Population Structure of Staphylococcus aureus from Remote African Babongo Pygmies

Staphylococcus aureus is a bacterium that colonizes humans worldwide. The anterior nares are its main ecological niche. Carriers of S. aureus are at a higher risk of developing invasive infections. Few reports indicated a different clonal structure and profile of virulence factors in S. aureus isolates from Sub-Saharan Africa. As there are no data about isolates from remote indigenous African populations, we conducted a cross-sectional survey of S. aureus nasal carriage in Gabonese Babongo Pygmies. The isolates were characterized regarding their susceptibility to antibiotic agents, possession of virulence factors and clonal lineage. While similar carriage rates were found in populations of industrialized countries, isolates that encode the genes for the Panton-Valentine leukocidin (PVL) were clearly more prevalent than in European countries. Of interest, many methicillin-susceptible S. aureus isolates from Babongo Pygmies showed the same genetic background as pandemic methicillin-resistant S. aureus (MRSA) clones. We advocate a surveillance of S. aureus in neglected African populations to control the development of resistance to antibiotic drugs with particular respect to MRSA and to assess the impact of the high prevalence of PVL-positive isolates

Genetic Pathway in Acquisition and Loss of Vancomycin Resistance in a Methicillin Resistant Staphylococcus aureus (MRSA) Strain of Clonal Type USA300

An isolate of the methicillin-resistant Staphylococcus aureus (MRSA) clone USA300 with reduced susceptibility to vancomycin (SG-R) (i.e, vancomycin-intermediate S. aureus, VISA) and its susceptible “parental” strain (SG-S) were recovered from a patient at the end and at the beginning of an unsuccessful vancomycin therapy. The VISA phenotype was unstable in vitro generating a susceptible revertant strain (SG-rev). The availability of these 3 isogenic strains allowed us to explore genetic correlates of antibiotic resistance as it emerged in vivo. Compared to the susceptible isolate, both the VISA and revertant strains carried the same point mutations in yycH, vraG, yvqF and lspA genes and a substantial deletion within an intergenic region. The revertant strain carried a single additional frameshift mutation in vraS which is part of two component regulatory system VraSR. VISA isolate SG-R showed complex alterations in phenotype: decreased susceptibility to other antibiotics, slow autolysis, abnormal cell division and increased thickness of cell wall. There was also altered expression of 239 genes including down-regulation of major virulence determinants. All phenotypic properties and gene expression profile returned to parental levels in the revertant strain. Introduction of wild type yvqF on a multicopy plasmid into the VISA strain caused loss of resistance along with loss of all the associated phenotypic changes. Introduction of the wild type vraSR into the revertant strain caused recovery of VISA type resistance. The yvqF/vraSR operon seems to function as an on/off switch: mutation in yvqF in strain SG-R turns on the vraSR system, which leads to increase in vancomycin resistance and down-regulation of virulence determinants. Mutation in vraS in the revertant strain turns off this regulatory system accompanied by loss of resistance and normal expression of virulence genes. Down-regulation of virulence genes may provide VISA strains with a “stealth” strategy to evade detection by the host immune system

Combined PARP and ATR inhibition potentiates genome instability and cell death in ATM-deficient cancer cells.

