Dados do Trabalho

Título

Biofilm formation and antimicrobial resistance of Rhodococcus equi, identified by mass spectrometry, isolated from human patients with pulmonary signs of suspected tuberculosis: Preliminary data

Introdução

Rhodococcus equi are oportunistic soilborne bacteria of livestock. Human infections occur by the inhalation of aerosols in contaminated environments (horses) and the ingestion of meat (cattle and pigs). Pneumonia, which resembles tuberculosis, represents the most common clinical sign of human rhodococcosis. Recently, an increase in multidrug-resistant R. equi strains of human and animal origin has been observed. Since foals are treated for rhodococcosis, humans could be infected by resistant R. equi from horses. Moreover, biofilms are complex communities of aggregated bacteria that impair antimicrobial activity.

Objetivo (s)

Considering this scenario, in vitro susceptibility/resistance and biofilm formation were investigated in 20 R. equi strains isolated from human patients with signs of pneumonia, and suspected of having tuberculosis.

Material e Métodos

The isolates were identified using mass spectrometry (MALDI-TOF MS). A microtiter method using 96-well plates was used to evaluate the biofilm yield. In vitro susceptibility testing (disk diffusion method) was performed using 19 antimicrobials from 10 classes: 1) used exclusively for humans (tigecycline, vancomycin); 2) used for both humans and animals (amikacin, amoxicillin/clavulanic acid, azithromycin, ceftriaxone, ciprofloxacin, clarithromycin, erythromycin, gentamicin, imipenem, levofloxacin, penicillin, rifampicin, sulfamethoxazole/trimethoprim); and 3) used only in animals (enrofloxacin, ceftiofur, florfenicol, marbofloxacin). This study was approved by the Scientific Committee of IAL-RP (52-P/2023) and FMVZ (protocol 123/2015). Low biofilm-formation were observed in all isolates. All R. equi were susceptible to amikacin, amoxicillin/clavulanic acid, clarithromycin, imipenem, levofloxacin, marbofloxacin, rifampicin, tigecycline, and vancomycin. In turn, R. equi was resistant mainly to penicillin (60%) and sulfamethoxazole/trimethoprim (35%), and multidrug resistance was identified in 25% strains. Resistance of R. equi to drugs used exclusively for animals included florfenicol (25%), ceftiofur (10%), and enrofloxacin (5%).

Resultados e Conclusão

Overall, biofilm-formation was observed in all R. equi strains, and multidrug resistance in 25% isolates, reinforcing that therapy should be instituted based on previous in vitro susceptibility tests. The isolation of R. equi from humans, resistant to antimicrobials used only in animals, is a circumstantial evidence that humans could be infected by isolates from animal origin. CNPq: 310345/2020-0

Palavras Chave

human rhodococcosis; pulmonary infection; multidrug-resistance; MALDI-TOF MS; One Health approaches