Effects of four commercial fungal formulations on mortality and sporulation in house flies (Musca domestica) and stable flies (Stomoxys calcitrans)

Progress in the Study of Natural Antimicrobial Active Substances in Pseudomonas aeruginosa

The prevalence of antimicrobial resistance reduces the effectiveness of antimicrobial drugs in the prevention and treatment of infectious diseases caused by pathogens such as bacteria, fungi, and viruses. Microbial secondary metabolites have been recognized as important sources for new drug discovery and development, yielding a wide range of structurally novel and functionally diverse antimicrobial drugs for the treatment of a variety of diseases that are considered good producers of novel antimicrobial drugs. Bacteria produce a wide variety of antimicrobial compounds, and thus, antibiotics derived from natural products still dominate over purely synthetic antibiotics among the antimicrobial drugs developed and introduced over the last four decades. Among them, Pseudomonas aeruginosa secondary metabolites constitute a richly diverse source of antimicrobial substances with good antimicrobial activity. Therefore, they are regarded as an outstanding resource for finding novel bioactive compounds. The exploration of antimicrobial compounds among Pseudomonas aeruginosa metabolites plays an important role in drug development and biomedical research. Reports on the secondary metabolites of Pseudomonas aeruginosa, many of which are of pharmacological importance, hold great promise for the development of effective antimicrobial drugs against microbial infections by drug-resistant pathogens. In this review, we attempt to summarize published articles from the last twenty-five years (2000-2024) on antimicrobial secondary metabolites from Pseudomonas aeruginosa.

Activity Against Musca domestica of Hypocrealean Fungi Isolated from Culicids in Central Brazil and Formulated in Vermiculite

Musca domestica L. is a cosmopolitan nuisance of high sanitary importance. Entomopathogenic fungi are innovative and attractive tools for integrated control of the housefly to overcome insufficient levels of control caused by increasing resistance of this pest against chemical insecticides. High virulence of a fungal strain is a prerequisite to develop a mycoinsecticide, and the present study investigated the potential of hypocrealean fungi from the genera Beauveria, Clonostachys, Cordyceps, Akanthomyces, Metarhizium, and Tolypocladium, isolated from mosquitoes in Central Brazil against M. domestica. The highest mortalities (larvae, pupae, and adults) were caused by Metarhizium humberi IP 478 (98%) and IP 421 (90%), Metarhizium anisopliae IP 432 (85%), Beauveria bassiana IP 433 (82%), and Tolypocladium cylindrosporum IP 425 (68%) after a 23-day exposure of initially pre-pupating third instar larvae to conidia mixed with vermiculite. Lethal concentrations to kill 90% of adults of IP 433 and IP 478 were 5 × 10⁷ and 10⁸ conidia g^-1 substrate, respectively. Fifty percent of adults were killed within 4 to 5 days of exposure initially as pupae close to emergence to substrate treated with conidia of IP 478 or IP 433 at 1.1 × 10⁸ conidia g^-1, respectively. The other fungal strains tested were less virulent. The results demonstrate high potentials for conidial preparations in vermiculite of IP 433 and IP 478 as candidates for the biological control of both pre-pupating larvae, pupae, and emerging adults of houseflies.

Comparative Virulence of Metarhizium anisopliae and Four Strains of Beauveria bassiana Against House Fly (Diptera: Muscidae) Adults With Attempted Selection for Faster Mortality

Entomopathogenic fungi such as Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae/brunneum (Metchnikoff)/Petch have shown promising results for managing the house fly, Musca domestica L. A primary challenge of using these biological control agents (BCAs) in field situations is the time required to induce high adult house fly mortality, typically 6-7 d post-exposure. In this study, virulence of M. anisopliae (strain F52) and four B. bassiana strains were compared. The B. bassiana strains GHA and HF23 are used in commercial products and those were compared with two strains that were isolated from house flies on dairy farms (NFH10 and L90). Assays were conducted by exposing adult house flies to fungal-treated filter paper disks for 2 h. The lethal time to 50% mortality (LT50) at the high concentration of 1 × 109 conidia ranged from 3.8 to 5.2 d for all five strains. GHA, NFH10, and L90 killed flies faster than M. anisopliae strain F52; HF23 did not differ from either the M. anisopliae or the other B. bassiana strains. Attempts with the NFH10 strain to induce faster fly mortality through selection across 10 fungal to fly passages did not result in shorter time to fly death of the selected strain compared with the unselected strain.

