Antimicrobial resistance spectrum and virulence characterization of Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis isolated from asymptomatic and diarrheal rhesus monkeys

This study aims to deepen our understanding of the drug resistance and virulence characterization among gut bacteria in asymptomatic and diarrheal captive rhesus macaques (RMs). A total of 31 samples, including 8 asymptomatic RMs, 10 diarrheal RMs, and 1 dead RM, were collected from a breeding base in Sichuan, China, for bacterial isolation. As a result, Escherichia coli (n = 23), Klebsiella (n = 22), Proteus mirabilis (n = 10), Enterococcus (n = 10), Salmonella (n = 2), and Staphylococcus (n = 2) were isolated. All isolates were subjected to antimicrobial susceptibility testing and whole-genome sequencing, among which some E. coli, K. pneumoniae, and P. mirabilis were subjected to the Galleria mellonella and mice infection testing. The antimicrobial resistance rates of levofloxacin, enrofloxacin, and cefotaxime in diarrhea-associated isolates were higher than those of asymptomatic isolates. Consistent with the antimicrobial resistance phenotype, diarrheal isolates had a higher prevalence rate to qnrS1, blaTEM-1B and blaCTX-M-27 than asymptomatic isolates. Furthermore, compared with asymptomatic isolates, diarrheal isolates demonstrated a higher pathogenic potential against larvae and mice. Additionally, sequence types (STs) 14179-14181 in E. coli and ST 625 and ST 630-631 in Klebsiella aerogenes were firstly characterized. Our evidence underscores the considerable challenge posed by high rates of bacterial drug resistance in the effective treatment of diarrheal RMs.

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.

Molecular identification of Proteus mirabilis, Vibrio species leading to CRISPR-Cas9 modification of tcpA and UreC genes causing cholera and UTI

Heavy metal accumulation increases rapidly in the environment due to anthropogenic activities and industrialization. The leather and surgical industry produces many contaminants containing heavy metals. Cadmium, a prominent contaminant, is linked to severe health risks, notably kidney and liver damage, especially among individuals exposed to contaminated wastewater. This study aims to leverage the natural cadmium resistance mechanisms in bacteria for bioaccumulation purposes. The industrial wastewater samples, characterized by an alarming cadmium concentration of 29.6 ppm, 52 ppm, and 76.4 ppm-far exceeding the recommended limit of 0.003 ppm-were subjected to screening for cadmium-resistant bacteria using cadmium-supplemented media with CdCl2. 16S rRNA characterization identified Vibrio cholerae and Proteus mirabilis as cadmium-resistant bacteria in the collected samples. Subsequently, the cadmium resistance-associated cadA gene was successfully amplified in Vibrio species and Proteus mirabilis, revealing a product size of 623 bp. Further analysis of the identified bacteria included the examination of virulent genes, specifically the tcpA gene (472 bp) associated with cholera and the UreC gene (317 bp) linked to urinary tract infections. To enhance the bioaccumulation of cadmium, the study proposes the potential suppression of virulent gene expression through in-silico gene-editing tools such as CRISPR-Cas9. A total of 27 gRNAs were generated for UreC, with five selected for expression. Similarly, 42 gRNA sequences were generated for tcpA, with eight chosen for expression analysis. The selected gRNAs were integrated into the lentiCRISPR v2 expression vector. This strategic approach aims to facilitate precise gene editing of disease-causing genes (tcpA and UreC) within the bacterial genome. In conclusion, this study underscores the potential utility of Vibrio species and Proteus mirabilis as effective candidates for the removal of cadmium from industrial wastewater, offering insights for future environmental remediation strategies.

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.

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-β-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".

Transcriptomic analysis of skin immunity genes in the Chinese spiny frog (Quasipaa spinosa) after Proteus mirabilis infection

Recently, populations of Chinese spiny frogs (Quasipaa spinosa), an important amphibian species in China, have decreased, mainly due to a disease caused by the gram-negative bacteria Proteus mirabilis. To elucidate the immune response of the frogs, this study aimed to identify novel candidate genes functionally associated with P. mirabilis infection-induced "rotting skin" disease. Chinese spiny frogs were infected with P. mirabilis, and the skin transcriptome was sequenced using the MGISEQ-2000 platform. A total of 233,965 unigenes were obtained by sequencing, of which 27.23 % were known genes. Screening of differentially expressed genes (DEGs) indicated 210 unigenes differentially expressed after P. mirabilis infection, of which 132 unigenes were up-regulated, and 78 unigenes were down-regulated. Using Kyoto Encyclopedia of Genes and Genomes enrichment analysis, DEGs were identified as enriched in signal pathways, such as oxidative phosphorylation, apoptosis, and the Janus kinase-signal transducer and activator of transcription pathway. Of the DEGs, there was a significant upregulation of the colony stimulating factor 2 receptor beta common subunit, interleukin 2 receptor subunit gamma, cathelicidin antimicrobial peptide, interleukin-17 receptor E, receptor-interacting serine/threonine-protein kinase 3, and pulmonary surfactant-associated protein D immune genes following P. mirabilis infection. Conversely, scavenger receptor cysteine-rich domain-containing group B protein, tumor protein p53 inducible nuclear protein 2, suppressor of cytokine signaling 2, and metalloreductase STEAP3 were significantly downregulated. In conclusion, the first skin transcriptome database of Chinese spiny frogs was established, and several immune genes were identified to elucidate the pathogenic mechanism of "skin rot" in Chinese spiny frogs and other cultured frogs.

Antibiotic resistance and virulence profiles of Proteus mirabilis isolated from broiler chickens at abattoir in South Africa

BACKGROUND

Proteus mirabilis has been identified as an important zoonotic pathogen, causing several illnesses such as diarrhoea, keratitis and urinary tract infections.

OBJECTIVE

This study assessed the prevalence of P. mirabilis in broiler chickens, its antibiotic resistance (AR) patterns, ESBL-producing P. mirabilis and the presence of virulence genes.

METHODS

A total of 26 isolates were confirmed as P. mirabilis from 480 pooled broiler chicken faecal samples by polymerase chain reaction (PCR). The disk diffusion method was used to evaluate the antibacterial susceptibility test, while nine virulence genes and 26 AR genes were also screened by PCR.

RESULTS

All 26 P. mirabilis isolates harboured the ireA (siderophore receptors), ptA, and zapA (proteases), ucaA, pmfA, atfA, and mrpA (fimbriae), hlyA and hpmA (haemolysins) virulence genes. The P. mirabilis isolates were resistant to ciprofloxacin (62%) and levofloxacin (54%), while 8 (30.7%) of the isolates were classified as multidrug resistant (MDR). PCR analysis identified the blaCTX-M gene (62%), blaTEM (58%) and blaCTX-M-2 (38%). Further screening for AMR genes identified mcr-1, cat1, cat2, qnrA, qnrD and mecA, 12%, 19%, 12%, 54%, 27% and 8%, respectively for P. mirabilis isolates. The prevalence of the integron integrase intI1 and intI2 genes was 43% and 4%, respectively.

CONCLUSIONS

The rise of ciprofloxacin and levofloxacin resistance, as well as MDR strains, is a public health threat that points to a challenge in the treatment of infections caused by these zoonotic bacteria. Furthermore, because ESBL-producing P. mirabilis has the potential to spread to humans, the presence of blaCTX -M -producing P. mirabilis in broilers should be kept under control. This is the first study undertaken to isolate P. mirabilis from chicken faecal samples and investigate its antibiotic resistance status as well as virulence profiles in South Africa.

Key biological processes and essential genes for Proteus mirabilis biofilm development inhibition by protocatechuic acid

Proteus mirabilis is an opportunistic pathogen linked to human urinary tract infections, and is potentially present as a foodborne pathogen within poultry products, including broiler chickens. This report outlines the inhibitory impacts of protocatechuic acid (PCA) on P. mirabilis isolated from a broiler slaughterhouse in China as well as its biofilm. This investigation encompasses assays related to motility and adhesion, bacterial metabolic activity, extracellular polymer (EPS) production, and scavenging capacity. The findings demonstrated that PCA reduced biofilm formation by 61 %. Transcriptomics findings identified that PCA limited the expression of genes like PstS that promote adhesin formation, rbsA and RcsB that alter bacterial chemotaxis, lipopolysaccharide synthesis genes LpxA and EptB, and cell wall synthesis genes MurF and MrdA, and affects the Regulator of Capsule Synthesis (RCS) two-component modulation system. Weighted gene co-expression network analysis (WGCNA) was conducted to identify the core genes. Furthermore, the binding sites of PCA to cytochrome oxidases cydA and cydB, two subunits of ATP synthase atpI and atpH, and ftsZ, which regulate bacterial division, were predicted via molecular docking. Metabolome analysis determined that PCA critically influenced coenzyme A biosynthesis, nucleotide metabolism, alanine, aspartic acid, and glutamate metabolic pathways of P. mirabilis. Therefore, PCA impacts metabolism within bacteria via various pathways, limiting the levels of extracellular polymer and bacterial viability to hinder biofilm formation. Additionally, we prepared an antibacterial plastic film containing protocatechuic acid using PVA as the monomer and CNC as the reinforcing agent. We examined the mechanical and antibacterial properties of this film. When used to wrap chicken, it reduced the total number of colonies, slowed the deterioration of chicken, and maintained the freshness of chicken. In conclusion, the information outlined in this study complements our comprehension of P. mirabilis inhibition by PCA and provides clues for the reduction of foodborne infections associated with P. mirabilis.

