Utilização de antimicrobianos, Clorexidina e Mercúrio e resistência de Escherichia coli, Staphylococcus aureus, Streptococcus mutans e Lactobacillus spp, isolados da cavidade bucal

Abstract

The objective of this investigation was to conduct a case-control study of the impact of the use of antimicrobials, chlorhexidine and mercury, on the resistance of microorganisms of medical and dental interest (Escherichia coli, Staphylococcus aureus, Streptococcus mutans and Lactobacillus spp.) Present in the oral cavity. Four groups were tested, with ten volunteers each, namely: A- with multiple amalgam restorations, B- using antimicrobials, C- using 0.12% chlorhexidine digluconate in daily mouthwash and D- with no history of dental caries (control). Microbiological monitoring was carried out for four weeks. Resistance was determined, in vitro, by gel diffusion techniques for antimicrobials and dilution in agar, for antimicrobials, chlorhexidine digluconate and mercury chloride. The resistance transfer experiments were carried out by broth culture and membrane filtration techniques, using E. coli Kl 2 as receiving. Important colonization by Enterobacteriaceae was detected in the group using antimicrobials (50%) and control (40%). The most frequent species among the isolates was E. coli, particularly in group B (6/11) where one third of these microorganisms were multidrug-resistant. In this group, the CIMS for gentamicin were 64 mg / L versus 4 mg / L in the control group. The strains of these microorganisms were resistant to chlorhexidine and mercury chloride, regardless of group. Colonization by Staphylococcus aureus in group B was 50%, while that in group D was 30%, with an increase in colonization due to the time of use of antimicrobials. In group B, the isolates of this microorganism, as well as those of Staphylococcus spp., Were resistant to oxacillin (CIMS 90> 512 mg / L). These microorganisms, regardless of the group, were susceptible to chlorhexidine and resistant to mercury chloride, but with CIMS in relation to mercury, three times higher for those in the groups with restorations or using antimicrobials.In the group of volunteers regularly using chlorhexidine, Streptococcus mutans was the most affected microorganism. Simultaneous resistance to various antimicrobials, particularly ampicillin, was more common in group B (8/10) with an MIC90> 512 mg / L. The isolates of this species were susceptible to chlorhexidine and mercury, with the exception of two strains of group B. Strains of Lactobacillus spp. studied were susceptible to penicillin-G, chlorhexidine and mercury. The minimum inhibitory concentrations calculated by the E test for gentamicin (Enterobacteriaceae) oxacillin (staphylococci) ampicillin {Streptococcus mutans} and penicillin-G {Lactobacillus spp.) Were in agreement with the classical technique, except for an MRSA isolate that was susceptible to this technique. The conjugation experiments with the Enterobacteriaceae lactose positive isolates were successful in seven of the eight performed, however, with only two transconjugants, revealing the two resistance marks.