Lyudmila Boyanova | Medical University of Sofia (original) (raw)

Papers by Lyudmila Boyanova

Journal of Medical Microbiology, Aug 1, 2007

Dokladi na Bʺlgarskata akademiâ na naukite, May 25, 2024

Acta Microbiologica et Immunologica Hungarica, 2018

Helicobacter pylori positivity was assessed among 656 symptomatic children in 2010–2017. Overall ... more Helicobacter pylori positivity was assessed among 656 symptomatic children in 2010–2017. Overall infection prevalence was 24.5% and a significantly higher rate was detected in girls (28.5%) compared to boys (20.0%). Moreover, in children with duodenal ulcer, H. pylori prevalence was higher (47.4%) compared with the rest (23.9%). On the contrary, the infection was detected 1.9-fold less frequently in patients with GERD (14.5%) compared with the other (27.0%) patients and 2.1-fold less often in the presence of duodenogastric reflux (bile) reflux (13.0%) compared with the absence of the reflux (27.0%). No significant difference was observed between the younger (aged ≤7 years, 20.0%) and the older (aged 8–18 years, 25.5%) patients. H. pylori infection rate in Bulgarian pediatric patients between 2010 and 2017 was 2.5-fold lower than that in 1996–2006. In conclusion, H. pylori infection is still an important concern for Bulgarian children, although having decreased by about 1.8%/yearly o...

Microorganisms

Clostridioides difficile is a Gram-positive, spore-forming, anaerobic bacterium. The clinical fea... more Clostridioides difficile is a Gram-positive, spore-forming, anaerobic bacterium. The clinical features of C. difficile infections (CDIs) can vary, ranging from the asymptomatic carriage and mild self-limiting diarrhoea to severe and sometimes fatal pseudomembranous colitis. C. difficile infections (CDIs) are associated with disruption of the gut microbiota caused by antimicrobial agents. The infections are predominantly hospital-acquired, but in the last decades, the CDI patterns have changed. Their prevalence increased, and the proportion of community-acquired CDIs has also increased. This can be associated with the appearance of hypervirulent epidemic isolates of ribotype 027. The COVID-19 pandemic and the associated antibiotic overuse could additionally change the patterns of infections. Treatment of CDIs is a challenge, with only three appropriate antibiotics for use. The wide distribution of C. difficile spores in hospital environments, chronic persistence in some individuals, ...

Microorganisms

The gastrointestinal tract is an important reservoir of high-risk Enterobacteria clones and a dri... more The gastrointestinal tract is an important reservoir of high-risk Enterobacteria clones and a driver of antimicrobial resistance in hospitals. In this study, patients from six hospitals in four major Bulgarian towns were included in this study. Overall, 205 cefotaxime-resistant isolates (35.3%) of Enterobacterales order were detected in fecal samples among 580 patients during the period of 2017–2019. ESBL/carbapenemase/plasmidic AmpC producer rates were 28.8%, 2.4%, and 1.2%, respectively. A wide variety of ESBLs: CTX-M-15 (41%), CTX-M-3 (24%), CTX-M-27 (11%), and CTX-M-14 (4%) was found. The carbapenemases identified in this study were New Delhi metalo-β-lactamase (NDM)-1 (5.4%) and Klebsiella carbapenemase (KPC)-2 (1.5%). Most NDM-1 isolates also produced CTX-M-15/-3 and CMY-4 β-lactamases. They belonged to ST11 Klebsiella pneumoniae clone. The epidemiology typing revealed three main high-risk K. pneumoniae clones (26%)—ST11, ST258, and ST15 and five main Escherichia coli clones—S...

Acta Microbiologica et Immunologica Hungarica

Prevalence of antibiotic resistant Helicobacter pylori was compared between 50 patients living ou... more Prevalence of antibiotic resistant Helicobacter pylori was compared between 50 patients living outside the capital city and 50 matched pairs of capital city residents (CCRs). H. pylori isolates from 2018 to 2022 were included. Resistance rates in CCRs and those living elsewhere were 4.0 and 6.0% to amoxicillin, 48.0 and 42.0% to metronidazole, 30 and 30% to clarithromycin, and 4.0 and 4.0% to tetracycline, respectively. Levofloxacin resistance was higher (38.0%) in the capital city vs 20.0% (P = 0.047) in the country. Odd ratio for levofloxacin resistance between pair-matched groups was 2.45 (95% CI, OR 1.0–6.02, P value = 0.05) and relative risk for fluoroquinolone resistance was 1.90 (95% CI for RR 0.98–3.67) for CCRs vs residents in other regions. Resistance rates to levofloxacin and clarithromycin were worryingly high in our study, most probably due to the high quinolone consumption (2.86 DDD/day in 2017) in Bulgaria and the increase in macrolide, lincosamide and streptogramin c...

