BACTERIAL BIOFILM FORMATION ON BIOMATERIAL ABIOTIC SURFACES

AC37

Elisabeth Loshchagin Pizzolitto (1, 2) e-mail: pizzolel@fcfar.unesp.br, Bruna Arruda Leite (1), Cássio Antônio Lanfredi dos Santos (1), Gabriela de Souza Bettio (1), Flávio Ferraz de Campos Júnior (1), Milena Mioralli (1), Ana Cristina Basso (1), Antonio Carlos Pizzolitto (2).

(1)     Programa de Pós-Graduação Interunidades Bioengenharia –EESC/FMRP/IQSC- USP, (SP), Brasil.(2)     Universidade Estadual Paulista-UNESP, Faculdade de Ciências Farmacêuticas, campus de Araraquara-UNESP.

The surfaces that allow biofilm formation can range from abiotic surfaces to biotic surfaces. Bacterial biofilms are formed from individual planktonic cells in a complex developmental process and can survives on abiotic surfaces in hospital environments and colonizes different medical devices. The objective of this research was to assess the capacity of staphylococcal survival on abiotic surfaces. Polymethylmetacrylate (PMMA) discs and 1-centimeter-long segments of siliconized latex and polyurethane catheters were cut and served as the biomaterial substratum in this study. Each biomaterial sample was tested against each of the bacterial isolates Staphylococcus aureus ATCC 25923 and Staphylococcus epidermidis ATCC 12228 in duplicate. Samples were separately and aseptically introduced in a test tube containing 5ml of Brain Heart Infusion (BHI) broth inoculated with staphylococcal suspension of 10⁸ CFU/mL each one. The samples were incubated under aerobic conditions for 24 and 48 hours at 37ºC. Afterward the coupons were removed and maintained in a dry test tube under sterile conditions for 7 days at room temperature. Then, three dry coupons were inserted, one by one, into separated tubes containing BHI broth (5mL) and incubated for 24 and 48 hours at 37ºC. Also, tubes containing three of the samples in 1.0mL of phosphate buffer saline were sonicated for 8 minutes in a water bath sonicator to dislodge adherent bacteria. The number of viable staphylococci cells were assessed by quantitative culture of serial 10-fold dilutions of the sonicate. The sonicated coupons were cultured in BHI for 24 h at 37ºC. SEM was used to observe bacterial adherence on abiotic surfaces. The staphylococcal growth was evaluated at 24 and 48h observing the turbidity of BHI broth. The results shown that before and after the 7 day sterile preservation of the tested biomaterials, the BHI broths containing samples of each materials were visually cloudy before and after 7 day sterile preservation and subsequent incubation. The number of bacteria surviving on the three abiotic surfaces was below the level of inoculation of the assay. The average cfu count for S.aureus after 24 h was about 28.3x10² and after 48 h was 6.6x10², and for S. epidermidis after 24 h was about 109.6x10² after 48 h was 7.0x10². SEM shown that abiotic surfaces allowed bacterial adherence. In conclusion bacteria were able to colonize and proliferate on these abiotic surfaces, then, these results suggest that the abiotic surfaces studied are not resistant to biofilm formation.