Citrobacter Koseri Research Articles

Distribution and Antibiotic Sensitivity Patterns of Faecal Bacteria from Underground Faecal Storage Cisterns in Ondo State, Nigeria

Two hundred and fifty-six (256) human faecal samples were collected from thirty-three (33) underground faecal storage cisterns across 5 major towns (Akure, Akungba, Ondo, Ore and Owo) in Ondo State, Nigeria. Salmonella-Shigella agar, Eosine Methylene Blue agar and MacConkey agar, which are selective for faecal bacteria, were used to isolate a total of 103 strains of Gram-negative bacteria. Biochemical characterization of the isolates revealed Escherichia coli (32.04%), Enterobacter aerogenes (14.56), Klepsiella pneumoniae (12.62%), Salmonella typhi (11.65%), Psudomonas aeruginosa (7.77%), Shigella dysenteriae (6.80%), Proteus mirabilis (5.83%), Citrobacter koseri (3.88%), Providentia alcalifaciens (2.91%) and Klepsiella oxytoca (1.94%). All the bacterial isolates were then subjected to antibiotic sensitivity test using antibiotic discs impregnated with Augmentin (30 µg), Gentamycin (10 µg), Pefloxacin (10 µg), Ofloxacin (5 µg), Streptomycin (10 μg), Sulfomethoxazole-trimethoprim (30 µg), Chloramphenicol (30 μg); Sparfloxacin (10 μg); Ciprofloxacin (5 μg) and Amoxicillin (20 μg). The resistance of the isolates to the antibiotics used varied from 27.18% to Ciprofloxacin, 33.98% to Ofloxacin, 47.57% to Sulphomethazole-Trimethroprim, 56.31% to Streptomycin, 66.99% to Chloramphenicol, 74.76% to Pefloxacin, 75.73% to Sparfloxacin, 75.73% to Gentamycin, 85.44% to Ampicillin and 95.15 to Augmentin. These results showed that underground human faecal storage cisterns contain potential multiple antibiotic resistant bacteria that may be transmitted to human via formites, animal vectors and water.

Phenotypic and Genotypic Characterisation of Clinical Isolates of Nosocomial Infections

The study focuses on identification and characterization of clinical isolates of nosocomial infections with an aim to create a Bank of model microorganisms for further study of mechanisms and prospects of clinical use of novel medicines causing a reversion susceptibility to antibiotics in drug resistant pathogens.
 Clinical samples of nosocomial infections were collected from phthisiological hospitals in Almaty. Clinical isolates were characterized by morpho-cultural, tinctorial, physiological and biochemical properties and also by susceptibility to antibiotics. Our studies showed that the isolates are characterized by an increased ability to form biofilms that significantly complicates the therapy and prevention of these outbreaks. Moreover, isolates were characterized by varying degrees of susceptibility to antimicrobial drugs. The strains of Citrobacter were resistant to azithromycin, which is considered as a reserve drug. This fact raises a concern about the circulation and the spread in hospitals of microorganisms resistant to the latest generation of antibiotics.
 Obtained genome-scale contigs were used for taxonomic affiliation of the isolates and for identification of genetic determinants of antibiotic resistance. The search for genetic determinants of drug resistance in the obtained genome sequences confirmed the resistance to some antibiotics obtained by phenotypic methods.
 Whole genome sequences were obtained for 4 clinical isolates identified as Citrobacter koseri SCAID URN1-2019, Citrobacter freundii SCAID PHRX1-2019, Escherichia coli SCAID URN1-2019 and Streptococcus pneumoniae SCAID PHRX1-2019. The genomes were deposited in the NCBI database under accession numbers CP052059, CP052058, CP052057, and CP052060.

Making a Case for Infection Control at Public Places of Convenience in Accra, Ghana.