Infection and Drug Resistance, 2019

Background: There have been no reports in Bulgaria about quinolone resistance determinants among ... more Background: There have been no reports in Bulgaria about quinolone resistance determinants among Enterobacter spp. Aims: To investigate plasmid and chromosomal quinolone resistance rates among 175 thirdgeneration cephalosporin resistant Enterobacter spp. isolates (167 Enterobacter cloacae complex and eight Enterobacter aerogenes isolates) collected at a university hospital in Varna, Bulgaria, as well as to reveal their association with ESBL/AmpC production and a carriage of specific plasmid replicon types. Methods: PCR, isoelectric focusing, replicon typing, sequencing, and epidemiology typing were carried out. Results: A high level of combined third-generation cephalosporin and quinolone resistant Enterobacter spp. was found − 79.4%. The ESBL production rate was 87%, consisting mainly of CTX-M-15 among E. cloacae complex (in 76%) and CTX-M-3 among E. aerogenes (in 88%). Plasmid mediated quinolone resistance (PMQR) determinants were identified in 57% of the isolates. The most commonly detected PMQR determinants were qnrB (90%), consisting mainly of qnrB1 (in 61%), and qnrB9 (in 27%) of the isolates. Both alleles were transferred with CTX-M-15 genes; transconjugants showed HI2 replicons (for qnrB1 positive transconjugants) and were non-typeable (for qnrB9). One Enterobacter spp. isolate produced qnrB4. QnrA1, qnrS1, and aac(6ʹ)-Ib-cr were detected in single isolates only. QnrC, qnrD, qepA, and oqxAB genes were not found. QnrB was associated with CTX-M-15 production, and qnrS1 was linked to CTX-M-3. Alterations in 83 and 87 positions of gyrB in quinolone-resistance determining regions, and 80 position of parC were detected in high level quinolone resistant isolates. Among all the Enterobacter spp. isolates tested, one predominant clone A was identified (53%). Conclusion: Our data showed the necessity of more prudent use of quinolones and thirdgeneration cephalosporins, because of the risk of promoting dissemination, and selection of multiple resistance determinants (ESBL, PMQR) among Enterobacter spp. isolates in Bulgaria.

Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc, 1995

International Journal of Antimicrobial Agents, 2015

Antibiotics

Antibiotic resistance among Helicobacter pylori strains is the major cause of eradication failure... more Antibiotic resistance among Helicobacter pylori strains is the major cause of eradication failure. Resistance prevalence is dynamic and can greatly vary among countries over the years. We revealed H. pylori resistance trends for five antibiotics in 14 countries through articles predominantly published in 2018–2022, since the latest data can best show the most recent trends in resistance evolution. Amoxicillin resistance generally exhibited no evolution, yet it increased in Bulgaria, Iran, China, and Vietnam. Metronidazole resistance exhibited different trends, including an increase, a decrease and no evolution in six, three, and five studies, respectively. Clarithromycin resistance increased in Australia, Belgium, Bulgaria, Italy, Iran, and Taiwan, but remained stable in France, Spain, Russia, China, Chile, and Colombia. Tetracycline resistance was low and stable except in Iran. Levofloxacin resistance increased in four European and six other countries/regions, without significant i...

Diagnostic Microbiology and Infectious Disease, 2013

The aim of the study was to describe oral Helicobacter pylori strain from a child by 4 methods. T... more The aim of the study was to describe oral Helicobacter pylori strain from a child by 4 methods. The strain was positive by immunofluorescence, ureA- and cagA positive, vacA s1 m2 genotype and resistant to metronidazole and clarithromycin. In conclusion, virulent and antibiotic resistant H. pylori strains can be present in oral cavity from patients with chronic dental and gastroduodenal diseases.

