Assessment of resistance towards biocides following the attachment of micro-organisms to, and growth on, surfaces

Abstract

Aims: To develop a rapid method for the assessment of biocidal activity directed towards intact bio®lms. Methods and Results: Escherichia coli and Staphylococcus epidermidis were cultured for up to 48 h within 96-well microtitre plates. The planktonic phase was removed and the wells rinsed. Residual bio®lms were exposed to various concentrations of chloroxylenol, peracetic acid, polyhexamethylene biguanide (PHMB), cetrimide or phenoxyethanol for 1 h. At 15-min intervals, biocide was removed, and the wells washed in neutraliser and ®lled with volumes of fresh medium. Re-growth of the cultures was monitored during incubation at 35°C in the plate reader. Times taken for the treated wells to re-grow to ®xed endpoints were determined and related to numbers of surviving cells. Time±survival curves were constructed and the survival of the attached bacteria, following exposure to the agents for 30 min, interpolated for each biocide concentration. Log±log plots of these survival data and biocide concentration were constructed, and linear regression analysis performed in order to (i) calculate concentration exponents and (ii) compare the effectiveness of the biocides between variously aged bio®lm and planktonic cells. From such analyses iso-effective concentrations of biocide (95% kill in 30 min) were calculated and expressed as planktonic : bio®lm indices (PBI). Conclusions: PBI varied between 1á02 and 0á02, were relatively unaffected by age of the bio®lms but differed signi®cantly between organism and biocide. Notably those compounds with the higher activity against planktonic bacteria (PHMB and peracetic acid) were most prone to a bio®lm effect but remained the most effective of the agents selected. Signi®cance and Impact of the Study: The endpoint method proved robust, enabled the bactericidal effects of the biocides to be assessed against in-situ bio®lms, and was suitable for routine screening applications.

Exposure of Sink Drain Microcosms to Triclosan: Population Dynamics and Antimicrobial Susceptibility

“…Exposure of drain microcosms to use levels of TCSD (0.2 to 0.4%) did not significantly lower total counts of drain biofilm bacteria for a number of possible reasons. Biofilms are considerably less susceptible to antimicrobials than are planktonic cells (2,16,17,50), suggesting that lack of significant lethality could be simply due to the insusceptible biofilm phenotype. In addition, many of the bacteria isolated from the baseline drain microcosm were innately tolerant to TCS and could grow in saturated solutions of the biocide or on saturated TCS agar plates.…”

Comparative Proteomic Analysis of Streptococcus suis Biofi lms and Planktonic Cells That Identifi ed Biofi lm Infection-Related Immunogenic Proteins

“…�hen bio�lms are identi�ed as the main cause of infection, treatment becomes very difficult since bacteria within bio�lms adopt special features that confer them increased resistance to antimicrobial agents [9]. is resistance usually makes sessile microorganism more difficult to kill and remove from surfaces than planktonic counterparts.…”

“…Bio�lms represent a reservoir of pathogenic bacteria that can detach, resume their planktonic state, and contaminate new surfaces and patients. Moreover, microbial bio�lms are notorious for their high level of resistance towards antibiotic and biocide treatments [9]. Bacteria within bio�lms can easily live in the presence of high antibiotic concentrations similar to the ones that are prescribed during the course of therapies [10,11].…”

Endodontologie in beweging: nieuwe concepten, materialen en technieken 4. Wortelkanaaldesinfectie anno 2015

“…De slijmlaag vormt een fysieke bescherming tegen antimicrobiële middelen. Bovendien zijn biofi lmbacteriën metabool afwijkend, waardoor ze minder gevoelig kunnen zijn voor desinfectie (Gilbert et al, 2001). …”