Comparative Genomic Analysis of Citrobacter and Key Genes Essential for the Pathogenicity of Citrobacter koseri

Camel urine as a potential source of bioactive molecules showing their efficacy against pathogens: A systematic review

Camels are highly suited for severe desert conditions and able to provide most of the natural products like urine, which has been used as alternative medicine to treat diverse infections and disorders. There is, however, a shortage and paucity of scientific reviews highlighting the antifungal, antibacterial and antiviral effects of camel urine. By better understanding its antimicrobial characteristics, our overarching aim is to provide an exhaustive overview of this valuable natural product by synthesizing and summarizing data on the efficacy of this biofluid and also describing the potential substances exhibiting antimicrobial properties. We searched three databases in order to point out relevant articles (Web of Science, Scopus and Google Scholar) until December 2022. Research articles of interest evaluating the antimicrobial effects of camel urine were selected. Overall, camel urine furnished promising antibacterial activities against gram-positive bacteria, namely Staphylococcus aureus (30 mm), Bacillus cereus (22 mm), Bacillus subtilis (25 mm) and Micrococcus luteus (21 mm), as well as gram-negative bacteria, especially Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterobacter cloacae, and Salmonella spp., without forgetting its efficiency on Mycobacterium tuberculosis as well. The excretion also showed its potency against H1N1 virus, vesicular stomatitis virus and middle east respiratory syndrome coronavirus. Similarly, the camel urine featured strong antifungal activity against Candida albicans, Aspergillus niger, Aspergillus flavus and dermatophytes with a minimal inhibitory concentration of 0.625 μg/ml against Trichophyton violaceum, 2.5 μg/ml against Microsporum canis and 1.25 μg/ml against Trichophyton rubrum and Trichophyton mentagrophytes. This comprehensive review will be valuable for researchers interested in investigating the potential of camel urine in the development of novel broad-spectrum key molecules targeting a wide range of drug-resistant pathogenic microorganisms.

Revolutionizing and identifying novel drug targets in Citrobacter koseri via subtractive proteomics and development of a multi-epitope vaccine using reverse vaccinology and immuno-informatics

Citrobacter koseri is a gram-negative rod that has been linked to infections in people with significant comorbidities and immunocompromised immune systems. It is most commonly known to cause urinary tract infections. Thus, the development of an efficacious C. koseri vaccine is imperative, as the pathogen has acquired resistance to current antibiotics. Subtractive proteomics was employed during this research to identify potential antigenic proteins to design an effective vaccine against C. koseri. The pipeline identified two antigenic proteins as potential vaccine targets: DP-3-O-acyl-N-acetylglucosamine deacetylase and Arabinose 5-phosphate isomerase. B and T cell epitopes from the specific proteins were forecasted employing several immunoinformatic and bioinformatics resources. A vaccine was created using a combination of seven cytotoxic T cell lymphocytes (CTL), five helper T cell lymphocyte (HTL), and seven linear B cell lymphocyte (LBL) epitopes. An adjuvant (β-defensin) was added to the vaccine to enhance immunological responses. The created vaccine was stable for use in humans, highly antigenic, and non-allergenic. The vaccine's molecular and interactions binding affinity with the human immunological receptor TLR3 were studied using MMGBSA, molecular dynamics (MD) simulations, and molecular docking analyses. E. coli (strain-K12) plasmid vector pET-28a (+) was used to examine the ability of the vaccine to be expressed. The vaccine shows great promise in terms of developing protective immunity against diseases, based on the results of these computer experiments. However, in vitro and animal research are required to validate our findings.Communicated by Ramaswamy H. Sarma.

