Virulence-associated protein characterisation of Rhodococcus equi isolated from bovine lymph nodes

Rhodococcus equi has a low pathogenicity in cattle, but it occasionally causes lymph node granulomas, which are detected at abattoir post mortem inspection, and must be distinguished from tuberculous granulomas. Lymph node lesions were detected in 6719 cattle, from a total of 3,263,622 cattle examined post mortem in abattoirs, in the Republic of Ireland, during 1997 and 1998. Histological examination was performed on all lesions, principally for the purpose of identifying animals with tuberculosis. A total of 1122 of the lesions were cultured on blood agar and on Stonebrinks and Lowenstein-Jensen medium containing pyruvate, because the histological findings were difficult to interpret or were suggestive of R. equi infection. R. equi was isolated from 264 lesions. Almost all of the R. equi granulomas were confined to a single lymph node, and were present predominantly in the retropharyngeal, bronchial and mediastinal lymph nodes. R. equi granulomas were present in a significantly higher proportion of the lesions detected in steers and heifers compared to cows. The prevalence in the total population of 3.3 million cattle examined post mortem was 0.008%. The 15-17kDa antigens, associated with virulence in this organism, and the 20kDa antigen, associated with intermediate virulence, were not detected in isolates from 146 cattle, analysed by immunoblot assays. A PCR assay to detect the plasmid gene encoding the 15-17kDa antigens was also negative for isolates from these 146 animals. Plasmids were not detected in 30 isolates which were examined.

Rhodococcus equi infections in immunocompetent hosts: case report and review

Rhodococcus equi is an unusual cause of infection in humans. Infection in immunocompetent patients is extremely rare-only 19 cases in immunocompetent hosts have been reported. Localized infections represent nearly 50% of reported cases. Pulmonary infections account for only 42% of infections in immunocompetent hosts, compared with 84% of infections in immunocompromised hosts. The mortality rate among immunocompetent patients is approximately 11%, compared with rates of 50%-55% among human immunodeficiency virus (HIV)-infected patients and 20%-25% among non-HIV-infected immunocompromised patients. Treatment of infections in immunocompetent hosts depends on the site of infection. Serious infections need to be treated with combinations of parenteral antibiotics, followed by combinations of oral antibiotics. Surgical treatment is necessary for certain types of local infections. We report a pulmonary infection due to R. equi in an immunocompetent patient, and we review all reported cases of R. equi infection in immunocompetent hosts.

Chronic scalp wound infection due to Rhodococcus equi in an immunocompetent patient

A case of chronic scalp wound infection due to Rhodococcus equi in an immunocompetent individual following heavily contaminated traumatic injury was successfully treated by combining antibiotics and surgery. The agents used were erythromycin and rifampicin.

Pulmonary infection caused by Rhodococcus equi in HIV-infected patients: report of four patients from northern Thailand

We report four human immunodeficiency virus (HIV)-infected patients (3 men and one woman, average age, 34.3 years) with pulmonary infection (two with pneumonia and two with lung abscess) caused by Rhodococcus equi. These patients, who presented with fever and productive cough, were admitted to Nakornping Hospital in northern Thailand. Chest roentgenograms showed pulmonary infiltration and/or cavitary lesions. Their conditions were poor because of severe anemia, and transfusion was necessary in three of the four patients. Before culture results were available, the etiologic microorganisms identified in sputum smears were gram-positive and acid-fast coccobacilli. One of the four patients had a mixed infection with R. equi and Salmonella enteritidis. The mean CD4 lymphocyte count in the three tested patients was 10/mm3 (CD4/CD8 ratio = 0.057). Four isolates of R. equi were sensitive to imipenem, minocycline, erythromycin, vancomycin, and ciprofloxacin (minimum inhibitory concentrations; MICs, <or=1.56 microg/ml), but resistant to most beta-lactam antibiotics. Two isolates were sensitive (MICs, 0.20 and 0.78 microg/ml) and two resistant (MICs 50 and >100 microg/ml) to rifampicin. Two patients were treated with erythromycin plus rifampicin, while the other two were treated with anti-tuberculous drugs. However, treatment was ineffective; three patients subsequently died because of respiratory failure, and one patient did not improve and was transferred to another hospital in her hometown.

