Characterization and comparison of extended-spectrum β-lactamase (ESBL) resistance genotypes and population structure of Escherichia coli isolated from Franklin's gulls (Leucophaeus pipixcan) and humans in Chile

Abstract

We investigated the general level of antibiotic resistance with further analysis of extended-spectrum beta-lactamase (ESBL) prevalence, as well as the population structure of E. coli in fecal flora of humans and Franklin's gulls (Leucophaeus pipixcan) in central parts of Chile. We found a surprisingly high carriage rate of ESBL-producing E. coli among the gulls 112/372 (30.1%) as compared to the human population 6/49 (12.2%.) Several of the E. coli sequence types (STs) identified in birds have previously been reported as Multi Drug Resistant (MDR) human pathogens including the ability to produce ESBLs. This means that not only commensal flora is shared between birds and humans but also STs with pathogenic potential. Given the migratory behavior of Franklin's gulls, they and other migratory species, may be a part of ESBL dissemination in the environment and over great geographic distances. Apart from keeping the antibiotic use low, breaking the transmission chains between the environment and humans must be a priority to hinder the dissemination of resistance.

Figure 1. A neighbor joining tree based on seven concatenated gene sequences obtained by MLST.

Genetic relationships between different STs and the distribution of the isolates between humans and Franklin's gulls are shown. The new and previously undescribed STs are marked by number 1711 or a higher number. The reference strain Z205 was used to root the tree. Forty-seven strains of the ECOR collection were included in the analysis as references.

Figure 2. Minimal spanning tree calculated from the allelic differences between the isolates.

The tree shows the relationship between the genetic analysis and the geographical source of the isolates.