In Ghana, environmental hygiene remains a major problem and infection control measures are hardly practised, particularly outside of the hospital. To provide evidence for infection control measures at public places of convenience in Accra (capital city of Ghana), this study was performed. The aim of the study was to evaluate microbial contamination of door handles at public places of convenience in Accra and assess the public health risk. A total of 183 swab specimens were collected aseptically from door handles of public places of convenience of shops, schools, hospitals, lorry stations, churches, and markets. The samples were cultured on bacteriological media, and the isolated organisms were identified. The most prevalent bacterial agent isolated was Bacillus spp. (55.7%), followed by Staphylococcus aureus (20.2%), coagulase-negative staphylococcus spp. (17.1%), Citrobacter freundii (6.0%), Citrobacter koseri (4.4%), and Salmonella Paratyphi A (3.8%). Although in low prevalence, a wide range of enteric bacteria were isolated from door handles, accounting for 12 of the 16 isolated organisms. In conclusion, door handles of places of convenience in Accra harbour several pathogenic microorganisms, especially enteric organisms. This study highlights the need for proper disinfection of door handles of places of convenience in Accra as well as handwashing after visiting such places.

Characterization of bacterial contaminants of boar semen: identification by MALDI-TOF mass spectrometry and antimicrobial susceptibility profiling

ABSTRACT Artificial insemination is the foundation of Brazilian intensive pig farming and the semen quality is a key point for the success of the productive chain. Several bacteria have already been reported as semen contaminants and may cause morphological and functional changes in sperm, decreasing male fertility, in addition to predisposing females to reproductive failures. The objective of this study was to perform a bacteriological examination of boar semen (Sus scrofa) obtained from an Artificial Insemination Centre in the southwestern region of Paraná. One hundred semen samples were assessed for volume, colour, smell, motility, agglutinated sperm cells and for bacterial contamination. Bacterial species were further identified by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. The results revealed positive bacterial isolation in 43% of the samples, with predominance of Gram-negative pathogens. The identified species were: Pseudomonas aeruginosa, Proteus mirabilis, Escherichia coli, Kerstersia gyiorum, Aerococcus viridans, Brevibacterium casei, Providencia stuartii, Citrobacter koseri and Staphylococcus pasteuri. The E. coli contamination was associated with decreased sperm motility (p < 0.01) and vigour (p = 0.002). Despite the frequent usage, the antimicrobial resistance tests showed that few isolates were resistant to gentamycin or neomycin, drugs that are commonly used to extend semen viability in Brazil.

Positivity of Carbapenemase-producing Enterobacteriaceae in Patients Following Exposure within Long-term Care Facilities in Seoul, Korea.

BackgroundCarbapenemase-producing Enterobacteriaceae (CPE) are emerging as a worldwide threat. Long-term care facilities (LTCFs) are considered a reservoir for CPE and play a central role in transmission to acute care hospitals. We investigated the CPE positivity in patients exposed to CPE in LTCFs. Furthermore, we analyzed the CPE positivity rates in the environment exposed to CPE.MethodsWe collected rectal swab specimens from patients residing in LTCFs who were exposed to CPE. Environmental sampling was performed by infection control practitioners from sites classified as patient private space, common space in the patient room, common space other than patient rooms, and nursing station. Each sample was cultured on a Chrom Klebsiella pneumoniae carbapenemase (KPC) agar for CPE screening. The positive isolates were subjected to a polymerase chain reaction to identify the presence of blaKPC, blaVIM, blaIMP, blaOXA-48, and blaNDM and determine CPE genotype.ResultsFrom 65 index cases, a total of 24 hospitals and 481 patients were enrolled; 414 patients who had resided in the same patient room as a patient with confirmed CPE and 67 patients who were newly admitted to that patient room. A total of 117 (24.3%) patients were positive for CPE among which 93 (22.5%, 93/414) were already admitted patients and 24 (35.8%, 24/67) were newly admitted patients. A total of 163 CPEs were detected and K. pneumoniae (n = 104, 63.8%) was the most common bacteria followed by Escherichia coli (n = 43, 26.4%) and Citrobacter koseri (n = 11, 6.7%). Environmental sampling was performed in 24 hospitals and 604 sites. A total of 12 sites (2.0%) were positive for CPE and sink in the nursing station (n = 6, 4.2%) was the most contaminated space.ConclusionCPE colonization rates in patients exposed to CPE in LTCFs were higher than those found in acute care hospitals. Proper infection control measures for detecting and reducing CPE colonization in patients residing in LTCFs are required. Newly admitted patients could also be carriers; therefore, infection control for newly admitted patients also needs to be thorough.

