antibiotic susceptibility testing on time to appropriate antibiotic treatment of patients with bacteraemia: a randomised controlled trial.

Inadequate therapy in bloodstream infections is suggested to be associated with higher mortality. We evaluated the reduction in inappropriate antibiotic therapy using rapid identification and antibiotic susceptibility testing (FAST) compared to standard of care (SOC) testing in patients with bloodstream infections. The FAST method used polymerase chain reaction (PCR) for identification and to detect growth in the presence or absence of antibiotics after only 6 h. For SOC testing, the BD Phoenix system was used. Patients with blood cultures growing Staphylococcus, Streptococcus or Enterococcus species or Gram-negative rods were randomised for FAST or SOC tests. A total of 129 patients were randomised for FAST and 121 patients for the SOC group. At the time SOC results became available, 78 patients in the FAST group could have been switched to more appropriate therapy. Although FAST results were highly accurate (agreement with SOC was 94%), they were only implemented in a minority (16) of patients. However, significantly fewer patients in the FAST group used inappropriate therapy at the time of SOC results (p = 0.025). The time to results in the FAST group was reduced by 15.6 h (p < 0.001). In the patients switched after FAST, this was done after a mean of 42.3 h compared to 61.4 h in those switched after SOC tests (p < 0.001). In bacteraemic patients, FAST resulted in significantly more patients using appropriate antibiotic therapy at the time SOC results were available and 15.6 h earlier than SOC tests. However, the implementation of FAST results was not optimal and no benefit on clinical outcome was shown.

Comparison of the Staphylococcus QuickFISH BC Test with the Tube Coagulase Test Performed on Positive Blood Cultures for Evaluation and Application in a Clinical Routine Setting

Many studies demonstrate that delayed proper therapy in bloodstream infections caused by Staphylococcus aureus increases the mortality rate, emphasizing the need to shorten the turnaround time for positive blood cultures. Different techniques are currently available, from phenotypic methods to more complex tests such as matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF), real-time PCR (RT-PCR), and fluorescence in situ hybridization using peptide nucleic acid probes (PNA FISH). This study evaluated the performance of the Staphylococcus QuickFISH BC test (QFT), a novel FISH methodology, compared with the direct tube coagulase test (DTCT) on blood cultures exhibiting Gram-positive cocci in clusters. A total of 173 blood cultures collected from 128 different patients were analyzed using the DTCT, evaluated after both 4 and 24 h, and the QFT. A total of 179 isolates were identified using the Vitek2 system. Thirty-five out of 35 Staphylococcus aureus were correctly identified by the QFT (sensitivity = 100%), with a specificity of 100% (no green fluorescence was detected for strains different from S. aureus). The DTCT was positive after 4 h for 28 out of the 35 samples (sensitivity = 80%) and after 24 h for 31 out of the 35 samples (sensitivity = 88.57%). Among the remaining 144 isolates, one was then identified as Corynebacterium striatum and two as Micrococcus luteus. QFT identified 139 out of the 141 coagulase-negative staphylococci (CoNS) (sensitivity = 98.58%), showing again a specificity of 100% (no fluorescent red signals were detected for strains different from CoNS). We also discuss also the implementation process of this methodology in our setting, with particular emphasis on the workflow and the cost-effectiveness.

Bloodstream Infections Caused by Extended-Spectrum-β-Lactamase- Producing Escherichia coli : Risk Factors for Inadequate Initial Antimicrobial Therapy

Extended-spectrum-beta-lactamase (ESBL)-producing strains of Escherichia coli are a significant cause of bloodstream infections (BSI) in hospitalized and nonhospitalized patients. We previously showed that delaying effective antimicrobial therapy in BSI caused by ESBL producers significantly increases mortality. The aim of this retrospective 7-year analysis was to identify risk factors for inadequate initial antimicrobial therapy (IIAT) (i.e., empirical treatment based on a drug to which the isolate had displayed in vitro resistance) for inpatients with BSI caused by ESBL-producing E. coli. Of the 129 patients considered, 56 (43.4%) received IIAT for 48 to 120 h (mean, 72 h). Independent risk factors for IIAT include an unknown BSI source (odds ratios [OR], 4.86; 95% confidence interval [CI], 1.98 to 11.91; P = 0.001), isolate coresistance to >or=3 antimicrobials (OR, 3.73; 95% CI, 1.58 to 8.83; P = 0.003), hospitalization during the 12 months preceding BSI onset (OR, 3.33; 95% CI, 1.42 to 7.79; P = 0.005), and antimicrobial therapy during the 3 months preceding BSI onset (OR, 2.65; 95% CI, 1.11 to 6.29; P = 0.02). IIAT was the strongest risk factor for 21-day mortality and significantly increased the length of hospitalization after BSI onset. Our results underscore the need for a systematic approach to the management of patients with serious infections by ESBL-producing E. coli. Such an approach should be based on sound, updated knowledge of local infectious-disease epidemiology, detailed analysis of the patient's history with emphasis on recent contact with the health care system, and aggressive attempts to identify the infectious focus that has given rise to the BSI.