Diagnostic Microbiology and Infectious Disease

Acta Microbiologica et Immunologica Hungarica, 2022

Antibiotic resistance of Helicobacter pylori strains from 106 symptomatic children was evaluated ... more Antibiotic resistance of Helicobacter pylori strains from 106 symptomatic children was evaluated according to EUCAST breakpoints and rate of multidrug resistance (MDR) was analyzed. Overall resistance rates were amoxicillin 7.5%, metronidazole 25.5%, clarithromycin 34.0% and ciprofloxacin 14.1%. There were no significant differences in resistance rates according to patients' age (2–6 and 7–18 years) and sex. Combined resistance rate was 19.8%, including double, triple, and quadruple resistance in 13.2% (14 strains), 5.7% (6) and 0.9% (1) of the strains, respectively. MDR was found in 5.9% (5/84) of the children with gastritis and in two of the four children with celiac disease. The MDR was present in three children aged 4–6 years and in four children aged 10–17 years. The total MDR rate (6.6%) in Bulgarian children in 2012–2021 was higher than those in other studies based on EUCAST breakpoints such as those in pediatric patients in Slovenia in 2011–2014 (3.8%), Lithuania in 2013...

Journal of IMAB - Annual Proceeding (Scientific Papers), 2018

Purpose: The treatment of infections, caused by highly resistant strains of Gram-negative bacteri... more Purpose: The treatment of infections, caused by highly resistant strains of Gram-negative bacteria is extremely difficult. A potentially valuable option is combination antibiotic therapy. The aim of this study was to evaluate three different in vitro methods for synergy testing and to assess the effect of different combinations with colistin against carbapenem-resistant K. pneumoniae strains. Matherial/methods: A screening test for synergy with colistin (developed in the laboratory) and the microdilution method of El-Azizi were used on 50 carbapenem-resistant strains of K. pneumoniae. Additionally, time-kill assays (TKA) were performed for one antibiotic combination. Results: A total of 16 combinations were tested with the screening test. Synergy and probable synergy with colistin were observed mainly with azithromycin (18% of the isolates), rifampicin (16%), meropenem (14%) and doxycycline (12.8%). The combinations colistin-rifampicin, colistin-meropenem and colistin-gentamicin, were synergistic in 36%, 8% and 20%, respectively, according to the microdilution method of El-Azizi. The observed synergy was detected mainly against some of the colistin resistant strains. Agreement between the two methods was found in 80% for the combinations colistin-rifampicin and colistin-meropenem and in 84% for colistin-gentamicin. Agreement between the three methods used was observed for four strains (80%). Conclusions: The screening test may represent a rapid and cost effective screening of a large number of combinations with colistin. The microdilution method of El-Azizi may provide an opportunity for rapid testing of three double and one triple antibiotic combinations in one plate. There is an urgent need for standardization of the methods for synergy testing and guidelines for diagnostic laboratories.

Anaerobe, 2016

Finegoldia magna is a highly successful opportunistic pathogen. • Factors like sortase-dependent ... more Finegoldia magna is a highly successful opportunistic pathogen. • Factors like sortase-dependent pili and FAF act at the start of the infection. • Infection severity can be linked to superantigen protein L, capsule and enzyme. • FAF, SufA and biofilms can lead to infection chronification. • Antibiotic therapy can be hampered by biofilms and antibiotic resistance.

Gastroenterology, 2016

Conclusion: CD133 expression may represent a biomarker for early detection of gastric cancer.

