Enterobacter Amnigenus Research Articles

Microbiological Strategies for Sustainable Production of Bioactive Compounds Using Oil Produced Water Effluent with Sucrose and Crude Glycerine as Carbon Sources

Biopolymers and biosurfactants are bioactive compounds of great commercial interest. They are used for changing fluids viscosity and emulsifying properties of several types of solutions, characteristics necessary for the performance of enhanced oil recovery (EOR) strategies applied at distinct rock formations. The present work evaluated the production of Enterobacter amnigenus exopolysaccharide (EPS) of the strain grown alone or in consortium with Pseudomonas aeruginosa. Culturing was carried out using produced water amended with a mixture of crude glycerin and sucrose as carbon sources. E. amnigenus exopolysaccharide production was low when grown on pure culture, on the other hand, in the presence of P. aeruginosa, the amount of EPSwas of 14.74 gL-1. The produced biopolymer and biosurfactant exhibited excellent viscosity and emulsifyingactivity characteristics for the application in EOR strategies, and better pseudoplastic rheological behavior (was detected) than conventional chemicals used for this purpose. Statistical analysis showed that EPS production was influenced by the interaction between sucrose and glycerin amendments. Infrared absorption spectroscopy showed similar molecular structure to the E. amnigenus FucoPoL. This research shows that a recovering oil fluid can be prepared using produced water as main medium, contributing for reducing costs and increasing environmental gains.

Bacterial and Viral Source Tracking in the Sparkill Creek Watersheds

Microbial contamination of critical water sources is an important issue in urbanized areas faced throughout the world. Particularly concerning in Rockland County, NY is the contamination of the Sparkill Creek. The creek was placed on the “impaired waters list” by the NYS DEC in 2010, and the source and type of contamination has yet to be determined. The Sparkill Creek is unique in that it exceeds the acceptable levels for the indicator organism Enterococcus, specifically 24 times higher than what is allowed. It was our expectation that a thorough examination of multiple indicators and species level determination of the aquatic microbiome would inform the investigation into source of the contamination. The diversity of somatic coliphage and Gram negative bacteria were examined in dry and wet weather conditions, and correlated to nitrate and phosphate levels of the water, along with coliform and E. coli levels. Phage typing using family‐specific primers resulted in the identification of Myoviridae (25%), Siphoviridae (31.25%), and Microviridae (.06%). Plaque size distributions were determined and enough evidence suggests there is a significant difference between collections 1 and 3. Significant differences (p,0.05) were found in levels of E. coli and coliform levels when collections were taken in June and July, while there was not a correlation to nitrate and phosphate levels. A site‐by‐site analysis showed increased significance when looking at E. coli and coliform counts, as the sites approached New Jersey, particularly in Mill pond, Skating pond and the Marsh. Sequencing of cultured bacteria grown on EMB aerobically showed patterns of species found throughout most sites like Enterobacter amnigenus. While some were only specific to site like Brevundimonas diminuta. Stenotrophomonans retroflexus was identified in this way, correlating to only dry weather in 37.2% of the collection. Further investigation into the cause of this correlation is underway.By means of water quality analysis, it is evident that south of the Sparkill Creek, water filtration slows down as it enters Jersey. Upon re‐entering New York, E. coli and coliform counts increase therefore suggesting the contamination exponentially increases in New Jersey. P‐values of less than 0.05 were obtained when comparing Spruce street, (the first site of the Sparkill Creek) and Skating pond (the first site re‐entering New York,) indicates enough evidence to suggest significance amongst the numbers counted. Most significantly, Stenotrophomonas retroflexus, a species novel to the region seems to favor dry conditions as opposed to wet conditions, and was found in 37% of the samples sent for DNA sequencing. Additionally, the emergence of increased amounts of fecal indicators as the creek enters New Jersey provide the public with a better understanding of the source of its contamination.Support or Funding InformationASM‐URF FellowshipThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Identification of potentially pathogenic bacteria from tilapia (Oreochromis niloticus) and channel catfish (Clarias batrachus) culture in Samarinda, East Kalimantan, Indonesia

