NTU Undergraduates' research April 2014 - Biosciences | Page 100

The relationship between biofilm production and disinfectant
resistance in Acinetobacter baumannii
Charlotte.F Marshalla
a

Nottingham Trent University

Background: Acinetobacter baumannii is a gram negative pathogen which previously was described as a
ubiquitous microorganism, as it can produce biofilms .This allows survival in harsh conditions in hospitals such
as; desiccation, nutrient starvation and antibiotic treatment which has allowed Acinetobacter baumannii to
emerge as a human pathogen. This organism is so problematic in the healthcare setting, as it can colonise
medical devices and cause high mortality rates in immuno-compromised patients. Previous publications have
focused more on the fact that Acinetobacter baumannii can show resistance to antibiotics, which is why more
research is needed into disinfectants, as this may show which concentrations are more effective in reducing
biofilms and when resistance may be shown. Biofilms are problematic as they can form on any surface,
therefore it is important to determine how disinfectants react when treating a biofilm compared to when they
treat surfaces before the biofilms can form to show how effective disinfectants are. This would highlight how
difficult it is to remove biofilms formed by this bacterium when specific disinfectants are used at certain
concentrations. Previous publications have shown the biofilm can show resistance to Chlorhexidine disinfectant
however other publications focus more on planktonic cells compared to biofilms. For the disinfectants tested,
even though all four disinfectants are used routinely in hospitals there is only data published on how
Chlorhexidine can affect biofilms.
Objectives: The main objective was to determine whether biofilms provide Acinetobacter with resistance
against disinfectants compared to when present as planktonic cells. This was using MIC values. This experiment
hoped to determine the difference in biofilm levels affected by pre-treatment or post treatment with different
disinfectants. Chlorhexidine gluconate, Trigene advance, Hycolin and Biocleanse were the disinfectants tested.
Viable counts were used to determine survival of biofilm cells compared to planktonic when applied with
disinfectant Methods: Pre and post treatment of plastic wear with disinfectants were applied to six strains of
Acinetobacter baumannii, 1121,1125,1127,1265,1339 and 1340. Biofilm levels were measured using the total
protein content at 600nm. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations
were determined when these strains were present as planktonic and as biofilms to show whether resistance
was displayed based on the differences in the MIC values in particular. Using data acquired from this, viable
counts were carried out to show how differences in biofilm levels may be a factor in resistance to disinfectants.
Cells of both planktonic and biofilm (both intact and clumped) were incubated for 2 hours total.
Results and conclusions: Resistance was shown only with the wild type strain 1265 biofilm towards
Chlorhexidine. Pre-treatment and post treatment showed different effects on the biofilm levels with different
disinfectants. For Chlorhexidine and hycolin, viable counts showed planktonic cells were susceptible. When the
biofilm was disrupted this was more susceptible to the disinfectants than when intact. However, after two
hours colonies were still present in biofilm cells showing that biofilms can be treated with disinfectants to
reduce the number of colonies, however the protective layer of the biofilm prevents complete elimination of
colonies in contrast to planktonic cells which do not have this protective layer. There is incomplete data to
assume whether difference biofilm levels play a role in disinfectant resistance.