Dysbacteriosis of the Intestinal Flora Is an Important Reason for the Death of Adult House Flies Caused by Beauveria bassiana

Beauveria bassiana is one of the most widespread insect pathogens and can be used in the biological control of agricultural, forestry and medical pests. The mechanisms by which B. bassiana leads to mortality in different host insects are also different. For house flies, B. bassiana has strong virulence, but its microecological mechanism is not clear. In this paper, the virulence of three strains of B. bassiana (TB, CB and BB) isolated from different hosts to house flies was studied. The results showed that the three strains of B. bassiana had strong pathogenicity to house fly adults. Specifically, TB was the strongest, CB was the second strongest, and BB was the weakest, with maximum lethal effects on house fly populations 5, 6, and 7 days after infection, respectively. Further study showed that the intestinal flora of house flies was disordered 3, 4, and 5 days after B. bassiana TB, CB and BB strain infection, respectively. Intestinal flora dysbacteriosis may be an important reason for the death of house flies caused by B. bassiana. After infection, the negative interaction ratio of bacteria in the house fly intestine decreased, and the stronger the virulence was, the lower the negative interaction ratio was. The time from B. bassiana infection to intestinal flora dysbacteriosis was not fixed. We named this period the “spring stage”. The stronger the virulence of the B. bassiana strain was, the shorter the “spring stage” was. Therefore, the “spring stage” can be used as a virulence marker for evaluating the pathogenicity of different B. bassiana strains.

Comparative Genomic and Metabolomic Analyses of Two Pseudomonas aeruginosa Strains With Different Antifungal Activities

Pseudomonas aeruginosa isolated from the plant rhizosphere has been widely used as an effective strain in biological control against plant disease. This bacterium promotes plant growth and protect plants against various phytopathogens through the production of phenazine metabolites. In this study, the strain P. aeruginosa Y12 with anti-Beauveria bassiana activity was isolated from the gut of housefly larvae. It was comparatively analyzed with the strain P. aeruginosa P18, which showed no anti-B. bassiana activity. Genomic and metabolomic methods were used to obtain a comprehensive understanding of the antimicrobial mechanism of Y12. After whole-genome resequencing of the two strains, a total of 7,087 non-synonymous single-nucleotide polymorphisms (nsSNPs), 1079 insertions and deletions (InDels), 62 copy-number variations (CNVs) and 42 structural variations (SV) were found in both strains. We analyzed the differentially abundant metabolites between Y12 and P18, and identified six bioactive compounds that could be associated with the antimicrobial activity of Y12. Additionally, we found that, unlike other previously reported rhizospheric P. aeruginosa strains, Y12 could produce both phenazine-1,6-dicarboxylic acid (PDC) and pyocyanin (PYO) at significantly higher concentrations than P18. As B. bassiana is an effective biological insecticide that can cause high mortality in adult houseflies but has little effect on housefly larvae, we believe that P. aeruginosa Y12, identified in housefly larvae but not in adults, were beneficial for the development of housefly larvae and could protect them from B. bassiana infection through the production of toxic metabolites.

