Rhodococcus equi infections of humans. 12 cases and a review of the literature

Isolation of vapB-positive Rhodococcus equi from submaxillary lymph nodes with or without granulomatous lesions in growing-finishing pigs in Japan

To investigate the etiological role of vapB-positive Rhodococcus equi in pigs, R. equi was isolated from the submaxillary lymph nodes with or without macroscopically detectable lesions of apparently healthy growing-finishing pigs at a slaughterhouse in Toyama Prefecture, Japan. R. equi was isolated from 57 (24.6%) of 232 pigs with macroscopically detectable lymph node lesions, and 56 (98.2%) of the 57 isolates were vapB-positive. R. equi was isolated from 10 (2.4%) of 420 pigs without lymph node lesions, and six (60%) of the 10 isolates were vapB-positive. Plasmid DNA was isolated from the 62 vapB-positive isolates and digested with EcoRI and NsiI to obtain the plasmid profile. Fifty-two (83.9%), three (4.8%), and four (6.5%) isolates contained pVAPB subtypes 1, 2, and 3, respectively, while the remaining three isolates were of pVAPB subtypes 9, 13, and 14, respectively. Twelve specimens from lymph nodes with macroscopically detectable lesions were randomly selected for histopathological staining. Granulomatous lesions resembling tuberculosis were found in 11 of the 12 specimens, and the remaining specimen showed typical foci of malakoplakia in the lymph node. The isolation rates of R. equi and vapB-positive R. equi from lymph nodes with macroscopically detectable lesions were significantly higher (P<0.05) than those of lymph nodes without lesions, suggesting an etiologic association between vapB-positive R. equi and macroscopically detectable granulomatous lesions in porcine submaxillary lymph nodes. Previous reports on the prevalence of vapB-positive R. equi in pigs are reviewed and discussed.

An elderly male with septic arthritis and bacteremia

Rhodococcus hoagii is a gram positive actinomycete found in horses and cattle. Humans can be infected by ingestion or inhalation through contaminated food or soil. The organism usually infects immunosuppressed hosts with pneumonia being the common presentation. We present a case of an 89 years old, apparently immunocompetent host presenting with fever, encephalopathy and arthritis who grew Rhodococcus hoagii in blood and synovial fluid, The patient responded well to a combination of vancomycin, azithromycin and imipenem-cilastatin. Our case demonstrates that extra-pulmonary manifestations such as septic arthritis and bacteremia can be seen in immune competent hosts.

Disseminated Rhodococcus equi infection in a patient with diffuse large B-cell lymphoma treated with immunotherapy

Immunotherapies can lead to an immune compromised state that can allow for opportunistic pathogens such as Rhodococcus to flourish. The vast majority of Rhodococcus infections occur in immunocompromised hosts. Here we describe disseminated Rhodococcus equi infection in a patient with diffuse large B-cell lymphoma treated with immunotherapy. Infection with Rhodococcus can be diagnosed with the aid of cytomorphology and histochemical findings and the organism confirmed by sequencing. In conclusion, Rhodococcus should be considered in the differential of granulomatous inflammation in immunocompromised individuals treated with immunotherapies.

Rhodococcus infection: a 10-year retrospective analysis of clinical experience and antimicrobial susceptibility profile

Rhodococcus equi is an opportunistic pathogen known to cause pulmonary and extrapulmonary disease among immunocompromised patients. Treatment is frequently challenging due to intrinsic resistance to multiple antibiotic classes. While non-equi Rhodococcus spp. are prevalent, their clinical significance is poorly defined. There is also limited data on antibiotic susceptibility testing (AST) of Rhodococcus infection in humans. We conducted a single-center, retrospective cohort study evaluating clinical characteristics, microbiologic profile, and AST of Rhodococcus infections between June 2012 and 2022 at our tertiary academic medical center. Identification of Rhodococcus spp. was performed by Sanger 16S rRNA gene sequencing and/or matrix-assisted laser desorption ionization-time of flight mass spectrometry, and AST was performed by agar dilution. Three hundred twenty-two isolates of Rhodococcus spp. were identified from blood (50%), pulmonary (26%), and bone/joint (12%) sources. R. equi/hoagii, R. corynebacterioides, and R. erythropolis were the most frequently isolated species, with 19% of isolates identified only to genus level. One hundred ninety-nine isolates evaluated for AST demonstrated high-level resistance to amoxicillin/clavulanate, cephalosporins, and aminoglycosides. More than 95% susceptibility to imipenem, vancomycin, linezolid, rifampin, and clarithromycin was observed. Non-equi species showed a significantly more favorable AST profile relative to R. equi. Clinically significant Rhodococcus infection was rare with 10 cases diagnosed (majority due to R. equi) and managed. The majority of patients received 2- or 3-drug combination therapy for 2-6 months, with favorable clinical response. Significant differences in AST were observed between R. equi and non-equi species. Despite high antimicrobial resistance to several antibiotic classes, imipenem and vancomycin remain appropriate empiric treatment options for R. equi. Future research evaluating mechanisms underlying antimicrobial resistance is warranted.

