Neil W. Anderson

Detection of prosthetic joint biofilm infection using immunological and molecular techniques

Publisher Summary This chapter describes how the detection of bacteria by culture from revision hip prostheses can be improved by employing strict anaerobic techniques and by using mild ultrasonication to dislodge bacteria adhering to the surface of the retrieved implants. Nonculture techniques that can be used to further improve the detection of infection, including examination of the inflammatory response in implant-associated tissue and the detection of bacteria using immunological and polymerase chain reaction (PCR)-based molecular approaches, are also described. The use of strict anaerobic techniques and mild ultrasonication has resulted in bacteria being cultured from 26 of 120 (22%) retrieved implants examined. The use of nonculture techniques to improve the detection of prosthetic joint biofilm infection coupled with appropriate postoperative antibiotic therapy should improve the clinical outcome for patients undergoing revision hip surgery.

Comparison of Three Immunoassays for Detection of Antibodies to Strongyloides stercoralis

ABSTRACT Due to the limited sensitivities of stool-based microscopy and/or culture techniques for Strongyloides stercoralis, the detection of antibodies to this intestinal nematode is relied upon as a surrogate for determining exposure status or making a diagnosis of S. stercoralis infection. Here, we evaluated three immunoassays, including the recently released InBios Strongy Detect IgG enzyme-linked immunosorbent assay (ELISA) (InBios International, Inc., Seattle, WA), the SciMedx Strongyloides serology microwell ELISA (SciMedx Corporation, Denville, NJ), and the luciferase immunoprecipitation system (LIPS) assay performed at the National Institutes of Health (NIH), for their detection of IgG antibodies to S. stercoralis. A total of 101 retrospective serum samples, previously submitted for routine S. stercoralis antibody detection using the SciMedx assay, were also evaluated by the InBios and LIPS assays. The qualitative results from each assay were compared using a Venn diagram analysis, to the consensus result among the three assays, and each ELISA was also evaluated using the LIPS assay as the reference standard. By Venn diagram analysis, 65% (66/101) of the samples demonstrated perfect agreement by all three assays. Also, the numbers of samples considered positive or negative by a single method were similar. Compared to the consensus result, the overall percent agreement of the InBios, SciMedx, and LIPS assays were comparable at 87.1%, 84.2%, and 89.1%, respectively. Finally, the two ELISAs performed analogously but demonstrated only moderate agreement (kappa coefficient for the two assays, 0.53) with the LIPS assay. Collectively, while the two commercially available ELISAs perform equivalently, neither should be used independently of clinical evaluation to diagnose strongyloidiasis.

Morbidity and mortality among patients with respiratory syncytial virus infection: a 2-year retrospective review

Previous studies have demonstrated high morbidity and mortality for adult patients with respiratory syncytial virus (RSV) infection. We performed a retrospective, multicenter, two-year chart review of all patients (n = 334) testing positive for RSV by the ProFlu + (®) Influenza A/B and RSV assay (Hologic, Bedford, MA). We analyzed indicators of morbidity and mortality in children <6 years old, immunocompetent and immunosuppressed adults, and transplant patients. Significant morbidity and mortality was observed among hematopoietic stem cell transplant patients (7.3%, 60-day mortality), solid organ transplant patients (13.3%, 60-day mortality), and COPD patients (12.8%, 60-day mortality). Of the patients positive for RSV, 144 (43.1%) of 334 received antibacterials or antifungals following diagnosis. Of these patients, a bacterial or fungal pathogen was not recovered from 60% of cases. Despite advances in RSV treatment, certain populations appear to be inadequately treated, while others appear to be inappropriately treated with unnecessary antimicrobials.

Simultaneous Detection of Herpes Simplex Virus 1 and 2 in the Cerebrospinal Fluid of a Patient with Seizures and Encephalitis

ABSTRACT We report a case of a 62-year-old female with seizures and encephalitis. Molecular testing of the patients cerebrospinal fluid was positive for both herpes simplex virus 1 and 2 (HSV-1 and HSV-2). To our knowledge, this is the first report of simultaneous detection of HSV-1 and HSV-2 in cerebrospinal fluid.