Prevalence and antimicrobial susceptibility patterns of bacteria in ICU patients with lower respiratory tract infection: A cross-sectional study

Objective: To investigate the prevalence of isolated organisms in patients with lower respiratory tract infections and the antibiotic susceptibilities at a tertiary care center. Methods: In this observational and cross-sectional analysis, 114 patients admitted in the intensive care unit were enrolled. The endotracheal aspirates and bronchoalveolar lavage were collected. The bacteria were isolated and identified, and finally, antimicrobial sensitive pattern of the isolated bacteria was examined. Results: The prevalence of infection was 72.72% in male patients and 27.28% in females. The predominant bacteria were Klebsiella pneumoniae (37.50%) followed by Acinetobacter spp. (36.36%), Pseudomonas aeruginosa (7.95%), Escherichia coli (6.81%), Proteus mirabilis (2.27%), atypical Escherichia coli (1.13%), Enterococcus spp. (1.13%), Elizabethkingia meningoseptica (1.13%), Staphylococcus aureus (1.13%), Proteus vulgaris (1.13%), Citrobacter freundii (1.13%), and Citrobacter koseri (1.13%). High resistance to cephalosporins (82.18%) was demonstrated in all Gram-negative bacteria. Bacteria showed susceptibility to colistin (88.75%) followed by tigecycline (83.11%), gentamycin (36.18%), and amikacin (49.23%). Conclusions: As the most frequent respiratory organisms, Klebsiella pneumoniae and Acinetobacter spp. have increased resistance to cephalosporins and susceptibility to colistin followed by tigecycline.

UPΦphages, a new group of filamentous phages found in several members of Enterobacteriales.

Filamentous phages establish chronic infections in their bacterial hosts, and new phages are secreted by infected bacteria for multiple generations, typically without causing host death. Often, these viruses integrate in their host’s genome by co-opting the host’s XerCD recombinase system. In several cases, these viruses also encode genes that increase bacterial virulence in plants and animals. Here, we describe a new filamentous phage, UPϕ901, which we originally found integrated in a clinical isolate of Escherichia coli from urine. UPϕ901 and closely related phages can be found in published genomes of over 200 other bacteria, including strains of Citrobacter koseri, Salmonella enterica, Yersinia enterocolitica, and Klebsiella pneumoniae. Its closest relatives are consistently found in urine or in the blood and feces of patients with urinary tract infections. More distant relatives can be found in isolates from other environments, including sewage, water, soil, and contaminated food. Each of these phages, which we collectively call ‘UPϕ viruses’, also harbors two or more novel genes of unknown function.

Citrobacter koseri immobilized on agarose beads for nucleoside synthesis: a potential biocatalyst for preparative applications.

The biocatalyzed synthesis of purine nucleosides and their analogs is a case widely studied due to the high pharmaceutical interest of these compounds, providing the whole-cell biocatalysts, a useful tool for this purpose. Vidarabine and fludarabine are commercial examples of expensive bioactive nucleosides that can be prepared using a microbial transglycosylation approach. Citrobacter koseri whole-cells immobilized on agarose beads proved to be an interesting option to transform this biotransformation in a preparative process. The entrapment matrix provided a useful and resistant multipurpose biocatalyst regarding its stability, mechanical strength, microbial viability and reuse. Immobilized biocatalyst retained the initial activity for up to 1year storage and after 10years, the biocatalyst did not show cell leaking and still exhibited residual activity. In addition, the biocatalyst could be reused in batch 68 times keeping up to 50% of the initial biocatalytic activity and for at least 124h in a continuous process.

Study of biofilm formation in bacterial isolates from contact lens wearers.

