Rhodococcus equi is a bacterial pathogen that primarily affects foals, leading to pneumonia and other systemic infections. It is a significant concern in equine health due to its impact on the respiratory system of young horses. The bacterium is found in soil and can be inhaled by foals, leading to infection. Clinical signs of Rhodococcus equi infection in foals include coughing, fever, and respiratory distress. Diagnosis is typically confirmed through bacterial culture or polymerase chain reaction (PCR) testing. Management of the disease involves antimicrobial therapy and supportive care. This page compiles peer-reviewed research studies and scholarly articles that explore the pathogenesis, diagnosis, treatment, and prevention of Rhodococcus equi infections in horses.
Huber L, Giguère S, Slovis NM, Carter CN, Barr BS, Cohen ND, Elam J, Erol E, Locke SJ, Phillips ED, Smith JL.The objective of this study was to determine the prevalence of strains resistant to macrolides and rifampin over time in clinical samples from foals submitted to diagnostic laboratories in central Kentucky. We performed a retrospective observational study of all clinical samples from foals that were submitted to veterinary diagnostic laboratories in Kentucky between January 1995 and December 2017. Samples were included if the bacterium was cultured and tested for susceptibility to erythromycin or rifampin. susceptibility testing to erythromycin was available for 2,169 isolates of , while s...
Coleman MC, Blodgett GP, Bevevino KE, Ivanek R, Cummings KJ, Carter GK, Cohen ND.The occurrence of Rhodococcus equi at farms varies, with disease occurring endemically at some farms, but only sporadically, or not at all at other farms. Only some foals residing on endemic farms develop clinical signs of disease. Limited evidence is available regarding foal-level risk factors for the development of R. equi pneumonia. The purpose of this study was to identify foal-level risk factors associated with the development of R. equi pneumonia among foals at a large breeding farm in Texas with a recurrent problem of R. equi pneumonia. A retrospective cohort study was conducted usin...
Willingham-Lane JM, Coulson GB, Hondalus MK.Rhodococcus equi is a facultative intracellular bacterium of macrophages and is an important pathogen of animals and immunocompromised people wherein disease results in abcessation of the lungs and other sites. Prior work has shown that the presence of the major virulence determinant, VapA, encoded on the pVAPA-type plasmid, disrupts normal phagosome development and is essential for bacterial replication within macrophages. pVAPA- type plasmids are typical of R. equi strains derived from foals while strains from pigs carry plasmids of the pVAPB-type, lacking vapA, and those from humans harbor ...
Kalinowski M, Grądzki Z, Jarosz Ł, Adaszek Ł.Rhodococcus equi (R. hoagii) is an opportunistic pathogen commonly found in foals up to 6 months old and animal environment. The R. equi genome contains genetically stable chromosomal DNA and an 80-90 kb plasmid containing vapA gene, responsible for virulence. Most reports from around the world focus on the determination of R. equi plasmid profiles. Few studies have attempted to determine differences in nucleotide sequences between virulent strains of R. equi isolated from foals and breeding environment. The aim of the study was to perform a molecular analysis of a fragment of the chromosomal ...
Huber L, Giguère S, Berghaus LJ, Hanafi A, Ryan C.Rhodococcus equi, a soil saprophyte, is a common cause of pneumonia in foals and a frequent opportunistic pathogen in immunosuppressed people. Because it is widespread in the environment, R. equi can be detected in the feces of most horses. However, the exact timing and rate of shedding relative to infection is unknown. The objectives of this study were to quantify shedding of R. equi in mares and foals after experimental infection of foals with 2 different inocula and to determine the effect of composting on concentrations of R. equi in contaminated bedding. Foals were infected intratracheall...
Cywes-Bentley C, Rocha JN, Bordin AI, Vinacur M, Rehman S, Zaidi TS, Meyer M, Anthony S, Lambert M, Vlock DR, Giguère S, Cohen ND, Pier GB.Immune correlates of protection against intracellular bacterial pathogens are largely thought to be cell-mediated, although a reasonable amount of data supports a role for antibody-mediated protection. To define a role for antibody-mediated immunity against an intracellular pathogen, Rhodococcus equi, that causes granulomatous pneumonia in horse foals, we devised and tested an experimental system relying solely on antibody-mediated protection against this host-specific etiologic agent. Immunity was induced by vaccinating pregnant mares 6 and 3 weeks prior to predicted parturition with a conjug...