Diagnostic Microbiology and Infectious Disease, 2009

The aim of the study was to evaluate the prevalence of main virulence genes in Helicobacter pylor... more The aim of the study was to evaluate the prevalence of main virulence genes in Helicobacter pylori strains from 116 patients with peptic ulcers (41 cases) and nonulcer diseases (75) by polymerase chain reaction (PCR) with pure cultures and to compare the results with those by multiplex PCR in 39 H. pylori-positive gastric biopsies in another center in Sofia, Bulgaria. Strain susceptibility to amoxicillin, metronidazole, and clarithromycin was determined by agar dilution method. By PCR with pure cultures, coinfections with multiple H. pylori strains were found in 8 (6.9%) patients who were excluded from the statistical analysis. Prevalence of toxigenic type vacA s1 was higher (91.7%) than that usually reported in Europe. cagA-positive genotype was detected in most (81.5%) strains, and almost all of them harbored vacA s1 genotype. Strains with cagA+/vacA s1a genotype were more common (80.6%) than the other genotypes (19.4%, P = 0.0001). The ulcer patients had more often virulent strains than the other patients (92.3% versus 75.4% for cagA+, 100.0% versus 87.0% for vacA s1, 100% versus 84.0% for vacA s1a, and 92.3% versus 73.9% for cagA+/vacA s1a, respectively). The prevalence of H. pylori virulenceassociated genes was not associated with patients' sex and age or with the antibacterial resistance of strains. The most common H. pylori genotype was cagA+/vacA s1a. Similar prevalence of cagA-positive (82.1%), vacA s1 (97.4%), and cagA+/vacA s1 strains (79.5%) was found by multiplex PCR in gastric biopsies in the 2nd center. In conclusion, H. pylori strains with virulent genotypes are widespread in symptomatic Bulgarian patients.

Journal of Medical Microbiology, 2005

Propolis exhibits antimicrobial, anti-inflammatory and other biological effects. The aim of this ... more Propolis exhibits antimicrobial, anti-inflammatory and other biological effects. The aim of this study was to evaluate the activity of 30 % ethanolic extract of Bulgarian propolis against 94 Helicobacter pylori strains by three methods. By the agar-well diffusion method, only 13.8 % of the strains exhibited no inhibition by 30 μl propolis extract (containing 9 mg propolis) and all isolates were inhibited to some extent by 90 μl of the extract (27 mg propolis) per well. The mean diameters of growth inhibition by 30, 60 or 90 μl propolis extract or 30 μl 96 % ethanol per well were 16.8, 19.2, 27.5 and 8.3 mm, respectively. The propolis extract was more active than the ethanol (P < 0.001). With 90 μl propolis extract per well, 69.4 % of the strains exhibited large diameters of growth inhibition (⩾20 mm) versus 26.6 % with 30 μl per well (P < 0.001). With moist propolis discs, inhibition was detected in more strains (92.1 %) than with dried discs (78.2 %, P < 0.05), with mean i...

Journal of Medical Microbiology, Aug 1, 2007

Dokladi na Bʺlgarskata akademiâ na naukite, May 25, 2024

Acta Microbiologica et Immunologica Hungarica, 2018

Helicobacter pylori positivity was assessed among 656 symptomatic children in 2010–2017. Overall ... more Helicobacter pylori positivity was assessed among 656 symptomatic children in 2010–2017. Overall infection prevalence was 24.5% and a significantly higher rate was detected in girls (28.5%) compared to boys (20.0%). Moreover, in children with duodenal ulcer, H. pylori prevalence was higher (47.4%) compared with the rest (23.9%). On the contrary, the infection was detected 1.9-fold less frequently in patients with GERD (14.5%) compared with the other (27.0%) patients and 2.1-fold less often in the presence of duodenogastric reflux (bile) reflux (13.0%) compared with the absence of the reflux (27.0%). No significant difference was observed between the younger (aged ≤7 years, 20.0%) and the older (aged 8–18 years, 25.5%) patients. H. pylori infection rate in Bulgarian pediatric patients between 2010 and 2017 was 2.5-fold lower than that in 1996–2006. In conclusion, H. pylori infection is still an important concern for Bulgarian children, although having decreased by about 1.8%/yearly o...

Microorganisms

Clostridioides difficile is a Gram-positive, spore-forming, anaerobic bacterium. The clinical fea... more Clostridioides difficile is a Gram-positive, spore-forming, anaerobic bacterium. The clinical features of C. difficile infections (CDIs) can vary, ranging from the asymptomatic carriage and mild self-limiting diarrhoea to severe and sometimes fatal pseudomembranous colitis. C. difficile infections (CDIs) are associated with disruption of the gut microbiota caused by antimicrobial agents. The infections are predominantly hospital-acquired, but in the last decades, the CDI patterns have changed. Their prevalence increased, and the proportion of community-acquired CDIs has also increased. This can be associated with the appearance of hypervirulent epidemic isolates of ribotype 027. The COVID-19 pandemic and the associated antibiotic overuse could additionally change the patterns of infections. Treatment of CDIs is a challenge, with only three appropriate antibiotics for use. The wide distribution of C. difficile spores in hospital environments, chronic persistence in some individuals, ...

