Sashka Mihaylova - Academia.edu (original) (raw)

Papers by Sashka Mihaylova

Objectives: The identification of clinical isolates of Stenotrophomonas spp. to the species level... more Objectives: The identification of clinical isolates of Stenotrophomonas spp. to the species level, using a polyphasic approach of phenotypic and genotypic methods, and the determination and comparison of the in vitro responses to various classes of antimicrobial agents by these isolates. Previous studies have suggested a marked diversity among clinical, as well as environmental, isolates of Stenotrophomonas spp. and they represent a significant threat within hospital settings, particularly for patients in ICUs and other immunocompromised conditions. Isolates characterised as putative Stenotrophomonas spp. from Pleven University Hospital were analysed in detail. The predominant source of the isolates was respiratory tract and two thirds of patients were admitted to ICUs. Isolates were examined, using the VITEK 2 compact system, CCUG phenotypic characterisation panels and sequencing and analyses of the genes for 16S rRNA and gyrB. The in vitro responses of isolates to 10 antibiotics (...

FEMS Microbiology Letters, 2011

Stenotrophomonas species are found commonly in environmental and clinical samples; Stenotrophomon... more Stenotrophomonas species are found commonly in environmental and clinical samples; Stenotrophomonas maltophilia is an important opportunistic pathogen of humans. Traditional phenotyping protocols, as well as genotyping by 16S rRNA gene sequence analysis, do not reliably distinguish the species of Stenotrophomonas. Sequence analyses of two targeted PCR-amplified regions of the gyrB gene, which encodes the b-subunit of DNA gyrase, enabled resolution and identification of these species. Most type strains of the different species of Stenotrophomonas exhibited more than 7% dissimilarity in the gyrB gene sequences. Among these, strains identified as the same species exhibited sequence dissimilarities up to 4.6% and 5.9% for the two regions, respectively. Strains identified as S. maltophilia, with 16S rRNA gene sequence similarities > 99.0%, were grouped within a 'S. maltophilia complex'; these organisms exhibited gyrB similarities as low as 93%. Many of these strains possessed genomic DNA similarities with the type strain of S. maltophilia CCUG 5866 T below 70%. These data, including gyrB sequence comparisons, indicate that strains identified as S. maltophilia may comprise distinct, new species.

European Journal of Public Health, 2018

prevalence in non-meat foods was null (CI95% 0%-3.9%) and was 2.4% (CI95% 0.1%-12.9%) in pork mea... more prevalence in non-meat foods was null (CI95% 0%-3.9%) and was 2.4% (CI95% 0.1%-12.9%) in pork meat products. Conclusions: HEV is rarely detected in non-meat products collected in Italy, while higher virus prevalence can be predicted for pork-based food products. Further studies are needed to improve precision of the prevalence values estimated for the different food categories. Key messages: Hepatitis E virus is an emerging problem in developed countries, where transmission is mainly associated to consumption of raw or undercooked pork or game meat. Data collection studies are required to fill the information gaps in risk assessment of foodborne transmission of HEV.

Stenotrophomonas maltophilia uppvisar stor art-variation. Vi har jamfort gen-sekvenser av 16S rRN... more Stenotrophomonas maltophilia uppvisar stor art-variation. Vi har jamfort gen-sekvenser av 16S rRNA, gyrB och rpoD samt antibiotika resistens monster och data fran kliniska isolat. S. maltophilia isolat kunde delas in i fyra grupper (genotypiskt) och korrelleras till skillnader i antibiotika-resistens.

International Journal of Pathogen Research

The present study aims to investigate the microbiological research of mineral and spring mountain... more The present study aims to investigate the microbiological research of mineral and spring mountain waters in the region of Plovdiv, Bulgaria. In Bulgaria, there are mineral and mountain spring waters, which are not subjected to physicochemical and microbiological control by the Regional Health Inspectorate, yet they are the most widely used springs by the population as sources of drinking water. The methodology is including the determination of total number of mesophilic aerobic and facultative anaerobic bacteria. The results showed 11 rod shaped, Gram–positive and spore forming bacteria and 2 rod shaped, Gram–negative non-spore forming bacteria are isolated from spring and healing waters. The colonial and physiological characteristics of the isolated strains are defined. The biochemical profiles of the selected bacteria are determined with the system for rapid identification API 50 CH. The strains are identified by software processing of the obtained biochemical profiles with apiweb...

