Proteus mirabilis UreR coordinates cellular functions required for urease activity.

A hallmark of Proteus mirabilis infection of the urinary tract is the formation of stones. The ability to induce urinary stone formation requires urease, a nickel metalloenzyme that hydrolyzes urea. This reaction produces ammonia as a byproduct, which can serve as a nitrogen source and weak base that raises the local pH. The resulting alkalinity induces the precipitation of ions to form stones. Transcriptional regulator UreR activates expression of urease genes in a urea-dependent manner. Thus, urease genes are highly expressed in the urinary tract where urea is abundant. Production of mature urease also requires the import of nickel into the cytoplasm and its incorporation into the urease apoenzyme. Urease accessory proteins primarily acquire nickel from one of two nickel transporters and facilitate incorporation of nickel to form mature urease. In this study, we performed a comprehensive RNA-seq to define the P. mirabilis urea-induced transcriptome as well as the UreR regulon. We identified UreR as the first defined regulator of nickel transport in P. mirabilis. We also offer evidence for the direct regulation of the Ynt nickel transporter by UreR. Using bioinformatics, we identified UreR-regulated urease loci in 15 Morganellaceae family species across three genera. Additionally, we located two mobilized UreR-regulated urease loci that also encode the ynt transporter, implying that UreR regulation of nickel transport is a conserved regulatory relationship. Our study demonstrates that UreR specifically regulates genes required to produce mature urease, an essential virulence factor for P. mirabilis uropathogenesis. IMPORTANCE: Catheter-associated urinary tract infections (CAUTIs) account for over 40% of acute nosocomial infections in the USA and generate $340 million in healthcare costs annually. A major causative agent of CAUTIs is Proteus mirabilis, an understudied Gram-negative pathogen noted for its ability to form urinary stones via the activity of urease. Urease mutants cannot induce stones and are attenuated in a murine UTI model, indicating this enzyme is essential to P. mirabilis pathogenesis. Transcriptional regulation of urease genes by UreR is well established; here, we expand the UreR regulon to include regulation of nickel import, a function required to produce mature urease. Furthermore, we reflect on the role of urea catalysis in P. mirabilis metabolism and provide evidence for its importance.

Genetic characteristics of chromosomally integrated carbapenemase gene (blaNDM-1) in isolates of Proteus mirabilis.

OBJECTIVE: This study aims to conduct an in-depth genomic analysis of a carbapenem-resistant Proteus mirabilis strain to uncover the distribution and mechanisms of its resistance genes. METHODS: The research primarily utilized whole-genome sequencing to analyze the genome of the Proteus mirabilis strain. Additionally, antibiotic susceptibility tests were conducted to evaluate the strain's sensitivity to various antibiotics, and related case information was collected to analyze the clinical distribution characteristics of the resistant strain. RESULTS: Study on bacterial strain WF3430 from a tetanus and pneumonia patient reveals resistance to multiple antibiotics due to extensive use. Whole-genome sequencing exposes a 4,045,480 bp chromosome carrying 29 antibiotic resistance genes. Two multidrug-resistant (MDR) gene regions, resembling Tn6577 and Tn6589, were identified (MDR Region 1: 64.83 Kb, MDR Region 2: 85.64 Kbp). These regions, consist of integrative and conjugative elements (ICE) structures, highlight the intricate multidrug resistance in clinical settings. CONCLUSION: This study found that a CR-PMI strain exhibits a unique mechanism for acquiring antimicrobial resistance genes, such as blaNDM-1, located on the chromosome instead of plasmids. According to the results, there is increasing complexity in the mechanisms of horizontal transmission of resistance, necessitating a comprehensive understanding and implementation of targeted control measures in both hospital and community settings.

Downregulation of Klebsiella pneumoniae RND efflux pump genes following indole signal produced by Escherichia coli.

