First record of methicillin-resistant Staphylococcus aureus (MRSA) isolated from the Meia Ponte River and effluent in Brazil: an analysis of 1198 isolates

Objective

This study aimed to detect environmental reservoirs of multidrug-resistant Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) in Central Brazil.

Methods

Membrane filtration with growth on Baird-Parker agar base was used to recover S. aureus and MRSA from the effluents of a sewage treatment plant (STP) and surface water from an important Cerrado river. Effluent samples were collected at two points in the STP (pre- and post-treatment). Surface water was collected at six points along the Meia Ponte River, from its source to the mouth. Air samples were collected at all these collection points in 2022, totaling four campaigns between the dry and rainy seasons.

Results

S. aureus was isolated at all collection points in all campaigns, totaling 87715 isolates. Of the 1198 selected isolates, 83 were cefoxitin (FOX)-resistant, indicating a methicillin-resistance phenotype. The antimicrobial profiles of the 83 FOX-resistant isolates were investigated, and 88 % could be considered multidrug-resistant S. aureus. Of the 83 FOX-resistant isolates, more than 70 % were resistant to clindamycin, erythromycin, and rifampicin. The presence of the mecA gene was confirmed in 18 isolates collected along the Meia Ponte River and inside the STP, with 15 exhibiting multidrug-resistant phenotypes. The results of the principal component analysis (PCA) revealed an association between S. aureus isolates and the urbanized environment/STP, as well as the presence of antimicrobials.

Conclusion

This study is a pioneer in identifying the presence of MRSA in Brazilian water bodies, highlighting the urgent need for monitoring antimicrobial resistance in urban rivers.