Genomic analysis of Ralstonia pickettii reveals the genetic features for potential pathogenicity and adaptive evolution in drinking water

Ralstonia pickettii, the most critical clinical pathogen of the genus Ralstonia, has been identified as a causative agent of numerous harmful infections. Additionally, Ralstonia pickettii demonstrates adaptability to extreme environmental conditions, such as those found in drinking water. In this study, we conducted a comprehensive genomic analysis to investigate the genomic characteristics related to potential pathogenicity and adaptive evolution in drinking water environments of Ralstonia pickettii. Through phylogenetic analysis and population genetic analysis, we divided Ralstonia pickettii into five Groups, two of which were associated with drinking water environments. The open pan-genome with a large and flexible gene repertoire indicated a high genetic plasticity. Significant differences in functional enrichment were observed between the core- and pan-genome of different groups. Diverse mobile genetic elements (MGEs), extensive genomic rearrangements, and horizontal gene transfer (HGT) events played a crucial role in generating genetic diversity. In drinking water environments, Ralstonia pickettii exhibited strong adaptability, and the acquisition of specific adaptive genes was potentially facilitated by genomic islands (GIs) and HGT. Furthermore, environmental pressures drove the adaptive evolution of Ralstonia pickettii, leading to the accumulation of unique mutations in key genes. These mutations may have a significant impact on various physiological functions, particularly carbon metabolism and energy metabolism. The presence of virulence-related elements associated with macromolecular secretion systems, virulence factors, and antimicrobial resistance indicated the potential pathogenicity of Ralstonia pickettii, making it capable of causing multiple nosocomial infections. This study provides comprehensive insights into the potential pathogenicity and adaptive evolution of Ralstonia pickettii in drinking water environments from a genomic perspective.

Citrobacter koseri inhibits the growth of Staphylococcus epidermidis by suppressing iron utilization

The human skin microbiome consists of many species of bacteria, including Staphylococcus aureus and S. epidermidis. Individuals with atopic dermatitis (AD) have an increased relative abundance of S. aureus, which exacerbates the inflammation of AD. Although S. epidermidis, a main component of healthy skin microbiota, inhibits the growth of S. aureus, the balance between S. epidermidis and S. aureus is disrupted in the skin of individuals with AD. In this study, we found that Citrobacter koseri isolated from patients with AD produces substances that inhibit the growth of S. epidermidis. Heat-treated culture supernatant (CS) of C. koseri inhibited the growth of S. epidermidis but not S. aureus. The genome of C. koseri has gene clusters related to siderophores and the heat-treated CS of C. koseri contained a high concentration of siderophores compared with the control medium. The inhibitory activity of C. koseri CS against the growth of S. epidermidis was decreased by the addition of iron, but not copper or zinc. Deferoxamine, an iron-chelating agent, also inhibited the growth of S. epidermidis, but not that of S. aureus. These findings suggest that C. koseri inhibits the growth of S. epidermidis by interfering with its iron utilization.

Nationwide molecular epidemiology of carbapenemase-producing Citrobacter spp. in France in 2019 and 2020

IMPORTANCE

The emergence of carbapenemase producers in Enterobacterales mostly involves Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae complex species. However, in France, we observed the emergence and the rapid dissemination of carbapenemase in Citrobacter spp. In this study, we demonstrated that a wide variety of carbapenemases is produced by many different species of Citrobacter spp. However, we clearly identify three high-risk clones of Citrobacter freundii, ST8, ST22, and ST91 that drive the spread of carbapenemase in France. This epidemiological study paves the way of further analysis that would aim to identify the virulence factors involved in this pellicular ability of these three clones to disseminate at the hospital.

The phylogenomic landscape of extended-spectrum β-lactamase producing Citrobacter species isolated from surface water

BACKGROUND

Citrobacter species are Gram-negative opportunistic pathogens commonly reported in nosocomial-acquired infections. This study characterised four Citrobacter species that were isolated from surface water in the North West Province, South Africa.