BACKGROUND: More than a century has passed since it was discovered that many bacteria produce indole, but research into the actual biological roles of this molecule is just now beginning. The influence of indole on bacterial virulence was extensively investigated in indole-producing bacteria like Escherichia coli. To gain a deeper comprehension of its functional role, this study investigated how indole at concentrations of 0.5-1.0 mM found in the supernatant of Escherichia coli stationary phase culture was able to alter the virulence of non-indole-producing bacteria, such as Pseudomonas aeruginosa, Proteus mirabilis, and Klebsiella pneumoniae, which are naturally exposed to indole in mixed infections with Escherichia coli. RESULTS: Biofilm formation, antimicrobial susceptibility, and efflux pump activity were the three phenotypic tests that were assessed. Indole was found to influence antibiotic susceptibly of Pseudomonas aeruginosa, Proteus mirabilis and Klebsiella pneumoniae to ciprofloxacin, imipenem, ceftriaxone, ceftazidime, and amikacin through significant reduction in MIC with fold change ranged from 4 to 16. Biofilm production was partially abrogated in both 32/45 Pseudomonas aeruginosa and all eight Proteus mirabilis, while induced biofilm production was observed in 30/40 Klebsiella pneumoniae. Moreover, acrAB and oqxAB, which encode four genes responsible for resistance-nodulation-division multidrug efflux pumps in five isolates of Klebsiella pneumoniae were investigated genotypically using quantitative real-time (qRT)-PCR. This revealed that all four genes exhibited reduced expression indicated by 2^-ΔΔCT < 1 in indole-treated isolates compared to control group. CONCLUSION: The outcomes of qRT-PCR investigation of efflux pump expression have established a novel clear correlation of the molecular mechanism that lies beneath the influence of indole on bacterial antibiotic tolerance. This research provides novel perspectives on the various mechanisms and diverse biological functions of indole signaling and how it impacts the pathogenicity of non-indole-producing bacteria.

Caspase-like activity is associated with bacterial infection of the urine in urinary tract diseases.

Urinary tract infections (UTIs) are a serious public health problem. They can be caused by a number of pathogens, but the most common are Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Enterococcus faecalis and Staphylococcus saprophyticus. Bacterial infection is diagnosed by examining a urine sample. The presence of bacteria or white blood cells is determined under a microscope or a urine culture is performed. In this study, we used a panel of chromogenic substrates for the qualitative determination of specific enzyme activity in the urine of patients with confirmed bacterial infection and/or urinary tract disease. Healthy patients were used as a control group. It turned out that in the case of Escherichia coli infection, we observed the activity of the caspase subunit of the human 20S proteasome. We did not observe similar correlations for infections with other types of bacteria.

Distinct Commensals Induce Interleukin-1ß via NLRP3 Inflammasome in Inflammatory Monocytes to Promote Intestinal Inflammation in Response to Injury.

The microbiota stimulates inflammation, but the signaling pathways and the members of the microbiota involved remain poorly understood. We found that the microbiota induces interleukin-1ß (IL-1ß) release upon intestinal injury and that this is mediated via the NLRP3 inflammasome. Enterobacteriaceae and in particular the pathobiont Proteus mirabilis, induced robust IL-1ß release that was comparable to that induced by the pathogen Salmonella. Upon epithelial injury, production of IL-1ß in the intestine was largely mediated by intestinal Ly6C(high) monocytes, required chemokine receptor CCR2 and was abolished by deletion of IL-1ß in CCR2(+) blood monocytes. Furthermore, colonization with P. mirabilis promoted intestinal inflammation upon intestinal injury via the production of hemolysin, which required NLRP3 and IL-1 receptor signaling in vivo. Thus, upon intestinal injury, selective members of the microbiota stimulate newly recruited monocytes to induce NLRP3-dependent IL-1ß release, which promotes inflammation in the intestine.

Biosynthesis of α-keto acids and resolution of chiral amino acids by l-amino acid deaminases from Proteus mirabilis.