Detection of the dengue virus NS1 antigen using an enzyme immunoassay

Current diagnostic methods for dengue virus (DV) rely primarily on detection of anti-DV antibodies and/or DV RNA by reverse transcriptase (RT) PCR. Several limitations exist however: seroconversion is delayed following infection, and DV RT-PCR assays are not yet readily available. The DV nonstructural protein 1 (NS1) antigen is an alternative acute phase DV biomarker, and here, we evaluated the new InBios (InBios International, Inc., Seattle, WA, USA) DENV Detect(TM) NS1 enzyme-linked immunoassay (ELISA) compared to DV RT-PCR and serology for detection of recent DV infection. We report a positive, negative, and overall percent agreement of 96% (24/25), 86.0% (43/50), and 89.3% (67/75) for the InBios NS1 ELISA compared to DV RT-PCR. Performance of the NS1 ELISA compared to serology for anti-DV IgM antibodies showed a positive, negative, and overall percent agreement of 78.0% (85/109), 90.7% (333/367), and 87.8% (418/476), respectively. Collectively, the InBios NS1 ELISA can be used as an alternative to DV RT-PCR for identification of acute DV infection.

When Good Bugs Go Bad: Epidemiology and Antimicrobial Resistance Profiles of Corynebacterium striatum, an Emerging Multidrug-Resistant, Opportunistic Pathogen.

ABSTRACT Infections with Corynebacterium striatum have been described in the literature over the last 2 decades, with the majority being bacteremia, central line infections, and occasionally, endocarditis. In recent years, the frequency of C. striatum infections appears to be increasing; a factor likely contributing to this is the increased ease and accuracy of the identification of Corynebacterium spp., including C. striatum, from clinical cultures. The objective of this study was to retrospectively characterize C. striatum isolates recovered from specimens submitted as part of routine patient care at a 1,250-bed, tertiary-care academic medical center. Multiple strain types were recovered, as demonstrated by repetitive-sequence-based PCR. Most of the strains of C. striatum characterized were resistant to antimicrobials commonly used to treat Gram-positive organisms, such as penicillin, ceftriaxone, meropenem, clindamycin, and tetracycline. The MIC50 for ceftaroline was >32 μg/ml. Although there are no interpretive criteria for susceptibility with telavancin, it appeared to have potent in vitro efficacy against this species, with MIC50 and MIC90 values of 0.064 and 0.125 μg/ml, respectively. Finally, as previously reported in case studies, we demonstrated rapid in vitro development of daptomycin resistance in 100% of the isolates tested (n = 50), indicating that caution should be exhibited when using daptomycin for the treatment of C. striatum infections. C. striatum is an emerging, multidrug-resistant pathogen that can be associated with a variety of infection types.

Pathology Consultation on Influenza Diagnostics.

Abstract Objectives: To describe the strengths and limitations of the available influenza diagnostics, with a focus on rapid antigen detection assays and nucleic acid detection assays. Methods: A case-based presentation is used to illustrate the potential limitations of rapid antigen detection assays for influenza. Results: Influenza is a seasonal illness; estimates attribute influenza to approximately 200,000 hospitalizations and 41,000 deaths in the United States annually. Antigen detection assays for influenza are rapid and convenient, and thus are widely used in a variety of health care settings, even though the sensitivity of these assays may be suboptimal. The United States Food and Drug Administration has recently created new guidelines intended to improve the oversight and performance characteristics of influenza antigen detection assays. Molecular assays, although more costly and complex, are more sensitive and may be designed to simultaneously detect multiple respiratory pathogens within a single assay. Conclusions: Diagnostic assays for influenza can vary greatly with regards to analytical performance characteristics, complexity, turnaround time and cost. This can have important patient care and infection prevention implications.

Peaks of Promise and Peril: Screening for Antibiotic Resistance by Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry

ABSTRACT An article in this issue of the Journal of Clinical Microbiology (J.-H. Youn, S. K. Drake, R. A. Weingarten, K. M. Frank, J. P. Dekker, and A. F. Lau, J Clin Microbiol 53:35–42, 2015, http://dx.doi.org/10.1128/JCM.01643-15) describes the use of matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) mass spectrometry for the detection of organisms carrying a bla KPC-containing plasmid. This powerful and promising application highlights the challenges of using MALDI-TOF mass spectrometry for purposes other than organism identification.

The Brief Case: A Reactive HIV Rapid Antibody Test in a Pregnant Woman

A 32-year-old pregnant woman presented to her obstetrician for routine prenatal care during her 3rd month of pregnancy. She reported no major health concerns, with the exception of mild morning sickness that had been gradually improving. Upon physical examination, she appeared healthy and her vitals

A Rare Presentation of a Common Disease

A sexually active 25-year-old nulliparous woman presented for a routine gynecological checkup. The patient reported normal menses, including her last menstrual period 2 weeks prior. Her past medical history included multiple sexual partners and an episode of gonococcal cervicitis at age 21 which