Purpose:To detect biofilm forming capacity of bacterial isolates obtained from the conjunctiva, contact lens and accessories of contact lens wearers using phenotypic and genotypic methods.Methods:Bacterial strains were collected from the conjunctiva, contact lens and lens storage cases of contact lens wearers. The phenotypic detection of biofilm production was done using the tube method and congo red agar method. The biofilm-forming related genes, icaA, of Coagulase negative Staphylococcus (CONS) and Staphylococcus aureus, and pslA, of P. aeruginosa, were detected using PCR.Results:A total of 265 bacterial isolates which included S. aureus, CONS, Pseudomonas, Nil-fermenter Gram-negative bacilli (NFGNB), Bacillus spp, Diphtheroids, Micrococci, Klebsiella pneumonia, Klebsiella oxytoca, E. coli, Proteus mirabilis, Proteus vulgaris, Citrobacter koseri, Citrobacter freundii, Enterobacter cloacae, Moraxella were obtained. Of the 265 isolates, 53.5% were moderately positive, 33.2% strongly positive and 13.2% negative for biofilm production by tube method and 36.6% were moderately positive, 40% strongly positive and 23.3% negative for biofilm production by congo red agar method. Of the four S. aureus isolates, two (50%) showed the presence of icaA gene. Of the 23 CONS isolates, three (13%) showed the presence of icaA gene. All the Pseudomonas isolates were negative for presence pslA (1119 bp) gene though most of them were phenotypically positive for biofilm formation.Conclusion:Most of the bacterial isolates obtained from contact lens wearers had the potential to produce biofilms. Tube method and Congo red agar method exhibited significant statistical correlation (P-value = 0.006) and picked up a good number of biofilm-forming isolates, hence may be used for detection of biofilm production. The absence of biofilm-forming gene did not rule out the possibility for phenotypic biofilm production by bacteria.

The Effect of Ten Essential Oils on Several Cutaneous Drug-Resistant Microorganisms and Their Cyto/Genotoxic and Antioxidant Properties.

In this study, we determined the antimicrobial activity of ten essential oils (EOs)—oregano, thyme, clove, arborvitae, cassia, lemongrass, melaleuca, eucalyptus, lavender, and clary sage—against drug-resistant microorganisms previously isolated from patients with skin infections. The essential oil compositions were determined using gas chromatography coupled to mass spectrometry (GC/MS). The assayed bacteria included Pseudomonas aeruginosa, Proteus vulgaris, Citrobacter koseri, and Klebsiella pneumoniae. Two drug-resistant yeasts (Candida albicans and Candida parapsilosis) were also involved in our survey. Oregano, thyme, cassia, lemongrass and arborvitae showed very strong antibacterial and antifungal activity against all tested strains. These results show that these essential oils may be effective in preventing the growth of the drug-resistant microorganisms responsible for wound infections. In this study, the genotoxic effects of tested essential oils on healthy human keratinocytes HaCaT were evaluated using the comet assay for the first time. These results revealed that none of the essential oils induced significant DNA damage in vitro after 24 h. Moreover, the treatment of HaCaT cells with essential oils increased the total antioxidant status (TAS) level. The obtained results indicate that EOs could be used as a potential source of safe and potent natural antimicrobial and antioxidant agents in the pharmaceutical and food industries.

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

Citrobacter species are opportunistic bacterial pathogens that have been implicated in both nosocomial and community-acquired infections. Among the genus Citrobacter, Citrobacter koseri is often isolated from clinical material, and has been known to cause meningitis and brain abscess in neonates and immunocompromised individuals. The virulence determinants of Citrobacter, however, remain largely unknown. Based on traditional methods, the genus Citrobacter has been divided into 11 species, but this has been problematic. Here, we determined an improved, detailed, and more accurate phylogeny of the genus Citrobacter based on whole genome sequence (WGS) data from 129 Citrobacter genomes, 31 of which were sequenced in this study. A maximum likelihood (ML) phylogeny constructed with core genome single-nucleotide polymorphisms (SNPs) classified all Citrobacter isolates into 11 distinct groups, with all C. koseri strains clustering into a single group. For comprehensive and systematic comparative genomic analyses, we investigated the distribution of virulence factors, resistance genes, and macromolecular secretion systems among the Citrobacter genus. Moreover, combined with group-specific genes analysis, we identified a key gene cluster for iron transport, which is present in the C. koseri group, but absent in other the groups, suggesting that the high-pathogenicity island (HPI) cluster may be important for the pathogenicity of C. koseri. Animal experiments showed that loss of the HPI cluster significantly decreased C. koseri virulence in mice and rat. Further, we provide evidence to explain why Citrobacter freundii is less susceptible than C. koseri to several antibiotics in silico. Overall, our data reveal novel virulence clusters specific to the predominantly pathogenic C. koseri strains, which form the basis for elucidating the virulence mechanisms underlying these important pathogens.