Journal of the Turkish Academy of Dermatology

Twenty-one children who had at least one positive blood culture for B. cepacia between January 19... more Twenty-one children who had at least one positive blood culture for B. cepacia between January 1999 and December 2000 were studied retrospectively. Fifty-eight blood cultures and 52 cultures of hospital environment and medical staff were performed. Traditional methods (biotyping and antibiotic susceptibility profile) were used for epidemiological typing of B. cepacia. Hansen’s criteria for bacteremia were applied. From January 1999 to December 2000 there were 21 episodes of B. cepacia bacteremia distributed in four outbreaks. Bacteremia was monomicrobial in 16 episodes and polymicrobial in 5. Eleven episodes of bacteremia were certain and 10 were probable. Sixteen bacteremias were nosocomial and 5 were community-acquired. B. cepacia was found in three opened bottles with intravenous fluids. All B. cepacia isolates (clinical and environmental) belonged to the same biotype and had identical antibiotic susceptibility profile. All children with B. cepacia bacteremia were with indwelling...

Оne hundred and sixty-two patients were studied retrospectively. They were chosen on the basis of... more Оne hundred and sixty-two patients were studied retrospectively. They were chosen on the basis of the following criteria: isolation of B. cepacia from one or more clinical specimens from 1.1.1996 to 31.12.2002, data for hospital acquisition of the bacterium, and admission in intensive care unit. Five hundred and forty-seven cultures of hospital environment were performed in order to find the source of B. cepacia. A total of 411 strains of B. cepacia were isolated between January 1996 and December 2002. Three hundred and ninety of them were from clinical specimens, among which blood cultures predominated. Twenty-one strains of B. cepacia were found in environmental specimens. During the examined 7 years there are three periods without B. cepacia outbreaks. At this time the bacterium probably survives in the hospital environment or colonizes undetected carriers. The most important risk factors for nosocomial acquisition of B. cepacia were invasive procedures (insertion of central veno...

The growth on Burkholderia cepacia selective agar (BCSA) of B. cepacia and other gram-negative an... more The growth on Burkholderia cepacia selective agar (BCSA) of B. cepacia and other gram-negative and gram-positive organisms was evaluated. A total of 265 strains were included in the study: 136 B. cepacia, 88 other gram-negative bacteria, and 41 gram-positive bacteria. The testing of BCSA was conducted in two phases. In phase 1 polymyxin and gentamicin were included in BCSA base. In phase 2 vancomycin was added to this formulation. Plates with Mueller-Hinton agar, BCSA base, BCSA phase 1, and BCSA phase 2 were inoculated with standardized bacterial suspensions and were incubated at 320C up to 72 h. Two hundred and forty-six (92.8%) of tested 265 strains grew on BCSA base. For 19 Staphylococcus spp. this base had inhibitory effect. All B. cepacia isolates, 7 of 25 S. maltophilia, and 8 of 17 Enterococcus spp. grew on BCSA phase 1. None of the tested organisms of family Enterobacteriaceae, Pseudomonas spp., A. baumannii, and Staphylococcus spp. showed growth on BCSA with polymyxin and ...

Phenotypic characterization of bacteria of the Burkholderia cepacia complex was done and their ge... more Phenotypic characterization of bacteria of the Burkholderia cepacia complex was done and their genomovar status was determined. A total of 135 strains were examined with 30 biochemical tests. All tested isolates had identical phenotypic characteristics. Positive results for sucrose and adonitol oxidation allowed their assignation to a group, including genomovars I, III and VII. Production of ornithine decarboxylase and yellow pigment enabled to exclude genomovar VII. Thus, the genomovar identification was reduced to a group of genomovars I and III. Performed phenotypic tests gave opportunity to distinguish definitively the Burkholderia cepacia complex from Burkholderia cepacia-like organisms. These tests allowed separation the Burkholderia cepacia complex at least in four groups and also gave higher degree of differentiation in genomovar group I, III, and VII.

