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1.
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   

2.
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   

3.
Equine piroplasmosis is caused by one of 2 erythrocytic parasites Babesia caballi or Theileria equi. Although the genus of the latter remains controversial, the most recent designation, Theileria, is utilized in this review. Shared pathogenesis includes tick‐borne transmission and erythrolysis leading to anemia as the primary clinical outcome. Although both parasites are able to persist indefinitely in their equid hosts, thus far, only B. caballi transmits across tick generations. Pathogenesis further diverges after transmission to equids in that B. caballi immediately infects erythrocytes, whereas T. equi infects peripheral blood mononuclear cells. The recent re‐emergence of T. equi in the United States has increased awareness of these tick‐borne pathogens, especially in terms of diagnosis and control. This review focuses in part on factors leading to the re‐emergence of infection and disease of these globally important pathogens.  相似文献   

4.
Strangles, caused by the Gram‐positive bacteria Streptococcus equi subspecies equi (S. equi), is a highly contagious upper respiratory infection in horses. The infection is transmitted by inhalation or direct contact with mucopurulent discharge from an infected animal, resulting in fever, depression, and submandibular and retropharyngeal lymph node enlargement that can lead to respiratory distress. Complications include secondary cellulitis at external abscessation sites, guttural pouch empyema and its persistence into the carrier state, purpura haemorrhagica, metastatic abscessation, emergency tracheostomies and rarely secondary S. equi pneumonia or myositis. Control of outbreaks requires strict isolation protocols and hygiene measures. Detection methods of the index case and carrier state are constantly being refined to assist in the identification and prevention of disease perpetuation.  相似文献   

5.
During medical management of mild colic in a 12‐year‐old Quarter Horse, mid‐gestation mare, unilateral purulent nasal discharge from the right nostril was noted. Endoscopic examination revealed guttural pouch empyema. Culture was positive for Corynebacterium pseudotuberculosis and negative for Streptococcus equi ssp. equi. A synergistic haemolysis inhibition titre of 1024 was consistent with C. pseudotuberculosis infection. Treatment included serial lavages and local infusion of antibiotics into the guttural pouches along with a 6‐week course of oral trimethoprim–sulfamethoxazole and rifampicin. Overall, no additional sites of infection were identified and the mare responded well to treatment, delivering a healthy, full‐term foal. This case emphasises that C. pseudotuberculosis, although uncommon, should be considered as a differential for guttural pouch empyema.  相似文献   

6.
For decades researchers have been targeting prevention of Rhodococcus equi (Rhodococcus hoagui/Prescottella equi) by vaccination and the horse breeding industry has supported the ongoing efforts by researchers to develop a safe and cost effective vaccine to prevent disease in foals. Traditional vaccines including live, killed and attenuated (physical and chemical) vaccines have proved to be ineffective and more modern molecular‐based vaccines including the DNA plasmid, genetically attenuated and subunit vaccines have provided inadequate protection of foals. Newer, bacterial vector vaccines have recently shown promise for R. equi in the mouse model. This article describes the findings of key research in R. equi vaccine development and looks at alternative methods that may potentially be utilised.  相似文献   

7.
Rhodococcus equi is an opportunistic, intracellular saprophyte that causes severe pyogranulomatous pneumonia in foals. The bacterium displays in vitro susceptibility to many antibiotics. The highest efficacy against R. equi in vitro and in vivo is achieved by using a combination of rifampicin and macrolide antibiotics. Recent years have seen an upward trend in the minimum inhibitory concentration (MIC) of rifampicin and erythromycin, suggesting increasing resistance of R. equi to these antibiotics. The aim of the study was to determine the antimicrobial activity of 24 selected antibiotics against R. equi strains isolated from dead foals and from the environment of horse breeding farms with and without endemic R. equi infections. Minimum inhibitory concentration gradient strips were used to determine the lowest concentration of the antibiotic that inhibited the growth of R. equi. Based on normal MIC distribution, an epidemiologic cutoff values (ECOFF) were assessed for particular antibiotics and R. equi strains. The results were compared with ECOFFs for S. aureus, according to the European Committee on Antimicrobial Susceptibility Testing data. The data indicate that the lowest MIC values were obtained for clarithromycin, rifampicin, imipenem, and vancomycin. The majority of R. equi strains can be classified as wild type in relation to the majority of antibiotics. A small percentage of strains presented non-WT (NWT) with the exception of SXT, for which 35% of strains were classified as NWT. The lack of interpretative criteria for R. equi creates a real problem in the assessment of antibiotic sensitivity both for clinical and scientific purposes.  相似文献   

