[Antimicrobial susceptibility in isolates of Streptococcus equi subsp. equi from Buenos Aires province, Argentina].

The research article analyses the susceptibility of Streptococcus equi subsp. equi, the bacteria causing an equine disease called strangles, to different antibiotics in Buenos Aires, Argentina. It confirms the effective use of penicillin, while also identifying resistant strains to specific antibiotics.

Objective and Methodology of the Study

• The primary objective of the study was to investigate the antimicrobial susceptibility profile of Streptococcus equi subsp. equi, a bacterial pathogen responsible for a horse disease known as strangles, prevalent in Buenos Aires, Argentina.
• The researchers conducted the experiment on ninety-two isolates of the bacteria by using the single disk method with various antibiotics such as penicillin (PEN), cefotaxime, erythromycin (ERY), tetracycline, enrofloxacin (ENR), trimethoprim sulfamethoxazole (TMS), ciprofloxacin, clindamycin (CLI), streptomycin (STR), and florfenicol.
• They also performed tests to determine the Minimum Inhibitory Concentration (MIC), a measure of the minimum amount of an antibiotic needed to inhibit bacterial growth, for penicillin and those antibiotics to which the bacteria showed resistance or intermediate susceptibility.

Results of the Study

• The researchers found high rates of susceptibility through the disk diffusion method, which is a simple test to measure the efficacy of antibiotics against bacteria.
• The MIC values for penicillin, TMS, and CLI were below the breakpoint values, indicating that these antibiotics are effective against the Streptococcus equi subsp. equi bacteria.
• However, they also identified resistant strains to ENR and STR, with their MIC ranges lying above the breakpoint values. This reveals the presences of some isolates that would not respond to treatment with these particular antibiotics.
• Contrary to general expectations about penicillin resistance, they found no resistant strains in Buenos Aires, suggesting penicillin can still be used as an effective therapy there.

Conclusions and Recommendations

• The authors recommend the rational and judicious use of antibiotics. Although penicillin is confirmed to be effective, its indiscriminate use, or the use of any other antibiotic without testing for resistance, could lead to the development of resistant strains, recurrence of the infection, or chronicity.
• The research also emphasizes the need for continuous monitoring of the antimicrobial susceptibility profiles in the region to control antibiotic resistance effectively.