Mariana Marhova | University of Plovdiv (original) (raw)

Papers by Mariana Marhova

Journal of BioScience and Biotechnology, 2018

The present study is focused on the antibiotic and serum resistance of Enterobacteriaceae strains... more The present study is focused on the antibiotic and serum resistance of Enterobacteriaceae strains associated with community infections of the urogenital tract. During a one-year period from April 2016 to March 2017 total of 318 Enterobacteriaceae strains were collected from urine samples, vaginal and urethral secrets and ejaculates of outpatients with urinary and genital tract infections at IMDL "Chronolab"-Plovdiv, Bulgaria. The most common etiological agent was Escherichia coli (64.8%), followed by Klebsiella spp. (17%) and Proteus mirabilis (10.37%). The antibiotic susceptibility tests showed high resistance against ampicillin (49%), mecillinam (71%), doxycycline (41%) and high susceptibility to cephalosporins (cefuroxime 84.6%; cefoxitin 83.7%; cefotaxime 91.5%; cefepime 87.7%) and fluoroquinolones (ciprofloxacin 85%, norfloxacin 79%, levofloxacin 83%;). Significant resistance was established to nitrofurantoin (24%). Amongst the tested strains, 8.5% produced extended spectrum beta-lactamases (ESBLs). We tested serum susceptibility of strains and found that 84% of strains were resistant to the bactericidal activity of the normal human serum. Our data suggest that most likely the resistance to complement is one of the mandatory virulence factors for the majority of the Enterobacteriaceae strains associated with urogenital infections. The susceptibility profile of the tested Enterobacteriaceae strains confirms the need for constant data update on the antibiotic resistance and patterns of virulence of etiological agents of the urogenital infections.

Ecologia Balkanica, 2019

The present study analyzed the interactions between the environmental parameters, microbiological... more The present study analyzed the interactions between the environmental parameters, microbiological water quality indicators, and phytoplankton in Kardzhali reservoir, which is one of the largest and economically significant water bodies in Bulgaria, with highly developed cage- aquaculture. Data sets of eighteen parameters from 5 monitoring sites during 2016–2018 were used for analysis. We have applied multivariate methods, aiming to identify the key parameters affecting the communities, including the impact of the net-cage farms. The ANOSIM (analysis of similarities), showed significant differences in the values of physicochemical factors between the control site and the area for aquaculture, with higher nitrate, total nitrogen, and COD (chemical oxygen demand) content near the net-cages. The results were confirmed by the high R-value (R=0.87; p<0.01). The conducted PCA (principal component analysis) showed that only three principal components (PCs) are need to group the physicoch...

Journal of BioScience and Biotechnology, 2018

The present study is focused on the antibiotic and serum resistance of Enterobacteriaceae strains... more The present study is focused on the antibiotic and serum resistance of Enterobacteriaceae strains associated with community infections of the urogenital tract. During a one-year period from April 2016 to March 2017 total of 318 Enterobacteriaceae strains were collected from urine samples, vaginal and urethral secrets and ejaculates of outpatients with urinary and genital tract infections at IMDL "Chronolab" - Plovdiv, Bulgaria. The most common etiological agent was Escherichia coli (64.8%), followed by Klebsiella spp. (17%) and Proteus mirabilis (10.37%). The antibiotic susceptibility tests showed high resistance against ampicillin (49%), mecillinam (71%), doxycycline (41%) and high susceptibility to cephalosporins (cefuroxime 84.6%; cefoxitin 83.7%; cefotaxime 91.5%; cefepime 87.7%) and fluoroquinolones (ciprofloxacin 85%, norfloxacin 79%, levofloxacin 83%;). Significant resistance was established to nitrofurantoin (24%). Amongst the tested strains, 8.5% produced extended...

Journal of BioScience and Biotechnology, 2018

The current study aimed to examine the amylolytic activities of various species of the Bacillus g... more The current study aimed to examine the amylolytic activities of various species of the Bacillus genus. A total of 31% of the tested 166 strains showed a positive reaction on starch agar. Their amylolytic activity was in the range of 0.9 to 2.8 U/ml. Bacillus cereus №10 showed the highest initial activity, established in the late stationary phase of growth (36 hours of incubation). The effects of different nitrogen sources, metal ions and different type of secondary carbon sources (starch was used as a primary carbon source) on the production of amylase by the screened strain were studied. The enzyme production was significantly influenced by the type and concentration of the secondary carbon source. Replacement of peptone by yeast extract and the addition of 1 mM Ca2+ increased initial amylolytic activity by 153% reaching 4.29±0.63 U/ml.

