A. Alexandrova

Medical University of Sofia, Ulpia Serdica, Sofia-Capital, Bulgaria

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Publications (5)3.79 Total impact

  • L. Setchanova · I. Stancheva · A. Alexandrova · T. Kostyanev · I. Mitov
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    ABSTRACT: Aims: The 10-valent pneumococcal conjugate vaccine (PCV10) was first introduced in Bulgarian Immunization Program since April 2010. The aims were to identify the etiological structure of acute otitis media (AOM) in children, resistance to antibiotics of isolated otopathogens and pneumococcal serotypes two to four years after introduction of PCV10 in our immunization schedule. Methods: Middle ear fluid (MEF) was obtained from 185 children with severe AOM. The specimens were collected after spontaneous membrane rupture or by tympanocentesis from March 2012 to December 2014. Bacterial isolates were identified by routine microbiological methods. S. pneumoniae and H. influenzae strains were serotyped by Quellung reaction and latex agglutination. Antimicrobial susceptibility testing was done by MICs determination with broth microdilution and E-test method. Results: Among 106 culture positive MEF samples (57.3%) the most frequently isolated AOM pathogens were: S. pyogenes (27.4%), S. aureus (23.6%), followed by S. pneumoniae (17.0%) and H. influenzae (13.2%). All H. influenzae isolates (n=14) were non-typable (NTHi). Among S. pneumoniae isolates (n=18) the following serotypes were determined: 19F (38.9%), 19A (22.2%), 3 (16.7%), 9V (11.1%), 6A and 18B (5.5% each). Vaccine serotypes included in PCV10 were 50%. All pneumococcal isolates from serotypes 19F and 19A were resistant to antibiotics. Nonsusceptibility rate to oral penicillin was 83.3% among all S. pneumoniae strains. Both, macrolideresistance and multi-drug resistance was 61.1 % among pneumococcal isolates. Conclusions: PCV10 implementation in Bulgaria was associated with a rapid reduction of severe, complicated pneumococcal AOM episodes and additionally, a reduction of AOM cases caused by non-typable H. influenzae was observed. The proportion of non-vaccine types increased to 50% after PCV10 implementation. Despite introduction of the pneumococcal conjugate vaccine multidrug-resistant vaccine serotypes 19F and 19A have been successfully spread in post-vaccine period.
    No preview · Article · Jan 2015
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    ABSTRACT: Background Pneumococcal and Haemophilus influenzae type b (Hib) vaccines were introduced in our national immunisation program in April 2010. The aims of this retrospective, laboratory-based study were to determine the serotypes and antibiotic resistance of Streptococcus pneumoniae and H. influenzae isolates from middle ear fluid (MEF) collected before the introduction of immunization. Methods S. pneumoniae (n = 128) and H. influenzae (n = 40) strains isolated from MEF of children with AOM between 1994 and 2011 were studied. MICs were determined by a microdilution assay. Serotyping of S. pneumoniae was done by Quellung method and PCR capsular typing was used for H. influenzae. Macrolide resistance genes were detected by PCR for erythromycin resistant S. pneumoniae (ERSP). DNA sequencing of ftsI gene was performed for ampicillin nonsusceptible H. influenzae. Results The most common serotypes found among children with pneumococcal AOM were 19 F (20.3%), 6B (15.6%), and 19A (10.9%). The potential coverage rates by the PCV7, PCV10 and PCV13 of children aged < 5 years were 63.6%, 66.4% and 85.5%, respectively. Reduced susceptibility to oral penicillin was seen in 68.1%; resistance to erythromycin was 46.9%. We found erm(B) gene in 56.7% of the ERSP, mef(E) gene in 25%; 15% harbored both genes erm(B) + mef(E) and 3.3% had mutations of L4 ribosomal protein. Of the 40 H. influenzae isolates 97.5% were nontypeable. Nonsusceptibility to ampicillin occurred in 25%. Ampicillin resistance groups were: β-lactamase-positive ampicillin resistant (BLPAR) strains (10%), β-lactamase-negative ampicillin resistant (BLNAR) strains (12.5%) and β-lactamase-positive amoxicillin-clavulanate resistant (BLPACR) strains (2.5%). Among BLNAR and BLPACR most of the isolates (5/6) belonged to group II, defined by the Asn526Lys substitution. Conclusions The levels of antibiotic resistance among S. pneumoniae and H. influenzae causing severe AOM in children are high in our settings. The existence of multidrug-resistant S. pneumoniae serotype 19A is of particular concern. The rate of BLNAR and BLPACR strains among H. influenzae isolates was 15%.
    Full-text · Article · Mar 2013 · Annals of Clinical Microbiology and Antimicrobials
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    L P Setchanova · A Alexandrova · I Mitov · D Nashev · T Kantardjiev