Hardi EH, Nugroho RA, Saptiani G, Sarinah R, Anggraidini M, Mawardi M. 2018. Identification of potentially pathogenic bacteria from tilapia (Oreochromis niloticus) and channel catfish (Clarias batrachus) culture in Samarinda, East Kalimantan, Indonesia. Biodiversitas 19: 480-488. This research was conducted to isolate, identify, and characterize pathogenic bacteria from feces and water of tilapia (Oreochromis niloticus) and channel catfish (Clarias batrachus) culture from two selected locations in Samarinda, East Kalimantan, Indonesia. Bacteria were cultured and isolated on NA, TSA, and BHIA media at 30oC for 24 h. Colonies of the isolated bacteria were characterized morphologically in terms of their shape, chromogenesis, edge, and size. Antibiotic sensitivity test on each bacterial isolate was completed using inhibition zone tests. Commercial antibiotics used in this research were nitrofurantoin, ciprofloxacin, oxytetracycline, chloramphenicol, nalidixic acid, gentamicin, and norfloxacin. Koch’s postulates test was done by intraperitoneal injection of bacterial suspension to tilapia (15 g weight) at 103-109 CFU mL-1 in triplicates to determine the pathogenicity of each bacterium. Overall, there were 37 isolates obtained from different sources and growth media that belonged to 14 species: Acinetobacter calcoaceticus (1 isolate), Aerococcus urinae (2 isolates), Aerococcus viridans (1 isolate), Aeromonas hydrophila (1 isolate), Citrobacter freundii (5 isolates), Enterobacter amnigenus (2 isolate), Enterobacter cloacae (4 isolates), Escherichia coli (3 isolates), Listeria sp. (1 isolate), Niseria sp. (4 isolates), Pantoea spp. (1 isolate), Pseudomonas aeruginosa (1 isolate), Staphylococcus aureus (9 isolates), and Streptococcus iniae (2 isolates). Sixteen of the isolates were grown in BHIA medium, 12 isolates in TSA medium and 9 isolates in NA medium. The highest mortality was found in tilapia injected with Enterobacter sp., Listeria sp. and Streptococcus sp. at a density of 109 CFU mL-1. However, the number of bacteria causing mortality in fish was approximately 104-108 CFU mL-1. All bacteria detected in the tilapia and channel catfish cultures were also known as putative pathogens in human.

Bile-resistant Gram-negative bacteria effect of different kinds of root decoction pieces

To investigate the microbial contamination in Chinese herbal decoction pieces with different functional types by studying the total aerobic microbial count (TAMC), and total yeast and mould count (TYMC) in 40 samples of 8 types of root decoction pieces; further evaluate the contamination load of bile-resistant Gram-negative bacteria, and identify the Gram-negative bacteria by using biochemical identification system for Gram-negative bacteria. Our results showed that the TAMC value was more than 1 000 CFU•g⁻¹ in 85% (34/40) samples, and was more than 100 CFU•g⁻¹ in 30% (12/40) samples; the contamination of bile-resistant Gram-negative bacteria was detected in 45% (18/40) of the samples. The bile-resistant Gram-negative bacteria load of seven batches of samples was N>1 000 MPN•g⁻¹. Sixteen bacterium strains including Serratia plymouthensis, Cedecea neteri, Escherichia vulneris, Klebsiella oxytoca, Enterobacter amnigenus, E. cloacae, E. sakazakii, Proteus penneri and E. gergoviae were obtained and identified. E. cloacae was the predominant bacterium that was isolated from Salviae Miltiorrhizae Radix et Rhizoma, while E. amnigenus, Yersinia pseudotuberculosis was the typical bacterium of Ophiopogonis Radix and Codonopsis Radix, respectively. All these suggested that the contamination of bile-resistant Gram-negative bacteria was severe for the root decoction pieces in Wuhan city. Microbial species have certain selection specificity for medicinal ingredients, so the type and limit of control bacteria for detection should be formulated according to the pollution type and quantity of bile-resistant Gram-negative bacteria.

Secondary bacterial infections and antibiotic resistance among tungiasis patients in Western, Kenya.