Characterization and risk assessment of novel SXT/R391 integrative and conjugative elements with multidrug resistance in Proteus mirabilis isolated from China, 2018-2020

Proteus mirabilis can transfer transposons, insertion sequences, and gene cassettes to the chromosomes of other hosts through SXT/R391 integrative and conjugative elements (ICEs), significantly increasing the possibility of antibiotic resistance gene (ARG) evolution and expanding the risk of ARGs transmission among bacteria. A total of 103 strains of P. mirabilis were isolated from 25 farms in China from 2018 to 2020. The positive detection rate of SXT/R391 ICEs was 25.2% (26/103). All SXT/R391 ICEs positive P. mirabilis exhibited a high level of overall drug resistance. Conjugation experiments showed that all 26 SXT/R391 ICEs could efficiently transfer to Escherichia coli EC600 with a frequency of 2.0 × 10-7 to 6.0 × 10-5. The acquired ARGs, genetic structures, homology relationships, and conservation sequences of 26 (19 different subtypes) SXT/R391 ICEs were investigated by high-throughput sequencing, whole-genome typing, and phylogenetic tree construction. ICEPmiChnHBRJC2 carries erm (42), which have never been found within an SXT/R391 ICE in P. mirabilis, and ICEPmiChnSC1111 carries 19 ARGs, including clinically important cfr, blaCTX-M-65, and aac(6')-Ib-cr, making it the ICE with the most ARGs reported to date. Through genetic stability, growth curve, and competition experiments, it was found that the transconjugant of ICEPmiChnSCNNC12 did not have a significant fitness cost on the recipient bacterium EC600 and may have a higher risk of transmission and dissemination. Although the transconjugant of ICEPmiChnSCSZC20 had a relatively obvious fitness cost on EC600, long-term resistance selection pressure may improve bacterial fitness through compensatory adaptation, providing scientific evidence for risk assessment of horizontal transfer and dissemination of SXT/R391 ICEs in P. mirabilis.IMPORTANCEThe spread of antibiotic resistance genes (ARGs) is a major public health concern. The study investigated the prevalence and genetic diversity of integrative and conjugative elements (ICEs) in Proteus mirabilis, which can transfer ARGs to other hosts. The study found that all of the P. mirabilis strains carrying ICEs exhibited a high level of drug resistance and a higher risk of transmission and dissemination of ARGs. The analysis of novel multidrug-resistant ICEs highlighted the potential for the evolution and spread of novel resistance mechanisms. These findings emphasize the importance of monitoring the spread of ICEs carrying ARGs and the urgent need for effective strategies to combat antibiotic resistance. Understanding the genetic diversity and potential for transmission of ARGs among bacteria is crucial for developing targeted interventions to mitigate the threat of antibiotic resistance.

Three separate acquisitions of blaNDM-1 in three different bacterial species from a single patient

To investigate the acquisition and relatedness of New Delhi Metallo-beta-lactamase among multiple separate species from one patient. Five isolates from three species (Pseudomonas aeruginosa; Pa, Acinetobacter baumannii; Ab and Proteus mirabilis; Pm) suspected of harbouring a carbapenemase were investigated by phenotype (antimicrobial susceptibilities) and whole genome sequencing. Epidemiological data was collected on this patient. Three different carbapenemase genes were detected; blaVIM-1 (Pa; ST773), blaOXA-23 (Ab, ST499) and blaNDM-1 identified in all isolates. NDM regions were found chromosomally integrated in all isolates. Data showed no evidence of NDM-1 transfer within this patient suggesting the enzyme was acquired in three separate events.

Uncharacterized and lineage-specific accessory genes within the Proteus mirabilis pan-genome landscape

Proteus mirabilis is a Gram-negative bacterium recognized for its unique swarming motility and urease activity. A previous proteomic report on four strains hypothesized that, unlike other Gram-negative bacteria, P. mirabilis may not exhibit significant intraspecies variation in gene content. However, there has not been a comprehensive analysis of large numbers of P. mirabilis genomes from various sources to support or refute this hypothesis. We performed comparative genomic analysis on 2,060 Proteus genomes. We sequenced the genomes of 893 isolates recovered from clinical specimens from three large US academic medical centers, combined with 1,006 genomes from NCBI Assembly and 161 genomes assembled from Illumina reads in the public domain. We used average nucleotide identity (ANI) to delineate species and subspecies, core genome phylogenetic analysis to identify clusters of highly related P. mirabilis genomes, and pan-genome annotation to identify genes of interest not present in the model P. mirabilis strain HI4320. Within our cohort, Proteus is composed of 10 named species and 5 uncharacterized genomospecies. P. mirabilis can be subdivided into three subspecies; subspecies 1 represented 96.7% (1,822/1,883) of all genomes. The P. mirabilis pan-genome includes 15,399 genes outside of HI4320, and 34.3% (5,282/15,399) of these genes have no putative assigned function. Subspecies 1 is composed of several highly related clonal groups. Prophages and gene clusters encoding putatively extracellular-facing proteins are associated with clonal groups. Uncharacterized genes not present in the model strain P. mirabilis HI4320 but with homology to known virulence-associated operons can be identified within the pan-genome. IMPORTANCE Gram-negative bacteria use a variety of extracellular facing factors to interact with eukaryotic hosts. Due to intraspecies genetic variability, these factors may not be present in the model strain for a given organism, potentially providing incomplete understanding of host-microbial interactions. In contrast to previous reports on P. mirabilis, but similar to other Gram-negative bacteria, P. mirabilis has a mosaic genome with a linkage between phylogenetic position and accessory genome content. P. mirabilis encodes a variety of genes that may impact host-microbe dynamics beyond what is represented in the model strain HI4320. The diverse, whole-genome characterized strain bank from this work can be used in conjunction with reverse genetic and infection models to better understand the impact of accessory genome content on bacterial physiology and pathogenesis of infection.

Genetic analysis of resistance and virulence characteristics of clinical multidrug-resistant Proteus mirabilis isolates

Objective

Proteus mirabilis is the one of most important pathogens of catheter-associated urinary tract infections. The emergence of multidrug-resistant (MDR) P. mirabilis severely limits antibiotic treatments, which poses a public health risk. This study aims to investigate the resistance characteristics and virulence potential for a collection of P. mirabilis clinical isolates.

Methods and results

Antibiotic susceptibility testing revealed fourteen MDR strains, which showed high resistance to most β-lactams and trimethoprim/sulfamethoxazole, and a lesser extent to quinolones. All the MDR strains were sensitive to carbapenems (except imipenem), ceftazidime, and amikacin, and most of them were also sensitive to aminoglycosides. The obtained MDR isolates were sequenced using an Illumina HiSeq. The core genome-based phylogenetic tree reveals the high genetic diversity of these MDR P. mirabilis isolates and highlights the possibility of clonal spread of them across China. Mobile genetic elements SXT/R391 ICEs were commonly (10/14) detected in these MDR P. mirabilis strains, whereas the presence of resistance island PmGRI1 and plasmid was sporadic. All ICEs except for ICEPmiChn31006 carried abundant antimicrobial resistance genes (ARGs) in the HS4 region, including the extended-spectrum β-lactamase (ESBL) gene blaCTX-M-65. ICEPmiChn31006 contained the sole ARG blaCMY-2 and was nearly identical to the global epidemic ICEPmiJpn1. The findings highlight the important roles of ICEs in mediating the spread of ARGs in P. mirabilis strains. Additionally, these MDR P. mirabilis strains have great virulence potential as they exhibited significant virulence-related phenotypes including strong crystalline biofilm, hemolysis, urease production, and robust swarming motility, and harbored abundant virulence genes.

Conclusion

In conclusion, the prevalence of MDR P. mirabilis with high virulence potential poses an urgent threat to public health. Intensive monitoring is needed to reduce the incidence of infections by MDR P. mirabilis.