RESULTS

Phenotypic antimicrobial susceptibility profiles of the isolates demonstrated their ability to produce the extended-spectrum β-lactamase (ESBL). Whole genomes were sequenced to profile antibiotic resistance and virulence genes, as well as mobile genetic elements. In silico taxonomic identification was conducted by using multi-locus sequence typing and average nucleotide identity. A pangenome was used to determine the phylogenomic landscape of the Citrobacter species by using 109 publicly available genomes. The strains S21 and S23 were identified as C. braakii, while strains S24 and S25 were C. murliniae and C. portucalensis, respectively. Comparative genomics and sequenced genomes of the ESBL-producing isolates consisted of n = 91; 83% Citrobacter species in which bla-CMY-101 (n = 19; 32,2%) and bla-CMY-59 (n = 12; 38,7%) were prevalent in C. braakii, and C. portucalensis strains, respectively. Macrolide (acrAB-TolC, and mdtG) and aminoglycoside (acrD) efflux pumps genes were identified in the four sequenced Citrobacter spp. isolates. The quinolone resistance gene, qnrB13, was exclusive to the C. portucalensis S25 strain. In silico analysis detected plasmid replicon types IncHI1A, IncP, and Col(VCM04) in C. murliniae S24 and C. portucalensis S25, respectively. These potentially facilitate the T4SS secretion system in Citrobacter species. In this study, the C. braakii genomes could be distinguished from C. murliniae and C. portucalensis on the basis of gene encoding for cell surface localisation of the CPS (vexC) and identification of genes involved in capsule polymer synthesis (tviB and tviE). A cluster for the salmochelin siderophore system (iro-BCDEN) was found in C. murliniae S24. This is important when it comes to the pathogenicity pathway that confers an advantage in colonisation.

CONCLUSIONS

The emerging and genomic landscapes of these ESBL-producing Citrobacter species are of significant concern due to their dissemination potential in freshwater systems. The presence of these ESBL and multidrug-resistant (MDR) pathogens in aquatic environments is of One Health importance, since they potentially impact the clinical domain, that is, in terms of human health and the agricultural domain, that is, in terms of animal health and food production as well as the environmental domain.

Comparative Genomic Analyses of Virulence and Antimicrobial Resistance in Citrobacter werkmanii, an Emerging Opportunistic Pathogen

Citrobacter werkmanii is an emerging and opportunistic human pathogen found in developing countries and is a causative agent of wound, urinary tract, and blood infections. The present study conducted comparative genomic analyses of a C. werkmanii strain collection from diverse geographical locations and sources to identify the relevant virulence and antimicrobial resistance genes. Pangenome analyses divided the examined C. werkmanii strains into five distinct clades; the subsequent classification identified genes with functional roles in carbohydrate and general metabolism for the core genome and genes with a role in secretion, adherence, and the mobilome for the shell and cloud genomes. A maximum-likelihood phylogenetic tree with a heatmap, showing the virulence and antimicrobial genes' presence or absence, demonstrated the presence of genes with functional roles in secretion systems, adherence, enterobactin, and siderophore among the strains belonging to the different clades. C. werkmanii strains in clade V, predominantly from clinical sources, harbored genes implicated in type II and type Vb secretion systems as well as multidrug resistance to aminoglycoside, beta-lactamase, fluoroquinolone, phenicol, trimethoprim, macrolides, sulfonamide, and tetracycline. In summary, these comparative genomic analyses have demonstrated highly pathogenic and multidrug-resistant genetic profiles in C. werkmanii strains, indicating a virulence potential for this commensal and opportunistic human pathogen.

Ocular Bacterial Infections: A Ten-Year Survey and Review of Causative Organisms Based on the Oklahoma Experience

Ocular infections can be medical emergencies that result in permanent visual impairment or blindness and loss of quality of life. Bacteria are a major cause of ocular infections. Effective treatment of ocular infections requires knowledge of which bacteria are the likely cause of the infection. This survey of ocular bacterial isolates and review of ocular pathogens is based on a survey of a collection of isolates banked over a ten-year span at the Dean McGee Eye Institute in Oklahoma. These findings illustrate the diversity of bacteria isolated from the eye, ranging from common species to rare and unique species. At all sampled sites, staphylococci were the predominant bacteria isolated. Pseudomonads were the most common Gram-negative bacterial isolate, except in vitreous, where Serratia was the most common Gram-negative bacterial isolate. Here, we discuss the range of ocular infections that these species have been documented to cause and treatment options for these infections. Although a highly diverse spectrum of species has been isolated from the eye, the majority of infections are caused by Gram-positive species, and in most infections, empiric treatments are effective.