Microorganisms

The gastrointestinal tract is an important reservoir of high-risk Enterobacteria clones and a dri... more The gastrointestinal tract is an important reservoir of high-risk Enterobacteria clones and a driver of antimicrobial resistance in hospitals. In this study, patients from six hospitals in four major Bulgarian towns were included in this study. Overall, 205 cefotaxime-resistant isolates (35.3%) of Enterobacterales order were detected in fecal samples among 580 patients during the period of 2017–2019. ESBL/carbapenemase/plasmidic AmpC producer rates were 28.8%, 2.4%, and 1.2%, respectively. A wide variety of ESBLs: CTX-M-15 (41%), CTX-M-3 (24%), CTX-M-27 (11%), and CTX-M-14 (4%) was found. The carbapenemases identified in this study were New Delhi metalo-β-lactamase (NDM)-1 (5.4%) and Klebsiella carbapenemase (KPC)-2 (1.5%). Most NDM-1 isolates also produced CTX-M-15/-3 and CMY-4 β-lactamases. They belonged to ST11 Klebsiella pneumoniae clone. The epidemiology typing revealed three main high-risk K. pneumoniae clones (26%)—ST11, ST258, and ST15 and five main Escherichia coli clones—S...

Acta Microbiologica et Immunologica Hungarica

Prevalence of antibiotic resistant Helicobacter pylori was compared between 50 patients living ou... more Prevalence of antibiotic resistant Helicobacter pylori was compared between 50 patients living outside the capital city and 50 matched pairs of capital city residents (CCRs). H. pylori isolates from 2018 to 2022 were included. Resistance rates in CCRs and those living elsewhere were 4.0 and 6.0% to amoxicillin, 48.0 and 42.0% to metronidazole, 30 and 30% to clarithromycin, and 4.0 and 4.0% to tetracycline, respectively. Levofloxacin resistance was higher (38.0%) in the capital city vs 20.0% (P = 0.047) in the country. Odd ratio for levofloxacin resistance between pair-matched groups was 2.45 (95% CI, OR 1.0–6.02, P value = 0.05) and relative risk for fluoroquinolone resistance was 1.90 (95% CI for RR 0.98–3.67) for CCRs vs residents in other regions. Resistance rates to levofloxacin and clarithromycin were worryingly high in our study, most probably due to the high quinolone consumption (2.86 DDD/day in 2017) in Bulgaria and the increase in macrolide, lincosamide and streptogramin c...

Infection and Drug Resistance, 2019

Background: There have been no reports in Bulgaria about quinolone resistance determinants among ... more Background: There have been no reports in Bulgaria about quinolone resistance determinants among Enterobacter spp. Aims: To investigate plasmid and chromosomal quinolone resistance rates among 175 thirdgeneration cephalosporin resistant Enterobacter spp. isolates (167 Enterobacter cloacae complex and eight Enterobacter aerogenes isolates) collected at a university hospital in Varna, Bulgaria, as well as to reveal their association with ESBL/AmpC production and a carriage of specific plasmid replicon types. Methods: PCR, isoelectric focusing, replicon typing, sequencing, and epidemiology typing were carried out. Results: A high level of combined third-generation cephalosporin and quinolone resistant Enterobacter spp. was found − 79.4%. The ESBL production rate was 87%, consisting mainly of CTX-M-15 among E. cloacae complex (in 76%) and CTX-M-3 among E. aerogenes (in 88%). Plasmid mediated quinolone resistance (PMQR) determinants were identified in 57% of the isolates. The most commonly detected PMQR determinants were qnrB (90%), consisting mainly of qnrB1 (in 61%), and qnrB9 (in 27%) of the isolates. Both alleles were transferred with CTX-M-15 genes; transconjugants showed HI2 replicons (for qnrB1 positive transconjugants) and were non-typeable (for qnrB9). One Enterobacter spp. isolate produced qnrB4. QnrA1, qnrS1, and aac(6ʹ)-Ib-cr were detected in single isolates only. QnrC, qnrD, qepA, and oqxAB genes were not found. QnrB was associated with CTX-M-15 production, and qnrS1 was linked to CTX-M-3. Alterations in 83 and 87 positions of gyrB in quinolone-resistance determining regions, and 80 position of parC were detected in high level quinolone resistant isolates. Among all the Enterobacter spp. isolates tested, one predominant clone A was identified (53%). Conclusion: Our data showed the necessity of more prudent use of quinolones and thirdgeneration cephalosporins, because of the risk of promoting dissemination, and selection of multiple resistance determinants (ESBL, PMQR) among Enterobacter spp. isolates in Bulgaria.

Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc, 1995

International Journal of Antimicrobial Agents, 2015

Antibiotics

Antibiotic resistance among Helicobacter pylori strains is the major cause of eradication failure... more Antibiotic resistance among Helicobacter pylori strains is the major cause of eradication failure. Resistance prevalence is dynamic and can greatly vary among countries over the years. We revealed H. pylori resistance trends for five antibiotics in 14 countries through articles predominantly published in 2018–2022, since the latest data can best show the most recent trends in resistance evolution. Amoxicillin resistance generally exhibited no evolution, yet it increased in Bulgaria, Iran, China, and Vietnam. Metronidazole resistance exhibited different trends, including an increase, a decrease and no evolution in six, three, and five studies, respectively. Clarithromycin resistance increased in Australia, Belgium, Bulgaria, Italy, Iran, and Taiwan, but remained stable in France, Spain, Russia, China, Chile, and Colombia. Tetracycline resistance was low and stable except in Iran. Levofloxacin resistance increased in four European and six other countries/regions, without significant i...

Diagnostic Microbiology and Infectious Disease, 2013

The aim of the study was to describe oral Helicobacter pylori strain from a child by 4 methods. T... more The aim of the study was to describe oral Helicobacter pylori strain from a child by 4 methods. The strain was positive by immunofluorescence, ureA- and cagA positive, vacA s1 m2 genotype and resistant to metronidazole and clarithromycin. In conclusion, virulent and antibiotic resistant H. pylori strains can be present in oral cavity from patients with chronic dental and gastroduodenal diseases.

Diagnostic Microbiology and Infectious Disease

Acta Microbiologica et Immunologica Hungarica, 2022

Antibiotic resistance of Helicobacter pylori strains from 106 symptomatic children was evaluated ... more Antibiotic resistance of Helicobacter pylori strains from 106 symptomatic children was evaluated according to EUCAST breakpoints and rate of multidrug resistance (MDR) was analyzed. Overall resistance rates were amoxicillin 7.5%, metronidazole 25.5%, clarithromycin 34.0% and ciprofloxacin 14.1%. There were no significant differences in resistance rates according to patients' age (2–6 and 7–18 years) and sex. Combined resistance rate was 19.8%, including double, triple, and quadruple resistance in 13.2% (14 strains), 5.7% (6) and 0.9% (1) of the strains, respectively. MDR was found in 5.9% (5/84) of the children with gastritis and in two of the four children with celiac disease. The MDR was present in three children aged 4–6 years and in four children aged 10–17 years. The total MDR rate (6.6%) in Bulgarian children in 2012–2021 was higher than those in other studies based on EUCAST breakpoints such as those in pediatric patients in Slovenia in 2011–2014 (3.8%), Lithuania in 2013...

Journal of IMAB - Annual Proceeding (Scientific Papers), 2018

Purpose: The treatment of infections, caused by highly resistant strains of Gram-negative bacteri... more Purpose: The treatment of infections, caused by highly resistant strains of Gram-negative bacteria is extremely difficult. A potentially valuable option is combination antibiotic therapy. The aim of this study was to evaluate three different in vitro methods for synergy testing and to assess the effect of different combinations with colistin against carbapenem-resistant K. pneumoniae strains. Matherial/methods: A screening test for synergy with colistin (developed in the laboratory) and the microdilution method of El-Azizi were used on 50 carbapenem-resistant strains of K. pneumoniae. Additionally, time-kill assays (TKA) were performed for one antibiotic combination. Results: A total of 16 combinations were tested with the screening test. Synergy and probable synergy with colistin were observed mainly with azithromycin (18% of the isolates), rifampicin (16%), meropenem (14%) and doxycycline (12.8%). The combinations colistin-rifampicin, colistin-meropenem and colistin-gentamicin, were synergistic in 36%, 8% and 20%, respectively, according to the microdilution method of El-Azizi. The observed synergy was detected mainly against some of the colistin resistant strains. Agreement between the two methods was found in 80% for the combinations colistin-rifampicin and colistin-meropenem and in 84% for colistin-gentamicin. Agreement between the three methods used was observed for four strains (80%). Conclusions: The screening test may represent a rapid and cost effective screening of a large number of combinations with colistin. The microdilution method of El-Azizi may provide an opportunity for rapid testing of three double and one triple antibiotic combinations in one plate. There is an urgent need for standardization of the methods for synergy testing and guidelines for diagnostic laboratories.