Characterization of Proteus mirabilis and associated plasmids isolated from anaerobic dairy cattle manure digesters

Proteus mirabilis is an opportunistic pathogen associated with a variety of human infections, including urinary tract infections. The prevalence of P. mirabilis in foods of animal origin and in the manure by-products created in animal production is not well documented. Further, the prevalence and persistence of extended-spectrum cephalosporin (ESC) resistant P. mirabilis is largely unknown. In this study, we characterized ESC-resistant P. mirabilis recovered from various stages of dairy manure anaerobic digestion. Isolates were screened by PCR for blaCTX-M, blaCMY and blaSHV, and antimicrobial susceptibility testing was performed. Fifty-six P. mirabilis carrying CTX-M were sequenced with short and long read sequencing technologies, and the assembled chromosomes and plasmids were compared. ESC-resistant Proteus was found in four of the six manure digesters, an indication that not all digesters were colonized with resistant strains. Both CTX-M-1 and CTX-M-15 plasmids were found in P. mirabilis isolates. Transfer of plasmid DNA by conjugation was also explored, with ESC-resistance plasmids able to transfer to Escherichia coli at high frequency. We concluded that P. mirabilis can harbour and transfer ESC-resistance genes and plasmids, and may be an overlooked reservoir of antimicrobial resistance.

Isolation, biological and whole genome characteristics of a Proteus mirabilis bacteriophage strain

Proteus mirabilis, a naturally resistant zoonotic bacterium belonging to the Enterobacteriaceae family, has exhibited an alarming increase in drug resistance. Consequently, there is an urgent need to explore alternative antimicrobial agents. Bacteriophages, viruses that selectively target bacteria, are abundant in the natural environment and have demonstrated potential as a promising alternative to antibiotics. In this study, we successfully isolated four strains of Proteus mirabilis phages from sewage obtained from a chicken farm in Sichuan, China. Subsequently, we characterized one of the most potent lytic phages, Q29, by examining its biological and genomic features. Comparative genomic analysis revealed the functional genes and phylogenetic evolution of Q29 phages. Our findings revealed that Proteus mirabilis bacteriophage Q29 possesses an icosahedral symmetrical head with a diameter of 95 nm and a tail length of 240 nm. Moreover, phage Q29 exhibited stability within a temperature range of 37 ℃ to 55 ℃ and under pH conditions ranging from 4 to 9. The optimal multiplicity of infection (MOI) for this phage was determined to be 0.001. Furthermore, the one-step growth curve results indicated an incubation period of approximately 15 min, an outbreak period of approximately 35 min, and an average cleavage quantity of approximately 60 plaque-forming units (PFU) per cell. The genome of phage Q29 was found to have a total length of 58,664 base pairs and encoded 335 open reading frames (ORFs) without carrying any antibiotic resistance genes. Additionally, genetic evolutionary analysis classified phage Q29 within the family Caudalidae and the genus Myotail. This study provides valuable research material for further development of Proteus mirabilis bacteriophage biologics as promising alternatives to antibiotics, particularly in light of the growing challenge of antibiotic resistance posed by this bacterium.

Molecular Analysis of Virulence Genes HpmB and rsbA among proteus Species Isolated from Different Infectious Cases in Iraq

Proteus species (spp.) is considered one of the widely spread pathogens worldwide. Proteus spp. can be detected in contaminated water, soil, and manure, aiding the decomposition of organic substances from animals. Proteus is a gram-negative bacterium that causes a wide range of human illnesses. This study aimed to find some virulence genes in Proteus spp. from different sources, including the laboratories of government hospitals in Karbala, Al-Hussies, and Al-Muthanna, Iraq. Fifty swab samples were collected from patients' wounds, ears, and sputum. Clinicians collected swab samples for identification. In total, 17 sputum samples, 13 ear samples, and 20 wound samples were collected from 27 (54%) females and 23 (46%) males. The virulence genes hpmB and rsbA were identified after the genomic diagnosis of Proteus spp. Thirteen Proteus isolates were identified using the hpmB primer, and 16 isolates were identified using the rsbA primer. The DNA sequence analysis of rsbA and hpmB genes revealed that all samples shared 99.52% identity for the rsbA gene, whereas the hpmB gene differed from one sample to the next. The sequence results are available at the NCBI under the accession numbers (LC661938) and (LC661939), respectively.

Genomes comparison of two Proteus mirabilis clones showing varied swarming ability

BACKGROUND

Proteus mirabilis is a Gram-negative bacteria most noted for its involvement with catheter-associated urinary tract infections. It is also known for its multicellular migration over solid surfaces, referred to as 'swarming motility'. Here we analyzed the genomic sequences of two P. mirabilis isolates, designated K38 and K39, which exhibit varied swarming ability.

METHODS AND RESULTS

The isolates genomes were sequenced using Illumina NextSeq sequencer, resulting in about 3.94 Mbp, with a GC content of 38.6%, genomes. Genomes were subjected for in silico comparative investigation. We revealed that, despite a difference in swarming motility, the isolates showed high genomic relatedness (up to 100% ANI similarity), suggesting that one of the isolates probably originated from the other.

CONCLUSIONS

The genomic sequences will allow us to investigate the mechanism driving this intriguing phenotypic heterogeneity between closely related P. mirabilis isolates. Phenotypic heterogeneity is an adaptive strategy of bacterial cells to several environmental pressures. It is also an important factor related to their pathogenesis. Therefore, the availability of these genomic sequences will facilitate studies that focus on the host-pathogen interactions during catheter-associated urinary tract infections.

A Core Genome Multilocus Sequence Typing Scheme for Proteus mirabilis

OBJECTIVE

A core genome multilocus sequence typing (cgMLST) scheme to genotype and identify potential risk clonal groups (CGs) in Proteus mirabilis.

METHODS

In this work, we propose a publicly available cgMLST scheme for P. mirabilis using chewBBACA. In total 72 complete P. mirabilis genomes, representing the diversity of this species, were used to set up a cgMLST scheme targeting 1,842 genes, 635 unfinished (contig, chromosome, and scaffold) genomes were used for its validation.

RESULTS

We identified a total of 205 CGs from 695 P. mirabilis strains with regional distribution characteristics. Of these, 159 unique CGs were distributed in 16 countries. CG20 and CG3 carried large numbers of shared and unique antibiotic resistance genes. Nine virulence genes ( papC, papD, papE, papF, papG, papH, papI, papJ, and papK) related to the P fimbrial operon that cause severe urinary tract infections were only found in CG20. These CGs require attention due to potential risks.

CONCLUSION

This research innovatively performs high-resolution molecular typing of P. mirabilis using whole-genome sequencing technology combined with a bioinformatics pipeline (chewBBACA). We found that the CGs of P. mirabilis showed regional distribution differences. We expect that our research will contribute to the establishment of cgMLST for P. mirabilis.

Characterization, genome analysis and antibiofilm efficacy of lytic Proteus phages RP6 and RP7 isolated from university hospital sewage

The crystalline formation of biofilms by Proteus blocks the urine flow which often complicates the health care of catheterized patients. Bacteriophages has been highlighted as a promising tool to control biofilm-mediated bacterial infections. Here, we isolated and characterized two newly isolated lytic phages capable of infecting clinical isolates of P. mirabilis and P. vulgaris. Moreover, insights regarding the biological and molecular characterization were analysed. Both RP6 and RP7 phages showed a Proteus-genus-specific profile, administering no lytic activity against other family of Enterobacteriaceae. The optimal MOI value of the RP6 and RP7 phages were determined as 0.1 and 0.01, respectively. The one-step growth curve showed that RP6 and RP7 phages have a short latent period of 20 min and large burst size of 220-371 PFU/ML per infected host cell. Bacteria growth was reduced immediately after the phages were added, which is shown by the optical density (OD) measurement after 24 hr. Proteus phage RP6 and RP7 were found to eradicate both the planktonic and mature biofilms produced by the Proteus isolates tested. Genome sequence of Proteus phage RP6 was found to be 58,619 bp, and a G-C content of 47%. Also, Proteus phage RP7 genome size was 103,593 bp with G-C ratio of 38.45%. A total of 70 and 172 open reading frame (ORF) was encoded in RP6 and RP7 phage genomes, respectively. Interestingly, there were no tRNA encoded by Proteus phage RP6 genome even though there is a significant G-C content difference between the phage and its host. Additionally, the exhibition of highly lytic activity and absence of virulence and antibiotic-resistant genes in both Proteus RP6 and RP7 phages emphasized that this newly isolated phages are promising for potential therapeutic phages.

Evaluation of antibiotic resistance in Proteus spp: a growing trend that worries Public Health. Results of 10 Years of Analysis

The genus Proteus includes several species among which Proteus mirabilis is by far the most commonly detected in clinical specimens. In the last twenty years, isolates with multiple acquired resistance genes have been detected, especially in the hospital environment, with a significant impact on the treatment of infections. This research is a ten-year cross-sectional study reporting the detection rates and the antibiotic susceptibility of Proteus spp. in clinical specimens from a healthcare setting in Southern Italy. Of all the 1,600 clinical samples sent to the laboratory, 4.4% were positive to Proteus spp., with P. mirabilis by far the most detected one (83.1%), especially in lower limb ulcers and urines. Moreover, we noted a significant increase of 1200% in the detection rate from 2011 to 2020. Finally, we reported a significant and constantly increasing trend in the detection of antibiotic-resistant strains, ranging from 48.4% in 2011 to 74% in 2020. Our results highlight a clear and significant increase in Proteus spp. detection in a typical hospital setting with a parallel increase in the detection of antibiotic-resistant strains. Therefore, Proteus spp. can be considered one of the main emerging pathogenic bacteria in the hospital environment.

