Serratia Marcescens Strain Research Articles

Isolation and identification of two Serratia marcescens strains from silkworm, Bombyx mori.

Bacterial septicemia commonly occurs and usually cause huge losses in sericulture industry. Here, two pathogenic bacterial strains were isolated from dead silkworm and named as ZJ-1 and ZJ-2. Phenotypic and genotypic analysis results revealed that both of these two strains are closely related to Serratia marcescens (S. marcescens). The morphological as well as physiological and biochemical characteristics of ZJ-1 were accordant with S. marcescens mentioned in Bergey's manual of determinative bacteriology, whereas ZJ-2 showed some discrepancies such as the utilization of malonate and starch, fermentation of maltose and sucrose, and tests of urease, etc. Surprisingly, ZJ-2 could produce red pigment at high temperature (37°) but ZJ-1 could not. Besides, by analyzing the lethal concentration 50 (LC50) of ZJ-1 and ZJ-2, it was found that the virulence of ZJ-2 was lower than that of ZJ-1. These results revealed that ZJ-1 and ZJ-2 were two different strains of S. marcescens and that ZJ-2 was expected to be a safe (low-toxicity) and efficient strain for the production of red pigment. Nonetheless, further research in molecular level is needed to understand the regulation mechanism of pigment production and infection of ZJ-2.

Influence of tannase from Serratia marcescens strain IMBL5 on enhancing antioxidant properties of green tea

Abstract The present study was focused on the isolation and screening of potential tannase producing gut microbes from dung beetle Onthophagus babirussa IMBL, further optimized and characterized for industrial applications. Serratia marcescens strain IMBL5 was found to be the most potent tannase producer out of 36 isolates. The adjusted process parameters for maximum tannase yield were pH 4.5 at 45 °C and 96 h incubation. The tannase production was increased 4.46 fold i.e. 120.13 U/mL, by varying the concentration of media components using Response surface methodology. The molecular weight of purified tannase was resolved at ~40 kDa through SDS-PAGE analysis. Several functional groups including carboxyl, hydroxyl and amide groups were detected in FT-IR analysis whilst the occurrence of epicatechin gallate peaks detected from HPLC chromatogram signifying the tannin degradation. Tannase also potentially induce the antioxidant properties of green tea extract which was determined through in-vitro analysis. There was no hemolytic activity exhibited in hemolysis assay using human red blood cells which corroborated that tannase derived from S. marcescens strain IMBL5 might be a safe and promising agent in food industry.

Ready‐to‐eat vegetable salads served in Nigerian restaurants: a potential source of multidrug‐resistant bacteria

Public health promotion of fruit and vegetables as healthier sources of nutrition in Nigeria has led to an increase in consumption of fruit and vegetables, particularly in the form of ready-to-eat (RTE) salads. However, the continual association of drug-resistant bacteria with fruit and vegetables creates an additional challenge for consumer safety. Hence this study was carried out to determine the prevalence of multidrug-resistant bacteria (MRB) in, and characterization of MRB isolated from, RTE salads. RTE vegetable salad samples were randomly selected for bacterial analysis with Wei's Urn iterative randomization technique and a One Way Analysis of Variance performed with Kruskal-Wallis test. Total viable bacteria count (TVC) was performed with pour-plate technique. Bacterial colonies from Petri plates were tested for multidrug resistance with Kirby Bauer disc diffusion test and prevalence/counts of MRB, as well as multiple antibiotic resistance indices (MAR), was/were subsequently deduced. Mean prevalence of MRB in all RTE salad samples was estimated at 54·38% while mean counts of MRB were estimated at 6·83±6·42 log10 CFU per g. Prevalence of bacterial resistance to all antibiotics tested ranged from 5·92 to 100·00%. Mean MAR obtained for all RTE salad samples was estimated at 0·51 (recommended limit=0·20) indicating that RTE salads were a potential source of MRB, with significant health risk. MRB isolated from RTE salads included Proteus vulgaris strain ATU 243, Bacillus thuringiensis strain AND 236, Citrobacter freundii strain ABC 2 and Serratia marcescens strain ADJ 212. This study showed that MRB constitute a significant proportion of the bacterial community present in RTE salads served in Nigerian restaurants. Our study provided empirical evidence which showed that RTE salads served in Nigerian restaurants were a potential source of MRB, with significant health risk.