Chiral amino acids and their deamination products, α-keto acids, have important applications in food, medicine, and fine chemicals. In this study, two l-amino acid deaminase genes from Proteus mirabilis, PM473 of type Ⅰ and PM471 of type Ⅱ were cloned and expressed in Escherichia coli respectively, expected to achieve the chiral separation of amino acids. Extensive substrate preference testing showed that both deaminases had catalytic effects on the d-amino acid component of the D, l-amino acids, and PM473 has a wider catalytic range for amino acids. When D, L-Cys was used as the substrate, all L-Cys components and 75.1 % of D-Cys were converted to mercapto pyruvate, and the remaining D-Cys was a single chiral enantiomer. Molecular docking analysis showed that the interaction between the substrate and the key residues affected the stereoselectivity of enzymes. The compatibility of hydrophobicity between the binding pocket and substrate may be the basic factor that affects the substrate selectivity. This work provides an alternative method for the production of α-keto acids and the resolution of chiral amino acids.

In vitro and in vivo study of antibacterial and anti-encrustation coating on ureteric stents.

OBJECTIVES: To investigate the ability of propolis-coated ureteric stents to solve complications, especially urinary tract infections (UTIs) and crusting, in patients with long-term indwelling ureteric stents through antimicrobial and anti-calculus activities. MATERIALS AND METHODS: Polyurethane (PU) ureteric stents were immersed in the ethanol extract of propolis (EEP), a well-known antimicrobial honeybee product, and subjected to chemical, hydrophilic, and seismic tests. The antimicrobial activity of the EEP coating was then examined by in vitro investigation. Proteus mirabilis infection was induced in rats within uncoated and EEP-coated groups, and the infection, stone formation, and inflammation were monitored at various time points. RESULTS: The characterisation results showed that the hydrophilicity and stability of the EEP surface improved. In vitro tests revealed that the EEP coating was biocompatible, could eliminate >90% of bacteria biofilms attached to the stent and could maintain bacteriostatic properties for up to 3 months. The in vivo experiment revealed that the EEP-coating significantly reduced the amount of bacteria, stones, and salt deposits on the surface of the ureteric stents and decreased inflammation in the host tissue. CONCLUSIONS: Compared with clinically used PU stents, EEP-coated ureteric stents could better mitigate infections and prevent encrustation. Thus, this study demonstrated that propolis is a promising natural dressing material for ureteric stents.

An in-vitro model for bacteria-related catheter encrustations.

PURPOSE: About 50% of individuals with long-term indwelling catheters are affected by catheter encrustations and bladder stone formation. Therefore, prophylaxis of catheter encrustations is important. Currently, however, neither an established prophylaxis nor a standardized in-vitro model to test different measures exist. We have therefore developed and qualitatively evaluated an in-vitro model of catheter encrustation. METHODS: Size 14 French suprapubic catheters were incubated under sterile conditions at 37 degrees Celsius in five different media: (1) sterile artificial urine (n = 16), (2) artificial urine with E. coli (n = 8), (3) with Pseudomonas aeruginosa (n = 8), (4) with Proteus mirabilis (n = 8), and (5) with a mix of these three strains (n = 8). Catheter balloons were inflated either a glycerine or a bactericidal solution. After 6 weeks, the catheters were removed from the solution, dried, and weighed, and a photometric determination of the retrieved encrustations was performed. RESULTS: Most frequently and pronounced encrustations were detected in the Pseudomonas group. The median weight of these encrustations (50% struvite and brushite) was 84.4 mg (47.7 mg / 127.3 mg). Even on catheters stored in sterile urine, encrustations (69.2% struvite) were found. Bacterial growth was not affected by the medium used for catheter blockage. CONCLUSION: Although in-vitro models appear to be limited because they lack "the human factor", they are valuable for systematically assessing physico-chemical factors affecting encrustations. Therefore, our model, being reliable and cost-effective, may foster further research despite its limitations.

Emergence and genomic chion of Proteus mirabilis harboring blaNDM-1 in Korean companion dogs.

