Biological and Synthetic Surfactants Increase Class I Integron Prevalence in Ex Situ Biofilms.

The role of biocides in the spread of antimicrobial resistance (AMR) has been addressed but only a few studies focus on the impact of surfactants on microbial diversity and AMR, although they are common constituents of cleaners, disinfectants, and personal care products and are thus released into the environment in large quantities. In this study, we used a static ex situ biofilm model to examine the development of four biofilms exposed to surfactants and analyzed the biofilms for their prevalence of class I integrons as a proxy for the overall abundance of AMR in a sample. We furthermore determined the shift in bacterial community composition by high-resolution melt analysis and 16S ribosomal RNA (16S rRNA) gene sequencing. Depending on the initial intrinsic prevalence of class I integrons in the respective ex situ biofilm, benzalkonium chloride, alkylbenzene sulfonate, and cocamidopropyl betaine increased its prevalence by up to 6.5× on average. For fatty alcohol ethoxylate and the biosurfactants sophorolipid and rhamnolipid, the mean increase did not exceed 2.5-fold. Across all surfactants, the increase in class I integrons was accompanied by a shift in bacterial community composition. Especially benzalkonium chloride, cocamidopropyl betaine, and alkylbenzene sulfonate changed the communities, while fatty alcohol ethoxylate, sophorolipid, and rhamnolipid had a lower effect on the bacterial biofilm composition.

A loophole in soap dispensers mediates contamination with Gram-negative bacteria.

Liquid soap dispensers are widely used in domestic and clinical settings. In previous studies, the risk of bacterial contamination of refillable systems was pointed out and a bacterial contamination rate of 25%, with values of up to 108 colony-forming units/mL (CFU/mL), was reported. However, the route of contamination remains elusive. To address this point, we determined the microbial contamination of refillable standard pump dispensers and nonrefillable press-dispenser systems. Following the collection of 104 liquid soap dispensers from hotel rooms across Germany, bacterial counts were determined. Isolates of samples containing nonfastidious Gram-negative(lac-) bacteria were further analyzed by the Vitek 2 system for the determination of species. 70.2% of the refillable pump dispensers (mean total bacterial count = 2.2 × 105 CFU/mL) but only 10.6% of the nonrefillable press dispensers, were contaminated (mean total bacterial count = 1.5 × 101 CFU/mL). Of samples containing nonfastidious Gram-negative(lac-) bacteria, Pluralibacter gergoviae was present in 41.7%, Pseudomonads (Pseudomonas aeruginosa and Pseudomonas putida) in 25%, Serratia marcescens in 16.7%, and Klebsiella oxytoca and Pasteurella testudinis in 8.3%. After the initial assessment, we contaminated different dispensing systems with P. aeruginosa/P. gergoviae, to reveal the route of contamination and identied the pressure release of standard pump dispensers as the loophole for microbial contamination.

High resolution ITS amplicon melting analysis as a tool to analyse microbial communities of household biofilms in ex-situ models.

Biofilms are the most common growth types of microorganisms. These complex communities usually consist of different species and are embedded in an extracellular matrix containing polymers, proteins and DNA. This matrix offers protection against different (a)biotic environmental factors and generally increases resistances. Higher resistances against antibiotics are one of the main reasons why biofilms are often associated with healthcare settings. Nevertheless, they are also found in domestic settings, mostly in humid places with abundant nutrients like dishwashers or washing machines. Biofilms in these areas show individual compositions and are influenced for example by temperature, frequency of use or the age of the device. In this study, we introduce a model for the ex-situ cultivation of domestic biofilms from household appliances. Furthermore, we tested the ability of high resolution melting analysis (HRMA) as a tool for analysing these biofilms. Our goal was to maintain a high amount of complexity in the ex-situ biofilms that is characterized by the melting behavior of the contained DNA. Dishwasher and washing machine biofilms were sampled in private households and cultivated for 10 d. After DNA extraction, 16S rDNA was sequenced and melting behavior of the bacterial Internal Transcribed Spacer (ITS) region was analysed. Additionally, testing for independence of continuous new sampling, storage of cultivated biofilms in glycerol stocks and following recultivation of them was done up to three times. Our results show that a high level of complexity could be maintained in the ex-situ biofilms after 10 d of cultivation, although in general the bacterial diversity slightly decreased compared to the original biofilm in most cases. Recultivation of a similar biofilm from glycerol stocks was possible as well with some impact by various factors. Differences in the bacterial composition of biofilms could clearly made visible by HRMA although it was not possible to match peaks to a specific phylogenetic group. Still, HRMA proved to be a less costly and time consuming alternative to sequencing for the characterization of biofilms.