Rhodococcus equi isolation from sputum of patients with suspected tuberculosis

Abstract

Rhodococcus equi has emerged as an opportunistic pathogen associated with pulmonary, invasive or systemic infections in immunocompromised patients. We report the identification of 51 R. equi isolates found in sputum samples of 546 individuals suspected to have pulmonary tuberculosis in two Public Health Hospital Units in Brazil.The epidemiology of R. equi infection as well as the phenotypic identification and drug susceptibility profile of isolates are described in this paper.Key words: Rhodococcus equi -identification -tuberculosis -antimicrobial profile -epidemiologyThe genus Rhodococcus belongs to the group of nocardioform, Gram-positive rods containing mycolic acids in the cell wall; this group also includes the genera My� cobacterium, Nocardia, Corynebacterium, Dietzia, Gor� donia, Millisia, Segniliparus, Skermania, Tsukamurella and Williamsia (Soddell et al. 2006a, b, Tsitko et al. 2006). The genus Rhodococcus was discovered by Zopf in 1891 (Goodfellow & Alderson 1977) and comprises 30 species, of which Rhodococcus equi is considered the most opportunistic pathogen in mammals, including humans (Meijer & Prescott 2004). The first case of human infection was reported in 1967 in a patient presenting with a pulmonary abscess. The two first cases that occurred in Brazil were reported by Severo et al. (2001). However, with the AIDS epidemic, the number of patients infected by R. equi has grown (Roda et al. 2009). R. equi also causes infection in patients with lymphoma, chronic renal failure, alcoholism, lung cancer, leukaemia, diabetes mellitus and other immunodeficient syndromes. Some cases have been reported in which the infection can also occur in immunocompetent hosts (von Bargen & Haas 2009).When incubated aerobically at 37°C, R. equi grows efficiently in the majority of nonselective culture media, including media used in mycobacteria isolation and produces irregular, smooth and mucoid colonies that turn a shade of salmon pink to yellow after a week of growth (Prescott 1991). R. equi appears coccoid on stained smears of clinical specimens, especially purulent material and tissue (obtained by biopsy, during surgery and upon autopsy). However, long rods have been reported in clinical specimens isolated from blood, sputum and bronchial lavage fluid In general, R. equi is biochemically non-reactive, has no proteolytic activity and fails to oxidize or ferment carbohydrates, with the exception of glucose, which is oxidized by R. equi in 14 days. R. equi is strictly aerobic, catalase positive, oxidase negative and mostly urease positive. R. equi produces soluble "equi factors" that are associated with phospholipase and cholesterol oxidase activity and interact with phospholipase D of Listeria ivanovii to induce complete haemolysis of sheep erythrocytes (Prescott 1991).The Laboratory of Mycobacteriology at the Adolfo Lutz Institute in Ribeirão Preto (SP, Brazil) has frequently isolated partial acid-fast bacteria from sputum of patients suspected to have pulmonary tuberculosis. Considering the emerging clinical im...

Identification of Virulence-Associated Plasmids in Rhodococcus equi in Humans with and without Acquired Immunodeficiency Syndrome in Brazil

“…1 In the present study, six patients were men 30-50 years of age. This finding is consistent with results of other studies, which have also identified similar frequencies of rhodococcosis in men 30-50 years of age, 5,14 indicating an occupational risk of human infection by R. equi , particularly to immunocompromised patients exposed to livestock or farm environments. 1,11 The clinical manifestation of R. equi in humans is diverse, although pulmonary infections are present in approximately 80% of cases.…”

“…13 Despite implementation of control strategies and treatment protocols against HIV/AIDS in Brazil, deaths of HIV-positive patients co-infected with R. equi have been observed. 14 However, little information is available in Brazil about virulence plasmid profiles of R. equi isolates from humans. [15][16][17] Intermediately virulent strains of R. equi are predominantly identified in HIV-positive patients, 2 the lymph nodes of pigs with and without lymphadenitis, 7,12 and, more recently, in lymph nodes of wild boars ( Sus scrofa ) in Hungary 10 and Brazil.…”

Molecular Detection of vapA and vapB Genes in Rhodococcus equi Isolated from Human and Horses by Multiplex PCR in Baghdad

“…Exposure to domestic animals or their environment, such as horses and pigs, may play important role in several cases of infection. In Brazil, Silva et al (2010) reported that the resemblance of the clinical course between Rhodococcosis and tuberculosis in patient makes it difficult to detect and treat R. equi infection. A patient infected with R. equi may be treated with unsuitable initial antibiotic due to misdiagnosis with Mycobacterium species, Nocaredias species and diphtheriods.…”

“…It is an opportunistic bacterium, causing rhodococcosis, a zoonotic problem that can be confused with tuberculosis (Silva et al, 2010). Besides human and horses, infections with this pathogen has been detected in a number of animal species like cattle, pigs, deer, dogs, goats, cats, sheep, and wild animals (Prescott, 1991;Sakai et al, 2012;Cohen et al, 2014).…”

Pesquisas em pneumologia recentemente publicadas em revistas brasileiras

“…In a study conducted in Brazil by da Silva et al, (30) 51 Rhodococcus equi isolates were identified in the sputum samples of 546 individuals suspected of having pulmonary tuberculosis. The authors described the epidemiology of the infection, as well as the phenotypic characteristics and drug susceptibility profile of the isolates.…”