Evaluation of direct inoculation of the BD PHOENIX system from positive BACTEC blood cultures for both Gram-positive cocci and Gram-negative rods.

BACKGROUND: Rapid identification (ID) and antibiotic susceptibility testing (AST) of the causative micro-organism of bloodstream infections result in earlier targeting of antibiotic therapy.In order to obtain results of ID and AST up to 24 hours earlier, we evaluated the accuracy of direct inoculation of the Phoenix system from positive blood cultures (BACTEC) by using Serum Separator Tubes to harvest bacteria from positive blood cultures. Results were compared to those of standard Phoenix procedure. Discrepancies between the two methods were resolved by using the API system, E-test or microbroth dilution. RESULTS: ID with the direct method was correct for 95.2% of all tested Enterobacteriaceae (n = 42) and 71.4% of Pseudomonas aeruginosa strains (n = 7).AST with the direct method showed a categorical agreement for Gram-negative rods (GNR) of 99.0%, with 0.7% minor errors, 0.3% very major errors and no major errors. All antibiotics showed an agreement of >95%.The direct method for AST of Staphylococcus (n = 81) and Enterococcus (n = 3) species showed a categorical agreement of 95.4%, with a minor error rate of 1.1%, a major error rate of 3.1% and a very major error rate of 0.4%. All antibiotics showed an agreement of >90%, except for trimethoprim-sulfamethoxazole and erythromycin. CONCLUSIONS: Inoculation of Phoenix panels directly from positive blood cultures can be used to report reliable results of AST of GNR a day earlier, as well as ID-results of Enterobacteriaceae. For Staphylococcus and Enterococcus species, results of AST can also be reported a day earlier for all antibiotics, except for erythromycin and trimethoprim-sulfamethoxazole.

Molecular probes for diagnosis of clinically relevant bacterial infections in blood cultures.

Broad-range real-time PCR and sequencing of the 16S rRNA gene region is a widely known method for the detection and identification of bacteria in clinical samples. However, because of the need for sequencing, such identification of bacteria is time-consuming. The aim of our study was to develop a more rapid 16S real-time PCR-based identification assay using species- or genus-specific probes. The Gram-negative bacteria were divided into Pseudomonas species, Pseudomonas aeruginosa, Escherichia coli, and other Gram-negative species. Within the Gram-positive species, probes were designed for Staphylococcus species, Staphylococcus aureus, Enterococcus species, Streptococcus species, and Streptococcus pneumoniae. The assay also included a universal probe within the 16S rRNA gene region for the detection of all bacterial DNA. The assay was evaluated with a collection of 248 blood cultures. In this study, the universal probe and the probes targeting Pseudomonas spp., P. aeruginosa, E. coli, Streptococcus spp., S. pneumoniae, Enterococcus spp., and Staphylococcus spp. all had a sensitivity and specificity of 100%. The probe specific for S. aureus showed eight discrepancies, resulting in a sensitivity of 100% and a specificity of 93%. These data showed high agreement between conventional testing and our novel real-time PCR assay. Furthermore, this assay significantly reduced the time needed for identification. In conclusion, using pathogen-specific probes offers a faster alternative for pathogen detection and could improve the diagnosis of bloodstream infections.

[Invasive pulmonary aspergillosis in influenza]. / Invasieve pulmonale aspergillose bij influenza.

BACKGROUND: Invasive pulmonary aspergillosis (IPA) is a life-threatening infection that occurs predominantly in severely immunocompromised patients. Recently, IPA is also increasingly seen in less severely immunocompromised patients, such as patients with COPD receiving glucocorticoids and patients on ventilation in an IC unit. CASE DESCRIPTION: Here we present the case of a 59-year-old male who died of influenza complicated by a superinfection with Aspergillus fumigatus. This patient had no known previous medical history, except schizophrenia. CONCLUSION: Since the 2009 influenza pandemic, IPA has been increasingly reported as a superinfection in patients with a severe influenza virus infection. This combined Aspergillus and influenza infection often has a fatal outcome. An Aspergillus sputum culture should be taken seriously in patients with severe influenza pneumonia, and treatment should be considered early in the disease course.

One-day workflow scheme for bacterial pathogen detection and antimicrobial resistance testing from blood cultures.