A Phage Cocktail To Control Surface Colonization by Proteus mirabilis in Catheter-Associated Urinary Tract Infections

Proteus mirabilis is a biofilm-forming bacterium and one of the most common causes of catheter-associated urinary tract infections (CAUTIs). The rapid spread of multidrug-resistant P. mirabilis represents a severe threat to management of nosocomial infections. This study aimed to isolate a potent phage cocktail and assess its potential to control urinary tract infections caused by biofilm-forming P. mirabilis. Two lytic phages, Isf-Pm1 and Isf-Pm2, were isolated and characterized by proteome analysis, transmission electron microscopy, and whole-genome sequencing. The host range and effect of the phage cocktail to reduce the biofilm formation were assessed by a cell adhesion assay in Vero cells and a phantom bladder model. The samples treated with the phage cocktail showed a significant reduction (65%) in the biofilm mass. Anti-quorum sensing and quantitative real-time PCR assays were also used to assess the amounts of transcription of genes involved in quorum sensing and biofilm formation. Furthermore, the phage-treated samples showed a downregulation of genes involved in the biofilm formation. In conclusion, these results highlight the efficacy of two isolated phages to control the biofilms produced by P. mirabilis CAUTIs. IMPORTANCE The rapid spread of multidrug-resistant (MDR) and extensively drug-resistant (XDR) bacterial strains and biofilm formation of bacteria have severely restricted the use of antibiotics and become a challenging issue in hospitals. Therefore, there is a necessity for alternative or complementary treatment measures, such as the use of virulent bacteriophages (phages), as effective therapeutic strategies.

Augmented Enterocyte Damage During Candida albicans and Proteus mirabilis Coinfection

The human gut acts as the main reservoir of microbes and a relevant source of life-threatening infections, especially in immunocompromised patients. There, the opportunistic fungal pathogen Candida albicans adapts to the host environment and additionally interacts with residing bacteria. We investigated fungal-bacterial interactions by coinfecting enterocytes with the yeast Candida albicans and the Gram-negative bacterium Proteus mirabilis resulting in enhanced host cell damage. This synergistic effect was conserved across different P. mirabilis isolates and occurred also with non-albicans Candida species and C. albicans mutants defective in filamentation or candidalysin production. Using bacterial deletion mutants, we identified the P. mirabilis hemolysin HpmA to be the key effector for host cell destruction. Spatially separated coinfections demonstrated that synergism between Candida and Proteus is induced by contact, but also by soluble factors. Specifically, we identified Candida-mediated glucose consumption and farnesol production as potential triggers for Proteus virulence. In summary, our study demonstrates that coinfection of enterocytes with C. albicans and P. mirabilis can result in increased host cell damage which is mediated by bacterial virulence factors as a result of fungal niche modification via nutrient consumption and production of soluble factors. This supports the notion that certain fungal-bacterial combinations have the potential to result in enhanced virulence in niches such as the gut and might therefore promote translocation and dissemination.

[Improving the thermal stability of Proteus mirabilis lipase based on multiple computational design strategies]

Proteus mirabilis lipase (PML) features tolerance to organic solvents and great potential for biodiesel synthesis. However, the thermal stability of the enzyme needs to be improved before it can be used industrially. Various computational design strategies are emerging methods for the modification of enzyme thermal stability. In this paper, the complementary algorithm-based ABACUS, PROSS, and FoldX were employed for positive selection of PML mutations, and their pairwise intersections were further subjected to negative selection by PSSM and G_REMLIN to narrow the mutation library. Thereby, 18 potential single-point mutants were screened out. According to experimental verification, 7 mutants had melting temperature (T_m) improved, and the ΔT_m of K208G and G206D was the highest, which was 3.75 ℃ and 3.21 ℃, respectively. Five mutants with activity higher than the wild type (WT) were selected for combination by greedy accumulation. Finally, the T_m of the five-point combination mutant M10 increased by 10.63 ℃, and the relative activity was 140% that of the WT. K208G and G206D exhibited certain epistasis during the combination, which made a major contribution to the improvement of the thermal stability of M10. Molecular dynamics simulation indicated that new forces were generated at and around the mutation sites, and the rearrangement of forces near G206D/K208G might stabilize the Ca²⁺ binding site which played a key role in the stabilization of PML. This study provides an efficient and user-friendly computational design scheme for the thermal stability modification of natural enzymes and lays a foundation for the modification of PML and the expansion of its industrial applications.

The QseEF Two-Component System-GlmY Small RNA Regulatory Pathway Controls Swarming in Uropathogenic Proteus mirabilis

Bacterial sensing of environmental signals through the two-component system (TCS) plays a key role in modulating virulence. In the search for the host hormone-sensing TCS, we identified a conserved qseEGF locus following glmY, a small RNA (sRNA) gene in uropathogenic Proteus mirabilis. Genes of glmY-qseE-qseG-qseF constitute an operon, and QseF binding sites were found in the glmY promoter region. Deletion of glmY or qseF resulted in reduced swarming motility and swarming-related phenotypes relative to the wild-type and the respective complemented strains. The qseF mutant had decreased glmYqseEGF promoter activity. Both glmY and qseF mutants exhibited decreased flhDC promoter activity and mRNA level, while increased rcsB mRNA level was observed in both mutants. Prediction by TargetRNA2 revealed cheA as the target of GlmY. Then, construction of the translational fusions containing various lengths of cheA 5′UTR for reporter assay and site-directed mutagenesis were performed to investigate the cheA-GlmY interaction in cheA activation. Notably, loss of glmY reduced the cheA mRNA level, and urea could inhibit swarming in a QseF-dependent manner. Altogether, this is the first report elucidating the underlying mechanisms for modulation of swarming motility by a QseEF-regulated sRNA GlmY, involving expression of cheA, rcsB and flhDC in uropathogenic P. mirabilis.

Virulence genes and antimicrobial resistance pattern in Proteus mirabilis strains isolated from patients attended with urinary infections to Tertiary Hospitals, in Iran

Background

Proteus mirabilis is a frequent reason for catheter-associated urinary tract infections (UTIs). The aim of this study was to identify virulence genes and antimicrobial resistance patterns in P. mirabilis strains isolated from patients who attended a tertiary hospital in Iran.

Methods

In this study, 100 P. mirabilis strains from urine samples were isolated. These isolated strains were identified by biochemical and PCR-based tests, and their antibiotic resistance was profiled through a standard procedure using 14 antibiotics. PCR assays were used to detect virulence-related genes in P. mirabilis strains. The biofilm formation of each P. mirabilis strain was examined.

Results

Of the 100 P. mirabilis isolates, 16 (16%) were multidrug-resistant. High resistance was observed against cotrimoxazole (97%), nalidixic acid (93%), cefotaxime (77%), and amoxicillin (62%). Sixty of the 100 isolates showed resistance against extended-spectrum cephalosporins. The prevalence rates of the genes related to the virulence factors in this study were mrpH (100%), ucaA (91%), hpmA (94%), zapA (95%), ptaA (100%), ureG (100%), pmfA (100%), fliC (97%), and mrpA (90%) using PCR method. Strong biofilm formation was observed in 20% (5/25) of the strains isolated from non-catheterized samples and 80% (20/25) of strains isolated from catheterized samples.

Conclusions

Resistance to antibiotics and the prevalence of pathogenicity genes are high in Proteus mirabilis strains iolated from UTIs.

Comparison of swab types for collection and analysis of microorganisms

The human microbiome has begun to emerge as a potential forensic tool, with varied applications ranging from unique identification to investigative leads that link individuals and/or locations. The relative abundance of the combined DNA of the microbiome, compared to human nuclear DNA, may expand potential sources of biological evidence, especially in cases with transfer or low-copy number DNA samples. This work sought to determine the optimal swab type for the collection and analysis of microorganisms. A bacterium (Proteus mirabilis) was deposited by pipette onto four swab types (cotton, flocked, dental applicators, and dissolvable), and extraction and real-time PCR quantitation of the bacterial DNA were performed, which allowed for absolute microbial DNA recovery and comparison of yields across the four sampling substrates. Flocked swabs had the highest yield (~1240 ng) compared to the cotton swabs (~184 ng), dental applicators (~533 ng), and dissolvable swabs (~430 ng). The collection efficiency was further evaluated for cotton and flocked swabs using dried microbial samples spotted onto non-porous surfaces (treated wood, glass, plastic, and tile). Flocked swabs performed consistently better across wood, glass, and tile, but showed decreased recovery from plastic. The cotton swabs failed in the recovery of P. mirabilis DNA across all surfaces. Knowing the appropriate sampling substrate will be useful as others continue to investigate the use of the microbiome as a forensics tool.

