Rhodococcus equi and cytomegalovirus pneumonia in a renal transplant patient: diagnosis by fine-needle aspiration biopsy

Specific preadaptations of Rhodococcus equi cooperate with its Virulence-associated protein A during macrophage infection

Gram-positive Rhodococcus equi (Prescotella equi) is a lung pathogen of foals and immunocompromised humans. Intra-macrophage multiplication requires production of the bacterial Virulence-associated protein A (VapA) which is released into the phagosome lumen. VapA pH-neutralizes intracellular compartments allowing R. equi to multiply in an atypical macrophage phagolysosome. Here, we show that VapA does not support intra-macrophage growth of several other bacterial species demonstrating that only few bacteria have the specific preadaptations needed to profit from VapA. We show that the closest relative of R. equi, environmental Rhodococcus defluvii (Prescotella defluvii), does not multiply in macrophages at 37°C even when VapA is present because of its thermosensitivity but it does so once the infection temperature is lowered providing rare experimental evidence for 'thermal restriction'. Using growth experiments with isolated macrophage lysosomes and modified infection schemes we provide evidence that R. equi resists the attack by phagolysosome contents at low pH for several hours. During this time, R. equi produces and secretes VapA which enables it to grow at the expense of lysosome constituents. We present arguments that, under natural infection conditions, R. equi is VapA-less during the initial encounter with the host. This has important implications for vaccine development.

Clinicopathological and radiographic features in 40 cats diagnosed with pulmonary and cutaneous Rhodococcus equi infection (2012-2018)

OBJECTIVES

This retrospective study aimed to describe clinical manifestations, diagnostic options, radiological features, therapeutic plans and outcomes for cats infected with Rhodococcus equi.

METHODS

Forty cats aged between 2 months and 11 years old (median 6 months) that were definitively diagnosed with rhodococcosis between 2012 and 2018 were recruited in this study. Medical records were reviewed for information on signalment, history, clinical presentation, diagnostic testing, treatment plans and clinical outcomes.

RESULTS

Of the 40 cats, 36 showed the pulmonary form of the disease, with 35 (87.5%) presenting with dyspnoea, while four cats presented with only cutaneous lesions. Mean body temperature was 38.7 ± 0.2°C. Dyspnoea was noted in 87.5% of the cats. Leukocytosis (58.3%) with band neutrophilia (83.3%), monocytosis (58.3%) and thrombocytopenia (55.5%) were prominent findings in the haematology reports. Hyperproteinaemia (61.1%) with hypoalbuminaemia (22.2%) and hyperglobulinaemia (63.8%) with a low albumin:globulin ratio (38.9%) were prominent features of blood biochemistry reports. An alveolar-interstitial pattern was noted in 75% of pre-thoracocentesis radiographs. Pleural effusion, hepatomegaly, thoracic lymphadenopathy and atelectasis of any lung lobe were seen in 88.9%, 75%, 41.7% and 36.1% of cats, respectively. Overall, the mortality rate was 67.5% in both forms.

CONCLUSIONS AND RELEVANCE

Clinicians should be aware that feline rhodococcosis manifests as a pulmonary disease at a much higher rate than previously reported. Further studies are required to address the epidemiology, pathophysiology, disease management and prognosis of feline rhodococcosis. The role of immunosuppression as a predisposing factor in feline rhodococcosis requires further investigation.

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.

Persistent Rhodococcus equi infection in a renal transplant patient: case report and review of the literature

Rhodococcus equi is a pathogen that mainly causes infection in immunocompromised hosts. We report a case of relapsing R. equi pulmonary infection in a 57-year-old male renal transplant recipient who was treated with 12 months of antibiotics, adjunctive surgery, and a reduction in his immunosuppression. He suffered from relapsing disease, treatment-related complications, and ultimately died of Pneumocystis pneumonia. Case reports in the literature portray a good cure rate for transplant-related R. equi infections, with shorter durations of antibiotics. The case illustrates the difficulties in the management of R. equi infections. Forty cases from the literature were reviewed and compared in terms of epidemiology, location of infection, transplant type, immunosuppression used, treatment used, outcomes, and possible exposures.

