Investigation of virulence factors, phylogenetic group features, and the presence of ST131 clone in escherichia coli isolates, A urinary tract infection agent in children

AIM: In this study; antimicrobial resistance rates, phylogenetic group distributions, virulence factors frequency, and belonging to the O25b/ST131 clone of a total of 200 Escherichia coli isolates (causative agents of 100 first and 100 recurrent urinary tract infections (UTI)) isolated from pediatric patients' (3-18 years) mid-stream urine samples between January 2021 and September 2021. The isolates obtained from Ankara University Faculty of Medicine Cebeci Hospital Central Microbiology Laboratory with the preliminary diagnosis of UTI of pediatric patients. In addition to contributing to the surveillance data in our country, it is aimed to shed light on new studies for diagnosis, treatment and prophylaxis options that can be developed for a more effective UTI management by investigating the distribution of the obtained data between the first and recurrent UTI agents and between the isolates belonging and not belonging to the O25b/ST131 clone. MATERIALS AND METHODS: Antimicrobial susceptibility testing of the conventionally identified E. coli isolates evaluated by Kirby-Bauer disc diffusion method, extended spectrum beta-lactamase (ESBL) production assessed by double disc synergy test, biofilm formation investigated by microplate method and hemolysin production detected by blood agar cultivation technique. Polymerase chain reaction (PCR) was used for phylogenetic grouping, investigation of the O25b/ST131 clone and virulence genes, identification of uropathogenic E. coli (UPEC) at the molecular level, and virotyping. Pulsed-field gel electrophoresis (PFGE) was performed to reveal the relationship between isolates collected at different times from the same patient. RESULTS: The highest antimicrobial resistance rates were against ampicillin (n=100, 50%), amoxicillin-clavulanic acid (n=43, 21.5%), cefazolin (n=99, 49.5%), cefotaxime (n=43, 21.5%) and trimethoprim-sulfamethoxazole (n=55, 27.5%). In recurrent UTI agents (n=100), according to the first UTI agents, resistance rates were higher for cefotaxime (n=29, 29%), cefepime (n=25, 25%) and trimethoprim-sulfamethoxazole (n=35, 35%); in O25b/ST131 isolates (n=67), comparing to the non-O25b/ST131 isolates (n=133), the resistance rates were higher for ciprofloxacin (n=17, 25.4%), amikacin (n=3, 4.5%) and gentamicin (n=10, 14.9%) (p<0,05). The rate of multidrug-resistant (MDR) and extended-spectrum beta-lactamase (ESBL) producing isolates was found to be 29% (n=58) and 19% (n=38), respectively. The rates of MDR and/or ESBL were higher in recurrent UTI isolates than in first UTI agents (n=36 (36%) vs n=22 (22%); n=27 (27%) vs n=11 (11%) respectively, p<0.05). Biofilm formation was observed in three (1.5%) of the isolates and all of them were found to belong to phylogenetic group A. Hemolysis production was observed in 29 (14.5%) of the isolates, and the ratio of the O25b/ST131 clone in these isolates was found to be higher than the non-O25b/ST131 (n=23 (79%) and n=6 (21%) respectively, p<0.0001). It was found that 91 (45.5%) of the isolates were in D, 75 (37.5%) in B2, 25 (12.5%) in A, and 9 (4.5%) in B1 phylogenetic group. It was determined that the isolates in groups B2 and D had higher antimicrobial resistance and carried more virulence genes (p<0,05). Sixty-seven (33.5%) of the isolates were found to belong to the O25b/ST131 clone. The rates of the O25b/ST131 clone among the first and recurrent UTI agents were found to be similar (p>0,05). The most common virulence factor group were adhesins [fimH n=194 (97%), papA n=114 (57%), yfcV n=99 (49.5%)] followed by iron uptake systems [fyuA n=171 (85.5%), chuA n=156 (78%), iutA n=146 (73%)], while the least detected virulence genes were found in toxin group [vat n=64 (32%), hlyA n=31 (15.5%), cnf I n=13 (6.5%)]. All virulence factors were detected more frequently in isolates belonging to the O25b/ST131 clone compared to isolates not belonging to this clone (p<0.05). The most common virulence gene detected with antimicrobial resistance was papA (ampicillin, amoxicillin-clavulanic acid, piperacillin-tazobactam, cefazolin, cefotaxime, cefepime, ciprofloxacin and trimethoprim-sulfamethoxazole resistance, p<0.05). One hundred and one (50.5%) of the isolates were defined as UPEC at molecular level. Sixty-five (97%) of the isolates belonging to the O25b/ST131 clone and 36 (27.1%) of the isolates not belonging to this clone were defined as molecular UPEC (p<0.0001). In our study, 40 (59.7%) of the isolates in the O25b/ST131 clone were detemined as virotype B, while 18 (26.9%) of them as virotype C, 3 (4.5%) of them as virotype A and 3 (4,5%) of them were as virotype D. Thirty-three E. coli isolated from 15 patients were evaluated with PFGE, and it was observed that the latter isolate and the first isolate of nine patients (60%) had the same band profile. CONCLUSIONS: UTI caused by E. coli is an important health problem in children. Especially, E. coli O25b/ST131 clone is becoming a serious public health problem due to its high virulence and antimicrobial resistance rates. Focusing on surveillance, diagnostic testing, treatment algorithms, and preventive measures for this clone will help to manage challenging E. coli infections, and will shed light on the development of new prophylaxis, treatment or vaccine strategies, and studies to prevent carriage and colonization.