Main Characteristics of Helicobacter pylori Strains and Infection in Bulgaria

The aim of the work was to summarize some specific characteristics of Helicobacter pylori strains and infection in Bulgaria according to our studies. Data of our studies, mostly those from the last decade are discussed. Infection seroprevalence dropped from 82.6% to 72.4% in adult blood donors over 18 years, being only 24.2% in children. Virulence genes were frequent (>80%) in strains from symptomatic patients for vacuolating cytotoxin (vacA) s1a and cytotoxinassociated gene A (cagA) and outer inflammatory protein (oipA) in active status. In Bulgaria, vacA i alleles were more useful to determine the strain virulence compared with other vacA alleles. Using EUCAST breakpoints, overall H. pylori resistance rates were: metronidazole 33.8%, clarithromycin 28.1%, levofloxacin 19.4%, amoxicillin 4.0% and tetracycline 3.7%. Multidrug resistance was found in 4.2% of untreated and more often (15.4%) in treated adults, and in 1.2% of untreated children. Risk factors, resistance evolution and extended anamnesis are discussed. Lactobacillus delbrueckii subsp. bulgaricus strains inhibited the growth of a portion of H. pylori strains, including those resistant to antibiotics. Neutralized filtrates of 7 strains suppressed the growth of >2/3 of H. pylori strains. There was an association between regular honey consumption and a lower infection rate, and an inverse association between honey and yoghurt intake and anti-CagA antibodies against virulent strains. In conclusion, although the infection prevalence decreases in younger people, still the high infection prevalence, common virulence genes, increasing resistance to clarithromycin and quinolones and multidrug resistance show that H. pylori infection problem in our country is not yet fully resolved.