Establishment and evaluation of a BALBc mouse model of Burkholderia pseudomallei via nasal infection / 中国热带医学

@#Abstract: Objective To establish an animal model of BALB/c mice infected with Burkholderia pseudomallei through the nose (inhalation route), provides a reliable animal model for the follow-up studies on the virulence of melioidosis and the pathogenesis of acute melioidosis. Methods　The experiment was carried out through infecting with Burkholderia pseudomallei through the nose (inhalation route). The pathophysiological response, visceral pathological damage and bacterial colonization of the mice infected with Burkholderia pseudomallei were observed by gross anatomy, histopathology and tissue homogenate count, and the biological characteristics of the mouse model of acute melioidosis were analyzed accordingly. Then we compared the physiological responses in BALB/c mice between the Burkholderia pseudomallei and non-pathogenic Burkholderia thailandensis. Results　In the model of acute nasal infection with Burkholderia thailandensis, most death happened between the 3rd to 5th day after infection, 3×105-3×106 CFU was the suitable dose for acute fatal melioidosis model of BALB/c mice, and the medium lethal dose was about 3×104-3×105 CFU. Both gross anatomy and tissue HE staining showed that abscesses or necrosis were found in the lung, spleen and liver, especially in the spleen and lung, which was positively correlated with the challenge dose. Viable bacteria was isolated from the blood, lung, spleen and liver of Burkholderia pseudomallei-infected mice, and the bacteria account colonization was related to tissue specificity. The concentration of live bacteria isolated from in the blood was the highest [Log2 value: (10.28±0.34) CFU/mL], and the organ with the maximum quantity of bacteria was the lung [Log2 value: (7.54±2.11) CFU/total organ]. It has been reported that the biological effects of Burkholderia pseudomallei and its homologous non-pathogenic Burkholderia thailandensis were similar at the cellular level, like multi-nuclear giant cell formation and active intracellular replication, while it is still unclarrified in the differences of virulence in mice. In this study, it was proved that Burkholderia thailandensis was not fatal to mice even at a high dose (8×107CFU), or detected from mice infected with it via nasal. Conclusion　We successfully established a reliable BALB/c mouse model (acute lethal model) of melioidosis via nasal infection, described its biological characteristics, and identified the different biological responses between Burkholderia pseudomallei and its homologous non-pathogenic Burkholderia thailandensis in mice.

The prevalence of aminoglycoside-modifying enzyme and virulence genes among enterococci with high-level aminoglycoside resistance in Inner Mongolia, China

ABSTRACT This study highlights the prevalence of aminoglycoside-modifying enzyme genes and virulence determinants among clinical enterococci with high-level aminoglycoside resistance in Inner Mongolia, China. Screening for high-level aminoglycoside resistance against 117 enterococcal clinical isolates was performed using the agar-screening method. Out of the 117 enterococcal isolates, 46 were selected for further detection and determination of the distribution of aminoglycoside-modifying enzyme-encoding genes and virulence determinants using polymerase chain reaction -based methods. Enterococcus faecium and Enterococcus faecalis were identified as the species of greatest clinical importance. The aac(6')-Ie-aph(2")-Ia and ant(6')-Ia genes were found to be the most common aminoglycoside-modifying enzyme genes among high-level gentamicin resistance and high-level streptomycin resistance isolates, respectively. Moreover, gelE was the most common virulence gene among high-level aminoglycoside resistance isolates. Compared to Enterococcus faecium, Enterococcus faecalis harbored multiple virulence determinants. The results further indicated no correlation between aminoglycoside-modifying enzyme gene profiles and the distribution of virulence genes among the enterococcal isolates with high-level gentamicin resistance or high-level streptomycin resistance evaluated in our study.

Antennal sensilla of grasshoppers (Orthoptera: Acrididae) in relation to food preferences and habits.

The external structure, i.e. number and distribution of sensillae on male and female antennae of 12 species of grasshoppers belonging to Pamphaginae, Catantopinae, Oedipodinae and Gomphocerinae in the grasslands of Inner Mongolia was investigated using scanning electron microscopy. Five major types of antennal sensillae were detected--trichoid, long basiconic, short basiconic, slender and short basiconic, and coeloconic sensillae. Total number of antennal sensillae varied among different sexes, subfamilies, feeding groups, life forms and eco-forms. Males showed significantly more sensillae than females, due to presence of more short basiconic and coeloconic sensillae. Species under Catantopinae showed more long basiconic sensillae than the others. The Oedipodinae had the highest number of slender and short basiconic sensillae and coeloconic sensillae, followed by Catantopinae and Gomphocerinae; while Pamphaginae had the fewest. The total number of sensillae showed the same trend for these two types amongst the subfamilies as well, species which prefer habits on the ground possessed fewer antennal sensillae than species which prefer to stay on plants. The maximal number of antennal sensillae were observed in hygrophytous species, Chorthippus albomarginatus, in the 12 grasshopper species investigated, although the data is not statistically significant. The general trend which emerged was that species feeding on grass possessed more antennal sensillae, particularly coeloconic sensillae, compared to other feeding group species.