Antimicrobial Residue Accumulation Contributes to Higher Levels of Rhodococcus equi Carrying Resistance Genes in the Environment of Horse-Breeding Farms

Antimicrobial residues excreted in the environment following antimicrobial treatment enhance resistant microbial communities in the environment and have long-term effects on the selection and maintenance of antimicrobial resistance genes (AMRGs). In this study, we focused on understanding the impact of antimicrobial use on antimicrobial residue pollution and antimicrobial resistance (AMR) in the environment of horse-breeding farms. Rhodococcus equi is an ideal microbe to study these associations because it lives naturally in the soil, exchanges AMRGs with other bacteria in the environment, and can cause disease in animals and humans. The environment is the main source of R. equi infections in foals; therefore, higher levels of multidrug-resistant (MDR) R. equi in the environment contribute to clinical infections with MDR R. equi. We found that macrolide residues in the environment of horse-breeding farms and the use of thoracic ultrasonographic screening (TUS) for early detection of subclinically affected foals with R. equi infections were strongly associated with the presence of R. equi carrying AMRGs in the soil. Our findings indicate that the use of TUS contributed to historically higher antimicrobial use in foals, leading to the accumulation of antimicrobial residues in the environment and enhancing MDR R. equi.

Nadir Bir Etken: Rhodococcus equi, İmmunkompetan Hastalarda Yumuşak Doku Enfeksiyonlarına İlişkin Bir Vaka Sunumu ve Literatür İncelemesi

Rhodococcus equi is a microorganism that was first described in horses and later it had been found out to cause opportunistic infections in immunosuppressed patients. It causes especially pulmonary infections in immunocompromised patients while it rarely causes diseases such as septic arthritis and soft tissue infections. It is important to question epidemiological risk factors for the diagnosis of the disease. Also the clinician-microbiologist relationship is important in the laboratory diagnosis of the microorganism because it is possible to be missed as the part of normal flora or contaminant or to be confused with microorganisms with similar phenotypic features (Nocardia species or rapidly growing mycobacteria). Rarely, it has been reported in immunocompetent patients, as in our case. MEDLINE, SCOPUS, Google Scholar, and Cochrane searches were performed using keywords Rhodococcus equi and Corynebacterium equi from 1945 to July 2021. A total of 582 articles were determined. Articles containing these keywords were then scanned for words "humans", “soft tissue infections”, and “cellulite” and a total of 42 articles were listed in the end. A total of 14 case reports of soft tissue infection/cellulitis in immunocompetent patients related R. equi were detected in the literature In our case, there was a soft tissue infection and R. equi was detected in the abscess culture. Obtaining culture and determining the factor is very important in the treatment of infections. In this report, soft tissue infections caused by R. equi in immunocompetent patients are reviewed.

Chronic Cavitary Infections Other than Tuberculosis: Clinical Aspects

Lung cavitation may be due to infectious or noninfectious pathologic processes. The latter category includes nonmalignant conditions, such as granulomatosis with polyangiitis, and malignant conditions, such as squamous cell carcinoma of the lung. Infectious etiologies that produce lung cavitation usually cause chronic illness, although some, particularly pyogenic bacteria, may produce acute cavitary disease. Tuberculosis is the most common cause of chronic pulmonary infection with cavitation. The goal of this review was to highlight a selection of the better-known infectious agents, other than tuberculosis, that can cause chronic lung disease with cavitation. Emphasis is placed on the following organisms: nontuberculous mycobacteria, Histoplasma, Blastomyces, Coccidioides, Paracoccidioides, Aspergillus, Burkholderia pseudomallei, Paragonimus westermani, and Rhodococcus equi. These organisms generally produce clinical features and radiologic findings that overlap or mimic those of tuberculosis. In a companion article, we have further emphasized aspects of the same conditions that are more pertinent to radiologists.

Chronic cavitary pneumonia by Rhodococcus equi in a highly prevalent tuberculosis country: a diagnosis challenge

Rhodococcus equi is a facultative aerobic, intracellular, non-motile, non-spore-forming, Gram-positive, weakly acid-fast coccobacillus belonging to the group of nocardioform actinomycetes. R. equi infections are rare opportunistic illnesses in patients with Acquired Immunodeficiency Syndrome (AIDS), associated with a high mortality rate. The most common clinical presentation of R. equi infections is a chronic cavitary pneumonia. Due to its acid-fastness, R. equi can be mistaken for others acid-fast organisms, as Mycobacterium tuberculosis. In turn, R. equi is also a gram-positive pleomorphic bacteria and can be mistaken for diphtheroids or Micrococcus organisms, being accidentally disregarded as oral contaminants in sputum cultures. Therefore, in Brazil, a highly prevalent tuberculosis (TB) country, pulmonary infections caused by R. equi may mimic pulmonary TB and represent a diagnostic challenge. Here, we report on a case of chronic cavitary pneumonia by R. equi in a Human Immunodeficiency Virus (HIV)-infected patient, focusing on diagnostic aspects.

