Antimicorbial Susceptibility, Clonal and Serotype Diversity of Streptococcus pneumoniae Isolated from Children with Acute Otitis Media in Moscow

Clinical Microbiology and Antimicrobial Chemotherapy. 2016; 18(2):84-92

Type
Journal article

Objective.

Streptococcus pneumoniae (pneumococcus) is the leading cause of acute otitis media (AOM) in children. Hereby, we describe antibiotic susceptibility, clonality, and serotype distribution of pneumococci isolated from the middle ear fluid (MEF) in children with AOM.

Materials and Methods.

MEF specimens from children ≤5 years of age with AOM were collected in 4 pediatric hospitals in Moscow in 2011–2013. Isolation and identification of pneumococcus was performed using standard microbiological procedures. Antibiotic susceptibility was tested by means of the disk diffusion method, minimal inhibitory concentration (MIC) for penicillin and amoxicillin was determined by the E-test. Serotyping was performed using pneumococcal antisera from the Staten Serum Institut (Denmark). For the multilocus sequence typing, a conventional protocol was used.

Results.

A total of 107 pneumococcal isolates were analyzed. Penicillin nonsusceptibility (MIC >0.06 µg/L) was found in 45% (48107) isolates, macrolide resistance had 34% (36107) pneumococci. The vast majority of macrolide-resistant isolates (92%, 3336) carried the ermB gene conferring a constitutive MLSB-phenotype, i.e. simultaneous resistance to all macrolides, lincosamides, streptogramin B. A multidrug resistant (MDR) phenotype displayed 30% (32107) pneumococci, however all isolates were susceptible to amoxicillin (MIC ≤2 µg/mL). Ten of 32 (31%) MDR isolates belonged to clonal complex (CC) 320, the rest were distributed among 7 different CC. In the serotype distribution, isolates with serotype 19F (27%), 3 (12%), 6B (11%), 14 (11%), 19A (9%), and 23F (8%) predominated. Available polysaccharide pneumococcal conjugated vaccines (PCV) cover the majority of AOM serotypes (PCV7, 66%; PCV10, 67%; PCV13, 93%).

Conclusions.

AOM pneumococci circulating in Moscow are characterized by a substantial reduction in antimicrobial susceptibility and pronounced clonality. Pneumococcal serotype distribution suggests advantage of a PCV with the extended coverage.

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