Whole genome sequence of a New Delhi metallo-β-lactamase 1-producing Proteus mirabilis isolate SNYG35 from broiler chicken in China

OBJECTIVES

The global spread of the New Delhi metallo-β-lactamase 1 (NDM-1) gene poses a significant challenge to worldwide public health. Here, we characterize the whole genome of NDM-1-producing Proteus mirabilis isolate SNYG35 of broiler chicken origin in China.

METHODS

The genome of SNYG35 was sequenced using a PacBio RS II sequencing instrument and Illumina HiSeq platform. SMRT cell data were assembled independently using HGAP4 and Canu v1.6, and were further polished with Illumina data using Pilon v1.22. The presence of antimicrobial resistance genes was identified using CGE ResFinder 3.2. A conjugation experiment was performed using the sodium azide-resistant Escherichia coli J53Azi^R strain as the recipient.

RESULTS

The chromosome of SNYG35 is 4 014 504 bp in size and consists of one chromosome and one plasmid named pSNYG35. It contains 3646 coding sequences, 82 tRNA genes, 22 rRNAs, and four non-coding RNAs. Besides bla_NDM-1, SNYG35 harbours 26 different antimicrobial resistance genes including ESBL gene bla_CTX-M-65 as well as fluoroquinolone and aminoglycoside resistance gene aac(6')-Ib-cr. The bla_NDM-1-harbouring pSNYG35 is a pPrY2001-like plasmid and shares highest nucleotide identity to pHFK418-NDM. It carries a Tn1696-like multidrug-resistant region harbouring 12 different antimicrobial resistance genes, and could be transferred to E. coli J53.

CONCLUSIONS

Here, we report for the first time the whole genome sequence of a NDM-1-producing P. mirabilis isolate from broiler chicken in China, which provides valuable information for tracing the potential transmission of NDM-1-producing P. mirabilis from broiler chicken to humans, as well as revealing the spread and evolution of bla_NDM-1-harbouring pPrY2001-like plasmids.

Cointegration as a mechanism for the evolution of a KPC-producing multidrug resistance plasmid in Proteus mirabilis

The incidence and transmission of Klebsiella pneumoniae carbapenemase (KPC) producing plasmids have been well documented. However, the evolutionary dynamics of KPC plasmids and their fitness costs are not well characterized. Here, two carbapenemase-producing plasmids from Proteus mirabilis, pT18 and pT211 (both carrying bla KPC-2), were characterized through whole genome sequencing. pT211 is a 24.2 kbp N-type plasmid that contains bla KPC-2 and a single copy of the IS6-family insertion sequence IS26. pT18 is a 59 kbp cointegrate plasmid comprised of sequences derived from three different plasmids: a close relative of pT211 (containing bla KPC-2), an FII-33 plasmid (bla TEM-1B, bla CTX-M-65, rmtB and fosA3) and a rolling-circle plasmid. The segments of pT18 derived from each of the different plasmids are separated by copies of IS26, and sequence analysis indicated that pT18 was likely generated by both conservative and replicative IS26-mediated cointegrate formation. pT18 and pT211 were transferred into Escherichia coli DH5α separately to assess the impact of plasmids on host fitness. Only DH5α harbouring pT18 grew slower than the wild type in antibiotic-free media. However, in sub-inhibitory concentrations of fosfomycin and amikacin, cells containing pT18 grew faster than the wild type, and the minimum concentrations of fosfomycin and amikacin required to observe an advantage for plasmid-carrying cells were 1/3 and 1/20 the DH5α MIC, respectively. This study highlights the importance of the role of cointegrate plasmids in the dissemination of antibiotic resistance genes between pathogenic bacterial species, and highlights the importance of sub-inhibitory concentrations of antibiotics to the persistence of such plasmids.

Biotransformation and chiral resolution of d,l-alanine into pyruvate and d-alanine with a whole-cell biocatalyst expressing l-amino acid deaminase

Pyruvate is an important pharmaceutical intermediate and is widely used in food, nutraceuticals, and pharmaceuticals. However, high environmental pollution caused by chemical synthesis or complex separation process of microbial fermentation methods constrain the supply of pyruvate. Here, one-step pyruvate and d-alanine production from d,l-alanine by whole-cell biocatalysis was investigated. First, l-amino acid deaminase (Pm1) from Proteus mirabilis was expressed in Escherichia coli, resulting in pyruvate titer of 12.01 g/L. Then, N-terminal coding sequences were introduced to the 5'-end of the pm1 gene to enhance the expression of Pm1 and the pyruvate titer increased to 15.13 g/L. Next, product utilization by the biocatalyst was prevented by knocking out the pyruvate uptake transporters (cstA, btsT) and the pyruvate metabolic pathway genes pps, poxB, pflB, ldhA, and aceEF using CRISPR/Cas9, yielding 30.88 g/L pyruvate titer. Finally, by optimizing the reaction conditions, the pyruvate titer was further enhanced to 43.50 g/L in 8 H with a 79.99% l-alanine conversion rate; meanwhile, the resolution of d-alanine reached 84.0%. This work developed a whole-cell biocatalyst E. coli strain for high-yield, high-efficiency, and low-pollution pyruvate and d-alanine production, which has great potential for the commercial application in the future.

MrpH, a new class of metal-binding adhesin, requires zinc to mediate biofilm formation

Proteus mirabilis, a Gram-negative uropathogen, is a major causative agent in catheter-associated urinary tract infections (CAUTI). Mannose-resistant Proteus-like fimbriae (MR/P) are crucially important for P. mirabilis infectivity and are required for biofilm formation and auto-aggregation, as well as for bladder and kidney colonization. Here, the X-ray crystal structure of the MR/P tip adhesin, MrpH, is reported. The structure has a fold not previously described and contains a transition metal center with Zn²⁺ coordinated by three conserved histidine residues and a ligand. Using biofilm assays, chelation, metal complementation, and site-directed mutagenesis of the three histidines, we show that an intact metal binding site occupied by zinc is essential for MR/P fimbria-mediated biofilm formation, and furthermore, that P. mirabilis biofilm formation is reversible in a zinc-dependent manner. Zinc is also required for MR/P-dependent agglutination of erythrocytes, and mutation of the metal binding site renders P. mirabilis unfit in a mouse model of UTI. The studies presented here provide important clues as to the mechanism of MR/P-mediated biofilm formation and serve as a starting point for identifying the physiological MR/P fimbrial receptor.

Many bacteria use fimbriae to adhere to surfaces, and this function is often essential for pathogens to gain a foothold in the host. In this study, we examine the major virulence-associated fimbrial protein, MrpH, of the bacterial urinary tract pathogen Proteus mirabilis. This species is particularly known for causing catheter-associated urinary tract infections, in which it forms damaging urinary stones and crystalline biofilms that can block the flow of urine through indwelling catheters. MrpH resides at the tip of mannose-resistant Proteus-like (MR/P) fimbriae and is required for MR/P-dependent adherence to surfaces. Although MR/P belongs to a well-known class of adhesive fimbriae encoded by the chaperone-usher pathway, we found that MrpH has a dramatically different structure compared with other tip-located adhesins in this family. Unexpectedly, MrpH was found to bind a zinc cation, which we show is essential for MR/P-mediated biofilm formation and adherence to red blood cells. Furthermore, MR/P-mediated adherence can be modified by controlling zinc levels. These findings have the potential to aid development of better anti-biofilm urinary catheters or other methods to prevent P. mirabilis infection of the urinary tract.

Replication of the Salmonella Genomic Island 1 (SGI1) triggered by helper IncC conjugative plasmids promotes incompatibility and plasmid loss

The mobilizable resistance island Salmonella genomic island 1 (SGI1) is specifically mobilized by IncA and IncC conjugative plasmids. SGI1, its variants and IncC plasmids propagate multidrug resistance in pathogenic enterobacteria such as Salmonella enterica serovars and Proteus mirabilis. SGI1 modifies and uses the conjugation apparatus encoded by the helper IncC plasmid, thus enhancing its own propagation. Remarkably, although SGI1 needs a coresident IncC plasmid to excise from the chromosome and transfer to a new host, these elements have been reported to be incompatible. Here, the stability of SGI1 and its helper IncC plasmid, each expressing a different fluorescent reporter protein, was monitored using fluorescence-activated cell sorting (FACS). Without selective pressure, 95% of the cells segregated into two subpopulations containing either SGI1 or the helper plasmid. Furthermore, FACS analysis revealed a high level of SGI1-specific fluorescence in IncC⁺ cells, suggesting that SGI1 undergoes active replication in the presence of the helper plasmid. SGI1 replication was confirmed by quantitative PCR assays, and extraction and restriction of its plasmid form. Deletion of genes involved in SGI1 excision from the chromosome allowed a stable coexistence of SGI1 with its helper plasmid without selective pressure. In addition, deletion of S003 (rep) or of a downstream putative iteron-based origin of replication, while allowing SGI1 excision, abolished its replication, alleviated the incompatibility with the helper plasmid and enabled its cotransfer to a new host. Like SGI1 excision functions, rep expression was found to be controlled by AcaCD, the master activator of IncC plasmid transfer. Transient SGI1 replication seems to be a key feature of the life cycle of this family of genomic islands. Sequence database analysis revealed that SGI1 variants encode either a replication initiator protein with a RepA_C domain, or an alternative replication protein with N-terminal replicase and primase C terminal 1 domains.