Current taxonomy of Rhodococcus species and their role in infections

Rhodococcus is a genus of obligate aerobic, Gram-positive, partially acid-fast, catalase-positive, non-motile, and none-endospore bacteria. The genus Rhodococcus was first introduced by Zopf. This bacterium can be isolated from various sources of the environment and can grow well in non-selective medium. A large number of phenotypic characterizations are used to compare different species of the genus Rhodococcus, and these tests are not suitable for accurate identification at the genus and species level. Among nucleic acid-based methods, the most powerful target gene for revealing reliable phylogenetic relationships is 16S ribosomal RNA gene (16S rRNA gene) sequence analysis, but this gene is unable to differentiation some of Rhodococcus species. To date, whole genome sequencing analysis has solved taxonomic complexities in this genus. Rhodococcus equi is the major cause of foal pneumonia, and its implication in human health is related to cases in immunocompromised patients. Macrolide family together with rifampicin is one of the most effective antibiotic agents for treatment rhodococcal infections.

Diagnosis and management of pulmonary infection due to Rhodococcus equi

BACKGROUND

Rhodococcus equi is a recognized cause of disease in humans, especially in individuals who are immunocompromised. Because diphtheroids are regarded as part of normal respiratory flora, the importance of R. equi as a pulmonary pathogen may not be fully appreciated and its prevalence may be underestimated. Most treatment recommendations for R. equi infection were established before antiretroviral drugs became available for human immunodeficiency virus/AIDS therapy, and therapeutic strategies may need to be updated.

OBJECTIVES

To review the role of R. equi as a cause of pulmonary infection; to highlight its importance for clinicians and microbiologists; and to challenge current approaches to treatment, whether in immunodeficient or immunocompetent individuals.

SOURCES

A PubMed search using combinations of the following terms: 'Rhodococcus (automatically including Corynebacterium) equi' AND 'pneumonia' OR 'pulmonary' infection, then cross-checking references in the resulting cases, case series and reviews.

CONTENT

We provide a review that details the challenges in the diagnosis, microbiology and pathogenesis of pulmonary infection caused by R. equi and the options for treatment.

IMPLICATIONS

Ten to 14 days of treatment may be effective for pneumonia due to R. equi. Our review suggests that longer courses of therapy are needed for cavitary lesions and lung masses. However, recommendations for excessively prolonged treatment of all pulmonary infections arose during a time when many cases occurred in individuals with AIDS and before effective antiretroviral therapy was available. We suggest that the rationale for prolonged therapy with multiple antibiotics needs to be re-evaluated.

Identification of Mycobacterium species and Rhodococcus equi in peccary lymph nodes

Mycobacterium species and the virulence-associated proteins (vapA, vapB, and vapN genes) of Rhodococcus equi isolated from 330 lymph nodes of collared peccaries (Tayassu tajacu) and white-lipped peccaries (Tayassu pecari) intended for human consumption were investigated. Thirty-six (10.9%) R. equi strains were isolated; 3.3% (n = 11/330) were from white-lipped peccary lymph nodes, and 7.6% (25/330) were from collared peccary lymph nodes. Among the 11 isolates of R. equi from the white-lipped peccaries, 90.9% (n = 10/11) were obtained from the mesenteric lymph nodes, and only 9.1% (n = 1/10) were obtained from the mediastinal lymph nodes. In the 25 isolates of R. equi obtained from the collared peccaries, 40.0% (n = 10/25) were recovered from the mesenteric lymph nodes, 36% (n = 9/25) from the submandibular lymph nodes, and 24.0% (n = 6/25) from the mediastinal lymph nodes. No vapA, vapB, or vapN genes (plasmidless) or three host-associated types (pVAPA, pVAPB, and pVAPN) were identified among the R. equi isolates. Mycobacterium species were isolated in 3.03% (n = 10/330) of all the lymph nodes analyzed. Among the 10 mycobacterial isolates, 60% (n = 6/10) were from the white-lipped peccary lymph nodes, and 40% (n = 4/10) were from the collared peccary lymph nodes. Ten Mycobacterium species were detected by PCR-PRA with a predominance of M. avium type 1. Sequencing of the hsp65 and rpob genes revealed mycobacteria that were saprophytic (M. sinense and M. kumamotonense) and potentially pathogenic (M. colombiense and M. intracellulare) to humans and animals. To our knowledge, this is the first description of R. equi and/or mycobacterial species identified in the lymph nodes of peccary specimens. R. equi (plasmidless) and the mycobacterial species described here have been reported as causes of pulmonary and extrapulmonary infections in both immunocompetent and immunocompromised humans.