Butanediol production from glycerol and glucose by Serratia marcescens isolated from tropical peat soil

Six bacterial strains , Bacillus subtilis LQOB-SE1, Bacillus coagulans LQOB-SE2, Bacillus pumilus LQOB-SE3, Brevibacillus brevis LQOB-SE4, Lysinibacillus sp. LQOB-SE5 and Serratia marcescens LQOB-SE6, isolated from a tropical peat soil , were assessed for 2,3-butanediol (2,3-BD) production by fermentation of glucose and glycerol. Only S. marcescens LQOB-SE6 strain was capable of producing 2,3-BD from both glucose and glycerol fermentation, and this process was optimized by changes in fermentation parameters. The best conditions for glycerol fermentation were initial pH 7.0, 8 g L −1 nutrient broth, 50 g L −1 substrate, and an incubation time of seven days, with 2,3-BD yield of 0.30 g g −1 , and productivity of 0.13 g L −1 h −1 . The best conditions for glucose fermentation were initial pH 7.0, 8 g L −1 nutrient broth, 75 g L −1 substrate, and an incubation time of five days, with 2,3-BD yield of 0.42 g g −1 and productivity of 0.15 g L −1 h −1 . meso -2,3-butanediol was the only stereoisomer obtained from glucose fermentation, while glycerol fermentation also produced smaller amounts of (2 R ,3 R )-2,3-butanediol. • Serratia marcescens strain from peat soil is capable of producing 2,3-butanediol. • The 2,3-butanediol production is influenced by fermentation parameters. • Glucose fermentation yielded only the meso -2,3-butanediol stereoisomer. • Glycerol fermentation yielded both meso -2,3-butanediol and (2 R ,3 R )-2,3-butanediol. • The ratio of stereoisomers varies accordingly the fermentation time.

Genetic Analysis and Immunoelectron Microscopy of Wild and Mutant Strains of the Rubber Tree Endophytic Bacterium Serratia marcescens Strain ITBB B5-1 Reveal Key Roles of a Macrovesicle in Storage and Secretion of Prodigiosin.

Rubber tree is an economically important tropical crop. Its endophytic bacterial strain Serratia marcescens ITBB B5-1 contains an intracellular macrovesicle and red pigment. In this research, the red pigment was identified as prodigiosin by quadrupole time-of-flight mass spectrometry. Prodigiosin has a wide range of potential medical values such as anticancer and antiorgan transplant rejection. The strain ITBB B5-1 accumulated prodigiosin up to 2000 mg/L, which is higher production compared to most known Serratia strains. The formation of the macrovesicle and prodigiosin biosynthesis were highly associated and were both temporal- and temperature-dependent. A mutant strain B5-1mu that failed to produce prodigiosin was obtained by ultraviolet mutagenesis. Whole genome sequencing of wild-type and mutant strains indicated that the PigC gene encoding the last-step enzyme in the prodigiosin biosynthesis pathway was mutated in B5-1mu by a 17-bp deletion. Transmission electron microscopy analysis showed that the macrovesicle was absent in the mutant strain, indicating that formation of the macrovesicle relied on prodigiosin biosynthesis. Immunoelectron microscopy using prodigiosin-specific antiserum showed the presence of prodigiosin in the macrovesicle, the cell wall, and the extracellular vesicles, while immuno-reaction was not observed in the mutant cell. These results indicate that the macrovesicle serves as a storage organelle of prodigiosin, and secretes prodigiosin into cell envelop and culture medium as extracellular vesicles.

Draft genome sequence of a multidrug-resistant KPC-2 and SRT-2 co-producing Serratia marcescens strain isolated from a hospitalised patient in Chile

