Culture Methods for Proteus mirabilis

The antimicrobial effect and mechanism of the Artemisia argyi essential oil against bacteria and fungus

Artemisia argyi is a traditional Chinese herb with antibacterial, antifungal, and antitumor activities. The essential oil of Artemisia argyi was extracted using the steam distillation method in this study. The chemical composition of the essential oil was analyzed using the gas chromatography-mass spectrometry method. Agar disc diffusion and double-broth dilution assays were used to detect the antimicrobial activity of the essential oil. Subsequently, the antimicrobial mechanisms were explored through cytomembrane permeability assay and electron microscopy. Based on gas chromatography-mass spectrometry analysis, 25 compounds were detected, including 13.76% cineole, 6.77% terpinen-4-ol, 6.68% 3-dione, 1,7,7-trimethyl-, 4.07% 3-cyclohexen-1-ol, 4-methyl-1-(1-methylethyl)-acetate, 3.58% 1-isopropyl-2-methylbenzene, and 1.58% g-terpinene. The essential oil was tested for antimicrobial activity, and the IC50 values for Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Listeria monocytogenes, Pseudomonas aeruginosa, Streptococcus pneumoniae, and Candida albicans were determined to be 25.51 ± 2.29, 49.53 ± 0.86, 52.40 ± 1.49, 52.76 ± 1.60, 73.99 ± 1.38, 65.52 ± 0.95, and 214.98 ± 3.27 μg mL-1, respectively. For essential oil interaction with cytoderm, the microorganisms treated by 1 × IC50 and 2 × IC50 concentration of essential oil both represented positive test results. Additionally, the alkaline phosphatase levels showed a direct correlation with concentration and treatment duration (range from 0 to 8 h). The interaction between essential oils and the cytomembrane was investigated by examining samples containing one of three test strains (Staphylococcus aureus, Escherichia coli, and Candida albicans), essential oil, and voltage-sensitive fluorescent dye disc35. The results demonstrated a significant increase in fluorescence levels within the solution upon introduction of the essential oil-treated strains. The findings of our research suggest that the essential oil disrupts the cytoderm and cytomembrane, thereby exhibiting antimicrobial activity.

Organ agar serves as physiologically relevant alternative for in vivo bacterial colonization

Animal models for host-microbial interactions have proven valuable, yielding physiologically relevant data that may be otherwise difficult to obtain. Unfortunately, such models are lacking or nonexistent for many microbes. Here, we introduce organ agar, a straightforward method to enable the screening of large mutant libraries while avoiding physiological bottlenecks. We demonstrate that growth defects on organ agar were translatable to bacterial colonization deficiencies in a murine model. Specifically, we present a urinary tract infection agar model to interrogate an ordered library of Proteus mirabilis transposon mutants, with accurate prediction of bacterial genes critical for host colonization. Thus, we demonstrate the ability of ex vivo organ agar to reproduce in vivo deficiencies. Organ agar was also useful for identifying previously unknown links between biosynthetic genes and swarming motility. This work provides a readily adoptable technique that is economical and uses substantially fewer animals. We anticipate this method will be useful for a wide variety of microorganisms, both pathogenic and commensal, in a diverse range of model host species.

Organ agar serves as physiologically relevant alternative for in vivo colonization

Animal models for host-microbial interactions have proven valuable, yielding physiologically relevant data that may be otherwise difficult to obtain. Unfortunately, such models are lacking or nonexistent for many microbes. Here, we introduce organ agar, a straightforward method to enable the screening of large mutant libraries while avoiding physiological bottlenecks. We demonstrate that growth defects on organ agar were translatable to colonization deficiencies in a murine model. Specifically, we present a urinary tract infection agar model to interrogate an ordered library of Proteus mirabilis transposon mutants, with accurate prediction of bacterial genes critical for host colonization. Thus, we demonstrate the ability of ex vivo organ agar to reproduce in vivo deficiencies. This work provides a readily adoptable technique that is economical and uses substantially fewer animals. We anticipate this method will be useful for a wide variety of microorganisms, both pathogenic and commensal, in a diverse range of model host species.

Sialic Acid Derivatives Inhibit SiaT Transporters and Delay Bacterial Growth

Antibiotic resistance is a major worldwide concern, and new drugs with mechanistically novel modes of action are urgently needed. Here, we report the structure-based drug design, synthesis, and evaluation in vitro and in cellular systems of sialic acid derivatives able to inhibit the bacterial sialic acid symporter SiaT. We designed and synthesized 21 sialic acid derivatives and screened their affinity for SiaT by a thermal shift assay and elucidated the inhibitory mechanism through binding thermodynamics, computational methods, and inhibitory kinetic studies. The most potent compounds, which have a 180-fold higher affinity compared to the natural substrate, were tested in bacterial growth assays and indicate bacterial growth delay in methicillin-resistant Staphylococcus aureus. This study represents the first example and a promising lead in developing sialic acid uptake inhibitors as novel antibacterial agents.

Comparison of a Chromogenic Urine Culture Plate System (UTid+) and Conventional Urine Culture for Canine and Feline Specimens

In companion animal medicine, urinary tract infection (UTI) is one of the most common indications for antimicrobial therapy. Definitive diagnosis of UTI requires isolation of bacteria with routine urine culture from an animal with concurrent clinical signs. Urine culture is typically performed at reference laboratories where paired susceptibility testing can be performed, but delays in shipment or processing can affect results. This study evaluated the use of a selective chromogenic, point-of-care culture system (UTid+) compared to conventional urine culture. A total of 119 (73 canine and 46 feline) cystocentesis urine samples were evaluated. Conventional urine culture was positive for 28 (23.5%) of the 119 cultures and UTid+ culture was positive for 26 (21.8%). The overall sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 92.3%, 97.8%, 92.3%, 97.8 and 96.6% for UTid+ respectively. Overall, the UTid+ culture system showed an acceptable level of accuracy when compared to conventional urine culture. Agreement of identification results was high (κ = 0.90) with an important exception being Proteus spp. which was only identified in 1/3 positive cultures. UTid+ may be useful in scenarios where a common UTI pathogen is expected and identification within 24 h is ideal; however, conventional urine culture remains the gold standard.

Not Only Antimicrobial: Metronidazole Mitigates the Virulence of Proteus mirabilis Isolated from Macerated Diabetic Foot Ulcer

Diabetic foot ulcers are recognized to be a severe complication of diabetes, increasing the risk of amputation and death. The bacterial infection of Diabetic foot ulcers with virulent and resistant bacteria as Proteus mirabilis greatly worsens the wound and may not be treated with conventional therapeutics. Developing new approaches to target bacterial virulence can be helpful to conquer such infections. In the current work, we evaluated the anti-virulence activities of the widely used antibacterial metronidazole. The minimum inhibitory concentrations (MIC) and minimum biofilm eradication concentrations (MEBC) were determined for selected antibiotics which P. mirabilis was resistant to them in the presence and absence of metronidazole in sub-MIC. The effect of metronidazole in sub-MIC on P. mirabilis virulence factors as production of exoenzymes, motilities, adhesion and biofilm formation, were evaluated. Furthermore, molecular docking of metronidazole into P. mirabilis adhesion and essential quorum sensing (QS) proteins, was performed. The results revealed a significant ability of metronidazole to in-vitro inhibit P. mirabilis virulence factors and antagonize its essential proteins. Moreover, metronidazole markedly decreased the MICs and MBECs of tested antibiotics. Conclusively, metronidazole in sub-MIC is a plausible anti-virulence and anti-QS agent that can be combined to other antibiotics as anti-virulence adjuvant to defeat aggressive infections.