Occurrence and Characteristics of Staphylococcus aureus Strains along the Production Chain of Raw Milk Cheeses in Poland

Abstract

Cheeses produced from unpasteurized milk by traditional production methods may contain many groups of microorganisms, including Staphylococcus aureus. The aim of this study was to determine the occurrence of S. aureus in the artisanal cheese production chain from unpasteurized milk. We investigated the prevalence of S. aureus strains isolated from various stages of artisanal cheese of unpasteurized milk production from farms in the northeastern and southern parts of Poland and characterized them. Characterization included antimicrobial susceptibility by microbroth dilution and biofilm formation by in vitro assay. Among all strains, the presence of enterotoxigenic genes and genes involved with biofilm formation and antibiotic resistance were screened by PCR-based methods. A total of 180 samples were examined. A high percentage of strains were resistant to penicillin (54/58.1%) and tobramycin (32/34.4%). Some tested isolates also showed resistance to the macrolide class of antibiotics: azithromycin, clarithromycin, and erythromycin at 17/18.3%, 15/16.1%, and 21/22.6%, respectively. Among tested isolates, we also found phenotypic resistance to oxacillin (9/9.7%) and cefoxitin (12/12.9%). The blaZ gene encoding penicillin resistance was the most common gene encoding antibiotic resistance among the tested strains. All isolates showing phenotypic resistance to cefoxitin possessed the mecA gene. The study also evaluated the prevalence of biofilm-associated genes, with eno the most frequently associated gene. Eighty-nine out of 93 S. aureus isolates (95.7%) possessed at least one enterotoxin-encoding gene. The results of this study showed that production of raw milk cheeses may be a source of antibiotic resistance and virulent S. aureus. Our results suggest that artisanal cheese producers should better control production hygiene.

In Vitro Antimicrobial Activity of Thymus vulgaris, Origanum vulgare, Satureja montana and Their Mixture against Clinical Isolates Responsible for Canine Otitis Externa

“…Resistance to methicillin and other antimicrobials are a spread threat with severe implications on animal and human health [ 23 ]. The tested staphylococcal isolates were resistant to several antibiotics and most of them were resistant to ampicillin (81.81%) and tobramycin (68.18%) in accordance with other surveys [ 23 , 24 , 25 , 26 , 27 , 28 ].…”

Prevalence and Antibiotic Resistance of Bacillus sp. Isolated from Raw Milk

“…The study showed that a high percentage (40/90 (40.11%)) of the tested isolates were multidrug resistant (resistant to at minimum three antibiotics from different chemical classes of antibiotic), with 100% of isolates having a MAR index >0.20. MAR index values higher than 0.2 suggest a high level of antibiotic resistance among strains isolated from milk [18,33]. Nevertheless, it is worthy of attention that in our study, 77.50% (31/40) of the multidrug-resistant Bacillus strains were from the B. cereus group.…”

“…The multiple antibiotic resistance (MAR) index was calculated for each isolate as: number of antibiotics to which the isolate is resistant/total number of antibiotics against which the isolate was tested [18,33]. In this study, we defined multidrug resistance (MDR) as resistance to at least one antibiotic from three or more classes of antibiotics [33].…”

Recent Trends of Antibiotic Resistance in Staphylococcus aureus Causing Clinical Mastitis in Dairy Herds in Abruzzo and Molise Regions, Italy

“…The classes of β-lactams and fluoroquinolones prevailed among the antibiotics prescribed by veterinarians, and this could explain the high prevalence of strains harboring bla Z genes and the increase in norfloxacin MIC values in 2022. In investigations carried out in different countries, the bla Z gene was found at high frequencies as well, with a maximum of 95.7% [ 20 ]. The increase in norfloxacin MIC values could be indicative of an increase in resistance to quinolones that in S. aureus is mediated by the core gene nor A, encoding different variants of an efflux pump, as well as other efflux systems [ 14 ].…”