Robert F. Luo

Is Repeat PCR Needed for Diagnosis of Clostridium difficile Infection

ABSTRACT Patients with diarrhea, defined as loose or watery stool, and two or more Clostridium difficile tcdB PCR tests within 14 days of each other were investigated. Repeat PCR for 293 patients with a prior negative result yielded negative results in 396 (97.5%) of 406 tests. Ten new positives were detected, including one false positive. Repeat PCR within 7 days appears rarely useful, except for patients with evidence of a new infection.

Real-Time PCR Testing for mecA Reduces Vancomycin Usage and Length of Hospitalization for Patients Infected with Methicillin-Sensitive Staphylococci

ABSTRACT Nucleic acid amplification tests (NAATs) have revolutionized infectious disease diagnosis, allowing for the rapid and sensitive identification of pathogens in clinical specimens. Real-time PCR testing for the mecA gene (mecA PCR), which confers methicillin resistance in staphylococci, has the added potential to reduce antibiotic usage, improve clinical outcomes, lower health care costs, and avoid emergence of drug resistance. A retrospective study was performed to identify patients infected with methicillin-sensitive staphylococcal isolates who were receiving vancomycin treatment when susceptibility results became available. Vancomycin treatment and length of hospitalization were compared in these patients for a 6-month period before and after implementation of mecA PCR. Among 65 and 94 patients identified before and after mecA PCR, respectively, vancomycin usage (measured in days on therapy) declined from a median of 3 days (range, 1 to 44 days) in the pre-PCR period to 1 day (range, 0 to 18 days) in the post-PCR period (P < 0.0001). In total, 38.5% (25/65) of patients were switched to β-lactam therapy in the pre-PCR period, compared to 61.7% (58/94) in the post-PCR period (P = 0.004). Patient hospitalization days also declined from a median of 8 days (range, 1 to 47 days) in the pre-PCR period to 5 days (range, 0 to 42 days) in the post-PCR period (P = 0.03). Real-time PCR testing for mecA is an effective tool for reducing vancomycin usage and length of stay of hospitalized patients infected with methicillin-sensitive staphylococci. In the face of ever-rising health care expenditures in the United States, these findings have important implications for improving outcomes and decreasing costs.

Preferential lower respiratory tract infection in swine-origin 2009 A(H1N1) influenza.

We report a case of 2009 influenza A(H1N1) virus infection in which virus was detected predominantly in specimens from the lower respiratory tract but was absent or at very low levels in nasopharyngeal swab samples. This presentation suggests that, in certain hosts or for particular variants of 2009 A(H1N1) virus, the lower respiratory tract may be the preferred site of infection.

Comparison of Single-Copy and Multicopy Real-Time PCR Targets for Detection of Mycobacterium tuberculosis in Paraffin-Embedded Tissue

ABSTRACT Real-time PCR can rapidly identify Mycobacterium tuberculosis in paraffin-embedded tissue in the absence of microbiological culture. In a comparison of single-copy and multicopy PCR targets in 70 tissue samples, the sensitivities were 26% and 54%, respectively, with 100% specificity. Sensitivity was 75% for newer samples and was not decreased for acid-fast bacillus (AFB) stain-negative specimens.

Performance of Xpert MTB/RIF on pleural tissue for the diagnosis of pleural tuberculosis