Proteus mirabilis is a commensal bacterium dwelling in the gastrointestinal (GI) tract of humans and animals. Although New Delhi metallo-ß-lactamase 1 (NDM-1) producing P. mirabilis is emerging as a threat, its epidemiology in our society remains largely unknown. LHPm1, the first P. mirabilis isolate harboring NDM-1, was detected from a companion dog that resides with a human owner. The whole-genome study revealed 20 different antimicrobial resistance (AMR) genes against various classes of antimicrobial agents, which corresponded to the MIC results. Genomic regions, including MDR genes, were identified with multiple variations and visualized in a comparative manner. In the whole-genome epidemiological analysis, multiple phylogroups were identified, revealing the genetic relationship of LHPm1 with other P. mirabilis strains carrying various AMR genes. These genetic findings offer comprehensive insights into NDM-1-producing P. mirabilis, underscoring the need for urgent control measures and surveillance programs using a "one health approach".

Occurrence and characterization of Proteus mirabilis from infected farmed African catfish in Ogun State, Nigeria.

BACKGROUND: Bacterial pathogens are the causative agents of some of the most serious disease problems in cultured fish causing mortalities and severe economic losses. This study was conducted to determine the occurrence and characterization of Proteus mirabilis from infected farmed African catfish in Ogun State, Nigeria. METHODOLOGY: The bacteria were isolated from diseased farmed African catfish (Clarias gariepinus, n=128) with clinical signs of skin haemorrhages, ulceration, and ascites purposively sampled from farms within three senatorial districts namely Ogun East (OE; n=76), Ogun Central (OC; n=30) and Ogun West (OW; n=22) in Ogun State. The isolates were identified based on morphological characteristics, biochemical tests, and 16S rRNA gene characterisation. The 16S rRNA gene sequences were analysed using BLAST, submitted to the NCBI database, and an accession number was generated. RESULTS: The occurrence of Proteus mirabilis in infected Clarias gariepinus was 13.16%, 25%, and 31.25% in OE, OC, and OW, respectively. A significantly higher incidence was recorded in OW compared to other areas. All the Proteus mirabilis isolates were motile, gram-negative, short rod, non-lactose fermenter bacteria that showed positive catalase reactions, negative oxidase, and positive for methyl-red. The Proteus mirabilis isolates (OP 594726.1) were closely related to isolates from Pakistan, Italy, and India CONCLUSIONS: We conclude that Proteus mirabilis colonises farmed Clarias gariepinus in Ogun State, Nigeria and the identified strain showed an evolutionary relationship with known pathogenic NCBI reference strains from other countries.

Identification of mechanisms modulating chlorhexidine and octenidine susceptibility in Proteus mirabilis.

AIMS: We aimed to identify mechanisms underlying the tolerance of Proteus mirabilis-a common cause of catheter associated urinary tract infection-to the clinically used biocides chlorhexidine (CHD) and octenidine (OCT). METHODS AND RESULTS: We adapted three clinical isolates to grow at concentrations of 512 µg ml-1 CHD and 128 µg ml-1 OCT. Genetic characterization and complementation studies revealed mutations inactivating the smvR repressor and increasing smvA efflux expression were associated with adaptation to both biocides. Mutations in mipA (encoding the MltA interacting protein) were less prevalent than smvR mutations and only identified in CHD adapted populations. Mutations in the rppA response regulator were exclusive to one adapted isolate and were linked with reduced polymyxin B susceptibility and a predicted gain of function after biocide adaptation. Biocide adaptation had no impact on crystalline biofilm formation. CONCLUSIONS: SmvR inactivation is a key mechanism in both CHD and OCT tolerance. MipA inactivation alone confers moderate protection against CHD, and rppA showed no direct role in either CHD or OCT susceptibility.

Emergence of extensive drug resistance and high prevalence of multidrug resistance among clinical Proteus mirabilis isolates in Egypt.