Ecologia Balkanica, 2018

The aim of this study was to determine the current microbiological status of the microbial commun... more The aim of this study was to determine the current microbiological status of the microbial communities and their ability to form biofilms in two protected by Natura 2000 wetlands in Southern Bulgaria. The numbers of heterotrophic bacteria (TVC22 and TVC 37), actinomycetes, fungi, and sanitary state indicators were determined for dry soil samples and sediments collected form Zlato pole wetland and Tsalapitsa rice paddies. The number of heterotrophic microorganisms (TVC22 and TVC 37) and indicators of sanitary status (FS, FC, and Escherichia coli) in the two rice paddies near the city of Plovdiv is higher in comparison to the control zone Zlato pole – the maximum was recorded in the rice paddy near Tsalapitsa village (C1 and C2 was 12.6х106 cfu.g-1 and 26х106 cfu.g-1, respectively). In the studied samples, the bacterial complex takes a dominant position and it exceeds the number of both fungus and actinomycetes at least 1.5 times. The cluster analysis showed a high similarity between ...

Journal of BioScience and Biotechnology, 2019

Enterococci are increasingly associated with infections of the urogenital tract. The two species ... more Enterococci are increasingly associated with infections of the urogenital tract. The two species Enterococcus faecalis and Enterococcus faecium are the third most commonly isolated pathogens in catheter-associated urinary tract infections (CAUTI). Both species are capable of producing biofilms, with E. faecalis being more frequently isolated. This study explores the antimicrobial resistance and biofilm formation ability of 72 Enterococcus faecalis strains, collected a one-year period from the urogenital tract of outpatients. The results showed that urinary tract infections (UTI), caused by enterococci are more frequent among children up to 10 years of age, while genital tract infections (GTI) are most often observed in women in reproductive age. Antimicrobial resistance was low, with higher levels for UTI compared to GTI strains. The results demonstrate 100% susceptibility to penicillins, which are the most effective agents for the treatment of infections caused by Enterococcus faec...

The study is focused on the etiological structure and drug resistance of bacterial strains causin... more The study is focused on the etiological structure and drug resistance of bacterial strains causing upper respiratory tract infections, which are widely spread amongst children. The aim is to update the data about antimicrobial susceptibility and to establish virulence factors important for infectious process for Staphylococcus spp. isolates from the upper respiratory tract. A total of 711 strains were isolated from outpatients with nasal and oropharyngeal infections at Medical Diagnostic Laboratories "Sinevo-Bulgaria" LTD in Plovdiv for a two-year period 2019-2020. The results demonstrate that the etiological structure is highly related to the site of infection. Branhamella catarrhalis was found to dominate in the samples from the oropharynx (40%), while the majority of isolates from the nasal and ear samples were identified as Staphylococcus aureus - 65% and 35% respectively. S. aureus showed higher drug resistance compared to other isolates, reaching up to 70% to penicil...

The application of phospholipases produced by species of genus Bacillus in different industries r... more The application of phospholipases produced by species of genus Bacillus in different industries reduces the negative impact on the environment by reducing the need of toxic chemicals, consumed energy, and produced carbon emissions. In the current study one hundred sixty-six bacterial strains belonging to the genus Bacillus were tested for phospholipase C production. Eighty-seven percent of the studied strains demonstrated phospholipase C activity on egg-yolk agar. Strain Bacillus thuringiensis was selected as the most promising for the phospholipase production with initial activity of 19.61 U/ml. The nutrient medium composition and cultivating conditions were optimized for achieving higher enzyme yields. The highest phospholipase production was achieved on the following conditions of the liquid medium: 1% of yeast extract as a source of nitrogen; 0.5% NaCl; 0.4% of glucose as a carbon source; NaHCO3 – 3 g/l; Na2HPO4 – 0.4 g/l; 1 mM ZnCl2; pH 7; inoculated with 3% (1.4 x 109 cfu/ml) ...

This study explored the spatial differences and physiological diversity of soil microbial communi... more This study explored the spatial differences and physiological diversity of soil microbial communities in natural wetland and constructed rice paddies in the Maritsa River Basin, protected under the Birds Directive 2009/147/EC as natural habitats. Community level physiological profiling was used to characterize the metabolic function of the communities. The microbial activity expressed, as average well colour development (AWCD) and substrate richness and diversity was higher in the non-flooded soils with no significant spatial differences. Individual carbon source utilization patterns (CSUPs) segregated the paddy fields profiles from the natural wetland sediments and showed that communities` metabolic functions were strongly influenced by rice cropping and not by the sample location. The CUSPs revealed that easily degradable carbohydrates were the most widely used substrates followed by amino acids, carboxylic acids, and polyols. Natural wetland communities held an isolated position ...