Vanniasinkam T, Barton MD, Das TP, Heuzenroeder MW.This chapter describes a strategy for mapping linear B-cell epitopes of proteins using synthetic biotinylated peptides in an ELISA.A set of overlapping peptides were designed based upon a known amino acid sequence of the target protein, VapA (Virulence-associated Protein A) of the bacterium Rhodococcus equi, an important pulmonary pathogen in foals. The peptides synthesized as biotinylated peptides were coated directly onto micro titer plates which had been pre-coated with NeutrAvidin™ and used to screen sera from foals confirmed to have R. equi disease. A linear B-cell epitope was identifie...
Huber L, Giguère S, Berghaus LJ, Hanafi A, Vitosh-Sillman S, Czerwinski SL.Rhodococcus equi is one of the most important causes of disease in foals. Infection is typically characterized by pyogranulomatous pneumonia although extrapulmonary infections occur occasionally. Uveitis and polysynovitis have been reported in foals naturally infected with R. equi and are thought to be the result of an immune-mediated process. However, the pathogenesis of these conditions is poorly understood. The objectives of this study were to document the occurrence of uveitis and polysynovitis after experimental infection with R. equi and to determine if these disorders are the direct res...
Gressler LT, Machado G, da Silveira BP, Cohen ND, Corbellini LG, Leotti VB, Diehl GN, Dos Santos LC, de Vargas AC.Rhodococcus equi is an important cause of foal pneumonia. While its isolation from different sources has been widely evaluated, there is a need to better understand the R. equi epidemiology from samples of the nasal cavity of healthy horses. Objective: To determine the prevalence of R. equi from the nasal cavity of healthy horses, along with its virulence profile, antimicrobial susceptibility and environmental variables associated. Methods: Cross-sectional study. Methods: Swabs from the nasal cavity of 1010 apparently healthy horses from 341 farms were submitted for bacteriological analyses. T...
Berlin S, Wallstabe S, Scheuch E, Oswald S, Hasan M, Wegner D, Grube M, Venner M, Ullrich A, Siegmund W.Standard treatment of foals with severe abscessing lung infection caused by Rhodococcus equi using rifampicin and a macrolide antibiotic can be compromised by extensive inhibition and/or induction of drug metabolising enzymes (e.g. CYP3A4) and transport proteins (e.g. P-glycoprotein), as has been shown for rifampicin and clarithromycin. The combination of rifampicin with the new, poorly metabolised gamithromycin, a long-acting analogue of azithromycin and tulathromycin with lower pharmacokinetic interaction potential, might be a suitable alternative. Objective: To evaluate the pharmacokinetic ...
Berghaus LJ, Giguère S, Bordin AI, Cohen ND.Rhodococcus equi is a common cause of pneumonia in foals and an opportunistic pathogen in immunosuppressed people. The ability of R. equi to survive and replicate in macrophages is the basis of its pathogenicity. Limited knowledge about the role of cytokines in host defense against R. equi comes from studies in mice and the role of cytokines in intracellular survival of R. equi in equine macrophages is unknown. The objectives of this study were to determine the effect of priming with interferon (IFN)-γ, interleukin (IL)-1β, IL-4, IL-6, IL-10, or tumor necrosis factor (TNF)-α at various conc...
Giguère S, Berghaus LJ, Willingham-Lane JM.Pneumonia caused by remains an important cause of disease and death in foals. The combination of a macrolide (erythromycin, azithromycin, or clarithromycin) with rifampin has been the recommended treatment for foals with clinical signs of infection caused by since the early 1980s with, until recently, only rare reports of resistance. Resistance to macrolides and rifampin in isolates of cultured from horses is increasing, with isolates resistant to all macrolides and rifampin now being cultured from up to 40% of infected foals at some farms. This text reviews the available data regarding ant...
Duquesne F, Houssin E, Sévin C, Duytschaever L, Tapprest J, Fretin D, Hébert L, Laugier C, Petry S.Rhodococcus equi causes pulmonary and extrapulmonary infections in animals and humans, with endemic situations and significant young foal mortality in stud farms worldwide. Despite its economic impact in the horse-breeding industry, the broad geographic and host distribution, global diversity and population structure of R. equi remain poorly characterised. In this context, we developed a multilocus sequence typing (MLST) scheme using 89 clinical and environmental R. equi of various origins and eight Rhodococcus sp. Data can be accessed at http://pubmlst.org/rhodococcus/. A clonal R. equi popul...
Tirosh-Levy S, Gürbilek SE, Tel OY, Keskin O, Steinman A.Rhodococcus equi is a common cause of pneumonia in foals and has extensive clinical, economic and possibly zoonotic consequences. This bacterium survives well in the environment and may be considered as normal flora of adult horses. Certain strains of this bacterium are extremely virulent in foals, and early identification and intervention is crucial for prognosis. Rhodococcus equi is endemic in many parts of the world and occasionally isolated in Israel. This study was designed to evaluate R. equi seroprevalence in adult horses in Israel to indirectly indicate the potential level of exposure ...