ObjectivesSerratia marcescens is a neglected opportunistic pathogen of public-health concern, especially due to its antimicrobial resistance features. Here we report the draft genome sequence of the first KPC-2 and SRT-2 co-producing S. marcescens strain (UCO-366) recovered from a catheter tip culture of a hospitalised patient in Santiago, Chile, in 2014. MethodsWhole genomic DNA of strain UCO-366 was extracted and was sequenced using an Illumina NextSeq platform. De novo genome assembly was performed using Unicycler v.0.4.0 and the genome was annotated by the NCBI Prokaryotic Genome Annotation Pipeline (PGAP) v.4.8. Genomic features were analysed using bioinformatic tools available at the Center for Genomic Epidemiology, the Comprehensive Antibiotic Resistance Database (CARD) and Pathosystems Resource Integration Center (PATRIC). ResultsThe genome size of strain UCO-366 was 5 267 357bp, with a G+C content of 59.7% and comprising 5299 coding sequences (CDS), 42 tRNAs and 115 pseudogenes. The genome of UCO-366 also included an IncL/M plasmid. The resistome comprised various antimicrobial resistance genes (ARGs) conferring resistance to carbapenems, cephalosporins, aminoglycosides, sulfonamides, chloramphenicol, rifampicin and fluoroquinolones. Importantly, S. marcescens UCO-366 harboured blaKPC-2 and blaSRT-2, representing the first description of these β-lactamase genes in this species in Chile. ConclusionHere we report the genome of the first KPC-positive multidrug-resistant S. marcescens strain identified in Chile, which co-harboured several ARGs. The genome sequence of S. marcescens UCO-366 provides an insight into the antimicrobial resistance characteristics of this species in this country and offers important data for further genomic studies on this critical priority pathogen.

Spaceflight and simulated microgravity conditions increase virulence of Serratia marcescens in the Drosophila melanogaster infection model

While it has been shown that astronauts suffer immune disorders after spaceflight, the underlying causes are still poorly understood and there are many variables to consider when investigating the immune system in a complex environment. Additionally, there is growing evidence that suggests that not only is the immune system being altered, but the pathogens that infect the host are significantly influenced by spaceflight and ground-based spaceflight conditions. In this study, we demonstrate that Serratia marcescens (strain Db11) was significantly more lethal to Drosophila melanogaster after growth on the International Space Station than ground-based controls, but the increased virulence phenotype of S. marcescens did not persist after the bacterial cultures were passaged on the ground. Increased virulence was also observed in bacteria that were grown in simulated microgravity conditions on the ground using the rotating wall vessel. Increased virulence of the space-flown bacteria was similar in magnitude between wild-type flies and those that were mutants for the well-characterized immune pathways Imd and Toll, suggesting that changes to the host immune system after infection are likely not a major factor contributing towards increased susceptibility of ground-reared flies infected with space-flown bacteria. Characterization of the bacteria shows that at later timepoints spaceflight bacteria grew at a greater rate than ground controls in vitro, and in the host. These results suggest complex physiological changes occurring in pathogenic bacteria in space environments, and there may be novel mechanisms mediating these physiological effects that need to be characterized.

Microbial diversity changes and enrichment of potential petroleum hydrocarbon degraders in crude oil-, diesel-, and gasoline-contaminated soil.

This study investigated the impacts of crude oil, diesel, and gasoline on the diversity of indigenous microbial communities as well as culturable microorganisms in the studied soil. Oil contamination led to shifts in thediversityofthesoil'smicrobialcommunities, regardless of the contaminant applied. Unpolluted soils were more diverse and evenly distributed than contaminated samples. The domain Bacteria accounted for 65.15% of the whole microbial community. The bacterial phylum Proteobacteria dominated in all samples, followed by Actinobacteria and Acidobacteria. Pseudomonas with 28.15% of reads dominated in Proteobacteria, while Rhodococcus (3.07%) dominated in Actinobacteria, and Blastocatella (2.53%) dominated in Acidobacteria. The dominant fungal phyla across all samples were Ascomycota dominated by Penicillium (50.48% of sequences), and Zygomycota dominated by Mortierella (16.87%). Sequences similar to the archaeal phyla, Euryarchaeota and Thaumarchaeota, were also detected. The number of culturable microorganisms increased following the contamination and was higher in contaminated samples than in clean samples. Oil contamination also resulted in the enrichment of oil-degrading strains. Two bacteria, Serratia marcescens strain PL and Raoultella ornithinolytica PS, which were isolated from crude oil-contaminated soil, exhibited strong crude oil degradation ability. Strain PL was the most efficient strain and degraded 75.10% of crude oil, while strain PL degraded 65.48%, after 20days of incubation. However, the mixed culture of the two strains was more effective than single strain and could achieve up to 96.83% of crude oil degradation, with a complete abatement of straight-chain hydrocarbons (from C12 to C25), and more than 91% removal of highly branched hydrocarbons, phytane and pristane, which are known to be more recalcitrant to biodegradation. Strains PS and PL are two newly isolated crude oil degraders that are not among the most prominent crude oil-degrading strains referenced in the literature. Therefore, their high degradation capacity makes them perfect candidates for the bioremediation of petroleum hydrocarbon contaminated environments.