8.
Salmonella enterica serovar Rissen has been recognized as one of the most common serovar among humans and pork production systems in different parts of the world, especially Asia. In the United States, this serovar caused outbreaks but its epidemiologic significance remains unknown. The objectives of this study were to compare the phenotypic (antimicrobial susceptibility) and genotypic attributes of Salmonella Rissen isolated in Thailand (Thai) and the United States (US). All the Thai isolates (n = 30) were recovered from swine faecal samples. The US isolates (n = 35) were recovered from swine faecal samples (n = 29), cattle (n = 2), chicken (n = 2), dog (n = 1) and a ready‐to‐eat product (n = 1). The antimicrobial susceptibility of isolates was determined using the Kirby‐Bauer disk diffusion method with a panel of 12 antimicrobials. Pulse‐field gel electrophoresis (PFGE) was used to determine the genotypic diversity of isolates. All Thai isolates showed multidrug resistance (MDR) with the most frequent antibiotic resistance shown against ampicillin (100%), sulfisoxazole (96.7%), tetracycline (93.3%), streptomycin (90%) and chloramphenicol (30%). About half of the isolates of USA origin were pan‐susceptible and roughly 30% were resistant to only tetracycline (R‐type: Te). Salmonella Rissen isolated from Thailand and the USA in this study were found to be clonally unrelated. Genotypic analyses indicated that isolates were clustered primarily based on the geographic origin implying the limited clonality among the strains. Clonal relatedness among different host species within the same geography (USA) was found. We found genotypic similarity in Thai and US isolates in few instances but with no epidemiological link. Further studies to assess propensity for increased inter‐regional transmission and dissemination is warranted.  相似文献   

9.
This case report describes the history, clinical and diagnostic findings, treatment and outcome of a 3‐year‐old Thoroughbred gelding. The horse was examined for chronic weight loss, intermittent fever of 4 months' duration and acute lameness of 2 weeks' duration, and was finally diagnosed with septic tendonitis of the deep digital flexor tendon and digital flexor tendon sheath caused by Streptococcus equi ssp. zooepidemicus. Investigation of the lower respiratory tract also allowed isolation of S. equi ssp. zooepidemicus. Although surgical treatment was recommended, because of the severity of the lesion and the guarded prognosis for a return to full athletic function, the owner declined surgery. The horse was therefore treated aggressively with antimicrobials using systemic, local and regional approaches, and with anti‐inflammatory drugs. At 20 months after discharge, the horse was able to race, and he is now in full work with 20 races finished successfully.  相似文献   

10.
Streptococcus equi subspecies (ssp.) equi infection (strangles) remains one of the most frequently diagnosed and costly infectious diseases of horses. Large breeding herds, where a disease outbreak competes for personnel and financial resources needed for foaling management, present a special challenge for equine practitioners. A 15‐month outbreak involving 62 clinical cases of strangles occurred on a large Standardbred breeding farm (average population of 1400 horses). Sixteen asymptomatic horses were found to be PCR (polymerase chain reaction)‐positive for S. equi ssp. equi. During the outbreak, serological samples from 48 clinically normal horses were found to be seropositive for S. equi ssp. equi, confirming herd‐wide exposure. After several clinical cases of strangles had been diagnosed, an intranasal S. equi ssp. equi vaccine was administered to clinically normal horses (n = 558) considered to be at risk of exposure. Strangles complications included 7 fatalities (none in vaccinated horses) and 6 cases of purpura haemorrhagica (4 in vaccinated horses). Midway through the outbreak, injectable, sustained release ceftiofur crystalline free acid (CCFA), given as an initial dose followed by a second dose 4 days later, was used exclusively for systemic antimicrobial treatment of clinically affected and PCR‐positive horses. This antimicrobial regimen coincided with a reduction in disease incidence and eventual resolution of the outbreak. Two horses with persistent guttural pouch infection were endoscopically confirmed as carrier horses. The herd history demonstrated that a strangles outbreak will often result in asymptomatic carrier horses and that identification and treatment of these horses are necessary to eliminate long‐term sources of infection. Ceftiofur crystalline free acid was found to be a suitable antimicrobial due to its activity against S. equi ssp. equi and the efficiencies associated with twice parenteral dosing during a 10‐day treatment period. Occurrence of purpura in 4 vaccinated horses suggests that vaccination should be reserved for healthy seronegative horses and avoided during an active outbreak.  相似文献   