Urinary tract infections are serious health and economic burden for society. Selected bacterial s... more Urinary tract infections are serious health and economic burden for society. Selected bacterial species as Escherichia coli, Klebsiella spp., Proteus spp. are often isolated from patience’s urine samples. We investigated twenty strains Escherichia coli, isolated from urine of 14 patients with different urinary infections, 4 patients with asymptomatic bacteriuria and 2 pregnant women. Distribution of virulence determinants as adhesins, motility, hemolysins, serum resistance and biofilm-forming were investigated phenotypically and with multiplex PCR in correlation. We found that strains poses different combinations of virulence capabilities and the structure statistically most often found is the type 1 pili.

One hundred sixty-six bacterial strains belonging to genus Bacillus were tested for protease prod... more One hundred sixty-six bacterial strains belonging to genus Bacillus were tested for protease production. Ninety percent of the studied strains demonstrated protease activity on nutrient gelatin and milk agar. A strain Bacillus thuringiensis was selected as the most promising for enzyme production based on its initial enzyme activity of 9.2 U/ml. The nutrient medium composition and cultivating conditions were optimized aiming better yields. The highest protease activity of 15 U/ml was achieved on the following conditions: inoculation of the medium with 5% inoculum (6.0 McF), followed by 16 hours of cultivation in liquid medium containing 0.5% glucose, 0.55% Bacto Peptone, 50mM phosphate buffer and 0.2% magnesium ions. The produced enzymes were partially purified 5.6 fold by ultrafiltration and size-exclusion chromatography on Sephadex G-75 and had a specific activity of 17.7 U/mg. The approximate molecular weights were determined by SDS-PAGE to be between 45 and 66 kDa.

Pseudomonas strains were examined for the production of lipolytic enzymes. Bacteria synthesize ex... more Pseudomonas strains were examined for the production of lipolytic enzymes. Bacteria synthesize extracellular lipase and phospholipase type-C. The majority of the strains of Pseudomonas sp. are producers of lipase and phospholipase-C. Phospholipase-C activity is maximal in the initial stationary phase – 12 th hour, while the maximum lipase secretion found in the late stationary phase. The production of both enzymes is positively influenced by the addition of extra carbon sources at a concentration of 0.5% for soybean-casein medium that is suitable for cultivation of species Pseudomonas.

Biotechnology & Biotechnological Equipment, 2019

Microbial communities drive the biogeochemical cycles in wetlands and provide a number of ecosyst... more Microbial communities drive the biogeochemical cycles in wetlands and provide a number of ecosystem services. They underpin soil function, and are easily impacted by anthropogenic pressure. This study examined the bacterial microbiome in the natural wetland of Zlato Pole and the protected, periodically flooded rice paddies in the Maritsa River Basin using a metagenomic approach, based on high-throughput sequencing. Alpha-diversity analysis showed a significant variation between the three study sites for Chao1 and ACE (abundance based coverage estimator) richness estimators. A positive correlation was established with pH, with highest values detected for the rice paddies and the lowest, for the Zlato Pole sediments. The obtained sequences were assigned into 37 known bacterial phyla with over 97% bacterial sequences classified within only nine of them. The bacterial communities in rice paddies sediments were more evenly distributed, whereas the Zlato Pole sediment was the most biased. The consortiums in the rice paddies were dominated by Proteobacteria, followed by Actinobacteria and Acidobacteria. The bacterial assemblages in those sites could not be distinguished by analysis of similarity. The Zlato Pole sediment community held an isolated position, where Acidobacteria was replaced by Firmicutes and Bacteroidetes and the microbiome showed an extremely high abundance of Gammaproteobacteria and Bacilli. The dominance of Gammaproteobacteria and the presence of Deinococcus-Thermus phylum, along lower nutrient concentration and the absence of correlation with the environmental parameters, is evidence of constant anthropogenic pressure around the area. The obtained results could be applied in the plans for sustainable management of the protected wetlands.

