Identification of hypermucoviscous Klebsiella pneumoniae K1, K2, K54 and K57 capsular serotypes by Raman spectroscopy.

Antimicrobial resistance poses a significant challenge in modern medicine, affecting public health. Klebsiella pneumoniae infections compound this issue due to their broad range of infections and the emergence of multiple antibiotic resistance mechanisms. Efficient detection of its capsular serotypes is crucial for immediate patient treatment, epidemiological tracking and outbreak containment. Current methods have limitations that can delay interventions and increase the risk of morbidity and mortality. Raman spectroscopy is a promising alternative to identify capsular serotypes in hypermucoviscous K. pneumoniae isolates. It provides rapid and in situ measurements with minimal sample preparation. Moreover, its combination with machine learning tools demonstrates high accuracy and reproducibility. This study analyzed the viability of combining Raman spectroscopy with one-dimensional convolutional neural networks (1-D CNN) to classify four capsular serotypes of hypermucoviscous K. pneumoniae: K1, K2, K54 and K57. Our approach involved identifying the most relevant Raman features for classification to prevent overfitting in the training models. Simplifying the dataset to essential information maintains accuracy and reduces computational costs and training time. Capsular serotypes were classified with 96 % accuracy using less than 30 Raman features out of 2400 contained in each spectrum. To validate our methodology, we expanded the dataset to include both hypermucoviscous and non-mucoid isolates and distinguished between them. This resulted in an accuracy rate of 94 %. The results obtained have significant potential for practical healthcare applications, especially for enabling the prompt prescription of the appropriate antibiotic treatment against infections.

Do high MICs predict the outcome in invasive fusariosis?

BACKGROUND: Invasive fusariosis (IF) affects mostly severely immunocompromised hosts and is associated with poor outcome. Since Fusarium species exhibit high MICs for most antifungal agents, this could explain the poor prognosis. However, a clear-cut correlation between MIC and outcome has not been established. OBJECTIVE: To evaluate the correlation between MIC and outcome (6 week death rate) in patients with IF. METHODS: We performed a multicentre retrospective study of patients with IF who received treatment and had MIC levels determined by EUCAST or CLSI for the drug(s) used during treatment. We compared the MIC50 and MIC distribution among survivors and patients who died within 6 weeks from the diagnosis of IF. RESULTS: Among 88 patients with IF, 74 had haematological diseases. Primary treatment was monotherapy in 52 patients (voriconazole in 27) and combination therapy in 36 patients (liposomal amphotericin B + voriconazole in 23). The MIC50 and range for the five most frequent agents tested were: voriconazole 8 mg/L (range 0.5-64), amphotericin B 2 mg/L (range 0.25-64), posaconazole 16 mg/L (range 0.5-64), itraconazole 32 mg/L (range 4-64), and isavuconazole 32 mg/L (range 8-64). There was no difference in MIC50 and MIC distribution among survivors and patients who died. By contrast, persistent neutropenia and receipt of corticosteroids were strong predictors of 6 week mortality. CONCLUSIONS: Our study did not show any correlation between MIC and mortality at 6 weeks in patients with IF.

Repetición del test Platelia Aspergillus en muestras positivas para la detección de galactomanano en suero: ¿es necesario repetir el test? / Repeating the Platelia Aspergillus test in samples positive for serum galactomannan: Is it necessary?

Background. The manufacturers of the Platelia Aspergillus test recommend retesting every sample with a positive result to galactomannan detection. Aims. To evaluate the repeated results of the Platelia Aspergillus test on initially positive samples, and their association with clinical and microbiological studies. Methods. A total of 150 positive sera belonging to 92 patients were studied. More than one positive sample was obtained from 31 (33.6%) patients. Nine patients were diagnosed with probable invasive aspergillosis and two with proven Fusarium oxysporum and Scedosporium prolificans invasive fungal infection, respectively. Results. Only 35 out of 150 (23.3%) sera remained positive upon test repetition. The average OD-index difference between the initially positive and subsequently negative samples was 0.76. Sera from 3 patients out of 9 diagnosed with probable invasive aspergillosis yielded negative results after repetition. Conclusions. Our study shows poor reproducibility of the positive samples for the Platelia Aspergillus test. These results reinforce the need to evaluate a second sample and to consider simultaneously repeating the first positive serum to enhance the diagnosis of invasive fungal infection (AU)

Antecedentes. Los fabricantes del test Platelia Aspergillus recomiendan repetir todas aquellas muestras positivas para la detección de galactomanano. Objetivos. Evaluación de los resultados de la repetición del test Platelia Aspergillus en muestras inicialmente positivas y su correlación con estudios clínico-microbiológicos. Métodos. Se han estudiado 150 sueros positivos pertenecientes a 92 pacientes, de los cuales 31 (33,6%) tenían más de una muestra positiva. Nueve pacientes fueron diagnosticados de aspergilosis invasiva probable y dos de infección fúngica invasiva probada por Fusarium oxysporum y Scedosporium prolificans. Resultados. Solamente 35 de los 150 sueros (23,3%) siguieron siendo positivos al repetir el ensayo. La media de la diferencia del índice OD entre las muestras inicialmente positivas y después negativas fue de 0,76. En 3 de los 9 pacientes diagnosticados de aspergilosis invasiva probable se obtuvo negativización de todas las muestras inicialmente positivas al repetir el ensayo. Conclusiones. Nuestro estudio muestra una pobre reproducibilidad en los resultados positivos del test Platelia Aspergillus. Estos resultados apoyan la necesidad de evaluar una segunda muestra junto a la repetición simultánea de la primera que resultó positiva para reforzar el diagnóstico de infección fúngica invasiva (AU)

