No abstract

An assay based on the utilization of degenerate primers that enable enzymatic amplification of an internal fragment of cat genes known to be present in gram-positive cocci was developed to identify the genes encoding chloramphenicol resistance in streptococci and enterococci. The functionality of this system was illustrated by the detection of cat genes belonging to four different hydridization classes represented by the staphylococcal genes catpC221, catpC1949 catpSCS79 and the clostridial gene catP, and by the characterization of a new streptococcal cat gene designated catS. A sequence related to the clostridial catQ gene, which was present in one streptococcal strain, was not detected by this assay. These results reveal that these six cat genes account for chromosomal-borne chloramphenicol resistance in 12 group A, B, and G streptococci tested. By contrast, only three of these six cat genes (catp'221, catj%94 and catpsCS7) were detected on the 10 enterococcal plasmids studied here that encode resistance to chloramphenicol.Chloramphenicol resistance (Cmr) in bacteria of clinical importance is generally due to the synthesis of the enzyme chloramphenicol acetyltransferase (CAT) which inactivates the antibiotic by converting it successively to 3-acetyl and 1,3-diacetyl derivatives (31). Comparison of the amino acid sequences of 17 CAT proteins from gram-negative and gram-positive bacteria has revealed a significant degree of homology between the various enzymes, and their phylogenetic relationship has been established (2, 18, 29). Nucleotide sequences are now available for 13 cat genes originating in gram-positive bacteria. These are the gene cat-86 from Bacillus pumilus (10); those carried by the staphylococcal plasmids pC194 (11), pC221 (32), pSCS1 (30), pSCS5 (28), pSCS6 (7), pSCS7 (29), and pUB112 (5) and by the streptococcal plasmid pIP501 (12,35) Utilization of degenerate primers in polymerase chain reaction (PCR) enables the detection of rRNA methylase genes that confer resistance to macrolide-lincosamide-streptogramin B-type (MLS) antibiotics in gram-positive bacteria (1). We have developed a similar assay in order to characterize the cat genes present in the remaining seven plasmidfree streptococci (23) and in the three Enterococcus faecalis plasmids (26) which did not detectably hybridize with catp.221 (or catpIP501) and cat C194* In addition, one E. faecalis and six Enterococcus [aecium plasmids coding for Cmr were included in this study. MATERIALS AND METHODSBacterial strains and culture conditions. The main characteristics of the strains and plasmids used in this study which carried unidentified cat genes are listed in Table 1

No abstract

Although COVID-19 vaccines have recently been approved for emergency use, search for new vaccines are still urgent, since the access of the countries, especially the poorest, to the vaccines, has shown to be slower than the necessary to rapidly control the pandemic. We proposed a novel platform for vaccine using recombinant receptor binding domain (rRBD) from Sars-Cov-2 spike protein and Neisseria meningitidis outer membrane vesicles (OMVs). The antigen preparation produced a humoral and cellular immune response. Taken together our findings suggest a good immunostimulatory patter in response to immunization with rRBD plus N. meningitidis OMV.

No abstract

The experimental system of Taenia crassiceps cysticerci infection in BALB/c mice is considered to be the most representative model of cysticercosis. In our work, mice were sacrificed 7 and 30days after infection, and pouch fluid was collected to determine the number of accumulated cells and the concentrations of IFNγ, IL-2, IL-4, IL-6, IL-10 and nitric oxide. The injection of 50 nonbudding cysticerci into normal mouse dorsal air pouches induced a high level of IFNγ and nitric oxide production relative to the parasite load. The air pouch provides a convenient cavity that allows studying the cellular immunological aspects of the T. crassiceps parasite. The nonbudding cysticerci recovered from the air pouches contained cells that can reconstitute complete cysts in the peritoneal cavity of mice. In conclusion, these results demonstrate that the air pouch model is an alternative tool for the evaluation of the immune characteristics of T. crassiceps infection.

No abstract

Abstract The elderly are more likely to die when infected with Neisseria meningitidis. Aging is associated with immune system dysfunctions that impair responses to vaccines and infections. Therefore, immunization of middle-aged individuals could be beneficial. This study aims to evaluate the immunogenicity of N. meningitidis B outer membrane vesicles (OMVs) complexed to two different adjuvants. Middle-aged BALB/c and A/Sn mice were immunized and subsequent immune response was assessed by ELISA, immunoblotting, and ELISpot. IgG levels were similar between the animals immunized with OMVs complexed to adjuvants. 235 days after the last immunization only A/Sn mice presented higher IgG levels than those observed in the baseline, especially the group immunized with OMVs and aluminum hydroxide. The predominant IgG subclasses were IgG2a and IgG2b. Immunization with the three-dose regimen generated IgG antibodies that recognized a variety of antigens present in the homologous and heterologous meningococcal OMVs evaluated. There was an increase in the frequency of antigen-specific IFN-γ secreting splenocytes, after in vitro stimulation, in mice immunized with OMVs and adjuvants compared to the control group, almost one year after the last immunization. Both adjuvants showed similar performance. Immunization of middle-aged mice has generated a robust immune response and it appears to be advantageous.