Adler DMT, Damborg P, Verwilghen DR.Lameness is the most commonly reported health problem in horses, and lameness investigations which include local anaesthetic injections are routinely performed by equine practitioners. Through this process, bacteria can enter the tissues perforated by the needle and may cause local infections at the injection site. The objective of this in vitro study was to investigate if local anaesthetics at concentrations available in commercially available solutions could inhibit growth and/or kill bacteria that could be inoculated into the synovial space or soft tissues during injection. This study evalu...
Rutenberg D, Venner M, Giguère S.There is conflicting data regarding the efficacy of tulathromycin for the treatment of foals with bronchopneumonia. Tulathromycin is effective for the treatment of bronchopneumonia in foals and noninferior to the combination of azithromycin and rifampin. A total of 240 foals on a farm endemic for infections caused by Rhodococcus equi. In a controlled, randomized, and double-blinded clinical trial, foals with ultrasonographic pulmonary lesions (abscess score 10-15 cm) were allocated to 3 groups: 1-tulathromycin IM q 7 days (n = 80); 2-azithromycin-rifampin, orally q24h (n = 80); or 3-untreated ...
Stieler Stewart AL, Sanchez LC, Mallicote MF, Muniz AL, Westerterp MS, Burrow JA, MacKAY RJ.Erythromycin (ERY) induces anhidrosis in foals. Azithromycin (AZI) and clarithromycin (CLA), often combined with rifampicin (RIF), are commonly used to treat Rhodococcus equi infections, but effects on sweating have not been investigated. Objective: To determine the effects of AZI, CLA and RIF on sweat responses in normal foals. Methods: Each experiment was a blinded, duplicated, six foal × three period counterbalanced within subjects design (12 foals/experiment). Methods: Antimicrobials were given orally for 5 days. In Experiment 1, ERY, AZI and CLA were given. In Experiment 2, ERY, RIF and ...
Berlin S, Randow T, Scheuch E, Grube M, Venner M, Siegmund W.The long-acting azalide antibiotic gamithromycin is marketed for intramuscular treatment of bovine and swine infections. Off-label use in foals leads to severe local lesions likely caused by hyperosmolality of the injected solution. We provide evidence from a pharmacokinetic study in 10 warm-blooded healthy foals for intravenous bolus injection of gamithromycin diluted in distilled water to be a safe and well tolerated alternative. By intravenous dosing, markedly higher plasma exposure and better penetration into bronchoalveolar lavage cells but lower distribution into epithelial lining fluid ...
Berlin S, Kirschbaum A, Spieckermann L, Oswald S, Keiser M, Grube M, Venner M, Siegmund W.The treatment of equine lung infections by Rhodococcus equi with rifampicin is empirically based because pharmacokinetic/pharmacodynamic (PK/PD) indices and pivotal clinical outcome data are not available. Objective: To evaluate the pharmacokinetics and pulmonary distribution of rifampicin into epithelial lining fluid (ELF) and bronchoalveolar lavage cells (BALC) to predict antimicrobial activity in the lung using PK/PD indices. Methods: Controlled, randomised, two-period, crossover, repeated-dose study with an initial arm to measure disposition after i.v. administration of rifampicin. Methods...
Barceló Oliver F, Russell TM, Uprichard KL, Neil KM, Pollock PJ.To describe the clinical signs, surgical treatment, and outcome of septic arthritis of the coxofemoral joint in foals. Methods: Retrospective clinical study. Methods: Foals (n = 12) with confirmed sepsis of the coxofemoral joint. Methods: Lameness was localized to the coxofemoral joint based on physical examination. Sepsis was confirmed by cytological analysis of synovial fluid obtained under ultrasonographic guidance, during general anesthesia or standing sedation. Intra-articular analgesia was used as an adjunct diagnostic modality in 2 foals. Surgical lavage of the affected joint was pe...
Giguère S.Pneumonia caused by Rhodococcus equi remains an important cause of disease and death in foals. The combination of a macrolide (erythromycin, azithromycin, or clarithromycin) with rifampin remains the recommended therapy for foals with clinical signs of infection caused by R equi. Most foals with small, subclinical ultrasonographic pulmonary lesions associated with R equi recover without therapy, and administration of antimicrobial agents to these subclinically affected foals does not hasten lesion resolution relative to administration of a placebo. Resistance to macrolides and rifampin in isol...