Induction of Reactive Intermediates and Autophagy-Related Proteins upon Infection of Macrophages with Rhodococcus equi

Rhodococcus equi (R. equi) is an intracellular macrophage-tropic pathogen with potential for causing fatal pyogranulomatous pneumonia in foals between 1 and 6 months of age. In this study, we sought to determine whether infection of macrophages with R. equi could lead to the induction of autophagy. Murine bone marrow derived macrophages (BMDM) were infected with R. equi for various time intervals and analyzed for upregulation of autophagy proteins and accumulation of autophagosomes relative to uninfected controls. Western blot analysis showed a progressive increase in LC3-II and Beclin1 levels in a time-dependent manner. The functional accumulation of autophagosomes detected with monodansylcadaverine further supported the enhanced induction of autophagy in BMDM infected with R. equi. In addition, infection of BMDM with R. equi induced generation of reactive oxygen species (ROS) in a time-dependent manner. These data are consistent with reports documenting the role of ROS in induction of autophagy and indicate that the infection of macrophages by R. equi elicits innate host defense mechanisms.

[Respiratory infections caused by slow-growing bacteria: Nocardia, Actinomyces, Rhodococcus]

INTRODUCTION

Pneumonia caused by slow-growing bacteria is rare but sometimes severe.

STATE OF THE ART

These infections share many similarities such as several differential diagnoses, difficulties to identify the pathogen, the importance of involving the microbiologist in the diagnostic investigation and the need for prolonged antibiotic treatment. However, major differences distinguish them: Nocardia and Rhodococcus infect mainly immunocompromised patients while actinomycosis also concerns immunocompetent patients; the severity of nocardioses is related to their hematogenous spread while locoregional extension by contiguity makes the gravity of actinomycosis.

PROSPECTIVE

For these diseases, molecular diagnostic tools are essential, either to obtain a species identification and guide treatment in the case of nocardiosis or to confirm the diagnosis from a biological sample. Treatment of these infections is complex due to: (1) the limited data in the literature; (2) the need for prolonged treatment of several months; (3) the management of toxicities and drug interactions for the treatment of Nocardia and Rhodococcus.

CONCLUSION

Close cooperation between pneumonologists, infectious disease specialists and microbiologists is essential for the management of these patients.

Differences in Rhodococcus equi Infections Based on Immune Status and Antibiotic Susceptibility of Clinical Isolates in a Case Series of 12 Patients and Cases in the Literature

Rhodococcus equi is an unusual zoonotic pathogen that can cause life-threatening diseases in susceptible hosts. Twelve patients with R. equi infection in Kentucky were compared to 137 cases reported in the literature. Although lungs were the primary sites of infection in immunocompromised patients, extrapulmonary involvement only was more common in immunocompetent patients (P < 0.0001). Mortality in R. equi-infected HIV patients was lower in the HAART era (8%) than in pre-HAART era (56%) (P < 0.0001), suggesting that HAART improves prognosis in these patients. Most (85–100%) of clinical isolates were susceptible to vancomycin, clarithromycin, rifampin, aminoglycosides, ciprofloxacin, and imipenem. Interestingly, there was a marked difference in susceptibility of the isolates to cotrimoxazole between Europe (35/76) and the US (15/15) (P < 0.0001). Empiric treatment of R. equi infection should include a combination of two antibiotics, preferably selected from vancomycin, imipenem, clarithromycin/azithromycin, ciprofloxacin, rifampin, or cotrimoxazole. Local antibiograms should be checked prior to using cotrimoxazole due to developing resistance.

A Case of Recurrent Meningitis Caused by Rhodococcus species Successfully Treated with Antibiotic Treatment and Intrathecal Injection of Vancomycin through an Ommaya Reservoir

Human infection by Rhodococcus species is rare and mostly limited to immunocompromised hosts such as patients infected with the human immunodeficiency virus (HIV) or organ transplant recipients. The most common strain is R. equi, and the most common clinical presentation is pulmonary infection, reported in 80% of Rhodococcus spp. infections. The central nervous system is an uncommon infection site. We report a case of a patient with pneumonia, brain abscess, and recurrent meningitis caused by Rhodococcus spp. He initially presented with pneumonia with necrosis, which progressed to brain abscess and recurrent meningitis. Rhodococcus spp. was identified from the cerobrospinal fluid (CSF) collected during his fourth hospital admission. Despite prolonged treatment with appropriate antibiotics, meningitis recurred three times. Finally, in order to administer antibiotics directly into the CSF and bypass the blood-brain barrier, an Ommaya reservoir was inserted for administration of 90 days of intrathecal vancomycin and amikacin in conjunction with intravenous and oral antibiotics; the patient was finally cured with this treatment regimen.

Rhodococcus equi peritonitis in continuous ambulatory peritoneal dialysis: a first in Australia

A 33-year-old Caucasian man with end-stage renal disease secondary to biopsy-proven IgA nephropathy, managed with continuous ambulatory peritoneal dialysis (PD), presented with PD-related peritonitis, the causal organism being a non-branching Gram-positive bacillus, Rhodococcus equi. Initial empirical Gram positive and negative coverage with cefazolin and ceftazidime was unsuccessful, but following isolation of the organism, and conversion to intraperitoneal vancomycin and oral ciprofloxacin, the peritonitis episode resolved. At day 10, vancomycin was switched to azithromycin for a total of 6 weeks of antimicrobial therapy. The PD catheter was preserved, and the patient remained peritonitis-free at 6 months of follow-up.