Anaerobe, 2016

Finegoldia magna is a highly successful opportunistic pathogen. • Factors like sortase-dependent ... more Finegoldia magna is a highly successful opportunistic pathogen. • Factors like sortase-dependent pili and FAF act at the start of the infection. • Infection severity can be linked to superantigen protein L, capsule and enzyme. • FAF, SufA and biofilms can lead to infection chronification. • Antibiotic therapy can be hampered by biofilms and antibiotic resistance.

Gastroenterology, 2016

Conclusion: CD133 expression may represent a biomarker for early detection of gastric cancer.

Diagnostic Microbiology and Infectious Disease, 2009

The aim of the study was to evaluate the prevalence of main virulence genes in Helicobacter pylor... more The aim of the study was to evaluate the prevalence of main virulence genes in Helicobacter pylori strains from 116 patients with peptic ulcers (41 cases) and nonulcer diseases (75) by polymerase chain reaction (PCR) with pure cultures and to compare the results with those by multiplex PCR in 39 H. pylori-positive gastric biopsies in another center in Sofia, Bulgaria. Strain susceptibility to amoxicillin, metronidazole, and clarithromycin was determined by agar dilution method. By PCR with pure cultures, coinfections with multiple H. pylori strains were found in 8 (6.9%) patients who were excluded from the statistical analysis. Prevalence of toxigenic type vacA s1 was higher (91.7%) than that usually reported in Europe. cagA-positive genotype was detected in most (81.5%) strains, and almost all of them harbored vacA s1 genotype. Strains with cagA+/vacA s1a genotype were more common (80.6%) than the other genotypes (19.4%, P = 0.0001). The ulcer patients had more often virulent strains than the other patients (92.3% versus 75.4% for cagA+, 100.0% versus 87.0% for vacA s1, 100% versus 84.0% for vacA s1a, and 92.3% versus 73.9% for cagA+/vacA s1a, respectively). The prevalence of H. pylori virulenceassociated genes was not associated with patients' sex and age or with the antibacterial resistance of strains. The most common H. pylori genotype was cagA+/vacA s1a. Similar prevalence of cagA-positive (82.1%), vacA s1 (97.4%), and cagA+/vacA s1 strains (79.5%) was found by multiplex PCR in gastric biopsies in the 2nd center. In conclusion, H. pylori strains with virulent genotypes are widespread in symptomatic Bulgarian patients.

Journal of Medical Microbiology, 2005

Propolis exhibits antimicrobial, anti-inflammatory and other biological effects. The aim of this ... more Propolis exhibits antimicrobial, anti-inflammatory and other biological effects. The aim of this study was to evaluate the activity of 30 % ethanolic extract of Bulgarian propolis against 94 Helicobacter pylori strains by three methods. By the agar-well diffusion method, only 13.8 % of the strains exhibited no inhibition by 30 μl propolis extract (containing 9 mg propolis) and all isolates were inhibited to some extent by 90 μl of the extract (27 mg propolis) per well. The mean diameters of growth inhibition by 30, 60 or 90 μl propolis extract or 30 μl 96 % ethanol per well were 16.8, 19.2, 27.5 and 8.3 mm, respectively. The propolis extract was more active than the ethanol (P < 0.001). With 90 μl propolis extract per well, 69.4 % of the strains exhibited large diameters of growth inhibition (⩾20 mm) versus 26.6 % with 30 μl per well (P < 0.001). With moist propolis discs, inhibition was detected in more strains (92.1 %) than with dried discs (78.2 %, P < 0.05), with mean i...