Isolation and characterization of a <i>Chlamydia muridarum tc0237</i> mutant from a genetic screen that is attenuated in epithelial cells

by Kaylee R. Jacobs, Caleb M. Ardizzone, Arkaprabha Banerjee, Evelyn Toh, Xiaoli Zhang, David E. Nelson

Chlamydia are obligate intracellular bacterial pathogens that infect a wide range of vertebrate hosts. Despite having highly conserved genomes, closely related Chlamydia species can exhibit distinct host and tissue tropisms. The host tropisms of the human pathogen Chlamydia trachomatis and the closely related mouse pathogen Chlamydia muridarum are influenced by their ability to evade host immune responses, particularly those mediated by interferon gamma. However, there is evidence that tissue tropism is driven by additional poorly understood host and Chlamydia factors. In this study, we used a forward genetic approach to investigate the mechanisms that mediate C. muridarum tissue tropism. We conducted a tropism screen using a randomly mutagenized C. muridarum library and murine cell lines representing different tissues. We identified a mutant isolate whose growth was restricted in murine rectal and oviduct epithelial cells in an interferon gamma-independent manner. This phenotype was mapped to a missense mutation in tc0237, a gene that mediates the affinity of C. muridarum for cultured human epithelial cells. Our analysis of growth dynamics showed that the tc0237 mutant exhibits a developmental delay in rectal epithelial cells. Together, these results suggest that TC0237 plays a role in C. muridarum tissue tropism.

Testing learning as alternative to the blank slate hypothesis in the honey bee, <i>Apis mellifera</i>

by Olav Rueppell, Kayla De Jong, Jacob J. Herman, Cleo Randall

Reliable recognition of nestmates and discrimination against non-nestmates is key to the integrity of social insect colonies. Cuticular hydrocarbon profiles play a key role in this recognition process in many species, including honey bees. Newly emerged worker bees are largely devoid of cuticular hydrocarbons and therefore believed to represent a “blank slate” that is not discriminated against and instead accepted into other colonies regardless of colony origin. However, instead of being unrecognizable, the absence of cuticular hydrocarbons may also represent a recognizable “Gestalt”. Thus, an alternative hypothesis for the universal acceptance of newly emerged workers may be that older workers in every colony learn the absence of cuticular hydrocarbons as a familiar stimulus that belongs to their colony because other such workers are constantly emerging under normal circumstances. Here, we tested this hypothesis by comparing the response to newly emerged workers between bees that matured in colonies with and without newly emerging bees. Contrary to our prediction, we found no significant difference between these two experimental groups in an aggression bioassay towards newly emerged workers. We thus failed to provide empirical evidence against the blank slate hypothesis. However, the groups displayed significant differences in aggression towards foragers from their own respective colonies, indicating that the emergence of new workers in a colony can affect group discriminatory behavior in honey bees. Furthermore, we identified a negative effect of temperature on aggressive behavior toward newly emerged workers.

Antibiotic prescription patterns and associated symptoms in children living with HIV at Arthur Davison Children’s Hospital in Ndola, Zambia

by Jonathan Gwasupika, Davidson H. Hamer, Victor Daka, Ephraim Chikwanda, David Mwakazanga, Ruth L. Mfune, Choolwe Jacobs

Background

Children with human immunodeficiency virus (HIV) infection are disproportionately susceptible to bacterial infections. There are a wide range of antibacterial agents available to manage HIV positive children with bacterial infections. However, administration of antibiotics in most children is empirical which could lead to antimicrobial resistance.

Objectives

This study aimed to determine commonly prescribed antibiotics and associated symptoms in children at Arthur Davison children’s hospital antiretroviral therapy clinic in Ndola, Zambia.

Methods

This was a cross-sectional study that analysed the antibiotic prescribing patterns from routinely collected secondary data at Arthur Davison children’s hospital. Children diagnosed with HIV before the age of 5, actively attending antiretroviral therapy clinic identified by SmartCare software and who had taken antiretroviral therapy for at least 6 months were eligible. Data were collected from files of children who met the eligibility criteria. STATA software version 16 SE (STATA Corp., College Station, Texas, USA) was used for analysis. A p-value less than 0.05 was considered statistically significant at a confidence interval of 95%.

Results

From a total of 132 children included in the study, 37.9% presented with symptoms with the most common symptoms being cough (70.0%) and diarrhoea (30.0%). A larger proportion of children (62.1%) were on arbacavir/lamivudine/dolutogravr combination of antiretroviral therapy while 8.2% were on the tenoforvir alafenamide/lamivudine/dolutobravir regimen. Children who were on abacavir/lamivudine/dolutegravir regimen presented with more symptoms (48.8%) compared to those on tenofovir alafenamide/lamivudine/dolutegravir (21.0%) and tenofovir disoproxil fumarate/lamivudine/dolutegravir (18.2%) (p = 0.006). Approximately 60.0% of children presenting with symptoms were prescribed antibiotics. Co-trimoxazole was the most commonly (38.0%) prescribed, while erythromycin (2.0%) and Cephalexin (2.0%) were the least.

Conclusions

Respiratory and gastrointestinal symptoms were the most common presentations suggestive of a suspected infection requiring antibiotic prescription in HIV-positive children on ART. Despite co-trimoxazole being the prophylactic drug among HIV-positive children, it was the most common antibiotic among children presenting with symptoms suggestive of an infection. This calls for the prudent use of co-trimoxazole to avoid its resistance.

Sex differences persist in visuospatial mental rotation under 3D VR conditions

by Oliver L. Jacobs, Katerina Andrinopoulos, Jennifer K. E. Steeves, Alan Kingstone

The classic Vandenberg and Kuse Mental Rotations Test (MRT) shows a male advantage for visuospatial rotation. However, MRTs that have been adapted for use with real or physical objects have found that sex differences are reduced or abolished. Previous work has also suggested that virtual 3D objects will eliminate sex differences, although this has not been demonstrated in a purely visuospatial paradigm without motor input. In the present study we sought to examine potential sex differences in mental rotation using a fully-immersive 3D VR adaptation of the original MRT that is purely visuospatial in nature. With unlimited time 23 females and 23 males completed a VR MRT designed to approximate the original Vandenberg and Kuse stimuli. Despite the immersive VR experience and lack of time pressure, we found a large male performance advantage in response accuracy, exceeding what has typically been reported for 2D MRTs. No sex differences were observed in response time. Thus, a male advantage in pure mental rotation for 2D stimuli can extend to 3D objects in VR, even when there are no time constraints.