Genotypic study of Citrobacter koseri, an emergent platelet contaminant since 2012 in France.

Transfusion-transmitted bacterial infection is a rare occurrence but the most feared complication in transfusion practices. Between 2012 and 2017, five cases of platelet concentrates (PCs) contaminated with the bacterial pathogen Citrobacter koseri (PC-Ck) have been reported in France, with two leading to the death of the recipients. We tested the possibilities of the emergence of a PC-specific clone of C. koseri (Ck) and of specific bacterial genes associated with PC contamination. The phylogenetic network, based on a homemade Ck core genome scheme, inferred from the genomes of 20 worldwide Ck isolates unrelated to PC contamination taken as controls (U-Ck) and the genomes of the five PC-Ck, explored the clonal relationship between the genomes and evaluated the distribution of PC-Ck throughout the species. Along with this core genome multilocus sequence typing approach, a Ck pan genome has been used to seek genes specific to PC-Ck isolates. Our genomic approach suggested that the population of C. koseri is nonclonal, although it also identified a cluster containing three PC-Ck and eight U-Ck. Indeed, the PC-Ck did not share any specific genes. The elevated incidence of PCs contaminated by C. koseri in France between 2012 and 2017 was not due to the dissemination of a clone. The determinants of the recent outbreaks of PC contamination with C. koseri are still unknown.

Increased Serum Immunoglobulin Responses to Gut Commensal Gram-Negative Bacteria in Unipolar Major Depression and Bipolar Disorder Type 1, Especially When Melancholia Is Present.

Major depressive disorder (MDD) is accompanied by higher serum IgM/IgA responses to LPS of Gram-negative bacteria, suggesting increased bacterial translocation and gut dysbiosis while the latter may occur in bipolar disorder (BD). There are differences between MDD and BD type 1 (BP1) and 2 (BP2) in nitro-oxidative stress biomarkers associated with leaky gut. This study examines serum IgM/IgA responses directed to LPS of 6 Gram-negative bacteria as well as IgG responses to oxidized LDL (oxLDL) in 29 BP1, 37 BP2, 44 MDD, and 30 healthy individuals. Increased IgM/IgA responses to Pseudomonas aeruginosa significantly discriminated patients with affective disorders (MDD plus BD) from controls. BP1 patients showed higher IgM responses to Morganella morganii as compared with MDD and BP2 patients. Patients with melancholia showed higher IgA responses to Citrobacter koseri as compared to controls and non-melancholic depression. The total score on the Hamilton Depression Rating Scale was significantly associated with IgA responses to C. koseri. IgG to oxLDL was significantly associated with increased bacterial translocation. In conclusion, MDD, BP1, and BP2 are accompanied by an immune response due to the increased load of LPS while these aberrations in the gut-brain axis are most pronounced in BP1 and melancholia. Activated oxidative stress pathways and autoimmune responses to oxidative specific epitopes in mood disorders may be driven by a breakdown in gut paracellular, transcellular, and/or vascular pathways. If replicated, drugs that protect the integrity of the gut barrier may offer novel therapeutic opportunities for BP1 and MDD.

Bacterial flora distribution and antimicrobial resistance of pyogenic liver abscess: a multicenter retrospective study (A report of 897 cases)

Bacterial flora distribution and antimicrobial resistance of pyogenic liver abscess: a multicenter retrospective study (A report of 897 cases)

Crystal structures of AztD provide mechanistic insights into direct zinc transfer between proteins

Zinc acquisition from limited environments is critical for bacterial survival and pathogenesis. AztD has been identified as a periplasmic or cell surface zinc-binding protein in numerous bacterial species. In Paracoccus denitrificans, AztD can transfer zinc directly to AztC, the solute binding protein for a zinc-specific ATP-binding cassette transporter system, suggesting a role in zinc acquisition and homeostasis. Here, we present the first cry\tstal structures of AztD from P. denitrificans and tbe human pathogen Citrobacter koseri, revealing a beta-propeller fold and two high-affinity zinc-binding sites that are highly conserved among AztD homologs. These structures combined with transfer assays using WT and mutant proteins provide rare insight into the mechanism of direct zinc transfer from one protein to another. Given the importance of zinc import to bacterial pathogenesis, these insights may prove valuable to the development of zinc transfer inhibitors as antibiotics.

