High risk of intestinal colonization with ESBL-producing Escherichia coli among soldiers of military contingents in specific geographic regions

One-hundred Polish soldiers of a contingent in Afghanistan in 2019 were screened for Enterobacterales resistant to newer-generation β-lactams at their departure and return. Seventeen percent were colonized in the gut at the departure, whereas 70% acquired carriage in Afghanistan. The commonest organisms were extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (ESBL-Ec; 96.6%). All isolates were sequenced and were clonally diverse overall, even within the same sequence type, indicating that independent acquisitions mainly. ESBL-Ec were often multi-drug-resistant. Soldiers stationing in certain regions are at high risk of acquiring resistant bacteria that may cause endogenous infection, be transmitted to vulnerable individuals, and spread resistance genes.

Effect of inbreeding and heritability of sperm competition success in the bulb mite Rhizoglyphus robini

Sperm competition is a potent evolutionary force shaping the reproductive biology of most animal species. Here, we estimated the heritability of sperm competition success in the promiscuous bulb mite Rhizoglyphus robini. Sperm competition success was measured with the sterile male technique as the proportion of eggs fertilised by the second of three males mated with a single female. Sperm competition success responded significantly to selection. The heritability estimated from the response to five generations of selection was 0.13. We also estimated the effect of inbreeding on sperm competition success. Males produced by sib-mating (F=0.25) had a significantly lower sperm competition success than outbred males. The estimated coefficient of inbreeding depression was 0.53. Such high inbreeding depression together with moderately low heritability is consistent with the view that sperm competitive ability is under strong directional selection and strongly influences the reproductive success of males.

Polyandry increases offspring fecundity in the bulb mite

The common occurrence of polyandry continues to puzzle evolutionary biologists, as female reproductive success is thought to be limited mostly by her fecundity. Here we test whether females of the bulb mite, a species in which the females are highly promiscuous, benefit from polyandry in terms of increased fitness of their progeny. Females were given opportunity to mate with either one or six males, but the experiment was designed to allow the same number of matings per female in both groups, that is, irrespective of the number of males. We found that daughters of females mated to six males had significantly higher fecundity than daughters of females mated to one male, whereas other fitness components of progeny (male virility and longevity of both sexes) were not affected. These findings appear to support hypotheses proposing that multi-male mating enables females to exercise postcopulatory mate-choice (direct or indirect, via sperm competition) and thus accrue genetic benefits.