首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
Reasons for performing the study: Disease caused by Rhodococcus equi is a significant burden to the horse breeding industry worldwide. Early detection of rhodococcal pneumonia, albeit important to minimise treatment costs, is difficult because of the insidious nature of the disease and the lack of definitive diagnostic tests. Objectives: To investigate air sampling from the breathing zone of neonatal foals as a predictor of subsequent rhodococcal pneumonia. Methods: Air samples were collected from the breathing zone of 53 neonatal foals (age ≤10 days) and again at the time of routine ultrasonographic screening for R. equi pneumonia (age 1–2 months). Results: Pneumonia was diagnosed ultrasonographically in 23% of foals. Virulent R. equi was detected in air from the breathing zone of 19% of neonatal foals and 45% of foals at age 1–2 months. There was no association between virulent R. equi in the breathing zone of foals and the subsequent ultrasonographic diagnosis of rhodococcal pneumonia. The median concentration of virulent R. equi in the breathing zone of both neonates (0 [range 0–4] colony‐forming units [cfu]/250 l) and older foals (0 [range 0–3] cfu/250 l) was not significantly different from that in background air samples (0 [range 0–6] cfu/250 l). There was no difference in the concentration of virulent R. equi in the breathing zone of older foals that were diagnosed with rhodococcal pneumonia or clinically normal foals. Conclusion: Detection of virulent R. equi in air from the breathing zone was not a positive predictor of rhodococcal pneumonia in foals up to age ≤2 months. Potential relevance: Selective culture of air samples from the breathing zone of young foals is not better at diagnosing rhodococcal pneumonia than early ultrasonographic screening. However, culture of air samples from the breathing zone of older foals remains a useful herd‐based epidemiological tool.  相似文献   

2.
Pneumonia caused by Rhodococcus equi is one of the most important causes of disease and death in foals. R. equi can also be cultured from a large variety of extrapulmonary sites of infection. In the absence of an effective vaccine, ultrasonographic screening for early detection of pulmonary lesions has become routine practice at many farms endemic for pneumonia caused by R. equi. Consequently, the most frequently recognised form of R. equi infection at such farms is a subclinical form in which foals develop sonographic evidence of peripheral pulmonary consolidation or abscessation without necessarily manifesting clinical signs. Evidence exists that not all foals with ultrasonographic lesions will progress to develop clinical signs, and treating a large proportion of foals based on subclinical ultrasonographic findings has been linked to emergence of macrolide‐ and rifampin‐resistant R. equi at a horse farm. Selectively treating only those foals with larger lesion scores and monitoring foals with daily physical inspections and weekly thoracic ultrasonography offers an approach that could decrease antimicrobial drug use without significantly increasing mortality. Current evidence continues to support the combination of rifampin with a macrolide (azithromycin, clarithromycin or erythromycin) for treating clinical infections caused by R. equi despite recently described pharmacological interactions between these drugs. When infection with a macrolide‐resistant isolate is confirmed, limited effective alternatives exist.  相似文献   

3.
Rhodococcus equi infections cause severe pulmonary disease in foals, affecting animal welfare and increasing production costs in horse-breeding farms. Extra-pulmonary disorders (EPD) are relatively common and can occur independently of pulmonary disease; foals with EPD have a more guarded prognosis. The accompanying paper by Shaw et al. (2021) reports the successful diagnosis and medical treatment of a large abdominal abscess caused by R. equi infection. The authors report on the benefits of using gallium maltolate, a semimetal compound with antimicrobial activity, in combination with traditional R. equi infection antimicrobial treatment (combination of a macrolide and rifampicin). Experimental studies are needed to understand further the benefits of this combined therapy, to evaluate the synergistic effects and if it improves the concentration of antimicrobial drugs into infected tissues. The publication of this case report in Equine Veterinary Education is of clinical importance to equine practitioners when diagnosing and treating R. equi infected foals with or without EPD.  相似文献   

4.
A 20‐year‐old, Thoroughbred mare in the fifth month of gestation was examined for weight loss, pyrexia and lethargy. Physical examination, ultrasonography and radiography revealed a severe abscessing pneumonia and a dead fetus. The mare did not respond to symptomatic treatment and died suddenly. Necropsy revealed multifocal pulmonary abscessation. Rhodococcus equi was isolated from the lungs, liver and kidneys. Specific immune function of the mare and presence of the virulence associated protein A (VapA) of the R. equi isolated was not determined. It is likely that immunosuppression is required for systemic R. equi infections in adult horses; however, it is unknown if VapA is necessary to produce disease in adult horses.  相似文献   