Witkowski L, Rzewuska M, Takai S, Chrobak-Chmiel D, Kizerwetter-Świda M, Feret M, Gawryś M, Witkowski M, Kita J.Rhodococcus equi is one of the most significant bacterial pathogens affecting foals up to 6 months of age worldwide. Rhodococcosis is present in Poland however information about molecular characterization of R. equi isolates is scarce. This study describes molecular characterization of Rhodococcus equi infection on 13 horse breeding farms in Poland between 2001 and 2012. Samples were collected by tracheobronchial aspiration from pneumonic foals or during necropsy. The R. equi isolates were genotyped by plasmid profiling and pulsed-field gel electrophoresis. Results: Totally, 58 R. equi isolat...
Javed R, Taku AK, Sharma RK, Badroo GA.The aim was to determine the occurrence of in equines and their environment in Jammu (R.S. Pura, Katra), molecular characterization and to determine the antibiotic resistance pattern of . Methods: A total of 96 nasopharyngeal swab samples were collected from equines. The organism was isolated on Columbia nalidixic acid agar containing 5% sheep blood as well as on sheep blood agar and was later confirmed by cultural characteristics and biochemical tests. Molecular detection of isolates was done by gene amplification followed by virulence associated protein A () gene amplification. Antibiogra...
McQueen CM, Whitfield-Cargile CM, Konganti K, Blodgett GP, Dindot SV, Cohen ND.Rhodococcus equi (R. equi) is an intracellular bacterium that affects young foals and immuno-compromised individuals causing severe pneumonia. Currently, the genetic mechanisms that confer susceptibility and/or resistance to R. equi are not fully understood. Previously, using a SNP-based genome-wide association study, we identified a region on equine chromosome 26 associated with culture-confirmed clinical pneumonia. To better characterize this region and understand the function of the SNP located within TRPM2 that was associated with R. equi pneumonia, we performed RNA-Seq on 12 horses repres...
Willingham-Lane JM, Berghaus LJ, Giguère S, Hondalus MK.The soil-dwelling, saprophytic actinomycete is a multihost, facultative intracellular pathogen of macrophages. When inhaled by susceptible foals, it causes severe bronchopneumonia. It is also a pathogen of pigs, which may develop submaxillary lymphadenitis upon exposure. isolates obtained from foals and pigs possess conjugative plasmids housing a pathogenicity island (PAI) containing a novel family of genes of unknown function called the virulence-associated protein or family. The PAI regions of the equine and swine plasmids differ in gene composition, with equine isolates possessing six ...
Giguère S, Berghaus LJ, Miller CD.Despite the paucity of data available, stall-side serum amyloid (SAA) assays are commonly used to make diagnostic and treatment decisions in foals with bronchopneumonia. Objective: Measurement of SAA concentrations can accurately differentiate pneumonic from healthy foals. Methods: Fifty-four pneumonic foals between 3 weeks and 5 months of age were compared to 44 healthy controls. In addition, 47 foals on a farm endemic for R. equi infections were studied. Methods: Serum samples were collected from pneumonic foals at hospital admission. Foals were categorized as having pneumonia caused by R. e...
Perez-Ecija A, Mendoza FJ, Estepa JC, Bautista MJ, Pérez J.A 2-month-old foal with septic shock and severe respiratory distress was referred to the Veterinary Teaching Hospital. Due to poor prognosis, the foal was euthanized. Histopathology showed lesions suggestive of Rhodococcus equi infection associated with a diffuse interstitial infiltrate of foamy macrophages and syncytial cells presenting large acidophilic intranuclear inclusion bodies, fibrin exudates and hyaline membranes. Bacteriological examination from lung and respiratory exudates confirmed R. equi infection, whilst immunohistochemistry and PCR yielded a positive result for Equid herpesvi...
Kalinowski M, Grądzki Z, Jarosz Ł, Kato K, Hieda Y, Kakuda T, Takai S.Rhodococcus equi is an important bacterial pathogen in foals up to 6 months old, widespread in horse farms all over the world. It was found that only virulent R. equi strains expressing 15-17 kDa virulence-associated protein (VapA) and having large virulence plasmid of 85-90 kb containing vapA gene are pathogenic for horses. To date, 12 plasmid types have been reported in VapA positive strains from horses. There are no data concerning plasmid types of Polish field R. equi strains isolated from horses and horse farm environment. The aim of the study is to determine plasmid profiles of virulent ...
Colavita G, Amadoro C, Rossi F, Fantuz F, Salimei E.Today the interest toward horse (Equus caballus) and donkey (Equus asinus) milk for human consumption is receiving a renewed attention because of its particular composition, hypoallergenicity, and nutraceutical properties. The realistic perspective of global use of this aliment in balanced diets, especially for infancy and geriatrics, poses the need for a more in depth knowledge on milk hygiene and on the health status of dairy animals, as a prerequisite of consumers' safety. The aim of this paper was to review the available literature on the health and hygiene parameters as well as on the pot...