Isoniazid Mono-Resistant Tuberculosis Presenting as Empyema Thoracis With Citrobacter koseri and Morganella morganii Infections: The World's First Reported Case of Its Type

Drug resistance is very common in developing countries. Isolated cases of concomitant infection with Mycobacterium tuberculosis, Citrobacter koseri, and Morganella morganii are rare. Furthermore, there is no report available in the literature of concurrent infection of Citrobacter koseri and Morganella morganii in an isoniazid mono-resistant tuberculosis patient. In this case, we present a concomitant infection with drug-resistant strains of Mycobacterium tuberculosis, Citrobacter koseri, and Morganella morganii in a 40-year-old Indian male who presented with fever, dry cough, and chest pain. He was initiated on an isoniazid mono regimen and a broad-spectrum antibiotic, following the national guidelines.

Molecular analysis of clinical Citrobacter spp. isolates: Acquisition of the Yersinia high-pathogenicity island mediated by ICEkp in C. freundii

Background

Studies on Citrobacter spp. are limited, hindering our understanding of its species evolution and medical relevance.

Methods

A total of 164 clinical Citrobacter spp. isolates were collected from 2017 to 2020 and identified by VITEK MALDI-TOF MS or VITEK-2 Gram-Negative Identification Card. All isolates were further analyzed by whole-genome sequencing using a HiSeq sequencer. All sequences were processed using different modules of the PGCGAP integrated package: Prokka and fastANI were used for annotation and average nucleotide identification (ANI), respectively. Antibiotic resistance and virulence genes were identified by searching CARD, ResFinder, and VFDB databases, respectively. Strains were identified using Ribosomal Multi-locus Sequence Typing (rMLST) classification based on 53 ribosome protein subunits (rps). The evolutionary relationship was analyzed using kSNP3 and visualized by iTOL editor v1_1. Genetic environments were compared by BLAST and visualized by Easyfig 2.2.5. The pathogenicity of some Citrobacter freundii isolates was confirmed by Galleria mellonella larvae infection test.

Results

A total of 14 species of Citrobacter spp. were identified from 164 isolates. However, 27 and 11 isolates were incorrectly identified as C. freundii and Citrobacter braakii by MALDI-TOF MS, respectively. In addition, MS also failed to identify Citrobacter portucalensis. The virulence genes mainly encoded proteins related to flagella and iron uptake systems. Citrobacter koseri isolates (n = 28) contained two iron uptake systems, coding yersiniabactin and aerobactin, respectively. C. braakii isolates (n = 32), like Salmonella, carried Vi capsule polysaccharide synthesis genes. The yersiniabactin gene clusters identified in five C. freundii isolates are located on various ICEkp elements and have not been reported previously. Moreover, ICEkp-carrying C. freundii showed diverse pathogenic features.

Conclusion

Conventional methods have significant defects in identifying Citrobacter spp. ICEkp-like elements-mediated acquirement of the Yersinia high-pathogenicity island was identified for the first time in C. freundii.

Comparative genomic analysis of Citrobacter sp. XT1-2-2 reveals insights into the molecular mechanism of microbial immobilization of heavy metals

BACKGROUND

In our previous study, Citrobacter sp. XT1-2-2 was isolated from high cadmium-contaminated soils, and demonstrated an excellent ability to decrease the bioavailability of cadmium in the soil and inhibit cadmium uptake in rice. In addition, the strain XT1-2-2 could significantly promote rice growth and increase rice biomass. Therefore, the strain XT1-2-2 shows great potential for remediation of cadmium -contaminated soils. However, the genome sequence of this organism has not been reported so far.  RESULTS: Here the basic characteristics and genetic diversity of the strain XT1-2-2 were described, together with the draft genome and comparative genomic results. The strain XT1-2-2 is 5040459 bp long with an average G + C content of 52.09%, and contains a total of 4801 genes. Putative genomic islands were predicted in the genome of Citrobacter sp. XT1-2-2. All genes of a complete set of sulfate reduction pathway and various putative heavy metal resistance genes in the genome were identified and analyzed.

