Archive for June 24, 2016

Multiplexed Anti-Toxoplasma IgG, IgM, and IgA Assay on Plasmonic Gold Chips: towards Making Mass Screening Possible with Dye Test Precision

Journal of Clinical Microbiology July 2016 V.54 N.7 P.1726-1733

Xiaoyang Li, Christelle Pomares, Géraldine Gonfrier, Byumseok Koh, Shoujun Zhu, Ming Gong, Jose G. Montoya, and Hongjie Dai

aDepartment of Chemistry, Stanford University, Stanford, California, USA

bDivision of Infectious Diseases, Stanford University, Stanford, California, USA

cPalo Alto Medical Foundation Toxoplasma Serology Laboratory, Palo Alto, California, USA

dINSERM, U1065, Centre Méditerranéen de Médecine Moléculaire, C3M, Toxines Microbiennes dans la Relation Hôte Pathogènes—Université de Nice Sophia Antipolis, Faculté de Médecine, Nice, France

eParasitologie-Mycologie, Centre Hospitalier Universitaire l’Archet, Nice, France

fVirologie, Centre Hospitalier Universitaire l’Archet, Nice, France

Toxoplasmosis is an infection caused by the protozoan parasite Toxoplasma gondii that can lead to severe sequelae in the fetus during pregnancy. Definitive serologic diagnosis of the infection during gestation is made mostly by detecting T. gondii-specific antibodies, including IgG and IgM, individually in a single serum sample by using commercially available kits. The IgA test is used by some laboratories as an additional marker of acute infection. Most of the commercial tests have failed to reach 100% correlation with the reference method, the Sabin-Feldman dye test for the detection of Toxoplasma IgG antibodies. For Toxoplasma IgM and IgA antibodies, there is no reference method and their evaluation is done by comparing the results of one assay to those of another. There is a need for multiplexed assay platforms, as the serological diagnosis of T. gondii infection does not rely on the detection of a single Ig subtype. Here we describe the development of a plasmonic gold chip with vast fluorescence enhancement in the near-infrared region for simultaneous detection of IgG, IgM, and IgA antibodies against T. gondii in an ∼1-μl serum or whole-blood sample. When 168 samples were tested on this platform, IgG antibody detection sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were all 100%. IgM antibody detection achieved 97.6% sensitivity and 96.9% specificity with a 90.9% PPV and a 99.2% NPV. Thus, the nanoscience-based plasmonic gold platform enables a high-performance, low-cost, multiplexed assay requiring ultrasmall blood volumes, paving the way for the implementation of universal screening for toxoplasmosis infection during gestation.

PDF

http://jcm.asm.org/content/54/7/1726.full.pdf+html

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June 24, 2016 at 2:02 pm

Do Staphylococcus epidermidis Genetic Clusters Predict Isolation Sources?

Journal of Clinical Microbiology July 2016 V.54 N.7 P.1711-1719

Isaiah Tolo, Jonathan C. Thomas, Rebecca S. B. Fischer, Eric L. Brown, Barry M. Gray, and D. Ashley Robinson

aDepartment of Microbiology and Immunology, University of Mississippi Medical Center, Jackson, Mississippi, USA

bDepartment of Biology, University of Bolton, Bolton, United Kingdom

cCenter for Infectious Disease, University of Texas Health Science Center, Houston, Texas, USA

dDepartment of Pediatrics, University of Illinois College of Medicine at Peoria, Peoria, Illinois, USA

Staphylococcus epidermidis is a ubiquitous colonizer of human skin and a common cause of medical device-associated infections. The extent to which the population genetic structure of S. epidermidis distinguishes commensal from pathogenic isolates is unclear. Previously, Bayesian clustering of 437 multilocus sequence types (STs) in the international database revealed a population structure of six genetic clusters (GCs) that may reflect the species’ ecology. Here, we first verified the presence of six GCs, including two (GC3 and GC5) with significant admixture, in an updated database of 578 STs. Next, a single nucleotide polymorphism (SNP) assay was developed that accurately assigned 545 (94%) of 578 STs to GCs. Finally, the hypothesis that GCs could distinguish isolation sources was tested by SNP typing and GC assignment of 154 isolates from hospital patients with bacteremia and those with blood culture contaminants and from nonhospital carriage. GC5 was isolated almost exclusively from hospital sources. GC1 and GC6 were isolated from all sources but were overrepresented in isolates from nonhospital and infection sources, respectively. GC2, GC3, and GC4 were relatively rare in this collection. No association was detected between fdh-positive isolates (GC2 and GC4) and nonhospital sources. Using a machine learning algorithm, GCs predicted hospital and nonhospital sources with 80% accuracy and predicted infection and contaminant sources with 45% accuracy, which was comparable to the results seen with a combination of five genetic markers (icaA, IS256, sesD [bhp], mecA, and arginine catabolic mobile element [ACME]). Thus, analysis of population structure with subgenomic data shows the distinction of hospital and nonhospital sources and the near-inseparability of sources within a hospital.