5.
This case report describes the treatment and outcome of a 3.5-month-old lame foal, with a history of pneumonia associated with Rhodococcus equi. Clinical examination identified osteomyelitis of the scapulohumeral joint. The unusual location of the Rhodococcus equi osteomyelitis unresponsive to prevention and adequate treatment led to euthanasia of the patient. Post-mortem findings confirmed bronchopneumonia due to Rhodococcus equi as well as the osteomyelitis of the scapulohumeral joint. This case highlights that Rhodococcus equi should be considered as a pathogen in extrapulmonary locations such as septic arthritis and osteomyelitis in foals with history of bronchopneumonia. Early and aggressive treatment should be considered.  相似文献   

6.
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 in North America. Correlates of protective immunity for R. equi infections of foals remain elusive, but recent evidence indicates that innate immune responses are important both for mediating killing and orchestrating adaptive immune responses. A macrolide antimicrobial in combination with rifampin remains the recommended treatment for foals with R. equi pneumonia. Great need exists to identify which antimicrobial combination is most effective for treating foals with R. equi pneumonia and to limit emergence of antimicrobial-resistant strains. In the absence of an effective vaccine against R. equi, passive immunisation remains the only commercially available method for effectively reducing the incidence of R. equi pneumonia. Because passive immunisation is expensive, labour-intensive and carries risks for foals, great need exists to develop alternative approaches for passive and active immunisation.  相似文献   

7.
Rhodococcus equi pneumonia is a major cause of morbidity and mortality in neonatal foals. Much effort has been made to identify preventative measures and new treatments for R. equi with limited success. With a growing focus in the medical community on understanding the genetic basis of disease susceptibility, investigators have begun to evaluate the interaction of the genetics of the foal with R. equi. This review describes past efforts to understand the genetic basis underlying R. equi susceptibility and tolerance. It also highlights the genetic technology available to study horses and describes the use of this technology in investigating R. equi. This review provides readers with a foundational understanding of candidate gene approaches, single nucleotide polymorphism‐based, and copy number variant‐based genome‐wide association studies, and next generation sequencing (both DNA and RNA).  相似文献   

8.
Our objective was to characterize the association between types of radiographic findings and outcome in foals with pneumonia caused by Rhodococcus equi. Admission lateral thoracic radiographs of 62 foals with culture‐confirmed R. equi pneumonia were reviewed retrospectively. A scoring system was developed to individually assess the severity of alveolar pattern, interstitial pattern, tracheobronchial lymphadenopathy, pleural effusion, and the number of nodular opacities and cavitary lesions. Individual scores were added to obtain a total radiographic score ranging from 0 (normal) to 22. Forty‐three of 62 foals (69%) survived to discharge. The median total radiographic score of nonsurvivors (14; range, 9–16) was significantly (P = 0.007) higher than that of survivors (11; range, 4–15). Foals with a total radiographic score of greater than or equal to 15 were 6.15 times (95% CI: 1.35 to 28.2) less likely to survive than foals with a lower score (P = 0.019). A multivariate logistic regression model was used to identify the potential associations between specific types of radiographic lesions and outcome. The model was statistically significant (P = 0.002) and correctly classified 75.8% of foals. Only severity of alveolar pattern and number of cavitary lesions made statistically significant contributions to the model. There was no significant association between concurrent isolation of other bacteria along with R. equi and the types or severity of radiographic lesions. Based on the results of this study, severity of alveolar pattern and number of cavitary lesions are the radiographic findings significantly associated with a poor outcome in foals with R. equi pneumonia.  相似文献   

9.
Rhodococcus equi is a Gram-positive facultative intracellular bacterium that causes pyogranulomatous pneumonia in foals and immunocompromised people. In the present study, signature-tagged transposon mutagenesis was applied for the negative selection of R. equi mutants that cannot survive in vivo. Twenty-five distinguishable plasmid-transposon (plasposon) vectors by polymerase chain reaction (PCR), each containing a unique oligonucleotide tag, were constructed and used to select the transposon mutants that have in vivo fitness defects using a mouse systemic infection model. Of the 4,560 transposon mutants, 102 mutants were isolated via a real-time PCR-based screening as the mutants were unable to survive in the mouse model. Finally, 50 single transposon insertion sites were determined via the self-cloning strategy. The insertion of the transposon was seen on the virulence plasmid in 15 of the 50 mutants, whereas the remaining 35 mutants had the insertion of transposon on the chromosome. The chromosomal mutants contained transposon insertions in genes involved in cellular metabolism, DNA repair and recombination, gene regulation, non-ribosomal peptide synthesis, and unknown functions. Additionally, seven of the chromosomal mutants showed a reduced ability to multiply in the macrophages in vitro. In this study, we have identified several biosynthetic pathways as fitness factors associated with the growth within macrophages and survival in mice.  相似文献   