BACKGROUND: Proteus mirabilis is an opportunistic pathogen that has been held responsible for numerous nosocomial and community-acquired infections which are difficult to be controlled because of its diverse antimicrobial resistance mechanisms. METHODS: Antimicrobial susceptibility patterns of P. mirabilis isolates collected from different clinical sources in Mansoura University Hospitals, Egypt was determined. Moreover, the underlying resistance mechanisms and genetic relatedness between isolates were investigated. RESULTS: Antimicrobial susceptibility testing indicated elevated levels of resistance to different classes of antimicrobials among the tested P. mirabilis clinical isolates (n = 66). ERIC-PCR showed great diversity among the tested isolates. Six isolates (9.1%) were XDR while all the remaining isolates were MDR. ESBLs and AmpCs were detected in 57.6% and 21.2% of the isolates, respectively, where blaTEM, blaSHV, blaCTX-M, blaCIT-M and blaAmpC were detected. Carbapenemases and MBLs were detected in 10.6 and 9.1% of the isolates, respectively, where blaOXA-48 and blaNDM-1 genes were detected. Quinolone resistant isolates (75.8%) harbored acc(6')-Ib-cr, qnrD, qnrA, and qnrS genes. Resistance to aminoglycosides, trimethoprim-sulfamethoxazole and chloramphenicol exceeded 80%. Fosfomycin was the most active drug against the tested isolates as only 22.7% were resistant. Class I or II integrons were detected in 86.4% of the isolates. Among class I integron positive isolates, four different gene cassette arrays (dfrA17- aadA5, aadB-aadA2, aadA2-lnuF, and dfrA14-arr-3-blaOXA-10-aadA15) and two gene cassettes (dfrA7 and aadA1) were detected. While class II integron positive isolates carried four different gene cassette arrays (dfrA1-sat1-aadA1, estXVr-sat2-aadA1, lnuF- dfrA1-aadA1, and dfrA1-sat2). CONCLUSION: P. Mirabilis ability to acquire resistance determinants via integrons may be held responsible for the elevated rates of antimicrobial resistance and emergence of XDR or even PDR strains limiting the available therapeutic options for management of infections caused by those strains.

Potential antivirulence activity of sub-inhibitory concentrations of ciprofloxacin against Proteus mirabilis isolates: an in-vitro and in-vivo study.

BACKGROUND: Proteus mirabilis is a significant nosocomial pathogen that is frequently associated with a wide range of infections, necessitating heightened attention to mitigate potential health risks. Hence, this study was performed to investigate the impact of sub-minimum inhibitory concentrations (MICs) of ciprofloxacin (CIP) on Proteus mirabilis clinical isolates. METHODS: The sub-MICs of CIP were selected using the growth curve approach. The untreated and treated isolates with sub-MICs of CIP were assessed for their biofilm development, motilities on agar, and other virulence factors. The cell morphology of untreated and treated isolates with sub-MIC of CIP was explored using electron microscope. Moreover, the expression levels of the virulence genes in isolates were measured using quantitative real-time PCR. RESULTS: Data revealed that sub-MICs of CIP significantly (p < 0.05), in a concentration-dependent manner, inhibited biofilm formation and other virulence factors in the selected isolates. Electron microscope analysis showed cell enlargement and various abnormalities in the cell wall and membrane integrity. CONCLUSION: Sub-MICs of CIP exhibited inhibition of virulence and alterations in morphological integrity against P. mirabilis isolates.

Molecular characterization of a carbon dioxide-dependent Proteus mirabilis small-colony variant isolated from a clinical specimen.