Tungiasis or jigger infestation is a parasitic disease caused by the female sand flea Tunga penetrans. Secondary infection of the lesions caused by this flea is common in endemic communities. This study sought to shed light on the bacterial pathogens causing secondary infections in tungiasis lesions and their susceptibility profiles to commonly prescribed antibiotics. Participants were recruited with the help of Community Health Workers. Swabs were taken from lesions which showed signs of secondary infection. Identification of suspected bacteria colonies was done by colony morphology, Gram staining, and biochemical tests. The Kirby Bauer disc diffusion test was used to determine the drug susceptibility profiles. Out of 37 participants, from whom swabs were collected, specimen were positive in 29 and 8 had no growth. From these, 10 different strains of bacteria were isolated. Two were Gram positive bacteria and they were, Staphylococcus epidermidis (38.3%) and Staphylococcus aureus (21.3%). Eight were Gram negative namely Enterobacter cloacae (8.5%), Proteus species (8.5%), Klebsiellla species (6.4%), Aeromonas sobria (4.3%), Citrobacter species (4.3%), Proteus mirabillis(4.3%), Enterobacter amnigenus (2.1%) and Klebsiella pneumoniae (2.1%). The methicillin resistant S. aureus (MRSA) isolated were also resistant to clindamycin, kanamycin, erythromycin, nalidixic acid, trimethorprim sulfamethoxazole and tetracycline. All the Gram negative and Gram positive bacteria isolates were sensitive to gentamicin and norfloxacin drugs. Results from this study confirms the presence of resistant bacteria in tungiasis lesions hence highlighting the significance of secondary infection of the lesions in endemic communties. This therefore suggests that antimicrobial susceptibility testing may be considered to guide in identification of appropriate antibiotics and treatment therapy among tungiasis patients.

Enumeration and Identification of Ethanol-Injured Coliform Bacteria Found on Harvest Equipment and its Cross-Contamination with Cabbage

Enumeration and Identification of Ethanol-Injured Coliform Bacteria Found on Harvest Equipment and its Cross-Contamination with Cabbage Although disinfection by sanitizers used to produce packing sheds which helps in preventing cross-contamination between farm equipment and produces, sanitizing agents like ethanol are capable of causing sanitizer-injured bacteria. Using the thin agar layer (TAL) method, the proportion of ethanol-injured coliform bacteria resulting from the use of an alcohol agent containing 1.6% and 47% ethanol was evaluated in pure cultures and in a harvest environment of cabbage, respectively. In pure cultures of Enterobacter cloacae, Escherichia coli, and E. coli O157:H7, ethanol-injured cells were observed at a range of 68-95% by treatment with an alcohol agent. When an alcohol agent was sprayed on harvest equipment including knife, container and gloves, 60% of the total coliforms detected on the knife were injured, but no injured coliforms were detected on the container and gloves. The isolation and identification of coliforms on selective and TAL media from the knife suggested that the ethanol stress caused injury to Enterobacter amnigenus, E. asburiae, and E. kobei. Injured bacteria were not detected on cabbage after harvest using the alcohol spray-treated knife because the species of bacteria found in cabbage (14 species belonging to 11 genera) were different from those on the knife. These results indicate that the sanitizer-injured coliforms would not be present on cabbage when transfer of the bacteria from harvest equipment to the cabbage is prevented or when a suitable sanitizer is used that causes death of the bacteria rather than sanitizer-induced cell injury.

Evaluation of the antibacterial and antioxidant activities of chitosan edible films incorporated with organic essential oils obtained from four Thymus species

The aims of this study were to evaluate, (1) the antibacterial properties, (2) the total phenol content and (3) the antioxidant activity, of chitosan edible films incorporated with certified organic essential oils (EOs) obtained from Thymus zygis, Thymus mastichina, Thymus capitatus and Thymus vulgaris. The agar disc diffusion method was used to determine the antibacterial activities of chitosan edible films while for the antioxidant activity, two different analytical assays were used (DPPH and FRAP). As regard antibacterial activity, films containing only chitosan were not effective against any of tested bacteria. Chitosan films containing T. capitatus EO (CH+TCEO) was more effective against Listeria innocua and Alcaligenes faecalis whilst chitosan films containing T. mastichina EO (CH+TMEO) had the highest inhibition halos against Serratia marcescens. For and Enterobacter amnigenus no antibacterial activity was achieved. Chitosan films added with Thymus essential oils showed antioxidant activity, at all concentrations and with all methods assayed. CH+TZEO had the highest antioxidant activity revealed with DPPH assay. However in CH+TCEO showed best antioxidant effect when assessed with FRAP assay. The results showed that chitosan edible films incorporated with organic Thymus EOs could be used as active films in food industry due to its antibacterial and antioxidant activities.

