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Irish veterinary journal2015; 68; 23; doi: 10.1186/s13620-015-0051-4

Minimum inhibitory concentrations of erythromycin and rifampin for Rhodococcus equi during the years 2007-2014.

Abstract: Rhodococcus equi is a gram positive, intracellular pathogen of foals worldwide. The aim of this study was to determine whether there was an increasing resistance occurring in Rhodococcus equi towards the antibiotics rifampin and erythromycin over a seven year period. The investigation was carried out with the use of E test strips (epsilometers) for rifampin and erythromycin in order to determine the Minimum Inhibitory Concentrations (MIC) values of Rhodococcus equi to these antibiotics. Results: The main results of this study found that the mean MICs were higher for erythromycin than for rifampin for every year analysed apart from 2008. The results highlight that 75 % (6/8) of the mean MICs for erythromycin were above the threshold of susceptibility of 0.5 μg/ml and one of the yearly mean MICs for rifampin (2008) was above the level of ≤ 1 μg/ml. Two soil samples analysed had high MIC values of 2 μg/ml and 3 μg/ml for rifampin and erythromycin respectively. These samples can be said to have acquired resistance as they are above 1 μg/ml. Conclusions: The significance of these findings is that R. equi is already a problematic pathogen to treat and if the bacteria keeps gaining resistance to these antibiotics at rate that has been shown over the last decade, then a new form of treatment will have to be introduced. Further research into the genomics of Rhodococcus equi will, in time, shed more light on possible alternatives such as vaccines or new, more effective antimicrobials.
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Publication Date: 2015-10-06 PubMed ID: 26445669PubMed Central: PMC4594895DOI: 10.1186/s13620-015-0051-4Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research examines the increasing resistance of Rhodococcus equi, a globally prevalent infection in foals, to antibiotics rifampin and erythromycin over seven years. The results indicate a significant rise in the bacteria’s resistance to these drugs, suggesting the need for research into new treatments.

Study Aim and Methodology

  • The purpose of this study was to investigate whether the Rhodococcus equi bacteria, responsible for causing infections in foals, is growing increasingly resistant to common antibiotics erythromycin and rifampin over a period of seven years (2007-2014).
  • For scientifically assessing this possible resistance, the researchers employed a tool called E test strips (epsilometers). These strips are employed to figure out the Minimum Inhibitory Concentrations (MIC) – the lowest concentration of an antimicrobial agent that prevents visible growth of a microorganism.

Major Findings

  • Throughout nearly every year analyzed, the median MICs for erythromycin were higher than those for rifampin, except in 2008. Which suggests that Rhodococcus equi may have a higher resistance to erythromycin.
  • 75% of the mean MICs for erythromycin surpassed the susceptibility threshold of 0.5 μg/ml, indicating a significant level of resistance. Moreover, the mean MIC for rifampin in 2008 was also high, going above the tolerance level of ≤ 1 μg/ml.
  • Two examined soil samples had high MIC values (2 μg/ml for rifampin and 3 μg/ml for erythromycin), indicating acquired resistance as these values are above 1 μg/ml.

Study Implications and Conclusion

  • The findings are concerning since Rhodococcus equi is already a difficult-to-treat pathogen. If the bacteria’s resistance to erythromycin and rifampin continues to increase at the rate identified in this study, the development of alternative treatment strategies will become a necessity.
  • The researchers propose that further investigation into the genomics of Rhodococcus equi could provide insight into potential alternatives, such as new vaccines or more effective antimicrobials.

Cite This Article

APA
Fenton CS, Buckley TC. (2015). Minimum inhibitory concentrations of erythromycin and rifampin for Rhodococcus equi during the years 2007-2014. Ir Vet J, 68, 23. https://doi.org/10.1186/s13620-015-0051-4

Publication

Irish veterinary journal
ISSN: 0368-0762
NlmUniqueID: 0100762
Country: Ireland
Language: English
Volume: 68
Pages: 23
PII: 23

Researcher Affiliations

Fenton, Caitriona S
  • University College Dublin, Belfield, Dublin, Ireland.
Buckley, Thomas C
  • Irish Equine Centre, Johnstown, Naas, Co. Kildare Ireland.

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Citations

This article has been cited 4 times.
  1. Zúñiga MP, Badillo E, Abalos P, Valencia ED, Marín P, Escudero E, Galecio JS. Antimicrobial susceptibility of Rhodococcus equi strains isolated from foals in Chile.. World J Microbiol Biotechnol 2023 Jun 22;39(9):231.
    doi: 10.1007/s11274-023-03677-2pubmed: 37347336google scholar: lookup
  2. Swanner KD, Patel R, Nguyen TT, Patel FN, Magadia R, Rifai AO, Davenport M. A Rare Presentation of Rhodococcus Equi Bacteremia as a Result of Right Upper Arm Cellulitis: A Case Report and Literature Review.. Cureus 2023 Apr;15(4):e38295.
    doi: 10.7759/cureus.38295pubmed: 37255906google scholar: lookup
  3. Gray AD, Bernhardt E. Are nitrogen and carbon cycle processes impacted by common stream antibiotics? A comparative assessment of single vs. mixture exposures.. PLoS One 2022;17(1):e0261714.
    doi: 10.1371/journal.pone.0261714pubmed: 34986185google scholar: lookup
  4. Ruocco NA 3rd, Luedke LK, Fortier LA, Ducharme NG, Reesink HL. Rhodococcus equi Joint Sepsis and Osteomyelitis Is Associated With a Grave Prognosis in Foals.. Front Vet Sci 2019;6:503.
    doi: 10.3389/fvets.2019.00503pubmed: 31993449google scholar: lookup
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