Evaluation of nasotracheal aspiration as a diagnostic tool for Rhodococcus equi pneumonia in foals

The reliability of preparing bacteriological cultures from nasotracheal aspirates of foals routinely in order to diagnose R. equi pneumonia in foals was studied by isolating Rhodococcus equi from specimens obtained from 96 foals by nasotracheal aspiration with a silicon catheter. Results were compared with specimens obtained from 21 foals by transtracheal aspiration (percutaneous tracheal puncture). These 117 foals showed clinical signs of respiratory tract infection at sampling. R. equi was isolated from 14 of 21 (66.7%) specimens by transtracheal aspiration and from 59 of 96 (61.4%) specimens by nasotracheal aspiration, 649 of 655 isolates (99.1%) from the 73 positive specimens were virulent R. equi, and the culture-positive foals were diagnosed as having R. equi pneumonia. To assess the contamination of aspirates by organisms from the nasopharynx, the results of R. equi isolation from nasal swabs obtained from 56 of the 96 foals were compared to those obtained by nasotracheal aspiration from the same foals. R. equi was isolated from 2 of the 56 nasal swabs: one from a tracheal aspirate was positive, and the other was not. These results suggest that the nasotracheal aspiration technique, which is noninvasive and not associated with complications, could be used as an alternative to the transtracheal aspiration method, especially for the diagnosis of R. equi pneumonia in foals.

Rhodococcus equi lung abscess complicating Evan's syndrome treated with corticosteroid

We report a case of Rhodococcus equi, an unusual pathogen, causing a right upper lobe lung abscess in a patient with Evan's syndrome (auto-immune haemolytic anaemia and thrombocytopenia) who was treated with high-dose corticosteroid therapy. The patient was treated successfully with clarithromycin, vancomycin, ciprofloxacin and imipenen which appear to be effective in combination for this unusual condition in which the treatment regimen has been controversial.

Association of disease with isolation and virulence of Rhodococcus equi from farm soil and foals with pneumonia

OBJECTIVE

To determine whether isolation and virulence of Rhodococcus equi from soil and infected foals are associated with clinical disease.

DESIGN

Cross-sectional and case-control study.

SAMPLE POPULATION

R equi isolates from 50 foals with pneumonia and soil samples from 33 farms with and 33 farms without a history of R equi infection (affected and control, respectively).

PROCEDURE

R equi was selectively isolated from soil samples. Soil and clinical isolates were evaluated for virulence-associated protein antigen plasmids (VapA-P) and resistance to the beta-lactam antibiotics penicillin G and cephalothin. Microbiologic cultures and VapA-P assays were performed at 2 independent laboratories.

RESULTS

VapA-P was detected in 49 of 50 (98%) clinical isolates; there was complete agreement between laboratories. Rhodococcus equi was isolated from soil on 28 of 33 (84.8%) affected farms and 24 of 33 (72.7%) control farms, but there was poor agreement between laboratories. Virulence-associated protein antigen plasmids were detected on 14 of 66 (21.2%) farms by either laboratory, but results agreed for only 1 of the 14 VapA-P-positive farms. We did not detect significant associations between disease status and isolation of R equi from soil, detection of VapA-P in soil isolates, or resistance of soil isolates to beta-lactam antibiotics. No association between beta-lactam antibiotic resistance and presence of VapA-P was detected.

CONCLUSIONS AND CLINICAL RELEVANCE

On the basis of soil microbiologic culture and VapA-P assay results, it is not possible to determine whether foals on a given farm are at increased risk of developing disease caused by R equi.