Antimicrobial resistance patterns of Enterobacteriaceae in European wild bird species admitted in a wildlife rescue centre.

Wild birds have been considered to be reservoirs of enteric human pathogens and vectors of resistance dissemination to the environment. During annual migration, they potentially play a role in the epidemiology of human associated zoonoses. The aim of this study was to investigate the frequency of isolation and antimicrobial susceptibility profiles of Enterobacteriaceae members isolated from cloacal swabs of common European wild birds. Fifty-five cloacal swabs were taken during birds' entrance evaluation in a rescue centre for injured wild birds in the Province of Messina (Sicily, Italy). All samples were examined for the presence of members of the family Enterobacteriaceae using standard methods and on the isolated strains antibiotic susceptibility testing was performed. Eighty three Enterobacteriaceae strains were isolated from raptors, waterbirds and passerines. The bacterial species isolated were: Escherichia coli, Proteus mirabilis, Proteus vulgaris, Citrobacter freundii, Enterobacter cloacae, Klebsiella oxytoca, Salmonella Typhimurium, Escherichia vulneris, Enterobacter amnigenus biogroup 2, Salmonella Duesseldorf and Hafnia alvei. The isolates showed significant frequencies of antibiotic resistance. Multiresistance to three or more groups of antibiotics also occurred. None of them have shown a phenotypic Extended Spectrum Beta Lactamase (ESBL) profile.

Prevalence and antimicrobial resistance pattern of bacterial strains isolated from patients with urinary tract infection in Messalata Central Hospital, Libya.

To investigate the prevalence of urinary tract infection among patients at Messalata Central Hospital, Libya, to identify the causative bacteria, and to explore their resistance pattern to antimicrobials. A total number of 1153 urine samples were collected from patients, who attended daily to Messalata Central Hospital, Libya, in a study extended for one year. Antimicrobial susceptibility testing and isolates typing were done using Phoenix BD (BD diagnostic). Resistance was confirmed manually using agar disk diffusion method. Of the 1153 urine samples tested, 160 (13.9%) samples were positive, from which 17 different, solely Gram negative, uropathogens were identified. Escherichia coli were the most prevalent (55.6%) bacteria, followed by Klebsiella pneumoniae subspecies pneumoniae (16.3%), Proteus mirabilis (6.3%), Pseudomonas aeruginosa (5.6%), Enterobacter cloacae and Klebsiella oxytoca (2.5%, each), Citrobacter koseri and Providencia rettgeri (1.9%, each), Acinetobacter baumannii, Enterobacter aerogenes and Proteus vulgaris (1.3%, each), and Aeromonas caviae, Citrobacter freundii, Cronobacter sakazakii, Enterobacter amnigenus biogroup 2, Pseudomonas putida and Serratia marcescens (0.6%, each). The isolated uropathogens showed increased levels of resistance ranged from 10.5% to 64.5%, with an overall resistance of 28.9%. Amikacin was the most effective antimicrobial followed by Imipenem and Meropenem (0%, 0.6% and 2.5% resistance, respectively); while, Cephalothin and Ampicillin were the least (80.6% and 90.0% resistance, respectively) effective. The obtained results emphasized the emergence of highly resistant bacteria to most of tested antimicrobials and raise the alarm for physicians to change their treatment pattern depending on antimicrobial susceptibility results.

