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Journal of clinical microbiology2009; 47(3); 734-737; doi: 10.1128/JCM.01395-08

Detection of virulent Rhodococcus equi in exhaled air samples from naturally infected foals.

Abstract: Virulent Rhodococcus equi causes pyogranulomatous bronchopneumonia in foals. The route of infection of foals has been considered to be inhalation of aerosolized bacteria from soil that is contaminated with equine feces. Thus, disease caused by R. equi has been regarded as an opportunistic infection of environmental origin and not a contagious disease. In this study, we report the exhalation of virulent R. equi from the respiratory tract of naturally infected foals. A handheld air-monitoring system was used to recover virulent R. equi from the exhaled breath of foals, and the concentration of virulent R. equi organisms in exhaled air was compared to the concentration in environmental air samples taken from the holding pens and lane areas on farms. R. equi strains carrying the vapA gene of the virulence plasmid were detected by using colony blotting and DNA hybridization techniques in cultures of exhaled air from 67% (37/55) of foals tested. The concentration of virulent R. equi organisms in exhaled air from foals was significantly higher than that in environmental air (P<0.001). There were no significant differences in the median concentrations of virulent R. equi bacteria exhaled by clinically healthy or diseased foals. The high concentrations of virulent R. equi bacteria in exhaled air suggested that aerosol transmission between foals is possible and may have a significant impact on the prevalence of R. equi pneumonia on farms. The air sampling technique described is potentially useful as a noninvasive method for the detection and quantification of virulent R. equi in the respiratory tract of foals.
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Publication Date: 2009-01-14 PubMed ID: 19144811PubMed Central: PMC2650914DOI: 10.1128/JCM.01395-08Google 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.

This research article suggests that foals (young horses) infected with the virulent Rhodococcus equi, a bacteria that causes a specific type of pneumonia, may release the bacteria into the air when they exhale. The researchers found concentrations of these bacteria to be higher in exhaled air compared to environmental air, implying that it’s possible for the bacteria to spread via aerosols from one foal to another.

Introduction to Rhodococcus equi

  • Virulent Rhodococcus equi is a type of bacteria known to cause pyogranulomatous bronchopneumonia in foals, which is a serious pulmonary disease.
  • Traditionally, it has been thought that foals contract the bacteria by inhaling it from soil contaminated with equine feces, as R. equi is generally considered an infection of environmental origin and not a contagious disease.

Study Objectives and Methods

  • The researchers in this study aim to examine if virulent R. equi might also be spreading via a different route – through the air exhaled by infected foals.
  • They used a handheld air-monitoring system to collect air samples exhaled by the foals and measure the concentration of R. equi bacteria. This method also helped isolate strains of R. equi carrying the vapA gene, a key marker of the bacterium’s virulence or ability to cause disease.
  • The study conducted tests on air samples from 55 foals and compared the bacterial concentration in the foals’ exhaled air with that in the environmental air samples taken from their holding areas.

Study Findings

  • They found that R. equi was detected in cultures of exhaled air from 67% of the foals tested. This means that a significant majority of foals were exhaling the bacteria.
  • Interestingly, the concentration of R. equi bacteria found in the exhaled air was significantly higher than the concentration in environmental air samples.
  • No significant difference was observed in the concentrations of exhaled bacteria between healthy foals and ones already exhibiting symptoms of the disease caused by R. equi.

Implications and Conclusions

  • The high concentrations of the bacteria in exhaled air suggest that aerosol transmission (spreading by air droplets) of the bacteria between foals could be a significant method of disease spread, affecting the overall disease prevalence on farms.
  • The researchers propose the air sampling technique as a useful noninvasive method to detect and quantify R. equi in the respiratory tracts of foals, helping to monitor and prevent the potential spread of the disease.

Cite This Article

APA
Muscatello G, Gilkerson JR, Browning GF. (2009). Detection of virulent Rhodococcus equi in exhaled air samples from naturally infected foals. J Clin Microbiol, 47(3), 734-737. https://doi.org/10.1128/JCM.01395-08

Publication

Journal of clinical microbiology
ISSN: 1098-660X
NlmUniqueID: 7505564
Country: United States
Language: English
Volume: 47
Issue: 3
Pages: 734-737

Researcher Affiliations

Muscatello, G
  • Equine Infectious Disease Laboratory, School of Veterinary Science, The University of Melbourne, Parkville, Victoria 3010, Australia.
Gilkerson, J R
    Browning, G F

      MeSH Terms

      • Actinomycetales Infections / microbiology
      • Actinomycetales Infections / veterinary
      • Air Microbiology
      • Animals
      • Bacterial Proteins / genetics
      • Breath Tests / methods
      • DNA, Bacterial / genetics
      • Disease Transmission, Infectious
      • Exhalation
      • Horse Diseases / microbiology
      • Horses
      • Nucleic Acid Hybridization
      • Plasmids
      • Rhodococcus equi / isolation & purification
      • Virulence Factors / genetics

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