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

Cationic polyelectrolytes: A new look at their possible roles as opsonins, as stimulators of respiratory burst in leukocytes, in bacteriolysis, and as modulators of immune-complex diseases (A review hypothesis)

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44497/1/10753_2004_Article_BF00915991.pd

Characterization of Clostridioides difficile strains, the disease severity and the microbial changes they induce

Abstract Background In recent years, the global incidence of Clostridioides difficile infection has increased dramatically, with the emergence of hyper-virulent strains. The characteristics of the different strains, the severity of the disease they cause, their susceptibility to antimicrobial agents, and the changes they inflict on the gut microbiome, have not yet been comprehensively studied. Results Using Multilocus Sequencing Typing (MLST) analysis, the different sequence types (STs) of 70 clinical isolates were determined. The most frequent strains were ST04 (22.5%), ST37 (12.7%), ST104 (8.5%), ST42 (7%), and ST02 (7%). The different STs were divided to different phylogenetic lineages (clades), with clade 1 forming the majority of cases (81.4%, 57/70). A significant correlation was found between ST and age (p = 0.024); patients with ST104 (n = 6) were of the lowest mean age (61.67 ± 18.8 years), while patients with ST37 (n = 9) were of the oldest mean age (79.67 ± 10.6 years). In addition, a significant correlation between ST and susceptibility to moxifloxacin was identified (p = 0.001); 15 ST04 isolates (93.7%, n = 16) were resistant, while all ST42 (n = 5) and ST104 isolates (n = 6) were sensitive. Significant correlations were found between clade and binary toxin gene presence (p = 0.002), with 93% of the isolates belonging to clade 1 lacking the gene. Furthermore, significant correlations were found between clade and susceptibility to both metronidazole and vancomycin (p = 0.024, p = 0.035, respectively). Differences in intestinal microbiome were affected by age, clade distribution and ST. Conclusions By defining the characteristics of the different strains and clades, clinicians can choose medical interventions based on the predicted response or disease severity associated with each strain, enabling new advances in the field of personalized medicine.</jats:p

Characterization of Clostridioides difficile Strains, the Disease Severity, and the Microbial Changes They Induce

Background: Clostridioides difficile infection (CDI) is a major nosocomial disease. The characteristics of different strains, the disease severity they cause, their susceptibility to antibiotics, and the changes they inflict on gut microbiome, have not been comprehensively studied in Israel. Methods: A severity score was calculated for 70 patients. Stool samples were tested for toxins presence using a special kit. Bacteria were isolated, identified by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) and antibiotic susceptibility tests were performed for several antibiotics. Strains were classified by Multi-locus sequence typing (MLST), and changes in gut microbiome were tested. Results: ST04 (22.5%) and ST37 (12.7%) were the most frequent strains. Clade (phylogenetic lineage) 1 was the most (81.4%) prevalent. We found significant associations between ST and age (p = 0.024) and between ST and moxifloxacin susceptibility (p = 0.001). At the clade level, we found significant associations with binary toxin gene occurrence (p = 0.002), and with susceptibility to both metronidazole and vancomycin (p = 0.024, 0.035, respectively). Differences in intestine microbiome were affected by age, clades&rsquo; distribution and STs. Conclusions: By defining the characteristics of the different strains and clades, clinicians can choose medical interventions based on the predicted response or disease severity associated with each strain, enabling new advances in the field of personalized medicine

Characterization of Clostridioides difficile Strains, the Disease Severity, and the Microbial Changes They Induce

Background: Clostridioides difficile infection (CDI) is a major nosocomial disease. The characteristics of different strains, the disease severity they cause, their susceptibility to antibiotics, and the changes they inflict on gut microbiome, have not been comprehensively studied in Israel. Methods: A severity score was calculated for 70 patients. Stool samples were tested for toxins presence using a special kit. Bacteria were isolated, identified by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) and antibiotic susceptibility tests were performed for several antibiotics. Strains were classified by Multi-locus sequence typing (MLST), and changes in gut microbiome were tested. Results: ST04 (22.5%) and ST37 (12.7%) were the most frequent strains. Clade (phylogenetic lineage) 1 was the most (81.4%) prevalent. We found significant associations between ST and age (p = 0.024) and between ST and moxifloxacin susceptibility (p = 0.001). At the clade level, we found significant associations with binary toxin gene occurrence (p = 0.002), and with susceptibility to both metronidazole and vancomycin (p = 0.024, 0.035, respectively). Differences in intestine microbiome were affected by age, clades’ distribution and STs. Conclusions: By defining the characteristics of the different strains and clades, clinicians can choose medical interventions based on the predicted response or disease severity associated with each strain, enabling new advances in the field of personalized medicine.</jats:p