[Repeating the Platelia™ Aspergillus test in samples positive for serum galactomannan: Is it necessary?]. / Repetición del test Platelia™ Aspergillus en muestras positivas para la detección de galactomanano en suero: ¿es necesario repetir el test?

BACKGROUND: The manufacturers of the Platelia™ Aspergillus test recommend retesting every sample with a positive result to galactomannan detection. AIMS: To evaluate the repeated results of the Platelia™ Aspergillus test on initially positive samples, and their association with clinical and microbiological studies. METHODS: A total of 150 positive sera belonging to 92 patients were studied. More than one positive sample was obtained from 31 (33.6%) patients. Nine patients were diagnosed with probable invasive aspergillosis and two with proven Fusarium oxysporum and Scedosporium prolificans invasive fungal infection, respectively. RESULTS: Only 35 out of 150 (23.3%) sera remained positive upon test repetition. The average OD-index difference between the initially positive and subsequently negative samples was 0.76. Sera from 3 patients out of 9 diagnosed with probable invasive aspergillosis yielded negative results after repetition. CONCLUSIONS: Our study shows poor reproducibility of the positive samples for the Platelia™ Aspergillus test. These results reinforce the need to evaluate a second sample and to consider simultaneously repeating the first positive serum to enhance the diagnosis of invasive fungal infection.

Impact of empirical treatment in extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella spp. bacteremia. A multicentric cohort study.

BACKGROUND: The objective of this study is to analyze the factors that are associated with the adequacy of empirical antibiotic therapy and its impact in mortality in a large cohort of patients with extended-spectrum ß-lactamase (ESBL)--producing Escherichia coli and Klebsiella spp. bacteremia. METHODS: Cases of ESBL producing Enterobacteriaceae (ESBL-E) bacteremia collected from 2003 through 2008 in 19 hospitals in Spain. Statistical analysis was performed using multivariate logistic regression. RESULTS: We analyzed 387 cases ESBL-E bloodstream infections. The main sources of bacteremia were urinary tract (55.3%), biliary tract (12.7%), intra-abdominal (8.8%) and unknown origin (9.6%). Among all the 387 episodes, E. coli was isolated from blood cultures in 343 and in 45.71% the ESBL-E was multidrug resistant. Empirical antibiotic treatment was adequate in 48.8% of the cases and the in hospital mortality was 20.9%. In a multivariate analysis adequacy was a risk factor for death [adjusted OR (95% CI): 0.39 (0.31-0.97); P = 0.04], but not in patients without severe sepsis or shock. The class of antibiotic used empirically was not associated with prognosis in adequately treated patients. CONCLUSION: ESBL-E bacteremia has a relatively high mortality that is partly related with a low adequacy of empirical antibiotic treatment. In selected subgroups the relevance of the adequacy of empirical therapy is limited.

Time to positivity in blood cultures of adults with Streptococcus pneumoniae bacteremia.

BACKGROUND: previous studies have established that bacterial blood concentration is related with clinical outcome. Time to positivity of blood cultures (TTP) has relationship with bacterial blood concentration and could be related with prognosis. As there is scarce information about the usefulness of TTP, we study the relationship of TTP with clinical parameters in patients with Streptococcus pneumoniae bacteremia. METHODS: TTP of all cases of Streptococcus pneumoniae bacteremia, detected between January 1995 and December 2004 using the BacT/Alert automated blood culture system in a teaching community hospital was analyzed. When multiple cultures were positive only the shortest TTP was selected for the analysis. RESULTS: in the study period 105 patients with Streptococcus pneumoniae bacteremia were detected. Median TTP was 14.1 hours (range 1.2 h to 127 h). Immunosuppressed patients (n = 5), patients with confusion (n = 19), severe sepsis or shock at the time of blood culture extraction (n = 12), those with a diagnosis of meningitis (n = 7) and those admitted to the ICU (n = 14) had lower TTP. Patients with TTP in the first quartile were more frequently hospitalized, admitted to the ICU, had meningitis, a non-pneumonic origin of the bacteremia, and a higher number of positive blood cultures than patients with TTP in the fourth quartile. None of the patients with TTP in the 90th decile had any of these factors associated with shorter TTP, and eight out of ten patients with TTP in the 10th decile had at least one of these factors. The number of positive blood cultures had an inverse correlation with TTP, suggesting a relationship of TTP with bacterial blood concentration. CONCLUSION: Our data support the relationship of TTP with several clinical parameters in patients with Streptococcus pneumoniae bacteremia, and its potential usefulness as a surrogate marker of outcome.