The Salmonella genomic island 1 (SGI1) and its variants propagate multidrug resistance in several species of human and animal pathogens with the help of IncA and IncC conjugative plasmids that are absolutely required for SGI1 dissemination. These helper plasmids are known to trigger the excision of SGI1 from the chromosome. Here, we found that IncC plasmids also trigger the replication of the excised, circular form of SGI1 by enabling the expression of an SGI1-borne replication initiator gene. In return, high-copy replication of SGI1 interferes with the persistence of the IncC plasmid and prevents its cotransfer into a recipient cell, thereby allowing integration and stabilization of SGI1 into the chromosome of the new host. This finding is important to better understand the complex interactions between SGI1-like elements and their helper plasmids that lead to widespread and highly efficient propagation of multidrug resistance genes to a broad range of human and animal pathogens.

Unveiling the Multipath Biosynthesis Mechanism of 2-Phenylethanol in Proteus mirabilis

Proteus mirabilis could convert l-phenylalanine into 2-phenylethanol (2-PE) via the Ehrlich pathway, the amino acid deaminase pathway, and the aromatic amino acid decarboxylase pathway. The aromatic amino acid decarboxylase pathway was proved for the first time in P. mirabilis. In this pathway, l-aromatic amino acid transferase demonstrated a unique catalytic property, transforming 2-penylethylamine into phenylacetaldehyde. Eleven enzymes were supposed to involve in 2-phenylethanol synthesis. The mRNA expression levels of 11 genes were assessed over time by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) in vivo. As a result, the expression of 11 genes was significantly increased, suggesting that P. mirabilis could transform l-phenylalanine into 2-phenylethanol via three pathways under aerobic conditions; nine genes were significantly overexpressed, suggesting that P. mirabilis could synthesize 2-phenylethanol via the Ehrlich pathway under anaerobic conditions. This study reveals the multipath synthetic metabolism for 2-phenylethanol in P. mirabilis and will enrich the new ideas for natural (2-PE) synthesis.

A single Proteus mirabilis lineage from human and animal sources: a hidden reservoir of OXA-23 or OXA-58 carbapenemases in Enterobacterales

In Enterobacterales, the most common carbapenemases are Ambler's class A (KPC-like), class B (NDM-, VIM- or IMP-like) or class D (OXA-48-like) enzymes. This study describes the characterization of twenty-four OXA-23 or OXA-58 producing-Proteus mirabilis isolates recovered from human and veterinary samples from France and Belgium. Twenty-two P. mirabilis isolates producing either OXA-23 (n = 21) or OXA-58 (n = 1), collected between 2013 and 2018, as well as 2 reference strains isolated in 1996 and 2015 were fully sequenced. Phylogenetic analysis revealed that 22 of the 24 isolates, including the isolate from 1996, belonged to a single lineage that has disseminated in humans and animals over a long period of time. The blaOXA-23 gene was located on the chromosome and was part of a composite transposon, Tn6703, bracketed by two copies of IS15∆II. Sequencing using Pacbio long read technology of OXA-23-producing P. mirabilis VAC allowed the assembly of a 55.5-kb structure encompassing the blaOXA-23 gene in that isolate. By contrast to the blaOXA-23 genes, the blaOXA-58 gene of P. mirabilis CNR20130297 was identified on a 6-kb plasmid. The acquisition of the blaOXA-58 gene on this plasmid involved XerC-XerD recombinases. Our results suggest that a major clone of OXA-23-producing P. mirabilis is circulating in France and Belgium since 1996.

Distribution of blaTEM, blaSHV, blaCTX-M, blaOXA, and blaDHA in Proteus mirabilis Isolated from Diabetic Foot Infections in Erbil, Iraq

Diabetic foot infection is considered to be one of the most important medical, economic, and social problems and a major cause of morbidity and mortality. Proteus mirabilis is a common etiologic agent of diabetic foot infections. This study aimed to determine the prevalence of beta-lactamase genes in P. mirabilis recovered from patients with diabetic foot wounds in Erbil, Iraq. Eighteen P. mirabilis isolated from 84 patients with diabetic foot ulcers were first phenotypically examined for the existence of extended-spectrum beta-lactamases by combined disc method and double-disc synergy method that all isolates showed positive results by both methods. The results were confirmed genetically by PCR to detect beta-lactamase-encoding genes (blaTEM, blaSHV, blaCTX-M, blaOXA, and blaDHA). The results revealed that all isolates contained extended-spectrum beta-lactamase and that 80% of the P. mirabilis isolates contained blaDHA, 60% had blaTEM, 53.3% had blaOXA, and 26.7% had blaCTX-M, whereas no isolates harbored blaSHV. The coexistence of two or more beta-lactamase genes in one isolate was observed. The existence of four genes (blaTEM + blaCTX-M + blaOXA + blaDHA) in the same isolate was documented in two isolates. In conclusion, this is the first study that reports a high prevalence of blaDHA and the coexistence of four resistance genes in the same organism in P. mirabilis isolated from diabetic foot patients in Iraq.

SGI0, a relative of Salmonella genomic islands SGI1 and SGI2, lacking a class 1 integron, found in Proteus mirabilis

Several groups of integrative mobilizable elements (IMEs) that harbour a class 1 integron carrying antibiotic resistance genes have been found at the 3'-end of the chromosomal trmE gene. Here, a new IME, designated SGI0, was found in trmE in the sequenced and assembled genome of a French clinical, multiply antibiotic resistant Proteus mirabilis strain, Pm1LENAR. SGI0 shares the same gene content as the backbones of SGI1 and SGI2 (overall 97.6% and 97.7% nucleotide identity, respectively) but it lacks a class 1 integron. However, SGI0 is a mosaic made up of segments with >98.5% identity to SGI1 and SGI2 interspersed with segments sharing 74-95% identity indicating that further diverged backbone types exist and that recombination between them is occurring. The structure of SGI1-V, here re-named SGI-V, which lacks two SGI1 (S023 and S024) backbone genes and includes a group of additional genes in the backbone, was re-examined. In regions shared with SGI1, the backbones shared 97.3% overall identity with the differences distributed in patches with various levels of identity. The class 1 integron is also in a slightly different position with the target site duplication AAATT instead of ACTTG for SGI1 and variants, indicating that it was acquired independently. The Pm1LENAR resistance genes are in the chromosome, in Tn7 and an ISEcp1-mobilised segment.

Altered metabolomic profile of dual-species biofilm: Interactions between Proteus mirabilis and Candida albicans

In this study, we aimed to determine the interspecies interactions between Proteus mirabilis and Candida albicans. Mono and dual-species biofilms were grown in a microtiter plate and metabolomic analysis of the biofilms was performed. The effects of togetherness of two species on the expression levels of candidal virulence genes and urease and swarming activities of P.mirabilis were investigated. The growth of C.albicans was inhibited by P.mirabilis whereas the growth and swarming activity of P.mirabilis were increased by C.albicans. The inhibition of Candida cell growth was found to be biofilm specific. The alteration was not detected in urease activity. The expressions of EFG1, HWP1 and SAP2 genes were significantly down-regulated, however, LIP1 was upregulated by P.mirabilis. In the presence of P.mirabilis carbonhydrates, amino acids, polyamine and lipid metabolisms were altered in C.albicans. Interestingly, the putrescine level was increased up to 230 fold in dual-species biofilm compared to monospecies C.albicans biofilm. To our knowledge, this is the first study to investigate the impact of each microbial pathogen on the dual microbial environment by integration of metabolomic data.

Comparative Genomics of Antibiotic-Resistant Uropathogens Implicates Three Routes for Recurrence of Urinary Tract Infections

The rise of antimicrobial resistance in uropathogens has complicated the management of urinary tract infections (UTIs), particularly in patients who are afflicted by recurrent episodes of UTIs. Antimicrobial-resistant (AR) uropathogens persistently colonizing individuals at asymptomatic time points have been implicated in the pathophysiology of UTIs. The dynamics of uropathogen persistence following the resolution of symptomatic disease are, however, mostly unclear. To further our understanding, we determined longitudinal AR uropathogen carriage and clonal persistence of uropathogenic Escherichia coli, Proteus mirabilis, and Klebsiella pneumoniae isolates in the intestinal and urinary tracts of patients affected by recurrent and nonrecurrent UTIs. Clonal tracking of isolates in consecutively collected urine and fecal specimens indicated repeated transmission of uropathogens between the urinary tract and their intestinal reservoir. Our results further implicate three independent routes of recurrence of UTIs: (i) following an intestinal bloom of uropathogenic bacteria and subsequent bladder colonization, (ii) reinfection of the urinary tract from an external source, and (iii) bacterial persistence within the urinary tract. Taken together, our observation of clonal persistence following UTIs and uropathogen transmission between the intestinal and urinary tracts warrants further investigations into the connection between the intestinal microbiome and recurrent UTIs.IMPORTANCE The increasing antimicrobial resistance of uropathogens is challenging the continued efficacy of empiric antibiotic therapy for UTIs, which are among the most frequent bacterial infections worldwide. It has been suggested that drug-resistant uropathogens could persist in the intestine after the resolution of UTI and cause recurrences following periurethral contamination. A better understanding of the transmission dynamics between the intestinal and urinary tracts, combined with phenotypic characterization of the uropathogen populations in both habitats, could inform prudent therapies designed to overcome the rising resistance of uropathogens. Here, we integrate genomic surveillance with clinical microbiology to show that drug-resistant clones persist within and are readily transmitted between the intestinal and urinary tracts of patients affected by recurrent and nonrecurrent UTIs. Thus, our results advocate for understanding persistent intestinal uropathogen colonization as part of the pathophysiology of UTIs, particularly in patients affected by recurrent episodes of symptomatic disease.

