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Microorganisms
Volume 13
Issue 12
10.3390/microorganisms13122756
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Article

Quantification of Total Staphylococci and Escherichia coli in Milk and Dairy Products from Small Ruminants and Characterization of the Antimicrobial Resistance Profiles of Isolated Pathogenic Strains

by
Sergiu Condor
1,
Mihaela Duma
2,
Smaranda Crăciun
1,
Marian Mihaiu
1,
Raluca Cîmpean
1,
Oana Lucia Crisan-Reget
1,
Sorin Daniel Dan
1,
Laura Condor
3,
Claudiu-Nicusor Ionica
1 and
Alexandra Tabaran
1,*
1
Department of Animal Breeding and Food Safety, Faculty of Veterinary Medicine, University of Agriculture Sciences and Veterinary Medicine of Cluj-Napoca, 400684 Cluj-Napoca, Cluj County, Romania
2
National Sanitary Veterinary and Food Safety Authority, 400621 Cluj-Napoca, Cluj County, Romania
3
National Sanitary Veterinary and Food Safety Authority, 510216 Alba-Iulia, Alba County, Romania
*
Author to whom correspondence should be addressed.
Microorganisms 2025, 13(12), 2756; https://doi.org/10.3390/microorganisms13122756
Submission received: 27 October 2025 / Revised: 20 November 2025 / Accepted: 21 November 2025 / Published: 4 December 2025
(This article belongs to the Special Issue Antimicrobial Resistance: Genetic Mechanisms, Emerging Trends, and Pathogen Risks in Food Safety)
Versions Notes

Abstract

This study evaluated the microbiological quality, presence of virulence genes, and antimicrobial resistance of Staphylococcus aureus and Escherichia coli in sheep and goat milk and traditional Romanian dairy products (Telemea and Burduf cheeses). Raw milk contained high levels of coagulase-positive staphylococci (CPS; 5.2 log CFU/mL) and E. coli (4.3 log CFU/mL), with several samples exceeding legal limits. Sour cream exhibited moderate CPS (1.2–1.9 log CFU/g) and E. coli (0.4–3.12 log CFU/g) counts, with occasional non-compliance. Cheeses had low CPS (0.52–0.84 log CFU/g) and E. coli (0.37–0.89 log CFU/g) levels, all within permissible limits. Molecular analysis detected the nuc gene in 21 sheep milk samples, of which 85.7% also carried the sea gene and 14.3% carried seb. Additionally, two goat milk samples tested positive for both nuc and sea. Three Telemea cheese samples were also sea-positive. Among raw milk samples, 10 E. coli isolates carried stx1, and two additionally harbored hly, while dairy products were negative for E. coli virulence genes. Antimicrobial susceptibility testing showed high resistance of S. aureus to penicillin (90.5%) and ampicillin (85.7%), with multidrug resistance among sea- and seb-positive isolates. STEC isolates showed resistance to ampicillin (70%), tetracycline (50%), and trimethoprim–sulfamethoxazole (40%), but remained susceptible to amoxicillin–clavulanic acid.
Keywords: Staphylococcus aureus; Escherichia coli; dairy products; antimicrobial resistance; virulence genes Staphylococcus aureus; Escherichia coli; dairy products; antimicrobial resistance; virulence genes

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MDPI and ACS Style

Condor, S.; Duma, M.; Crăciun, S.; Mihaiu, M.; Cîmpean, R.; Crisan-Reget, O.L.; Dan, S.D.; Condor, L.; Ionica, C.-N.; Tabaran, A. Quantification of Total Staphylococci and Escherichia coli in Milk and Dairy Products from Small Ruminants and Characterization of the Antimicrobial Resistance Profiles of Isolated Pathogenic Strains. Microorganisms 2025, 13, 2756. https://doi.org/10.3390/microorganisms13122756

AMA Style

Condor S, Duma M, Crăciun S, Mihaiu M, Cîmpean R, Crisan-Reget OL, Dan SD, Condor L, Ionica C-N, Tabaran A. Quantification of Total Staphylococci and Escherichia coli in Milk and Dairy Products from Small Ruminants and Characterization of the Antimicrobial Resistance Profiles of Isolated Pathogenic Strains. Microorganisms. 2025; 13(12):2756. https://doi.org/10.3390/microorganisms13122756

Chicago/Turabian Style

Condor, Sergiu, Mihaela Duma, Smaranda Crăciun, Marian Mihaiu, Raluca Cîmpean, Oana Lucia Crisan-Reget, Sorin Daniel Dan, Laura Condor, Claudiu-Nicusor Ionica, and Alexandra Tabaran. 2025. "Quantification of Total Staphylococci and Escherichia coli in Milk and Dairy Products from Small Ruminants and Characterization of the Antimicrobial Resistance Profiles of Isolated Pathogenic Strains" Microorganisms 13, no. 12: 2756. https://doi.org/10.3390/microorganisms13122756

APA Style

Condor, S., Duma, M., Crăciun, S., Mihaiu, M., Cîmpean, R., Crisan-Reget, O. L., Dan, S. D., Condor, L., Ionica, C.-N., & Tabaran, A. (2025). Quantification of Total Staphylococci and Escherichia coli in Milk and Dairy Products from Small Ruminants and Characterization of the Antimicrobial Resistance Profiles of Isolated Pathogenic Strains. Microorganisms, 13(12), 2756. https://doi.org/10.3390/microorganisms13122756

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