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Were studied the genes encoding the virulence factors of 221 strains: E. coli O 6 :H 1 (194) and E. coli O 25 :H 4 (27), isolated in 2014-2018 from stool samples of children and adults examined according to epidemic indications. Molecular methods included PCR with hybridization-fluorescence and electrophoresis detection of amplified products. The strains did not have virulence genes for diarrheagenic E. coli (DEC) pathogroups EPEC, ETEC, EIEC, EHEC, EAggEC, and belonged to the phylogenetic group B2. They contained from four to eight genes encoding virulence factors of ExPEC: E. coli O 6 :H 1 - pap (68,6%), sfa (87,6%), fimH (96,4%), hly (62,4%), cnf (74,7%), iutA (97,9%), fyuA (95,9%), chu (100%); E. coli O 25 :H 4 - pap (66,7%), afa (22,2%), fimH (100%), hly (44,4%), cnf (44,4%), iutA (100%) , fyuA (100%), chu (100%). The antimicrobial susceptibility testing to 6 classes of antimicrobials (beta-lactams, fluoroquinolones, aminoglycosides, nitrofurantoin, sulfanilamide, trimethoprim / sulfamethoxazole) according the EUCAST. 60,3% of E. coli O 6 :H 1 were sensitive to antibiotics, E. coli O25:H4 remained sensitive to carbapenems and nitrofurans. Extended-spectrum cephalosporins resistance was due to the production ESBL (CTX-M). The 57,1% resistant strains of E. coli O 6 :H 1 and 100% of E. coli O 25 :H 4 strains belonged to the MDR phenotype. The XDR phenotype had one in five MDR strains of E. coli O6:H1 and E. coli O 25 :H 4 . All strains of E. coli O 25 :H 4 belonged to ST131. Given the important role of E. coli in human pathology, detection of virulence genes should be performed to confirm the etiological significance of the isolated strain., Competing Interests: The authors declare no conflict of interest.

The article presents the results of antimicrobial resistance monitoring of Salmonella isolated from children and adults with diarrhea in St. Petersburg in 2014-2018. In 746 isolates of 42 serovars more than 90,0% belonged to three: S. enteritidis (79,6%), S. typhimurium (6,8%) and S. infantis (3,8%). The antimicrobial susceptibility testing (according the EUCAST) to 7 classes of antimicrobials revealed the resistance in 78,6% of Salmonella. Low-level quinolone resistance (MIC of ciprofloxacin 0,12-0,5 mg/l) was detected in 63,3% isolates (S. enteritidis -71,0%, S. typhimurium - 15,7%, S. infantis - 89,3%) and was due to five kinds of single nucleotide substitutions in gyrA: Asp87Tyr - 36,1% of studied isolates (only S. infantis); Ser83Phe - 22,2% (only S. enteritidis); Asp87Asn - 19,4% (S. enteritidis, S. typhimurium, S. hadar, S. newport); Ser83Tyr -11,1% (S. enteritidis and S. infantis) and Asp87Gly - 8,3% (only S. enteritidis). Only in one S. kentucky isolate with high-level fluoroquinolone resistance (MIC of ciprofloxacin > 8,0 mg/l) two substitutions (Ser83Phe and Asp87Asn) were detected. Two Salmonella isolates (S. typhimurium and S. corvallis) had plasmid-mediated quinolone resistance (qnrS). Extended-spectrum cephalosporin resistance was found in 6 Salmonella serovars (1,6%). The bla-genes were detected: of genetic group CTX-M1 - in 10 isolates (serovars S. typhimurium, S. enteritidis, S. abony, S. coeln and S. virchow), CTX-M2 - in 2 S. typhimurium isolates, CTX-M9 - in three S. enteritidis isolates. In one S. typhimurium CTX-M1 and CTX-M2 were detected. The gene of CMY-2 (molecular class C cephalosporinase) was revealed in two isolates (S. newport and S. enteritidis). Our study showed that Salmonella (the main bacterial pathogen of acute diarrhea in children and adults) isolated in Saint-Petersburg had antimicrobial resistance to drugs of choice for salmonellosis treatment., Competing Interests: The authors declare no conflict of interest.