CONCLUSIONS

These analytical results provide insights into the genomic basis of microbial immobilization of heavy metals.

The double-edged sword of probiotic supplementation on gut microbiota structure in Helicobacter pylori management

As Helicobacter pylori management has become more challenging and less efficient over the last decade, the interest in innovative interventions is growing by the day. Probiotic co-supplementation to antibiotic therapies is reported in several studies, presenting a moderate reduction in drug-related side effects and a promotion in positive treatment outcomes. However, the significance of gut microbiota involvement in the competence of probiotic co-supplementation is emphasized by a few researchers, indicating the alteration in the host gastrointestinal microbiota following probiotic and drug uptake. Due to the lack of long-term follow-up studies to determine the efficiency of probiotic intervention in H. pylori eradication, and the delicate interaction of the gut microbiota with the host wellness, this review aims to discuss the gut microbiota alteration by probiotic co-supplementation in H. pylori management to predict the comprehensive effectiveness of probiotic oral administration.Abbreviations: acyl-CoA- acyl-coenzyme A; AMP- antimicrobial peptide; AMPK- AMP-activated protein kinase; AP-1- activator protein 1; BA- bile acid; BAR- bile acid receptor; BCAA- branched-chain amino acid; C2- acetate; C3- propionate; C4- butyrate; C5- valeric acid; CagA- Cytotoxin-associated gene A; cAMP- cyclic adenosine monophosphate; CD- Crohn's disease; CDI- C. difficile infection; COX-2- cyclooxygenase-2; DC- dendritic cell; EMT- epithelial-mesenchymal transition; FMO- flavin monooxygenases; FXR- farnesoid X receptor; GPBAR1- G-protein-coupled bile acid receptor 1; GPR4- G protein-coupled receptor 4; H2O2- hydrogen peroxide; HCC- hepatocellular carcinoma; HSC- hepatic stellate cell; IBD- inflammatory bowel disease; IBS- irritable bowel syndrome; IFN-γ- interferon-gamma; IgA immunoglobulin A; IL- interleukin; iNOS- induced nitric oxide synthase; JAK1- janus kinase 1; JAM-A- junctional adhesion molecule A; LAB- lactic acid bacteria; LPS- lipopolysaccharide; MALT- mucosa-associated lymphoid tissue; MAMP- microbe-associated molecular pattern; MCP-1- monocyte chemoattractant protein-1; MDR- multiple drug resistance; mTOR- mammalian target of rapamycin; MUC- mucin; NAFLD- nonalcoholic fatty liver disease; NF-κB- nuclear factor kappa B; NK- natural killer; NLRP3- NLR family pyrin domain containing 3; NOC- N-nitroso compounds; NOD- nucleotide-binding oligomerization domain; PICRUSt- phylogenetic investigation of communities by reconstruction of unobserved states; PRR- pattern recognition receptor; RA- retinoic acid; RNS- reactive nitrogen species; ROS- reactive oxygen species; rRNA- ribosomal RNA; SCFA- short-chain fatty acids; SDR- single drug resistance; SIgA- secretory immunoglobulin A; STAT3- signal transducer and activator of transcription 3; T1D- type 1 diabetes; T2D- type 2 diabetes; Th17- T helper 17; TLR- toll-like receptor; TMAO- trimethylamine N-oxide; TML- trimethyllysine; TNF-α- tumor necrosis factor-alpha; Tr1- type 1 regulatory T cell; Treg- regulatory T cell; UC- ulcerative colitis; VacA- Vacuolating toxin A.

