Rhodococcus equi: AN APPROACH TO THE METHODOLOGY OF PRESUMPTIVE IDENTIFICATION AND TESTS OF SENSITIVITY TO ANTIMICROBIALS

• DOI: 10.22533/at.ed.1593722311096

• Palavras-chave: Rhodococcus equi, presumptive identification, “camp factor” Cholesterol Oxidase, antimicrobials, Disk Diffusion, CIM.

• Keywords: Rhodococcus equi, presumptive identification, “camp factor” Cholesterol Oxidase, antimicrobials, Disk Diffusion, CIM.

• Abstract:

  Rhodococcus equi is a Gram-positive bacterial agent and contains mycolic acids in the cell wall, being classified in the group of aerobic actinomycetes. The relevance of R. equi is remarkable for veterinary and human medicine, as it is considered a zoonotic agent that causes rhodococcosis in animals and humans, with pulmonary infection being the most common. R. equi is considered a pathogenic agent in foals and has emerged as an opportunist in humans, especially associated with human immunodeficiency virus infection. Pulmonary rhodococcosis has clinical and pathological characteristics similar to pulmonary tuberculosis, in immunocompromised and non-immunocompromised patients. In this review, we address a methodology that can be implemented in microbiology laboratories, especially those that carry out diagnosis, in view of the occurrence of bacterial isolates that resemble the phenotypic profiles of R. equi, valuing the importance of its isolation and identification, even if presumptively. The study was based on the review of scientific articles, case reports, monographs, dissertations and theses, published in magazines, periodicals, books and materials available online. The presumptive identification of R. equi is carried out based on a variety of phenotypic characteristics, initially considering the colonial and cellular morphology, partial resistance to acid alcohol and the production of the factor equi demonstrated in the CAMP Test. The treatment of rhodococcosis is still quite incipient and in Brazil there are few works carried out to evaluate the sensitivity profile to the current antimicrobials for this bacterial agent. The standard test recommended by the “Clinical and Laboratory Standards Institute/National Committee for Clinical Laboratory Standards” for aerobic actinomycetes, including Rhodococcus sp, is the determination of the Minimum Inhibitory Concentration (MIC), which can be performed using the broth microdilution method. Müeller Hinton (MH broth) supplemented with cations. There are still no standardized methods for testing the sensitivity of aerobic actinomycetes, using the Disk Diffusion method, however, in recent years, several antimicrobial agents have been tested, such as amikacin, amoxicillin-clavulanate, ceftriaxone, ciprofloxacin, erythromycin, imipenem, minocycline and sulfamethoxazole- trimethoprim. Several researchers have followed the interpretation criteria of accepted cutoff points for Staphylococcus sp. Due to the occurrence of human rhodococcosis with the increase in the number of cases of infections by R. equi, there is a need to use more appropriate identification techniques, as well as more clinical studies to delineate a conclusion of diagnosis and treatment schemes. Presumptive identification is often enough to initiate empirical treatment with antimicrobial agents.