Rhodococcus equi Sepsis in a Renal Transplant Recipient: A Case Study

Rhodococcus equi is an unusual cause of infection in humans, but has emerged as an opportunistic pathogen among immunocompromised patients. Primary pulmonary involvement is the most common clinical presentation, although the spectrum of disease is broad. Diagnosing R. equi infections remains challenging, both from clinical and microbiological view, and no standard treatment has been established. In this report, we present a detailed case of a 57-year-old male renal transplant recipient who developed R. equi bacteremia with a concomitant Pneumocystis jirovecii pneumonia. We describe the clinical features of R. equi infections, highlight the importance of an early diagnosis, and briefly review treatment options for this rare infection.

Cerebral pathology post heart transplantation

Cerebral pathology is frequently encountered post heart transplantation with a cumulative incidence of about 80% after 15 years. A broad spectrum of disease entities is reported, from minor abnormalities to life-threatening diseases. Although cerebral infections and malignancies are rare in this patient population, they have a high mortality rate. Since 1991, 171 orthotopic heart transplantations were performed at the Ghent University Hospital with a 10-year survival rate of 75%. Severe cerebral complications occurred in 10 patients, with epilepsy in 2 patients, cerebrovascular accidents in 4 patients, cerebral infections in 3 patients and a cerebral malignancy in 1 patient, resulting in a fatal outcome in 7 patients. We present four of these cases.

Diagnosing Rhodococcus equi infections in a setting where tuberculosis is highly endemic: a double challenge

Rhodococcus equi infection is increasing in regions with high HIV prevalence worldwide. The microbiological features and clinical mimicry of tuberculosis infection pose diagnostic challenges in high-tuberculosis-incidence settings. We present two HIV-associated cases of R. equi infection from Vietnam and discuss the unique diagnostic challenges in such settings.

Misidentification of Mycobacterium fortuitum in an immunocompetent patient presenting with a unilateral neck mass

A 31-year-old African man with a blameless medical history presented with an enlarging neck swelling of 6 months duration. He was systemically well with normal heamatobiochemistry. MRI of the neck demonstrated abnormal signalling in the subcutaneous fat overlying the posterior spinal muscles in the midline and the left sternocleidomastoid muscle. Scanty growth of Rhodococcus equi was reported from a turbid fine needle aspirate of the neck on two separate occasions. The swelling progressed despite numerous antibiotic combinations which necessitated surgical debridement. Analysis of debrided tissue using 16S rDNA surprisingly identified Mycobacterium fortuitum, not R equi, thereby resolving our diagnostic conundrum.

Rhodococcus equi Pericarditis in a Patient Living with HIV/AIDS

Introduction:

Rhodococcus equi, previously called Corynebacterium equi, is known to cause pneumonia in foals and swine. Although it was known to cause infection rarely in humans, R equi infection in humans has increased with the advent of HIV and increased use of immunosuppressants.

Case:

We report a case of a 48-year-old male patient with newly diagnosed HIV/AIDS presenting with recurrent R equi bacteremia, pericardial effusion, and pericardial cyst. The infection was treated with drainage of the pericardial effusion and cyst and 2 weeks of intravenous vancomycin and 6 months of oral azithromycin and levofloxacin.

Discussion:

Rhodococcus equi causes pericarditis and pericardial effusion. It can be effectively treated with debridement, drainage, and a prolonged course of antibiotics. In vitro antibiotic susceptibility should be checked as resistance to antibiotics can develop, especially if drainage is inadequate.

Rhodococcus equi granulomatous mastitis in an immunocompetent patient

A 37-year-old immunocompetent woman was evaluated for progressive swelling of her left breast. Magnetic resonance imaging (MRI) showed multiple hypo-intense solid lesions and could not exclude breast cancer. Tissue biopsy was suggestive of granulomatous mastitis without any evidence of malignancy. Culture of the specimen in brain heart infusion broth grew Rhodococcus equi. The patient responded well to combination therapy with ciprofloxacin and azithromycin, and the lesions regressed in follow-up MRI. To the best of our knowledge, this is the first report of R. equi granulomatous mastitis. Accurate identification of this rare pathogen is necessary to provide appropriate treatment in granulomatous mastitis.

Other HIV-associated pneumonias

The incidence, mortality, and epidemiology of human immunodeficiency virus (HIV)-associated pulmonary infections have changed as a result of effective antiretroviral and prophylaxis antimicrobial therapy. The clinical presentation, radiographic abnormalities, and treatment of pneumonia from various uncommon pathogens in patients with AIDS can be different from those in immunocompetent patients. Advances in invasive and noninvasive testing and molecular biological techniques have improved the diagnosis and prognosis of pulmonary infections in patients infected with HIV. This review focuses on pulmonary infections from nontuberculosis mycobacteria, cytomegalovirus, fungi (aspergillosis, cryptococcosis, endemic fungi), and parasites (toxoplasmosis), and uncommon bacterial pneumonia (nocardiosis, rhodococcosis) in these patients.