Biotechnology & Biotechnological Equipment, 2009

Current knowledge on antimicrobial susceptibility pattern of uropathogens is necessary for approp... more Current knowledge on antimicrobial susceptibility pattern of uropathogens is necessary for appropriate therapy. The objective of this study was to investigate antibiotic susceptibility of 28 clinically isolated strains Escherichia coli, associated with different urinary tract infections. Lowest susceptibility detected was for betalactams ampicillin and ampicillin/sulbactam. High susceptibility was detected for aminoglycoside antibiotics. Approximately half of investigated strain showed multidrug resistance profiles. Plasmid content of E. coli isolates was investigated and participation of detected plasmids in drug resistance was discussed. Our data show the high level of antimicrobial resistance and extended spectrum b-lactamases (ESBL) production amongst the uropathogens causing urinary tract infection.

Biotechnology & Biotechnological Equipment, 2010

The aim of the present study was to investigate biofilm-forming capabilities of clinically isolat... more The aim of the present study was to investigate biofilm-forming capabilities of clinically isolated strains Escherichia coli, associated with different urinary tract infections. Biofilm production was detected in 36% of the isolates from UTI. Additionally some of virulence factors are estimated to find correlation between antibiotic resistance, hemolysins, morfotypes and biofilm production. Our data indicate that no combination of VFs was highly associated with biofilm production.

Biotechnology & Biotechnological Equipment, 2011

Materials and Methods Strains, media and cultivation In this study were included three urinary cl... more Materials and Methods Strains, media and cultivation In this study were included three urinary clinically isolated strains with pre-estimated good biofilm growth capacity (11) from the laboratory collection of the Departnemt of Biochemistry and Microbiology, Plovdiv University. PU-1 was isolated from a woman with pyelonephritis, PU-13-from a man with cystitis, and PU-19-from a man with ABU. Estimation of the antibacterial activity of the plant extracts was tested also on reference strains: E. coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923 and Streptococcus saprophyticus nctc 7292. The strains were stored frozen in Trypticase soy broth (TSB) (Difco) supplemented with 30% glycerol. Before use, samples were inoculated into TSB and incubated overnight at

Biotechnology & Biotechnological Equipment, 2015

The aim of the present study was to carry out a preliminary assessment for the occurrence of bact... more The aim of the present study was to carry out a preliminary assessment for the occurrence of bacterial strains resistant to frequently used antibiotics in the sediments beneath the sturgeon cage farm in Kardzhali Dam (Bulgaria). Samples were taken from the top 2 cm of sediments under a fish farm and from a control station in the aquatory of the reservoir in the period JulyÀOctober 2011. Surveillance of bacterial susceptibility to 16 antimicrobial agents was performed for 160 Gram-negative strains (Pseudomonas mandelii À 100 strains; Hafnia alvei À 30 strains; and Raoultella ornithinolytica À 30 strains). No significant differences in the resistance to the tested antibiotics were observed between the strains isolated from the two stations (analysis of variance, P > 0.05). Widespread resistance to penicillins and certain cephalosporin antibiotics was observed in both stations. None of the studied strains showed resistance to the aminoglycoside antibiotics gentamicin and amikacin, or to ciprofloxacin. Minimal Inhibitory Concentrations (MIC) were determined for five of the tested antimicrobial agents by the microdilution antibiotic sensitivity assay. The data indicate that amikacin, tetracycline and ciprofloxacin effectively suppress the growth of the tested microorganisms. The isolates from genus Pseudomonas showed the highest MIC and were characterized by the highest percentage of antibiotic resistance.

ILIEV, I., S. KOSTADINOVA, M. MARHOVA, T. HUBENOVA and A. ZAIKOV, 2015. Microbial status of Dospa... more ILIEV, I., S. KOSTADINOVA, M. MARHOVA, T. HUBENOVA and A. ZAIKOV, 2015. Microbial status of Dospat Dam Lake, Bulgaria. Bulg. J. Agric. Sci., Supplement 1, 21: 33–39 The aim of this study was to determine the total count of main microbial indicators for the water quality of Dospat Dam Lake. Samples were taken from six stations situated in the aquatory of the reservoir and one station at Dospatska River. The seasonal dynamics of the total viable count (TVC 20°C), total coliforms (TC), E. coli, fecal streptococci (FS) and C. perfringens were studied for the period April 2011 – March 2012. The values for the TVC 20oC were within range of 1.103cfu.100 mL–1 to 39.103 cfu.100 mL–1, without statistically signifi cant differences between stations (ANOVA, P > 0.05). The average values for TC varied from 10 cfu.100 mL–1 to 100 cfu.100 mL–1 and in August it rose to 1000 cfu.100 mL–1 with higher numbers near the net cage farms (ANOVA, P < 0.005). Presence of E. coli, FS and C. perfringens ...

