Fatal Nocardia farcinica Bacteremia Diagnosed by Matrix-Assisted Laser Desorption-Ionization Time of Flight Mass Spectrometry in a Patient with Myelodysplastic Syndrome Treated with Corticosteroids

Nocardia farcinica is a Gram-positive weakly acid-fast filamentous saprophytic bacterium, an uncommon cause of human infections, acquired usually through the respiratory tract, often life-threatening, and associated with different clinical presentations. Predisposing conditions for N. farcinica infections include hematologic malignancies, treatment with corticosteroids, and any other condition of immunosuppression. Clinical and microbiological diagnoses of N. farcinica infections are troublesome, and the isolation and identification of the etiologic agent are difficult and time-consuming processes. We describe a case of fatal disseminated infection in a patient with myelodysplastic syndrome, treated with corticosteroids, in which N. farcinica has been isolated from blood culture and identified by Matrix-Assisted Laser Desorption-Ionization Time of Flight Mass Spectrometry. The patient died after 18 days of hospitalization in spite of triple antimicrobial therapy. Nocardia farcinica infection should be suspected in patients with history of malignancy, under corticosteroid therapy, suffering from subacute pulmonary infection,and who do not respondto conventional antimicrobial therapy. Matrix-Assisted Laser Desorption-Ionization Time of Flight Mass Spectrometry can be a valuable tool for rapid diagnosis of nocardiosis

A prediction model for real-time PCR results in blood samples from febrile patients with suspected sepsis

Sepsis, a systemic, deleterious host response to infection that leads to organ dysfunction, is a potentially deadly condition needing prompt identification of the causative organisms and early appropriate antimicrobial therapy. Among non-culture-based diagnostic methods, SeptiFast(SF) can be employed to speed bacterial and fungal DNA detection, but it suffers from poor sensitivity and high cost. The aim of the present study, performed in 285 febrile patients, was to develop a prediction model to restrict the SF assay to clinical cases with a high probability of positive SF results. The prevalence of SF results positive for a pathogen was 17.2 %. Independent predictors of positive results were: blood sampling within 12 h after the onset of fever [odds ratio (OR) 20.03; 95 % confidence interval (CI) 6.87–58.38;P<0.0001]; ≥0.5 ng serum procalcitonin (PCT) ml−1(OR 18.52; 95 % CI 5.12–67.02;P<0.0001); body temperature ≥38 °C (OR 3.78; 95 % CI 1.39–10.25;P = 0.009); ≤3 g serum albumin dl−1(OR 3.40; 95 % CI 1.27–9.08;P = 0.014); and ≥13 000 white blood cells mm−3(OR 2.75; 95 % CI 1.09–7.69;P = 0.05). The model showed good calibration (Hosmer–Lemeshow chi-squared 1.61;P = 0.978). Area under the receiving operating characteristic curve was 0.944 (95 % CI 0.914–0.973;P<0.0001). These results suggest that a prediction model based on PCT and a few other routinely available laboratory and clinical variables could be of help in selecting patients with a high probability of SF-positive results

Comparison of the BD Phoenix System with the Cefoxitin Disk Diffusion Test for Detection of Methicillin Resistance in Staphylococcus aureus and Coagulase-Negative Staphylococci▿

The BD Phoenix system was compared to the cefoxitin disk diffusion test for detection of methicillin (meticillin) resistance in 1,066 Staphylococcus aureus and 1,121 coagulase-negative staphylococcus (CoNS) clinical isolates. The sensitivity for Phoenix was 100%. The specificities were 99.86% for S. aureus and 88.4% for CoNS

Procalcitonin predicts real-time PCR results in blood samples from patients with suspected sepsis.