The poly (ADP-ribose) polymerase (PARP) inhibitor olaparib is FDA approved for the treatment of BRCA-mutated breast, ovarian and pancreatic cancers. Olaparib inhibits PARP1/2 enzymatic activity and traps PARP1 on DNA at single-strand breaks, leading to replication-induced DNA damage that requires BRCA1/2-dependent homologous recombination repair. Moreover, DNA damage response pathways mediated by the ataxia-telangiectasia mutated (ATM) and ataxia-telangiectasia mutated and Rad3-related (ATR) kinases are hypothesised to be important survival pathways in response to PARP-inhibitor treatment. Here, we show that olaparib combines synergistically with the ATR-inhibitor AZD6738 (ceralasertib), in vitro, leading to selective cell death in ATM-deficient cells. We observe that 24 h olaparib treatment causes cells to accumulate in G2-M of the cell cycle, however, co-administration with AZD6738 releases the olaparib-treated cells from G2 arrest. Selectively in ATM-knockout cells, we show that combined olaparib/AZD6738 treatment induces more chromosomal aberrations and achieves this at lower concentrations and earlier treatment time-points than either monotherapy. Furthermore, single-agent olaparib efficacy in vitro requires PARP inhibition throughout multiple rounds of replication. Here, we demonstrate in several ATM-deficient cell lines that the olaparib and AZD6738 combination induces cell death within 1-2 cell divisions, suggesting that combined treatment could circumvent the need for prolonged drug exposure. Finally, we demonstrate in vivo combination activity of olaparib and AZD6738 in xenograft and PDX mouse models with complete ATM loss. Collectively, these data provide a mechanistic understanding of combined PARP and ATR inhibition in ATM-deficient models, and support the clinical development of AZD6738 in combination with olaparib

Intratumoral heterogeneity of programmed cell death ligand-1 expression is common in lung cancer

Programmed cell death ligand-1 (PD-L1) expression may predict the response to both programmed cell death-1 and PD-L1 inhibitors in lung cancer. However, the extent of intratumoral heterogeneity of PD-L1 expression, which may cause false negative results, is largely unexplored. We aimed to assess the intratumoral heterogeneity of PD-L1 expression in surgically resected lung cancer specimens by applying a novel method of tissue microarray, namely Spiral Arrays, which enables us to observe the heterogeneity in spiral-shaped tissue cores. Adenocarcinoma and squamous cell carcinoma specimens were obtained from consecutive patients with lung cancer who had undergone surgical resection at Nagasaki University Hospital (Nagasaki, Japan) since 2009. Small cell lung cancer and large cell carcinoma specimens were selected from patients in the same archive who had undergone resection since 1998. Spiral Arrays were constructed of spiral-shaped cores, prepared from representative blocks of each case, which were subjected to immunohistochemistry using an anti-PD-L1 antibody. Each core was divided into 8 segments and each segment was classified as either PD-L1-positive or PD-L1-negative using thresholds of 1.0%, 5.0%, 10.0%, and 50.0%, respectively. In total, 138 specimens were selected, including 60 adenocarcinomas, 59 squamous cell carcinomas, 12 small cell lung cancers, and 7 large cell carcinomas. The majority of specimens with PD-L1-positive segments exhibited heterogeneous expression (i.e., had a mixture of PD-L1-positive and PD-L1-negative segments within a core) irrespective of the threshold (1.0%, 66.7%; 5.0%, 74.4%; 10.0%, 75.8%; and 50.0%, 85.7%]. Large variations in the ratios of PD-L1-positive segments were observed. At least 50.0% of the segments within a core were negative in no fewer than 50.0% (range, 50.0?76.0%) of cases with heterogeneous PD-L1 expression. In conclusion, intratumoral heterogeneity of PD-L1 expression was frequently observed in cases of lung cancer. Thus, multiple tumor biopsy specimens may be needed to accurately determine the PD-L1 expression status

Teaching situation and instructors’ key-competencies at the college of maritime education (CME): evaluation of the marine engineering students

Strength of educational system depends upon the quality pf teachers. Teachers have always been considered as one of the noblest professions. (Naz, 2016). Students are generally influenced by their teachers because they spend most of their time at school (Rahaman, 2010; Rosen, 2010). To teach students according to today’s standards, teachers need to understand subject matter deeply and flexibly so that they can help students create useful cognitive maps, relate one idea to another, and address misconceptions. Teachers need to see how ideas connect across fields and to everyday life. Teachers use suitable strategies and resources to follow instructions according to the needs of the needs of individuals and groups of students. Teachers should guide pupils learning in analyzing. Teachers should provide manifold models and explanations of concepts behaviors and skills. Teachers provide creative and critical thinking, problem solving ability, curiosity. They should know how to use various technological and communication. They should believe in change and flexibility in teaching learning process (Rahaman, 2010; Rosen, 2010)