Abstract
Background:
Staphylococcus aureus (S. aureus) is a major pathogenic bacterium in veterinary medicine and human health. It is one of the most important bacterial agents causing urinary tract infection (UTI). The increasing incidence of multidrug-resistant and biofilm-forming S. aureus is a great problem today.

Aim:
The aim of study was conducted to investigate the phenotypic and genotypic aspects of biofilm formation in MDR S. aureus isolated from UTI infection in human and cattle in Babylon, Iraq.

Methods:
A total of 168 and 172 urine samples were collected from UTI infection in humans and cattle, respectively, during the period from November 2023 to February 2024. Morphological and biochemical identification was used to diagnose S. aureus. Additional confirmation was performed by the automated Vitek 2 compact system.

Results:
Among the 168 human isolates, 24 (14.2%) and 172 cattle isolates , 16 (9.3%) isolates were diagnosed as S. aureus. Genotypically identification of the isolates was performed using the 16s RNA gene. Twenty-two (91.6%) from 24 human source S. aureus isolates and 8 (50%) from 16 animals source S. aureus isolates were found to be MDR according to the Vitek 2 compact system. Results revealed that 19 (86.3%) and 7(87.5%) MDR isolates were phenotypically positive for biofilm production in concern to human and animal source isolates ,respectively. Genotypically, three polysaccharide intracellular adhesion (PIA) genes and one MSCRAMMs (fib) were screened in MDR bacteria using specific primers. The prevalence rate of genes was icaA (100%), icaB (100%), and icaC (100%) in all 30 MDR isolates . fib gene were present in 63.6% of human isolates and 75% of cattle source isolates.

Conclusion:
The study has shown that the biofilm-forming S. aureus that cause UTI were resistant to multiple antibiotic agents. These findings underscore the necessity of development an effective treatment approaches to control UTI infections in humans and animals.

Key words: Staphylococcus aureus, Vitek II, Biofilm genes, UTI infections