Draft Genome Sequence of a Serratia marcescens Strain Isolated from the Pitcher Fluids of a Sarracenia Pitcher Plant.

The genome of a Serratia marcescens strain (C7) that was found in the pitcher fluids of a Sarracenia rosea pitcher plant was sequenced using the Illumina platform. A 5,543,750-bp genome assembly was obtained. A total of 6,278 coding sequences are predicted from this assembly.

Production and one-step purification of serratiopeptidase enzyme from Serratia marcescens with potent anti-inflammatory and antioxidant power

Background and objective Inflammation is a huge problem facing the world. NSAIDs are the most popular and widespread drugs used for lowering the impaired symptoms accompanied with inflammation. This group has plentiful disorders to the gastrointestinal tract reaching to gastric ulcer. The objective of this study was to produce a natural product having an anti-inflammatory power without the side effects concomitant with the used drugs. The serratiopeptidase enzyme has a potent anti-inflammatory action without any abnormal disorders. Materials and methods Different media and cultural conditions were evaluated for the optimal production of the serratiopeptidase enzyme from a local bacterial strain. Partial purification was employed using the ammonium sulfate precipitation technique. Results and conclusion Serratiopeptidase enzyme was produced by the bacterial strain Serratia marcescens and its anti-inflammatory and antioxidant power were declared. The best medium was chosen for the optimal productivity and the optimum pH was 6 that recorded the highest anti-inflammatory and anti-oxidant activity at 67.5 and 71.8%, respectively, which is powerful than any chemical drugs used. Serratiopeptidase enzyme produced by this strain was partially purified by ammonium sulfate precipitation revealed an increase in specific activity by two times than the crude one with 14.7 recovery. The authors conclude the use of serratiopeptidase enzyme for treating the inflammation instead of the traditional ways.

Biodegradation of Sodium Dodecyl Sulphate (SDS) by Serratia marcescens strain DRY6

A bacterium capable of degrading sodium dodecyl sulphate (SDS) is characterized. Previously, the bacterium has been shown to have the capability to reduce molybdenum to molybdenum blue. In this report, we showed that almost complete degradation of SDS was observed in 6 to 10 days when the bacterium was grown on medium supplemented with SDS ranging from 0.5 to 1 g L-1 while higher concentrations showed partial degradation with no degradation was observed at concentrations higher than 2.5 g L-1. Other detergents were also tested including Tergitol NP9, Tergitol 15S9, Witconol 2301 (methyl oleate), sodium dodecylbenzene sulfonate (SDBS), benzethonium chloride and benzalkonium chloride. However, growth can only be seen on the anionic SDBS. We also showed that the presence of metal ions such as silver, copper, cadmium, chromium, lead and mercury inhibits the ability of the bacterium to degrade SDS by 50%. Growth on SDS could not support molybdenum-reduction in this bacterium. Growth kinetic studies showed that the growth rate could be modelled using Haldane substrate inhibition kinetics with the maximum growth rate, µmax, was 0.13 h-1, while the saturation constant or half velocity constant Ks and inhibition constant Ki, were 0.707 and 11.303 g L-1 SDS, respectively.

Bio-priming of rice seeds with novel bacterial strains, for management of seedborne Magnaporthe oryzae L.

Rice blast disease caused by Magnaporthe oryzae is a seed borne which occurs in all rice growing regions of the country (India) causing yield losses up to 40%. In the present study, we report the efficacy of different bacterial strains through seed priming in reducing the blast disease severity under in vitro, in vivo and field conditions. In vitro evaluation revealed that the Bacillus amyloliquefaciens strain UASBR9 and Serratia marcescens strain UASBR4 were found most effective in reducing disease severity (84.28%) compared to reference cultures Bacillus subtilis RBs-1 (72.00%) and Pseudomonas fluorescens RPf-1 (55.24%). The least disease severity and highest seed germination was recorded in seeds bio-primed with B. amyloliquefaciens UASBR9 (0.96 and 98.00%) under in vivo. Bio-priming also activated the induced systemic resistance as evident in the increased activities of peroxidase (0.563/min/g) and polyphenol oxidase (0.825/min/g) defense-related enzymes in comparison with untreated control in rice seedlings upon challenge inoculation with M. oryzae. Field studies showed that seeds bio-primed with B. amyloliquefaciens UASBR9 recorded lowest disease severity (7.0%) of rice blast and increased the grain yield (0.67 kg/m2). Our results indicated that B. amyloliquefaciens UASBR9 could be served as plant growth promoter and an environmental friendly alternative for chemical pesticides to manage rice blast disease.