HIV-infected patient with a Rhodococcus equi pneumonia

The case history of a HIV patient with a pulmonary infect of Rhodococcus equi is presented. He recovered after prolonged treatment with antibiotics and lobectomy. The Rhodococcus equi infection was the presenting symptom of his impaired immune status caused by HIV infection.

MICs of oxazolidinones for Rhodococcus equi strains isolated from humans and animals

Eperezolid and linezolid are representatives of a new class of orally active, synthetic antimicrobial agents. The in vitro activity values (MICs) of linezolid, eperezolid, and comparator antibiotics against 102 strains of Rhodococcus equi isolated from humans and animals were determined. Linezolid was more active than eperezolid against the strains tested; premafloxacin was the most active comparator antibiotic.

Isolation of rare opportunistic pathogens in Hungary: case report and short review of the literature. Rhodococcus equi

Rhodococcus equi is a well-established pathogen in foal pneumonia and is increasingly recognized as a pathogen in immunocompromised humans. We have isolated a Gram-positive coccobacillus from 8 blood samples and lung tissues of a renal transplant patient. Colony morphology, growth in Lowenstein-Jensen medium, 21 biochemical reactions, the characteristic morphological cycle (coccus-rod-coccus) and the CAMP test established the R. equi diagnosis. Histological studies of 2 lung biopsy specimens revealed numerous microabscesses with aggregates of polymorphonuclear leukocytes surrounded by abundant foamy macrophages. Our isolates proved to be sensitive to majority of antibacterial drugs. The appropriate therapy (amoxicillin-clavulanate) proved to be effective, however six months later a relapse was observed. Data show that in spite of its rare occurrence, R. equi infection represents a diagnostic and therapeutic challenge. The taxonomical, epidemiological, clinico-pathological, diagnostic and therapeutic data of R. equi are discussed.

Evaluation of mini-VIDAS rapid test for detection of Listeria monocytogenes from production lines of fresh to cold-smoked fish

This study was conducted to evaluate the efficacy of the mini-VIDAS Listeria monocytogenes (LMO) system (BioMérieux Vitek, Inc., Missouri, USA) for detection of L. monocytogenes in environmental and fish samples from three Portuguese cold-smoking plants and from their fresh fish suppliers. Mini-VIDAS-LMO is a fully automated system that uses fluorescent ELFA (Enzyme Linked Fluorescent Assay) technology for detection of Listeria monocytogenes antigens in food. It can be a rapid screening method alternative to time consuming classical isolation and identification. Two hundred and ninety five samples were tested in mini-VIDAS-LMO and in parallel by the ISO 11290-1 traditional protocol. The mini-VIDAS-LMO detected 8 of the 11 confirmed positive samples and presented 11 false positive results. The specificity of the mini-VIDAS-LMO found in this experiment was 0.96 and the sensitivity 0.73.

In vitro activities of polycationic peptides alone and in combination with clinically used antimicrobial agents against Rhodococcus equi

The in vitro activities of magainin II, nisin, and ranalexin alone and in combination with other antimicrobial agents against six clinical isolates of Rhodococcus equi were investigated by MIC and time-kill studies. All isolates were more susceptible to nisin. A positive interaction was observed when the peptides were combined with ampicillin, ceftriaxone, rifabutin, rifampin, azithromycin, clarithromycin, and vancomycin.

Disseminated Rhodococcus equi infection in two goats

Rhodococcus equi infection was diagnosed in two goats from the same herd. At necropsy, numerous caseating granulomas were disseminated throughout the liver, lungs, abdominal lymph nodes, medulla of right humerus, and the right fifth rib of goat No. 1, and the liver of goat No. 2. Histopathologic examination confirmed the presence of multiple caseating granulomas in these organs. Numerous gram-positive and Giemsa-positive coccobacilli were identified within the cytoplasm of macrophages. Aerobic bacterial cultures of the liver and lung from both goats yielded a pure growth of R. equi. R. equi antigens were immunohistochemically identified in caseating granulomas from both goats. However, the 15- to 17-kd virulence antigens of R. equi were not detected, suggesting possible infection by an avirulent strain of this organism.