Chaffin MK, Cohen ND, Martens RJ.To determine the effect of azithromycin chemoprophylaxis on the cumulative incidence of pneumonia caused by Rhodococcus equi, age at onset of pneumonia, and minimum inhibitory concentration (MIC) of azithromycin for R equi isolates cultured from fecal and clinical samples. Methods: Controlled, randomized clinical trial. Methods: 338 foals born and raised at 10 equine breeding farms; each farm had a history of endemic R equi infections. Methods: Group 1 foals were control foals, and group 2 foals were treated with azithromycin (10 mg/kg [4.5 mg/lb], PO, q 48 h) during the first 2 weeks after bi...
Álvarez-Narváez S, Giguère S, Anastasi E, Hearn J, Scortti M, Vázquez-Boland JA.Antibiotic use has been linked to changes in the population structure of human pathogens and the clonal expansion of multidrug-resistant (MDR) strains among healthcare- and community-acquired infections. Here we present a compelling example in a veterinary pathogen, , the causative agent of a severe pulmonary infection affecting foals worldwide. We show that the (46) gene responsible for emerging macrolide resistance among equine isolates in the United States is part of a 6.9-kb transposable element, Tn, actively mobilized by an IS family transposase. Tn is carried on an 87-kb conjugative pla...
Duchesne R, Castagnet S, Maillard K, Petry S, Cattoir V, Giard JC, Leon A.This study aimed to analyse antimicrobial susceptibility evolution of equine pathogens isolated from clinical samples from 2006-2016. A collection of 25 813 bacterial isolates was studied, clustered according to their origins (respiratory tract, cutaneous, genital and other), and analysed for their antimicrobial susceptibility using the disk diffusion method. The most frequently isolated pathogens were group C Streptococci (27.6%), Escherichia coli (20.0%), Staphylococcus aureus (7.8%), Pseudomonas aeruginosa (4.0%), Enterobacter spp. (3.4%), Klebsiella pneumoniae (2.4%), and Rhodococcus equi ...
Hurley JR, Begg AP.A trial was conducted on a Thoroughbred stud to determine whether or not the administration of anti-Rhodococcus equi hyperimmune plasma would reduce the prevalence of R equi pneumonia (rattles) in foals born in the 1992 horse breeding season. Hyperimmune plasma was administered to 34 foals; another 57 foals were untreated. There was no significant difference in the number of transfused foals developing R equi pneumonia compared with the untreated foals. The time required for recovery from pneumonia between the 2 groups was not significantly different.
Fines M, Pronost S, Maillard K, Taouji S, Leclercq R.Treatment with a combination of erythromycin and rifampin has considerably improved survival rates of foals and immunocompromised patients suffering from severe pneumonia caused by Rhodococcus equi. Frequently, because of monotherapy, emergence of rifampin-resistant strains has been responsible for treatment failure. Using consensus oligonucleotides, we have amplified and sequenced the rifampin resistance (Rif(r))-determining regions of 12 rifampin-resistant R. equi strains isolated from three foals and of mutants selected in vitro from R. equi ATCC 3701, a rifampin-susceptible strain. The ded...
Muscatello G, Gerbaud S, Kennedy C, Gilkerson JR, Buckley T, Klay M, Leadon DP, Browning GF.Rhodococcoccus equi is a significant cause of bronchopneumonia in foals worldwide. Infection of the lungs is believed to result from inhalation of virulent R. equi in dust from contaminated environments. A measure of infectious risk in an environment is the level of airborne contamination. Objective: To assess and compare the level of airborne virulent R. equi in paddocks and stables. Methods: Air samples were collected sequentially over the 2003 foaling season from the paddocks and stables on 3 Irish horse breeding farms affected by R. equi pneumonia. Colony blotting and DNA hybridisation tec...
Cohen ND, Chaffin MK, Vandenplas ML, Edwards RF, Nevill M, Moore JN, Martens RJ.Prognosis of Rhodococcus equi pneumonia can be challenging because the course of the disease is often insidious and overt clinical signs are subtle. Early diagnosis is considered desirable because it may offer the chance of more successful implementation of treatment and, thereby, improved outcome. Serological tests have previously failed to be accurate for early detection or diagnosis. Measurement of serum amyloid A (SAA) prior to and at the time of clinical signs was therefore chosen in order to assess its potential clinical use. Objective: To determine whether SAA concentrations differentia...
