Bacteriophages from Australian horse farms targeting
            Rhodococcus equi

: Rhodococcus equi is a facultative intracellular pathogen that causes infections in foals and many other animals such as pigs, cattle, sheep, and goats. Antibiotic resistance is rapidly rising in horse farms, which makes ineffective current antibiotic treatments based on a combination of macrolides and rifampicin. Therefore, new therapeutic strategies are urgently needed to treat R. equi infections caused by antimicrobial resistant strains. Here, we employed a R. equi mycoredoxin-null mutant strain highly susceptible to oxidative stress to screen for novel ROS-generating antibiotics. Then, we used the well-characterized Mrx1-roGFP2 biosensor to confirm the redox stress generated by the most promising antimicrobial agents identified in our screening. Our results suggest that different combinations of antibacterial compounds that elicit oxidative stress are promising anti-infective strategies against R. equi. In particular, the combination of macrolides with ROS-generating antimicrobial compounds such as norfloxacin act synergistically to produce a potent antibacterial effect against R. equi. Therefore, our screening approach could be applied to identify novel ROS-inspired therapeutic strategies against intracellular pathogens.

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Epidemiologic study of results of pulsed-field gel electrophoresis of isolates of Rhodococcus equi obtained from horses and horse farms

American Journal of Veterinary Research ◽

10.2460/ajvr.2003.64.153 ◽

2003 ◽

Vol 64 (2) ◽

pp. 153-161 ◽

Cited By ~ 23

Author(s):

Noah D. Cohen ◽

Karen E. Smith ◽

Thomas A. Ficht ◽

Shinji Takai ◽

Melissa C. Libal ◽

...

Keyword(s):

Gel Electrophoresis ◽

Epidemiologic Study ◽

Rhodococcus Equi ◽

Pulsed Field Gel Electrophoresis ◽

Pulsed Field ◽

Horse Farms

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Associations between the Ecology of Virulent Rhodococcus equi and the Epidemiology of R. equi Pneumonia on Australian Thoroughbred Farms

Applied and Environmental Microbiology ◽

10.1128/aem.00495-06 ◽

2006 ◽

Vol 72 (9) ◽

pp. 6152-6160 ◽

Cited By ~ 44

Author(s):

G. Muscatello ◽

G. A. Anderson ◽

J. R. Gilkerson ◽

G. F. Browning

Keyword(s):

Model Building ◽

Management Strategies ◽

Rhodococcus Equi ◽

Soil Conditions ◽

Virulent Strains ◽

Environmental Management Strategies ◽

Horse Farms ◽

Breeding Farms ◽

Breeding Seasons ◽

The Impact

ABSTRACT The ecology of virulent strains of Rhodococcus equi on horse farms is likely to influence the prevalence and severity of R. equi pneumonia in foals. This study examined the association between the ecology of virulent R. equi and the epidemiology of R. equi pneumonia by collecting air and soil samples over two breeding seasons (28 farm-year combinations) on Thoroughbred breeding farms with different reported prevalences of R. equi pneumonia. Colony blotting and DNA hybridization were used to detect and measure concentrations of virulent R. equi. The prevalence of R. equi pneumonia was associated with the airborne burden of virulent R. equi (both the concentration and the proportion of R. equi bacteria that were virulent) but was not associated with the burden of virulent R. equi in the soil. Univariable screening and multivariable model building were used to evaluate the effect of environmental and management factors on virulent R. equi burdens. Lower soil moisture concentrations and lower pasture heights were significantly associated with elevated airborne concentrations of virulent R. equi, as were the holding pens and lanes, which typically were sandy, dry, and devoid of pasture cover. Few variables appeared to influence concentrations of virulent R. equi in soil. Acidic soil conditions may have contributed to an elevated proportion of virulent strains within the R. equi population. Environmental management strategies that aim to reduce the level of exposure of susceptible foals to airborne virulent R. equi are most likely to reduce the impact of R. equi pneumonia on endemically affected farms.

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