Monitoring of Drug-Resistance Rates Among <i>Staphylococcus</i><i>aureus</i> and <i>Enterococcus</i><i>faecalis</i> Isolates from Hospital Wastewaters in a Northern Province of Iran

Background: Hospital wastewater is one of the most dangerous and important sources of the spread of opportunistic bacteria. It is also one of the main causes of multidrug-resistant (MDR) hospital infections. Objectives: Considering the importance of investigating such environmental contaminants, this study was conducted to determine the frequency and phenotypes of antibiotic resistance among two important Gram-positive pathogens isolated from hospital wastewater. Methods: Enterococcus faecalis and Staphylococcus aureus isolates were identified from 42 samples obtained from 14 hospital wastewaters using filtration methods, microbiological tests, and polymerase chain reaction (PCR) with a specific ddlE primer and the VITEK-2 card system. The antibiotic resistance patterns were investigated using the Kirby-Bauer test according to CLSI-2021 guidelines regarding antibiotic classes. Results: Enterococcus faecalis was identified as the most frequent (n = 65; 30.37%) Gram-positive isolate. The highest resistance and susceptibility rates among these isolates were related to cotrimoxazole (SXT) (84.62%) and linezolid (LZ) (90.77%), respectively. In addition, the highest resistance and susceptibility rates among S. aureus isolates were related to penicillin (P) (78.95%) and LZ (87.72%), respectively. The frequency of extensively drug-resistant (XDR) E. faecalis isolates was two times higher than that of S. aureus isolates (P = 0.01). Conclusions: The results of this study confirm the high prevalence of antibiotic-resistant E. faecalis and S. aureus in hospital wastewaters. Therefore, eliminating these environmental pollutants requires continuous and simultaneous monitoring of environmental and clinical samples while considering the issue of antibiotic resistance. Moreover, appropriate control measures should be taken to prevent the spread of linezolid-resistant isolates in antibiotic therapy.