11.
A total of 227 field samples from naturally exposed foals aged between 3 weeks and 6 months were used in an evaluation of a peptide‐based enzyme‐linked immunosorbent assay (ELISA) for diagnosis of Rhodococcus equi infection. A biotinylated peptide derived from the virulence‐associated protein A (VapA) of R. equi, a horse pathogen, was synthesized and designated as PN11‐14. The peptide corresponds to the N‐terminal B‐cell epitope TSLNLQKDEPNGRASDTAGQ of the VapA protein. Based upon a serum immunoglobulin (Ig)G titre of 512 as a positive cut‐off value for the R. equi infection, the ELISA provided the overall sensitivity of 47.62%, specificity of 69.67% and an accuracy of 59.47% with a positive predictive value of 57.47% for true R. equi pneumonia. The assay was improved by detecting VapA‐specific IgGb antibodies against N‐terminal B‐cell epitope of the VapA protein rather than IgG antibodies. The VapA‐IgGb ELISA showed the overall sensitivity of 70.47%, specificity of 72.13% and accuracy of 71.36% with a positive predictive value of 68.52%. Diagnosis of R. equi disease in 6‐week‐old foals showed that the VapA‐IgGb ELISA provided an increasing trend (P = 0.0572) in sensitivity of 82.4% in comparison with the VapA‐IgG ELISA which showed the sensitivity of 58.8%. However, differences in specificity of both tests were statistically insignificant (P = 0.357) as analysed by the McNemar test. These results indicated that detection of VapA‐specific IgGb antibodies may be a better predictor of R. equi disease in foals.  相似文献   

12.
Vertebral body osteomyelitis in the cervical spine secondary to Rhodococcus equi has been treated both medically and surgically. This Case Report describes a 4‐month‐old foal exhibiting severe neurological signs from R. equi vertebral body osteomyelitis. Rapid, significant resolvement of neurological signs was noted in this case with surgical debridement and use of synthetic bone filler. The outcome suggests that aggressive surgical therapy in conjunction with synthetic allograft may be indicated in treatment of cervical vertebral body osteomyelitis.  相似文献   

13.
Two consecutive experiments were carried out to determine efficacy of Megasphaera elsdenii inoculation in alleviation of subacute ruminal acidosis (SARA). In the first experiment, SARA was induced by feeding corn‐ and wheat‐based diets (20%, 40%, 60% and 80% of TMR, DM basis) in six ruminally cannulated heifers. Continuous pH was obtained using data loggers embedded in rumen. In corn (80%)‐ and wheat (60%)‐based diets ruminal pH ranged from 5.2 to 5.6 for 7.77 and 5.93 hr. In the second experiment (5 day), M. elsdenii (200 ml; 2.4 x 1010 cfu/ml) was inoculated during the first two days. During the SARA induction period, M. elsdenii and S. bovis in rumen liquor were more abundant in wheat‐based feeding (7.97 and 8.77) than in corn‐based feeding (7.06 and 7.95 per ml, log basis; p < 0.0001 for both). M. elsdenii inoculation increased total volatile fatty acids (VFA) concentration when corn‐based diet was fed, whereas it decreased total VFA concentration when wheat‐based diet was fed (p < 0.004). There was a decrease in the propionic acid proportion (24.04%–19.08%; p < 0.002), whereas no alteration in lactate and ammonia concentrations was observed. M. elsdenii inoculation increased protozoa count (from 5.39 to 5.55 per ml, log basis; p < 0.009) and decreased S. bovis count (from 9.18 to 7.95 per ml, log basis; p < 0.0001). The results suggest that M. elsdenii inoculation may help prevent SARA depending on dietary grain through altering rumen flora as reflected by a decrease in S. bovis count and an increase in protozoa count.  相似文献   