Genotypic Detection of qnrA and qnrC Genes in Citrobacter koseri Isolated from Patients with Urinary Tract Infection

The urinary tract infection (UTI) is a prevalent infection that affects people of all ages. Bacterial agents are the most common causes of UTIs. Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, and other staphylococcal species, Citrobacter freundii and Citrobacter koseri (C. koseri) account for a smaller number of infections. These pathogens are transported into the urinary tract from the colonic biotope into dysbacteriosis. Urine samples were randomly collected from 249 outpatients who were suspected of having UTIs. After genital cleaning, 10 mL of urine specimens were collected in a sterilized bowel. Then, the specimens were centrifuged at 2,000 rpm for 5 min and the residue was aerobically incubated with the broth infusion of brain flasks at 37°C for 24 h and then applied with a sterile ring onto blood agar plates and MacConkey agar (OxoidTM). Out of 249 urine samples, the results proved that there were 176 (70.7%) and 51(20.5%) gram-negative and gram-positive bacteria isolates, respectively. However, the results demonstrated that there were 22 (8.8%) urine samples with no growth. In addition, the results showed that eight various antimicrobials are used to treat C. koseri. In the current study, C. koseri was treated with eight different antimicrobial agents. The antimicrobial resistance rate for 7 isolates against Cefotaxime, Ceftriaxone, Ciprofloxacin, and Levofloxacin was high for 6 (85.71%) isolates. The results indicated that 6 and 5 isolates had 85.71% and 71.42% antimicrobial resistance against Ceftazidime and Levofloxacin, respectively. Whereas Gentamicin showed a moderate rate of resistance (4 isolates, 57.14%), and Amikacin resistance was found in 5 isolates, accounting for 28.57%. The bacterial isolates had a high susceptibility rate to Imipenem. The qnrA gene was found in 6 (85.71%) isolates. However, the recorded data demonstrated that there is no isolate carrying the qnrC gene. Among all pathogenic bacteria, C. koseri was the lowest causative agent of UTI in this study and was highly resistant to most antimicrobials except Imipenem, which was a good antibiotic with 100% sensitivity.

Second Trimester Fetal Loss Due to Citrobacter koseri Infection: A Rare Cause of Preterm Premature Rupture of Membranes (PPROM)

Citrobacter koseri is a facultative anaerobic, motile, non-spore-forming Gram-negative bacillus, which belongs to the family of Enterobacteriaceae. Severe infections due to Citrobacter spp. have been reported in the urinary tract, respiratory airways, intra-abdominal organs, skin and soft tissue, eye, bone, bloodstream, and central nervous system. In newborns, C. koseri is a well-known cause of meningitis, cerebral abscesses, brain adhesions, encephalitis, and pneumocephalus. Infection can be acquired through vertical maternal transmission or horizontal hospital settings; however, in many cases, the source is unknown. Preterm premature rupture of membranes (PPROM), caused by C. koseri, has rarely been described. Herein, we describe a case of PPROM at 16 weeks and 3 days of gestation, leading to anhydramnios. The parents opted for legal termination of the pregnancy, as the prognosis was very poor. C. koseri was isolated postmortem from a placental subamniotic swab and parenchymal sample, as well as fetal blood and lung. To the best of our knowledge, this is the first case of early second-trimester PPROM in which C. koseri infection was demonstrated.

Complete genome sequencing and comparative analysis of Citrobacter koseri CKNJ, a strain isolated from patient with endogenous endophthalmitis

Citrobacter koseri is an opportnistic pathogen can cause a variety of diseases. Though the mortality rate of C. koseri infections is high but there is a paucity of clinical information on them. Furthermore, the genomic features of this species are poorly studied. Herein, we presented a patient with endogenous endophthalmitis secondary to septicaemia, and collected a C. koseri isolate, CKNJ, from the blood of the patient. Whole genome sequencing revealed that the CKNJ harbors no plasmid and codes for 67 putative virulence factors. Whole genome SNP-based phylogenetic analysis revealed that strain CKNJ was close to the strains with same isolation sites. Compared to the other sequenced C. koseri chromosomes, CKNJ contains several strain-variable regions, including one prophage and two large genomic islands. The sequencing of the first complete genome of a clinical strain from China should reinforce our understanding of the genomic features and pathogenicity of this invasive infection-causing C. koseri with clinical significance.