A 39-year-old man with fevers, cough, and right upper lobe cavitory lesion in lung

In this case report, we present a patient who had an endobronchial lesion that was found to be caused by Rhodococcus equi, earlier known as corynebacterium. Although this organism has been reported to infect immunocompromised patients, including several patients with acquired immune deficiency syndrome, it has rarely been reported to present as an endobronchial lesion.

[Bacterial pneumonia in HIV-infected patients (excluding mycobacterial infection)]

Respiratory infections are the most common complications in HIV patients, regardless of the degree of immunosuppression. Even though antiretroviral therapy has a protective effect on the risk of bacterial pneumonia, this still remains high (including those with CD(4)>500/mm(3)). The most frequently isolated bacteria are Streptococcus pneumoniae and Haemophilus influenzae. The clinical and radiological presentations of lower respiratory tract infections in HIV patients are quite variable. The clinical presentation is more severe and the radiological presentation is more atypical if the immunosuppression is severe. The first-line antibiotic therapy is an injectable third-generation cephalosporin (ceftriaxone or cefotaxime) or co-amoxiclav. Pneumococcal vaccination (as well as influenza vaccine) is recommended. Although rare, Nocardia spp. and Rhodococcus equi seem more common among AIDS patients.

Rhodococcus bacteremia in cancer patients is mostly catheter related and associated with biofilm formation

Rhodococcus is an emerging cause of opportunistic infection in immunocompromised patients, most commonly causing cavitary pneumonia. It has rarely been reported as a cause of isolated bacteremia. However, the relationship between bacteremia and central venous catheter is unknown. Between 2002 and 2010, the characteristics and outcomes of seventeen cancer patients with Rhodococcus bacteremia and indwelling central venous catheters were evaluated. Rhodococcus bacteremias were for the most part (94%) central line-associated bloodstream infection (CLABSI). Most of the bacteremia isolates were Rhodococcus equi (82%). Rhodococcus isolates formed heavy microbial biofilm on the surface of polyurethane catheters, which was reduced completely or partially by antimicrobial lock solution. All CLABSI patients had successful response to catheter removal and antimicrobial therapy. Rhodococcus species should be added to the list of biofilm forming organisms in immunocompromised hosts and most of the Rhodococcus bacteremias in cancer patients are central line associated.

Disseminated Rhodococcus equi infection in HIV infection despite highly active antiretroviral therapy

BACKGROUND

Rhodococcus equi (R.equi) is an acid fast, GRAM + coccobacillus, which is widespread in the soil and causes pulmonary and extrapulmonary infections in immunocompromised people. In the context of HIV infection, R.equi infection (rhodococcosis) is regarded as an opportunistic disease, and its outcome is influenced by highly active antiretroviral therapy (HAART).

CASE PRESENTATION

We report two cases of HIV-related rhodococcosis that disseminated despite suppressive HAART and anti-rhodococcal treatment; in both cases there was no immunological recovery, with CD4+ cells count below 200/μL. In the first case, pulmonary rhodococcosis presented 6 months after initiation of HAART, and was followed by an extracerebral intracranial and a cerebral rhodococcal abscess 1 and 8 months, respectively, after onset of pulmonary infection. The second case was characterized by a protracted course with spread of infection to various organs, including subcutaneous tissue, skin, colon and other intra-abdominal tissues, and central nervous system; the spread started 4 years after clinical resolution of a first pulmonary manifestation and progressed over a period of 2 years.

CONCLUSIONS

Our report highlights the importance of an effective immune recovery, despite fully suppressive HAART, along with anti-rhodococcal therapy, in order to clear rhodococcal infection.

Short report: Identification of virulence-associated plasmids in Rhodococcus equi in humans with and without acquired immunodeficiency syndrome in Brazil

Virulence of Rhodococcus equi strains from 20 humans in Brazil was investigated by using a polymerase chain reaction to characterize isolates as virulent (VapA), intermediately virulent (VapB), and avirulent. Nine isolates were obtained from human immunodeficiency virus (HIV)-positive patients, six from HIV-negative patients, and five from patients of unknown status. Five isolates were VapB positive, four were VapA positive, and eleven were avirulent. Among the nine isolates from HIV-positive patients, five contained VapB plasmids and two contained VapA plasmids. Five VapB-positive isolates had the type 8 virulence plasmid. Eleven of the patients had a history of contact with livestock and/or a farm environment, and none had contact with pigs.

Rhodococcus equi venous catheter infection: a case report and review of the literature

Introduction

Rhodococcus equi is an animal pathogen that was initially isolated from horses and is being increasingly reported as a cause of infection in humans with impaired cellular immunity. However, this pathogen is underestimated as a challenging antagonist and is frequently considered to be a mere contaminant despite the potential for life-threatening infections. Most case reports have occurred in immunocompromised patients who have received organ transplants (for example kidney, heart, bone marrow) or those with human immunodeficiency virus infection. Infections often manifest as pulmonary involvement or soft tissue abscesses. Bacteremia related to R. equi infections of tunneled central venous catheters has rarely been described.

