A. Alexandrova

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

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Publications (3)3.79 Total impact

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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%.
    Annals of Clinical Microbiology and Antimicrobials 03/2013; 12(1). DOI:10.1186/1476-0711-12-6 · 2.19 Impact Factor
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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.
    Journal of chemotherapy (Florence, Italy) 02/2012; 24(1):12-7. DOI:10.1179/1120009X12Z.0000000004 · 1.60 Impact Factor
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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.