Currently, we are facing the ever-increasing phenomenon of bacteria being resistant to antibiotics. It is the consequence of excessive and incorrect use of drugs. The phenomenon is a global problem affecting bacteria both in their hospital population and in the natural environment. Municipal waste is an environment conducive to the development of microorganisms, therefore it contains various groups of bacteria, including drug-resistant staphylococci. The aim of the study was to identify species of bacteria, determine their antibiotic resistance, and assess the occurrence of genes responsible for methicillin resistance in Staphylococcus aureus isolated from mixed municipal waste. Strains were isolated by Koch’s serial dilution method with the use of microbiological media. Species were identified using the MALDI TOF-MS technique, whereas the drug resistance profile was determined by disk diffusion and molecular PCR methods. 250 isolates of S. aureus were collected. The highest resistance found was to cefoxitin, erythromycin and tetracycline. Among the bacteria collected, resistance to 1, 2, 3 or 4 antibiotics at the same time was the most common, with a maximum of 10. Additionally, 45 (18%) MDR (multidrug-resistant) isolates were detected. Methicillin resistance was found by the disk diffusion test in 60 (24%) strains, while the mecA gene was detected in as many as 180 (72%) isolates.

Staphylococcus pseudintermedius (SP) and methicillin-resistant SP (MRSP) is one of the most important veterinary pathogens in the dog. Herein, from a total of 126 S. pseudintermedius strains, 23 MRSP (18%) were identified. Multi-Locus Sequence Typing (MLST) revealed that most of MRSP strains belonged to ST71 (26%), which have been already reported in Italy and other countries. Interestingly, nine new sequence types (39%), from 1053 up to 1061, were described for the first time. Moreover, the isolated MRSP strains showed relevant antibiotic resistance profiles. This report highlights the circulation of new sequence types of MRSP in Italy and underlines the need of a global epidemiological surveillance to limit the increasing spread of multidrug-resistant MRSP strains worldwide, since they may represent a considerable concern for dog’s health.