Case presentation

We report the case of a 63-year-old non-transplant recipient, non-HIV infected Caucasian woman with endometrial carcinoma who developed recurrent bloodstream infections and septic shock due to R. equi and ultimately required the removal of her port catheter, a subcutaneous implantable central venous catheter. We also review the medical literature related to human infections with R. equi.

Conclusion

R. equi should be considered a serious pathogen, not a contaminant, particularly in an immunocompromised patient who presents with a central venous catheter-related bloodstream infection. Counseling patients with central venous catheters who participate in activities involving exposure to domesticated animals is recommended.

Nonhealing wound due to Rhodococcus equi in an apparently immunocompetent patient, revealing CD8+ T-lymphocyte deficiency

We describe a case of a nonhealing wound due to Rhodococcus equi. Failure of the wound to heal led to immunological investigations and the discovery of a previously unknown CD8+ T-lymphocyte deficit responsible for the chronic infection. The infection was cured after a 3-month course of a combination of antibiotics.

Invasive infection with Rhodococcus equi--two case reports and review of literature

Rhodococcus equi infection is rare in humans, but has increasingly been reported in the last three decades, particularly in immunocompromised patients. The infection is mainly pulmonary but can also assume an extra-pulmonary form. R. equi infection is difficult to diagnose at an early stage both from a clinical and microbiologic view. Only correct and timely diagnosis and treatment can help reduce significant morbidity and mortality. Optimal treatment probably consists of prolonged, preferably triple combination therapy, including vancomycin, with optimization of pharmacokinetic parameters and screening for drug interactions, when indicated. Two clinical cases of invasive R. equi infection are reported in this manuscript: a pulmonary form and an extra-pulmonary form with brain abscesses, both in immunocompromised patients, with detailed description of symptoms, analysis, treatment, and outcome.

LINFADENITE INFECCIOSA EM SUÍNOS: ETIOLOGIA, EPIDEMIOLOGIA E ASPECTOS EM SAÚDE PÚBLICA

RESUMO A linfadenite infecciosa em suínos gera altos prejuízos com a condenação de carcaças, pela similaridade das lesões causadas pelos agentes causais e de certos micro-organismos, reforçando a necessidade da vigilância sanitária continuada nas afecções de linfonodos em suínos. O crescente isolamento de Mycobacterium sp. e de Rhodococcus equi em pacientes acometidos pela síndrome da imunodeficiência adquirida (Aids) redobrou a preocupação na vigilância da linfadenite na linha de abate, em virtude destes micro-organismos figurarem dentre as principais causas da linfadenite em suínos. O presente artigo revisou os principais aspectos da linfadenite infecciosa em suínos, com ênfase na epidemiologia e reflexos em saúde pública, e a ocorrência de Mycobacterium sp. e R. equi como agentes causais da linfadenite.

Malacoplakia of the tongue: a case report and clinicopathologic review of 6 cases

BACKGROUND

Extra-urogenital tract malacoplakia is uncommon, with tongue malacoplakia being exceptionally rare. The nonspecific clinical presentation and variable histologic patterns can make recognition of this lesion and separation from other lesions challenging. There are only a few reported cases in the English literature.

MATERIALS AND METHODS

Five case reports of tongue malacoplakia were compiled from the literature (MedLine 1960-2008) and integrated with this case report.

RESULTS

The patients included 4 males and 2 females, ranging in age from 9 to 98 years (mean, 64 years). Patients presented with difficulty swallowing, foreign body sensation, a mass lesion, or referred pain (neck or ear). Symptoms were present from a few days up to 18 months. The base of the tongue was the most frequent site, although midline tongue and half of the tongue were also affected. Radiographic studies demonstrated a mass, with a single lesion showing positron emission tomography positivity. Two patients had previous cancers (prostate and colorectal; larynx). This case report was a farm hand for horses, with gram-negative rods, suggestive of Rhodococcus equi identified. The lesions were 1 to 2 cm in greatest dimension. Histologically, there is pseudoepitheliomatous hyperplasia or ulceration with a heavy acute and chronic inflammatory infiltrate. The subepithelial spaces are completely filled with eosinophilic histiocytes, most of which contain granular material in their cytoplasm. Well-formed, blue, calcific bodies are noted, a few showing a "targetoid appearance" and concentric lamination. These Michaelis-Gutmann bodies are positive with von Kossa, iron, and periodic acid-Schiff stains. These findings support a diagnosis of malacoplakia. The differential diagnosis includes granular cell tumor, poorly differentiated carcinoma, and Langerhans histiocytosis. Patients are managed with antibiotic therapy and excision.

CONCLUSIONS

Tongue malacoplakia is rare, often presenting as a mass lesion. Histologic recognition of this abnormal phagocytic disorder will prevent potentially disfiguring surgery.

