Genetic Complexity of CC5 Staphylococcus aureus Isolates Associated with Sternal Bursitis in Chickens: Antimicrobial Resistance, Virulence, Plasmids, and Biofilm Formation

Abstract

Sternal bursitis, a common inflammatory condition in poultry, poses significant challenges to both animal welfare and public health. This study aimed to investigate the prevalence, antimicrobial resistance, and genetic characteristics of Staphylococcus aureus isolates associated with sternal bursitis in chickens. Ninety-eight samples were collected from affected chickens, and 24 S. aureus isolates were identified. Antimicrobial susceptibility testing revealed resistance to multiple agents, with a notable prevalence of aminoglycoside resistance genes. Whole genome sequencing elucidated the genetic diversity and virulence profiles of the isolates, highlighting the predominance of clonal complex 5 (CC5) strains. Additionally, biofilm formation assays demonstrated moderate biofilm production capacity among the isolates. These findings underscore the importance of vigilant monitoring and targeted interventions to mitigate the impact of sternal bursitis in poultry production systems.

Keywords: CC5; Staphylococcus aureus; antimicrobial resistance; breast blisters; genetic lineages; poultry; sternal bursitis.

Figure 1

Phylogenetic tree showing 24 S. aureus isolates analyzed via NGS, showcasing MLST, spa-type, resistance gene, and virulence factors profiles. The unrooted maximum likelihood tree, ordered and constructed using RAxML, was generated based on ‘Core Genome SNPs. Filled squares indicate the presence of the corresponding gene, while empty squares indicate the absence of the gene.

Figure 2

Percentage of biofilm formation of 24 S. aureus strains isolated from chicken bursitis. Data are presented as mean ± standard deviation for seven independent replicates. To standardize the results, biofilm formation of each isolate was normalized based on the results obtained from the positive control strain ATCC^® 25923.