10.
SUMMARY 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.  相似文献   

11.
A 4-month-old Thoroughbred filly presented with pyrexia, inappetence and diarrhoea. Abdominal ultrasonography revealed a multilobulated abdominal mass that was determined to be associated with the caecum using computed tomography. Computed tomography also identified mesenteric lymphadenopathy and a pulmonary mass in the left caudal lung lobe. Percutaneous aspiration of the abdominal mass yielded pure growth of Rhodococcus equi. The filly responded in a positive fashion to the administration of clarithromycin, rifampin and gallium maltolate. Follow-up computed tomography revealed complete resolution of the abdominal mass and lymphadenopathy. Extrapulmonary disorders associated with R. equi should be considered even when thoracic ultrasonography reveals no evidence of pulmonary pathology. Although intra-abdominal abscesses have a grave prognosis, successful treatment is possible. Gallium maltolate can be safely administered to foals and may improve patient outcomes.  相似文献   

12.
The sonographic characteristics of intraabdominal abscesses in 11 foals and intraabdominal lymphadenitis in five foals with Rhodococcus equi infections are presented. Intraabdominal abscesses were usually present in the ventral abdomen adjacent to the ventral body wall, well‐marginated, and contained a mixed or complex echo pattern. Lymphadenitis appeared as singular or multiple clusters of lymph nodes of mixed echogenicity adjacent to any portion of the gastrointestinal tract or body wall. Sonographic findings were supported by necropsy examinations, but sonographic measurements consistently underestimated the size of abscess.  相似文献   

13.
A relative immunodeficiency of young foals is considered to account for the increased susceptibility of foals to infectious diseases, including pneumonia caused by Rhodococcus equi. In this report, peripheral blood mononuclear cells (PBMCs) from healthy foals at 14 and 56 days of age, or from their dams, were incubated with three stimulatory and one nonstimulatory (control) synthetic cytosine-phosphate-guanosine oligodeoxynucleotides (CpG-ODNs), and mRNA expression of tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), interleukin (IL) -6, IL-8, IL12-p35, and IL-12p40 were determined. Results indicated that synthetic CpG-ODNs can induce strong, rapid cytokine responses in healthy foals and adult horses. B-class CpG-ODNs 2135 and 2142 induced greater messenger RNA (mRNA) expression of IFN-γ, IL-6, and IL-12p40 than the C-class CpG-ODN 2395 in foal PBMCs. In foals, B-class CpG-ODNs induced IFN-γ, IL-6, and IL-12P40 mRNA expression that was similar to or higher in magnitude than that observed in adult horses. These observations indicate that CpG-ODNs might be useful as immunomodulators or as potential adjuvants for vaccines to aid in preventing R. equi pneumonia and other bacterial diseases of foals.  相似文献   

14.
Objective – To describe the clinical presentation, case management, and outcome in 2 foals with Rhodococcus equi infection associated with presumptive severe immune‐mediated hemolytic anemia. Series Summary – Two foals diagnosed with R. equi pneumonia on the basis of tracheal wash cultures, thoracic radiographs, and thoracic ultrasonography were concurrently diagnosed with hemolytic anemia. Both foals required whole blood transfusions, and were treated with the antimicrobial combination of rifampin and a macrolide (eg, clarithromycin, erythromycin, or azithromycin). Dexamethasone was used to prevent further hemolysis in both foals, and to treat acute lung injury/acute respiratory distress syndrome in 1 of the foals. Both foals survived, and required prolonged antimicrobial therapy. New or Unique Information Provided – Although extra‐pulmonary disorders are commonly diagnosed in foals infected with R. equi, hemolytic anemia is rarely described. Dexamethasone is considered the treatment of choice for immune‐mediated hemolytic anemia, but may be contra‐indicated in foals with severe bacterial infections. In these foals, a relatively low dose and short duration of dexamethasone was utilized in an attempt to minimize immune suppression, although early discontinuation in 1 foal precipitated a second hemolytic crisis.  相似文献   

15.
Rhodococcus equi remains a significant pathogen, causing severe pneumonia in foals. The development of vaccines and serologic diagnosis could be greatly facilitated by studying the humoral immune response to this equine pathogen. In this study, a crude extract of R. equi ATCC 33701-secreted proteins combined with the Montanide® ISA70 adjuvant was found to be highly immunogenic in mice with the highest titer of 99,000 on day 42 after the first subcutaneous immunization. This immune response was dependent on the quantity of proteins injected and the presence of adjuvant. By dot-blotting, eight recombinant secreted proteins were identified to react strongly with sera from immunized mice. Of these eight proteins, four were detected as immunogenic only when administered in conjunction with adjuvant. This screening strategy led to the identification of promising new candidates for vaccine development.  相似文献   

