Epidemiología clínica y molecular de bacteriemias por Escherichia coli en el Hospital Clínico Universitario Virgen de la Arrixaca

Resumen

OBJECTIVES: The main objective of this study was to analyze the epidemiological, clinical and microbiological traits of Escherichia coli bacteraemias at the Hospital Clínico Universitario Virgen de la Arrixaca during the period of one year. MATERIAL AND METHODS: Demographic and epidemiological data were collected from all patients with documented E. coli bacteraemia during the year 2013. Consecutive isolates of Escherichia coli from blood cultures were recovered and studied. The biochemical identification and antibiotic sensitivity of the isolates were performed using the Vitek2¿ automated system. The presence of extended spectrum betalactamases (ESBL) was suspected in strains where the minimum inhibitory concentrations for cefotaxime and ceftazidime were equal to or greater than 2 microgr / ml and were confirmed phenotypically by the double disc synergy method according to CLSI. The characterization of the ESBL enzymes was carried out, the phylogenetic group, virulence factors, the specific presence of ST69 ST73, ST95, ST131 clones and ST ("Sequence type") of all isolates belonging to the phylogenetic B2 and ESBL producers not previously characterized. RESULTS: The incidence of bacteraemia caused by E. coli was of per 86.5 episodes / 100,000 inhabitants per year. The mean age in adults was 63,9 years and 72,8% presented some comorbidity. 58.5% of the bacteriemias were community adquired and 59.5% were of the urinary focus. A 9.9% of E. coli strains were ESBL producers and total resistance to ciprofloxacin was 39.6%. Higher antibiotic resistance was found between isolates of E. coli producing ESBLs and in strains resistant to ciprofloxacin. The existence of chronic lung disease and the administration of previous antibiotic therapy were both risk factors for the acquisition of ESBL E. coli bacteraemia, observing a tendency for bacterial acquisition of E. coli resistant to ciprofloxacin. 80% of the ESBLs were of the CTX-M family and 46,7% were of the CTX-M-15 subfamily. The most abundant phylogroup was B2 (52.9%) followed by group D (13.4%). The ExPEC strains percentage was 69.8% and the most prevalent virulence factor was iutA. Among the isolates of phylogenetic group B2, the more frequent clonal complex was ST95 (15%), followed by ST73 (12.8%) and ST131 (10.7%). ST69 comprised 67% of isolates of the phylogenetic group D. Among the ESBL strains, 38.9% were of ST131 clone, 85% of which were associated with CTX-M 15, and 11.1% were of ST155 clone, respectively . Statistically significant differences were observed regarding the early administration of antimicrobials and diabetes mellitus in bacteraemias by non-ST73 and non-ST131 strains, respectively. STs 69, 73 and 95 strains were more sensitive generally while ST131 strains were more resistant. CONCLUSIONS: In our study, we have observed a prevalence of E. coli bacteraemias of community acquisition and urinary origin in patients of advanced age and high comorbidity. The presence of ESBL and resistance to ciprofloxacin were associated with higher resistance rates to other antimicrobial families. The risk factors for the acquisition of ESBL E. coli bacteraemia were earlier antimicrobial therapy and chronic lung disease, and a trend was observed in resistant to ciprofloxocin E. coli strains. It was observed a high presence of microorganisms belonging to phylogenetic group B2 and classified as ExPEC. The major STs were ST95, ST73, ST131 and ST69. In ESBL strains a predominance of ST131 associated with CTX-M 15 was observed. Either earlier administration of antimicrobials or diabetes mellitus were protective factors for the acquisition of E. coli ST73 and ST131 bacteraemias, respectively.Finally, ST131 was associated with higher resistance rates.