Arnold-Lehna D, Venner M, Berghaus LJ, Berghaus R, Giguère S.There is a lack of data on the efficacy of treatment of Rhodococcus equi pneumonia in association with an optimised selection of foals. Objective: To evaluate whether targeted treatment protocols resulting in decreased antimicrobial use impact foal mortality rates. Methods: Retrospective study. Methods: Three hundred and thirty foals with pneumonia per year were randomly selected from 2008 to 2016. All foals were examined once weekly from birth until weaning. A physical examination of the respiratory tract, body temperature, haematology and an ultrasonographic examination of the lungs was incl...
Hooper-McGrevy KE, Wilkie BN, Prescott JF.Rhodococcus equi causes severe pyogranulomatous pneumonia in foals and in immunocompromised humans. Replication of virulent isolates within macrophages correlates with the presence of a large plasmid which encodes a family of seven virulence-associated proteins (VapA and VapC to VapH), whose functions are unknown. Although cell-mediated immunity is thought to be crucial in eliminating R. equi infection, antibody partially protects foals. The antibody response to both VapA and VapC was similar in six adult horses and six naturally exposed but healthy foals, as well as in eight foals with R. equ...
Cauchard J, Sevin C, Ballet JJ, Taouji S.The aim of this study was to evaluate serum IgG antibody levels and opsonizing activity in foals from pregnant mares immunized with either proteins from an R. equi strain containing virulence-associated protein A (VapA), an immunodominant surface-expressed lipoprotein encoded by a virulence plasmid crucial for virulence in foals, or a whole killed virulent R. equi preparation. Forty-eight pregnant mares were distributed into three groups, i.e. 24 immunized with R. equi VapA protein antigen associated with a water-based nanoparticle adjuvant (Montanide IMS 3012), 8 immunized with whole killed R...
Bordin AI, Huber L, Sanz MG, Cohen ND.Pneumonia in foals caused by the bacterium Rhodococcus equi has a worldwide distribution and is a common cause of disease and death for foals. The purpose of this narrative review was to summarise recent developments pertaining to the epidemiology, immune responses, treatment, and prevention of rhodococcal pneumonia of foals. Screening tests have been used to implement earlier detection and treatment of foals with presumed subclinical R. equi pneumonia to reduce mortality and severity of disease. Unfortunately, this practice has been linked to the emergence of antimicrobial-resistant R. equi i...
Burton AJ, Giguère S, Berghaus LJ, Hondalus MK, Arnold RD.Rhodococcus equi, a facultative intracellular pathogen and an important cause of pneumonia in foals, is highly susceptible to killing by gentamicin in vitro. However, gentamicin is not effective in vivo, due to its poor cellular penetration. Encapsulation of drugs in liposomes enhances cellular uptake. The objectives of this study were to compare liposomal gentamicin and free gentamicin with respect to their uptake by equine macrophages and intracellular colocalization with R. equi and to compare the efficacies of liposomal gentamicin, free gentamicin and clarithromycin with rifampin for the r...
Sellon DC, Besser TE, Vivrette SL, McConnico RS.Recently, a technique was described for amplification of Rhodococcus equi-specific chromosomal and vapA DNA from blood and tracheal wash fluids. It was hypothesized that this technique would be more sensitive than standard culture techniques or serology for diagnosis of R. equi pneumonia in foals. Tracheal wash fluid, nasal swabs, whole blood samples, and serum samples from 56 foals with pneumonia were analyzed. Final clinical diagnosis was determined by the attending clinician on the basis of final interpretation of all available information about each foal, including clinical presentation, d...
Berghaus LJ, Giguère S, Sturgill TL.Rhodococcus equi, a facultative intracellular pathogen of macrophages, causes life-threatening pneumonia in foals and in people with underlying immune deficiencies. As a basis for this study, we hypothesized that macrophage lineage and age would affect intracellular survival of R. equi and cytokine induction after infection. Monocyte-derived and bronchoalveolar macrophages from 10 adult horses and from 10 foals (sampled at 1-3 days, 2 weeks, 1 month, 3 months, and 5 months of age) were infected ex vivo with virulent R. equi. Intracellular R. equi were quantified and mRNA expression of IL-1β, ...
Båverud V, Franklin A, Gunnarsson A, Gustafsson A, Hellander-Edman A.In Sweden, mares sometimes develop acute, often fatal, colitis when their foals are treated orally with erythromycin and rifampicin for Rhodococcus (R.) equi infection. Clostridium (C.) difficile, or its cytotoxin, was demonstrated in faecal samples from 5 of 11 (45%) mares with diarrhoea. By contrast C. difficile was not found in the faecal flora of 12 healthy mares with foals treated for R. equi infection or in 56 healthy mares with healthy untreated foals. No other enteric pathogen was isolated from any diarrhoeic mare. Of 7 investigated treated foals, 4 had a high (1651.0, 1468.3, 273.0 an...