Peer pressure from a Proteus mirabilis self-recognition system controls participation in cooperative swarm motility

Colonies of the opportunistic pathogen Proteus mirabilis can distinguish self from non-self: in swarming colonies of two different strains, one strain excludes the other from the expanding colony edge. Predominant models characterize bacterial kin discrimination as immediate antagonism towards non-kin cells, typically through delivery of toxin effector molecules from one cell into its neighbor. Upon effector delivery, receiving cells must either neutralize it by presenting a cognate anti-toxin as would a clonal sibling, or suffer cell death or irreversible growth inhibition as would a non-kin cell. Here we expand this paradigm to explain the non-lethal Ids self-recognition system, which stops access to a social behavior in P. mirabilis by selectively and transiently inducing non-self cells into a growth-arrested lifestyle incompatible with cooperative swarming. This state is characterized by reduced expression of genes associated with protein synthesis, virulence, and motility, and also causes non-self cells to tolerate previously lethal concentrations of antibiotics. We show that temporary activation of the stringent response is necessary for entry into this state, ultimately resulting in the iterative exclusion of non-self cells as a swarm colony migrates outwards. These data clarify the intricate connection between non-lethal recognition and the lifecycle of P. mirabilis swarm colonies.

A resident of animal intestines, Proteus mirabilis is a major cause of catheter-associated urinary tract infections and can cause recurrent, persistent infections. Swarming, which is a collective behavior that promotes centimeter-scale population migration, is implicated in colonization of bladders and kidneys. A regulatory factor of swarming is kin recognition, which involves the transfer of a self-identity protein from one cell into a physically adjacent neighboring cell. However, how kin recognition regulates swarming was previously unclear. We have now shown a mechanism linking kin recognition, swarm migration, and antibiotics tolerance: cells induce a transient antibiotics-tolerant, persister-like state in adjacent non-identical cells which in turn prevents non-identical cells from continuing to participate in collective swarming. These affected non-identical cells continue to exhibit large-scale gene expression suggesting an active shift into a different expression state. These data provide two key insights for the field. First, kin recognition can be a regulatory mechanism that acts with spatial and temporal precision. Second, induction into an antibiotics-tolerant state, instead of occurring stochastically, can be physically and spatially regulated by neighboring cells. These insights highlight the importance of further developing four-dimensional (time and X-, Y-, Z-axes) model systems for interrogating cell-cell signaling and control in microbial populations.

Genotypic and phenotypic profiles of virulence factors and antimicrobial resistance of Proteus mirabilis isolated from chicken carcasses: potential zoonotic risk

Proteus mirabilis is an opportunistic pathogen often associated with a variety of human infections acquired both in the community and in hospitals. In this context, the present work aimed to evaluate the genotypic and phenotypic characteristics of the virulence factors and antimicrobial resistance determinants of 32 P. mirabilis strains isolated from chicken carcasses in a poultry slaughterhouse in the north of the state of Paraná, Brazil, in order to assess a potential zoonotic risk. The isolates presented a variety of virulence genes that contribute to the development of infection in humans. The mrpA, pmfA, atfA (fimbriae), ireA (siderophores receptor), zapA, ptA (Proteases), and hpmA (hemolysin) genes were found in 32 (100%) isolates and ucaA (fimbriae) in 16 (50%). All isolates showed aggregative adherence in HEp-2 cells and formed biofilms. Of all strains, 27 (84.38%) showed cytotoxic effects in Vero cells. Antimicrobial susceptibility was tested using 20 antimicrobials, in which 25 (78.13%) strains were considered multidrug-resistant. The presence of blaESBL and blaampC genes conferring resistance to β-lactams and qnr to quinolones were also detected in the isolates after presumption in the phenotypic test, in which 7 (21.88%) isolates contained the CTX-M-2 group, 11 (34.38%) contained CIT group and 19 (59.38%) contained qnrD. Therefore, chicken carcasses contaminated with P. mirabilis may pose a health risk to the consumer, as these isolates have a variety of virulence and antimicrobial resistance characteristics that can be found in P. mirabilis strains isolated from human infections.

Alcohol dehydrogenases from Proteus mirabilis contribute to alcoholic flavor

BACKGROUND

Cheese ripening involves a complex series of metabolic reactions and numerous concomitant secondary transformations. Alcohol dehydrogenase (ADH) converts aldehydes into their corresponding alcohols, which enrich cheese aroma.

RESULTS

In this study, we identified five ADH genes in Proteus mirabilis JN458, and these genes were overexpressed and characterized in Escherichia coli BL21 (DE3). The optimum pH was 7.0 for the purified recombinant ADH-1, ADH-2, and ADH-3 and 8.0 for ADH-4 and ADH-5. The optimum temperature was 40 °C for ADH-1, ADH-3, and ADH-5 and 45 °C for ADH-2 and ADH-4. The K_m value of ADH-1, ADH-2, and ADH-3 was 34.45, 16.90, and 10.01 µmol L^-1 for phenylacetaldehyde, respectively. The K_m value of ADH-4 and ADH-5 was 14.81 and 24.62 µmol L^-1 for 2-methylbutanal, respectively.

CONCLUSION

Proteus species play important roles during cheese ripening. The results of our study are important for further research on cheese flavor and for quality control during cheese production. © 2019 Society of Chemical Industry.

Rapid screening of engineered microbial therapies in a 3D multicellular model

Synthetic biology is transforming therapeutic paradigms by engineering living cells and microbes to intelligently sense and respond to diseases including inflammation, infections, metabolic disorders, and cancer. However, the ability to rapidly engineer new therapies far outpaces the throughput of animal-based testing regimes, creating a major bottleneck for clinical translation. In vitro approaches to address this challenge have been limited in scalability and broad applicability. Here, we present a bacteria-in-spheroid coculture (BSCC) platform that simultaneously tests host species, therapeutic payloads, and synthetic gene circuits of engineered bacteria within multicellular spheroids over a timescale of weeks. Long-term monitoring of bacterial dynamics and disease progression enables quantitative comparison of critical therapeutic parameters such as efficacy and biocontainment. Specifically, we screen Salmonella typhimurium strains expressing and delivering a library of antitumor therapeutic molecules via several synthetic gene circuits. We identify candidates exhibiting significant tumor reduction and demonstrate high similarity in their efficacies, using a syngeneic mouse model. Last, we show that our platform can be expanded to dynamically profile diverse microbial species including Listeria monocytogenes, Proteus mirabilis, and Escherichia coli in various host cell types. This high-throughput framework may serve to accelerate synthetic biology for clinical applications and for understanding the host-microbe interactions in disease sites.

Community onset of CTX-M extended spectrum β-lactamases among uropathogenic E. coli and K. pneumoniae from Karachi, Pakistan

Urinary tract infections (UTIs) are major health issue in developing countries like Pakistan, become more complicated with extended spectrum β-lactamase (ESBL) expression in Escherichia coli and Klebsiella pneumoniae. The ground of this present study was to evaluate the incidence of cefotaxime (CTX-M) gene in Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis. The clinical isolates from various specimens were collected for one-year duration from January till December 2015. After initial screening (n=352) isolates were examined for phenotypic expression of ESBLs by double disc synergy test. Furthermore, eight-four isolates were analyzed by polymerase chain reaction for identification of Cefotaxime (CTX-M), Temoneira (TEM) and Sulfhdryl variable (SHV) genes. Among eighty-four clinical isolates CTX-M was dominant and found positive in 50 isolates (59.5%) followed by TEM in 35 (41.6%) and SHV in 11 (13%). In uropathogenic E. coli and K. pneumoniae, ESBLs gene was found in 50 and 6 isolates out of 57 and 7 respectively. Among uropathogens CTX-M was most prevalent 78% (39/50) in E. coli followed by K. pneumoniae. In uropathogenic E. coli, CTX-M was found dominant in females. The study concluded that ESBL related uropathogenic E. coli were CTX-M dominant, showed community onsets of UTIs that can be preventive and controlled with modified hygienic practices.

