AUTHOR=Moawad Amira A. , El-Adawy Hosny , Linde Jörg , Jost Ines , Tanja Gärtner , Katja Hruschka , Karsten Donat , Neubauer Heinrich , Monecke Stefan , Tomaso Herbert 

TITLE=Whole genome sequence-based analysis of Staphylococcus aureus isolated from bovine mastitis in Thuringia, Germany

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1216850

DOI=10.3389/fmicb.2023.1216850

ISSN=1664-302X

ABSTRACT=<sec id="sec1"><title>Background</title><p>Bovine mastitis is a common disease of dairy cattle causing major economic losses due to reduced yield and poor quality of milk worldwide. The current investigation aimed to gain insight into the genetic diversity, antimicrobial resistance profiles and virulence associated factors of <italic>Staphylococcus</italic> (<italic>S.</italic>) <italic>aureus</italic> isolated from clinical bovine mastitis in dairy farms in Thuringia, Germany.</p></sec><sec id="sec2"><title>Methods</title><p>Forty <italic>Staphylococcus aureus</italic> isolates collected from clinical bovine mastitis cases from 17 Thuringian dairy farms were phenotyped and genetically characterized using whole genome sequencing.</p></sec><sec id="sec3"><title>Results</title><p>Out of 40 <italic>S. aureus</italic>, 30 (75%) were confirmed as methicillin resistant isolates. The isolates showed elevated antimicrobial resistance against penicillin, tetracycline and oxacillin, i.e., 77.5, 77.5, and 75%, respectively. Lower resistance rates were found against moxifloxacin, ciprofloxacin, gentamicin and trimethoprim/sulfamethoxazole, i.e., 35, 35, 30, and 22.5%, respectively. While resistance against clindamycin and erythromycin was rarely found (5 and 2.5%, respectively). All isolates were susceptible to linezolid, teicoplanin, vancomycin, tigecycline, fosfomycin, fusidic acid and rifampicin. These isolates were further allocated into five different sequence types: ST398 (<italic>n</italic> = 31), ST1074 (<italic>n</italic> = 4), ST504 (<italic>n</italic> = 3), ST582 (CC15) (<italic>n</italic> = 1) and ST479 (<italic>n</italic> = 1). These isolates were also assigned to seven clusters with up to 100 SNP which has facilitated geographical mapping and epidemiological distribution in Thuringia. Strains belonging to ST398 were classified into clusters 1, 2, 3, 4 and 7. The isolates of ST504 were of cluster 5, those of ST1074 were belonging to cluster 6. Resistance genes <italic>bla</italic>Z, <italic>bla</italic>I and <italic>bla</italic>R associated with penicillin resistance were found in 32 (80%) strains, all except one were belonging to ST398. Methicillin resistance associated <italic>mec</italic>A was identified in 30 (96.8%) isolates of ST398. All tetracycline and erythromycin resistant isolates were of ST398, and all harbored both <italic>tet</italic>M and <italic>erm</italic>A. About 90.3% of tetracycline resistant isolates assigned to ST398 were also carrying <italic>tet</italic>K gene. The point mutations <italic>par</italic>C_S80F, <italic>gyr</italic>A_S84L and <italic>par</italic>C_S80Y in <italic>gyr</italic>A and <italic>par</italic>C associated with quinolone resistance were found in all phenotypically resistant isolates to ciprofloxacin and moxifloxacin (<italic>n</italic> = 14). Sixty-eight virulence genes were identified among isolates. Both <italic>luk</italic>D/E and <italic>lukM</italic>/F-PV-P83 were identified in 22.5% of isolates, all were non-ST398.</p></sec><sec id="sec4"><title>Conclusion</title><p>In this study, ST398 had the highest potential to cause disease and had a massive prevalence in bovine mastitis cases. Five different sequence types and seven clusters were identified in the federal state of Thuringia. The circulation of some clusters in the same region over several years shows the persistence of cluster-associated infection despite the intensive veterinary care. On the other hand, some regions had different clusters at the same year or in different consecutive years. Different sequence types and associated different clusters of <italic>S. aureus</italic> were geographically widely distributed among dairy farms in Thuringia. The findings of this study show that various clusters have the potential to spread over a large geographical scale. The detection of LA-MRSA on dairy farms, which is known for cabapility to widely spread among different groups of animals, humans and their environment urges for the implementation of national wide strategic programs. The identification of CA-MRSA among the isolates such as ST398 poses a significant risk for the transmission of such strains between animals and humans on dairy farms.</p></sec>