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

Abstract

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 treatment.

Relationship between MLSB resistance and the prevalent virulence genotypes among Bulgarian Staphylococcus aureus isolates

“…A similar rate to the present resistance in Bulgaria (96.09%) has been found in recent years in Turkish pediatric patients with HA infections [2]. The basic mechanism underlying the resistance to penicillins is associated with blaZ and the production of extracellular betalactamases that hydrolyze the beta-lactam ring, which is the active center of the antimicrobial agent, and can interfere with the successful treatment of other respiratory pathogens [19]. The geographical distribution of MRSA attributed to mecA at present varies in a very wide ranged depending on the origin of the infection, CA or HA.…”

“…The present rate of 34.02% in the tested Bulgarian isolates (both of CA and HA) is similar to 40.2% reported in Central Greece [13], up to 48.4% in HIV positive patients in Ethiopia [21], 64.1% in Hospitals in China [22], 79% in a tertiary hospital in Ismir during 2011-2012 [26] and 91% in Tokyo, Japan [27]. The resistance to MLSB antibiotics (per EUCAST) in Bulgarian clinical S. aureus isolates has not increased as rapidly in recent years but varied from of 30% in 2014 [19] to a higher incidence of 34% in 2018-2019, with an increasing trend during the last 5 years of the investigation. Another problem that was found was that the most prevalent mechanisms of resistance to this group of antimicrobials in the tested strains were erm genotypes, which confer a higher level of resistance, including clindamycin, which is important for severe soft tissue infections (Tables 2 and 3).…”

“…Penicillin resistance has been known for a long time and has progressed in Bulgarian comparison to earlier data from 2014, when 90% of Bulgarian staphylococcal isolates were reported resistant [19]. A similar rate to the present resistance in Bulgaria (96.09%) has been found in recent years in Turkish pediatric patients with HA infections [2].…”

“…The methicillin resistance rate among the Bulgarian S. aureus isolates both of CA and HA infections during 2017-2019 observed in this study was 11.03% and the EARS-Net data about 2017-2018 for MRSA of invasive isolates in Bulgaria were between 13.7 and 17.6% [23]. Some decreasing trend during the last 5 years can be noted when compared with data of about 20% MRSA in 2014 from a previous study in Bulgaria [19] and EARS-Net data for 20.8% MRSA of invasive isolates in Bulgaria during 2014 [24]. The macrolide resistance in the Bulgarian staphylococcal isolates was more problematic in this period.…”

Distribution of Virulence Genes in Moraxella catarrhalis Isolated from Clinical Samples in the North of Iran

“…In sinusitis, both in acute and chronic conditions, M. catarrhalis is the third most common cause of infection, and its prevalence may be up to 20% (15). In a study conducted by Gergova et al (16) to determine the prevalence of M. catarrhalis in patients with sinusitis, the prevalence of the bacterium was reported as 39%.…”