Rapid Detection of Carbapenemase and Extended-Spectrum ß-Lactamase Producing Gram-Negative Bacteria Directly from Positive Blood Cultures Using a Novel Protocol.

BACKGROUND: Early and adequate antibiotic treatment is the cornerstone of improving clinical outcomes in patients with bloodstream infections (BSI). Delays in appropriate antimicrobial therapy have catastrophic consequences for patients with BSI. Microbiological characterization of multi-drug resistant pathogens (MDRP) allows clinicians to provide appropriate treatments. Current microbiologic techniques may take up to 96 h to identify causative pathogens and their resistant patterns. Therefore, there is an important need to develop rapid diagnostic strategies for MDRP. We tested a modified protocol to detect carbapenemase and extended-spectrum ß-lactamase (ESBL) producing Gram-negative bacteria (GNB) from positive blood cultures. METHODS: This is a prospective cohort study of consecutive patients with bacteremia. We developed a modified protocol using the HB&L® system to detect MDRP. The operational characteristics were analyzed for each test (HB&L-ESBL/AmpC® and HB&L-Carbapenemase® kits). The kappa coefficient, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), likelihood ratios (LR) with 95% confidence intervals (CI), and reduction in identification time of this novel method were calculated. RESULTS: Ninety-six patients with BSI were included in the study. A total of 161 positive blood cultures were analyzed. Escherichia coli (50%, 81/161) was the most frequently identified pathogen, followed by Klebsiella pneumoniae (15%, 24/161) and Pseudomonas aeruginosa (8%, 13/161). Thirty-three percent of isolations had usual resistance patterns. However, 34/161 (21%) of identified pathogens were producers of carbapenemases and 21/161 (13%) of extended-spectrum ß-lactamases. Concordance between our HB&L® modified protocol and the traditional method was 99% (159/161). Finally, identification times were significantly shorter using our HB&L®-modified protocol than traditional methods: median (IQR) 19 h (18, 22) vs. 61 h (60, 64), p < 0.001. CONCLUSIONS: Here, we provide novel evidence that using our HB&L®-modified protocol is an effective strategy to reduce the time to detect MDRP producers of carbapenemases or extended-spectrum ß-lactamases, with an excellent concordance rate when compared to the gold standard. Further studies are needed to confirm these findings and to determine whether this method may improve clinical outcomes.

Cerebral phaeohyphomycosis caused by Alternaria spp.: A case report.

Phaeohyphomycosis is a group of infections caused by pigmented, black, dematiaceous fungi and is responsible for cutaneous, superficial and deep mycoses, disseminated infection and brain abscesses. The primary agents involved include Alternaria spp., Exophiala spp. and Cladophialophora spp. Invasive systemic presentation is rare and in most cases is associated with immunosuppression; for this reason, reported cases of Alternaria spp. infection are scarce. This report describes the case of a 66-year-old man with a history of renal transplantation from a cadaveric donor 1 year ago, which was considered as the primary risk factor. The characteristics of the infection, procedures performed, microbiological findings and treatment provided are described.