INTRODUCTION: Carbon dioxide-dependent Proteus mirabilis has been isolated from clinical specimens. It is not clear whether mutations in carbonic anhydrase are responsible for the carbon dioxide dependence of P. mirabilis. The pathogenicity of carbon dioxide-dependent P. mirabilis also remains unclear. The purpose of this study was to determine the cause carbon dioxide dependence of P. mirabilis and its pathogenicity. METHODS: The DNA sequence of can encoding carbonic anhydrase of a carbon dioxide-dependent P. mirabilis small colony variant (SCV) isolate was analyzed. To confirm that impaired carbonic anhydrase activity is responsible for the formation of the carbon dioxide-dependent SCV phenotype of P. mirabilis, we performed complementation experiments using plasmids with intact can. Additionally, mouse infection experiments were performed to confirm the change in virulence due to the mutation of carbonic anhydrase. RESULTS: We found that the can gene of the carbon dioxide-dependent P. mirabilis SCV isolate showed had a frameshift mutation with a deletion of 1 bp (c. 173delC). The can of P. mirabilis encodes carbonic anhydrase was also found to function in Escherichia coli. The cause of the carbon dioxide-dependent SCV phenotype of P. mirabilis was an abnormality in carbonic anhydrase. Nevertheless, no changes were observed in virulence due to the mutation of carbonic anhydrase in mouse infection experiments. CONCLUSIONS: The can gene is essential for the growth of P. mirabilis in ambient air. The mechanisms underlying this fitness advantage in terms of infection warrant further investigation.

Green-Synthesized Silver Nanoparticles in the Prevention of Multidrug-Resistant Proteus mirabilis Infection and Incrustation of Urinary Catheters BioAgNPs Against P. mirabilis Infection.

This study aimed to assess the activity of AgNPs biosynthesized by Fusarium oxysporum (bio-AgNPs) against multidrug-resistant uropathogenic Proteus mirabilis, and to assess the antibacterial activity of catheters coated with bio-AgNPs. Broth microdilution and time-kill kinetics assays were used to determine the antibacterial activity of bio-AgNPs. Catheters were coated with two (2C) and three (3C) bio-AgNPs layers using polydopamine as crosslinker. Catheters were challenged with urine inoculated with P. mirabilis to assess the anti-incrustation activity. MIC was found to be 62.5 µmol l-1, causing total loss of viability after 4 h and bio-AgNPs inhibited biofilm formation by 76.4%. Catheters 2C and 3C avoided incrustation for 13 and 20 days, respectively, and reduced biofilm formation by more than 98%, while the pristine catheter was encrusted on the first day. These results provide evidence for the use of bio-AgNPs as a potential alternative to combat of multidrug-resistant P. mirabilis infections.

Bacterial-induced pH shifts link individual cell physiology to macroscale collective behavior.

Bacteria have evolved a diverse array of signaling pathways that enable them to quickly respond to environmental changes. Understanding how these pathways reflect environmental conditions and produce an orchestrated response is an ongoing challenge. Herein, we present a role for collective modifications of environmental pH carried out by microbial colonies living on a surface. We show that by collectively adjusting the local pH value, Paenibacillus spp., specifically, regulate their swarming motility. Moreover, we show that such pH-dependent regulation can converge with the carbon repression pathway to down-regulate flagellin expression and inhibit swarming in the presence of glucose. Interestingly, our results demonstrate that the observed glucose-dependent swarming repression is not mediated by the glucose molecule per se, as commonly thought to occur in carbon repression pathways, but rather is governed by a decrease in pH due to glucose metabolism. In fact, modification of the environmental pH by neighboring bacterial species could override this glucose-dependent repression and induce swarming of Paenibacillus spp. away from a glucose-rich area. Our results suggest that bacteria can use local pH modulations to reflect nutrient availability and link individual bacterial physiology to macroscale collective behavior.

The Cd resistant mechanism of Proteus mirabilis Ch8 through immobilizing and detoxifying.

