Rotavirus NSP486-175 interacts with H9c2(2-1) cells in vitro, elevates intracellular Ca2+ levels and can become cytotoxic: a possible mechanism for extra-intestinal pathogenesis.

Rotavirus (RV) is the predominant cause of infantile gastroenteritis with multiple pathogenic factors, among which enterotoxin NSP4 is the most significant factor. NSP4 has been shown to induce elevation of the intracellular calcium concentration, alteration of the cytoskeleton organization, and cytopathic effect among other processes. However, increasing evidence suggests that RVs can escape from the gastrointestinal tract and invade other organs and tissues to cause extra-intestinal diseases. In this study, we investigated whether NSP4 has a pathogenic effect on extra-intestinal cells and examined possible molecular mechanisms in vitro. Our results showed that NSP486-175 has important functions in increasing intracellular Ca2+ concentration, altering actin cytoskeleton organization and inducing cellular damage in H9c2(2-1) cells. Blockade of the integrin α2 receptor using a specific antibody attenuated the increase of intracellular Ca2+ concentration and alleviated the observed cytopathic effects, suggesting that integrin α2 may be a receptor for NSP486-175. Collectively, these results indicate that extracellular NSP486-175 can induce elevation of the intracellular Ca2+ concentration, cause cytotoxic changes, and disrupt the actin cytoskeleton in H9c2(2-1) cells, which may constitute a possible mechanism for RV extra-intestinal pathogenesis.

Microbiological and Clinical Characteristics of Klebsiella pneumoniae Isolates of K57 Capsular Serotype in China.

Background: K57 Klebsiella pneumoniae (K57-KP) is associated with hypervirulence, but the basis and systematic data of K57-KP are limited. Materials and Methods: A retrospective study was conducted in 156 patients between January 2013 and January 2016. The clinical and molecular data, including antimicrobial susceptibility testing, multilocus sequence typing, antimicrobial resistance genes, and virulence determinants were assessed. Results: Among the 39 K57-KP isolates, 14 isolates (35.9%) were associated with various types of invasive infections. Diabetes, drainage, use of carbapenems and quinolone antibiotics were dependent risk factors for K57-KP infections. Sequence type (ST)412 was the most prevalent among K57-KP isolates. K57-KP isolates were more resistant to clinically often used antimicrobial agents than hvKP (K1/K2) strains, and 12.8% (5/39) of the strains were resistant to carbapenems, which all harbored blaKPC-2. The prevalence of hypermucoviscosity phenotype, aerobactin, rmpA, rmpA2, and ybts revealed 66.7%, 100%, 89.7%, 89.7%, and 30.8%, whereas wcaG, allS, magA and kfu revealed 0%, 0%, 0%, and 5.1%, which were significantly lower than that of hvKP (K1/K2). The serum sensitivity, neutrophil phagocytic rate, and biofilm formation capacity of K57-KP strains were higher than that of K1/K2. Conclusion: There were no significant differences in the prevalence of hypermucoviscosity phenotype, carriage of rmpA and aerobactin genes between K57 and K1/K2 isolates, but the composition and production of capsule polysaccharide of K57-KP may be different from that of K1/K2 strains. K57-KP isolates exhibited distinctive virulence-associated traits, most of which belonged to ST412. Physicians should enhance the management of K57-KP infections because of the emergence of more and more carbapenem-resistant K57-KP isolates.

Regulation of gene expression of hcp, a core gene of the type VI secretion system in Acinetobacter baumannii causing respiratory tract infection.

Purpose. The objective of the current study was to investigate whether hcp plays a role in the process of Acinetobacter baumannii infection and to examine clinically relevant factors that may affect hcp expression.Methodology. Seventy-seven A. baumannii isolates from patients with a respiratory infection at the Second Affiliated Hospital and Yuying Childrens Hospital of Wenzhou Medical University (Wenzhou, China) were included in this study. PCR was performed to screen for the presence of hcp. Quantitative real time polymerase chain reaction (qRT-PCR) was carried out to examine the expression of hcp.Results. A total of 77.9 % (60 of 77) of the A. baumannii clinical isolates possessed the hcp gene. Expression of hcp was found to be strain-specific and associated with the infection status. Higher gene expression of hcp was found for invasive A. baumannii isolates causing an infection relative to the colonization group, and for the same strain at a post-infection status compared with that prior to infection. Acid environment was also found to be a trigger of hcp gene expression.Conclusion. The type VI secretion system and hcp predominate in A. baumannii causing respiratory infections. Expression of hcp is regulated by the infection status and acid environment, and might play a role in the process of triggering infection by the colonizer.