To the Editor: Tuberculosis (TB) remains the second leading cause of death from an infectious disease in adults. Extrapulmonary TB (EPTB) accounts for about 25% of all cases of active TB. Pleural TB is the second most common manifestation of EPTB. Existing tests for the diagnosis of pleural TB have major limitations in terms of accuracy, time to diagnosis and drug resistance testing, and require special expertise for sample acquisition and interpretation of the results. Biopsy of the pleural tissue for combined histological examination and culture is considered the diagnostic gold standard, albeit imperfect [1, 2]. The Xpert MTB/RIF assay (Xpert; Cepheid, Sunnyvale, CA, USA) is a rapid, World Health Organization (WHO) endorsed, automated PCR test optimised for respiratory specimens that can detect both Mycobacterium tuberculosis (MTB) and rifampicin resistance [3, 4]. Given the limitations of available tests for the diagnosis of pleural TB, several studies have evaluated the performance of Xpert using pleural fluid as a sample type. Overall, these studies show limited accuracy with sensitivity averaging around 44% [5–7]. However, the preferred specimen for the diagnosis of pleural TB is pleural tissue. To date, the evaluation of Xpert performed on pleural tissue has been limited to isolated samples within larger studies [4, 6, 7]. We enrolled consecutive adult patients that were evaluated for pleural TB in the pulmonary clinic and inpatient ward at the Christian Medical College, Vellore, India. Pleural TB was suspected based on clinical symptoms and radiographic evidence of a pleural effusion. Information on demographics, comorbidities, presenting symptoms and results of diagnostic evaluation were collected prospectively. The institutional review boards of the Christian Medical College …

CD81 protein is expressed at high levels in normal germinal center B cells and in subtypes of human lymphomas

CD81 is a tetraspanin cell surface protein that regulates CD19 expression in B lymphocytes and enables hepatitis C virus infection of human cells. Immunohistologic analysis in normal hematopoietic tissue showed strong staining for CD81 in normal germinal center B cells, a cell type in which its increased expression has not been previously recognized. High-dimensional flow cytometry analysis of normal hematopoietic tissue confirmed that among B- and T-cell subsets, germinal center B cells showed the highest level of CD81 expression. In more than 800 neoplastic tissue samples, its expression was also found in most non-Hodgkin lymphomas. Staining for CD81 was rarely seen in multiple myeloma, Hodgkin lymphoma, or myeloid leukemia. In hierarchical cluster analysis of diffuse large B-cell lymphoma, staining for CD81 was most similar to other germinal center B cell-associated markers, particularly LMO2. By flow cytometry, CD81 was expressed in diffuse large B-cell lymphoma cells independent of the presence or absence of CD10, another germinal center B-cell marker. The detection of CD81 in routine biopsy samples and its differential expression in lymphoma subtypes, particularly diffuse large B-cell lymphoma, warrant further study to assess CD81 expression and its role in the risk stratification of patients with diffuse large B-cell lymphoma.

Engineering the Stereochemistry of Cephalosporin for Specific Detection of Pathogenic Carbapenemase‐Expressing Bacteria

Reported herein is the design of fluorogenic probes specific for carbapenem-resistant Enterobacteriaceae (CRE) and they were designed based on stereochemically modified cephalosporin having a 6,7-trans configuration. Through experiments using recombinant β-lactamase enzymes and live bacterial species, these probes demonstrate the potential for use in the specific detection of carbapenemases, including metallo-β-lactamases in active bacterial pathogens.

Brain Abscess Caused by Phaeoacremonium parasiticum in an Immunocompromised Patient

ABSTRACT Phaeoacremonium parasiticum is an environmental fungus usually associated with subcutaneous infections. We report the first documented case of central nervous system involvement with brain abscess formation in a patient with chronic granulomatous disease and review the literature on Phaeoacremonium parasiticum infections.

Alerting Physicians during Electronic Order Entry Effectively Reduces Unnecessary Repeat PCR Testing for Clostridium difficile

ABSTRACT Hospital information systems (HIS) alerts restricting repeat Clostridium difficile PCR ordering by physicians in patients with a prior result within 7 days eliminated 91% of repeat tests, from 14.5% (282/1,949) repeats preintervention to 1.3% (135/10,285) postintervention. HIS alerting is an effective, targeted, patient-specific tool for improving the quality and utilization of C. difficile results.

Transient facial swellings in a patient with a remote African travel history.

We present a case of Loa loa infection in a patient, 21 years after visiting an endemic area for only 4 days. To our knowledge, this case represents the longest time for the diagnosis of loiasis to be made post-exposure in a traveler and emphasizes that even short exposures can place travelers at risk.