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The emergence of multidrug resistance poses a huge risk to public health globally. Yet these recalcitrant pathogens continue to rise in incidence rate with resistance rates significantly outpacing the speed of antibiotic development. This therefore presents an aura of related health issues such as untreatable nosocomial infections arising from organ transplants, surgeries, as well as community acquired infections that are related to people with compromised immunity e.g., diabetic and HIV patients etc. There is a global effort to fight multidrug resistant pathogens spearheaded by the World Health Organization, thus calling for research into novel antimicrobials agents to fight multiple drug resistance. Previously, our laboratory demonstrated that Cannabidiol (CBD) was an effective antimicrobial against Salmonella Typhimurium (S. Typhimurium). However, we observed resistance development over time. To understand the mechanisms S. Typhimurium uses to develop resistance to Cannabidiol (CBD), we studied the abundance of bacteria lipopolysaccharide (LPS) and membrane sterols of both susceptible and resistant S. Typhimurium. Using real-time quantitative polymerase chain reaction (rt qPCR), we also analyzed the expression of selected genes known for aiding resistance development in S. Typhimurium. We discovered that there was a significantly higher expression of blaTEM, fimA, fimZ, and integrons in the CBD-resistant bacteria, and these were also accompanied by a shift in abundance in cell surface molecules such as lipopolysaccharide (LPS) and sterols.

The rise of antimicrobial resistance is a global public health crisis that threatens the effective control and prevention of infections. Due to the emergence of pandrug-resistant bacteria, most antibiotics have lost their efficacy. Meanwhile, the development of new antimicrobials has stagnated, which leads to the creation of new and unconventional treatments. Bacteriophages or their components are known to target bacterial cell walls, cell membranes, and lipopolysaccharides (LPS) and hydrolyze them. Bacteriophages being the natural predators of pathogenic bacteria, are inevitably categorized as 'human friends', thus fulfilling the adage that 'the enemy of my enemy is my friend'. Leveraging on their lethal capabilities against pathogenic bacteria, researchers are searching for more ways to overcome the current antibiotic resistance challenge. Bacteriophages are considered to be one of the most effective alternative therapies for multidrug resistant bacteria. In this study, we expressed and purified epsilon 34 phage tailspike protein (E34 TSP) from the E34 TSP gene which was previously cloned into a pET30a-LIC vector, then assessed the ability of this bacteriophage protein in the killing of two CBD-resistant strains of Salmonella spp. We observed that the combined treatment of CBD-resistant strains of Salmonella with CBD and E34 TSP showed poor killing ability whereas the monotreatment with E34 TSP showed considerably higher killing efficiency.

Pseudacteon curvatus and P. obtusus are two species of parasitic phorid flies (Diptera: Phoridae), introduced in the southern USA for biological control of Solenopsis fire ants (Hymenoptera: Formicidae). The preference of both parasitoid species (P. curvatus and P. obtusus) for native Solenopsis fire ants (S. geminata complex) versus imported fire ants, S. saevissima complex (S. invicta and S. richteri) was investigated in four-choice olfactometer assays. We hypothesized that differences in the venom alkaloid profiles of fire ant species mediate host preference in phorid flies. In olfactometer bioassays, female P. obtusus showed preference for the venom alkaloid (cis + trans alkaloid mixture) of the imported S. invicta fire ant over the venom alkaloid of the native geminata fire ant. Similarly, P. obtusus showed preference for the venom alkaloid of the S. richteri fire ant over that of the native S. geminata ants. Pseudacteon curvatus also showed preference for the venom alkaloid of the S. invicta and S. richteri fire ants over that of the native geminata ants in separate bioassays. The results suggest that host preference in P. curvatus and P. obtusus is mediated, at least in part, by differences in the venom alkaloid profile of various fire ant species. This finding may explain why Pseudacteon species associated with either the S. geminata or S. saevissima complexes have not switched to the other group despite the overlap of native and imported fire ants in some areas of their distributions.