Rocha JN, Cohen ND, Bordin AI, Brake CN, Giguère S, Coleman MC, Alaniz RC, Lawhon SD, Mwangi W, Pillai SD.There is currently no licensed vaccine that protects foals against Rhodococcus equi-induced pneumonia. Oral administration of live, virulent R. equi to neonatal foals has been demonstrated to protect against subsequent intrabronchial challenge with virulent R. equi. Electron beam (eBeam)-inactivated R. equi are structurally intact and have been demonstrated to be immunogenic when administered orally to neonatal foals. Thus, we investigated whether eBeam inactivated R. equi could protect foals against developing pneumonia after experimental infection with live, virulent R. equi. Foals (n = 8) w...
Sangal V, Goodfellow M, Jones AL, Sutcliffe IC.Opinion 106 of the Judicial Commission has clarified the nomenclature of the taxon variously named , ' and . As a consequence, we present here the genus name and that of its nomenclatural type species, comb. nov., for valid publication and propose the reclassification of four rhodococcal species as novel combinations in the genus, namely Guo et al. 2015 comb. nov., Kämpfer . 2014 comb. nov., Li . 2015 comb. nov. and Lee . 2019 comb. nov. In addition, we note that a clinical isolate, strain 86-07 (=W8901), likely represents an additional species within the genus . Nearly a century after ...
Okoko T, Blagova EV, Whittingham JL, Dover LG, Wilkinson AJ.Virulence and host range in Rhodococcus equi depends on the variable pathogenicity island of their virulence plasmids. Notable gene products are a family of small secreted virulence-associated proteins (Vaps) that are critical to intramacrophagic proliferation. Equine-adapted strains, which cause severe pyogranulomatous pneumonia in foals, produce a cell-associated VapA that is necessary for virulence, alongside five other secreted homologues. In the absence of biochemical insight, attention has turned to the structures of these proteins to develop a functional hypothesis. Recent studies have ...
Reuss SM, Cohen ND.Bacterial pneumonia is a common cause of disease in both neonatal and weanling foals. The causal organism or organisms differ with the age of the foal, should be identified via microbiologic culture, and will ultimately dictate appropriate treatment. Initial treatment in neonates should be broad spectrum and bactericidal, whereas weanling age foals may receive more targeted treatment. The combination of a macrolide antibiotic and rifampin remains the gold standard for treatment of Rhodococcus equi pneumonia; however, resistance to these antimicrobials is a concern.
Willingham-Lane JM, Berghaus LJ, Giguère S, Hondalus MK.The soil-dwelling, saprophytic actinomycete is a multihost, facultative intracellular pathogen of macrophages. When inhaled by susceptible foals, it causes severe bronchopneumonia. It is also a pathogen of pigs, which may develop submaxillary lymphadenitis upon exposure. isolates obtained from foals and pigs possess conjugative plasmids housing a pathogenicity island (PAI) containing a novel family of genes of unknown function called the virulence-associated protein or family. The PAI regions of the equine and swine plasmids differ in gene composition, with equine isolates possessing six ...
Prescott JF, Travers M, Yager-Johnson JA.Corynebacterium equi was cultured from manure or soil on five horse-breeding farms in Ontario at monthly intervals on three occasions during the summer of 1982. The organism was widespread. Contamination by C. equi of the loafing paddock and pasture areas was significantly greater in a farm established 30 years than in two established for four and six years and there was a significant correlation between the C. equi burden in stables, paddocks and pastures and the length of use of the five farms for horses. In all farms, numbers of C. equi in pasture soil exceeded numbers in fresh manure, sugg...
Takai S, Takeda K, Nakano Y, Karasawa T, Furugoori J, Sasaki Y, Tsubaki S, Higuchi T, Anzai T, Wada R, Kamada M.To investigate the emergence of rifampin resistance in Rhodococcus equi strains isolated from foals and their environment in Japan, we compared the in vitro antimicrobial susceptibilities to rifampin of 640 isolates from 64 infected foals and 98 soil isolates from their horse-breeding farms. As a control, 39 human isolates from patients with and without AIDS were also tested for susceptibility to rifampin. All of the isolates showed rifampin sensitivity, except isolates from one infected foal and two patients with AIDS that showed rifampin resistance. To investigate the emergence of rifampin-r...
Patton KM, McGuire TC, Hines MT, Mealey RH, Hines SA.Rhodococcus equi is an important cause of pneumonia in young horses; however, adult horses are immune due to their ability to mount protective recall responses. In this study, the hypothesis that R. equi-specific cytotoxic T lymphocytes (CTL) are present in the lung of immune horses was tested. Bronchoalveolar lavage (BAL)-derived pulmonary T lymphocytes stimulated with R. equi lysed infected alveolar macrophages and peripheral blood adherent cells (PBAC). As with CTL obtained from the blood, killing of R. equi-infected targets by pulmonary effectors was not restricted by equine lymphocyte all...
