Virulence type and tissue tropism of Staphylococcus strains originating from Hungarian rabbit farms

Genomic Analysis of Staphylococcus aureus Strains Originating from Hungarian Rabbit Farms Reinforce the Clonal Origin of Various Virulence Types

Simple Summary

Staphylococcosis is a major disease in both human and veterinary medicine. In commercial rabbit production, highly virulent variants cause significant economic losses. This study describes the comparative analysis of the whole genome of 51 strains sequenced by our group, and 12 sequences derived from online repositories. The investigation was based on whole-genome sequencing and whole-genome multilocus sequence typing. The typical highly virulent strains showed great similarity with ST121/t645 isolates from Italy, Spain and the UK. The most prevalent genotype in Hungary was an atypical highly virulent variant; these strains form a novel sequence type (ST5993), and belong to three different spa types (t4770, t711 and t2407). Low virulence (LV) strains grouped into two main clusters, two ST1 LV strains formed a separate cluster from the majority forming a clone-like group, despite the five different multilocus sequence typing (MLST) patterns and seven different spa types. Some strains in this survey showed genetic polymorphism on more than 50% of the examined loci, however, even within the same MLST ST group, hundreds of loci showed polymorphism, which could facilitate the very fine differentiation of the strains.

Abstract

Staphylococcosis is one of the most important infectious diseases in rabbit medicine, especially in commercial farming. Previous studies revealed the existence of virulent variants adapted to rabbits. Typical and atypical, highly virulent as well as low virulent variants have been isolated and reported from industrial units in all major rabbit-meat-producing countries. Preceding the research focused on detecting defined nucleotide sequences, the genome of these organisms as a whole was rarely subjected to scientific investigations. The authors sequenced 51 Staphylococcus strains originating from industrial rabbit farms in Hungary. Another 12 draft genomes of rabbit isolates were constructed from read sequences available in digital repositories, and were compared based on whole-genome multilocus sequence typing. The clonal origin of highly virulent variants is confirmed, the strains from Hungary were closely related with the strains isolated in the UK, Italy, and Spain. Atypical highly virulent strains are the most prevalent in Hungary, they form a separate clonal cluster. The low virulent strains were genetically similar, but more heterogeneous than the highly virulent (HV) and aHV strains even by the traditional MLST typing scheme. Other “non-aureus” Staphylococcus species were also identified.

Mastitis on Rabbit Farms: Prevalence and Risk Factors

In this cross-sectional study, prevalence of clinical mastitis (PCM) and farm-specific risk factors were determined on 531 doe rabbit farms in Spain and Portugal, from January 2001 through March 2017. The information was obtained by carrying out 2367 visits and doing physical examinations of 144,455 lactating does, sorted in 2635 cohorts. Overall mean PCM was 4.05% (CI95% [3.87⁻4.22]), (minimum to maximum: 0⁻36.00% PCM). This study suggests that PCM was influenced by the variable number of batches (a batch was a group of does served the same day), per maternity barn (p < 0.0001). The duo system (does being moved to clean disinfected barns for parturition), was also an enabling risk factor for CM. The day of service or lactation stage also affected PCM. Lastly, there was an effect of the breeds or lines (p < 0.0001); mean PCM ranged between 1.29% and 7.09%. A subset of data obtained from 200 farms visited during January 2012⁻March 2017, was recorded to describe the use of antimicrobials against mastitis. Changes in host, husbandry, environment, and biosecurity practices, are highlighted to provide health and welfare benefits for breeding rabbits.

Draft Genome Sequence of an Atypical Highly Virulent Rabbit Staphylococcus aureus Strain

Rabbit staphylococcosis is one of the most important diseases in industrial rabbit production. We report here the draft genome sequence of Staphylococcus aureus strain 380/11, an atypical highly virulent (aHV) rabbit Staphylococcus aureus strain.