Myo-inositol utilization by Citrobacter koseri promotes brain infection

Citrobacter species are opportunistic bacterial pathogens that are implicated in both nosocomial and community-acquired infections. Among the Citrobacter species, Citrobacter koseri is often isolated from clinical material, and it can cause meningitis and brain abscesses in neonates and immunocompromised individuals, thus posing a great threat to human health. However, the virulence determinants of C. koseri remain largely unknown. Myo-inositol is an abundant carbohydrate in the environment and in certain organs of the human body, especially the brain. The C. koseri genome harbors a cluster of genes, QCQ70420.1 to QCQ70429.1 (named the Ino-cluster in this study), which encode IolBCDE, MmsA, and an ATP-binding cassette transporter. The gene cluster may be involved in the utilization of myo-inositol. To investigate the functions of the Ino-cluster in C. koseri, we constructed a mutant strain by deleting the Ino-cluster and found that the mutant could not use myo-inositol as the sole carbon source, confirming that this cluster is responsible for myo-inositol utilization. Moreover, we investigated the function of the Ino-cluster and myo-inositol utilization in C. koseri pathogenicity. Deletion of the Ino-cluster significantly impaired C. koseri colonization of the brain of infected Sprague–Dawley (SD) rats and BALB/c mice, and this increased the survival rate of the infected animals, indicating that the Ino-cluster and the ability to use myo-inositol are essential for C. koseri pathogenicity. Taken together, our findings suggest that using the Ino-cluster products, C. koseri can exploit the abundant myo-inositol in the brain as a carbon source for growth, thus promoting colonization and virulence.

Genome sequence of carbapenem-resistant Citrobacter koseri carrying blaOXA-181 isolated from sewage sludge.

This study reported the resistome content of sewage sludge-isolated carbapenem-resistant Citrobacter koseri (C. koseri) carrying blaOXA-181. It also provided a general phylogenomic analysis highlighting antibiotic resistance genes (ARGs), plasmids and pathogenicity of C. koseri genomes. The carbapenem-resistantC. koseri AS1 strain was isolated from sewage sludge on CHROMagar™ mSuperCARBA™ media. Whole genome sequencing of C. koseri AS1 was performed using an HiSeq X™ Ten instrument. Additional C. koseri genomes were downloaded from National Center for Biotechnology Information (NCBI). Phylogenomic analysis was established through CSI Phylogeny. ARGs, plasmids and pathogenicity were identified using ResFinder 3.1, PlasmidFinder 2.0 and PathogenFinder 1.1, respectively. The phylogenomic tree indicated a polyclonal pattern ofC. koseri genomes. Resistome analysis of C. koseri AS1 revealed β-lactam resistance genes (blaMAL-1 and blaOXA-181) as well as a fosfomycin resistance gene (fosA7). Three plasmids (ColKP3, ColRNAI and IncX30) were identified in the C. koseri AS1 genome. In addition, 25 ARGs were found in downloaded genomes. Of these, clinically significant ARGs such as blaKPC-2 and blaOXA-48 were found in two and four genomes, respectively. Assessment of the genomes using PathogenFinder revealed all genomes as putative human pathogens. It is believed that noC. koseri genome has been reported to carry blaOXA-181; therefore, C. koseri AS1 is the first of its kind. This study also highlighted the resistome contents of C. koseri genomes.

