Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Hospital visits among women with skeletal-related events secondary to breast cancer and bone metastases: a nationwide population-based cohort study in Denmark

Marie Louise Svendsen,1 Henrik Gammelager,1 Claus Sværke,1 Mellissa Yong,2 Victoria M Chia,2 Christian F Christiansen,1 Jon P Fryzek1 1Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark; 2Center for Observational Research, Amgen, Thousand Oaks, CA, USA Objective: Skeletal-related events (SREs) among women with breast cancer may be associated with considerable use of health-care resources. We characterized inpatient and outpatient hospital visits in a national population-based cohort of Danish women with SREs secondary to breast cancer and bone metastases. Methods: We identified first-time breast cancer patients with bone metastases from 2003 through 2009 who had a subsequent SRE (defined as pathologic fracture, spinal cord compression, radiation therapy, or surgery to bone). Hospital visits included the number of inpatient hospitalizations, length of stay, number of hospital outpatient clinic visits, and emergency room visits. The number of hospital visits was assessed for a pre-SRE period (90 days prior to the diagnostic period), a diagnostic period (14 days prior to the SRE), and a post-SRE period (90 days after the SRE). Patients who experienced more than one SRE during the 90-day post-SRE period were defined as having multiple SREs and were followed until 90 days after the last SRE. Results: We identified 569 women with SREs secondary to breast cancer with bone metastases. The majority of women had multiple SREs (73.1%). A total of 20.9% and 33.4% of women with single and multiple SREs died in the post-SRE period, respectively. SREs were associated with a large number of hospital visits in the diagnostic period, irrespective of the number and type of SREs. Women with multiple SREs generally had a higher number of visits compared to those with a single SRE in the post-SRE period, eg, median length of hospitalization was 5 days (interquartile range 0–15) for women with a single SRE and 13 days (interquartile range 4–30) for women with multiple SREs. Conclusion: SREs secondary to breast cancer and bone metastases were associated with substantial use of hospital resources. Keywords: breast neoplasms, bone metastases, skeletal-related events, hospital services, utilizatio

Treatment with belimumab in systemic lupus erythematosus does not impair antibody response to 13-valent pneumococcal conjugate vaccine.

Background/purpose: The objective of this study was to explore the impact of systemic lupuserythematosus and belimumab given in addition to standard of care therapy on 13-valentconjugated pneumococcal vaccine (PCV13) response. Methods: Forty-seven systemic lupuserythematosus patients and 21 healthy controls were immunized with a single dose of13-valent conjugated pneumococcal vaccine. Forty systemic lupus erythematosus patientswere treated with traditional disease-modifying anti rheumatic drugs, 11 of those receivedbelimumab in addition, and 32 patients were treated with concomitant prednisolone.Quantification of serotype specific IgG levels to 12 pneumococcal capsular polysaccharideswas performed in serum taken before and four to six weeks after vaccination using multiplexfluorescent microsphere immunoassay. IgG levels against serotypes 23F and 6B were alsoanalyzed using standard enzyme-linked immunosorbent assays. Opsonophagocyticassay was performed on serotype 23F to evaluate the functionality of the antibodies. Preandpost-vaccination log transformed antibody levels were compared to determine theimpact of systemic lupus erythematosus diagnosis and different treatments on antibodyresponse. Results: Systemic lupus erythematosus patients as a group showed lower postvaccinationantibody levels and lower fold increase of antibody levels after vaccinationcompared to controls (p¼0.02 and p¼0.009, respectively). Systemic lupus erythematosuspatients treated with belimumab in addition to standard of care therapy or with only hydroxychloroquinedid not differ compared to controls, whereas the other treatment groups hadsignificantly lower fold increase of post-vaccination antibody levels. Higher age was associatedwith lower post-vaccination antibody levels among systemic lupus erythematosuspatients. Conclusion: Belimumab given in addition to traditional disease-modifyinganti rheumatic drugs or prednisolone did not further impair antibody response to 13-valentconjugated pneumococcal vaccine