Immunization with modern vaccines is the safest and the most efficacious way of preventing a numb... more Immunization with modern vaccines is the safest and the most efficacious way of preventing a number of infections. The purpose of the present study is to assess parents’ knowledge of the infectious diseases for which vaccine prophylaxis is performed according to the Immunization schedule of the country. A direct individual inquiry is conducted among 400 parents. Their knowledge is evaluated according to a 5-point scale. The highest levels of knowledge are ascertained for clinical manifestations and epidemiology of tuberculosis, and the lowest levels of knowledge are demonstrated for clinical presentations of diphtheria and epidemiology of poliomyelitis. One third of parents are with very good and excellent overall knowledge regarding the infections for which vaccine prophylaxis is performed according to the Immunization schedule. It is necessary to direct the future efforts toward increasing knowledge of all vaccine-preventable diseases by organizing programs for health education of...

Susceptibility of strains of the B. cepacia complex to 23 antimicrobial agents was examined in th... more Susceptibility of strains of the B. cepacia complex to 23 antimicrobial agents was examined in the present study, in order to optimise the choice of drugs for managing the infections caused by these bacteria. One hundred and forty-nine isolates were tested, using the agar dilution method. On the basis of respective MIC all strains were defined as being susceptible to AZL, PIP, CAZ and MER and resistant to AMP/SAM, GEN, TOB and POL B. More than 90% of examined isolates were determined to be susceptible to CFP, FTX, CRO, FEP, IPM, TMP, TMP/SMX, NAL and CIP. The highest activity evaluated by MIC90 demonstrated MER, CAZ, PIP and AZL which makes them agents of choice for therapy of B. cepacia complex infections. The finding that almost all strains were susceptible to β-lactams, TMP/SMX and clinically relevant fluoroquinolones is an unusual observation in that bacterial group.

General Medicine

Poliomyelitis is an acute infectious vaccine-preventable disease with virus aetiology. Children u... more Poliomyelitis is an acute infectious vaccine-preventable disease with virus aetiology. Children up to 5 years suffer most frequently. Poliomyelitis is both medical and social problem as the disease leads to disability in one of 200 infected children and the lethality can reach 10%. Effective vaccines introduced in the middle of the twentieth century changed the epidemiology of infection worldwide. The study aim was to analyze the incidence of poliomyelitis in Bulgaria during the years prior and after introduction of immunization. A documentary method was used and analysis of epidemiological information was performed. Pre-immunization period was characterized by a tendency of increasing the number of infected people. Cases with lethal outcome were registered. The average incidence 0.7 per 100 000 population was recorded till the year of 1935. Over the next two decades the lowest incidence (0.1 per 100 000) was recorded in 1950 and the highest incidence (13.9 per 100 000) in 1957. In ...

World Applied Sciences Journal

The objective of the present study was to evaluate thein vitroactivities of antimicrobial agents ... more The objective of the present study was to evaluate thein vitroactivities of antimicrobial agents againstRhizobium radiobacterstrains, in order to identify the most effective antibiotics for the elimination and control of this bacterium from different biological systems. Carbenicillin, imipenem, meropenem, gentamicin, amikacin, polymyxin B, ciprofloxacin and levofloxacin were determined to be applicable for transformation of the plants with these bacteria. Carbenicillin, carbapenems and fluoroquinolones would be suggested for treatment of human infections.

General Medicine

The purpose of the present study is to ascertain Bulgarian parents’ attitudes towards vaccination... more The purpose of the present study is to ascertain Bulgarian parents’ attitudes towards vaccinations according to the Immunization schedule of Republic of Bulgaria and to investigate the correlation with parents’ knowledge of vaccine-preventable diseases. The study included 632 persons from Pleven region. A structured questionnaire was used. The percentage of parents considering that vaccines must be applied was 90.8%; 40 parents (6.3%) didn’t have opinion on the problem; and 18 parents (2.9%) were against the vaccines. The parents with positive attitudes towards vaccines always demonstrated higher percentage of correct answers to the questions about vaccine-preventable diseases in comparison to parents with negative and indefinite attitudes. A statistically significant difference was found by gender in parents’ attitudes towards vaccines (р < 0.05). There were no differences in other demographic characteristics. The presented results give grounds to make the following conclusions:...

