Microbiological characterization of Streptococcus pneumoniae and non-typeable Haemophilus influenzae isolates as primary causes of acute otitis media in Bulgarian children before the introduction of conjugate vaccines

Abstract

BackgroundPneumococcal 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.MethodsS. 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.ResultsThe 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.ConclusionsThe 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%.

Macrolones Are a Novel Class of Macrolide Antibiotics Active against Key Resistant Respiratory Pathogens In Vitro and In Vivo

“…It is possible that additional interactions lead to the improved activity against strains with cMLSb compared to the activities of related antibiotics. Nonetheless, it is also reasonable to assume that the changed azi-NN-Cl (1) 0.28 azi-ON-Cl (7) 0.31 azi-ON (8) 0.49 clari-ON-Cl (9) 0.86 claric-NO-Cl (11) 0.73 claric-NO (12) 0.68 azi-OO-Cl (13) 0.58 azi-OO (14) 0.47 claric-OO-Cl (17) 0.87 azi-OON-Cl (19) 0 Inducible macrolide resistance is of strong clinical significance. Depending on the study and the geographical region concerned, macrolide resistance has been detected in 30 to 90% of S. pyogenes isolates (40,52).…”

“…Erythromycin resistance is predominantly mediated by two mechanisms: ribosome modification by methylation, resulting in a phenotype of inducible resistance to macrolide-lincosamide-streptogramin B (iMLSb) or constitutive resistance to macrolide-lincosamide-streptogramin B (cMLSb), and the production of efflux pumps, resulting in the M phenotype. In addition, pneumococcal isolates with mutations in 23S rRNA domains II and V and ribosomal proteins L4 and L22 have been reported, but their clinical significance is still rather low (10)(11)(12)(13). In Streptococcus pyogenes, inducible erm gene expression has three distinct patterns with different levels of resistance to macrolides with a 14-, 15-, or 16-membered macrolactone ring (14).…”

Frequency of resistance to penicillin and erythromycin of pneumococcal strains that caused ottis media

“…Studija o osetljivosti pneumokoka izazivača AOM u Bugarskoj iz 2014. godine prikazala je 28,1% rezistentnih izolata (12). U zemljama Mediterana, gde su stope rezistencije pneumokoka na antibiotike bile tradicionalno visoke, beleži se pad nakon uvođenja obavezne pneumokokne vakcine.…”

“…Nešto nižu incidenciju rezistencije prikazuju okolne zemlje, Bugarska (46,9%), Rumunija (58,3%) i Hrvatska (37%) (12,14,11). Do sada je već opisana pojava da rezistencija streptokoka na makrolide raste sa većom potrošnjom ovih antibiotika (15).…”

Bacterial Etiology and Pneumococcal Serotypes in Turkish Children with Acute Otitis Media

“…Streptococcus pneumoniae and Haemophilus influenzae have been consistently reported to be the two major bacterial pathogens responsible for AOM, mainly by studies in the USA and European countries [5][6][7]. Three pneumococcal conjugate vaccines (PCVs) are currently licensed for use in children and they have showed modest efficacy against AOM overall [8]. Randomized clinical trials with a 7-valent pneumococcal conjugate vaccine (PCV-7) in the USA and Finland showed reductions in the incidence of AOM of 6-9% [9][10][11][12].…”