Perturbation of RNA Polymerase I transcription machinery by ablation of HEATR1 triggers the RPL5/RPL11-MDM2-p53 ribosome biogenesis stress checkpoint pathway in human cells.

Ribosome biogenesis is an energy consuming process which takes place mainly in the nucleolus. By producing ribosomes to fuel protein synthesis, it is tightly connected with cell growth and cell cycle control. Perturbation of ribosome biogenesis leads to the activation of p53 tumor suppressor protein promoting processes like cell cycle arrest, apoptosis or senescence. This ribosome biogenesis stress pathway activates p53 through sequestration of MDM2 by a subset of ribosomal proteins (RPs), thereby stabilizing p53. Here, we identify human HEATR1, as a nucleolar protein which positively regulates ribosomal RNA (rRNA) synthesis. Downregulation of HEATR1 resulted in cell cycle arrest in a manner dependent on p53. Moreover, depletion of HEATR1 also caused disruption of nucleolar structure and activated the ribosomal biogenesis stress pathway - RPL5 / RPL11 dependent stabilization and activation of p53. These findings reveal an important role for HEATR1 in ribosome biogenesis and further support the concept that perturbation of ribosome biosynthesis results in p53-dependent cell cycle checkpoint activation, with implications for human pathologies including cancer.

Incidence of fecal Enterobacteriaceae producing broad-spectrum beta-lactamases in patients with hematological malignancies.

AIM: Given the steadily increasing numbers of resistant bacteria, the frequency and severity of infections are on the rise. In patients with hematological malignancies, the treatment itself increases the risk of complicating bacterial infections. One important mechanisms of resistance is production of broad-spectrum beta-lactamases, increasingly detected not only in bacterial pathogens but also in bacteria contained in the normal microflora of the human body. The objectives of this study were determination and analysis of the prevalence of multiresistant ESBL- and AmpC-positive Enterobacteriaceae in the gastrointestinal tract (GIT) of patients with hematological malignancies. METHODS: For 3 months, rectal swabs were taken from patients with hematological malignancies and analyzed using chromogenic screening plates to isolate ESBL- and AmpC-producing Enterobacteriaceae. Beta-lactamase production was determined by phenotype tests and confirmed by detecting genes encoding ESBL and AmpC types. At the same time, ESBL- and AmpC-positive Enterobacteriaceae were isolated from clinical samples collected from patients with bacterial infection. RESULTS: Over the study period, fifteen patients (21%) of all patients treated at the Department of Hemato-Oncology were shown to have ESBL- or AmpC-positive Enterobacteriaceae in their GIT. Most frequently identified were ESBL-positive strains of Klebsiella pneumoniae and AmpC-positive strains of Citrobacter freundii. The ESBL enzymes were mainly of the CTX-M type. Isolates producing AmpC were found to contain genes for enzymes mainly from the CIT and DHA groups. CONCLUSION: The study identified patients diagnosed with urinary tract and bloodstream infections caused by ESBL-positive strain of Klebsiella pneumoniae and AmpC-positive strain of Enterobacter cloacae contained in the GIT microflora.

Acinetobacter baumannii producing OXA-23 detected in the Czech Republic.

BACKGROUND: Acinetobacter baumannii is an opportunistic pathogen posing an increased risk to hospitalized persons, causing nosocomial pneumonias, urinary tract infections and postoperative infections. METHODS: Between 1 December 2011 and 30 September 2012, strains of Acinetobacter spp. were isolated from clinical samples obtained from hospitalized patients. Susceptibility to antibiotics was determined by the standard microdilution method and phenotypic testing was used to detect the presence of serine carbapenemases and metallo-beta-lactamases. The polymerase chain reaction was used to detect the genes encoding carbapenemases. Pulsed field gel electrophoresis was used to investigate the genetic relationship among the carbapenem resistant isolates of Acinetobacter baumannii. RESULTS: In three strains of Acinetobacter baumannii enzyme OXA-23 was detected. This positive result was confirmed by restriction analysis and sequencing. The study reported an OXA-23-producing strains of Acinetobacter baumannii in the Czech Republic. All three strains isolated from Military Hospital patients had a completely identical restriction profile, indicating clonal spread of a strain carrying serine carbapenemase OXA-23 in this health care facility. Moreover this was the first time the strain was detected in the country in patients who had not stayed abroad.