Bordin AI, Pillai SD, Brake C, Bagley KB, Bourquin JR, Coleman M, Oliveira FN, Mwangi W, McMurray DN, Love CC, Felippe MJ, Cohen ND.Rhodococcus equi is an important pathogen of foals that causes severe pneumonia. To date, there is no licensed vaccine effective against R. equi pneumonia of foals. The objectives of our study were to develop an electron beam (eBeam) inactivated vaccine against R. equi and evaluate its immunogenicity. A dose of eBeam irradiation that inactivated replication of R. equi while maintaining outer cell wall integrity was identified. Enteral administration of eBeam inactivated R. equi increased interferon-γ production by peripheral blood mononuclear cells in response to stimulation with virulent R. ...
Takai S, Kawazu S, Tsubaki S.An enzyme-linked immunosorbent assay (ELISA) was used to diagnose Corynebacterium (Rhodococcus) equi infection in foals. In tests done with different antigen-extraction procedures (sodium dodecyl sulfate, sodium deoxycholate, polyoxy-ethylene [9] p-tert-octylphenol, polyoxy-ethylene [9-10] p-tert-octylphenol, sonification, homogenization, and heat treatment at 121 C), Tween 20 was a satisfactory reactive antigen. Using hyperimmune rabbit sera or infected foal sera, we investigated the specificity and the sensitivity of the ELISA with the Tween 20 antigen of the different serotypes or of the is...
Grimm MB, Cohen ND, Slovis NM, Mundy GD, Harrington JR, Libal MC, Takai S, Martens RJ.To determine whether mares are a clinically important source of Rhodococcus equi for their foals. Methods: 171 mares and 171 foals from a farm in Kentucky (evaluated during 2004 and 2005). Methods: At 4 time points (2 before and 2 after parturition), the total concentration of R equi and concentration of virulent R equi were determined in fecal specimens from mares by use of quantitative bacteriologic culture and a colony immunoblot technique, respectively. These concentrations for mares of foals that developed R equi-associated pneumonia and for mares with unaffected foals were compared. Data...
Chaffin MK, Cohen ND, Martens RJ, Edwards RF, Nevill M.To identify foal-related risk factors associated with development of Rhodococcus equi pneumonia among foals on farms with endemic R. equi infection. Methods: Prospective case-control study. Methods: 220 foals at 2 equine breeding farms in Texas during a 2-year period. Methods: Information collected for each dam included age, time housed on the farm prior to parturition, whether there were any peripartum illnesses, parity, and health of previous foals. Information collected for each foal included breed, sex, gestational age, month and year of birth, location of birth, type of flooring and beddi...
Ren J, Prescott JF.An 81 kb virulence plasmid containing a pathogenicity island (PI) plays a crucial role in the pathogenesis of Rhodococcus equi pneumonia in foals but its specific function in virulence and regulation of plasmid-encoded virulence genes is unclear. Using a LacZ selection marker developed for R. equi in this study, in combination with an apramycin resistance gene, an efficient two-stage homologous recombination targeted gene mutation procedure was used to mutate three virulence plasmid genes, a LysR regulatory gene homologue (ORF4), a ResD-like two-component response regulator homologue (ORF8), a...
Venner M, Credner N, Lämmer M, Giguère S.The objectives of the present study were to determine the relative efficacy of tulathromycin, azithromycin, or azithromycin with rifampin for the treatment of pulmonary abscesses on a farm with endemic infections caused by Rhodococcus equi. Foals with ultrasonographic evidence of pulmonary abscesses (abscess score 8.0-15 cm; n=120) were randomly allocated in four equal treatment groups: (1) tulathromycin intramuscularly; (2) azithromycin monotherapy, orally; (3) azithromycin with rifampin, orally; (4) saline intramuscularly as a placebo. Physical examination and thoracic ultrasonography were p...
Giguère S, Hernandez J, Gaskin J, Miller C, Bowman JL.To evaluate WBC concentration, plasma fibrinogen concentration, and an agar gel immunodiffusion (AGID) test for early identification of Rhodococcus equi-infected foals. Methods: Prospective study. Methods: 162 foals from a farm with enzootic R equi infection. Methods: Blood samples were obtained from each foal at 4-week intervals for measurement of WBC and plasma fibrinogen concentrations and at 2-week intervals for detection of anti-R equi antibody by an AGID assay. Diagnostic performance of WBC and fibrinogen concentrations was assessed by use of receiver operating characteristic curve analy...