Occurrence and analysis of irp2 virulence gene in isolates of Klebsiella pneumoniae and Enterobacter spp. from microbiota and hospital and community-acquired infections

Eighty-five isolates of Klebsiella pneumoniae and Enterobacter spp., originating from hospital- and community-acquired infections and from oropharyngeal and faecal microbiota from patients in Recife-PE, Brazil, were analyzed regarding the presence of irp2 gene. This is a Yersinia typical gene involved in the synthesis of siderophore yersiniabactin. DNA sequencing confirmed the identity of irp2 gene in five K. pneumoniae, five Enterobacter aerogenes and one Enterobacter amnigenus isolates. To our knowledge in the current literature, this is the first report of the irp2 gene in E. amnigenus, a species considered an unusual human pathogen, and in K. pneumoniae and E. aerogenes isolates from the normal microbiota and from community infections, respectively. Additionally, the analyses of nucleotide and amino acid sequences suggest the irp2 genes derived from isolates used in this study are more closely related to that of Yersinia pestis P.CE882 than to that of Yersinia enterocolitica 8081. These data demonstrated that K. pneumoniae and Enterobacter spp. from normal microbiota and from community- and hospital-acquired infections possess virulence factors important for the establishment of extra-intestinal infections.

Potential Bacterial Zoonotic Pathogens Isolated from a Major Abattoir and its Receiving Surface Water in Abeokuta, Nigeria

The rapid pace and scale of urbanization in Nigeria has led to large volumes of domestic and industrial wastes, which pose threats to the environment and public health. Currently, in Nigeria, there seems to be neither sufficient measures nor facilities to treat abattoir effluents for environmental safety or to recover usable energy and material from abattoir by-products. This study was conducted to assess the microbial status of the Lafenwa abattoir effluent and its receiving surface water. The Total viable and Coliform counts (TBC and TCC) using surface plating and multiple tube test techniques, respectively were performed. Bacterial contaminants were isolated and identified by standard microbiological procedures. Furthermore, various methods for waste disposal at the abattoir were assessed. The mean TBC and TCC for waste water during and after slaughtering were 5.2x107, 4.9x107 and 4.26x107, 3.06x107 cfu/ml respectively. The receiving surface water had mean TBC and TCC of 4.15x107, 3.83x107, and 3.89x107, 2.87x107 cfu/ml respectively. Waste disposal in the abattoir was by open dumping of solid wastes while effluent was discharged into the nearby Ogun River, which is also used by butchers for meat processing. Bacterial organisms isolated from the effluent include Enterobacter aerogenes, Hafnia alvei, Erwinia mallotivora, Edwardsiella ictaluri, Enterobacter amnigenus and Escherichia coli O157strains while Proteus miriabilis, Staphylococcus spp, Pseudomonas aeruginosa, Enterobacter intermedius, Yersinia aleksiciae, Serratia odorifera, Enterobacter cloacae, Enterobacter aerogens and Eschericia coli O157 strains were isolated from the surface water. The high microbial load and the isolation of pathogenic organisms of public health importance especially Escherichia coli O157 strains further demonstrates the need for adequate waste disposal and treatment. Also, the current methods of waste disposal at the abattoir greatly reduces the quality of the surrounding environment and portends a risk to public health and food safety.

Bioremediation of Cr(VI) by Enterobacter amnigenus EA31 isolated from tannery waste contaminated soil

A novel chromium resistant and reducing bacterium was isolated from tannery waste contaminated soil. On the basis of different morphological, biochemical characteristics and 16S rRNA gene analysis the strain was identified as Enterobacter amnigenus EA31. The strain reduced Cr(VI) under a wide range of concentrations from 100 to 400 mg/L with a maximumat 100 mg/L. Optimum temperature and pH being 37°C and 9 respectively for maximum chromium reduction. The bacterial culture were repeatedly added with 25 mg/L Cr(VI) until saturation in Cr(VI) reduction was observed. Repeated detoxification of 25 mg/L Cr(VI) could be achieved up to three consecutive inputs. The suspended culture repeatedly reduced 25 mg/L Cr(VI) within 6 h up to three consecutive inputs. The reduction of chromium occurred even in the presence of high concentration of other heavy metals. Assay with resting and permeabilised cells (treated with toluene and Triton X-100) demonstrated that Cr(VI) reduction activity was soluble and not tightly bound to the cell membrane. Inoculation with E. amnigenus improved the growth parameters of wheat and clover under chromium stress. The results suggest that E. amnigenus can be exploited for bioremediation of chromium under various environmental conditions.