Objectives: The identification of clinical isolates of Stenotrophomonas spp. to the species level... more Objectives: The identification of clinical isolates of Stenotrophomonas spp. to the species level, using a polyphasic approach of phenotypic and genotypic methods, and the determination and comparison of the in vitro responses to various classes of antimicrobial agents by these isolates. Previous studies have suggested a marked diversity among clinical, as well as environmental, isolates of Stenotrophomonas spp. and they represent a significant threat within hospital settings, particularly for patients in ICUs and other immunocompromised conditions. Isolates characterised as putative Stenotrophomonas spp. from Pleven University Hospital were analysed in detail. The predominant source of the isolates was respiratory tract and two thirds of patients were admitted to ICUs. Isolates were examined, using the VITEK 2 compact system, CCUG phenotypic characterisation panels and sequencing and analyses of the genes for 16S rRNA and gyrB. The in vitro responses of isolates to 10 antibiotics (...

FEMS Microbiology Letters, 2011

Stenotrophomonas species are found commonly in environmental and clinical samples; Stenotrophomon... more Stenotrophomonas species are found commonly in environmental and clinical samples; Stenotrophomonas maltophilia is an important opportunistic pathogen of humans. Traditional phenotyping protocols, as well as genotyping by 16S rRNA gene sequence analysis, do not reliably distinguish the species of Stenotrophomonas. Sequence analyses of two targeted PCR-amplified regions of the gyrB gene, which encodes the b-subunit of DNA gyrase, enabled resolution and identification of these species. Most type strains of the different species of Stenotrophomonas exhibited more than 7% dissimilarity in the gyrB gene sequences. Among these, strains identified as the same species exhibited sequence dissimilarities up to 4.6% and 5.9% for the two regions, respectively. Strains identified as S. maltophilia, with 16S rRNA gene sequence similarities > 99.0%, were grouped within a 'S. maltophilia complex'; these organisms exhibited gyrB similarities as low as 93%. Many of these strains possessed genomic DNA similarities with the type strain of S. maltophilia CCUG 5866 T below 70%. These data, including gyrB sequence comparisons, indicate that strains identified as S. maltophilia may comprise distinct, new species.

European Journal of Public Health, 2018

prevalence in non-meat foods was null (CI95% 0%-3.9%) and was 2.4% (CI95% 0.1%-12.9%) in pork mea... more prevalence in non-meat foods was null (CI95% 0%-3.9%) and was 2.4% (CI95% 0.1%-12.9%) in pork meat products. Conclusions: HEV is rarely detected in non-meat products collected in Italy, while higher virus prevalence can be predicted for pork-based food products. Further studies are needed to improve precision of the prevalence values estimated for the different food categories. Key messages: Hepatitis E virus is an emerging problem in developed countries, where transmission is mainly associated to consumption of raw or undercooked pork or game meat. Data collection studies are required to fill the information gaps in risk assessment of foodborne transmission of HEV.

Stenotrophomonas maltophilia uppvisar stor art-variation. Vi har jamfort gen-sekvenser av 16S rRN... more Stenotrophomonas maltophilia uppvisar stor art-variation. Vi har jamfort gen-sekvenser av 16S rRNA, gyrB och rpoD samt antibiotika resistens monster och data fran kliniska isolat. S. maltophilia isolat kunde delas in i fyra grupper (genotypiskt) och korrelleras till skillnader i antibiotika-resistens.

International Journal of Pathogen Research

The present study aims to investigate the microbiological research of mineral and spring mountain... more The present study aims to investigate the microbiological research of mineral and spring mountain waters in the region of Plovdiv, Bulgaria. In Bulgaria, there are mineral and mountain spring waters, which are not subjected to physicochemical and microbiological control by the Regional Health Inspectorate, yet they are the most widely used springs by the population as sources of drinking water. The methodology is including the determination of total number of mesophilic aerobic and facultative anaerobic bacteria. The results showed 11 rod shaped, Gram–positive and spore forming bacteria and 2 rod shaped, Gram–negative non-spore forming bacteria are isolated from spring and healing waters. The colonial and physiological characteristics of the isolated strains are defined. The biochemical profiles of the selected bacteria are determined with the system for rapid identification API 50 CH. The strains are identified by software processing of the obtained biochemical profiles with apiweb...