Diversity of bacterial strains degrading hexadecane in relation to the mode of substrate uptake

The relative distribution of the modes of hydrocarbon uptake, used by bacteria of the environment for the degradation of long-chain alkanes, has been evaluated. The first mode of uptake, direct interfacial accession, involves contact of cells with hydrocarbon droplets. In the second mode, biosurfactant-mediated transfer, cell contact takes place with hydrocarbons emulsified or solubilized by biosurfactants. Sixty-one strains growing on hexadecane were isolated from polluted and non-polluted soils and identified. The majority (61%) belonged to the Corynebacterium-Mycobacterium-Nocardia group. Criteria selected for characterizing hexadecane uptake were cell hydrophobicity, interfacial and surface tensions and production of glycolipidic extracellular biosurfactants. These properties were determined in flask cultures on an insoluble (hexadecane) and on a soluble (glycerol or succinate) carbon source for a subset of 23 representative strains. Exclusive direct interfacial uptake was utilized by 47% of studied strains. A large proportion of strains (53%) produced biosurfactants. The data on cellular hydrophobicity suggested the existence of two distinct alkane transfer mechanisms in this group. Accordingly, tentative assignments of biosurfactant-mediated micellar transfer were made for 11% of the isolated strains, and of biosurfactant-enhanced interfacial uptake for 42%.

Pathogenicity of Rhodococcus equi strains possessing virulence-associated 15- to 17-kDa and 20-kDa antigens: experimental and natural cases in pigs

The pathogenic role of Rhodococcus equi in pigs remains controversial. Small numbers of pigs were inoculated intravenously (i.v.), or intramuscularly (i.m.) around the mouth, with a virulent, an intermediately virulent, or an avirulent strain of R. equi and killed 14 days later. None showed clinical signs other than transient fever and weight loss. The virulent and intermediately virulent strains were recovered in culture from various organs and lymph nodes of pigs inoculated i.v., but only from the mandibular lymph nodes of pigs inoculated i.m. The avirulent strain was not recovered from any site. None of the pigs developed macroscopically visible lesions, but they showed reactive hyperplasia of the mandibular lymph nodes. The latter contained scattered phagocytic cells, which were labelled immunohistochemically for virulence-associated antigens (15- to 17-kDa antigens or 20-kDa antigen). Intermediately virulent and virulent strains of R. equi were isolated from mandibular lymph nodes of 5.5% of apparently healthy abattoir pigs (n = 1615). Virulence-associated antigens were detected in phagocytic cells of culture-positive nodes, but the latter showed no lesions other than reactive lymphoid hyperplasia. The results would seem to question the pathogenic role of R. equi in pigs, and it is speculated that the organism survives in the lymph nodes without causing pathognomonic lesions.

Uncommon manifestations of opportunistic infections in an HIV infected patient

A case of an HIV infected patient complicated with Penicillium marneffei and Rhodococcus equi infection is reported. He presented with chronic ulcer as pyoderma gangrenosum-like on his right calf and submandibular lymphadenitis as scrofuloderma-like. Penicillium marneffei and Rhodococcus equi were isolated from the ulcer and lymph node respectively.

Rhodococcus equi and Nocardia brasiliensis infection of the brain and liver in a patient with acute nonlymphoblastic leukemia

Resolution of neutropenia is usually followed by resolution of fever in patients with febrile neutropenia. However, in some cases fever continues even when the patient is no longer neutropenic. Described here is a case of acute myeloblastic leukemia complicated by brain abscess, pulmonary nodules, and hepatic lesions. The patient's fever had continued after the neutropenia resolved; brain and hepatic cultures grew Rhodococcus equi and Nocardia brasiliensis. Although Rhodococcus infections occur frequently in patients with HIV infection, they are uncommon in patients with acute leukemia.