Early diagnosis and rapid bacterial identification are of primary importance for outcome of septic patients. SeptiFast® (SF) real-time PCR assay is of potential utility in the etiological diagnosis of sepsis, but it cannot replace blood culture (BC) for routine use in clinical laboratory. Procalcitonin (PCT) is a marker of sepsis and can predict bacteremia in septic patients. The aim of the present study was to investigate whether PCT serum levels could predict SF results, and could help screening febrile patients in which a SF assay can improve the etiological diagnosis of sepsis.From 1009 febrile patients with suspected sepsis, 1009 samples for BC, SF real-time PCR, and PCT determination were obtained simultaneously, and results were compared and statistically analysed. Receiver operating characteristic (ROC) curves were generated to determine the area under the curve and to identify which cut-off of PCT value produced the best sensitivity to detect SF results.Mean PCT values of sera drawn simultaneously with samples SF positive (35.42 ± 61.03 ng/ml) or BC positive (23.14 ± 51.56 ng/ml) for a pathogen were statistically higher than those drawn simultaneously with SF negative (0.84 ± 1.67 ng/ml) or BC negative (2.79 ± 16.64 ng/ml) samples (p<0.0001). For SF, ROC analysis showed an area under the curve of 0.927 (95% confidence interval: 0.899-0.955, p<0.0001). The PCT cut-off value of 0.37 ng/ml showed a negative predictive value of 99%, reducing the number of SF assays of 53.9%, still identifying the 96.4% of the pathogens.PCT can be used in febrile patients with suspected sepsis to predict SF positive or negative results. A cut-off value of 0.37 ng/ml can be considered for optimal sensitivity, so that, in the routine laboratory activity, SF assay should not be used for diagnosis of sepsis in an unselected patient population with a PCT value <0.37 ng/ml

Bactericidal activity of oxacillin and glycopeptides against <it>Staphylococcus aureus </it>in patients with endocarditis: Looking for a relationship between tolerance and outcome

Abstract Background There is no clear relationship between in vitro bactericidal activity tests and clinical outcome. We studied bactericidal activity of oxacillin, vancomycin and teicoplanin against Staphylococcus aureus isolates in patients with endocarditis and then we sought to determine if there was a relationship between in vitro bactericidal activity and clinical outcome. Methods Minimal bacteriostatic and minimal bactericidal concentrations were determined for Staphylococcus aureus strains isolated from patients with endocarditis following standardized methods. Medical records were reviewed retrospectively to collect data on antimicrobial susceptibility at admission, antimicrobial therapy, need for surgery, embolic events and outcome. Results and Discussion Sixty-two Staphylococcus aureus strains were studied in 62 patients with endocarditis. Overall, 91.9% definite, 21% methicillin resistant and 72.6% cured. Surgery was performed in 32.3% and embolic events were documented in 64.5%. Tolerance to oxacillin and teicoplanin was more common than vancomycin tolerance among methicillin susceptible Staphylococcus aureus. Among methicillin resistant Staphylococcus aureus teicoplanin was shown to have a higher rate of tolerance than vancomycin. No statistically significant differences on clinical outcome between oxacillin tolerant and oxacillin non tolerant Staphylococcus aureus infections were observed. Tolerance to oxacillin did not adversely affect clinical outcomes of patients with methicillin susceptible Staphylococcus aureus endocarditis treated with a combination of antimicrobials including oxacillin. The cure rate was significantly lower among patients with methicillin resistant Staphylococcus aureus endocarditis. Conclusions In vitro bactericidal test results were not valid predictors of clinical outcome. Physicians need to use additional parameters when treating patients with staphylococcal endocarditis.</p

Sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, negative likelihood ratio of different cut-off values of PCT on SeptiFast results.

<p>PPV = positive predictive value.</p><p>NPV = negative predictive value.</p><p>LR+ = positive likelihood ratio.</p><p>LR− = negative likelihood ratio.</p

One hundred forty pathogens detected by SeptiFast (SF) and/or blood culture (BC) in 1009 patients.

1<p><i>Streptococcus</i> spp. group includes <i>S. agalactiae, S. pyogenes, S. anginosus</i>, <i>S. bovis</i>, <i>S. constellatus</i>, <i>S. cristatus</i>, <i>S. gordonii</i>, <i>S. intermedius, S. milleri, S. mitis, S. mutans, S. oralis, S. parasanguinis, S. salivarius, S. sanguinis, S. thermophilus, S. vestibularis, S. viridans</i>.</p>2<p>Coagulase-negative staphylococci group includes <i>S. epidermidis, S. haemolyticus, S. hominis, S. pasteuri, S. warneri, S. cohnii, S. lugdunensis, S. capitis, S. caprae, S. saprophyticus</i>, and <i>S. xylosus</i>.</p>3<p>ND, not included in the SF master list <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0053279#pone.0053279-Lehmann1" target="_blank">[6]</a>.</p

ROC curves for SeptiFast and blood cultures results according to different cut-off of PCT.

<p>SeptiFast: Area Under the Curve (AUC) = 0.927; 95% confidence interval (CI): 0.899–0.955, p<0.0001 (panel A). Blood culture: AUC = 0.820; 95% CI: 0.769–0.870, p>0.0001 (panel B).</p