Cadmium (Cd) pollution is a serious global environmental problem, which requires a global concern and practical solutions. Microbial remediation has received widespread attention owing to advantages, such as environmental friendliness and soil amelioration. However, Cd toxicity also severely deteriorates the remediation performance of functional microorganisms. Analyzing the mechanism of bacterial resistance to Cd stress will be beneficial for the application of Cd remediation. In this study, the bacteria strain, up to 1400 mg/L Cd resistance, was employed and identified as Proteus mirabilis Ch8 (Ch8) through whole genome sequence analyses. The results indicated that the multiple pathways of immobilizing and detoxifying Cd maintained the growth of Ch8 under Cd stress, which also possessed high Cd extracellular adsorption. Firstly, the changes in surface morphology and functional groups of Ch8 cells were observed under different Cd conditions through SEM-EDS and FTIR analyses. Under 100 mg/L Cd, Ch8 cells exhibited aggregation and less flagella; the Cd biosorption of Ch8 was predominately by secreting exopolysaccharides (EPS) and no significant change of functional groups. Under 500 mg/L Cd, Ch8 were present irregular polymers on the cell surface, some cells with wrapping around; the Cd biosorption capacity exhibited outstanding effects (38.80 mg/g), which was mainly immobilizing Cd by secreting and interacting with EPS. Then, Ch8 also significantly enhanced the antioxidant enzyme activity and the antioxidant substance content under different Cd conditions. The activities of SOD and CAT, GSH content of Ch8 under 500 mg/L Cd were significantly increased by 245.47%, 179.52%, and 241.81%, compared to normal condition. Additionally, Ch8 significantly induced the expression of Acr A and Tol C (the resistance-nodulation-division (RND) efflux pump), and some antioxidant genes (SodB, SodC, and Tpx) to reduce Cd damage. In particular, the markedly higher expression levels of SodB under Cd stress. The mechanism of Ch8 lays a foundation for its application in solving soil remediation.

Pharmacokinetic and Pharmacodynamic Analysis of the Oxacephem Antibiotic Flomoxef against Extended-Spectrum ß-Lactamase-Producing Enterobacterales from Dogs.

Flomoxef (FMX) may be a potential alternative to carbapenems for dogs infected with Enterobacterales-producing extended-spectrum ß-lactamase (ESBL-E). However, the appropriate dosage of FMX in dogs with ESBL-E infections has yet to be established. This study was carried out to establish appropriate treatment regimens for FMX against ESBL-E infections in dogs using a pharmacokinetics-pharmacodynamics (PK-PD) approach. Five dogs were intravenously administered at a bolus dose of FMX (40 mg/kg body weight). Serum concentrations of FMX were calculated with high-performance liquid chromatography-tandem mass spectrometry, and then applied to determine PK indices based on a non-compartmental model. The cumulative fraction of response (CFR) was estimated based on the dissemination of minimum inhibitory concentrations among wild-type ESBL-E from companion animals. From the results, the dosage regimens of 40 mg/kg every 6 and 8 h were estimated to attain a CFR of >90% for wild-type isolates of ESBL-producing Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis for dogs. By contrast, all regimens had a CFR of <80% for ESBL-producing Enterobacter cloacae. Our results indicated that dosage regimens of 40 mg/kg FMX every 6 and 8 h can be a non-carbapenem treatment for canine infections of ESBL-producing Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis, but not for those of ESBL-producing Enterobacter cloacae.

Distribution of antimicrobial resistance and virulence markers in chicken originated Proteus mirabilis isolates.

Proteus mirabilis is a common enteric bacterium in livestock and humans. The increase and spread of the antimicrobial resistant P. mirabilis is considered alarming worldwide. Transmission mainly occurs through consumption of contaminated poultry products. We investigated antimicrobial resistance (AMR) and virulence markers in broiler chicken-originated P. mirabilis isolates from 380 fecal samples. Phenotypic AMR test was performed against seventeen different antimicrobials. Genotypic AMR test was performed to detect sixteen different AMR genes. The samples were also tested for the presence of eight different virulence genes and biofilm formation. P. mirabilis was isolated in 11% of the samples, with significantly high multidrug-resistant (MDR) prevalence (63%). All isolates were resistant to tetracycline (100%). The combined disc method indicated that all isolates were of extended-spectrum beta-lactamase (ESBL) producers, which was compatible with the high blaTEM prevalence (95%). This was associated with blaTEM being responsible for more than 80% of ampicillin resistance in enteric pathogens. The absence of phenotypically carbapenem-resistant isolates was compatible with the very low prevalences of blaOXA (2%) and blaNDM (0%). All isolates were positive for pmfA, atfA, hpmA, and zapA (100%) virulence genes, while biofilm formation rate (85%) indicated high adherence abilities of the isolates.

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.