Conference in Seminarios VISAVET 2021

November 29^th, 2021

Lopez-Chavarrias V.

The problem of antimicrobial resistance in zoonotic bacteria such as thermophilic Campylobacter could be aggravated by the simultaneous presentation of resistant phenotypes to multiple antimicrobial families, such as aminoglycosides (gentamicin and streptomycin) and macrolides (erythromycin), the drugs of choice for the treatment of clinical campylobacteriosis. This study evaluated the association of phenotypic resistance between these two antimicrobial families in thermophilic Campylobacter recovered from four livestock species in Spain, and assessed it against a corresponding genetic/genomic analysis.
Data were collected via the Spanish AMR monitoring network (VAV network) from 2002 to 2018, consisting of approx. 11,000 faecal samples from broilers, turkeys, pigs and cattle. Phenotypic AMR was assessed using the microdilution method against tetracycline, nalidixic acid, ciprofloxacin, aminoglycosides (gentamicin, streptomycin) and macrolides (erythromycin). Proportions, trends in AMR and co-resistance, and minimum inhibitory concentrations (MICs) for the different host and years were initially explored with descriptive statistics, and a subset of 168 isolates was further characterized by sequencing the SVR flaA gene, to evaluate the presence of variability as well as the existence of clusters based on resistotype. A Neighbor-Joining phylogenetic tree was constructed to assess the genetic relatedness of isolates with different resistotypes across hosts for C. coli and C. jejuni, and this was compared with an MCA analysis of the ‘relative synonymous codon usage’ (RSCU) to translate/codify the flaA gene in the different isolates. These results were compared with the presence of resistance markers against both antimicrobial classes in 51 out of 168 isolates, obtained by whole genome sequencing.
Individual proportions of resistance across hosts and bacterial species varied widely and more isolates were resistant to multiple antibiotics in C. coli than in C. jejuni. MIC distribution comparisons revealed significant host-specific differences only for erythromycin in C. jejuni (p=0.032). However, there was consistent association between the simultaneous presentation of phenotypic AMR to aminoglycosides and macrolides in all hosts, and the flaA gene analysis showed clustering of isolates sharing resistotype and to a lesser degree bacterial species and host. Several resistance markers associated with resistance to aminoglycosides and macrolides were found among the sequenced isolates.
The study is currently focused on identifying all genetic markers involved in resistance to both antimicrobial classes, and in particular, on those suggesting combined resistance phenomena, such as resistance clusters and multidrug resistance genomic islands. We will also search and identify the possible persistence of certain strains over time, and the bacteria/host pair combination that most likely may harbour the above mentioned resistance/co-resistance phenomena.
Additional whole genome sequencing was carried out for that purpose – we have access to 179 sequences in total (79 C. coli y 100 C. jejuni) from broilers, turkeys, pigs, cattle, wild boars and partridges – and the preliminary results of the study will be shown. The future plan is to complement this work with information obtained from clinical samples from humans hospitalized with campylobacteriosis in Spain, and compare our study with the situation in other European countries. Finally, a phylogenetic/evolution study will be performed with the resistance markers found.
ANNEX: A brief summary of a study based on resistance genes to betalactamase enzymes in E. coli currently carried out within the ZTA group will also be presented

	Centro de Vigilancia Sanitaria Veterinaria (VISAVET). Universidad Complutense (UCM).

Epidemiology of antimicrobial resistance to aminoglycosides and macrolides in thermophilic Campylobacter in livestock and wild animals in Spain

Link to Seminars VISAVET 2021