14.
Campylobacter jejuni is one of the major causative pathogens of outbreaks or sporadic cases of diarrhoeal diseases worldwide. In this study, we compared the phenotypic and genetic characteristics of C. jejuni isolates of human and food‐producing animal origins in Korea and examined the genetic relatedness between these two groups of isolates. Regardless of isolation source, all C. jejuni isolates harboured four virulence genes, cadF, cdtB, ciaB and racR, whereas the wlaN and virB11 genes were more frequently observed in human isolates. Antimicrobial susceptibility testing showed that the majority of C. jejuni isolates displayed high‐level resistance to fluoroquinolone (95.2%) or tetracycline (76.2%) antibiotics, and 12.4% of isolates exhibited multidrug resistance (more than three classes of antibiotics tested). Pulsed‐field gel electrophoresis (PFGE) of all Campylobacter isolates revealed 51 different SmaI‐PFGE patterns and six major clusters containing both human and animal isolates. These results indicate that genetically diverse strains of C. jejuni with antimicrobial drug‐resistance and virulence properties have prevailed in Incheon. Nevertheless, some particular populations continue to circulate within the community, providing the evidence for an epidemiological link of C. jejuni infections between humans and food‐producing animals. Therefore, the continued monitoring and surveillance of C. jejuni isolates of human and food‐producing animal origins are required for public health and food safety.  相似文献   

15.
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   

16.
Salmonella enterica is a common food‐borne pathogen with occasional multidrug resistance (MDR). Salmonella genomic island (SGI1) is a horizontally transmissible genomic island, containing an MDR gene cluster. All Salmonella serotypes are public health concern, although there is an additional concern associated with those that harbour SGI1. In Iran, there are no data on the presence of SGI1 variants in Salmonella isolates. The present study was conducted to identify MDR‐ and SGI1‐carrying Salmonella strains isolated from various sources and to compare their genetic relatedness between human and animal sources. In total, 242 Salmonella isolates collected from chicken, cattle, and humans from 2008 through 2014 were studied. The isolates were tested for resistance to 14 antimicrobials via the disc diffusion method. They were also tested for the presence of SGI1 variants via PCR, and genetic relatedness was evaluated based on pulsed‐field gel electrophoresis (PFGE). Resistance to at least one antimicrobial agent was observed in 132 (54%) Salmonella isolates (n = 242), while more than 40% of the isolates showed MDR. Based on PCR analysis, eight variants of SGI1, including SGI1, SGI1‐B, SGI1‐C, SGI1‐D, SGI1‐F, SGI1‐I, SGI1‐J and SGI1‐O, were found in both human and animal isolates. Statistical analysis revealed no significant difference in the prevalence of SGI1 variants between human and animal isolates (p > 0.05). Macrorestriction PFGE analysis of the isolates with the same SGI1 variant and resistance patterns revealed genetic relatedness ranging from 70% to 100% among human and animal isolates. According to our review, this is the first documentation of SGI1 in Salmonella isolates in Iran. The presence of similar SGI1 variants in both humans and animals, along with their related PFGE patterns, suggests that food‐producing animals may be a source of MDR Salmonella isolates in Iran.  相似文献   