The kudzu bug, Megacopta cribraria (Fabricius) (Hemiptera: Plataspidae), is a major economic pest of soybean in the southeastern United States. With climate warming, this pest is expected to move northward and cause additional crop damage. Parasitoid biocontrol is a potential method of integrated pest management for kudzu bug. Two species of egg parasitoid wasps have been observed emerging from kudzu bug egg masses in the southeastern United States: Paratelenomus saccharalis (Dodd) (Hymenoptera: Platygastridae) and Ooencyrtus nezarae (Ishii) (Hymenoptera: Encyrtidae). This paper used egg mass emergence data collected between 2018 and 2020 in Alabama soybean fields and compared the data to weather indices. Indices included the number of days with minimum temperatures below zero, accumulated rainfall (mm m−2), as well as species specific metrics of accumulated growing degree days, accumulated daily minimum temperature (°C), and accumulated daily maximum temperature (°C). Emergence of the generalist parasitoid, O. nezarae, was highly correlated with kudzu bug nymph abundance, accumulated degree day, accumulated daily temperatures, and precipitation. Ooencyrtus nezarae emergence was predicted in a stepwise regression equation by aggregated degree day and date of collection, which indicates that seasonality may be a predictor of its presence. In contrast, collections of the specialist parasitoid, P. saccharalis, were near-zero throughout the collection period, suggesting that this species may no longer be a usable biocontrol agent in the southeastern United States as a result of external limiting factors.

Corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), has emerged as an injurious insect pest to hemp, Cannabis sativa L., a crop newly reintroduced to the United States. Growing hemp presents a potential alternative economic opportunity for farmers but can be challenging with a market that is unstable and just developing. One of the most notable production challenges is managing corn earworm, an insect pest that is particularly damaging when it feeds on flower buds produced in cannabinoid varieties, creating extensive bud tunneling and wounds that allow entry of pathogens that can aid development and presence of bud rot. Damage to seeds is of lesser concern in hemp cultivars grown for grain and minimal risk is associated with hemp grown for fiber. Our ability to research hemp has only recently been allowed as production was largely suspended following World War II and, as such, there has been limited opportunity to develop information for empirically-based pest management recommendations. Further complicating development of integrated pest management (IPM) strategies are regulatory challenges associated with providing registration support to add hemp to pesticide labels, as it was not formally recognized as a crop by U.S. regulatory agencies until late 2019. Research needs and challenges to develop effective IPM programs for corn earworm on hemp are discussed here.

The high surface area to volume ratio of terrestrial insects makes them highly susceptible to desiccation mainly through the cuticle. Cuticular permeability (CP) is usually the most important factor limiting water loss in terrestrial insects. Water loss rate, percentage of total body water (%TBW) content, CP, and desiccation tolerance were investigated in workers of four Solenopsis species in the southeastern USA. We hypothesized that tropical/subtropical ants (S. invicta and S. geminata) will have lower CP values and tolerate higher levels of desiccation than temperate ants (S. richteri and S. invicta &times, S. richteri). The %TBW content was similar among species. Solenopsis invicta had a 1.3-fold and 1.1-fold lower CP value than S. invicta &times, S. richteri and S. richteri, respectively. Solenopsis geminata had a 1.3-fold lower CP value than S. invicta &times, S. richteri, and a 1.2-fold lower CP value than S. richteri. The LT50 values (lethal time to kill 50% of the population) ranged from 1.5 h (small S. geminata) to 8.5 h (large S. invicta). Desiccation tolerance ranged between 36 and 50 %TBW lost at death and was not related to a species&rsquo, location of origin. This study is the first report of water relations of S. invicta &times, S. richteri. It demonstrates that desiccation stress differentially can affect the survival of different Solenopsis species and implies that environmental stress can affect the distribution of these species in the southeastern USA.

