Rhodococcus equi Pathogenesis and Infection Management

Rhodococcus equi is a Gram‐positive, facultative intracellular pathogen that predominantly causes severe bronchopneumonia in foals and opportunistic infections in immunocompromised humans. The bacterium survives and multiplies within alveolar macrophages by deploying a virulence plasmid encoding Vap proteins that neutralise phagosomal acidification and subvert host immune responses. Clinically, disease ranges from subclinical pulmonary lesions to overt dyspnoea, fever and abscess formation. Diagnosis relies on a combination of thoracic ultrasonography, radiography and microbiological culture, while management centres on long‐term administration of rifampicin combined with a macrolide antibiotic. Emerging resistance to these first‐line agents has prompted investigation of alternative antimicrobials, optimisation of dosing to achieve therapeutic concentrations in pulmonary epithelial lining fluid and exploration of novel vaccine candidates. Infection prevention on breeding farms emphasises early detection of subclinical cases by ultrasonography and judicious use of antimicrobial prophylaxis to limit the development of multidrug resistance. Recent advances in genomic and immunological studies have deepened understanding of plasmid‐borne pathogenicity islands and host immunity, paving the way for next‐generation vaccines and precision therapy.

Research from Nature Portfolio

Longitudinal ultrasonographic studies have characterised the natural history of rhodococcal pulmonary lesions in preweaned foals, revealing that subclinical lung abscesses are common and often precede overt clinical signs. Quantitative assessment of abscess diameter and pleural irregularities has identified threshold lesion sizes predictive of subsequent respiratory distress, informing more targeted diagnostic protocols. Separately, environmental and microbiome analyses have demonstrated that routine prophylactic administration of macrolide–rifampicin combinations to subclinically affected foals significantly disrupts gut microbial diversity and selects for multidrug‐resistant R. equi strains. This work underscores the ecological impact of widespread antimicrobial use and supports the adoption of alternative therapies and refined treatment guidelines to preserve drug efficacy.

Rhodococcus equi Pathogenesis and Infection Management publication trend

The graph below shows the total number of articles in rhodococcus equi pathogenesis and infection management across all publications each year (not limited to Nature Index journals).

Technical terms

Alveolar macrophage: A lung‐resident immune cell that internalises and attempts to destroy inhaled pathogens.

Virulence plasmid: An extrachromosomal DNA element encoding factors essential for bacterial survival and replication within host cells.

Minimum inhibitory concentration (MIC): The lowest antibiotic concentration that prevents visible bacterial growth in vitro.

Pathogenicity island: A genomic region acquired by horizontal gene transfer that contains clusters of virulence‐associated genes.

Prophylaxis: Preventative treatment administered to avert the onset of disease.

References

1. Comparative bactericidal activity of four macrolides alone and combined with rifampicin or doxycycline against Rhodococcus equi at concentrations achievable in foals. Frontiers in Pharmacology (2024).
2. Exploring the Accessory Genome of Multidrug-Resistant Rhodococcus equi Clone 2287. Antibiotics (2023).
3. Evaluation of vaccine candidates against Rhodococcus equi in BALB/c mice infection model: cellular and humoral immune responses. BMC Microbiology (2024).
4. Investigation of the relationship between pulmonary lesions based on lung ultrasound and respiratory clinical signs in foals with suspected pulmonary rhodococcosis. Scientific Reports (2023).
5. Differential Effects of Rhodococcus equi Virulence-Associated Proteins on Macrophages and Artificial Lipid Membranes. Microbiology Spectrum (2023).
6. Comparative Genomics of Rhodococcus equi Virulence Plasmids Indicates Host-Driven Evolution of the vap Pathogenicity Island. Genome Biology and Evolution (2017).
7. A Common Practice of Widespread Antimicrobial Use in Horse Production Promotes Multi-Drug Resistance. Scientific Reports (2020).