Bioremediation of Cr(VI) by Enterobacter amnigenus EA31 isolated from tannery waste contaminated soil

A novel chromium resistant and reducing bacterium was isolated from tannery waste contaminated soil. On the basis of different morphological, biochemical characteristics and 16S rRNA gene analysis the strain was identified as Enterobacter amnigenus EA31. The strain reduced Cr(VI) under a wide range of concentrations from 100 to 400 mg/L with a maximumat 100 mg/L. Optimum temperature and pH being 37°C and 9 respectively for maximum chromium reduction. The bacterial culture were repeatedly added with 25 mg/L Cr(VI) until saturation in Cr(VI) reduction was observed. Repeated detoxification of 25 mg/L Cr(VI) could be achieved up to three consecutive inputs. The suspended culture repeatedly reduced 25 mg/L Cr(VI) within 6 h up to three consecutive inputs. The reduction of chromium occurred even in the presence of high concentration of other heavy metals. Assay with resting and permeabilised cells (treated with toluene and Triton X-100) demonstrated that Cr(VI) reduction activity was soluble and not tightly bound to the cell membrane. Inoculation with E. amnigenus improved the growth parameters of wheat and clover under chromium stress. The results suggest that E. amnigenus can be exploited for bioremediation of chromium under various environmental conditions.

Assessment of species and antimicrobial resistance among Enterobacteriaceae isolated from mallard duck faeces.

Mallard ducks have demonstrated to be a likely reservoir for zoonotic E. coli strains; thus, it is possible that these ducks could also act as a reservoir for other Enterobacteriaceae members. The present study was initiated to evaluate the species distribution of Enterobacteriaceae other than E. coli in 175 fresh faecal samples collected from a population of mallard ducks. Sixty-four samples displayed detectable colonies of Enterobacteriaceae (excluding E. coli), which resulted in 75 pulsed-field gel electrophoresis (PFGE) types. Seventy-five single representatives of each PFGE type were subjected to identification with API 32NE and MALDI TOF MS systems due to the practical difficulties in species differentiation of Enterobacteriaceae. Those isolated were found to be from nine genera: Buttiauxella (15 %), Citrobacter (5 %), Enterobacter (32 %), Hafnia (1 %), Leclercia (1 %), Pantoea (7 %), Raoultella (21 %), Rahnella (7 %) and Serratia (11 %). Evaluation of antimicrobial resistance phenotypes using the disc method and detection of resistance genes using the microarray method revealed that these microbes possess resistance to β-lactams, aminoglycosides, macrolides, quinolones, rifamycine, sulphonamides, streptogramins and diaminopyrimidines. In conclusion, mallard ducks harbour a variety of non-pathogenic and pathogenic Enterobacteriaceae species like Enterobacter cloacae and Enterobacter amnigenus in their intestine and could act as a reservoir of resistant Enterobacteriaceae.

Isolation and Molecular Characterization of Multidrug-Resistant Enterobacteriaceae Strains from Pork and Environmental Samples in Xiamen, China

This study was conducted to investigate the prevalence and molecular characterization of multidrug-resistant (MDR) Enterobacteriaceae isolated from swine meat and the breeding environment. A total of 102 MDR Enterobacteriaceae strains belonging to five genera were obtained from 210 samples collected from a large-scale swine farm from March 2012 to June 2013 in Xiamen, People's Republic of China. Among these MDR isolates, Escherichia coli strains were found most frequently in both meat and environmental samples, followed by Citrobacter spp., Klebsiella spp., and Shigella spp. The neighbor-joining phylogenetic tree indicated that 70.3% of Escherichia and 50% of Citrobacter isolates from meat samples shared 100% homology with relevant isolates from environmental samples. Resistance was most frequently observed to sulfonamide, trimethoprim, aminoglycoside, chloramphenicol, β-lactam, and tetracycline. Close correlation was noted between antibiotic resistance phenotype and the genes responsible for resistance to sulfonamide (sulI), trimethoprim (dhfrI), aminoglycoside (aadA, aac(3)-I, aphA-1, and aac(3)-IV), chloramphenicol (catI and cmlA), b-lactam (blaSHV, blaOXA, and blaTEM), florfenicol (floR), and tetracycline (tet(A) and tet(B)), which were widely distributed with prevalences of 72.5, 6.9, 62.7, 14.7, 78.4, 11.8, 25.5,42.2, 12.7, 14.7, 39.2, 87.2, 68.6, and 34.3%, respectively. Class 1 integrons carrying aadA22, dfrA17-aadA5, or dfrA12-aadA2 cassette arrays were commonly found in isolates from all samples. The gene cassette aac(6' )-Ib-cr-arr-3-dfrA27-aadA16 was first found in an Enterobacter amnigenus isolate. Conjugation experiments revealed the plasmid-mediated transfer of class 1 integrons. Our results indicate that swine meat and the farming environment can be sources of antibiotic-resistant bacteria, which could be potentially transmitted to humans via the meat products industry chain.