NASAL COLONIZATION BY GRAM-NEGATIVE BACTERIA IN DENTAL SURGEONS: INTERFACES BETWEEN PREVENTION AND CONTROL MEASURES

The work conditions of dental surgeons (DS), associated with low compliance to precautionary standards, often lead to the colonization and dissemination of infectious agents. To assess the epidemiological and microbiological aspects of nasal colonization by Gram-negative bacteria in DS while teaching (dentistry teachers). The data were collected by application of a questionnaire and a nasal swab. The biochemical identification, the susceptibility profile and the detection of β-lactamases were carried out in Vitek 2 compact®. 41 (77.3%) DS participated in the study, nine of them (22.0%) presented nasal colonization by Enterobacteriaceae, the participants were predominantly men (27/65.9%), over 50 years of age (24/58.5%). All ofthem confirmed using procedure gloves and a surgical mask while attending patients, with frequent (95.5%) hand washing although a statistical difference was found regarding personal habits (p=0.03). Enterobacter aerogenes (60.0%) was the most prevalent species, followed by Citrobacter koseri (20.0%). The intrinsic production of AmpC β-lactamase by E. aerogenes species, which is multiresistant to antimicrobials, was present in the nasal cavity of 14.6% of the DS. There were high levels of nasal colonization by Enterobacteriaceae in teaching DS (22.0%), 14.6% had been colonized by multiresistant microorganisms and the results wereassociated with inadequate personal habits.

Asymmetric synthesis of l-phosphinothricin using thermostable alpha-transaminase mined from Citrobacter koseri

α-Transaminase (α-TA) responsible for catalyzing the reversible transfer of amino groups between amine donors and amine acceptors, is applicable to enzymatic route for asymmetric synthesis of herbicide l-phosphinothricin (l-PPT). In the search for α-TAs with better catalysis performance, three α-TAs were discovered by genome mining approach using a known sequence encoding Escherichia coli tyrosine TA (TyrB) as probe. Through detailed comparison of their expression amount, activities and characteristics, Citrobacter koseri TA (CkTA) exhibited better activity and thermostability, which retain 65.9% of initial activity after incubation at 57 °C for 4 h. The Km and kcat/Km values of CkTA were 36.75 mM and 34.29 mM−1 min−1, respectively. In addition, recombinant CkTA cells were immobilized onto Celite 545 using tris(hydroxymethyl)phosphine as crosslinker. During five repetitive asymmetric synthesis of l-PPT from 20 g/L prostereogenic ketone using l-Glu as amine donor, all the yields of l-PPT reached up to 91.2% (＞99% ee). These characteristics made CkTA a valuable addition to the currently scarce α-TA library for stereospecific synthesis of l-PPT.

IN VITRO SCREENING OF ANTIOXIDANT AND ANTIMICROBIAL ACTIVITIES OF MEDICINAL PLANTS GROWING IN SLOVAKIA

Traditional medicine usage at the preventive medicine level is comprehensive and plant-based remedies are being prescribed for the treatment of a large scale of diseases by indigenous medical practitioners around the world. The phytochemicals being observed in the fruits and vegetables as well as herbal plants are getting investigated intensively as their important role in the avoidance of diverse human diseases is undoubtful. Antioxidant and antimicrobial activities of selected medicinal herbs were evaluated in this study. Aerial parts of plants from Hypericaceae, Lamiaceae, Fabaceae, Plantaginaceae, Rubiaceae growing wild in Slovakia (locality Zobor) were investigated to characterize their polyphenol content, flavonoid content, as well as antioxidant and antimicrobial activity. Inspection of the metabolic profile combined with HPLC data showed that the ethanol extract contained mainly eight polyphenols with apigenin, daidzein, kaempferol, rutin, quercetin, vitexin, and cynaroside as the main chemicals. Among them, neochlorogenic acid, chlorogenic acid, trans-p-caffeic acid, trans-p-coumaric acid, trans-p-sinapic acid, trans-p-ferulic acid, rosmarinic acid were identified. The antioxidant capacity of ethanol extracts was evaluated by employing DPPH radical scavenging and phosphomolybdenum assays. All samples were also tested against Gram-positive (Staphylococcus aureus, Bacillus thuringiensis, Micrococcus luteus, Staphyloccocus epidermidis) and Gram-negative (Citrobacter koseri, Escherichia coli, Pseudomonas proteolytica, Hafnia alvei, Salmonella enterica, Yersinia enterocolitica) bacterial species using the disk diffusion and minimum inhibitory concentration assays