Evaluation of Structural Changes and Molecular Mechanism Induced by High Hydrostatic Pressure in Enterobacter sakazakii

The contamination of infant milk and powder with Enterobacter sakazakii poses a risk to human health and frequently caused recalls of affected products. This study aims to explore the inactivation mechanism of E. sakazakii induced by high hydrostatic pressure (HHP), which, unlike conventional heat treatment, is a nonthermal technique for pasteurization and sterilization of dairy food without deleterious effects. The mortality of E. sakazakii under minimum reaction conditions (50 MPa) was 1.42%, which was increased to 33.12% under significant reaction conditions (400 MPa). Scanning electron microscopy (SEM) and fluorescent staining results showed that 400 MPa led to a loss of physical integrity of cell membranes as manifested by more intracellular leakage of nucleic acid, intracellular protein and K+. Real-time quantitative PCR (RT-qPCR) analysis presents a downregulation of three functional genes (glpK, pbpC, and ompR), which were involved in cell membrane formation, indicating a lower level of glycerol utilization, outer membrane protein assembly, and environmental tolerance. In addition, the exposure of E. sakazakii to HHP modified oxidative stress, as reflected by the high activity of catalase and super oxide dismutase. The HHP treatment lowered down the gene expression of flagellar proteins (fliC, flgI, fliH, and flgK) and inhibited biofilm formation. These results determined the association of genotype to phenotype in E. sakazakii induced by HHP, which was used for the control of food-borne pathogens.

Outbreak of OXA-48-producing Enterobacterales in a haematological ward associated with an uncommon environmental reservoir, France, 2016 to 2019

The hospital water environment, including the wastewater drainage system, is increasingly reported as a potential reservoir for carbapenemase-producing Enterobacterales (CPE). We investigated a persistent outbreak of OXA-48 CPE (primarily Citrobacter freundii) in a haematological ward of a French teaching hospital by epidemiological, microbiological and environmental methods. Between January 2016 and June 2019, we detected 37 new OXA-48 CPE-colonised and/or ‑infected patients in the haematological ward. In October 2017, a unit dedicated to CPE-colonised and/or ‑infected patients was created. Eleven additional sporadic acquisitions were identified after this date without any obvious epidemiological link between patients, except in one case. Environmental investigations of the haematological ward (June–August 2018) identified seven of 74 toilets and one of 39 drains positive for OXA-48 CPE (seven C. freundii, one Enterobacter sakazakii, one Escherichia coli). Whole genome comparisons identified a clonal dissemination of OXA-48-producing C. freundii from the hospital environment to patients. In addition to strict routine infection control measures, an intensive cleaning programme was performed (descaling and bleaching) and all toilet bowls and tanks were changed. These additional measures helped to contain the outbreak. This study highlights that toilets can be a possible source of transmission of OXA-48 CPE.

Microbiological and cytological characterization of coelomic fluid from three captive endangered amphibian Gastrotheca species with edema syndrome: preliminary analysis

Objective Edema syndrome is highly prevalent but under researched in captive frogs around the world. The objective of the present study was to characterize at a basic microbiological and cytological level of the bacteria of the edema fluid of 20 individuals of the genus Gastrotheca to determine the presence of possible anaerobic and aerobic bacteria. Results Fourteen types of bacteria were identified in the edema fluid, 12 of them at the species level (Pasteurella haemolytica, Hafnia alvei, Enterobacter agglomerans, Aeromonas hydrophila, Pseudomonas fluorescens, Burkholderia pseudomallei, Salmonella arizonae, Enterobacter gergoviae, Enterobacter sakazakii, Yersinia enterocolitica, Klebsiella oxytoca, and Klebsiella ozaenae) and two at the genus level (Enterococcus spp. and Streptococcus spp.). The most frequently identified cells were lymphocytes (37.7% in females and 46.4% in males), erythrocytes (23.5% in females and 17.5% in males) and neutrophils (4.2% in females and 2.8% in males). Finally, no relationship was found between the data obtained and the sex of the individuals studied.