Genomic insights into evolution of pathogenicity and resistance of multidrug-resistant Raoultella ornithinolytica WM1

Raoultella ornithinolytica is a poorly understood opportunistic pathogen, and the underlying mechanisms of its multidrug resistance and pathogenicity have not yet been comprehensively investigated. The multidrug-resistant (MDR) strain WM1 was isolated from the blood of a male patient in Tianjin, China, in 2018. Here, we describe the complete genome and provide a genomic analysis of R. ornithinolytica WM1. The isolate was resistant to all tested antimicrobials except amikacin, tobramycin, and tigecycline. Two plasmids, pWM1-1 (IncHI5) and pWM1-2 (IncR), carried multidrug-resistance regions. A large antimicrobial resistance island region resided on pWM1-1 and exhibited mosaic structures resulting from the acquisition of complex integrations of variable regions, including genes conferring resistance to multiple classes of antimicrobials. Moreover, WM1 possessed virulence-related elements that encode several virulence factors, including type I fimbriae, Escherichia coli common pilus, type II and VI secretion systems, yersiniabactin, enterobactin, and surface polysaccharide, indicating pathogenic potential. Furthermore, the core genome phylogeny and pan-genome analyses revealed extensive genetic diversity. Our analysis indicates the need for stringent infection control, antimicrobial stewardship, periodic resistance monitoring, and rational medication to address potential threats posed by MDR R. ornithinolytica strains.

Comparative Genomic Analysis Reveals Genetic Mechanisms of the Variety of Pathogenicity, Antibiotic Resistance, and Environmental Adaptation of Providencia Genus

The bacterial genus Providencia is Gram-negative opportunistic pathogens, which have been isolated from a variety of environments and organisms, ranging from humans to animals. Providencia alcalifaciens, Providencia rettgeri, and Providencia stuartii are the most common clinical isolates, however, these three species differ in their pathogenicity, antibiotic resistance and environmental adaptation. Genomes of 91 isolates of the genus Providencia were investigated to clarify their genetic diversity, focusing on virulence factors, antibiotic resistance genes, and environmental adaptation genes. Our study revealed an open pan-genome for the genus Providencia containing 14,720 gene families. Species of the genus Providencia exhibited different functional constraints, with the core genes, accessory genes, and unique genes. A maximum-likelihood phylogeny reconstructed with concatenated single-copy core genes classified all Providencia isolates into 11 distant groups. Comprehensive and systematic comparative genomic analyses revealed that specific distributions of virulence genes, which were highly homologous to virulence genes of the genus Proteus, contributed to diversity in pathogenicity of Providencia alcalifaciens, Providencia rettgeri, and Providencia stuartii. Furthermore, multidrug resistance (MDR) phenotypes of isolates of Providencia rettgeri and Providencia stuartii were predominantly due to resistance genes from class 1 and 2 integrons. In addition, Providencia rettgeri and Providencia stuartii harbored more genes related to material transport and energy metabolism, which conferred a stronger ability to adapt to diverse environments. Overall, our study provided valuable insights into the genetic diversity and functional features of the genus Providencia, and revealed genetic mechanisms underlying diversity in pathogenicity, antibiotic resistance and environmental adaptation of members of this genus.

Diverse and emerging molecular mechanisms award polymyxins resistance to Enterobacteriaceae clinical isolates from a tertiary hospital of Recife, Brazil

OBJECTIVE

To describe the molecular mechanisms of polymyxins resistance in five Enterobacteriaceae clinical isolates from a tertiary hospital of Recife, Brazil.

METHODS

The species identification and the susceptibility to antimicrobials were firstly performed by automatized methods and polymyxin resistance was confirmed by broth microdilution methods. The genetic basis of resistance was characterized with WGS analyses to study their resistome, plasmidome and mobilome, by BLAST searches on reference databases.