Rhodococcal lung abscess in a renal transplant recipient

Background:

Rhodococcus species are relatively rare human pathogens, but are being increasingly recognized as causes of infection especially in immunosuppressed patients.

Case Report:

We present a case of Rhodococcus lung abscess in a patient 10 months post-cadaveric renal transplant, successfully treated with a combination of antibiotics. She required a prolonged course of oral antibiotics for 6 months. She did not require surgical intervention. Chest X-rays and CT thorax showed complete resolution of the initial lesion. We also review the medical literature related to Rhodococcus infection in patients with renal transplantation. Rhodococcus infection should be considered as in the differential diagnosis of immunosuppressed patients who present with lung abscess/mass.

Conclusions:

A literature review indicates this is a potentially fatal condition with disseminated sepsis/abscesses.

Rifampin combination therapy for nonmycobacterial infections

The increasing emergence of antimicrobial-resistant organisms, especially methicillin-resistant Staphylococcus aureus (MRSA), has resulted in the increased use of rifampin combination therapy. The data supporting rifampin combination therapy in nonmycobacterial infections are limited by a lack of significantly controlled clinical studies. Therefore, its current use is based upon in vitro or in vivo data or retrospective case series, all with major limitations. A prominent observation from this review is that rifampin combination therapy appears to have improved treatment outcomes in cases in which there is a low organism burden, such as biofilm infections, but is less effective when effective surgery to obtain source control is not performed. The clinical data support rifampin combination therapy for the treatment of prosthetic joint infections due to methicillin-sensitive S. aureus (MSSA) after extensive debridement and for the treatment of prosthetic heart valve infections due to coagulase-negative staphylococci. Importantly, rifampin-vancomycin combination therapy has not shown any benefit over vancomycin monotherapy against MRSA infections either clinically or experimentally. Rifampin combination therapy with daptomycin, fusidic acid, and linezolid needs further exploration for these severe MRSA infections. Lastly, an assessment of the risk-benefits is needed before the addition of rifampin to other antimicrobials is considered to avoid drug interactions or other drug toxicities.

Rhodococcus equi lung infection in an allogeneic hematopoietic stem cell transplant recipient

In this report, we describe a case of Rhodococcus equi lung infection diagnosed in an allogeneic hematopoietic stem cell transplant with oral graft-versus-host disease 3 months after stem cell infusion. The lung lesion persisted despite an approximate 3 months of vancomycin therapy, but then responded favorably to a combination of intravenous ertapenem at 1 g daily and oral rifampin at 600 mg daily for 1 month. An overview of Rhodococcus infection in transplant recipients is presented. This case and the discussed literature suggest that combination antibiotic therapy is warranted in patients with decreased humoral and cellular immunity.

Rhodococcus equi pneumonia in a renal transplant patient: a case report and review of literature

Immunocompromised patients are susceptible to many pathogens, including those that are predominantly problems in veterinary medicine. We report a case of a 42-yr-old white male who presented 19 months post-cadaveric renal transplant (for IgA nephropathy) with a 5 d history of nausea, vomiting, abdominal cramping and diarrhea. Admission chest X-ray revealed a suspicious mass lesion in the left lower lobe. Computed tomography (CT) guided biopsy of the lesion showed a large zone of CD68 +ve histiocytes in a non-caseating granuloma. Gram stain revealed multiple gram-positive rods within the histiocytes, which were eventually identified as R. equi. After 4 months of therapy with fluoroquinolones (Avelox) and Azithromycin a repeat CT showed complete resolution of the lesion. We reviewed the literature with special focus on the clinical features, challenges in diagnosis, and treatment of this rare infection (especially in the transplant patients who are also on immunosuppressive therapy).

[Laryngeal infection by Rhodococcus equi in patient with AIDS]

The Rhodococcus equi is an aerobic gram positive pleomorphic bacillus, that was isolated for the first time like a producer of bronchopneumonia in young horses. Every time more often, it is being recognized as a pathogen in humans, mainly in the immunodepressed population. We described a case, until now exceptional, of laryngeal infection by Rhodococcus equi in a patient with positive serology for the virus of the human immunodeficiency (HIV), and we reviewed some clinical and epidemiological characteristics of the infections by this germ. The treatment is riphampicine and/or erythromycin, being the prognosis bad, because usually they are immunodepressed patients.