Antimicrobial susceptibilities of Staphylococcus aureus isolated from animal and human sources in Brazil.

This research article investigates the susceptibility of different Staphylococcus aureus strains, isolated from humans and animals in Brazil, to seven distinct antibiotics. The findings show that the strains derived from human infections had a broader resistance to antibiotics compared to strains from animal infections and healthy human carriers.

Methodology

• The research was based on the analysis of 760 Staphylococcus aureus strains. These strains were isolated from different sources, with 400 derived from animal infections, 300 from human infections, and 60 from healthy human carriers.
• The susceptibilities of these strains to seven antibiotics were studied using an agar dilution technique.

Findings and Comparisons

• The primary finding of this research study is that the Staphylococcus aureus strains from human infections were significantly more resistant to a broader spectrum of antibiotics. This contrasts with the strains originating from animal infections and healthy human carriers, which exhibited lower resistance.
• Such a discovery suggests a higher evolution and adaptability of the Staphylococcus aureus bacteria in human hosts, allowing them to withstand a more extensive range of antibiotic treatments. The lower resistance shown by the bacteria isolated from animal infections indicates less exposure or adaptability to antibiotics in these hosts.

Most Active Drugs

• Among the seven antibiotics used in this study, Amikacin and Gentamicin were the most active drugs against all groups of strains. These antibiotics demonstrated high effectiveness irrespective of the source of the Staphylococcus aureus strains—be it human infections, animal infections, or healthy human carriers.
• The effectiveness of these two drugs signifies their potential use in treating infections caused by various Staphylococcus aureus strains. However, it should also be noted that continuous monitoring of their efficacy is necessary, given the bacteria’s high adaptability and potential evolution to develop resistance over time.