Some fire ants of the genus Solenopsis have become invasive species in the southern United States displacing native species by competition. Although the displacement pattern seems clear, the mechanisms underlying competitive advantage remain unclear. The ability of ant workers to produce relatively larger amount of alarm pheromone may correspond to relative greater fitness among sympatric fire ant species. Here we report on quantitative intra-specific (i.e. inter-caste) and inter-specific differences of alarm pheromone component, 2-ethyl-3,6-dimethylpyrazine (2E36DMP), for several fire ant species. The alarm pheromone component was extracted by soaking ants in hexane for 48 h and subsequently quantified by gas chromatography-mass spectrometry at single ion monitoring mode. Solenopsis invicta workers had more 2E36DMP than male or female alates by relative weight; individual workers, however, contained significantly less pyrazine. We thus believe that alarm pheromones may serve additional roles in alates. Workers of Solenopsis richteri, S. invicta, and hybrid (S. richteri × S. invicta) had significantly more 2E36DMP than a native fire ant species, Solenopsis geminata. The hybrid fire ant had significantly less 2E36DMP than the two parent species, S. richteri and S. invicta. It seems likely that higher alarm pheromone content may have favored invasion success of exotic fire ants over native species. We discuss the potential role of inter-specific variation in pyrazine content for the relationship between the observed shifts in the spatial distributions of the three exotic fire ant species in southern United States and the displacement of native fire ant species.

Sugar feeding is known to enhance lifespan in many parasitoid species. Several species of phorid flies in the genus Pseudacteon (Diptera: Phoridae) have been introduced in the Southern U.S.A. for the biological control of imported fire ants of Solenopsis species (Hymenoptera: Formicidae). Pseudacteon species are short-lived flies and little is known about their nutritional ecology. Results from previous studies in our laboratory show that one of the introduced species, Pseudacteon tricuspis Borgmeier, is capable of feeding on sugar sources with a significant increase in lifespan. However, in Pseudacteon phorid flies, the degree to which sugar feeding can enhance the lifespan of other species is not clear, nor is it known whether there is a relationship between body size and longevity. In the present study, the effect of sugar feeding on the survival of three phorid fly species of different body sizes, Pseudacteon cultellatus Borgmeier, Pseudacteon curvatus Borgmeier and Pseudacteon obtusus Borgmeier, is investigated. For all three species, flies continuously provided with 40% or 20% sucrose solution live longer than individuals provided water only or 40% sucrose solution only on the first day of adult life. However, the degree to which sugar feeding enhanced longevity varies by species and is highest for P. obtusus. The data also indicate that longevity in Pseudacteon phorid flies is related to body size: the largest species (P. obtusus) lives significantly longer than the smaller species (P. cultellatus and P. curvatus). These results suggest that adults of all three Pseudacteon species are capable of feeding on sucrose solution and that sugar feeding can enhance their longevity. The significance of these results is discussed in relation to the field performance of Pseudacteon phorid flies as biological control agents of imported fire ants.

Two sibling species, Solenopsis richteri and S. invicta, were both introduced into the southern USA from South America in the early 20th century. Today, S. richteri occupies higher latitudes and colder areas, while S. invicta occupies lower latitudes. Between the distributions of the two species, there is a large area of viable hybrid (S. richteri × S. invicta) populations. This study aimed to characterize the forces driving this distribution pattern and the underlying mechanisms. Cuticular hydrocarbons (CHCs) of freshly killed workers of S. invicta, hybrids, and S. richteri were removed using hexane. Both intact and CHCs-extracted workers were subjected to a constant rate of increasing temperature from 10 to 60 °C to obtain relative water loss and the water loss transition temperature (Tc-ant). Mass loss and Tc-ant were both significantly increased with CHCs removal. We then examined the CHC composition of three species. CHC profiles of S. richteri are characterized by significant amounts of short-chain (C23–C27) saturated and unsaturated hydrocarbons. In contrast, profiles of S. invicta consist primarily of long-chain (C27–C29) saturated hydrocarbons; unsaturated alkenes are completely lacking. Hybrid fire ants show intermediate profiles of the two parent species. We measured the melting point (Tm) and water-loss transition temperature of CHC blends (Tc-CHC) of different ant species colonies using differential scanning calorimetry (DSC) and an artificial membrane system, respectively. There were 3–5 Tms of each CHCs sample of different ant colonies due to their complex chemistry. The highest Tms (Tm-maxs) of CHCs samples from S. invicta and the hybrid were significantly higher than that from S. richteri. The correlation between Tc-CHC and Tm-max obtained from the same CHCs sample was highly significant. These results reveal that species having higher Tc and Tm-max retain more water under relatively higher temperature, and consequently are able to occupy warmer environments. We conclude that CHC chemistry plays a role in shaping current distribution patterns of S. richteri, S. invicta and their hybrid in the United States.