RHODOCOCCUS EQUI

RESUMO Rhodococcus equi é uma importante causa de broncopneumonia em potros com menos de seis meses de idade, sendo responsável pela mortalidade de eqüinos no mundo inteiro. É um microrganismo intracelular capaz de sobreviver e se multiplicar no interior de macrófagos. Apresenta três níveis de virulência de acordo com os diferentes antígenos expressos em sua superfície. Cepas virulentas apresentam um plasmídeo que codifica a proteína de superfície VapA e são isoladas principalmente de potros com pneumonia e de alguns pacientes humanos. Cepas com virulência intermediária expressam a proteína VapB e predominam em suínos e humanos com AIDS. Cepas avirulentas não expressam antígenos de superfície e são encontradas principalmente no ambiente e em pacientes humanos. Um dos fatores responsáveis pela ampla distribuição da enfermidade em potros é a imaturidade do sistema imunológico dos animais acometidos pela infecção, que pode se tornar endêmica em alguns criatórios. Em humanos, as formas de infecção são ainda desconhecidas, mas o contato com eqüinos é relatado em um terço dos casos. Devido à importância clínica da doença, são necessários métodos diagnósticos que promovam sua identificação precoce, facilitando e aumentando as chances de sucesso com o tratamento. Os métodos mais utilizados atualmente são o cultivo microbiológico, testes sorológicos para detecção de anticorpos séricos nos animais e técnicas de PCR que detectam a região 16S do rDNA e o fragmento do gene vapA do microrganismo.

Cavitary pulmonary disease

A pulmonary cavity is a gas-filled area of the lung in the center of a nodule or area of consolidation and may be clinically observed by use of plain chest radiography or computed tomography. Cavities are present in a wide variety of infectious and noninfectious processes. This review discusses the differential diagnosis of pathological processes associated with lung cavities, focusing on infections associated with lung cavities. The goal is to provide the clinician and clinical microbiologist with an overview of the diseases most commonly associated with lung cavities, with attention to the epidemiology and clinical characteristics of the host.

Recurrent Rhodococcus equi infection with fatal outcome in an immunocompetent patient

The majority of human Rhodococcus equi infections occur in immunocompromised hosts, especially those with AIDS, and infection in immunocompetent patients is rare. Reported here is a case of R. equi infection in a seemingly healthy patient with a very complicated course. Despite neurosurgery and prolonged antibiotic therapy the patient deceased.

[Rhodococcus equi infection]

<zakljucak> Humana R. equi infekcija jos uvek je retko oboljenje koje se javlja uglavnom kod osoba sa teskim stepenom imunodeficijencije. Najcesce se ispoljava u vidu subakutne bakterijske pneumonije sa kavitacijama, a karakterise se cestim recidivima, bakterijemijama i visokom stopom mortaliteta. Terapija R. equi infekcije bazira se na kombinaciji baktericidnih i antibiotika sa dobrom intracelijskom penetracijom koji se primenjuju u duzem periodu, dok su drenaza apscesnih kolekcija i/ili operativni zahvati indikovani samo u slucajevima izostanka adekvatnog odgovora na antibiotsku terapiju. Uzimajuci u obzir cinjenicu da je R. equi infekciju veoma tesko eradikovati, a u cilju sto ranijeg postavljanja prave dijagnoze i blagovremenog pocetka adekvatne terapije, od velikog znacaja je poznanje najvaznijih karakteristika ove bolesti.

Chilling and cultivar type affect the diversity of bacterial endophytes colonizing sweet pepper (Capsicum anuumL.)

A climate chamber experiment was conducted to assay the effect of low temperatures (chilling) on the diversity of bacteria colonizing the endospheres of two thermophilic sweet pepper (Capsicum anuum L.) cultivars, Milder Spiral and Ziegenhorn Bello. Structural diversity was analyzed by 16S rRNA-based terminal restriction fragment length polymorphism (T-RFLP) analysis and by the generation of 16S rRNA gene libraries to determine dominant community members in T-RFLP profiles. Cultivable community members colonizing lines Milder Spiral and Ziegenhorn Bello were identified by 16S rRNA gene analysis. T-RFLP profiles and 16S rRNA gene libraries revealed a high heterogeneity of community composition due to chilling and suggested further the existence of cultivar-specific communities. The majority of isolates obtained from the cultivar Milder Spiral were assigned as high-G+C Gram-positive bacteria (Microbacterium sp., Micrococcus sp., Rhodococcus sp.) and Firmicutes (Staphylococcus sp.). Of the isolated endophytes obtained from cultivar Zeigenhorn Bello, 93% were affiliated with Staphylococcus aureus and Bacillus sp. (Firmicutes). The experimental set-up was suited to demonstrate that chilling and cultivar type can influence the diversity of bacterial endophytes colonizing sweet pepper. We propose additional chilling experiments to investigate the effect of chilling on functional, plant-beneficial abilities of bacterial endophytes associated with low-temperature-sensitive crops, such as sweet pepper.Key words: chilling, thermophilic sweet pepper, bacterial endophyte diversity, 16S rRNA gene analysis.