MALDI-MS Profiling to Address Honey Bee Health Status under Bacterial Challenge through Computational Modeling.

Honey bees play a critical role in the maintenance of plant biodiversity and sustainability of food webs. In the past few decades, bees have been subjected to biotic and abiotic threats causing various colony disorders. Therefore, monitoring solutions to help beekeepers to improve bee health are necessary. Matrix-assisted laser desorption ionization-mass spectrometry (MALDI-MS) profiling has emerged within this decade as a powerful tool to identify in routine micro-organisms and is currently used in real-time clinical diagnosis. MALDI BeeTyping is developed to monitor significant hemolymph molecular changes in honey bees upon infection with a series of entomopathogenic Gram-positive and -negative bacteria. A Serratia marcescens strain isolated from one naturally infected honey bee collected from the field is also considered. A series of hemolymph molecular mass fingerprints is individually recorded and to the authors' knowledge, the first computational model harboring a predictive score of 97.92% and made of nine molecular signatures that discriminate and classify the honey bees' systemic response to the bacteria is built. Hence, the model is challenged by classifying a training set of hemolymphs and an overall recognition of 91.93% is obtained. Through this work, a novel, time and cost saving high-throughput strategy that addresses honey bee health on an individual scale is introduced.

Bacteria involved in biodegradation of creosote PAH – A case study of long-term contaminated industrial area

Polycyclic aromatic hydrocarbons (PAH) contained in creosote oil are particularly difficult to remove from the soil environment. Their hydrophobic character and low bioavailability to soil microorganisms affects their rate of biodegradation. This study was performed on samples of soil that were (for over forty years) subjected to contamination with creosote oil, and their metagenome and physicochemical properties were characterized. Moreover, the study was undertaken to evaluate the biodegradation of PAHs by autochthonous consortia as well as by selected bacteria strains isolated from long-term contaminated industrial soil. From among the isolated microorganisms, the most effective in biodegrading the contaminants were the strains Pseudomonas mendocina and Brevundimonas olei. They were able to degrade more than 60% of the total content of PAHs during a 28-day test. The biodegradation of these compounds using AT7 dispersant was enhanced only by Serratia marcescens strain. Moreover, the addition of AT7 improved the effectiveness of fluorene and acenaphthene biodegradation by Serratia marcescens 6-fold. Our results indicated that long-term contact with aromatic compounds induced the bacterial strains to use the PAHs as a source of carbon and energy. We observed that supplementation with surfactants does not increase the efficiency of hydrocarbon biodegradation.

Serratia marcescens shapes cutaneous bacterial communities and influences survival of an amphibian host.

Ongoing investigations into the interactions between microbial communities and their associated hosts are changing how emerging diseases are perceived and ameliorated. Of the numerous host-microbiome-disease systems of study, the emergence of chytridiomycosis (caused by Batrachochytrium dendrobatidis, hereafter Bd) has been implicated in ongoing declines and extinction events of amphibians worldwide. Interestingly, there has been differential survival among amphibians in resisting Bd infection and subsequent disease. One factor thought to contribute to this resistance is the host-associated cutaneous microbiota. This has raised the possibility of using genetically modified probiotics to restructure the host-associated microbiota for desired anti-fungal outcomes. Here, we use a previously described strain of Serratia marcescens (Sm) for the manipulation of amphibian cutaneous microbiota. Sm was genetically altered to have a dysfunctional pathway for the production of the extracellular metabolite prodigiosin. This genetically altered strain (Δpig) and the functional prodigiosin producing strain (wild-type, WT) were compared for their microbial community and anti-Bd effects both in vitro and in vivo. In vitro, Bd growth was significantly repressed in the presence of prodigiosin. In vivo, the inoculation of both Sm strains was shown to significantly influence amphibian microbiota diversity with the Δpig-Sm treatment showing increasing alpha diversity, and the WT-Sm having no temporal effect on diversity. Differences were also seen in host mortality with Δpig-Sm treatments exhibiting significantly decreased survival probability when compared with WT-Sm in the presence of Bd. These results are an important proof-of-concept for linking the use of genetically modified probiotic bacteria to host microbial community structure and disease outcomes, which in the future may provide a way to ameliorate disease and address critical frontiers in disease and microbial ecology.