RESULTS

Five (5%) Enterobacteriaceae isolates, comprising Escherichia coli (n = 2), Klebsiella pneumoniae (n = 2) and Citrobacter freundii (n = 1) species, exhibited polymyxin resistance. The mcr-1.1 gene was found in identical IncX4-plasmids harbored by both K. pneumoniae C119 (PolB MIC = 512 mg/L) and E. coli C153 (PolB MIC = 8 mg/L). The remaining E. coli strain C027 harbored the mcr-5.1 gene on an undefined Inc-plasmid (PolB MIC 256 mg/L). Some amino acid substitutions in PmrA (S29G, G144S), PmrB (S202P; D283G, W350*, Y258N) and PhoP (I44L) was detected among the E. coli clinical isolates, however they were also found in colistin-susceptible strains and predicted as neutral alterations. The mgrB of the ST54 KPC-2-producing K. pneumoniae C151 (PolB MIC = 32 g/mL) was interrupted at 69 nt by the IS903 element. The ST117 C. freundii C156 (PolB MIC = 256 mg/L) showed the A91T substitution on HAMP domain of the histidine kinase sensor CrrB, predicted as deleterious and deemed the remarkable determinant to polymyxins resistance in this strain.

CONCLUSIONS

Diverse mechanisms of polymyxins resistance were identified among clinical Enterobacteriaceae from a tertiary hospital of Recife, Brazil, such as plasmid-mediated MCR-1 and MCR-5; IS903-interruption of mgrB and mutation in CrrAB regulatory system. These findings highlight the involvement of the identified plasmids on mcr dissemination among Enterobacteriaceae; warn about co-selection of the polymyxin-resistant and KPC-producer K. pneumoniae ΔmgrB lineage by carbapenems usage; and demonstrate potential role of CrrAB on emerging of polymyxin resistance among Enterobacteriaceae, besides Klebsiella species.

Seaweed-coral competition in the field: effects on coral growth, photosynthesis and microbiomes require direct contact

A number of tropical reefs have transitioned from coral to macroalgal dominance, but the role of macroalgal competition in coral decline is debated. There is a need to understand the relative roles of direct coral-algal effects versus indirect, microbially mediated effects shaping these interactions, as well as the relevant scales at which interactions operate under natural field, as opposed to laboratory, conditions. We conducted a manipulative field experiment investigating how direct contact versus close proximity (approx. 1.5 cm) with macroalgae (Galaxaura rugosa, Sargassum polycystum) impacted the growth, photosynthetic efficiency, and prokaryotic microbiome of the common Indo-Pacific coral Acropora millepora. Both coral growth and photosynthetic efficiency were suppressed when in direct contact with algae or their inert mimics--but not when in close proximity to corals without direct contact. Coral microbiomes were largely unaltered in composition, variability, or diversity regardless of treatment, although a few uncommon taxa differed in abundance among treatments. Negative impacts of macroalgae were contact dependent, accounted for by physical structure alone and had minimal effects on coral microbiomes. The spatial constraints of these interactions have important implications for understanding and predicting benthic community dynamics as reefs degrade.

Antibiotic Resistance, Virulence Factors, Phenotyping, and Genotyping of Non-Escherichia coli Enterobacterales from the Gut Microbiota of Healthy Subjects

Non-Escherichia coli Enterobacterales (NECE) can colonize the human gut and may present virulence determinants and phenotypes that represent severe heath concerns. Most information is available for virulent NECE strains, isolated from patients with an ongoing infection, while the commensal NECE population of healthy subjects is understudied. In this study, 32 NECE strains were isolated from the feces of 20 healthy adults. 16S rRNA gene sequencing and mass spectrometry attributed the isolates to Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, Enterobacter aerogenes, Enterobacter kobei, Citrobacter freundii, Citrobacter amalonaticus, Cronobacter sp., and Hafnia alvei, Morganella morganii, and Serratia liquefaciens. Multiplex PCR revealed that K. pneumoniae harbored virulence genes for adhesins (mrkD, ycfM, and kpn) and enterobactin (entB) and, in one case, also for yersiniabactin (ybtS, irp1, irp2, and fyuA). Virulence genes were less numerous in the other NECE species. Biofilm formation was spread across all the species, while curli and cellulose were mainly produced by Citrobacter and Enterobacter. Among the most common antibiotics, amoxicillin-clavulanic acid was the sole against which resistance was observed, only Klebsiella strains being susceptible. The NECE inhabiting the intestine of healthy subjects have traits that may pose a health threat, taking into account the possibility of horizontal gene transfer.