Bloodstream infections are associated with high mortality rates because of the probable manifestation of sepsis, severe sepsis and septic shock(1). Therefore, rapid administration of adequate antibiotic therapy is of foremost importance in the treatment of bloodstream infections. The critical element in this process is timing, heavily dependent on the results of bacterial identification and antibiotic susceptibility testing. Both of these parameters are routinely obtained by culture-based testing, which is time-consuming and takes on average 24-48 hours(2, 4). The aim of the study was to develop DNA-based assays for rapid identification of bloodstream infections, as well as rapid antimicrobial susceptibility testing. The first assay is a eubacterial 16S rDNA-based real-time PCR assay complemented with species- or genus-specific probes(5). Using these probes, Gram-negative bacteria including Pseudomonas spp., Pseudomonas aeruginosa and Escherichia coli as well as Gram-positive bacteria including Staphylococcus spp., Staphylococcus aureus, Enterococcus spp., Streptococcus spp., and Streptococcus pneumoniae could be distinguished. Using this multiprobe assay, a first identification of the causative micro-organism was given after 2 h. Secondly, we developed a semi-molecular assay for antibiotic susceptibility testing of S. aureus, Enterococcus spp. and (facultative) aerobe Gram-negative rods(6). This assay was based on a study in which PCR was used to measure the growth of bacteria(7). Bacteria harvested directly from blood cultures are incubated for 6 h with a selection of antibiotics, and following a Sybr Green-based real-time PCR assay determines inhibition of growth. The combination of these two methods could direct the choice of a suitable antibiotic therapy on the same day (Figure 1). In conclusion, molecular analysis of both identification and antibiotic susceptibility offers a faster alternative for pathogen detection and could improve the diagnosis of bloodstream infections.

Antibiotic susceptibility testing of grown blood cultures by combining culture and real-time polymerase chain reaction is rapid and effective.

BACKGROUND: Early administration of appropriate antibiotic therapy in bacteraemia patients dramatically reduces mortality. A new method for RApid Molecular Antibiotic Susceptibility Testing (RAMAST) that can be applied directly to positive blood cultures was developed and evaluated. METHODOLOGY/PRINCIPAL FINDINGS: Growth curves and antibiotic susceptibility of blood culture isolates (Staphylococcus aureus, enterococci and (facultative) aerobic gram-negative rods) were determined by incubating diluted blood cultures with and without antibiotics, followed by a quantitative universal 16S PCR to detect the presence or absence of growth. Testing 114 positive blood cultures, RAMAST showed an agreement with microbroth dilution of 96.7% for gram-negative rods, with a minor error (false-susceptibility with a intermediate resistant strain) rate of 1.9%, a major error (false resistance) rate of 0.8% and a very major error (false susceptibility) rate of 0.6%. Agreement for S. aureus was 97.9%, with a very major error rate of 2.1%. Enterococcus species showed 95.0% agreement, with a major error rate of 5.0%. These agreements are comparable with those of the Phoenix system. Starting from a positive blood culture, the test was completed within 9 hours. CONCLUSIONS/SIGNIFICANCE: This new rapid method for antibiotic susceptibility testing can potentially provide accurate results for most relevant bacteria commonly isolated from positive blood cultures in less time than routine methods.

Soluble Triggering Receptor Expressed on Myeloid cells-1 in bronchoalveolar lavage fluid is not predictive for ventilator-associated pneumonia.

PURPOSE: Soluble Triggering Receptor Expressed on Myeloid cells-1 (sTREM-1) has proven to be a good biomarker for sepsis. For the diagnosis ventilator-associated pneumonia (VAP), however, there have only been a few, relatively small, studies on the role of this receptor. The aim of the study was to evaluate the usefulness of sTREM-1 in bronchoalveolar lavage fluid (BALF) from Intensive Care Unit patients as rapid diagnostic test for VAP. METHODS: The concentration of sTREM-1 in 240 BALF samples was measured using a quantitative sandwich enzyme immunoassay. Two researchers who were blind to the assay results determined whether a VAP was present or not. Clinical suspicion of a VAP was confirmed by the presence of > or = 2% cells containing intracellular organisms and/or a quantitative culture result of > or = 10(4) colony forming units per millilitre BALF. RESULTS: The mean concentration of sTREM-1 was significantly higher in the BALF of patients with confirmed VAP than in that of patients without confirmed VAP. However, the area under the receiver-operating characteristic curve was 0.58 (95% confidence interval 0.50-0.65, P = 0.04). CONCLUSIONS: The results imply that the sTREM-1 assay in BALF may not be discriminative for VAP.