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Genotypic characteristics and phylogenetic tree analysis of Staphylococcus aureus isolates from sheep subclinical

Alaa Shamil Alalaf¹, Ayman Hani Taha², Omar Hashim Sheet²

¹Department of Animal Production, College of Agriculture and Forestry, University of Mosul, Mosul, Iraq.

Open Veterinary Journal

|March 17, 2025

Abstract

Background:

Staphylococcus aureus describes the greatest common cause of mastitis in sheep; however, little information was available concerning methicillin-resistant S. aureus (MRSA) in the milk of mastitis sheep.

Aim:

The current study aimed to find exactly the incidence of S. aureus and MRSA in milk samples from sheep farmhouses in Mosul city, in addition to discovering specific genes that encode virulence factors.

Methods:

Samples of 60 sheep's subclinical milk were gathered between October 2023 and February 2024 from various places around the Nineveh governorate. Standard methods that include selective media and biochemical testing were utilized in the current study. Furthermore, the nuc, mecA, clfA, clfB, and coa genes in S. aureus were determined utilizing a polymerase chain reaction technique.

Results:

According to our findings, S. aureus was found in sheep subclinical mastitis at a rate of 23.3% (14/60) in sheep milk. Furthermore, all S. aureus isolates 100% appeared to carrying of the nuc, mecA, clfA, and coa genes, while 92.9% of isolates were positive for the clfB gene. The gene profiles of S. aureus isolates were divided into two primary categories. Based on the clfA, clfB, and coa genes, nine unique strains of S. aureus sequences were submitted to the NCBI GenBank. The phylogenetic tree analysis of all study isolates demonstrated its identity to various strains in the NCBI-BLAST.

Conclusion:

The incidence of S. aureus infections emphasized the presence of an issue in husbandry practices, insufficient adherence to basic hygiene protocols, and the random use of antibiotics.

Insights

Methicillin-resistant Staphylococcus aureus (MRSA) was detected in 23.3% of sheep milk samples. All identified S. aureus strains carried virulence genes, highlighting potential risks in sheep husbandry and hygiene.

Area of Science:

Veterinary Microbiology
Food Safety
Bacterial Pathogenesis

Background:

Staphylococcus aureus is the primary cause of ovine mastitis.
Limited data exists on methicillin-resistant S. aureus (MRSA) in mastitic sheep milk.

Purpose of the Study:

Determine the incidence of S. aureus and MRSA in sheep milk from Mosul city.
Identify genes encoding virulence factors in S. aureus isolates.

Main Methods:

Collected 60 subclinical sheep milk samples (Oct 2023 - Feb 2024).
Used standard microbiological techniques and PCR to detect nuc, mecA, clfA, clfB, and coa genes.

Main Results:

S. aureus detected in 23.3% (14/60) of samples.
All S. aureus isolates (100%) carried nuc, mecA, clfA, and coa genes; 92.9% carried clfB.
Nine S. aureus strains were sequenced and submitted to GenBank, showing identity to existing strains via BLAST analysis.

Conclusions:

High prevalence of S. aureus and associated virulence genes indicates significant mastitis issue.
Findings suggest problems with sheep husbandry, hygiene, and antibiotic use.

Read full analysis

Keywords:

Phylogenetic analysis tree S. aureus Sheep milk Virulence factors

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