Journal of the Turkish Academy of Dermatology

Twenty-one children who had at least one positive blood culture for B. cepacia between January 19... more Twenty-one children who had at least one positive blood culture for B. cepacia between January 1999 and December 2000 were studied retrospectively. Fifty-eight blood cultures and 52 cultures of hospital environment and medical staff were performed. Traditional methods (biotyping and antibiotic susceptibility profile) were used for epidemiological typing of B. cepacia. Hansen’s criteria for bacteremia were applied. From January 1999 to December 2000 there were 21 episodes of B. cepacia bacteremia distributed in four outbreaks. Bacteremia was monomicrobial in 16 episodes and polymicrobial in 5. Eleven episodes of bacteremia were certain and 10 were probable. Sixteen bacteremias were nosocomial and 5 were community-acquired. B. cepacia was found in three opened bottles with intravenous fluids. All B. cepacia isolates (clinical and environmental) belonged to the same biotype and had identical antibiotic susceptibility profile. All children with B. cepacia bacteremia were with indwelling...

Оne hundred and sixty-two patients were studied retrospectively. They were chosen on the basis of... more Оne hundred and sixty-two patients were studied retrospectively. They were chosen on the basis of the following criteria: isolation of B. cepacia from one or more clinical specimens from 1.1.1996 to 31.12.2002, data for hospital acquisition of the bacterium, and admission in intensive care unit. Five hundred and forty-seven cultures of hospital environment were performed in order to find the source of B. cepacia. A total of 411 strains of B. cepacia were isolated between January 1996 and December 2002. Three hundred and ninety of them were from clinical specimens, among which blood cultures predominated. Twenty-one strains of B. cepacia were found in environmental specimens. During the examined 7 years there are three periods without B. cepacia outbreaks. At this time the bacterium probably survives in the hospital environment or colonizes undetected carriers. The most important risk factors for nosocomial acquisition of B. cepacia were invasive procedures (insertion of central veno...

The growth on Burkholderia cepacia selective agar (BCSA) of B. cepacia and other gram-negative an... more The growth on Burkholderia cepacia selective agar (BCSA) of B. cepacia and other gram-negative and gram-positive organisms was evaluated. A total of 265 strains were included in the study: 136 B. cepacia, 88 other gram-negative bacteria, and 41 gram-positive bacteria. The testing of BCSA was conducted in two phases. In phase 1 polymyxin and gentamicin were included in BCSA base. In phase 2 vancomycin was added to this formulation. Plates with Mueller-Hinton agar, BCSA base, BCSA phase 1, and BCSA phase 2 were inoculated with standardized bacterial suspensions and were incubated at 320C up to 72 h. Two hundred and forty-six (92.8%) of tested 265 strains grew on BCSA base. For 19 Staphylococcus spp. this base had inhibitory effect. All B. cepacia isolates, 7 of 25 S. maltophilia, and 8 of 17 Enterococcus spp. grew on BCSA phase 1. None of the tested organisms of family Enterobacteriaceae, Pseudomonas spp., A. baumannii, and Staphylococcus spp. showed growth on BCSA with polymyxin and ...

Phenotypic characterization of bacteria of the Burkholderia cepacia complex was done and their ge... more Phenotypic characterization of bacteria of the Burkholderia cepacia complex was done and their genomovar status was determined. A total of 135 strains were examined with 30 biochemical tests. All tested isolates had identical phenotypic characteristics. Positive results for sucrose and adonitol oxidation allowed their assignation to a group, including genomovars I, III and VII. Production of ornithine decarboxylase and yellow pigment enabled to exclude genomovar VII. Thus, the genomovar identification was reduced to a group of genomovars I and III. Performed phenotypic tests gave opportunity to distinguish definitively the Burkholderia cepacia complex from Burkholderia cepacia-like organisms. These tests allowed separation the Burkholderia cepacia complex at least in four groups and also gave higher degree of differentiation in genomovar group I, III, and VII.

