Characterization of Contaminants from a Sanitized Milk Processing Plant

Milk processing lines offer a wide variety of microenvironments where a diversity of microorganisms can proliferate. We sampled crevices and junctions where, due to deficient reach by typical sanitizing procedures, bacteria can survive and establish biofilms. The sampling sites were the holding cell, cold storage tank, pasteurizer and storage tank - transfer pump junction. The culturable bacteria that were isolated after the sanitation procedure were predominantly Pseudomonas spp., Serratia spp, Staphylococcus sciuri and Stenotrophomonas maltophilia. We assayed several phenotypic characteristics such as the ability to secrete enzymes and siderophores, as well as the capacity of the strains to form biofilms that might contribute to their survival in a mixed species environment. The Pseudomonas spp. isolates were found to either produce proteases or lecithinases at high levels. Interestingly, protease production showed an inverse correlation with siderophore production. Furthermore, all of the Serratia spp. isolates were strong biofilm formers and spoilage enzymes producers. The organisms identified were not mere contaminants, but also producers of proteins with the potential to lower the quality and shelf-life of milk. In addition, we found that a considerable number of the Serratia and Pseudomonas spp. isolated from the pasteurizer were capable of secreting compounds with antimicrobial properties

A scoping review establishes need for consensus guidance on reporting health equity in observational studies.

To evaluate the support from the available guidance on reporting of health equity in research for our candidate items and to identify additional items for the Strengthening Reporting of Observational studies in Epidemiology-Equity extension. We conducted a scoping review by searching Embase, MEDLINE, CINAHL, Cochrane Methodology Register, LILACS, and Caribbean Center on Health Sciences Information up to January 2022. We also searched reference lists and gray literature for additional resources. We included guidance and assessments (hereafter termed "resources") related to conduct and/or reporting for any type of health research with or about people experiencing health inequity. We included 34 resources, which supported one or more candidate items or contributed to new items about health equity reporting in observational research. Each candidate item was supported by a median of six (range: 1-15) resources. In addition, 12 resources suggested 13 new items, such as "report the background of investigators". Existing resources for reporting health equity in observational studies aligned with our interim checklist of candidate items. We also identified additional items that will be considered in the development of a consensus-based and evidence-based guideline for reporting health equity in observational studies

A Strand Invasion 3′ Polymerization Intermediate of Mammalian Homologous Recombination

Initial events in double-strand break repair by homologous recombination in vivo involve homology searching, 3′ strand invasion, and new DNA synthesis. While studies in yeast have contributed much to our knowledge of these processes, in comparison, little is known of the early events in the integrated mammalian system. In this study, a sensitive PCR procedure was developed to detect the new DNA synthesis that accompanies mammalian homologous recombination. The test system exploits a well-characterized gene targeting assay in which the transfected vector bears a gap in the region of homology to the single-copy chromosomal immunoglobulin μ heavy chain gene in mouse hybridoma cells. New DNA synthesis primed by invading 3′ vector ends copies chromosomal μ-gene template sequences excluded by the vector-borne double-stranded gap. Following electroporation, specific 3′ extension products from each vector end are detected with rapid kinetics: they appear after 0.5 hr, peak at 3–6 hr, and then decline, likely as a result of the combined effects of susceptibility to degradation and cell division. New DNA synthesis from each vector 3′ end extends at least ∼1000 nucleotides into the gapped region, but the efficiency declines markedly within the first ∼200 nucleotides. Over this short distance, an average frequency of 3′ extension for the two invading vector ends is ∼0.007 events/vector backbone. DNA sequencing reveals precise copying of the cognate chromosomal μ-gene template. In unsynchronized cells, 3′ extension is sensitive to aphidicolin supporting involvement of a replicative polymerase. Analysis suggests that the vast majority of 3′ extensions reside on linear plasmid molecules