Auto-dissemination of commercially available fungal pathogens in a laboratory assay for management of the brown dog tick Rhipicephalus sanguineus

Rhipicephalus sanguineus is a canine tick that infests dogs throughout the world and is frequently found in homes and dog kennels. Management of this tick species is complicated by the presence of resistance to commonly utilized acaricides. Fungal formulations could provide a valuable alternative tool for management and are especially relevant indoors where detrimental environmental effects on fungal spores are of less concern. Two commercially available fungal formulations, one containing Metarhizium anisopliae and the other containing Beauveria bassiana, were compared for time to death and sporulation in nymphal ticks exposed for 60 min in treated filter paper packets. Beauveria bassiana exposure killed ticks faster than M. anisopliae exposure and B. bassiana was more likely to sporulate on tick cadavers than M. anisopliae. To determine whether infected ticks could disseminate fungus to their conspecifics, ticks were marked and treated with fungus before being placed with untreated ticks. Fungus was successfully transmitted from treated to untreated ticks. Mortality of ticks exposed to B. bassiana-exposed conspecifics occurred sooner than for those exposed to M. anisopliae-exposed conspecifics, indicating faster dissemination in the former. Therefore, although both formulations resulted in decreased longevity of ticks compared with the controls, the B. bassiana formulation holds the most promise for direct or indirect application with respect to brown dog tick management.

A Historical Review of Management Options Used against the Stable Fly (Diptera: Muscidae)

The stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), remains a significant economic pest globally in situations where intensive animal production or horticultural production provide a suitable developmental medium. Stable flies have been recorded as pests of livestock and humans since the late 1800s to early 1900s. Over 100 years of research has seen numerous methodologies used to control this fly, in particular to protect cattle from flies to minimise production losses. Reduced milk production in dairy cows and decreased weight gain in beef cattle account for losses in the US alone of > $2000 million annually. Rural lifestyles and recreation are also seriously affected. Progress has been made on many control strategies against stable fly over a range of chemical, biological, physical and cultural options. This paper reviews management options from both a historical and a technical perspective for controlling this pest. These include the use of different classes of insecticides applied to affected animals as toxicants or repellents (livestock and humans), as well as to substrates where stable fly larvae develop. Arthropod predators of stable flies are listed, from which potential biological control agents (e.g., wasps, mites, and beetles) are identified. Biopesticides (e.g., fungi, bacteria and plant-derived products) are also discussed along with Integrated Pest Management (IPM) against stable flies for several animal industries. A review of cultural and physical management options including trapping, trap types and methodologies, farm hygiene, scheduled sanitation, physical barriers to fly emergence, livestock protection and amendments added to animal manures and bedding are covered. This paper presents a comprehensive review of all management options used against stable flies from both a historical and a technical perspective for use by any entomologist, livestock producer or horticulturalist with an interest in reducing the negative impact of this pest fly.

Secretomic analysis of Beauveria bassiana related to cattle tick, Rhipicephalus microplus, infection

Beauveria bassiana is widely studied as an alternative to chemical acaricides in controlling the cattle tick Rhipicephalus microplus. Although its biocontrol efficiency has been proved in laboratory and field scales, there is a need to a better understanding of host interaction process at molecular level related to biocontrol activity. In this work, applying a proteomic technique multidimensional protein identification technology (MudPIT), the differential secretome of B. bassiana induced by the host R. microplus cuticle was evaluated. The use of the host cuticle in a culture medium, mimicking an infection condition, is an established experimental model that triggers the secretion of inducible enzymes. From a total of 236 proteins, 50 proteins were identified exclusively in infection condition, assigned to different aspects of infection like host adhesion, cuticle penetration and fungal defense, and stress. Other 32 proteins were considered up- or down-regulated. In order to get a meaningful global view of the secretome, several bioinformatic analyses were performed. Regarding molecular function classification, the highest number of proteins in the differential secretome was assigned in to hydrolase activity, enzyme class of all cuticle-degrading enzymes like lipases and proteases. These activities were also further validated through enzymatic assays. The results presented here reveal dozens of specific proteins and different processes potentially implicated in cattle tick infection improving the understanding of molecular basis of biocontrol of B. bassiana against R. microplus.