ABSTRACT
Background Knowledge on the molecular epidemiology of Escherichia coli causing E. coli bacteremia (ECB) in the Netherlands is almost exclusively based on extended-spectrum beta-lactamase producing E. coli isolates (ESBL-PEc) that are responsible for about 10% of all ECB episodes. We determined clonal differences and differences in resistance and virulence gene content between non-ESBL-producing E. coli (non-ESBL-PEc) and ESBL-PEc isolates with different epidemiological characteristics.
Materials/methods A random selection of non-ESBL-PEc isolates as well as all available ESBL-PEc blood isolates were obtained from two Dutch hospitals between January 2014 and December 2016. For comparative analysis, whole genome sequencing was performed of all isolates to infer the sequence types (STs), serotypes, antibiotic resistance by either acquired genes or chromosomal mutations and virulence gene (VG) scores, based on presence of 49 predefined putative pathogenic VG.
Results ST73 was most prevalent among the 212 non-ESBL-PEc (N = 26, 12.3%) and ST131 among the 69 ESBL-PEc (N = 30, 43.5%). Prevalence of ST131 among non-ESBL-PEc was 10.4% (N = 22, P value < 0.001 compared to ESBL-PEc). O25:H4 was the most common serotype in non-ESBL-PEc and ESBL-PEc. Median total resistance gene counts were 42 (IQR 39 – 45) and 46 (IQR 43 – 50) for non-ESBL-PEc and ESBL-PEc, respectively (P value < 0.001). Median acquired resistance gene counts were 1 (IQR 1 – 6) and 7 (IQR 4 – 9) for non-ESBL-PEc and ESBL-PEc, respectively (P value < 0.001). Median VG scores were 13 (IQR 9 – 20) and 12 (IQR 8 – 14) for non-ESBL-PEc and ESBL-PEc isolates, respectively (P value = 0.002). Resistance gene and VG content varied between different E. coli STs.
Conclusions We observed differences between non-ESBL-PEc and ESBL-PEc blood isolates in ST distribution, resistance gene and virulence gene content.