Journal of BioScience and Biotechnology, 2018

The present study is focused on the antibiotic and serum resistance of Enterobacteriaceae strains... more The present study is focused on the antibiotic and serum resistance of Enterobacteriaceae strains associated with community infections of the urogenital tract. During a one-year period from April 2016 to March 2017 total of 318 Enterobacteriaceae strains were collected from urine samples, vaginal and urethral secrets and ejaculates of outpatients with urinary and genital tract infections at IMDL "Chronolab"-Plovdiv, Bulgaria. The most common etiological agent was Escherichia coli (64.8%), followed by Klebsiella spp. (17%) and Proteus mirabilis (10.37%). The antibiotic susceptibility tests showed high resistance against ampicillin (49%), mecillinam (71%), doxycycline (41%) and high susceptibility to cephalosporins (cefuroxime 84.6%; cefoxitin 83.7%; cefotaxime 91.5%; cefepime 87.7%) and fluoroquinolones (ciprofloxacin 85%, norfloxacin 79%, levofloxacin 83%;). Significant resistance was established to nitrofurantoin (24%). Amongst the tested strains, 8.5% produced extended spectrum beta-lactamases (ESBLs). We tested serum susceptibility of strains and found that 84% of strains were resistant to the bactericidal activity of the normal human serum. Our data suggest that most likely the resistance to complement is one of the mandatory virulence factors for the majority of the Enterobacteriaceae strains associated with urogenital infections. The susceptibility profile of the tested Enterobacteriaceae strains confirms the need for constant data update on the antibiotic resistance and patterns of virulence of etiological agents of the urogenital infections.

Ecologia Balkanica, 2019

The present study analyzed the interactions between the environmental parameters, microbiological... more The present study analyzed the interactions between the environmental parameters, microbiological water quality indicators, and phytoplankton in Kardzhali reservoir, which is one of the largest and economically significant water bodies in Bulgaria, with highly developed cage- aquaculture. Data sets of eighteen parameters from 5 monitoring sites during 2016–2018 were used for analysis. We have applied multivariate methods, aiming to identify the key parameters affecting the communities, including the impact of the net-cage farms. The ANOSIM (analysis of similarities), showed significant differences in the values of physicochemical factors between the control site and the area for aquaculture, with higher nitrate, total nitrogen, and COD (chemical oxygen demand) content near the net-cages. The results were confirmed by the high R-value (R=0.87; p<0.01). The conducted PCA (principal component analysis) showed that only three principal components (PCs) are need to group the physicoch...

Journal of BioScience and Biotechnology, 2018

The present study is focused on the antibiotic and serum resistance of Enterobacteriaceae strains... more The present study is focused on the antibiotic and serum resistance of Enterobacteriaceae strains associated with community infections of the urogenital tract. During a one-year period from April 2016 to March 2017 total of 318 Enterobacteriaceae strains were collected from urine samples, vaginal and urethral secrets and ejaculates of outpatients with urinary and genital tract infections at IMDL "Chronolab" - Plovdiv, Bulgaria. The most common etiological agent was Escherichia coli (64.8%), followed by Klebsiella spp. (17%) and Proteus mirabilis (10.37%). The antibiotic susceptibility tests showed high resistance against ampicillin (49%), mecillinam (71%), doxycycline (41%) and high susceptibility to cephalosporins (cefuroxime 84.6%; cefoxitin 83.7%; cefotaxime 91.5%; cefepime 87.7%) and fluoroquinolones (ciprofloxacin 85%, norfloxacin 79%, levofloxacin 83%;). Significant resistance was established to nitrofurantoin (24%). Amongst the tested strains, 8.5% produced extended...

Journal of BioScience and Biotechnology, 2018

The current study aimed to examine the amylolytic activities of various species of the Bacillus g... more The current study aimed to examine the amylolytic activities of various species of the Bacillus genus. A total of 31% of the tested 166 strains showed a positive reaction on starch agar. Their amylolytic activity was in the range of 0.9 to 2.8 U/ml. Bacillus cereus №10 showed the highest initial activity, established in the late stationary phase of growth (36 hours of incubation). The effects of different nitrogen sources, metal ions and different type of secondary carbon sources (starch was used as a primary carbon source) on the production of amylase by the screened strain were studied. The enzyme production was significantly influenced by the type and concentration of the secondary carbon source. Replacement of peptone by yeast extract and the addition of 1 mM Ca2+ increased initial amylolytic activity by 153% reaching 4.29±0.63 U/ml.

