Epidemiological multilevel surveillance of methicillin-resistant staphylococci in a veterinary teaching hospital and first characterization of Staphylococcus pseudintermedius isolates using IR biotyper®

In a global view on Antimicrobial Resistance (AMR), Methicillin-resistant Staphylococci (MRS) are one of the most threatening pathogens in both human and veterinary medicine. The aim of this work was to assess the impact of MRS within a Small Animal Veterinary Teaching Hospital (VTH) in Italy, through a multilevel data collection on clinical, commensal and environmental isolates and a subsequent analysis through Fourier-transform infrared (FTIR) spectroscopy by IR Biotyper®. From December 2020 to May 2023, a total of 81/239 (33.9%) MRS clinical isolates was recorded, mainly MR S. pseudintermedius (MRSP, 66/81, 81.5%). High resistance rates towards most of the antimicrobials tested were observed, such as 97.5% (79/81) for tetracycline and 84% (68/81) for enrofloxacin. MRS prevalence in hospitalized patients’ oral flora was 22% (33/150) at admission, while in-hospital acquisition was 19.7% (23/117). The environmental analysis showed a high frequency of MRS detection in the Intensive Care Unit area (10/34, 29.4%), and in the personnel’ shoe soles (6/7, 85.7%) and the floor (5/7, 71.4%). In both patients’ flora and environment, the most common species were MRSP and MR Staphylococcus haemolyticus. Strain typing using IR Biotyper® on 96 selected isolated showed the presence of three main clusters, one of them detected at all levels (infected patients, patients’ commensal flora and environment), suggesting its endemic presence within the hospital. These findings confirm the importance of MRS in small animal practice, highlighting as a multilevel surveillance program can consent to achieve an exhaustive overview that could help in the development of tailored measures of infection control. • Methicillin-resistant Staphylococci (MRS) are one of the most concerning Antimicrobial Resistant (AMR) bacteria in both human and veterinary medicine. • In this multilevel surveillance study on an Italian Small Animal Veterinary Teaching Hospital, we highlighted as Methicillin-Resistan Staphylococcus pseudintermedius (MRSP) made up 81.5% of methicillin-resistant clinical isolates from infected dogs and cats, with 43% of all S. pseudintermedius isolates. • MRS isolates showed often a multi-drug resistance pattern, especially to penicillin, tetracycline, and enrofloxacin. • In the environment, MRS were found in high prevalence in the Intensive Care Unit (29.4%) , floor (71.4%) , and shoe soles (85.7%) indicating widespread contamination. • In patients’ oral flora, we found as 22% of patients carried MRS at admission ; 19.7% acquired it during hospitalization. Risk factors included recent hospitalization/surgery, dog species, and length of hospital stay. • FTIR analysis, used for the first time to characterize S.pseudintermedius isolates, revealed the presence of a persistent MRSP clone across clinical, commensal, and environmental samples, suggesting a likely endemic clone circulating within the hospital. • Multilevel surveillance, including clinical, commensal, and environmental monitoring, supports tailored infection control in veterinary hospitals.