Bacterial, fungal and yeast contamination in six brands of irreversible hydrocolloid impression materials

ABSTRACT

This study assessed the level of contamination of six commercially available irreversible hydrocolloids (two containing chlorhexidine) and identified the contamination present in the materials. Petri dishes containing selective and enriched culture media were inoculated with alginate powder (0.06 g), in triplicate. After incubation (37°C/7 days), the colony-forming units (CFU) were counted and Gram stained. Biochemical identification of the different morphotypes was also performed. The contamination levels for the materials were Jeltrate - 389 CFU/g; Jeltrate Plus - 516 CFU/g; Jeltrate Chromatic - 135 CFU/g; Hydrogum - 1,455 CFU/g; Kromopan - 840 CFU/g; and Greengel - 59 CFU/g. Gram staining revealed the presence of Gram-positive bacillus and Gram-positive cocci. The bacteria Staphylococcus epidermidis, Bacillus subtilis, Bacillus sp., Bacillus coagulans, Bacillus licheniformis, Bacillus cereus, Micrococcus luteus, and Nocardia sp.; the filamentous fungi Aspergillus niger, Aspergillus flavus, Rhizopus sp., Neurospora sp.; and the yeast Candida sp. were isolated. The contamination detected in the impression materials points out the need for adopting measures to improve the microbiological quality of these materials. The use of contaminated materials in the oral cavity goes against the basic principles for controlling cross-contamination and may represent a risk for debilitated or immunocompromised patients.

RESUMO

Este estudo avaliou o nível de contaminação de seis marcas comerciais de alginato (duas contendo clorexidina) e identificou a contaminação presente nesses materiais. Alíquotas de alginato (0,06 g) foram semeadas em meios de cultura seletivos e enriquecidos, em triplicata. Após incubação (37°C/7 dias), as unidades formadoras de colônia (UFC) foram contadas e foram realizadas as identificações morfotintorial (Gram) e bioquímica. Os níveis de contaminação dos materiais foram Jeltrate - 389 UFC/g; Jeltrate Plus - 516 UFC/g; Jeltrate Chromatic - 135 UFC/g; Hydrogum - 1.455 UFC/g; Kromopan - 840 UFC/g; e Greengel - 59 UFC/g. A coloração de Gram revelou a presença de bacilos Gram-positivos e cocos Gram-positivos. As bactérias Staphylococcus epidermidis, Bacillus subtilis, Bacillus sp., Bacillus coagulans, Bacillus licheniformis, Bacillus cereus, Micrococcus luteus e Nocardia sp.; os fungos filamentosos Aspergillus niger, Aspergillus flavus, Rhizopus sp., Neurospora sp.; e a levedura Candida sp. foram isolados. A contaminação detectada nos materiais aponta a necessidade de adoção de medidas para melhorar seu controle de qualidade microbiológica. O uso de materiais contaminados na boca contradiz os princípios básicos de controle de infecção-cruzada e pode representar um risco para pacientes debilitados ou imunocomprometidos.