Ecologia Balkanica, 2018

The aim of this study was to determine the current microbiological status of the microbial commun... more The aim of this study was to determine the current microbiological status of the microbial communities and their ability to form biofilms in two protected by Natura 2000 wetlands in Southern Bulgaria. The numbers of heterotrophic bacteria (TVC22 and TVC 37), actinomycetes, fungi, and sanitary state indicators were determined for dry soil samples and sediments collected form Zlato pole wetland and Tsalapitsa rice paddies. The number of heterotrophic microorganisms (TVC22 and TVC 37) and indicators of sanitary status (FS, FC, and Escherichia coli) in the two rice paddies near the city of Plovdiv is higher in comparison to the control zone Zlato pole – the maximum was recorded in the rice paddy near Tsalapitsa village (C1 and C2 was 12.6х106 cfu.g-1 and 26х106 cfu.g-1, respectively). In the studied samples, the bacterial complex takes a dominant position and it exceeds the number of both fungus and actinomycetes at least 1.5 times. The cluster analysis showed a high similarity between ...

Journal of BioScience and Biotechnology, 2019

Enterococci are increasingly associated with infections of the urogenital tract. The two species ... more Enterococci are increasingly associated with infections of the urogenital tract. The two species Enterococcus faecalis and Enterococcus faecium are the third most commonly isolated pathogens in catheter-associated urinary tract infections (CAUTI). Both species are capable of producing biofilms, with E. faecalis being more frequently isolated. This study explores the antimicrobial resistance and biofilm formation ability of 72 Enterococcus faecalis strains, collected a one-year period from the urogenital tract of outpatients. The results showed that urinary tract infections (UTI), caused by enterococci are more frequent among children up to 10 years of age, while genital tract infections (GTI) are most often observed in women in reproductive age. Antimicrobial resistance was low, with higher levels for UTI compared to GTI strains. The results demonstrate 100% susceptibility to penicillins, which are the most effective agents for the treatment of infections caused by Enterococcus faec...

The study is focused on the etiological structure and drug resistance of bacterial strains causin... more The study is focused on the etiological structure and drug resistance of bacterial strains causing upper respiratory tract infections, which are widely spread amongst children. The aim is to update the data about antimicrobial susceptibility and to establish virulence factors important for infectious process for Staphylococcus spp. isolates from the upper respiratory tract. A total of 711 strains were isolated from outpatients with nasal and oropharyngeal infections at Medical Diagnostic Laboratories "Sinevo-Bulgaria" LTD in Plovdiv for a two-year period 2019-2020. The results demonstrate that the etiological structure is highly related to the site of infection. Branhamella catarrhalis was found to dominate in the samples from the oropharynx (40%), while the majority of isolates from the nasal and ear samples were identified as Staphylococcus aureus - 65% and 35% respectively. S. aureus showed higher drug resistance compared to other isolates, reaching up to 70% to penicil...

The application of phospholipases produced by species of genus Bacillus in different industries r... more The application of phospholipases produced by species of genus Bacillus in different industries reduces the negative impact on the environment by reducing the need of toxic chemicals, consumed energy, and produced carbon emissions. In the current study one hundred sixty-six bacterial strains belonging to the genus Bacillus were tested for phospholipase C production. Eighty-seven percent of the studied strains demonstrated phospholipase C activity on egg-yolk agar. Strain Bacillus thuringiensis was selected as the most promising for the phospholipase production with initial activity of 19.61 U/ml. The nutrient medium composition and cultivating conditions were optimized for achieving higher enzyme yields. The highest phospholipase production was achieved on the following conditions of the liquid medium: 1% of yeast extract as a source of nitrogen; 0.5% NaCl; 0.4% of glucose as a carbon source; NaHCO3 – 3 g/l; Na2HPO4 – 0.4 g/l; 1 mM ZnCl2; pH 7; inoculated with 3% (1.4 x 109 cfu/ml) ...

This study explored the spatial differences and physiological diversity of soil microbial communi... more This study explored the spatial differences and physiological diversity of soil microbial communities in natural wetland and constructed rice paddies in the Maritsa River Basin, protected under the Birds Directive 2009/147/EC as natural habitats. Community level physiological profiling was used to characterize the metabolic function of the communities. The microbial activity expressed, as average well colour development (AWCD) and substrate richness and diversity was higher in the non-flooded soils with no significant spatial differences. Individual carbon source utilization patterns (CSUPs) segregated the paddy fields profiles from the natural wetland sediments and showed that communities` metabolic functions were strongly influenced by rice cropping and not by the sample location. The CUSPs revealed that easily degradable carbohydrates were the most widely used substrates followed by amino acids, carboxylic acids, and polyols. Natural wetland communities held an isolated position ...

