Occurrence and Phenotypic Characteristics of Methicillin-Resistant Staphylococcus aureus (MRSA) in Emergency Medical Service Ambulances as a Potential Threat to Medical Staff and Patients

Abstract

Introduction: An ambulance used by an emergency medical service team is the workplace of specialised medical personnel, providing daily transportation for patients in life-threatening conditions, from all walks of life, with numerous diseases and injuries. MRSA (methicillin-resistant Staphylococcus aureus) strains are classified as Gram-positive cocci, characterised primarily by their multidrug resistance. Infections caused by S. aureus have a low treatment success rate and are associated with persistent carrier state. This study aimed to isolate MRSA and MSSA (methicillin-sensitive Staphylococcus aureus) in the emergency vehicle and determine drug resistance of these isolates. Materials and Methods: This study involved an ambulance vehicle operated in central Poland. A total of 39 swabs were taken and evaluated from inside the ambulance on permanent duty. The isolates were analysed using catalase and coagulase assays, Gram staining, culturing on Chapman medium, growth evaluation on agar with 5% sheep blood, and assessing the strains’ sensitivities to selected antibiotics. Material was collected from 13 designated points located in the medical compartment and driver’s cabin. Results: S. aureus bacteria were detected in 51.28% of the samples, 40% of which were MRSA strains. Despite the application of high disinfection standards for the interior of the ambulance, it was not possible to kill all S. aureus strains, which may be because the pathogens in question produce a biofilm that effectively allows them to survive on various surfaces, including those disinfected. Almost 100% of the MRSA isolates were resistant to antibiotics from the β-lactam group (penicillin, ticarcillin, cefotaxime, and cefoxitin), the macrolide group (erythromycin) and the lincosamide group (clindamycin). However, only a few MRSA strains proved resistant to streptomycin (12.5%) and ciprofloxacin (37.5%). β-lactam antibiotics, such as cefotaxime (100% resistant strains) and penicillin (58% resistant strains), were also ineffective against MSSA. Although MSSA isolates showed slight resistance to ticarcillin and erythromycin (33.3%) and clindamycin (25%), the remaining antibiotics proved effective (no resistant strains). Conclusions: Among the isolated strains, the greatest resistance to β-lactam antibiotics and erythromycin was observed. Multidrug-resistant strains of S. aureus were found in the emergency medical system. Even the MSSA strains detected in the studied ambulance showed resistance to some of the antibiotics used. The prevalence of S. aureus strains within ambulances indicates the need for a high hygiene level in daily prehospital work with patients.