Allelic Exchange Mutagenesis in Proteus mirabilis

This chapter outlines a method for making unmarked, in-frame deletion mutations in Proteus mirabilis by allelic replacement. This method utilizes an R6K-based suicide plasmid allowing for integration of the plasmid by homologous recombination via a cloned insert. The plasmid also contains the sacB gene to select for plasmid loss (excision) in the presence of sucrose to create a mutant allele. This method has been applied to the P. mirabilis strains PM7002 and BB2000 and should be generally applicable to other P. mirabilis strains. The same methods described in this chapter can be used to introduce marked or point mutations in a given gene.

Transposon Insertion Site Sequencing in a Urinary Tract Model

Transposon sequencing (Tn-seq) is a technique that combines quantitative next-generation sequencing and a saturating transposon mutant library for an organism of interest, and ultimately allows for quantitation of the relative abundance of all of the mutants under a given condition, such as during experimental infection. The massively parallel sequencing capabilities of this technique provide a significant advance over more traditional methods of screening transposon mutant pools or individually determining the fitness contribution of genes of interest. Here, we describe a method for generating a genome-saturating transposon mutant library in Proteus mirabilis, determining the appropriate number of mutants for inoculation in an experimental infection model, preparing transposon insertion junctions for Illumina sequencing, and downstream analysis of mapped DNA sequencing reads for estimation of the contribution of each gene in the genome to fitness during infection.

Draft Genome Sequences of Proteus mirabilis K1609 and K670: A Model Strains for Territoriality Examination

Proteus mirabilis is a pathogenic Gram-negative bacterium characterized by its ability to swarm across surfaces, which frequently leads to colonization of the urinary tract and causes severe infections. P. mirabilis strains are also well known from their self-recognition phenomenon, referred to as Dienes phenomenon. In this study, we present novel aspect of self-recognition, which is a hierarchy in terms of strains territoriality. We report the draft genome sequences of P. mirabilis K1609 and K670 strains exhibiting the strongest and the weakest territoriality, respectively. Our results indicated that K1609 is closely related to strain BB2000, a model system for self-recognition, comparing with the K670. We annotated genes associated with recognition of kin and swarming initiation control and indicated polymorphisms by which observed differences in territoriality might results from. The phenotypic and genomic features of both strains reveal their application as a model organisms for studying not only the mechanisms of kin-recognition but also strains territoriality, thus providing new approach to the phenomenon. Availability of these genome sequences may facilitate understanding of the interactions between P. mirabilis strains.

Methodological considerations for the identification of choline and carnitine-degrading bacteria in the gut

The bacterial formation of trimethylamine (TMA) has been linked to cardiovascular disease. This review focuses on the methods employed to investigate the identity of the bacteria responsible for the formation of TMA from dietary choline and carnitine in the human gut. Recent studies have revealed the metabolic pathways responsible for bacterial TMA production, primarily the anaerobic glycyl radical-containing, choline-TMA lyase, CutC and the aerobic carnitine monooxygenase, CntA. Identification of these enzymes has enabled bioinformatics approaches to screen both human-associated bacterial isolate genomes and whole gut metagenomes to determine which bacteria are responsible for TMA formation in the human gut. We centre on several key methodological aspects for identifying the TMA-producing bacteria and report how these pathways can be identified in human gut microbiota through bioinformatics analysis of available bacterial genomes and gut metagenomes.

Sonochemical incorporated of cytosine in Cu-H2bpdc as an antibacterial agent against standard and clinical strains of Proteus mirabilis with rsbA gene

The cytosine embedded copper based metal-organic framework (Bio-MOF) was synthesized by facile one-step sonochemical method by simply mixing of 4-4, biphenyldicarboxylic, cytosine and copper nitrate (Bio-Cu-H₂bpdc-Cy). The prepared bio-MOF was characterized by XRD, FTIR and FE-SEM techniques. The effect of Cu-H₂bpdc-Cy on the expression of the rsbA gene was evaluated in the clinical and standard Proteus mirabilis and study of MIC of Cu-H₂bpdc-Cy by microdilution against them that have the rsbA gene. According to different concentrations of MIC, MBC concentrations was cultured on blood agar culture medium. Regarding to the concentration of MIC, gene expression changes were obtained by real-time PCR. MIC for standard and clinical strains of Proteus mirabilis was 1.6 and 1.8 mg/ml, and also MBC was obtained to be 1.8 and 2.0 mg/ml, respectively. Finally, in the real time PCR method, expression of the rsbA gene in presences of bio-Cu-H₂bpdc-Cy was reduced, but has no effect on the gene expression of the Housekeeping DNA Gyrase-B gene. Considering the effect of Cu-H₂bpdc-Cy on the rsbA gene in Proteus mirabilis bacteria, it is possible to use of Cu-H₂bpdc-Cy agent as a therapeutic supplement against this bacterium.

Mimicking a New 2-Phenylethanol Production Pathway from Proteus mirabilis JN458 in Escherichia coli

Bacteria rarely produce natural 2-phenylethanol. We verified a new pathway from Proteus mirabilis JN458 to produce 2-phenylethanol using Escherichia coli to coexpress l-amino acid deaminase, α-keto acid decarboxylase, and alcohol dehydrogenase from P. mirabilis. Based on this pathway, a glucose dehydrogenase coenzyme regeneration system was constructed. The optimal conditions of biotransformation by the recombinant strain E-pAEAKaG were at 40 °C and pH 7.0. Finally, the recombinant strain E-pAEAKaG produced 3.21 ± 0.10 g/L 2-phenylethanol in M9 medium containing 10 g/L l-phenylalanine after a 16 h transformation. Furthermore, when the concentration of l-phenylalanine was 4 g/L (24 mM), the production of 2-phenylethanol reached 2.88 ± 0.18 g/L and displayed a higher conversion rate of 97.38 mol %.

Subtle variation within conserved effector operon gene products contributes to T6SS-mediated killing and immunity

Type VI secretion systems (T6SS) function to deliver lethal payloads into target cells. Many studies have shown that protection against a single, lethal T6SS effector protein requires a cognate antidote immunity protein, both of which are often encoded together in a two-gene operon. The T6SS and an effector-immunity pair is sufficient for both killing and immunity. HereIn this paper we describe a T6SS effector operon that differs from conventional effector-immunity pairs in that eight genes are necessary for lethal effector function, yet can be countered by a single immunity protein. In this study, we investigated the role that the PefE T6SS immunity protein plays in recognition between two strains harboring nearly identical effector operons. Interestingly, despite containing seven of eight identical effector proteins, the less conserved immunity proteins only provided protection against their native effectors, suggesting that specificity and recognition could be dependent on variation within an immunity protein and one effector gene product. The variable effector gene product, PefD, is encoded upstream from pefE, and displays toxic activity that can be countered by PefE independent of T6SS-activity. Interestingly, while the entire pef operon was necessary to exert toxic activity via the T6SS in P. mirabilis, production of PefD and PefE alone was unable to exert this effector activity. Chimeric PefE proteins constructed from two P. mirabilis strains were used to localize immunity function to three amino acids. A promiscuous immunity protein was created using site-directed mutagenesis to change these residues from one variant to another. These findings support the notion that subtle differences between conserved effectors are sufficient for T6SS-mediated kin discrimination and that PefD requires additional factors to function as a T6SS-dependent effector.

Bacterial type VI secretion systems (T6SS) function as contractile nanomachines to puncture target cells and deliver lethal effectors. Little is known about the lifestyle or physiology dictating when bacteria normally express their T6SS. Previously, we have reported that discrimination of self during the multicellular swarming behavior of Proteus mirabilis requires the lethal action of the T6SS, T6SS-dependent effectors, and immunity proteins. Bacteria that share common immunity proteins are protected against T6SS killing and recognize each other as self. Here we introduce a new group of T6SS immunity effectors that require eight genes for killing and a single immunity gene that differs from the classical effector-immunity pairs. Variation within an effector operon drives specificity and recognition between strains. We propose that subtle sequence variation in the effector operons contribute to self and non-self recognition in these bacteria.

A single point mutation in a TssB/VipA homolog disrupts sheath formation in the type VI secretion system of Proteus mirabilis

The type VI secretion (T6S) system is a molecular device for the delivery of proteins from one cell into another. T6S function depends on the contractile sheath comprised of TssB/VipA and TssC/VipB proteins. We previously reported on a mutant variant of TssB that disrupts T6S-dependent export of the self-identity protein, IdsD, in the bacterium Proteus mirabilis. Here we determined the mechanism underlying that initial observation. We show that T6S-dependent export of multiple self-recognition proteins is abrogated in this mutant strain. We have mapped the mutation, which is a single amino acid change, to a region predicted to be involved in the formation of the TssB-TssC sheath. We have demonstrated that this mutation does indeed inhibit sheath formation, thereby explaining the global disruption of T6S activity. We propose that this mutation could be utilized as an important tool for studying functions and behaviors associated with T6S systems.