Genotypes and virulence factors in Staphylococcus aureus isolated from dairy cows with subclinical mastitis in Serbia

Slobodan Vujinović; Hans Ulrich Graber; Ivan Vićić; Branislav Vejnović; Oliver Stevanović; Dejan Krnjaić; Dušan Milivojević; Vera Katić

doi:10.1016/j.cimid.2023.102056

Genotypes and virulence factors in Staphylococcus aureus isolated from dairy cows with subclinical mastitis in Serbia

Comp Immunol Microbiol Infect Dis. 2023 Oct:101:102056. doi: 10.1016/j.cimid.2023.102056. Epub 2023 Sep 4.

Authors

Slobodan Vujinović¹, Hans Ulrich Graber², Ivan Vićić³, Branislav Vejnović⁴, Oliver Stevanović⁵, Dejan Krnjaić⁴, Dušan Milivojević⁶, Vera Katić⁴

Affiliations

¹ Veterinary Specialized Institute "Šabac", Vojvode Putnika 54, 15000 Šabac, Serbia.
² Agroscope, Research Division, Food Microbial Systems, Schwarzenburgstrasse 161, 3003 Bern, Switzerland.
³ University of Belgrade, Faculty of Veterinary Medicine, Bulevar oslobodjenja 18, 11000 Belgrade, Serbia. Electronic address: ivan.vicic@online.vet.bg.ac.rs.
⁴ University of Belgrade, Faculty of Veterinary Medicine, Bulevar oslobodjenja 18, 11000 Belgrade, Serbia.
⁵ PI Veterinary Institute Dr Vaso Butozan Banja Luka, Branka Radicevića 18, 78000 Banja Luka, Republic of Srpska, Bosnia and Herzegovina.
⁶ Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444a, 11000 Belgrade, Serbia.

PMID: 37678080
DOI: 10.1016/j.cimid.2023.102056

Abstract

This study aimed to determine the prevalence of Staphylococcus aureus subclinical mastitis and to genotype the S. aureus isolates using the 16S-23S rRNA intergenic spacer (RS-PCR) method. In addition, the genes responsible for adherence, biofilm formation, host evasion, tissue necrosis, methicillin resistance, and enterotoxin production of S. aureus were investigated. The overall prevalence of S. aureus subclinical mastitis in lactating cows was 5.4% (95% confidence interval, CI=4.7-6.1%). An increased risk of S. aureus intramammary infection was observed on small family farms (odds ratio, OR=4.2, 95% CI=2.6-6.6, P < 0.001) and medium-sized farms (OR=3.5, 95% CI=2.2-5.7, P < 0.001). The RS-PCR analysis revealed 44 genotypes and genotype variants, of which 15 new genotypes and five new variants were detected within small and medium-sized farms. S. aureus isolates of new genotypes and genotype variants carried the clfA gene responsible for adherence at a lower frequency (64.8%) and enterotoxin-producing genes sea (20.4%), seb (14.8%) and sec (14.8%) at a higher frequency than the other known genotypes (P < 0.001), and were confirmed to carry the sej and sep genes. The spa gene was detected in all S. aureus isolates, whereas none harbored bap, ser, or tsst-1 genes. Methicillin-resistant strains of S. aureus (MRSA) were also detected, with a higher prevalence (19.2%) on large farms with more than 50 cows (P < 0.001). Using molecular techniques as diagnostic tools provides a better understanding of intramammary staphylococcal infections' occurrence, spread, and eradication.

Keywords: Dairy cows; Genotyping; MRSA; Subclinical mastitis.