Immunization with modern vaccines is the safest and the most efficacious way of preventing a numb... more Immunization with modern vaccines is the safest and the most efficacious way of preventing a number of infections. The purpose of the present study is to assess parents’ knowledge of the infectious diseases for which vaccine prophylaxis is performed according to the Immunization schedule of the country. A direct individual inquiry is conducted among 400 parents. Their knowledge is evaluated according to a 5-point scale. The highest levels of knowledge are ascertained for clinical manifestations and epidemiology of tuberculosis, and the lowest levels of knowledge are demonstrated for clinical presentations of diphtheria and epidemiology of poliomyelitis. One third of parents are with very good and excellent overall knowledge regarding the infections for which vaccine prophylaxis is performed according to the Immunization schedule. It is necessary to direct the future efforts toward increasing knowledge of all vaccine-preventable diseases by organizing programs for health education of...

Susceptibility of strains of the B. cepacia complex to 23 antimicrobial agents was examined in th... more Susceptibility of strains of the B. cepacia complex to 23 antimicrobial agents was examined in the present study, in order to optimise the choice of drugs for managing the infections caused by these bacteria. One hundred and forty-nine isolates were tested, using the agar dilution method. On the basis of respective MIC all strains were defined as being susceptible to AZL, PIP, CAZ and MER and resistant to AMP/SAM, GEN, TOB and POL B. More than 90% of examined isolates were determined to be susceptible to CFP, FTX, CRO, FEP, IPM, TMP, TMP/SMX, NAL and CIP. The highest activity evaluated by MIC90 demonstrated MER, CAZ, PIP and AZL which makes them agents of choice for therapy of B. cepacia complex infections. The finding that almost all strains were susceptible to β-lactams, TMP/SMX and clinically relevant fluoroquinolones is an unusual observation in that bacterial group.

General Medicine

Poliomyelitis is an acute infectious vaccine-preventable disease with virus aetiology. Children u... more Poliomyelitis is an acute infectious vaccine-preventable disease with virus aetiology. Children up to 5 years suffer most frequently. Poliomyelitis is both medical and social problem as the disease leads to disability in one of 200 infected children and the lethality can reach 10%. Effective vaccines introduced in the middle of the twentieth century changed the epidemiology of infection worldwide. The study aim was to analyze the incidence of poliomyelitis in Bulgaria during the years prior and after introduction of immunization. A documentary method was used and analysis of epidemiological information was performed. Pre-immunization period was characterized by a tendency of increasing the number of infected people. Cases with lethal outcome were registered. The average incidence 0.7 per 100 000 population was recorded till the year of 1935. Over the next two decades the lowest incidence (0.1 per 100 000) was recorded in 1950 and the highest incidence (13.9 per 100 000) in 1957. In ...

World Applied Sciences Journal

The objective of the present study was to evaluate thein vitroactivities of antimicrobial agents ... more The objective of the present study was to evaluate thein vitroactivities of antimicrobial agents againstRhizobium radiobacterstrains, in order to identify the most effective antibiotics for the elimination and control of this bacterium from different biological systems. Carbenicillin, imipenem, meropenem, gentamicin, amikacin, polymyxin B, ciprofloxacin and levofloxacin were determined to be applicable for transformation of the plants with these bacteria. Carbenicillin, carbapenems and fluoroquinolones would be suggested for treatment of human infections.

General Medicine

The purpose of the present study is to ascertain Bulgarian parents’ attitudes towards vaccination... more The purpose of the present study is to ascertain Bulgarian parents’ attitudes towards vaccinations according to the Immunization schedule of Republic of Bulgaria and to investigate the correlation with parents’ knowledge of vaccine-preventable diseases. The study included 632 persons from Pleven region. A structured questionnaire was used. The percentage of parents considering that vaccines must be applied was 90.8%; 40 parents (6.3%) didn’t have opinion on the problem; and 18 parents (2.9%) were against the vaccines. The parents with positive attitudes towards vaccines always demonstrated higher percentage of correct answers to the questions about vaccine-preventable diseases in comparison to parents with negative and indefinite attitudes. A statistically significant difference was found by gender in parents’ attitudes towards vaccines (р < 0.05). There were no differences in other demographic characteristics. The presented results give grounds to make the following conclusions:...