Microbiological Features of Upper Respiratory Tract Infections in Bulgarian Children for the Period 1998-2014

Background: Across the globe, upper respiratory tract infections (URTIs) are the most prevalent cause of morbidity in childhood. Aims: The aim of our study is to analyze the incidence and etiology of bacterial URTIs in Bulgarian children, as well as the increasing antimicrobial resistance to the most common etiologic agents over a period of 17 years. Study Design: Retrospective study. Methods: The study material comprised the data from 4768 patients (aged 1-16 years) with URTI during the period from 1998-2014. Specific microbiology agent detection was performed by culture examination. Susceptibilities to the investigated pathogens were determined by the disk diffusion method and minimal inhibitory concentration according to the criteria of the Clinical and Laboratory Standards Institute (CLSI). Polymerase chain reaction was used to detect the presence of β-lactam resistance genes. Results: We identified the following as the most common URTI bacterial pathogens: Streptococcus pneumoniae (40.94%), Streptococcus pyogenes (34.16%), Haemophilus influenzae (44.23%), Moraxella catarrhalis (39.19%) and Staphylococcus aureus (23.88%). In more than 70% of cases, a polymicrobial etiology was found. The most commonly affected individuals were pre-school-aged children, which accounted for more than 36% of all patients. During the study period, a dramatic increase in resistance to antibiotic agents was observed. The most frequent types of resistance were the enzymatic inactivation of penicillins and cephalosporins (close to 100% in staphylococci and moraxellae) and inducible macrolide-lincozamide resistance (about 20% of Gram-positive cocci). Conclusion: Due to mandatory immunization against pneumococci and H. influenzae in Bulgaria and the vast expanding resistance to the most popular antimicrobial agents changes in the etiology of URTI have recently been noted. Regular analysis of this etiological dynamic and the antimicrobial resistance of respiratory pathogens is important for choosing the correct therapy and successful treatmen