PDF

http://jcm.asm.org/content/54/7/1711.full.pdf+html

June 24, 2016 at 2:01 pm

Towards Universal Screening for Toxoplasmosis: Rapid, Cost-Effective, and Simultaneous Detection of Anti-Toxoplasma IgG, IgM, and IgA Antibodies by Use of Very Small Serum Volumes

Journal of Clinical Microbiology July 2016 V.54 N.7 P.1684-1685

Swinburne A. J. Augustine

National Exposure Research Laboratory, Exposure Methods and Measurement Division, Microbial Exposure Branch, United States Environmental Protection Agency, Cincinnati, Ohio, US

Rapid, cost-effective, and early determination of the serological status of potentially infected individuals, particularly pregnant women, can be critical in preventing life-threatening infections and subsequent fetal congenital abnormalities. An article in this issue of the Journal of Clinical Microbiology (X. Li, C. Pomares, G. Gonfrier, B. Koh, S. Zhu, M. Gong, J. G. Montoya, and H. Dai, J Clin Microbiol 54:1726–1733, 2016, http://dx.doi.org/10.1128/JCM.03371-15) describes an innovative multiplexed immunoassay that offers a path toward universal screening.

PDF

http://jcm.asm.org/content/54/7/1684.full.pdf+html

June 24, 2016 at 2:00 pm

Significance of Staphylococcus epidermidis in Health Care-Associated Infections, from Contaminant to Clinically Relevant Pathogen: This Is a Wake-Up Call!

Journal of Clinical Microbiology July 2016 V.54 N.7 P.1679-1681

Micael Widerström

Department of Clinical Microbiology, Infectious Diseases, Unit of Research, Education and Development-Östersund, Umeå University, Umeå, Sweden

Coagulase-negative staphylococci, particularly Staphylococcus epidermidis, have been recognized as an important cause of health care-associated infections. Concurrently, S. epidermidis is a common contaminant in clinical cultures, which poses a diagnostic challenge. An article in this issue of Journal of Clinical Microbiology (I. Tolo, J. C. Thomas, R. S. B. Fischer, E. L. Brown, B. M. Gray, and D. A. Robinson, J Clin Microbiol 54:1711–1719, 2015, http://dx.doi.org/10.1128/JCM.03345-15) describes a rapid single nucleotide polymorphism-based assay for distinguishing between S. epidermidis isolates from hospital and nonhospital sources, which represents an important contribution to the characterization and understanding of S. epidermidis health care-associated infections.

PDF

http://jcm.asm.org/content/54/7/1679.full.pdf+html

June 24, 2016 at 1:59 pm

The Brief Case – Cryptococcus gattii Meningitis with Ventriculitis

Journal of Clinical Microbiology July 2016 V.54 N.7 P.1676-1678

Lars F. Westblade and Eileen M. Burd

aDepartment of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, New York, USA

bDepartment of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, Georgia, USA

cEmory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, Georgia, USA

A 39-year-old previously healthy man was transferred to Emory University Hospital Midtown, Atlanta, GA, USA, from Savannah, GA, USA, with a 1-month history of progressive headaches, drowsiness, blurred vision, and photosensitivity. Magnetic resonance imaging (MRI) revealed a noncommunicating obstructive hydrocephalus at the level of the third ventricle. Endoscopic ventriculostomy was attempted but could not be completed because of marked adhesions, scar tissue, and nodularity throughout the ependymal surfaces of the lateral ventricles. An external ventricular drainage catheter was placed, and a cerebrospinal fluid (CSF) sample was obtained. The CSF was bloody, with a normal glucose level of 40 mg/dl (normal range, 40 to 70 mg/dl), a corresponding serum glucose level of 100 mg/dl (normal range, 65 to 110 mg/dl), and an elevated CSF protein level of 148 mg/dl (normal range, 15 to 45 mg/dl). The CSF white blood cell count was elevated at 25 cells/μl (normal range, 0 to 5 cells/μl) with predominantly polymorphonuclear neutrophils (PMNs) (67%). A CSF Gram stain showed few PMNs but no organisms. A CSF cryptococcal latex agglutination antigen test (Meridian Bioscience Inc., Cincinnati, OH, USA) was negative, but a serum cryptococcal antigen titer performed a few days later was 32. Blood cultures taken at that time showed no growth, but bacterial and fungal cultures of the CSF grew a few cream-colored, mucoid colonies in 3 days (Fig. 1A). Direct microscopic examination of the colonies revealed round yeast cells that tested germ tube negative (Fig. 1B). The organism was able to hydrolyze urea, and a caffeic acid disk test was positive for melanin production, consistent with Cryptococcus neoformans, but upon growth, a blue coloration was produced on L-canavanine–glycine–bromothymol blue (CGB) agar (Centers for Disease Control and Prevention [CDC], Atlanta, GA, USA), distinguishing the isolate as Cryptococcus gattii (Fig. 1C). The identification was confirmed as C. gattii biotype VGI at the CDC by multilocus sequence typing, with 100% identity to the reference isolate across 4,141 nucleotides

PDF

http://jcm.asm.org/content/54/7/1676.full.pdf+html

 

Journal of Clinical Microbiology July 2016 V.54 N.7 P.1934

Closing the Brief Case: Cryptococcus gattii Meningitis with Ventriculitis

Lars F. Westblade and Eileen M. Burd

aDepartment of Pathology and Laboratory Medicine, Weill Cornell Medical College, New York, New York, USA

bDepartment of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, Georgia, USA

cEmory Antibiotic Resistance Center, Emory University School of Medicine, Atlanta, Georgia, USA

ANSWERS TO SELF-ASSESSMENT QUESTIONS

PDF

http://jcm.asm.org/content/54/7/1934.full.pdf+html

June 24, 2016 at 1:57 pm


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