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    ABSTRACT: The 10-valent pneumococcal conjugate vaccine (PCV10) was introduced as a mandatory vaccine in Bulgaria in April 2010. We report on the serotype distribution and the antimicrobial resistance of 222 invasive Streptococcus pneumoniae isolates collected from all age groups before the introduction of PCV10. PCV7, PCV10, and PCV13 covered 43.7, 59.9, and 78.8% of all invasive pneumococcal strains, and 64.2, 79.1, and 89.6% of isolates involving children less than 5 years of age. Penicillin resistance was found in 30.1% of the isolates responsible for meningitis and in 5.0% of isolates responsible for other invasive infections. Overall, erythromycin resistance was found in 19.4% of all invasive strains. The erm(B) was the most prevalent pneumococcal macrolide resistance genotype (63.2%) and dual mechanisms of both genes the erm(B) and mef(E) were detected in 15.8% of 19 erythromycin resistant isolates during the period 2006-2010. The prevalence and spread of serotypes 19F, 6B, and 19A during the last period may have contributed to the high predominance of erm(B) genotype in comparison of mef genotype, which was predominant in our country among erythromycin-resistant isolates before 2005. Continuing surveillance is required after the recent introduction of PCV10 in order to observe future developments of any serotype changes in the Bulgarian population, as well as surveillance of antimicrobial susceptibility of invasive S. pneumoniae isolates.
    Full-text · Article · Feb 2012 · Journal of chemotherapy (Florence, Italy)
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    ABSTRACT: Aims: To identify causative serotypes and antimicrobial resistance of invasive (IPD) and respiratory (RPD) S. pneumoniae strains isolated from children with pneumococcal disease before the introduction of pneumococcal conjugate vaccines (PCV) for routine immunization in Bulgaria. Methods: 146 strains were collected between 1998 and 2009 from children aged 1 month to 14 years: 67 invasive strains31 from CSF, 21 from blood, 15 pleural fluid specimens, and 79 respiratory strains-55 ear fluid, 19 sputum and 5 samples from sinus pus. The antimicrobial resistance was determined by MIC. The isolates were serotyped by the Neufeld reaction using type-specific antisera. Results: Twenty three different serotypes were identified among 146 studied isolates. The most prevalent serotypes among invasive strains were: 19F, 14, 23F, 5, 9V, 6B, 7F u 1. In respiratory infections the most prevalent serotypes were: 19F, 19A, 14, 23F, 9V, 6A, 6B, 15B and 3. Typical serotypes for IPD were serotypes 5, 7F and 1, and three other serotypes were typical for RTI: 19A, 6A and 3. The vaccine serotypes in the 7-valent conjugate vaccine (7PCV), 10PCV and 13PCV were responsible for 56.7%, 79.1% and 86.6% of all invasive strains, respectively. The coverage of 7PCV, 10PCV and 13PCV for RTI were 53,2%, 57.0% and 81.0%, respectively. The coverage of the two new vaccines 10PCV and 13PCV was better than 7PCV for IPD. The coverage of 13PCV was the best for RTI strains, but 10PCV has showed to induce additional protection against non-capsulated H. influenzae (the second in rank causative agents of otitis media). S. pneumoniae strains resistant to antimicrobials were from serogroup/serotypes: 19,14,23,6 and 9, which are included in PCV vaccines. The coverage of 7PCV, 10PCV and 13PCV for penicillin G-non-susceptible strains (17 isolates -11.6% resistance) was 94.1%. The macrolide-resistant pneumococci were 32.2% among all isolates, and the coverage of 7PCV, 10PCV and 13PCV for macrolide-resistant strains was 66.0%, 66.0% and 97.9%, respectively. Conclusions: The introduction in Bulgaria of PCVs in National Vaccination Plan will be accompanied by reductions in both the incidence of pneumococcal disease and reduction in dissemination of antibiotic non-susceptible S. pneumoniae strains.
    No preview · Article · Jan 2010 · Pediatriya
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    ABSTRACT: SUMMARY In total, 413 clinical isolates of Streptococcus pneumoniae were collected from four University laboratories in Sofia, Pleven, Plovdiv and Varna for the period of 2006- 2008. 150 strains (36, 3%) of all 413 tested S. pneumoniae were erythromycin-resistant (ERSP). The most prevalence of ERSP were observed in children under 5 years (80.0%). The results of conventional PCR showed presence of erm(Â) gene among 64.7% of the strains, mef(Å) gene among 29.3%, and 9 strains (6%) carried both erm(Â)+mef (Å). Serotypes 6Â, 19F and 19A were the most prevalent among ERSP with erm(Â) gene, and serotype 14 was predominant among strains harboring mef (E) gene. Phenotypic characterization of ERSP with the triple- disc test (4) completely confirmed the genotype: 106 strains were with MLSb phenotype (70.7%, including the 9-th strains harboring both erm (Â)+mef (Å) genes ) and 44 were with Ì phenotype (29.3%). Ìacrolides are widespread used antibiotics in therapy of pneumococcus infections in our country and ERSP increased with accelerated rates: from 20% in 2000, to 25% in 2005 (5), till 36% in the present research. The efflux mechanism of macrolide resistance, which were predominant before in Bulgaria (5), now give place to widely spread MLSB phenotype and genotype reffering with target modification. The dissemination of macrolide resistance encoded by erm (Â) gene were 30% in 2000, increased to 43% in 2005 and 70% in 2008.
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