Urinary tract infections are serious health and economic burden for society. Selected bacterial s... more Urinary tract infections are serious health and economic burden for society. Selected bacterial species as Escherichia coli, Klebsiella spp., Proteus spp. are often isolated from patience’s urine samples. We investigated twenty strains Escherichia coli, isolated from urine of 14 patients with different urinary infections, 4 patients with asymptomatic bacteriuria and 2 pregnant women. Distribution of virulence determinants as adhesins, motility, hemolysins, serum resistance and biofilm-forming were investigated phenotypically and with multiplex PCR in correlation. We found that strains poses different combinations of virulence capabilities and the structure statistically most often found is the type 1 pili.

One hundred sixty-six bacterial strains belonging to genus Bacillus were tested for protease prod... more One hundred sixty-six bacterial strains belonging to genus Bacillus were tested for protease production. Ninety percent of the studied strains demonstrated protease activity on nutrient gelatin and milk agar. A strain Bacillus thuringiensis was selected as the most promising for enzyme production based on its initial enzyme activity of 9.2 U/ml. The nutrient medium composition and cultivating conditions were optimized aiming better yields. The highest protease activity of 15 U/ml was achieved on the following conditions: inoculation of the medium with 5% inoculum (6.0 McF), followed by 16 hours of cultivation in liquid medium containing 0.5% glucose, 0.55% Bacto Peptone, 50mM phosphate buffer and 0.2% magnesium ions. The produced enzymes were partially purified 5.6 fold by ultrafiltration and size-exclusion chromatography on Sephadex G-75 and had a specific activity of 17.7 U/mg. The approximate molecular weights were determined by SDS-PAGE to be between 45 and 66 kDa.

Pseudomonas strains were examined for the production of lipolytic enzymes. Bacteria synthesize ex... more Pseudomonas strains were examined for the production of lipolytic enzymes. Bacteria synthesize extracellular lipase and phospholipase type-C. The majority of the strains of Pseudomonas sp. are producers of lipase and phospholipase-C. Phospholipase-C activity is maximal in the initial stationary phase – 12 th hour, while the maximum lipase secretion found in the late stationary phase. The production of both enzymes is positively influenced by the addition of extra carbon sources at a concentration of 0.5% for soybean-casein medium that is suitable for cultivation of species Pseudomonas.

Biotechnology & Biotechnological Equipment, 2019

Microbial communities drive the biogeochemical cycles in wetlands and provide a number of ecosyst... more Microbial communities drive the biogeochemical cycles in wetlands and provide a number of ecosystem services. They underpin soil function, and are easily impacted by anthropogenic pressure. This study examined the bacterial microbiome in the natural wetland of Zlato Pole and the protected, periodically flooded rice paddies in the Maritsa River Basin using a metagenomic approach, based on high-throughput sequencing. Alpha-diversity analysis showed a significant variation between the three study sites for Chao1 and ACE (abundance based coverage estimator) richness estimators. A positive correlation was established with pH, with highest values detected for the rice paddies and the lowest, for the Zlato Pole sediments. The obtained sequences were assigned into 37 known bacterial phyla with over 97% bacterial sequences classified within only nine of them. The bacterial communities in rice paddies sediments were more evenly distributed, whereas the Zlato Pole sediment was the most biased. The consortiums in the rice paddies were dominated by Proteobacteria, followed by Actinobacteria and Acidobacteria. The bacterial assemblages in those sites could not be distinguished by analysis of similarity. The Zlato Pole sediment community held an isolated position, where Acidobacteria was replaced by Firmicutes and Bacteroidetes and the microbiome showed an extremely high abundance of Gammaproteobacteria and Bacilli. The dominance of Gammaproteobacteria and the presence of Deinococcus-Thermus phylum, along lower nutrient concentration and the absence of correlation with the environmental parameters, is evidence of constant anthropogenic pressure around the area. The obtained results could be applied in the plans for sustainable management of the protected wetlands.

