1º Autor: Alcina Mateus
Serviço de Patologia Clínica, Unidade Local de Saúde de Coimbra
Coautores: João A. Pinto; Graça Pombo; Maria José Montanha – Serviço de Patologia Clínica, ULS do Nordeste
Resumo
Introduction: Ochrobactrum spp. are considered opportunistic pathogens of low virulence in humans. The genus Ochrobactrum includes Gram-negative, rod-shaped, obligate-aerobic, catalase-positive, and oxidase-positive microorganisms. These nonfastidious bacteria grow readily on most conventional culture media.
Ochrobactrum anthropic and O. intermedium can be isolated from several environmental sources. The first one, is recognized as a clinical pathogen that can lead to a variety of opportunistic infections including prosthetic valve endocarditis, catheter-related bloodstream infections and other medical device-associated nosocomial infections.
These microorganisms rarely cause infections in immunocompetent hosts. The severity of the infection depends on the host’s vulnerability and the microorganism’s ability to adhere to plastic devices. Due to the presence of AmpC beta-lactamases, they are usually resistant to most β-lactam antibiotics excluding carbapenems. Drugs like aminoglycosides, fluoroquinolones, tetracycline and trimethoprim–sulfamethoxazole are usually active against Ochrobactrum spp.
Case Report
A 64-year-old male patient was admitted to the emergency service with erysipelas and was discharged with a prescription of Amoxicillin + Clavulanic Acid. Six weeks later, he was readmitted to the emergency service with bradycardia, nausea and dizziness. Cardiac examination revealed complete atrioventricular block and an image suggested vegetation on the ventricular face of the aortic prosthetic valve, leading to a diagnosis of a possible endocarditis. The patient presented a history of drug abuse, HIV-1 under treatment and treated HCV. After clinical stabilisation during hospitalisation, prosthetic valve replacement was proposed, and the patient was transferred to a specialised unit. The surgery was performed without any complications. A biopsy was sent for microbiological study.
Discussion (Materials and Methods): In the laboratory, the biopsy collected during the prosthetic valve removal surgery, was cultivated in Brain Heart Infusion (BHI) at 37°C in a controlled atmosphere for nearly 5 days. Following this incubation period, a Gram-stained smear was prepared from the resulting microbial growth, showing Gram-negative bacilli. Two cultures were also performed, Columbia Agar + 5% Sheep Blood (GS) and PolyVitex Chocolate Agar (PVX) media. After incubation for 24 hours at 37°C in a controlled atmosphere, microbial growth was observed on the plates. The isolated microorganism was Ochrobactrum spp. using Matrix-Assisted Laser Desorption/Ionisation Time-of-Flight (MALDI-TOF), a rapid and accurate laboratory identification technique.
Conclusion: The number of studies available on antimicrobial drug susceptibility is low, due to the rare occurrence of Ochrobactrum spp. as an infectious agent. Therefore, the emergence of infections caused by less common agents represents a challenge for microbiology laboratories. The difficulty in obtaining adjusted and optimised susceptibility profiles can lead to the implementation of empirical and excessive antibiotherapy against highly sensitive agents, which, in the long term, contributes to the emergence of resistant variants.