17.
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   

18.
Rhodococcus equi is an intracellular pathogen of macrophages that causes rhodococcal pneumonia in foals and immunocompromised people. Evidence exists that neutrophils play a vital role in resistance to infection with R. equi; however, the means by which neutrophils exert their effects have not been clearly defined. In addition to directly killing bacteria, neutrophils also may exert a protective effect by linking innate and adaptive immune responses. In the present study we evaluated the cytokine expression profiles of adult equine neutrophils in response to stimulation with isogenic strains of virulent and avirulent R. equi in vitro. After 2 and 4 h incubation with virulent or avirulent R. equi, adult equine neutrophils expressed significantly (P < 0.05) greater tumor necrosis factor alpha (TNFα), interleukin (IL)-12p40, IL-6, IL-8 and IL-23p19 mRNA, but not interferon gamma (IFNγ) or IL-12p35 mRNA than unstimulated neutrophils. Furthermore, virulent R. equi induced significantly greater IL-23p19 mRNA than avirulent R. equi. These results demonstrate that R. equi-stimulated neutrophils are a source of many proinflammatory cytokines. Furthermore, these results suggest that IL-23 may be preferentially expressed over IL-12 in response to exposure with R. equi, and that this response may be more strongly induced by virulent R. equi than avirulent R. equi. Collectively, the data presented herein suggest a non-phagocytic role for neutrophils that may influence the type of adaptive immune response to R. equi.  相似文献   

19.
There is a distinct age-associated susceptibility of horses to Rhodococcus equi infection. Initial infection is thought to occur in the neonatal and perinatal period, and only foals less than 6 months of age are typically affected. R. equi is closely related and structurally similar to Mycobacterium tuberculosis, and causes similar pathologic lesions. Protective immune responses to M. tuberculosis involve classical major histocompatibility complex (MHC)-restricted T cells that recognize peptide antigen, as well as MHC-independent T cells that recognize mycobacterial lipid antigen presented by CD1 molecules. Given the structural similarity between these two pathogens and our previous observations regarding R. equi-specific, MHC-unrestricted cytotoxic T lymphocytes (CTL), we developed 3 related hypotheses: (1) CD1 molecules are expressed on equine antigen presenting cells (APC), (2) CD1 expression on APC is less in foals compared to adults and (3) infection with live virulent R. equi induces up-regulation of CD1 on both adult and perinatal APC. CD1 expression was examined by flow cytometric analysis using a panel of monoclonal CD1 antibodies with different species and isoform specificities.

Results

Three CD1 antibodies specific for CD1b showed consistent cross reactivity with both foal and adult monocyte-derived macrophages (MDM). CD1b and MHC class II expression were significantly higher on adult MDM compared with foals. R. equi infected MDM showed significantly lower expression of CD1b, suggesting that infection with this bacterium induces down-regulation of CD1b on the cell surface. Histograms from dual antibody staining of peripheral blood mononuclear cells also revealed that 45–71% of the monocyte population stained positive for CD1b, and that the majority of these also co-expressed MHC II molecules, indicating that they were APC. The anti-CD1 antibodies showed no binding or minimal binding to bronchoalveolar lavage (BAL)-derived macrophages.

Conclusion

The CD1b isoform is evolutionarily conserved, and is present on equine MDM, as well as on circulating blood monocytes. The unique susceptibility of foals to R. equi infection may be due in part to lower expression of CD1 and MHC class II, as observed in this study. The data also suggests that infection with R. equi induces down-regulation of CD1b on equine MDM. This may represent a novel mechanism by R. equi to avoid detection and killing of infected cells by the immune system, similar to that observed when human APC are infected with M. tuberculosis.  相似文献   

20.
The anti‐microbial susceptibility and genetic diversity of 65 strains of Streptococcus equi ssp. zooepidemicus (Sez) isolated from mares presenting clinical signs of endometritis was determined by disk agar diffusion and pulsed field gel electrophoresis (PFGE) methods, respectively. Overall, Sez isolates were susceptible to β‐lactams, enrofloxacin, trimethoprim‐sulfamethoxazole and gentamicin. These anti‐microbials could be recommended as empiric anti‐microbial therapy in cases of endometritis caused by Sez. Pulsed field gel electrophoresis typing revealed a great genetic diversity (56 different PFGE macrorestriction profiles) and a low level of genetic relatedness amongst the isolates.  相似文献   

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