Biotechnology & Biotechnological Equipment, 2009

Current knowledge on antimicrobial susceptibility pattern of uropathogens is necessary for approp... more Current knowledge on antimicrobial susceptibility pattern of uropathogens is necessary for appropriate therapy. The objective of this study was to investigate antibiotic susceptibility of 28 clinically isolated strains Escherichia coli, associated with different urinary tract infections. Lowest susceptibility detected was for betalactams ampicillin and ampicillin/sulbactam. High susceptibility was detected for aminoglycoside antibiotics. Approximately half of investigated strain showed multidrug resistance profiles. Plasmid content of E. coli isolates was investigated and participation of detected plasmids in drug resistance was discussed. Our data show the high level of antimicrobial resistance and extended spectrum b-lactamases (ESBL) production amongst the uropathogens causing urinary tract infection.

Biotechnology & Biotechnological Equipment, 2010

The aim of the present study was to investigate biofilm-forming capabilities of clinically isolat... more The aim of the present study was to investigate biofilm-forming capabilities of clinically isolated strains Escherichia coli, associated with different urinary tract infections. Biofilm production was detected in 36% of the isolates from UTI. Additionally some of virulence factors are estimated to find correlation between antibiotic resistance, hemolysins, morfotypes and biofilm production. Our data indicate that no combination of VFs was highly associated with biofilm production.

Biotechnology & Biotechnological Equipment, 2011

Materials and Methods Strains, media and cultivation In this study were included three urinary cl... more Materials and Methods Strains, media and cultivation In this study were included three urinary clinically isolated strains with pre-estimated good biofilm growth capacity (11) from the laboratory collection of the Departnemt of Biochemistry and Microbiology, Plovdiv University. PU-1 was isolated from a woman with pyelonephritis, PU-13-from a man with cystitis, and PU-19-from a man with ABU. Estimation of the antibacterial activity of the plant extracts was tested also on reference strains: E. coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 25923 and Streptococcus saprophyticus nctc 7292. The strains were stored frozen in Trypticase soy broth (TSB) (Difco) supplemented with 30% glycerol. Before use, samples were inoculated into TSB and incubated overnight at

Biotechnology & Biotechnological Equipment, 2015

The aim of the present study was to carry out a preliminary assessment for the occurrence of bact... more The aim of the present study was to carry out a preliminary assessment for the occurrence of bacterial strains resistant to frequently used antibiotics in the sediments beneath the sturgeon cage farm in Kardzhali Dam (Bulgaria). Samples were taken from the top 2 cm of sediments under a fish farm and from a control station in the aquatory of the reservoir in the period JulyÀOctober 2011. Surveillance of bacterial susceptibility to 16 antimicrobial agents was performed for 160 Gram-negative strains (Pseudomonas mandelii À 100 strains; Hafnia alvei À 30 strains; and Raoultella ornithinolytica À 30 strains). No significant differences in the resistance to the tested antibiotics were observed between the strains isolated from the two stations (analysis of variance, P > 0.05). Widespread resistance to penicillins and certain cephalosporin antibiotics was observed in both stations. None of the studied strains showed resistance to the aminoglycoside antibiotics gentamicin and amikacin, or to ciprofloxacin. Minimal Inhibitory Concentrations (MIC) were determined for five of the tested antimicrobial agents by the microdilution antibiotic sensitivity assay. The data indicate that amikacin, tetracycline and ciprofloxacin effectively suppress the growth of the tested microorganisms. The isolates from genus Pseudomonas showed the highest MIC and were characterized by the highest percentage of antibiotic resistance.

ILIEV, I., S. KOSTADINOVA, M. MARHOVA, T. HUBENOVA and A. ZAIKOV, 2015. Microbial status of Dospa... more ILIEV, I., S. KOSTADINOVA, M. MARHOVA, T. HUBENOVA and A. ZAIKOV, 2015. Microbial status of Dospat Dam Lake, Bulgaria. Bulg. J. Agric. Sci., Supplement 1, 21: 33–39 The aim of this study was to determine the total count of main microbial indicators for the water quality of Dospat Dam Lake. Samples were taken from six stations situated in the aquatory of the reservoir and one station at Dospatska River. The seasonal dynamics of the total viable count (TVC 20°C), total coliforms (TC), E. coli, fecal streptococci (FS) and C. perfringens were studied for the period April 2011 – March 2012. The values for the TVC 20oC were within range of 1.103cfu.100 mL–1 to 39.103 cfu.100 mL–1, without statistically signifi cant differences between stations (ANOVA, P > 0.05). The average values for TC varied from 10 cfu.100 mL–1 to 100 cfu.100 mL–1 and in August it rose to 1000 cfu.100 mL–1 with higher numbers near the net cage farms (ANOVA, P < 0.005). Presence of E. coli, FS and C. perfringens ...