How Serratia marcescens HB-4 absorbs cadmium and its implication on phytoremediation

A novel strain Serratia marcescens HB-4 with high Cadmium adsorption capacity was isolated from heavy metal contaminated soil in Hunan province, China. S. marcescens HB-4 reduced the concentration of Cd present in wastewater to less than 0.1 mg/L when the inlet stream contained no higher than 5.0 mg/L Cd. After treatment, wastewater meets Integrated Wastewater Discharge Standard of China (GB8978-1996). The naturally dead S. marcescens HB-4 still maintained over 80% of its Cd adsorption capacity. Scanning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS) results suggested that the mechanism of Cd adsorption can be explained as the synergy of extracellular adsorption, periplasm accumulation and intracellular absorption. The size of the accumulated Cd particular is at the nanometer scale, which can be washed out by EDTA without damaging cell integrity. SDS-polyacrylamide gel electrophoresis experiment showed that the heavy metal binding protein (especially Fe binding protein), transporter, amino acid and histidine periplasmic binding proteins and oxidoreductases were responsible for Cd removal. The pot experiment of S. marcescens HB-4 combined with Houttuynia cordata to detoxify Cd contaminated soil showed that the cadmium content in the aboveground and underground parts of Houttuynia cordata increased by 34.48% and 59.13% (w/w), respectively. The cadmium accumulation in Houttuynia cordata increased by 44.27% compared with the blank group which was not combined with S. marcescens HB-4. This work demonstrates that microbial synergistic phytoremediation has a significant potential to treat heavy metal contaminated soil.

Different Effects Of Amniotic Membrane Homogenate On The Growth Of Uropathogenic Escherichia coli, Staphylococcus aureus And Serratia marcescens.

PurposeDue to the emergence and spread of bacterial strains resistant to antibiotics, the development of new antimicrobials is imperative. The antimicrobial effect of the amniotic membrane (AM) has been explored to a limited extent so far.Materials and methodsWe collected 12 biological samples of AM homogenates and tested their antimicrobial effect on 4 pathogens, including the clinical strain of uropathogenic Escherichia coli (UPEC), the wild-type strain of Staphylococcus aureus, and the wild-type strain and a clinical strain of Serratia marcescens. To quantify the antibacterial effect of AM, we monitored the effect of AM homogenate on bacterial growth using plate count method and agar diffusion method. Additionally, minimal inhibitory concentrations (MICs) for AM homogenate dilutions were determined and S. marcescens growth in AM homogenate alone was evaluated.ResultsOur results demonstrated that AM homogenate had a bacteriostatic effect on studied UPEC and S. aureus. Interestingly, when used in lower concentrations, the AM homogenate had a bactericidal effect on both strains. In contrast, S. marcescens was completely resistant to the growth-inhibitory substances of AM homogenate. Its growth was slightly accelerated in liquid culture medium in the presence of AM homogenate and the strain was able to grow in undiluted, 2-fold and 4-fold diluted AM homogenate.ConclusionObtained results illustrated that AM homogenate could be a candidate for treatments and prevention of UPEC and S. aureus infections, but not that of S. marcescens, whose growth is enhanced by AM homogenate. Moreover, the established liquid culture medium assay can be used as a time- and cost-effective method for a personalized evaluation of drug effect on the growth of chosen bacterial strains with parallel testing of resistance or susceptibility to multiple drugs. The susceptibility of bacteria to AM homogenate in solid and liquid culture media is encouraging for its use in biomedical applications.

Antibiotic resistance and genotyping of gram-negative bacteria causing hospital-acquired infection in patients referred to Children's Medical Center.