Chromium Resistant Bacteria: Impact on Plant Growth in Soil Microcosm

Abstract Three chromium resistant bacterial strains, Pseudomonas fluorescens PF28, Enterobacter amnigenus EA31 and Enterococcus gallinarum S34 isolated from tannery waste contaminated soil were used in this study. All strains could resist a high concentration of K2Cr2O7 that is up to 300 mg/L. The effect of these strains on clover plants (Trifolium campestre) in the presence of two chromium salts CrCl3 and K2Cr2O7 was studied in soil microcosm. Application of chromium salts adversely affected seed germination, root and shoot length. Bacterial inoculation improved the growth parameters under chromate stress when compared with non inoculated respective controls. There was observed more than 50% reduction of Cr(VI) in inoculated soil microcosms, as compared to the uninoculated soil under the same conditions. The results obtained in this study are significant for the bioremediation of chromate pollution.

Histamine content and histamine-forming bacteria in mahi-mahi (Coryphaena hippurus) fillets and dried products

Forty-two mahi-mahi fillets and 17 dried products sold in retail markets in Taiwan were tested for histamine and histamine-forming bacteria. The levels of pH, salt content, water content, Aw, TVBN, APC, TC and Escherichia coli in mahi-mahi fillet samples ranged from 5.6 to 6.5, 0.05 to 2.44%, 70.9 to 82.8%, 0.95 to 0.99, 5.9 to 23.5 mg/100 g, 3.1 to 7.0 log CFU/g, <3 to 1650 MPN/g and <3 to 45 MPN/g, respectively. The levels of pH, salt content, water content, Aw, TVBN, APC, TC and E. coli in dried mahi-mahi samples ranged from 5.7 to 6.4, 0.63 to 20.13%, 7.1 to 42.9%, 0.51 to 0.85, 21.4 to 133.9 mg/100 g, 3.6 to 8.7 log CFU/g, <3 to 5900 MPN/g and <3 to 2500 MPN/g, respectively. The average content of various biogenic amines in fillets samples was less than 0.3 mg/100 g. Four of the 17 dried samples (23.4%) had histamine levels greater than the FDA guideline of 5 mg/100 g for scombroid fish and/or product with one of them containing 68.15 mg/100 g of histamine, which is greater than the 50 mg/100 g hazard action level. Eight histamine-producing bacterial isolates, capable of producing 12.6 ppm–562 ppm of histamine in trypticase soy broth supplemented with 1.0% l-histidine (TSBH), were identified as Raoultella ornithinolytica (three isolates), Pantoea agglomerans (two isolates), Proteus vulgaris (two isolates) and Enterobacter amnigenus (one isolate), by 16S rDNA sequencing with PCR amplification.