16.
The aim of this study was to evaluate the usefulness of the previously identified B‐cell epitope TSLNLQKDEPNGRASDTAGQ of the VapA protein of Rhodococcus equi and its association with R. equi pneumonia. A modified peptide designated PN11‐14 corresponding to the epitope was recognized by all sera from experimentally infected foals with virulent R. equi ATCC103+ containing the virulence plasmid but not by its plasmid‐cured derivative ATCC103? strain. Marked levels of VapA‐specific immunoglobulin (Ig)G were detected in all sera from the ATCC103+ infected foals at 2 weeks after the infection. One control animal had high titres as determined by the peptide enzyme‐linked immunosorbent assay (ELISA), indicating the ELISA may not absolutely differentiate between foals with R. equi pneumonia and healthy exposed foals in farms where the prevalence of disease is high. However, numbers of animals used were small. Further evaluation of the peptide ELISA with field samples is necessary to determine whether the assay is diagnostically useful. This study showed that levels of passive transfer of maternal IgG antibodies to the epitope in newborn foals could be measured. Interestingly, the maternally derived antibodies were found to significantly (P < 0.05 by Student's t‐test) decline 2 weeks after birth. Seroconversion against naturally occurring VapA expressing R. equi could be detected in some foals at 4 weeks of age. Antibodies to the epitope peaked and were significantly (P < 0.05) greater in foals aged between 6 and 8 weeks. These results indicated that the peptide ELISA could be used to monitor anti‐VapA antibodies in foals, particularly those at the age of 4–6 weeks. It is possible that the ELISA may be of some use as a diagnostic test on farms where R. equi is non‐endemic. Further studies using large number of field samples are needed to verify this assumption.  相似文献   

17.
Rhodococcus equi (R equi) pneumonia is an important cause of disease and death in foals. Feces from mares can contain R equi, including virulent R equi, and thus may act as a source of the bacteria at horse breeding farms. A previous report documented that every mare at a farm in central Kentucky shed virulent R equi in at least one of four fecal samples collected serially during the periparturient period. The objective of this study was to assess the extent to which this high prevalence of fecal shedding could be replicated at other horse breeding farms. The frequency of detection of R equi and virulent R equi in fecal samples was studied among 131 mares from 24 farms in central Kentucky. The proportions of fecal samples from mares containing R equi and virulent R equi were 95% and 76%, respectively. These findings indicate that R equi and virulent R equi may be isolated with high frequency from feces of mares at breeding farms in central Kentucky, and that mares are a source of virulent R equi for the environment of their foals.  相似文献   

18.
The aim of this retrospective study was to determine the clinical usefulness of thoracic ultrasonography compared to thoracic radiography in evaluation of Rhodococcus equi pneumonia. Criteria for patient inclusion in this study were: (1) isolation of R. equi from transtracheal aspirate, (2) radiographic evaluation of the pulmonary parenchyma, and (3) sonographic evaluation of the pulmonary parenchyma. Seventeen foals met this criteria and their medical records were reviewed. Pyogranulomatous pneumonia was identified radiographically in 13 foals. Severe consolidative pneumonia with no detectable abscessation was identified radiographically in three others. Both consolidation and abscessation were identified radiographically in one. In this foal only consolidation was ultrasonographically identified. Ultrasonographically, pulmonary abscessation was identified in 12 foals and pulmonary consolidation with no detectable abscessation was identified in three others. Sonographic examination allowed detection of only pleural irregularities in one foal, which was subsequently found to have pyogranulomatous pneumonia radiographically. Results indicate that ultrasonography may be an accurate alternative imaging modality for detection of pulmonary pathology attributed to R. equi pneumonia in foals when thoracic radiography is not available.  相似文献   

19.
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 are achieved as after intramuscular or subcutaneous administration. Intravenously injected gamithromycin was tolerated without any adverse drug reactions. The protocols for treatment of equine pulmonary infections caused by Rhodococcus equi should be revised accordingly.  相似文献   

20.
This report describes the diagnosis and successful treatment of multiple extrapulmonary sequelae of Rhodococcus equi (R. equi) pneumonia in a 3‐month‐old filly. Bilateral uveitis and hyphaema, haemolytic anaemia and polysynovitis developed in this foal and were likely due to immune‐mediated mechanisms. The challenges associated with diagnosis and treatments of these extrapulmonary disorders are discussed. The filly was treated initially with clarithromycin and rifampin; however, a blood transfusion and immunosuppressive therapy with dexamethasone were required due to progressive haemolysis and for treatment of uveitis and polysynovitis. Bilateral hyphaema was successfully treated with intracameral injections of a recombinant tissue plasminogen activator. The development of antimicrobial resistance in R. equi was an additional challenge encountered in the management of this case and emphasises the importance of culture and in vitro antimicrobial susceptibility testing of isolates from foals with R. equi pneumonia. Extrapulmonary disorders associated with R. equi pneumonia are likely underdiagnosed and associated with a poor prognosis. This case highlights the importance of thorough and ongoing diagnostic assessment of foals with R. equi pneumonia and demonstrates that a successful outcome can be achieved with appropriate and directed treatment.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号