Changes in the biocide susceptibility of Staphylococcus epidermidis and Escherichia coli cells associated with rapid attachment to plastic surfaces

Abstract

GI LB E RT . 1998. Differences in opacity between wells of a microtitre plate containing different volumes of inoculated growth medium reflected planktonic growth without any contribution from cells attached at the well surface. Simple algebra and a knowledge of the dependence of optical density upon sample path length (volume) for suspensions of differing cell density enables the generation of growth curves for attached populations (biofilms). In this manner, minimum inhibitory concentrations (MICs) were determined at various stages of growth (0-20 h), both for cells growing attached to the bases of the plate wells and, simultaneously, for cells growing in suspension above them. Biocides included cetrimide, polyhexamethylene biguanide, peracetic acid, phenoxyethanol and chloroxylenol. Results, expressed as planktonic:biofilm MIC ratios, showed susceptibility to change, not only as a function of attachment and biofilm formation, but also with respect to the nature of the chemical agent. In some instances, changes in susceptibility greater than twofold occurred immediately on attachment and could occur in the presence of biocide concentrations which exceeded the MIC.

The Limitations of In Vitro Experimentation in Understanding Biofilms and Chronic Infection

“…This system has been heavily used to identify potential anti-biofilm agents, by measuring the reduction in surface attached biomass on the sides of wells after treatment with potential therapeutic agents [51][52][53][54]. In addition to this, The Center for Disease Control (CDC) approved biofilm reactor [55][56][57], and drip flow reactors, have proved excellent for assessing biofilm formation on biological and non-biological materials [58][59][60].…”

Antimicrobial Activity of Polyhexamethylene Guanidine Derivatives Introduced into Polycaprolactone

“…Research by Zhou et al [12] indicates that low PHMG concentrations only damaged the external structures of bacterial cell membrane. Das et al [13] determined the ability of E. coli and S. aureus to form biofilm on polymers with incorporated polyhexamethylene biguanide in the presence of acetic acid. Their research demonstrated that PHMG inhibits biofilm formation and reduces bacterial cells adhesion to polymer surfaces, which is beneficial in packaging and medical industries.…”

Effect of glutaraldehyde biocide on laboratory-scale rotating biological contactors and biocide efficacy

“…In planktonic cells biooxidation was totally inhibited in the presence of 25 ppm glutaraldehyde while biofilms retained some of their bio-oxidation capacity in the presence of glutaraldehyde up to 180 ppm. This may be attributed to the effect of exopolysaccharide polymers produced as a potential barrier which can prevent biocides from reaching the target organisms within the biofilms (Das et al 1998;Morton et al 1998;Stewart et al1998). It can be assumed that in the presence of biocide planktonic bacteria play no part in the substrate removal and only bio-oxidation by the biofilms takes place.…”

“…Biofilm formation causes reductions in efficiency in industrial machinery, heat exchangers, vessels and filters (Melo and Bott, 1997;Bott, 1998;Das et al 1998) and may cause acceleration of metallic corrosion (Cloete et al 1998). Numerous methods have been used for minimizing adverse effects of biofilm formation.…”