Antibacterial activity of Borago officinalis and Brassica juncea aqueous extracts evaluated in vitro and in situ using different food model systems

The present study was undertaken to characterize the antibacterial activity of the aqueous extracts (AEs) obtained from the leaves of Borago officinalis L. and Brassica juncea L. The antagonistic activity was evaluated against several bacteria (42 strains of Listeria monocytogenes, 35 strains of Staphylococcus aureus, 38 strains of Enterobacter spp. and 18 strains of Salmonella enterica) commonly associated with foodborne diseases by paper disc diffusion method. The susceptibility to the plant extracts was strain specific. Thirty-five strains (7 L. monocytogenes, 11 S. aureus, 1 S. Enteritidis, 1 S. Veneziana, 7 Enterobacter hormaechei, 5 Enterobacter cloacae, 1 Enterobacter sakazakii and 2 Enterobacter amnigenus) were sensitive to both AEs. The activity of B. juncea AE towards the Gram-positive strains was generally higher than that observed for B. officinalis (45 and 22 strains inhibited by B. juncea and B. officinalis, respectively), while an opposite trend was registered against the Gram-negative strains (22 and 35 strains inhibited by B. juncea and B. officinalis, respectively). The highest inhibition was displayed by B. juncea AE against E. sakazakii 23A. B. officinalis AE showed the same minimum inhibitory concentration (MIC) (10 mg/mL) for the majority of the most sensitive strains, while the MIC of B. juncea AE was different for each bacterial species and the lowest concentration was registered to inhibit enterobacteria (3.1 mg/mL). After 1-year storage in different thermal conditions (room temperature, 4 °C and −20 °C), both AEs lost their inhibitory power. The extracts did not show cellular toxicity when tested against sheep erythrocytes. Hence, B. officinalis and B. juncea AEs were effective as natural antibacterial substances. AEs were tested in situ in three food model systems (meat, fish and vegetable) at two concentrations, but only when added at a concentration 10-fold higher than that showing definite efficacy in vitro (100 and 31 mg/mL for B. officinalis and B. juncea, respectively), they inhibited the growth of the sensitive strains, even though the cells were still viable after 24 h. The influence of AEs on the volatile organic compounds (VOCs) composition of the food models was analysed by gas chromatography/mass spectrometry. The different levels of alcohols, aldehydes, esters, hydrocarbons, ketones and phenol registered, showed a consistent effect of B. officinalis and B. juncea AEs on the VOCs of the food models. However, the sniffing assay found only B. juncea AE impacting consistently the final aroma of the food models.

Expression of mosquito-larvicidal toxin genes under the control of a native promoter in Enterobacter amnigenus An11

Enterobacter amnigenus An11, that can colonize the gut of mosquito larva, is an alternative toxin-producing host to be used as a mosquito control since it is able to float in the feeding zone of mosquito larvae. To produce mosquito-larvicidal toxins in this bacterium, a native promoter has been identified from its genomic DNA. The promoter exhibited consensus sequences for -35 and -10 regions of bacterial promoters and constitutively drove the expression of gfp. This promoter was inserted into recombinant plasmids upstream of promoter-free cyt2Aa2 from Bacillus thuringiensis and mtx2 from Bacillus sphaericus. Results demonstrated that Cyt2Aa2 and Mtx2 are constitutively produced without induction. The recombinant E. amnigenus showed toxicity against mosquito larvae, demonstrating a potential to be applied in a mosquito control program.

원유 내 내냉성 미생물의 계절별, 지역별 분포 및 동정

To investigate the distribution of psychrotrophic bacteria, raw milk was collected from farms in nine different regions located around Kyunggi province in South Korea at four different seasons. Psychrotrophic counts were higher in winter than in other seasons as 3.0×10 4 CFU/mL (p<0.05). Among nine regions, the population in raw milk sampled from B region was in significantly greater numbers and those from C and D province were in significantly lower numbers than any other regions, 2.4×10 5 CFU/mL and 8.7×10 3 CFU/mL, respectively (p<0.05). In addition, among 706 bacterial isolates, the predominant class was Gamma-proteobacteria (81.02%) and genus was Pseudomonas (32.34%), especially Pseudomonas fluorescens (39.46%). Compared to the regional predominance, Acinetobacter johnsonii in A region, Pseudomonas fluorescens in B region, Enterobacter amnigenus in C region, Psychrobacter maritimus in D region, Acinetobacter johnsonii in E region, Acinetobacter haemolyticus in F region, Pseudomonas fluorescens in G region, Acinetobacter jounsonii in H region, and Pseudomonas mucidolens in I region were found.