Characterization of antibiotic resistance and host-microbiome interactions in the human upper respiratory tract during influenza infection

BACKGROUND

The abundance and diversity of antibiotic resistance genes (ARGs) in the human respiratory microbiome remain poorly characterized. In the context of influenza virus infection, interactions between the virus, the host, and resident bacteria with pathogenic potential are known to complicate and worsen disease, resulting in coinfection and increased morbidity and mortality of infected individuals. When pathogenic bacteria acquire antibiotic resistance, they are more difficult to treat and of global health concern. Characterization of ARG expression in the upper respiratory tract could help better understand the role antibiotic resistance plays in the pathogenesis of influenza-associated bacterial secondary infection.

RESULTS

Thirty-seven individuals participating in the Household Influenza Transmission Study (HITS) in Managua, Nicaragua, were selected for this study. We performed metatranscriptomics and 16S rRNA gene sequencing analyses on nasal and throat swab samples, and host transcriptome profiling on blood samples. Individuals clustered into two groups based on their microbial gene expression profiles, with several microbial pathways enriched with genes differentially expressed between groups. We also analyzed antibiotic resistance gene expression and determined that approximately 25% of the sequence reads that corresponded to antibiotic resistance genes mapped to Streptococcus pneumoniae and Staphylococcus aureus. Following construction of an integrated network of ARG expression with host gene co-expression, we identified several host key regulators involved in the host response to influenza virus and bacterial infections, and host gene pathways associated with specific antibiotic resistance genes.

CONCLUSIONS

This study indicates the host response to influenza infection could indirectly affect antibiotic resistance gene expression in the respiratory tract by impacting the microbial community structure and overall microbial gene expression. Interactions between the host systemic responses to influenza infection and antibiotic resistance gene expression highlight the importance of viral-bacterial co-infection in acute respiratory infections like influenza. Video abstract.

Effects of long-term in vitro incubation of human spermatozoa: functional parameters and catalase effect

Prolonged incubation of human spermatozoa can have deleterious effects on sperm function. The aim of this paper was to describe the effects of a prolonged in vitro incubation, under similar conditions to those employed in human assisted reproduction, on various sperm functional parameters, and to investigate the effect of an antioxidant (catalase) on this system. Freshly collected ejaculates from 20 healthy donors were studied. Samples were divided into two aliquots: the first was incubated with Ham's F10 containing 3.5% HAS, and the second was incubated in the same medium plus catalase (100 units ml-1). All experiments were carried out with spermatozoa isolated using the swim-up technique. Spermatozoa recovered from the supernatant after 1 h (T1) of incubation in 5% CO2 in air at 37 degrees C, and after 5 h (T6), 23 h (T24) and 47 h (T48), were evaluated for concentration, motion parameters including hyperactivation (computer-assisted analysis), viability, ATP concentration, reactive oxygen species (ROS) generation, DNA integrity (acridine orange), and acrosome reaction (AR). The major alteration observed in sperm function during the prolonged in vitro incubation was a reduction in the number of motile spermatozoa, together with an impairment in the quality of sperm movement. ROS levels increased with the incubation time. No substantial modifications of sperm viability, chromatin condensation and AR inducibility were observed. The addition of catalase to the medium, while keeping ROS values within baseline levels, did not prevent the loss of motility or the corresponding increase in ATP.

Observations on the development of unusual melanization of leopard frog ventral skin

The ontogeny of ventral pigmentation of two species of leopard frog, Rana pipiens and R. chiricahuensis, was examined by light microscopy and transmission electron microscopy to reveal how the unusual melanistic ventral pigmentation of R. chiricahuensis is achieved at the cellular level. Ventral skin of R. pipiens is always white. Ventral skin of adult R. chiricahuensis is white when frogs are background-adapted to a white substrate, but ventral skin becomes nearly as dark colored as the dorsal skin when frogs darken in response to a black background. Skin samples from tadpoles of both species, newly metamorphosed frogs, and adult frogs were analyzed for chromatophore composition and distribution. Ventral skin of R. pipiens larvae, newly metamorphosed frogs, and adults and of R. chiricahuensis larvae was white due to abundant iridophores and no melanophores. Melanophore density in the ventral integument of R. chiricahuensis was 9.1 +/- 2.8/mm2 in newly metamorphosed frogs and 87.0 +/- 4.8/mm2 in adult frogs. Pigment within ventral melanophores migrated during physiological color change during background adaptation.

Effect of background color and low temperature on skin color and circulating alpha-MSH in two species of leopard frog

Circulating levels of alpha-melanocyte stimulating hormone (alpha-MSH) in two species of leopard frog, Rana pipiens and R. chiricahuensis, were measured by radioimmunoassay to reveal the correlation between skin color change induced by background color and by low temperature. High levels of alpha-MSH were found in both species of frog on a black background, but R. chiricahuensis had eight times higher levels than R. pipiens, R. chiricahuensis also exhibited the ability to darken its ventral surface, whereas the ventral surface of R. pipiens remained white. Neither skin color nor plasma alpha-MSH of R. pipiens was affected by cold. Low temperature did, however, darken dorsal and ventral skin of R. chiricahuensis in vivo, which corresponded to increased levels of plasma alpha-MSH. Dorsal and ventral skin of R. chiricahuensis, in vitro, darken in a dose-dependent manner to alpha-MSH, but not to cold.