Background and aimHospital-acquired infection (HAI) is a major problem worldwide. Understanding patterns of bacterial etiology and antibiotic susceptibility is vital to combating HAI. Besides, typing of isolates is important to establish the intra-hospital surveillance of resistant clones. In this study, we aimed to evaluate antibiotic resistance and genotyping of a number of gram-negative bacteria (GNB) causing HAI in patients who were referred to Children’s Medical Center.MethodsDuring the 6-month period, antimicrobial susceptibility profiles of GNB isolates recovered from patients in Children’s Medical Center were determined. Typing of common GNB was performed by random amplified polymorphic DNA (RAPD) analysis and the results were analyzed by Gelcompar II software.ResultsIn total, 142 (1.1%) gram-negative bacterial strains were isolated, among which 59.2% were from males. The most organisms were isolated from blood (63%) followed by wounds (13.7%). The greatest proportion of strains came from intensive care units (51%). Low sensitivity of Acinetobacter baumannii to common antibiotics and high resistance of Enterobacter spp. To cefotaxime (100%) were reported. The most efficient antibiotics for Escherichia coli strains were amikacin (84%) and gentamycin (81%). However, just 12.5% of Serratia marcescens strains were resistant to trimethoprim-sulfamethoxazole. The analysis of RAPD-typing revealed the presence of one clone in A. baumannii and E. coli and two clones in Klebsiella pneumoniae, whereas the trend varied completely in Pseudomonas aeruginosa strains and Enterobacter spp.ConclusionThe results of this study showed a possibility of an outbreak in the Children’s Medical Center. Since there is a possibility of transmission of an infection from one patient to another, high attention should be paid to the basic methods of preventing infection.

Broad-spectrum antimicrobial activity of secondary metabolites produced by Serratia marcescens strains

The genus Serratia is a predominantly unexplored source of antimicrobial secondary metabolites. The aim of the current study was thus to isolate and evaluate the antimicrobial properties of biosurfactants produced by Serratia species. Forty-nine (n = 34 pigmented; n = 15 non-pigmented) biosurfactant producing Serratia strains were isolated from environmental sources and selected isolates (n = 11 pigmented; n = 11 non-pigmented) were identified as Serratia marcescens using molecular typing. The swrW gene (serrawettin W1 synthetase) was detected in all the screened pigmented strains and one non-pigmented strain and primers were designed for the detection of the swrA gene (non-ribosomal serrawettin W2 synthetase), which was detected in nine non-pigmented strains. Crude extracts obtained from S. marcescens P1, NP1 and NP2 were chemically characterised using ultra-performance liquid chromatography coupled to electrospray ionisation mass spectrometry (UPLC-ESI-MS), which revealed that P1 produced serrawettin W1 homologues and prodigiosin, while NP1 produced serrawettin W1 homologues and glucosamine derivative A. In contrast, serrawettin W2 analogues were predominantly identified in the crude extract obtained from S. marcescens NP2. Both P1 and NP1 crude extracts displayed broad-spectrum antimicrobial activity against clinical, food and environmental pathogens, such as multidrug-resistant Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus and Cryptococcus neoformans. In contrast, the NP2 crude extract displayed antibacterial activity against a limited range of pathogenic and opportunistic pathogens. The serrawettin W1 homologues, in combination with prodigiosin and glucosamine derivatives, produced by pigmented and non-pigmented S. marcescens strains, could thus potentially be employed as broad-spectrum therapeutic agents against multidrug-resistant bacterial and fungal pathogens.

SILVER NANOPARTICLE SYNTHESIS USING ULTRASOUND AND HALLOYSITE TO CREATE A NANOCOMPOSITE WITH ANTIBACTERIAL PROPERTIES

Abstract—The antibacterial nanocomposites creation is a current trend against microbial contamination and microorganism’s biofilm formation. Existing methods for producing nanocomposites based on silver nanoparticles are difficult, expensive, and not environment friendly; therefore it has become necessary to develop a new method for their synthesis that didn’t have these minus. The paper discusses the possibility of silver nanoparticles synthesizing and obtains a new nanocomposite using halloysite nanotubes and ultrasound. Transmission electron microscopy revealed the silver nanoparticles presence on the inner and outer surface of halloysite nanotubes, and sample mapping showed a uniform distribution of silver nanoparticles in the nanocomposite. The antibacterial activity of the obtained nanocomposite against the strain Serratia marcescens (S. marcescens) was more than twice higher than that of the control. The swarming motility method showed that the diameter of migration of S. marcescens was 2.05 ± 0.05 cm, and in the presence of the nanocomposite, it was 1.63 ± 0.04 cm, indicating the ability of the nanocomposite to inhibit biofilm formation in these bacteria. In the future, the obtained nanocomposite can be used as an additive to various materials or as a coating protecting against bacterial contamination of various surfaces and materials.